srcmap_generator/

lib.rs

//! High-performance source map generator (ECMA-426).
//!
//! Builds source maps incrementally by adding mappings one at a time.
//! Outputs standard source map v3 JSON.
//!
//! # Examples
//!
//! ```rust
//! use srcmap_generator::SourceMapGenerator;
//!
//! fn main() {
//!     let mut builder = SourceMapGenerator::new(Some("bundle.js".to_string()));
//!
//!     let src = builder.add_source("src/app.ts");
//!     builder.set_source_content(src, "const x = 1;".to_string());
//!
//!     let name = builder.add_name("x");
//!     builder.add_named_mapping(0, 0, src, 0, 6, name);
//!     builder.add_mapping(1, 0, src, 1, 0);
//!
//!     let json = builder.to_json();
//!     assert!(json.contains(r#""version":3"#));
//!     assert!(json.contains(r#""sources":["src/app.ts"]"#));
//! }
//! ```

use rustc_hash::FxHashMap;
use srcmap_codec::{vlq_encode_unchecked, vlq_encode_unsigned};

use srcmap_scopes::ScopeInfo;

use std::io;

// ── Public types ───────────────────────────────────────────────────

/// Decomposed source map parts for structured access without JSON serialization.
///
/// Returned by [`SourceMapGenerator::into_parts`] and [`StreamingGenerator::into_parts`].
/// Useful when the caller needs direct access to individual fields (e.g., for NAPI
/// bindings that pass each field separately) without paying the cost of full JSON
/// serialization.
#[derive(Debug, Clone)]
pub struct SourceMapParts {
    /// The generated file name, if set.
    pub file: Option<String>,
    /// VLQ-encoded mappings string.
    pub mappings: String,
    /// List of original source file paths.
    pub sources: Vec<String>,
    /// List of identifier names referenced by mappings.
    pub names: Vec<String>,
    /// Source content for each source (parallel to `sources`).
    pub sources_content: Vec<Option<String>>,
    /// Indices into `sources` that should be ignored by debuggers.
    pub ignore_list: Vec<u32>,
    /// Debug ID (UUID) for this source map (ECMA-426).
    pub debug_id: Option<String>,
    /// Source root prefix.
    pub source_root: Option<String>,
    /// VLQ-encoded range mappings string (ECMA-426 proposal), if any.
    pub range_mappings: Option<String>,
}

/// A mapping from a generated position to an original position.
///
/// Used with [`SourceMapGenerator`] to define position relationships.
/// All positions are 0-based.
#[derive(Debug, Clone)]
pub struct Mapping {
    /// 0-based line in the generated output.
    pub generated_line: u32,
    /// 0-based column in the generated output.
    pub generated_column: u32,
    /// Source index from [`SourceMapGenerator::add_source`], or `None` for generated-only.
    pub source: Option<u32>,
    /// 0-based line in the original source.
    pub original_line: u32,
    /// 0-based column in the original source.
    pub original_column: u32,
    /// Name index from [`SourceMapGenerator::add_name`], or `None`.
    pub name: Option<u32>,
    /// Whether this mapping is a range mapping (ECMA-426 rangeMappings proposal).
    pub is_range_mapping: bool,
}

/// Builder for creating source maps incrementally.
///
/// Register sources and names first (they return indices), then add mappings
/// that reference those indices. Mappings should be added in generated-position
/// order, though the builder does not require it.
///
/// Sources and names are automatically deduplicated.
///
/// # Workflow
///
/// 1. [`add_source`](Self::add_source) — register each original file
/// 2. [`set_source_content`](Self::set_source_content) — optionally attach content
/// 3. [`add_name`](Self::add_name) — register identifier names
/// 4. [`add_mapping`](Self::add_mapping) / [`add_named_mapping`](Self::add_named_mapping) — add mappings
/// 5. [`to_json`](Self::to_json) — serialize to JSON
#[derive(Debug)]
pub struct SourceMapGenerator {
    file: Option<String>,
    source_root: Option<String>,
    sources: Vec<String>,
    sources_content: Vec<Option<String>>,
    names: Vec<String>,
    mappings: Vec<Mapping>,
    ignore_list: Vec<u32>,
    debug_id: Option<String>,
    scopes: Option<ScopeInfo>,
    assume_sorted: bool,
    // Tracks whether `mappings` is non-decreasing by (generated_line,
    // generated_column), maintained incrementally on every push so the encode
    // path can skip the O(n) `is_sorted_by_position` re-scan.
    mappings_in_order: bool,

    // Dedup maps for O(1) lookup
    source_map: FxHashMap<String, u32>,
    name_map: FxHashMap<String, u32>,
}

impl SourceMapGenerator {
    /// Create a new empty source map generator.
    pub fn new(file: Option<String>) -> Self {
        Self {
            file,
            source_root: None,
            sources: Vec::new(),
            sources_content: Vec::new(),
            names: Vec::new(),
            mappings: Vec::new(),
            ignore_list: Vec::new(),
            debug_id: None,
            scopes: None,
            assume_sorted: false,
            mappings_in_order: true,
            source_map: FxHashMap::default(),
            name_map: FxHashMap::default(),
        }
    }

    /// Create a new source map generator with pre-allocated capacity.
    ///
    /// Pre-allocates the internal mappings vector, avoiding re-allocations
    /// when the number of mappings is known upfront.
    pub fn with_capacity(file: Option<String>, mapping_capacity: usize) -> Self {
        Self {
            file,
            source_root: None,
            sources: Vec::new(),
            sources_content: Vec::new(),
            names: Vec::new(),
            mappings: Vec::with_capacity(mapping_capacity),
            ignore_list: Vec::new(),
            debug_id: None,
            scopes: None,
            assume_sorted: false,
            mappings_in_order: true,
            source_map: FxHashMap::default(),
            name_map: FxHashMap::default(),
        }
    }

    /// Set the source root prefix.
    pub fn set_source_root(&mut self, root: impl Into<String>) {
        self.source_root = Some(root.into());
    }

    /// Set the debug ID (UUID) for this source map (ECMA-426).
    pub fn set_debug_id(&mut self, id: impl Into<String>) {
        self.debug_id = Some(id.into());
    }

    /// Set scope and variable information (ECMA-426 scopes proposal).
    pub fn set_scopes(&mut self, scopes: ScopeInfo) {
        self.scopes = Some(scopes);
    }

    /// Assume mappings are already sorted by `(generated_line, generated_column)`.
    ///
    /// When set to `true`, the internal encoding path and [`to_decoded_map`](Self::to_decoded_map)
    /// skip the sort step, avoiding
    /// both the `O(n log n)` sort and the `Vec<&Mapping>` allocation.
    /// Most bundlers add mappings in order, so this is a safe optimization
    /// in the common case.
    pub fn set_assume_sorted(&mut self, sorted: bool) {
        self.assume_sorted = sorted;
    }

    /// Register a source file and return its index.
    #[inline]
    pub fn add_source(&mut self, source: &str) -> u32 {
        if let Some(&idx) = self.source_map.get(source) {
            return idx;
        }
        let idx = self.sources.len() as u32;
        self.sources.push(source.to_string());
        self.sources_content.push(None);
        self.source_map.insert(source.to_string(), idx);
        idx
    }

    /// Set the content for a source file.
    pub fn set_source_content(&mut self, source_idx: u32, content: impl Into<String>) {
        if (source_idx as usize) < self.sources_content.len() {
            self.sources_content[source_idx as usize] = Some(content.into());
        }
    }

    /// Register a name and return its index.
    #[inline]
    pub fn add_name(&mut self, name: &str) -> u32 {
        if let Some(&idx) = self.name_map.get(name) {
            return idx;
        }
        let idx = self.names.len() as u32;
        self.names.push(name.to_string());
        self.name_map.insert(name.to_string(), idx);
        idx
    }

    /// Add a source index to the ignore list.
    pub fn add_to_ignore_list(&mut self, source_idx: u32) {
        if !self.ignore_list.contains(&source_idx) {
            self.ignore_list.push(source_idx);
        }
    }

    /// Add a mapping with no source information (generated-only).
    /// Push a mapping, maintaining the incremental `mappings_in_order` flag.
    ///
    /// Single choke point for every mapping insertion: keeping the
    /// non-decreasing-position invariant updated here lets the encode path
    /// avoid an O(n) sortedness scan. Mirrors `is_sorted_by_position`'s
    /// `(generated_line, generated_column)` ordering exactly.
    #[inline]
    fn push_mapping(&mut self, mapping: Mapping) {
        if self.mappings_in_order
            && let Some(last) = self.mappings.last()
            && (mapping.generated_line, mapping.generated_column)
                < (last.generated_line, last.generated_column)
        {
            self.mappings_in_order = false;
        }
        self.mappings.push(mapping);
    }

    pub fn add_generated_mapping(&mut self, generated_line: u32, generated_column: u32) {
        self.push_mapping(Mapping {
            generated_line,
            generated_column,
            source: None,
            original_line: 0,
            original_column: 0,
            name: None,
            is_range_mapping: false,
        });
    }

    /// Add a mapping from generated position to original position.
    pub fn add_mapping(
        &mut self,
        generated_line: u32,
        generated_column: u32,
        source: u32,
        original_line: u32,
        original_column: u32,
    ) {
        self.push_mapping(Mapping {
            generated_line,
            generated_column,
            source: Some(source),
            original_line,
            original_column,
            name: None,
            is_range_mapping: false,
        });
    }

    /// Add a mapping with a name.
    pub fn add_named_mapping(
        &mut self,
        generated_line: u32,
        generated_column: u32,
        source: u32,
        original_line: u32,
        original_column: u32,
        name: u32,
    ) {
        self.push_mapping(Mapping {
            generated_line,
            generated_column,
            source: Some(source),
            original_line,
            original_column,
            name: Some(name),
            is_range_mapping: false,
        });
    }

    /// Add a range mapping from generated position to original position.
    ///
    /// A range mapping maps every position from its generated position up to
    /// (but not including) the next mapping, applying a proportional delta
    /// to the original position (ECMA-426 `rangeMappings` proposal).
    pub fn add_range_mapping(
        &mut self,
        generated_line: u32,
        generated_column: u32,
        source: u32,
        original_line: u32,
        original_column: u32,
    ) {
        self.push_mapping(Mapping {
            generated_line,
            generated_column,
            source: Some(source),
            original_line,
            original_column,
            name: None,
            is_range_mapping: true,
        });
    }

    /// Add a named range mapping.
    pub fn add_named_range_mapping(
        &mut self,
        generated_line: u32,
        generated_column: u32,
        source: u32,
        original_line: u32,
        original_column: u32,
        name: u32,
    ) {
        self.push_mapping(Mapping {
            generated_line,
            generated_column,
            source: Some(source),
            original_line,
            original_column,
            name: Some(name),
            is_range_mapping: true,
        });
    }

    /// Add a mapping only if it differs from the previous mapping on the same line.
    ///
    /// This skips redundant mappings where the source position is identical
    /// to the last mapping, which reduces output size without losing information.
    /// Used by bundlers and minifiers to avoid bloating source maps.
    pub fn maybe_add_mapping(
        &mut self,
        generated_line: u32,
        generated_column: u32,
        source: u32,
        original_line: u32,
        original_column: u32,
    ) -> bool {
        if let Some(last) = self.mappings.last()
            && last.generated_line == generated_line
            && last.source == Some(source)
            && last.original_line == original_line
            && last.original_column == original_column
        {
            return false;
        }
        self.add_mapping(generated_line, generated_column, source, original_line, original_column);
        true
    }

    /// Encode all mappings directly into the provided byte buffer.
    /// Avoids intermediate String allocation when writing to an existing buffer.
    fn encode_mappings_into(&self, out: &mut Vec<u8>) {
        if self.mappings.is_empty() {
            return;
        }

        // Fast path: skip sort when mappings are already in order (common case
        // for bundlers that emit mappings sequentially).
        if self.assume_sorted || self.mappings_in_order {
            #[cfg(feature = "parallel")]
            if self.mappings.len() >= 4096 {
                let refs: Vec<&Mapping> = self.mappings.iter().collect();
                let encoded = Self::encode_parallel_impl(&refs);
                out.extend_from_slice(encoded.as_bytes());
                return;
            }
            Self::encode_sequential_into(&self.mappings, out);
            return;
        }

        // Sort mappings by (generated_line, generated_column)
        let mut sorted: Vec<&Mapping> = self.mappings.iter().collect();
        sorted.sort_unstable_by(|a, b| {
            a.generated_line
                .cmp(&b.generated_line)
                .then(a.generated_column.cmp(&b.generated_column))
        });

        #[cfg(feature = "parallel")]
        if sorted.len() >= 4096 {
            let encoded = Self::encode_parallel_impl(&sorted);
            out.extend_from_slice(encoded.as_bytes());
            return;
        }

