adotenv 0.2.0

use alloc::{borrow::Cow, string::String, vec::Vec};
use core::{fmt, ops::Range};

use crate::{Diagnostic, DiagnosticCode, EditError, LineIndex, PositionError};

/// Quoting used by a literal value in the source.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
#[non_exhaustive]
pub enum Quote {
    /// An unquoted value.
    None,
    /// Fully literal single quotes.
    Single,
    /// Double quotes with Portable escapes.
    Double,
}

/// A declaration's assignment state, independent of any environment lookup.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
#[non_exhaustive]
pub enum AssignmentState {
    /// A declaration without `=`; this is not an empty string assignment.
    Bare,
    /// An assigned empty string; quoting is recorded separately.
    Empty,
    /// An assigned non-empty literal value.
    Value,
}

/// A physical source line ending, retained exactly.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
#[non_exhaustive]
pub enum LineEnding {
    /// No terminator at EOF.
    None,
    /// A line feed.
    Lf,
    /// A carriage return followed by a line feed.
    CrLf,
    /// A lone carriage return, diagnosed by Portable parsing.
    Cr,
}
impl LineEnding {
    /// The original ending bytes as text.
    #[must_use]
    pub const fn as_str(self) -> &'static str {
        match self {
            Self::None => "",
            Self::Lf => "\n",
            Self::CrLf => "\r\n",
            Self::Cr => "\r",
        }
    }
}

/// The kind of a lossless source item.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
#[non_exhaustive]
pub enum ItemKind {
    /// A blank physical line.
    Blank,
    /// A comment physical line.
    Comment,
    /// An assignment or bare declaration, possibly spanning physical lines.
    Entry,
    /// A malformed statement retained verbatim.
    Invalid,
}

/// Raw token ranges into a document's source; absent syntax is represented by `None`.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct EntryTokens {
    /// Leading spaces or tabs.
    pub indent: Range<usize>,
    /// The optional `export` keyword, excluding its separator.
    pub export: Option<Range<usize>>,
    /// Whitespace after the export keyword.
    pub space_after_export: Range<usize>,
    /// The key spelling.
    pub key: Range<usize>,
    /// Whitespace between the key and equals sign (or bare declaration tail).
    pub space_before_