        Self::encode_sequential_into(&sorted, out);
    }

    /// Encode all mappings to a VLQ-encoded string.
    #[allow(dead_code, reason = "used by tests and the parallel encoding path")]
    fn encode_mappings(&self) -> String {
        if self.mappings.is_empty() {
            return String::new();
        }

        // Fast path: skip sort when mappings are already in order (common case
        // for bundlers that emit mappings sequentially).
        if self.assume_sorted || self.mappings_in_order {
            #[cfg(feature = "parallel")]
            if self.mappings.len() >= 4096 {
                let refs: Vec<&Mapping> = self.mappings.iter().collect();
                return Self::encode_parallel_impl(&refs);
            }
            return Self::encode_sequential_impl(&self.mappings);
        }

        // Sort mappings by (generated_line, generated_column)
        let mut sorted: Vec<&Mapping> = self.mappings.iter().collect();
        sorted.sort_unstable_by(|a, b| {
            a.generated_line
                .cmp(&b.generated_line)
                .then(a.generated_column.cmp(&b.generated_column))
        });

        #[cfg(feature = "parallel")]
        if sorted.len() >= 4096 {
            return Self::encode_parallel_impl(&sorted);
        }

        Self::encode_sequential_impl(&sorted)
    }

    /// Encode mappings directly into an existing byte buffer.
    ///
    /// Writes VLQ-encoded mappings into `out`. Pre-allocates capacity internally
    /// based on mapping count and max generated line.
    #[inline]
    fn encode_sequential_into<T: std::borrow::Borrow<Mapping>>(sorted: &[T], out: &mut Vec<u8>) {
        // Ensure enough capacity: 36 bytes per mapping + semicolons for line gaps
        let max_line = sorted.last().map_or(0, |m| m.borrow().generated_line as usize);
        out.reserve(sorted.len() * 36 + max_line + 1);

        let mut prev_gen_col: i64 = 0;
        let mut prev_source: i64 = 0;
        let mut prev_orig_line: i64 = 0;
        let mut prev_orig_col: i64 = 0;
        let mut prev_name: i64 = 0;
        let mut prev_gen_line: u32 = 0;
        let mut first_in_line = true;

        for item in sorted {
            let m = item.borrow();
            while prev_gen_line < m.generated_line {
                out.push(b';');
                prev_gen_line += 1;
                prev_gen_col = 0;
                first_in_line = true;
            }

            if !first_in_line {
                out.push(b',');
            }
            first_in_line = false;

            // SAFETY: buffer pre-allocated with 36 bytes per mapping + max_line
            // semicolons. Each mapping writes at most 5 × 7 = 35 VLQ bytes
            // plus 1 separator, and each line gap writes 1 semicolon.
            // Total capacity = sorted.len() * 36 + max_line + 1 ≥ all writes.
            unsafe {
                vlq_encode_unchecked(out, m.generated_column as i64 - prev_gen_col);
                prev_gen_col = m.generated_column as i64;

                if let Some(source) = m.source {
                    vlq_encode_unchecked(out, source as i64 - prev_source);
                    prev_source = source as i64;

                    vlq_encode_unchecked(out, m.original_line as i64 - prev_orig_line);
                    prev_orig_line = m.original_line as i64;

                    vlq_encode_unchecked(out, m.original_column as i64 - prev_orig_col);
                    prev_orig_col = m.original_column as i64;

                    if let Some(name) = m.name {
                        vlq_encode_unchecked(out, name as i64 - prev_name);
                        prev_name = name as i64;
                    }
                }
            }
        }
    }

    #[inline]
    #[allow(dead_code, reason = "used by tests and the parallel encoding path")]
    fn encode_sequential_impl<T: std::borrow::Borrow<Mapping>>(sorted: &[T]) -> String {
        let max_line = sorted.last().map_or(0, |m| m.borrow().generated_line as usize);
        let mut out: Vec<u8> = Vec::with_capacity(sorted.len() * 36 + max_line + 1);
        Self::encode_sequential_into(sorted, &mut out);

        debug_assert!(out.is_ascii());
        // SAFETY: vlq_encode only pushes bytes from BASE64_ENCODE (all ASCII),
        // and we only add b';' and b',' — all valid UTF-8.
        unsafe { String::from_utf8_unchecked(out) }
    }

    #[cfg(feature = "parallel")]
    fn encode_parallel_impl(sorted: &[&Mapping]) -> String {
        use rayon::prelude::*;

        let max_line = sorted
            .last()
            .expect("encode_parallel_impl requires non-empty sorted slice")
            .generated_line as usize;

        // Build line ranges: (start_idx, end_idx) into sorted slice
        let mut line_ranges: Vec<(usize, usize)> = vec![(0, 0); max_line + 1];
        let mut i = 0;
        while i < sorted.len() {
            let line = sorted[i].generated_line as usize;
            let start = i;
            while i < sorted.len() && sorted[i].generated_line as usize == line {
                i += 1;
            }
            line_ranges[line] = (start, i);
        }

        // Sequential scan: compute cumulative state at each line boundary
        let mut states: Vec<(i64, i64, i64, i64)> = Vec::with_capacity(max_line + 1);
        let mut prev_source: i64 = 0;
        let mut prev_orig_line: i64 = 0;
        let mut prev_orig_col: i64 = 0;
        let mut prev_name: i64 = 0;

        for &(start, end) in &line_ranges {
            states.push((prev_source, prev_orig_line, prev_orig_col, prev_name));
            for m in &sorted[start..end] {
                if let Some(source) = m.source {
                    prev_source = source as i64;
                    prev_orig_line = m.original_line as i64;
                    prev_orig_col = m.original_column as i64;
                    if let Some(name) = m.name {
                        prev_name = name as i64;
                    }
                }
            }
        }

        // Parallel: encode each line independently
        let encoded_lines: Vec<Vec<u8>> = line_ranges
            .par_iter()
            .zip(states.par_iter())
            .map(|(&(start, end), &(s, ol, oc, n))| {
                if start == end {
                    return Vec::new();
                }
                encode_mapping_slice(&sorted[start..end], s, ol, oc, n)
            })
            .collect();

        // Join with semicolons
        let total_len = encoded_lines.iter().map(|l| l.len()).sum::<usize>() + max_line;
        let mut out: Vec<u8> = Vec::with_capacity(total_len);
        for (i, bytes) in encoded_lines.iter().enumerate() {
            if i > 0 {
                out.push(b';');
            }
            out.extend_from_slice(bytes);
        }

        // SAFETY: vlq_encode only pushes bytes from BASE64_ENCODE (all ASCII),
        // and we only add b';' — all valid UTF-8.
        debug_assert!(out.is_ascii());
        unsafe { String::from_utf8_unchecked(out) }
    }

    /// Encode range mappings to a VLQ string.
    /// Returns `None` if no range mappings exist.
    fn encode_range_mappings(&self) -> Option<String> {
        if !self.mappings.iter().any(|m| m.is_range_mapping) {
            return None;
        }

        let ordered: Vec<&Mapping> = if self.assume_sorted || self.mappings_in_order
        {
            self.mappings.iter().collect()
        } else {
            let mut sorted: Vec<&Mapping> = self.mappings.iter().collect();
            sorted.sort_unstable_by(|a, b| {
                a.generated_line
                    .cmp(&b.generated_line)
                    .then(a.generated_column.cmp(&b.generated_column))
            });
            sorted
        };

        let max_line = ordered.last().map_or(0, |m| m.generated_line);
        let mut out: Vec<u8> = Vec::new();
        let mut ordered_idx = 0;

        for line in 0..=max_line {
            if line > 0 {
                out.push(b';');
            }
            let mut prev_offset: u64 = 0;
            let mut first_on_line = true;
            let mut line_local_idx: u64 = 0;

            while ordered_idx < ordered.len() && ordered[ordered_idx].generated_line == line {
                if ordered[ordered_idx].is_range_mapping {
                    if !first_on_line {
                        out.push(b',');
                    }
                    first_on_line = false;
                    let delta = line_local_idx - prev_offset;
                    vlq_encode_unsigned(&mut out, delta);
                    prev_offset = line_local_idx;
                }
                line_local_idx += 1;
                ordered_idx += 1;
            }
        }

        while out.last() == Some(&b';') {
            out.pop();
        }

        if out.is_empty() {
            return None;
        }

        debug_assert!(out.is_ascii());
        // SAFETY: vlq_encode_unsigned only pushes ASCII base64 chars,
        // and we only add b';' and b',' — all valid UTF-8.
        Some(unsafe { String::from_utf8_unchecked(out) })
    }

    /// Generate the source map as a JSON string.
    pub fn to_json(&self) -> String {
        use std::io::Write;

        // Encode scopes (may introduce names not yet in self.names)
        let (scopes_str, names_for_json) = if let Some(ref scopes_info) = self.scopes {
            let mut names = self.names.clone();
            let s = srcmap_scopes::encode_scopes(scopes_info, &mut names);
            (Some(s), std::borrow::Cow::Owned(names))
        } else {
            (None, std::borrow::Cow::Borrowed(&self.names))
        };

        // Estimate capacity for JSON output
        let sources_size: usize = self.sources.iter().map(|s| s.len() + 4).sum();
        let names_size: usize = names_for_json.iter().map(|n| n.len() + 4).sum();
        let content_size: usize =
            self.sources_content.iter().map(|c| c.as_ref().map_or(5, |s| s.len() + 4)).sum();
        // Estimate mapping size: ~6 bytes per mapping on average
        let mappings_estimate = self.mappings.len() * 6;
        let capacity = 100 + sources_size + names_size + mappings_estimate + content_size;

        let mut json: Vec<u8> = Vec::with_capacity(capacity);
        json.extend_from_slice(br#"{"version":3"#);

        if let Some(ref file) = self.file {
            json.extend_from_slice(br#","file":"#);
            json_quote_into(&mut json, file);
        }

        if let Some(ref root) = self.source_root {
            json.extend_from_slice(br#","sourceRoot":"#);
            json_quote_into(&mut json, root);
        }

        // sources
        json.extend_from_slice(br#","sources":["#);
        for (i, s) in self.sources.iter().enumerate() {
            if i > 0 {
                json.push(b',');
            }
            json_quote_into(&mut json, s);
        }
        json.push(b']');

        // sourcesContent (only if any content is set)
        if self.sources_content.iter().any(|c| c.is_some()) {
            json.extend_from_slice(br#","sourcesContent":["#);

            #[cfg(feature = "parallel")]
            {
                use rayon::prelude::*;

                let total_content: usize =
                    self.sources_content.iter().map(|c| c.as_ref().map_or(0, |s| s.len())).sum();

                if self.sources_content.len() >= 8 && total_content >= 8192 {
                    let quoted: Vec<String> = self
                        .sources_content
                        .par_iter()
                        .map(|c| match c {
                            Some(content) => json_quote(content),
                            None => "null".to_string(),
                        })
                        .collect();
                    for (i, q) in quoted.iter().enumerate() {
                        if i > 0 {
                            json.push(b',');
                        }
                        json.extend_from_slice(q.as_bytes());
                    }
                } else {
                    for (i, c) in self.sources_content.iter().enumerate() {
                        if i > 0 {
                            json.push(b',');
                        }
                        match c {
                            Some(content) => json_quote_into(&mut json, content),
                            None => json.extend_from_slice(b"null"),
                        }
                    }
                }
            }

            #[cfg(not(feature = "parallel"))]
            for (i, c) in self.sources_content.iter().enumerate() {
                if i > 0 {
                    json.push(b',');
                }
                match c {
                    Some(content) => json_quote_into(&mut json, content),
                    None => json.extend_from_slice(b"null"),
                }
            }

            json.push(b']');
        }

        // names
        json.extend_from_slice(br#","names":["#);
        for (i, n) in names_for_json.iter().enumerate() {
            if i > 0 {
                json.push(b',');
            }
            json_quote_into(&mut json, n);
        }
        json.push(b']');

        // mappings — VLQ string is pure base64/,/; so no escaping needed.
        // Write directly into the json buffer to avoid intermediate String allocation.
        json.extend_from_slice(br#","mappings":""#);
        self.encode_mappings_into(&mut json);
        json.push(b'"');

        // ignoreList
        if !self.ignore_list.is_empty() {
            json.extend_from_slice(br#","ignoreList":["#);
            for (i, &idx) in self.ignore_list.iter().enumerate() {
                if i > 0 {
                    json.push(b',');
                }
                let _ = write!(json, "{idx}");
            }
            json.push(b']');
        }

        // rangeMappings (only if any range mappings exist)
        if let Some(ref range_mappings) = self.encode_range_mappings() {
            json.extend_from_slice(br#","rangeMappings":""#);
            json.extend_from_slice(range_mappings.as_bytes());
            json.push(b'"');
        }

        // debugId
        if let Some(ref id) = self.debug_id {
            json.extend_from_slice(br#","debugId":"#);
            json_quote_into(&mut json, id);
        }

        // scopes (ECMA-426 scopes proposal)
        if let Some(ref s) = scopes_str {
            json.extend_from_slice(br#","scopes":"#);
            json_quote_into(&mut json, s);
        }

        json.push(b'}');

        // SAFETY: all content written is valid UTF-8 — ASCII JSON syntax, base64 VLQ,
        // and original UTF-8 strings passed through json_quote_into.
        unsafe { String::from_utf8_unchecked(json) }
    }

    /// Get the number of mappings.
    pub fn mapping_count(&self) -> usize {
        self.mappings.len()
    }

    /// Directly construct a `SourceMap` from the generator's internal state.
    ///
    /// This avoids the encode-then-decode round-trip (VLQ encode to JSON string,
    /// then re-parse) that would otherwise be needed in composition pipelines.
    pub fn to_decoded_map(&self) -> srcmap_sourcemap::SourceMap {
        let convert_mapping = |m: &Mapping| srcmap_sourcemap::Mapping {
            generated_line: m.generated_line,
            generated_column: m.generated_column,
            source: m.source.unwrap_or(u32::MAX),
            original_line: m.original_line,
            original_column: m.original_column,
            name: m.name.unwrap_or(u32::MAX),
            is_range_mapping: m.is_range_mapping,
        };

        let sm_mappings: Vec<srcmap_sourcemap::Mapping> =
            if self.assume_sorted || self.mappings_in_order {
                // Skip sort — iterate directly over the mappings vec
                self.mappings.iter().map(convert_mapping).collect()
            } else {
                // Sort mappings by (generated_line, generated_column) — same as encode_mappings
                let mut sorted: Vec<&Mapping> = self.mappings.iter().collect();
                sorted.sort_unstable_by(|a, b| {
                    a.generated_line
                        .cmp(&b.generated_line)
                        .then(a.generated_column.cmp(&b.generated_column))
                });
                sorted.iter().map(|m| convert_mapping(m)).collect()
            };

        // Build sources_content: convert Vec<Option<String>> → Vec<Option<String>>
        let sources_content: Vec<Option<String>> = self.sources_content.clone();

        // Build the source root-prefixed sources (matching what from_json does)
        let sources: Vec<String> = match &self.source_root {
            Some(root) if !root.is_empty() => {
                self.sources.iter().map(|s| format!("{root}{s}")).collect()
            }
            _ => self.sources.clone(),
        };

        srcmap_sourcemap::SourceMap::from_parts(
            self.file.clone(),
            self.source_root.clone(),
            sources,
            sources_content,
            self.names.clone(),
            sm_mappings,
            self.ignore_list.clone(),
            self.debug_id.clone(),
            None, // scopes are not included in decoded map (would need encoding/decoding)
        )
    }

    /// Consume the generator and return decomposed source map parts.
    ///
    /// Returns a [`SourceMapParts`] struct with individual fields (file, mappings,
    /// sources, names, etc.) without performing JSON serialization. Useful for
    /// NAPI/WASM bindings that need structured access to each field.
    pub fn into_parts(self) -> SourceMapParts {
        let mappings = self.encode_mappings();
        let range_mappings = self.encode_range_mappings();

        SourceMapParts {
            file: self.file,
            mappings,
            sources: self.sources,
            names: self.names,
            sources_content: self.sources_content,
            ignore_list: self.ignore_list,
            debug_id: self.debug_id,
            source_root: self.source_root,
            range_mappings,
        }
    }

    /// Serialize the source map as JSON directly into a writer.
    ///
    /// Streams JSON output to the writer without building the full JSON string
    /// in memory. Useful for writing directly to files or network streams.
    pub fn to_writer(&self, writer: &mut impl io::Write) -> io::Result<()> {
        // Encode scopes (may introduce names not yet in self.names)
        let (scopes_str, names_for_json) = if let Some(ref scopes_info) = self.scopes {
            let mut names = self.names.clone();
            let s = srcmap_scopes::encode_scopes(scopes_info, &mut names);
            (Some(s), std::borrow::Cow::Owned(names))
        } else {
            (None, std::borrow::Cow::Borrowed(&self.names))
        };

        writer.write_all(br#"{"version":3"#)?;

        if let Some(ref file) = self.file {
            writer.write_all(br#","file":"#)?;
            write_json_quoted(writer, file)?;
        }

        if let Some(ref root) = self.source_root {
            writer.write_all(br#","sourceRoot":"#)?;
            write_json_quoted(writer, root)?;
        }

        // sources
        writer.write_all(br#","sources":["#)?;
        for (i, s) in self.sources.iter().enumerate() {
            if i > 0 {
                writer.write_all(b",")?;
            }
            write_json_quoted(writer, s)?;
        }
        writer.write_all(b"]")?;

        // sourcesContent (only if any content is set)
        if self.sources_content.iter().any(|c| c.is_some()) {
            writer.write_all(br#","sourcesContent":["#)?;
            for (i, c) in self.sources_content.iter().enumerate() {
                if i > 0 {
                    writer.write_all(b",")?;
                }
                match c {
                    Some(content) => write_json_quoted(writer, content)?,
                    None => writer.write_all(b"null")?,
                }
            }
            writer.write_all(b"]")?;
        }

        // names
        writer.write_all(br#","names":["#)?;
        for (i, n) in names_for_json.iter().enumerate() {
            if i > 0 {
                writer.write_all(b",")?;
            }
            write_json_quoted(writer, n)?;
        }
        writer.write_all(b"]")?;

        // mappings
        writer.write_all(br#","mappings":""#)?;
        let mut vlq_buf: Vec<u8> = Vec::new();
        self.encode_mappings_into(&mut vlq_buf);
        writer.write_all(&vlq_buf)?;
        writer.write_all(b"\"")?;

        // ignoreList
        if !self.ignore_list.is_empty() {
            writer.write_all(br#","ignoreList":["#)?;
            for (i, &idx) in self.ignore_list.iter().enumerate() {
                if i > 0 {
                    writer.write_all(b",")?;
                }
                write!(writer, "{idx}")?;
            }
            writer.write_all(b"]")?;
        }

        // rangeMappings
        if let Some(ref range_mappings) = self.encode_range_mappings() {
            writer.write_all(br#","rangeMappings":""#)?;
            writer.write_all(range_mappings.as_bytes())?;
            writer.write_all(b"\"")?;
        }

        // debugId
        if let Some(ref id) = self.debug_id {
            writer.write_all(br#","debugId":"#)?;
            write_json_quoted(writer, id)?;
        }

        // scopes
        if let Some(ref s) = scopes_str {
            writer.write_all(br#","scopes":"#)?;
            write_json_quoted(writer, s)?;
        }

        writer.write_all(b"}")?;
        Ok(())
    }
}

/// Source map generator that encodes VLQ on-the-fly.
///
/// Unlike [`SourceMapGenerator`], which collects all mappings and sorts them
/// at finalization, `StreamingGenerator` encodes each mapping to VLQ immediately.
/// Mappings **must** be added in sorted order `(generated_line, generated_column)`.
///
/// This avoids intermediate `Vec<Mapping>` allocation, making it ideal for
/// streaming composition pipelines.
///
/// # Examples
///
/// ```rust
/// use srcmap_generator::StreamingGenerator;
///
/// let mut sg = StreamingGenerator::new(Some("bundle.js".to_string()));
/// let src = sg.add_source("src/app.ts");
/// sg.set_source_content(src, "const x = 1;".to_string());
///
/// // Mappings must be added in order
/// sg.add_mapping(0, 0, src, 0, 6);
/// sg.add_mapping(1, 0, src, 1, 0);
///
/// let json = sg.to_json();
/// assert!(json.contains(r#""version":3"#));
/// ```
#[derive(Debug)]
pub struct StreamingGenerator {
    file: Option<String>,
    source_root: Option<String>,
    sources: Vec<String>,
    sources_content: Vec<Option<String>>,
    names: Vec<String>,
    ignore_list: Vec<u32>,
    debug_id: Option<String>,

    // Dedup maps
    source_map: FxHashMap<String, u32>,
    name_map: FxHashMap<String, u32>,

    // Streaming VLQ state
    vlq_out: Vec<u8>,
    prev_gen_line: u32,
    prev_gen_col: i64,
    prev_source: i64,
    prev_orig_line: i64,
    prev_orig_col: i64,
    prev_name: i64,
    first_in_line: bool,
    mapping_count: usize,

    // Range mapping tracking
    line_local_index: u32,
    range_entries: Vec<(u32, u32)>,
}

impl StreamingGenerator {
    /// Create a new streaming source map generator.
    pub fn new(file: Option<String>) -> Self {
        Self {
            file,
            source_root: None,
            sources: Vec::new(),
            sources_content: Vec::new(),
            names: Vec::new(),
            ignore_list: Vec::new(),
            debug_id: None,
            source_map: FxHashMap::default(),
            name_map: FxHashMap::default(),
            vlq_out: Vec::with_capacity(1024),
            prev_gen_line: 0,
            prev_gen_col: 0,
            prev_source: 0,
            prev_orig_line: 0,
            prev_orig_col: 0,
            prev_name: 0,
            first_in_line: true,
            mapping_count: 0,
            line_local_index: 0,
            range_entries: Vec::new(),
        }
    }

    /// Create a new streaming source map generator with pre-allocated VLQ capacity.
    pub fn with_capacity(file: Option<String>, vlq_capacity: usize) -> Self {
        Self {
            file,
            source_root: None,
            sources: Vec::new(),
            sources_content: Vec::new(),
            names: Vec::new(),
            ignore_list: Vec::new(),
            debug_id: None,
            source_map: FxHashMap::default(),
            name_map: FxHashMap::default(),
            vlq_out: Vec::with_capacity(vlq_capacity),
            prev_gen_line: 0,
            prev_gen_col: 0,
            prev_source: 0,
            prev_orig_line: 0,
            prev_orig_col: 0,
            prev_name: 0,
            first_in_line: true,
            mapping_count: 0,
            line_local_index: 0,
            range_entries: Vec::new(),
        }
    }

    /// Set the source root prefix.
    pub fn set_source_root(&mut self, root: impl Into<String>) {
        self.source_root = Some(root.into());
    }

    /// Set the debug ID (UUID) for this source map (ECMA-426).
    pub fn set_debug_id(&mut self, id: impl Into<String>) {
        self.debug_id = Some(id.into());
    }

    /// Register a source file and return its index.
    #[inline]
    pub fn add_source(&mut self, source: &str) -> u32 {
        if let Some(&idx) = self.source_map.get(source) {
            return idx;
        }
        let idx = self.sources.len() as u32;
        self.sources.push(source.to_string());
        self.sources_content.push(None);
        self.source_map.insert(source.to_string(), idx);
        idx
    }

    /// Set the content for a source file.
    pub fn set_source_content(&mut self, source_idx: u32, content: impl Into<String>) {
        if (source_idx as usize) < self.sources_content.len() {
            self.sources_content[source_idx as usize] = Some(content.into());
        }
    }

    /// Register a name and return its index.
    #[inline]
    pub fn add_name(&mut self, name: &str) -> u32 {
        if let Some(&idx) = self.name_map.get(name) {
            return idx;
        }
        let idx = self.names.len() as u32;
        self.names.push(name.to_string());
        self.name_map.insert(name.to_string(), idx);
        idx
    }

    /// Add a source index to the ignore list.
    pub fn add_to_ignore_list(&mut self, source_idx: u32) {
        if !self.ignore_list.contains(&source_idx) {
            self.ignore_list.push(source_idx);
        }
    }

    /// Add a mapping with no source information (generated-only).
    ///
    /// Mappings must be added in sorted order `(generated_line, generated_column)`.
    #[inline]
    pub fn add_generated_mapping(&mut self, generated_line: u32, generated_column: u32) {
        self.advance_to_line(generated_line);

        // Reserve enough for separator (1) + 1 VLQ value (7) = 8 bytes
        self.vlq_out.reserve(8);

        if !self.first_in_line {
            self.vlq_out.push(b',');
        }
        self.first_in_line = false;

        // SAFETY: we just reserved 8 bytes, vlq_encode_unchecked needs at most 7.
        unsafe {
            vlq_encode_unchecked(&mut self.vlq_out, generated_column as i64 - self.prev_gen_col);
        }
        self.prev_gen_col = generated_column as i64;
        self.line_local_index += 1;
        self.mapping_count += 1;
    }

    /// Add a mapping from generated position to original position.
    ///
    /// Mappings must be added in sorted order `(generated_line, generated_column)`.
    #[inline]
    pub fn add_mapping(
        &mut self,
        generated_line: u32,
        generated_column: u32,
        source: u32,
        original_line: u32,
        original_column: u32,
    ) {
        self.advance_to_line(generated_line);

        // Reserve enough for separator (1) + 4 VLQ values (4 × 7 = 28) = 29 bytes
        self.vlq_out.reserve(29);

        if !self.first_in_line {
            self.vlq_out.push(b',');
        }
        self.first_in_line = false;

        // SAFETY: we reserved 29 bytes; 4 vlq_encode_unchecked calls use at most 28.
        unsafe {
            vlq_encode_unchecked(&mut self.vlq_out, generated_column as i64 - self.prev_gen_col);
            self.prev_gen_col = generated_column as i64;

            vlq_encode_unchecked(&mut self.vlq_out, source as i64 - self.prev_source);
            self.prev_source = source as i64;

            vlq_encode_unchecked(&mut self.vlq_out, original_line as i64 - self.prev_orig_line);
            self.prev_orig_line = original_line as i64;

            vlq_encode_unchecked(&mut self.vlq_out, original_column as i64 - self.prev_orig_col);
            self.prev_orig_col = original_column as i64;
        }

        self.line_local_index += 1;
        self.mapping_count += 1;
    }

    /// Add a range mapping from generated position to original position.
    ///
    /// Same as [`add_mapping`](Self::add_mapping) but marks this mapping as a range mapping
    /// (ECMA-426). Mappings must be added in sorted order `(generated_line, generated_column)`.
    #[inline]
    pub fn add_range_mapping(
        &mut self,
        generated_line: u32,
        generated_column: u32,
        source: u32,
        original_line: u32,
        original_column: u32,
    ) {
        self.advance_to_line(generated_line);
        self.range_entries.push((self.prev_gen_line, self.line_local_index));

        // Reserve enough for separator (1) + 4 VLQ values (4 × 7 = 28) = 29 bytes
        self.vlq_out.reserve(29);

        if !self.first_in_line {
            self.vlq_out.push(b',');
        }
        self.first_in_line = false;

        // SAFETY: we reserved 29 bytes; 4 vlq_encode_unchecked calls use at most 28.
        unsafe {
            vlq_encode_unchecked(&mut self.vlq_out, generated_column as i64 - self.prev_gen_col);
            self.prev_gen_col = generated_column as i64;

            vlq_encode_unchecked(&mut self.vlq_out, source as i64 - self.prev_source);
            self.prev_source = source as i64;

            vlq_encode_unchecked(&mut self.vlq_out, original_line as i64 - self.prev_orig_line);
            self.prev_orig_line = original_line as i64;

            vlq_encode_unchecked(&mut self.vlq_out, original_column as i64 - self.prev_orig_col);
            self.prev_orig_col = original_column as i64;
        }

        self.line_local_index += 1;
        self.mapping_count += 1;
    }

    /// Add a mapping with a name.
    ///
    /// Mappings must be added in sorted order `(generated_line, generated_column)`.
    #[inline]
    pub fn add_named_mapping(
        &mut self,
        generated_line: u32,
        generated_column: u32,
        source: u32,
        original_line: u32,
        original_column: u32,
        name: u32,
    ) {
        self.advance_to_line(generated_line);

        // Reserve enough for separator (1) + 5 VLQ values (5 × 7 = 35) = 36 bytes
        self.vlq_out.reserve(36);

        if !self.first_in_line {
            self.vlq_out.push(b',');
        }
        self.first_in_line = false;

        // SAFETY: we reserved 36 bytes; 5 vlq_encode_unchecked calls use at most 35.
        unsafe {
            vlq_encode_unchecked(&mut self.vlq_out, generated_column as i64 - self.prev_gen_col);
            self.prev_gen_col = generated_column as i64;

            vlq_encode_unchecked(&mut self.vlq_out, source as i64 - self.prev_source);
            self.prev_source = source as i64;

            vlq_encode_unchecked(&mut self.vlq_out, original_line as i64 - self.prev_orig_line);
            self.prev_orig_line = original_line as i64;

            vlq_encode_unchecked(&mut self.vlq_out, original_column as i64 - self.prev_orig_col);
            self.prev_orig_col = original_column as i64;

            vlq_encode_unchecked(&mut self.vlq_out, name as i64 - self.prev_name);
            self.prev_name = name as i64;
        }

        self.line_local_index += 1;
        self.mapping_count += 1;
    }

    /// Add a named range mapping from generated position to original position.
    ///
    /// Same as [`add_named_mapping`](Self::add_named_mapping) but marks this mapping as a range
    /// mapping (ECMA-426). Mappings must be added in sorted order
    /// `(generated_line, generated_column)`.
    #[inline]
    pub fn add_named_range_mapping(
        &mut self,
        generated_line: u32,
        generated_column: u32,
        source: u32,
        original_line: u32,
        original_column: u32,
        name: u32,
    ) {
        self.advance_to_line(generated_line);
        self.range_entries.push((self.prev_gen_line, self.line_local_index));

        // Reserve enough for separator (1) + 5 VLQ values (5 × 7 = 35) = 36 bytes
        self.vlq_out.reserve(36);

        if !self.first_in_line {
            self.vlq_out.push(b',');
        }
        self.first_in_line = false;

        // SAFETY: we reserved 36 bytes; 5 vlq_encode_unchecked calls use at most 35.
        unsafe {
            vlq_encode_unchecked(&mut self.vlq_out, generated_column as i64 - self.prev_gen_col);
            self.prev_gen_col = generated_column as i64;

            vlq_encode_unchecked(&mut self.vlq_out, source as i64 - self.prev_source);
            self.prev_source = source as i64;

            vlq_encode_unchecked(&mut self.vlq_out, original_line as i64 - self.prev_orig_line);
            self.prev_orig_line = original_line as i64;

            vlq_encode_unchecked(&mut self.vlq_out, original_column as i64 - self.prev_orig_col);
            self.prev_orig_col = original_column as i64;

            vlq_encode_unchecked(&mut self.vlq_out, name as i64 - self.prev_name);
            self.prev_name = name as i64;
        }

        self.line_local_index += 1;
        self.mapping_count += 1;
    }

    /// Get the number of mappings added so far.
    pub fn mapping_count(&self) -> usize {
        self.mapping_count
    }

    /// Advance VLQ output to the given generated line, emitting semicolons.
    #[inline]
    fn advance_to_line(&mut self, generated_line: u32) {
        while self.prev_gen_line < generated_line {
            self.vlq_out.push(b';');
            self.prev_gen_line += 1;
            self.prev_gen_col = 0;
            self.first_in_line = true;
            self.line_local_index = 0;
        }
    }

    /// Generate the source map as a JSON string.
    pub fn to_json(&self) -> String {
        use std::io::Write;

        let vlq = self.vlq_str();

        // Better capacity estimate to avoid reallocs
        let sources_size: usize = self.sources.iter().map(|s| s.len() + 4).sum();
        let names_size: usize = self.names.iter().map(|n| n.len() + 4).sum();
        let content_size: usize =
            self.sources_content.iter().map(|c| c.as_ref().map_or(5, |s| s.len() + 4)).sum();
        let capacity = 100 + sources_size + names_size + vlq.len() + content_size;

        let mut json: Vec<u8> = Vec::with_capacity(capacity);
        json.extend_from_slice(br#"{"version":3"#);

        if let Some(ref file) = self.file {
            json.extend_from_slice(br#","file":"#);
            json_quote_into(&mut json, file);
        }

        if let Some(ref root) = self.source_root {
            json.extend_from_slice(br#","sourceRoot":"#);
            json_quote_into(&mut json, root);
        }

        json.extend_from_slice(br#","sources":["#);
        for (i, s) in self.sources.iter().enumerate() {
            if i > 0 {
                json.push(b',');
            }
            json_quote_into(&mut json, s);
        }
        json.push(b']');

        if self.sources_content.iter().any(|c| c.is_some()) {
            json.extend_from_slice(br#","sourcesContent":["#);
            for (i, c) in self.sources_content.iter().enumerate() {
                if i > 0 {
                    json.push(b',');
                }
                match c {
                    Some(content) => json_quote_into(&mut json, content),
                    None => json.extend_from_slice(b"null"),
                }
            }
            json.push(b']');
        }

        json.extend_from_slice(br#","names":["#);
        for (i, n) in self.names.iter().enumerate() {
            if i > 0 {
                json.push(b',');
            }
            json_quote_into(&mut json, n);
        }
        json.push(b']');

        // VLQ string is pure base64/,/; — no escaping needed
        json.extend_from_slice(br#","mappings":""#);
        json.extend_from_slice(vlq.as_bytes());
        json.push(b'"');

        if !self.ignore_list.is_empty() {
            json.extend_from_slice(br#","ignoreList":["#);
            for (i, &idx) in self.ignore_list.iter().enumerate() {
                if i > 0 {
                    json.push(b',');
                }
                let _ = write!(json, "{idx}");
            }
            json.push(b']');
        }

        if let Some(ref range_mappings) = self.encode_range_mappings() {
            json.extend_from_slice(br#","rangeMappings":""#);
            json.extend_from_slice(range_mappings.as_bytes());
            json.push(b'"');
        }

        if let Some(ref id) = self.debug_id {
            json.extend_from_slice(br#","debugId":"#);
            json_quote_into(&mut json, id);
        }

        json.push(b'}');

        // SAFETY: all content written is valid UTF-8 — ASCII JSON syntax, base64 VLQ,
        // and original UTF-8 strings passed through json_quote_into.
        unsafe { String::from_utf8_unchecked(json) }
    }

    /// Directly construct a `SourceMap` from the streaming generator's state.
    ///
    /// Parses the already-encoded VLQ mappings to build a decoded `SourceMap`.
    /// More efficient than `to_json()` + `SourceMap::from_json()` since it
    /// skips JSON generation and parsing.
    ///
    /// # Panics
    ///
    /// Panics if the internal VLQ-encoded mappings string is corrupted or
    /// contains invalid VLQ sequences. This is not expected under normal use,
    /// since the streaming encoder always produces valid output.
    pub fn to_decoded_map(
        &self,
    ) -> Result<srcmap_sourcemap::SourceMap, srcmap_sourcemap::ParseError> {
        let vlq = self.vlq_str();
        let range_mappings = self.encode_range_mappings();

        let sources: Vec<String> = match &self.source_root {
            Some(root) if !root.is_empty() => {
                self.sources.iter().map(|s| format!("{root}{s}")).collect()
            }
            _ => self.sources.clone(),
        };

        srcmap_sourcemap::SourceMap::from_vlq_with_range_mappings(
            vlq,
            sources,
            self.names.clone(),
            self.file.clone(),
            self.source_root.clone(),
            self.sources_content.clone(),
            self.ignore_list.clone(),
            self.debug_id.clone(),
            range_mappings.as_deref(),
        )
    }

    /// Encode range mapping entries to a VLQ string.
    /// Returns `None` if no range mappings exist.
    fn encode_range_mappings(&self) -> Option<String> {
        if self.range_entries.is_empty() {
            return None;
        }

        let max_line = self.range_entries.last().map_or(0, |&(line, _)| line);
        let mut out: Vec<u8> = Vec::new();
        let mut entry_idx = 0;

        for line in 0..=max_line {
            if line > 0 {
                out.push(b';');
            }
            let mut prev_offset: u64 = 0;
            let mut first_on_line = true;

            while entry_idx < self.range_entries.len() && self.range_entries[entry_idx].0 == line {
                if !first_on_line {
                    out.push(b',');
                }
                first_on_line = false;
                let local_idx = self.range_entries[entry_idx].1 as u64;
                let delta = local_idx - prev_offset;
                vlq_encode_unsigned(&mut out, delta);
                prev_offset = local_idx;
                entry_idx += 1;
            }
        }

        while out.last() == Some(&b';') {
            out.pop();
        }

        if out.is_empty() {
            return None;
        }

        // SAFETY: VLQ output is always valid ASCII/UTF-8.
        Some(unsafe { String::from_utf8_unchecked(out) })
    }

    /// Get the VLQ mappings as a str slice, trimming trailing semicolons.
    fn vlq_str(&self) -> &str {
        let end = self.vlq_out.iter().rposition(|&b| b != b';').map_or(0, |i| i + 1);
        // SAFETY: VLQ output is always valid ASCII/UTF-8
        unsafe { std::str::from_utf8_unchecked(&self.vlq_out[..end]) }
    }

    /// Consume the streaming generator and return decomposed source map parts.
    ///
    /// Returns a [`SourceMapParts`] struct with individual fields (file, mappings,
    /// sources, names, etc.) without performing JSON serialization. Useful for
    /// NAPI/WASM bindings that need structured access to each field.
    pub fn into_parts(self) -> SourceMapParts {
        let range_mappings = self.encode_range_mappings();
        // Trim trailing semicolons from VLQ output
        let end = self.vlq_out.iter().rposition(|&b| b != b';').map_or(0, |i| i + 1);
        // SAFETY: VLQ output is always valid ASCII/UTF-8
        let mappings = unsafe { String::from_utf8_unchecked(self.vlq_out[..end].to_vec()) };

        SourceMapParts {
            file: self.file,
            mappings,
            sources: self.sources,
            names: self.names,
            sources_content: self.sources_content,
            ignore_list: self.ignore_list,
            debug_id: self.debug_id,
            source_root: self.source_root,
            range_mappings,
        }
    }

    /// Serialize the source map as JSON directly into a writer.
    ///
    /// Streams JSON output to the writer without building the full JSON string
    /// in memory. Useful for writing directly to files or network streams.
    pub fn to_writer(&self, writer: &mut impl io::Write) -> io::Result<()> {
        let vlq = self.vlq_str();

        writer.write_all(br#"{"version":3"#)?;

        if let Some(ref file) = self.file {
            writer.write_all(br#","file":"#)?;
            write_json_quoted(writer, file)?;
        }

        if let Some(ref root) = self.source_root {
            writer.write_all(br#","sourceRoot":"#)?;
            write_json_quoted(writer, root)?;
        }

        // sources
        writer.write_all(br#","sources":["#)?;
        for (i, s) in self.sources.iter().enumerate() {
            if i > 0 {
                writer.write_all(b",")?;
            }
            write_json_quoted(writer, s)?;
        }
        writer.write_all(b"]")?;

        // sourcesContent
        if self.sources_content.iter().any(|c| c.is_some()) {
            writer.write_all(br#","sourcesContent":["#)?;
            for (i, c) in self.sources_content.iter().enumerate() {
                if i > 0 {
                    writer.write_all(b",")?;
                }
                match c {
                    Some(content) => write_json_quoted(writer, content)?,
                    None => writer.write_all(b"null")?,
                }
            }
            writer.write_all(b"]")?;
        }

        // names
        writer.write_all(br#","names":["#)?;
        for (i, n) in self.names.iter().enumerate() {
            if i > 0 {
                writer.write_all(b",")?;
            }
            write_json_quoted(writer, n)?;
        }
        writer.write_all(b"]")?;

        // mappings
        writer.write_all(br#","mappings":""#)?;
        writer.write_all(vlq.as_bytes())?;
        writer.write_all(b"\"")?;

        // ignoreList
        if !self.ignore_list.is_empty() {
            writer.write_all(br#","ignoreList":["#)?;
            for (i, &idx) in self.ignore_list.iter().enumerate() {
                if i > 0 {
                    writer.write_all(b",")?;
                }
                write!(writer, "{idx}")?;
            }
            writer.write_all(b"]")?;
        }

        // rangeMappings
        if let Some(ref range_mappings) = self.encode_range_mappings() {
            writer.write_all(br#","rangeMappings":""#)?;
            writer.write_all(range_mappings.as_bytes())?;
            writer.write_all(b"\"")?;
        }

        // debugId
        if let Some(ref id) = self.debug_id {
            writer.write_all(br#","debugId":"#)?;
            write_json_quoted(writer, id)?;
        }

        writer.write_all(b"}")?;
        Ok(())
    }
}

/// Encode a slice of mappings for a single line to VLQ bytes.
///
/// Generated column starts at 0 (reset per line).
/// Cumulative state is passed in from the sequential pre-scan.
#[cfg(feature = "parallel")]
fn encode_mapping_slice(
    mappings: &[&Mapping],
    init_source: i64,
    init_orig_line: i64,
    init_orig_col: i64,
    init_name: i64,
) -> Vec<u8> {
    // Pre-allocate: 36 bytes per mapping (5 VLQ × 7 + 1 separator)
    let mut buf = Vec::with_capacity(mappings.len() * 36);
    let mut prev_gen_col: i64 = 0;
    let mut prev_source = init_source;
    let mut prev_orig_line = init_orig_line;
    let mut prev_orig_col = init_orig_col;
    let mut prev_name = init_name;
    let mut first = true;

    for m in mappings {
        if !first {
            buf.push(b',');
        }
        first = false;

        // SAFETY: buffer pre-allocated with 36 bytes per mapping.
        // Each iteration writes at most 5 × 7 = 35 VLQ bytes + 1 separator.
        unsafe {
            vlq_encode_unchecked(&mut buf, m.generated_column as i64 - prev_gen_col);
            prev_gen_col = m.generated_column as i64;

            if let Some(source) = m.source {
                vlq_encode_unchecked(&mut buf, source as i64 - prev_source);
                prev_source = source as i64;

                vlq_encode_unchecked(&mut buf, m.original_line as i64 - prev_orig_line);
                prev_orig_line = m.original_line as i64;

                vlq_encode_unchecked(&mut buf, m.original_column as i64 - prev_orig_col);
                prev_orig_col = m.original_column as i64;

                if let Some(name) = m.name {
                    vlq_encode_unchecked(&mut buf, name as i64 - prev_name);
                    prev_name = name as i64;
                }
            }
        }
    }

    buf
}

/// JSON-quote a string directly into a byte buffer (avoids UTF-8 validation overhead).
fn json_quote_into(out: &mut Vec<u8>, s: &str) {
    let bytes = s.as_bytes();
    out.push(b'"');

    let mut start = 0;
    for (i, &b) in bytes.iter().enumerate() {
        let escape: &[u8] = match b {
            b'"' => b"\\\"",
            b'\\' => b"\\\\",
            b'\n' => b"\\n",
            b'\r' => b"\\r",
            b'\t' => b"\\t",
            0x00..=0x1f => {
                out.extend_from_slice(&bytes[start..i]);
                let hex = b"0123456789abcdef";
                out.extend_from_slice(&[
                    b'\\',
                    b'u',
                    b'0',
                    b'0',
                    hex[(b >> 4) as usize],
                    hex[(b & 0xf) as usize],
                ]);
                start = i + 1;
                continue;
            }
            _ => continue,
        };
        out.extend_from_slice(&bytes[start..i]);
        out.extend_from_slice(escape);
        start = i + 1;
    }

    out.extend_from_slice(&bytes[start..]);
    out.push(b'"');
}

/// JSON-quote a string, returning a new String (used in parallel contexts).
#[cfg(feature = "parallel")]
fn json_quote(s: &str) -> String {
    let mut out = Vec::with_capacity(s.len() + 2);
    json_quote_into(&mut out, s);
    // SAFETY: json_quote_into only writes valid UTF-8 (ASCII escapes + original UTF-8 content).
    unsafe { String::from_utf8_unchecked(out) }
}

/// JSON-quote a string directly into a writer.
fn write_json_quoted(writer: &mut impl io::Write, s: &str) -> io::Result<()> {
    let mut buf = Vec::with_capacity(s.len() + 2);
    json_quote_into(&mut buf, s);
    writer.write_all(&buf)
}

// ── Tests ──────────────────────────────────────────────────────────

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn empty_generator() {
        let builder = SourceMapGenerator::new(None);
        let json = builder.to_json();
        assert!(json.contains(r#""version":3"#));
        assert!(json.contains(r#""mappings":"""#));
    }

    #[test]
    fn simple_mapping() {
        let mut builder = SourceMapGenerator::new(Some("output.js".to_string()));
        let src = builder.add_source("input.js");
        builder.add_mapping(0, 0, src, 0, 0);

        let json = builder.to_json();
        assert!(json.contains(r#""file":"output.js""#));
        assert!(json.contains(r#""sources":["input.js"]"#));

        // Verify roundtrip with parser
        let sm = srcmap_sourcemap::SourceMap::from_json(&json).unwrap();
        let loc = sm.original_position_for(0, 0).unwrap();
        assert_eq!(sm.source(loc.source), "input.js");
        assert_eq!(loc.line, 0);
        assert_eq!(loc.column, 0);
    }

    #[test]
    fn mapping_with_name() {
        let mut builder = SourceMapGenerator::new(None);
        let src = builder.add_source("input.js");
        let name = builder.add_name("myFunction");
        builder.add_named_mapping(0, 0, src, 0, 0, name);

        let json = builder.to_json();
        assert!(json.contains(r#""names":["myFunction"]"#));

        let sm = srcmap_sourcemap::SourceMap::from_json(&json).unwrap();
        let loc = sm.original_position_for(0, 0).unwrap();
        assert_eq!(loc.name, Some(0));
        assert_eq!(sm.name(0), "myFunction");
    }

    #[test]
    fn multiple_lines() {
        let mut builder = SourceMapGenerator::new(None);
        let src = builder.add_source("input.js");
        builder.add_mapping(0, 0, src, 0, 0);
        builder.add_mapping(1, 4, src, 1, 2);
        builder.add_mapping(2, 0, src, 2, 0);

        let json = builder.to_json();
        let sm = srcmap_sourcemap::SourceMap::from_json(&json).unwrap();
        assert_eq!(sm.line_count(), 3);

        let loc = sm.original_position_for(1, 4).unwrap();
        assert_eq!(loc.line, 1);
        assert_eq!(loc.column, 2);
    }

    #[test]
    fn multiple_sources() {
        let mut builder = SourceMapGenerator::new(None);
        let a = builder.add_source("a.js");
        let b = builder.add_source("b.js");
        builder.add_mapping(0, 0, a, 0, 0);
        builder.add_mapping(1, 0, b, 0, 0);

        let json = builder.to_json();
        let sm = srcmap_sourcemap::SourceMap::from_json(&json).unwrap();

        let loc0 = sm.original_position_for(0, 0).unwrap();
        let loc1 = sm.original_position_for(1, 0).unwrap();
        assert_eq!(sm.source(loc0.source), "a.js");
        assert_eq!(sm.source(loc1.source), "b.js");
    }

    #[test]
    fn source_content() {
        let mut builder = SourceMapGenerator::new(None);
        let src = builder.add_source("input.js");
        builder.set_source_content(src, "var x = 1;".to_string());
        builder.add_mapping(0, 0, src, 0, 0);

        let json = builder.to_json();
        assert!(json.contains(r#""sourcesContent":["var x = 1;"]"#));

        let sm = srcmap_sourcemap::SourceMap::from_json(&json).unwrap();
        assert_eq!(sm.sources_content[0], Some("var x = 1;".to_string()));
    }

    #[test]
    fn source_root() {
        let mut builder = SourceMapGenerator::new(None);
        builder.set_source_root("src/".to_string());
        let src = builder.add_source("input.js");
        builder.add_mapping(0, 0, src, 0, 0);

        let json = builder.to_json();
        assert!(json.contains(r#""sourceRoot":"src/""#));
    }

    #[test]
    fn ignore_list() {
        let mut builder = SourceMapGenerator::new(None);
        let _app = builder.add_source("app.js");
        let lib = builder.add_source("node_modules/lib.js");
        builder.add_to_ignore_list(lib);
        builder.add_mapping(0, 0, lib, 0, 0);

        let json = builder.to_json();
        assert!(json.contains(r#""ignoreList":[1]"#));
    }

    #[test]
    fn generated_only_mapping() {
        let mut builder = SourceMapGenerator::new(None);
        builder.add_generated_mapping(0, 0);

        let json = builder.to_json();
        let sm = srcmap_sourcemap::SourceMap::from_json(&json).unwrap();
        // Generated-only mapping → no source info
        assert!(sm.original_position_for(0, 0).is_none());
    }

    #[test]
    fn dedup_sources_and_names() {
        let mut builder = SourceMapGenerator::new(None);
        let s1 = builder.add_source("input.js");
        let s2 = builder.add_source("input.js"); // duplicate
        assert_eq!(s1, s2);

        let n1 = builder.add_name("foo");
        let n2 = builder.add_name("foo"); // duplicate
        assert_eq!(n1, n2);

        assert_eq!(builder.sources.len(), 1);
        assert_eq!(builder.names.len(), 1);
    }

    #[test]
    fn large_roundtrip() {
        let mut builder = SourceMapGenerator::new(Some("bundle.js".to_string()));

        for i in 0..5 {
            builder.add_source(&format!("src/file{i}.js"));
        }
        for i in 0..10 {
            builder.add_name(&format!("var{i}"));
        }

        // Add 1000 mappings across 100 lines
        for line in 0..100u32 {
            for col in 0..10u32 {
                let src = (line * 10 + col) % 5;
                let name = if col % 3 == 0 { Some(col % 10) } else { None };

                match name {
                    Some(n) => builder.add_named_mapping(line, col * 10, src, line, col * 5, n),
                    None => builder.add_mapping(line, col * 10, src, line, col * 5),
                }
            }
        }

        let json = builder.to_json();
        let sm = srcmap_sourcemap::SourceMap::from_json(&json).unwrap();

        assert_eq!(sm.mapping_count(), 1000);
        assert_eq!(sm.line_count(), 100);

        // Verify a few lookups
        let loc = sm.original_position_for(50, 30).unwrap();
        assert_eq!(loc.line, 50);
        assert_eq!(loc.column, 15);
    }

    #[test]
    fn json_escaping() {
        let mut builder = SourceMapGenerator::new(None);
        let src = builder.add_source("path/with\"quotes.js");
        builder.set_source_content(src, "line1\nline2\ttab".to_string());
        builder.add_mapping(0, 0, src, 0, 0);

        let json = builder.to_json();
        // Should be valid JSON
        let _: serde_json::Value = serde_json::from_str(&json).unwrap();
    }

    #[test]
    fn maybe_add_mapping_skips_redundant() {
        let mut builder = SourceMapGenerator::new(None);
        let src = builder.add_source("input.js");

        // First mapping — always added
        assert!(builder.maybe_add_mapping(0, 0, src, 10, 0));
        // Same source position, different generated column — redundant, skipped
        assert!(!builder.maybe_add_mapping(0, 5, src, 10, 0));
        // Different source position — added
        assert!(builder.maybe_add_mapping(0, 10, src, 11, 0));
        // Different generated line, same source position as last — added (new line resets)
        assert!(builder.maybe_add_mapping(1, 0, src, 11, 0));

        assert_eq!(builder.mapping_count(), 3);

        let json = builder.to_json();
        let sm = srcmap_sourcemap::SourceMap::from_json(&json).unwrap();
        assert_eq!(sm.mapping_count(), 3);
    }

    #[test]
    fn maybe_add_mapping_different_source() {
        let mut builder = SourceMapGenerator::new(None);
        let a = builder.add_source("a.js");
        let b = builder.add_source("b.js");

        assert!(builder.maybe_add_mapping(0, 0, a, 0, 0));
        // Same line/col but different source — not redundant
        assert!(builder.maybe_add_mapping(0, 5, b, 0, 0));

        assert_eq!(builder.mapping_count(), 2);
    }

    #[test]
    fn to_decoded_map_basic() {
        let mut builder = SourceMapGenerator::new(Some("output.js".to_string()));
        let src = builder.add_source("input.js");
        builder.add_mapping(0, 0, src, 0, 0);
        builder.add_mapping(1, 4, src, 1, 2);

        let sm = builder.to_decoded_map();
        assert_eq!(sm.mapping_count(), 2);
        assert_eq!(sm.line_count(), 2);

        let loc = sm.original_position_for(0, 0).unwrap();
        assert_eq!(sm.source(loc.source), "input.js");
        assert_eq!(loc.line, 0);
        assert_eq!(loc.column, 0);

        let loc = sm.original_position_for(1, 4).unwrap();
        assert_eq!(loc.line, 1);
        assert_eq!(loc.column, 2);
    }

    #[test]
    fn to_decoded_map_with_names() {
        let mut builder = SourceMapGenerator::new(None);
        let src = builder.add_source("input.js");
        let name = builder.add_name("myFunction");
        builder.add_named_mapping(0, 0, src, 0, 0, name);

        let sm = builder.to_decoded_map();
        let loc = sm.original_position_for(0, 0).unwrap();
        assert_eq!(loc.name, Some(0));
        assert_eq!(sm.name(0), "myFunction");
    }

    #[test]
    fn to_decoded_map_matches_json_roundtrip() {
        let mut builder = SourceMapGenerator::new(Some("bundle.js".to_string()));
        for i in 0..5 {
            builder.add_source(&format!("src/file{i}.js"));
        }
        for i in 0..10 {
            builder.add_name(&format!("var{i}"));
        }

        for line in 0..50u32 {
            for col in 0..10u32 {
                let src = (line * 10 + col) % 5;
                let name = if col % 3 == 0 { Some(col % 10) } else { None };
                match name {
                    Some(n) => builder.add_named_mapping(line, col * 10, src, line, col * 5, n),
                    None => builder.add_mapping(line, col * 10, src, line, col * 5),
                }
            }
        }

        // Compare decoded map vs JSON roundtrip
        let sm_decoded = builder.to_decoded_map();
        let json = builder.to_json();
        let sm_json = srcmap_sourcemap::SourceMap::from_json(&json).unwrap();

        assert_eq!(sm_decoded.mapping_count(), sm_json.mapping_count());
        assert_eq!(sm_decoded.line_count(), sm_json.line_count());

        // Verify all lookups match
        for m in sm_json.all_mappings() {
            let a = sm_json.original_position_for(m.generated_line, m.generated_column);
            let b = sm_decoded.original_position_for(m.generated_line, m.generated_column);
            match (a, b) {
                (Some(a), Some(b)) => {
                    assert_eq!(
                        a.source, b.source,
                        "source mismatch at ({}, {})",
                        m.generated_line, m.generated_column
                    );
                    assert_eq!(
                        a.line, b.line,
                        "line mismatch at ({}, {})",
                        m.generated_line, m.generated_column
                    );
                    assert_eq!(
                        a.column, b.column,
                        "column mismatch at ({}, {})",
                        m.generated_line, m.generated_column
                    );
                    assert_eq!(
                        a.name, b.name,
                        "name mismatch at ({}, {})",
                        m.generated_line, m.generated_column
                    );
                }
                (None, None) => {}
                _ => panic!("lookup mismatch at ({}, {})", m.generated_line, m.generated_column),
            }
        }
    }

    #[test]
    fn to_decoded_map_empty() {
        let builder = SourceMapGenerator::new(None);
        let sm = builder.to_decoded_map();
        assert_eq!(sm.mapping_count(), 0);
        assert_eq!(sm.line_count(), 0);
    }

    #[test]
    fn to_decoded_map_generated_only() {
        let mut builder = SourceMapGenerator::new(None);
        builder.add_generated_mapping(0, 0);

        let sm = builder.to_decoded_map();
        assert_eq!(sm.mapping_count(), 1);
        // Generated-only mapping has no source info
        assert!(sm.original_position_for(0, 0).is_none());
    }

    #[test]
    fn to_decoded_map_multiple_sources() {
        let mut builder = SourceMapGenerator::new(None);
        let a = builder.add_source("a.js");
        let b = builder.add_source("b.js");
        builder.add_mapping(0, 0, a, 0, 0);
        builder.add_mapping(1, 0, b, 0, 0);

        let sm = builder.to_decoded_map();
        let loc0 = sm.original_position_for(0, 0).unwrap();
        let loc1 = sm.original_position_for(1, 0).unwrap();
        assert_eq!(sm.source(loc0.source), "a.js");
        assert_eq!(sm.source(loc1.source), "b.js");
    }

    #[test]
    fn to_decoded_map_with_source_content() {
        let mut builder = SourceMapGenerator::new(None);
        let src = builder.add_source("input.js");
        builder.set_source_content(src, "var x = 1;".to_string());
        builder.add_mapping(0, 0, src, 0, 0);

        let sm = builder.to_decoded_map();
        assert_eq!(sm.sources_content[0], Some("var x = 1;".to_string()));
    }

    #[test]
    fn to_decoded_map_reverse_lookup() {
        let mut builder = SourceMapGenerator::new(None);
        let src = builder.add_source("input.js");
        builder.add_mapping(0, 0, src, 10, 5);

        let sm = builder.to_decoded_map();
        let loc = sm.generated_position_for("input.js", 10, 5).unwrap();
        assert_eq!(loc.line, 0);
        assert_eq!(loc.column, 0);
    }

    #[test]
    fn out_of_order_insertion_is_sorted_on_encode() {
        // Insert mappings in reverse position order. The incremental
        // `mappings_in_order` flag must flip to false so encode sorts them,
        // producing identical output to in-order insertion.
        let mut unsorted = SourceMapGenerator::new(None);
        let src = unsorted.add_source("input.js");
        unsorted.add_mapping(2, 0, src, 2, 0);
        unsorted.add_mapping(0, 5, src, 0, 5);
        unsorted.add_mapping(0, 0, src, 0, 0);
        unsorted.add_mapping(1, 0, src, 1, 0);

        let mut sorted = SourceMapGenerator::new(None);
        let src = sorted.add_source("input.js");
        sorted.add_mapping(0, 0, src, 0, 0);
        sorted.add_mapping(0, 5, src, 0, 5);
        sorted.add_mapping(1, 0, src, 1, 0);
        sorted.add_mapping(2, 0, src, 2, 0);

        assert_eq!(unsorted.encode_mappings(), sorted.encode_mappings());

        // And the decoded map resolves the reordered positions correctly.
        let sm = unsorted.to_decoded_map();
        let loc = sm.original_position_for(0, 5).unwrap();
        assert_eq!((loc.line, loc.column), (0, 5));
        let loc = sm.original_position_for(2, 0).unwrap();
        assert_eq!((loc.line, loc.column), (2, 0));
    }

    #[test]
    fn to_decoded_map_sparse_lines() {
        let mut builder = SourceMapGenerator::new(None);
        let src = builder.add_source("input.js");
        builder.add_mapping(0, 0, src, 0, 0);
        builder.add_mapping(5, 0, src, 5, 0);

        let sm = builder.to_decoded_map();
        assert_eq!(sm.line_count(), 6);
        assert!(sm.original_position_for(0, 0).is_some());
        assert!(sm.original_position_for(2, 0).is_none());
        assert!(sm.original_position_for(5, 0).is_some());
    }

    #[test]
    fn empty_lines_between_mappings() {
        let mut builder = SourceMapGenerator::new(None);
        let src = builder.add_source("input.js");
        builder.add_mapping(0, 0, src, 0, 0);
        // Skip lines 1-4
        builder.add_mapping(5, 0, src, 5, 0);

        let json = builder.to_json();
        let sm = srcmap_sourcemap::SourceMap::from_json(&json).unwrap();

        // Line 0 should have a mapping
        assert!(sm.original_position_for(0, 0).is_some());
        // Lines 1-4 should have no mappings
        assert!(sm.original_position_for(2, 0).is_none());
        // Line 5 should have a mapping
        assert!(sm.original_position_for(5, 0).is_some());
    }

    #[test]
    fn debug_id() {
        let mut builder = SourceMapGenerator::new(None);
        builder.set_debug_id("85314830-023f-4cf1-a267-535f4e37bb17".to_string());
        let src = builder.add_source("input.js");
        builder.add_mapping(0, 0, src, 0, 0);

        let json = builder.to_json();
        assert!(json.contains(r#""debugId":"85314830-023f-4cf1-a267-535f4e37bb17""#));

        let sm = srcmap_sourcemap::SourceMap::from_json(&json).unwrap();
        assert_eq!(sm.debug_id.as_deref(), Some("85314830-023f-4cf1-a267-535f4e37bb17"));
    }

    #[test]
    fn scopes_roundtrip() {
        use srcmap_scopes::{Binding, GeneratedRange, OriginalScope, Position, ScopeInfo};

        let mut builder = SourceMapGenerator::new(Some("bundle.js".to_string()));
        let src = builder.add_source("input.js");
        builder.set_source_content(
            src,
            "function hello(name) {\n  return name;\n}\nhello('world');".to_string(),
        );
        let name_hello = builder.add_name("hello");
        builder.add_named_mapping(0, 0, src, 0, 0, name_hello);
        builder.add_mapping(1, 0, src, 1, 0);

        // Set scopes
        builder.set_scopes(ScopeInfo {
            scopes: vec![Some(OriginalScope {
                start: Position { line: 0, column: 0 },
                end: Position { line: 3, column: 14 },
                name: None,
                kind: Some("global".to_string()),
                is_stack_frame: false,
                variables: vec!["hello".to_string()],
                children: vec![OriginalScope {
                    start: Position { line: 0, column: 9 },
                    end: Position { line: 2, column: 1 },
                    name: Some("hello".to_string()),
                    kind: Some("function".to_string()),
                    is_stack_frame: true,
                    variables: vec!["name".to_string()],
                    children: vec![],
                }],
            })],
            ranges: vec![GeneratedRange {
                start: Position { line: 0, column: 0 },
                end: Position { line: 3, column: 14 },
                is_stack_frame: false,
                is_hidden: false,
                definition: Some(0),
                call_site: None,
                bindings: vec![Binding::Expression("hello".to_string())],
                children: vec![GeneratedRange {
                    start: Position { line: 0, column: 9 },
                    end: Position { line: 2, column: 1 },
                    is_stack_frame: true,
                    is_hidden: false,
                    definition: Some(1),
                    call_site: None,
                    bindings: vec![Binding::Expression("name".to_string())],
                    children: vec![],
                }],
            }],
        });

        let json = builder.to_json();

        // Verify scopes field is present
        assert!(json.contains(r#""scopes":"#));

        // Parse back and verify
        let sm = srcmap_sourcemap::SourceMap::from_json(&json).unwrap();
        assert!(sm.scopes.is_some());

        let scopes_info = sm.scopes.unwrap();

        // Verify original scopes
        assert_eq!(scopes_info.scopes.len(), 1);
        let root_scope = scopes_info.scopes[0].as_ref().unwrap();
        assert_eq!(root_scope.kind.as_deref(), Some("global"));
        assert_eq!(root_scope.variables, vec!["hello"]);
        assert_eq!(root_scope.children.len(), 1);

        let fn_scope = &root_scope.children[0];
        assert_eq!(fn_scope.name.as_deref(), Some("hello"));
        assert_eq!(fn_scope.kind.as_deref(), Some("function"));
        assert!(fn_scope.is_stack_frame);
        assert_eq!(fn_scope.variables, vec!["name"]);

        // Verify generated ranges
        assert_eq!(scopes_info.ranges.len(), 1);
        let outer = &scopes_info.ranges[0];
        assert_eq!(outer.definition, Some(0));
        assert_eq!(outer.bindings, vec![Binding::Expression("hello".to_string())]);
        assert_eq!(outer.children.len(), 1);

        let inner = &outer.children[0];
        assert_eq!(inner.definition, Some(1));
        assert!(inner.is_stack_frame);
        assert_eq!(inner.bindings, vec![Binding::Expression("name".to_string())]);
    }

    #[test]
    fn scopes_with_inlining_roundtrip() {
        use srcmap_scopes::{
            Binding, CallSite, GeneratedRange, OriginalScope, Position, ScopeInfo,
        };

        let mut builder = SourceMapGenerator::new(None);
        let src = builder.add_source("input.js");
        builder.add_mapping(0, 0, src, 0, 0);

        builder.set_scopes(ScopeInfo {
            scopes: vec![Some(OriginalScope {
                start: Position { line: 0, column: 0 },
                end: Position { line: 10, column: 0 },
                name: None,
                kind: None,
                is_stack_frame: false,
                variables: vec!["x".to_string()],
                children: vec![OriginalScope {
                    start: Position { line: 1, column: 0 },
                    end: Position { line: 4, column: 1 },
                    name: Some("greet".to_string()),
                    kind: Some("function".to_string()),
                    is_stack_frame: true,
                    variables: vec!["msg".to_string()],
                    children: vec![],
                }],
            })],
            ranges: vec![GeneratedRange {
                start: Position { line: 0, column: 0 },
                end: Position { line: 10, column: 0 },
                is_stack_frame: false,
                is_hidden: false,
                definition: Some(0),
                call_site: None,
                bindings: vec![Binding::Expression("_x".to_string())],
                children: vec![GeneratedRange {
                    start: Position { line: 6, column: 0 },
                    end: Position { line: 8, column: 0 },
                    is_stack_frame: true,
                    is_hidden: false,
                    definition: Some(1),
                    call_site: Some(CallSite { source_index: 0, line: 8, column: 0 }),
                    bindings: vec![Binding::Expression("\"Hello\"".to_string())],
                    children: vec![],
                }],
            }],
        });

        let json = builder.to_json();
        let sm = srcmap_sourcemap::SourceMap::from_json(&json).unwrap();
        let info = sm.scopes.unwrap();

        // Verify call site on inlined range
        let inlined = &info.ranges[0].children[0];
        assert_eq!(inlined.call_site, Some(CallSite { source_index: 0, line: 8, column: 0 }));
        assert_eq!(inlined.bindings, vec![Binding::Expression("\"Hello\"".to_string())]);
    }

    #[test]
    fn set_source_content_out_of_bounds() {
        let mut builder = SourceMapGenerator::new(None);
        // No sources added, index 0 is out of bounds
        builder.set_source_content(0, "content".to_string());
        // Should silently do nothing
        let json = builder.to_json();
        assert!(!json.contains("content"));
    }

    #[test]
    fn add_to_ignore_list_dedup() {
        let mut builder = SourceMapGenerator::new(None);
        let idx = builder.add_source("vendor.js");
        builder.add_to_ignore_list(idx);
        builder.add_to_ignore_list(idx); // duplicate - should be deduped
        let json = builder.to_json();
        // Should only appear once in ignoreList
        let sm = srcmap_sourcemap::SourceMap::from_json(&json).unwrap();
        assert_eq!(sm.ignore_list, vec![0]);
    }

    #[test]
    fn to_decoded_map_with_source_root() {
        let mut builder = SourceMapGenerator::new(None);
        builder.set_source_root("src/".to_string());
        let src = builder.add_source("app.ts");
        builder.add_mapping(0, 0, src, 0, 0);
        let sm = builder.to_decoded_map();
        // Sources should be prefixed with source_root
        assert_eq!(sm.sources, vec!["src/app.ts"]);
    }

    #[test]
    fn json_escaping_special_chars() {
        let mut builder = SourceMapGenerator::new(None);
        let src = builder.add_source("a.js");
        // Content with special chars: quotes, backslash, newline, carriage return, tab, control char
        builder.set_source_content(src, "line1\nline2\r\ttab\\\"\x01end".to_string());
        builder.add_mapping(0, 0, src, 0, 0);
        let json = builder.to_json();
        // Verify it's valid JSON by parsing
        let sm = srcmap_sourcemap::SourceMap::from_json(&json).unwrap();
        assert_eq!(sm.sources_content, vec![Some("line1\nline2\r\ttab\\\"\x01end".to_string())]);
    }

    #[test]
    fn json_escaping_in_names() {
        let mut builder = SourceMapGenerator::new(None);
        let src = builder.add_source("a.js");
        let name = builder.add_name("func\"with\\special");
        builder.add_named_mapping(0, 0, src, 0, 0, name);
        let json = builder.to_json();
        let sm = srcmap_sourcemap::SourceMap::from_json(&json).unwrap();
        assert_eq!(sm.names[0], "func\"with\\special");
    }

    #[test]
    fn json_escaping_in_sources() {
        let mut builder = SourceMapGenerator::new(None);
        let src = builder.add_source("path/with\"quotes.js");
        builder.add_mapping(0, 0, src, 0, 0);
        let json = builder.to_json();
        let sm = srcmap_sourcemap::SourceMap::from_json(&json).unwrap();
        assert_eq!(sm.sources[0], "path/with\"quotes.js");
    }

    #[cfg(feature = "parallel")]
    mod parallel_tests {
        use super::*;

        fn build_large_generator(lines: u32, cols_per_line: u32) -> SourceMapGenerator {
            let mut builder = SourceMapGenerator::new(Some("bundle.js".to_string()));
            for i in 0..10 {
                let src = builder.add_source(&format!("src/file{i}.js"));
                builder.set_source_content(
                    src,
                    format!("// source file {i}\n{}", "x = 1;\n".repeat(100)),
                );
            }
            for i in 0..20 {
                builder.add_name(&format!("var{i}"));
            }

            for line in 0..lines {
                for col in 0..cols_per_line {
                    let src = (line * cols_per_line + col) % 10;
                    let name = if col % 3 == 0 { Some(col % 20) } else { None };
                    match name {
                        Some(n) => builder.add_named_mapping(line, col * 10, src, line, col * 5, n),
                        None => builder.add_mapping(line, col * 10, src, line, col * 5),
                    }
                }
            }
            builder
        }

        #[test]
        fn parallel_large_roundtrip() {
            let builder = build_large_generator(500, 20);
            let json = builder.to_json();
            let sm = srcmap_sourcemap::SourceMap::from_json(&json).unwrap();
            assert_eq!(sm.mapping_count(), 10000);
            assert_eq!(sm.line_count(), 500);

            // Verify lookups
            let loc = sm.original_position_for(250, 50).unwrap();
            assert_eq!(loc.line, 250);
            assert_eq!(loc.column, 25);
        }

        #[test]
        fn parallel_matches_sequential() {
            let builder = build_large_generator(500, 20);

            // Sort mappings the same way encode_mappings does
            let mut sorted: Vec<&Mapping> = builder.mappings.iter().collect();
            sorted.sort_unstable_by(|a, b| {
                a.generated_line
                    .cmp(&b.generated_line)
                    .then(a.generated_column.cmp(&b.generated_column))
            });

            let sequential = SourceMapGenerator::encode_sequential_impl(&sorted);
            let parallel = SourceMapGenerator::encode_parallel_impl(&sorted);
            assert_eq!(sequential, parallel);
        }

        #[test]
        fn parallel_with_sparse_lines() {
            let mut builder = SourceMapGenerator::new(None);
            let src = builder.add_source("input.js");

            // Add mappings on lines 0, 100, 200, ... (sparse)
            for i in 0..50 {
                let line = i * 100;
                for col in 0..100u32 {
                    builder.add_mapping(line, col * 10, src, line, col * 5);
                }
            }

            let json = builder.to_json();
            let sm = srcmap_sourcemap::SourceMap::from_json(&json).unwrap();
            assert_eq!(sm.mapping_count(), 5000);

            // Verify empty lines have no mappings
            assert!(sm.original_position_for(50, 0).is_none());
            // Verify populated lines work
            let loc = sm.original_position_for(200, 50).unwrap();
            assert_eq!(loc.line, 200);
            assert_eq!(loc.column, 25);
        }
    }

    // ── StreamingGenerator tests ────────────────────────────────

    #[test]
    fn streaming_basic() {
        let mut sg = StreamingGenerator::new(Some("out.js".to_string()));
        let src = sg.add_source("input.js");
        sg.add_mapping(0, 0, src, 0, 0);
        sg.add_mapping(1, 0, src, 1, 0);

        let json = sg.to_json();
        let sm = srcmap_sourcemap::SourceMap::from_json(&json).unwrap();
        assert_eq!(sm.sources, vec!["input.js"]);
        assert_eq!(sm.mapping_count(), 2);

        let loc0 = sm.original_position_for(0, 0).unwrap();
        assert_eq!(sm.source(loc0.source), "input.js");
        assert_eq!(loc0.line, 0);

        let loc1 = sm.original_position_for(1, 0).unwrap();
        assert_eq!(loc1.line, 1);
    }

    #[test]
    fn streaming_with_names() {
        let mut sg = StreamingGenerator::new(None);
        let src = sg.add_source("a.js");
        let name = sg.add_name("foo");
        sg.add_named_mapping(0, 0, src, 0, 0, name);

        let sm = srcmap_sourcemap::SourceMap::from_json(&sg.to_json()).unwrap();
        let loc = sm.original_position_for(0, 0).unwrap();
        assert_eq!(loc.name, Some(0));
        assert_eq!(sm.name(0), "foo");
    }

    #[test]
    fn streaming_generated_only() {
        let mut sg = StreamingGenerator::new(None);
        let src = sg.add_source("a.js");
        sg.add_generated_mapping(0, 0);
        sg.add_mapping(0, 5, src, 0, 0);

        let sm = srcmap_sourcemap::SourceMap::from_json(&sg.to_json()).unwrap();
        assert_eq!(sm.mapping_count(), 2);
        assert!(sm.original_position_for(0, 0).is_none());
        assert!(sm.original_position_for(0, 5).is_some());
    }

    #[test]
    fn streaming_matches_regular_generator() {
        let mut regular = SourceMapGenerator::new(Some("out.js".to_string()));
        let mut streaming = StreamingGenerator::new(Some("out.js".to_string()));

        let src_r = regular.add_source("a.js");
        let src_s = streaming.add_source("a.js");

        let name_r = regular.add_name("hello");
        let name_s = streaming.add_name("hello");

        regular.set_source_content(src_r, "var hello;".to_string());
        streaming.set_source_content(src_s, "var hello;".to_string());

        regular.add_named_mapping(0, 0, src_r, 0, 0, name_r);
        streaming.add_named_mapping(0, 0, src_s, 0, 0, name_s);

        regular.add_mapping(0, 10, src_r, 0, 4);
        streaming.add_mapping(0, 10, src_s, 0, 4);

        regular.add_mapping(1, 0, src_r, 1, 0);
        streaming.add_mapping(1, 0, src_s, 1, 0);

        let sm_r = srcmap_sourcemap::SourceMap::from_json(&regular.to_json()).unwrap();
        let sm_s = srcmap_sourcemap::SourceMap::from_json(&streaming.to_json()).unwrap();

        assert_eq!(sm_r.mapping_count(), sm_s.mapping_count());
        assert_eq!(sm_r.sources, sm_s.sources);
        assert_eq!(sm_r.names, sm_s.names);
        assert_eq!(sm_r.sources_content, sm_s.sources_content);

        for (a, b) in sm_r.all_mappings().iter().zip(sm_s.all_mappings().iter()) {
            assert_eq!(a.generated_line, b.generated_line);
            assert_eq!(a.generated_column, b.generated_column);
            assert_eq!(a.source, b.source);
            assert_eq!(a.original_line, b.original_line);
            assert_eq!(a.original_column, b.original_column);
            assert_eq!(a.name, b.name);
        }
    }

    #[test]
    fn streaming_to_decoded_map() {
        let mut sg = StreamingGenerator::new(None);
        let src = sg.add_source("test.js");
        sg.add_mapping(0, 0, src, 0, 0);
        sg.add_mapping(2, 5, src, 1, 3);

        let sm = sg.to_decoded_map().unwrap();
        assert_eq!(sm.mapping_count(), 2);
        assert_eq!(sm.sources, vec!["test.js"]);

        let loc = sm.original_position_for(2, 5).unwrap();
        assert_eq!(loc.line, 1);
        assert_eq!(loc.column, 3);
    }

    #[test]
    fn streaming_source_dedup() {
        let mut sg = StreamingGenerator::new(None);
        let src1 = sg.add_source("a.js");
        let src2 = sg.add_source("a.js");
        assert_eq!(src1, src2);
        assert_eq!(sg.sources.len(), 1);
    }

    #[test]
    fn streaming_ignore_list() {
        let mut sg = StreamingGenerator::new(None);
        let src = sg.add_source("vendor.js");
        sg.add_to_ignore_list(src);
        sg.add_mapping(0, 0, src, 0, 0);

        let sm = srcmap_sourcemap::SourceMap::from_json(&sg.to_json()).unwrap();
        assert_eq!(sm.ignore_list, vec![0]);
    }

    #[test]
    fn streaming_empty() {
        let sg = StreamingGenerator::new(None);
        let json = sg.to_json();
        let sm = srcmap_sourcemap::SourceMap::from_json(&json).unwrap();
        assert_eq!(sm.mapping_count(), 0);
    }

    #[test]
    fn streaming_sparse_lines() {
        let mut sg = StreamingGenerator::new(None);
        let src = sg.add_source("a.js");
        sg.add_mapping(0, 0, src, 0, 0);
        sg.add_mapping(5, 0, src, 5, 0);

        let sm = srcmap_sourcemap::SourceMap::from_json(&sg.to_json()).unwrap();
        assert_eq!(sm.mapping_count(), 2);
        assert!(sm.original_position_for(0, 0).is_some());
        assert!(sm.original_position_for(5, 0).is_some());
    }

    // ── Range mapping tests ───────────────────────────────────

    #[test]
    fn range_mapping_basic() {
        let mut builder = SourceMapGenerator::new(None);
        let src = builder.add_source("input.js");
        builder.add_range_mapping(0, 0, src, 0, 0);
        builder.add_mapping(0, 5, src, 0, 10);

        let json = builder.to_json();
        assert!(json.contains(r#""rangeMappings":"A""#));
    }

    #[test]
    fn range_mapping_multiple_on_line() {
        let mut builder = SourceMapGenerator::new(None);
        let src = builder.add_source("input.js");
        builder.add_range_mapping(0, 0, src, 0, 0);
        builder.add_mapping(0, 5, src, 0, 10);
        builder.add_range_mapping(0, 10, src, 0, 20);

        let json = builder.to_json();
        assert!(json.contains(r#""rangeMappings":"A,C""#));
    }

    #[test]
    fn range_mapping_multi_line() {
        let mut builder = SourceMapGenerator::new(None);
        let src = builder.add_source("input.js");
        builder.add_range_mapping(0, 0, src, 0, 0);
        builder.add_range_mapping(1, 0, src, 1, 0);

        let json = builder.to_json();
        assert!(json.contains(r#""rangeMappings":"A;A""#));
    }

    #[test]
    fn no_range_mappings_omits_field() {
        let mut builder = SourceMapGenerator::new(None);
        let src = builder.add_source("input.js");
        builder.add_mapping(0, 0, src, 0, 0);

        let json = builder.to_json();
        assert!(!json.contains("rangeMappings"));
    }

    #[test]
    fn named_range_mapping() {
        let mut builder = SourceMapGenerator::new(None);
        let src = builder.add_source("input.js");
        let name = builder.add_name("foo");
        builder.add_named_range_mapping(0, 0, src, 0, 0, name);

        let json = builder.to_json();
        assert!(json.contains(r#""rangeMappings":"A""#));
    }

    #[test]
    fn to_decoded_map_preserves_range_mappings() {
        let mut builder = SourceMapGenerator::new(None);
        let src = builder.add_source("input.js");
        builder.add_range_mapping(0, 0, src, 0, 0);
        builder.add_mapping(0, 5, src, 0, 10);

        let sm = builder.to_decoded_map();
        assert!(sm.has_range_mappings());
        let mappings = sm.all_mappings();
        assert!(mappings[0].is_range_mapping);
        assert!(!mappings[1].is_range_mapping);
    }

    // ── Streaming range mapping tests ────────────────────────────

    #[test]
    fn streaming_range_mapping_basic() {
        let mut sg = StreamingGenerator::new(None);
        let src = sg.add_source("input.js");
        sg.add_range_mapping(0, 0, src, 0, 0);
        sg.add_mapping(0, 5, src, 0, 10);

        let json = sg.to_json();
        assert!(json.contains(r#""rangeMappings":"A""#));
    }

    #[test]
    fn streaming_range_mapping_roundtrip() {
        let mut sg = StreamingGenerator::new(None);
        let src = sg.add_source("input.js");
        sg.add_range_mapping(0, 0, src, 0, 0);
        sg.add_mapping(0, 5, src, 0, 10);

        let sm = sg.to_decoded_map().unwrap();
        assert!(sm.has_range_mappings());
        let mappings = sm.all_mappings();
        assert!(mappings[0].is_range_mapping);
        assert!(!mappings[1].is_range_mapping);
    }

    #[test]
    fn streaming_range_and_named_range() {
        let mut sg = StreamingGenerator::new(None);
        let src = sg.add_source("input.js");
        let name = sg.add_name("foo");
        sg.add_range_mapping(0, 0, src, 0, 0);
        sg.add_named_range_mapping(0, 10, src, 0, 5, name);

        let json = sg.to_json();
        assert!(json.contains(r#""rangeMappings":"A,B""#));

        let sm = sg.to_decoded_map().unwrap();
        assert!(sm.has_range_mappings());
        let mappings = sm.all_mappings();
        assert!(mappings[0].is_range_mapping);
        assert!(mappings[1].is_range_mapping);
    }

    #[test]
    fn streaming_range_mapping_matches_regular() {
        let mut regular = SourceMapGenerator::new(None);
        let mut streaming = StreamingGenerator::new(None);

        let src_r = regular.add_source("input.js");
        let src_s = streaming.add_source("input.js");

        regular.add_range_mapping(0, 0, src_r, 0, 0);
        streaming.add_range_mapping(0, 0, src_s, 0, 0);

        regular.add_mapping(0, 5, src_r, 0, 10);
        streaming.add_mapping(0, 5, src_s, 0, 10);

        regular.add_range_mapping(0, 10, src_r, 0, 20);
        streaming.add_range_mapping(0, 10, src_s, 0, 20);

        regular.add_range_mapping(1, 0, src_r, 1, 0);
        streaming.add_range_mapping(1, 0, src_s, 1, 0);

        let json_r = regular.to_json();
        let json_s = streaming.to_json();

        let sm_r = srcmap_sourcemap::SourceMap::from_json(&json_r).unwrap();
        let sm_s = srcmap_sourcemap::SourceMap::from_json(&json_s).unwrap();

        assert_eq!(sm_r.mapping_count(), sm_s.mapping_count());

        for (a, b) in sm_r.all_mappings().iter().zip(sm_s.all_mappings().iter()) {
            assert_eq!(a.generated_line, b.generated_line);
            assert_eq!(a.generated_column, b.generated_column);
            assert_eq!(a.source, b.source);
            assert_eq!(a.original_line, b.original_line);
            assert_eq!(a.original_column, b.original_column);
            assert_eq!(a.name, b.name);
            assert_eq!(a.is_range_mapping, b.is_range_mapping);
        }
    }

    // ── into_parts tests ────────────────────────────────────

    #[test]
    fn into_parts_basic() {
        let mut builder = SourceMapGenerator::new(Some("output.js".to_string()));
        let src = builder.add_source("input.js");
        builder.set_source_content(src, "var x = 1;".to_string());
        let name = builder.add_name("x");
        builder.add_named_mapping(0, 0, src, 0, 4, name);
        builder.add_mapping(1, 0, src, 1, 0);
        builder.set_debug_id("test-id");

        let json = builder.to_json();
        let sm_json = srcmap_sourcemap::SourceMap::from_json(&json).unwrap();

        // Rebuild with same data for into_parts
        let mut builder2 = SourceMapGenerator::new(Some("output.js".to_string()));
        let src2 = builder2.add_source("input.js");
        builder2.set_source_content(src2, "var x = 1;".to_string());
        let name2 = builder2.add_name("x");
        builder2.add_named_mapping(0, 0, src2, 0, 4, name2);
        builder2.add_mapping(1, 0, src2, 1, 0);
        builder2.set_debug_id("test-id");

        let parts = builder2.into_parts();
        assert_eq!(parts.file, Some("output.js".to_string()));
        assert_eq!(parts.sources, vec!["input.js"]);
        assert_eq!(parts.names, vec!["x"]);
        assert_eq!(parts.sources_content, vec![Some("var x = 1;".to_string())]);
        assert_eq!(parts.debug_id, Some("test-id".to_string()));
        assert!(!parts.mappings.is_empty());

        // Verify the mappings string produces the same source map
        let sm_parts = srcmap_sourcemap::SourceMap::from_vlq(
            &parts.mappings,
            parts.sources,
            parts.names,
            parts.file,
            parts.source_root,
            parts.sources_content,
            parts.ignore_list,
            parts.debug_id,
        )
        .unwrap();
        assert_eq!(sm_parts.mapping_count(), sm_json.mapping_count());
    }

    #[test]
    fn into_parts_empty() {
        let builder = SourceMapGenerator::new(None);
        let parts = builder.into_parts();
        assert_eq!(parts.file, None);
        assert!(parts.mappings.is_empty());
        assert!(parts.sources.is_empty());
        assert!(parts.names.is_empty());
    }

    #[test]
    fn into_parts_with_ignore_list() {
        let mut builder = SourceMapGenerator::new(None);
        let src = builder.add_source("vendor.js");
        builder.add_to_ignore_list(src);
        builder.add_mapping(0, 0, src, 0, 0);

        let parts = builder.into_parts();
        assert_eq!(parts.ignore_list, vec![0]);
    }

    #[test]
    fn into_parts_with_range_mappings() {
        let mut builder = SourceMapGenerator::new(None);
        let src = builder.add_source("input.js");
        builder.add_range_mapping(0, 0, src, 0, 0);
        builder.add_mapping(0, 5, src, 0, 10);

        let parts = builder.into_parts();
        assert!(parts.range_mappings.is_some());
    }

    #[test]
    fn streaming_into_parts() {
        let mut sg = StreamingGenerator::new(Some("out.js".to_string()));
        let src = sg.add_source("input.js");
        sg.set_source_content(src, "var x = 1;".to_string());
        let name = sg.add_name("x");
        sg.add_named_mapping(0, 0, src, 0, 4, name);
        sg.add_mapping(1, 0, src, 1, 0);

        let parts = sg.into_parts();
        assert_eq!(parts.file, Some("out.js".to_string()));
        assert_eq!(parts.sources, vec!["input.js"]);
        assert_eq!(parts.names, vec!["x"]);
        assert!(!parts.mappings.is_empty());
    }

    // ── to_writer tests ────────────────────────────────────

    #[test]
    fn to_writer_matches_to_json() {
        let mut builder = SourceMapGenerator::new(Some("output.js".to_string()));
        let src = builder.add_source("input.js");
        builder.set_source_content(src, "var x = 1;".to_string());
        let name = builder.add_name("x");
        builder.add_named_mapping(0, 0, src, 0, 4, name);
        builder.add_mapping(1, 0, src, 1, 0);

        let json = builder.to_json();
        let mut buf = Vec::new();
        builder.to_writer(&mut buf).unwrap();
        let writer_output = String::from_utf8(buf).unwrap();

        assert_eq!(json, writer_output);
    }

    #[test]
    fn to_writer_empty() {
        let builder = SourceMapGenerator::new(None);
        let mut buf = Vec::new();
        builder.to_writer(&mut buf).unwrap();
        let output = String::from_utf8(buf).unwrap();
        assert!(output.contains(r#""version":3"#));
        assert!(output.contains(r#""mappings":"""#));
    }

    #[test]
    fn to_writer_with_all_fields() {
        let mut builder = SourceMapGenerator::new(Some("bundle.js".to_string()));
        builder.set_source_root("src/");
        builder.set_debug_id("test-uuid");
        let src = builder.add_source("app.ts");
        builder.set_source_content(src, "const x = 1;".to_string());
        builder.add_to_ignore_list(src);
        let name = builder.add_name("x");
        builder.add_named_mapping(0, 0, src, 0, 6, name);

        let json = builder.to_json();
        let mut buf = Vec::new();
        builder.to_writer(&mut buf).unwrap();
        let writer_output = String::from_utf8(buf).unwrap();

        assert_eq!(json, writer_output);

        // Verify it parses correctly
        let sm = srcmap_sourcemap::SourceMap::from_json(&writer_output).unwrap();
        assert_eq!(sm.source(0), "src/app.ts");
        assert_eq!(sm.name(0), "x");
    }

    #[test]
    fn streaming_to_writer_matches_to_json() {
        let mut sg = StreamingGenerator::new(Some("out.js".to_string()));
        let src = sg.add_source("input.js");
        sg.set_source_content(src, "var x = 1;".to_string());
        let name = sg.add_name("x");
        sg.add_named_mapping(0, 0, src, 0, 4, name);
        sg.add_mapping(1, 0, src, 1, 0);

        let json = sg.to_json();
        let mut buf = Vec::new();
        sg.to_writer(&mut buf).unwrap();
        let writer_output = String::from_utf8(buf).unwrap();

        assert_eq!(json, writer_output);
    }
}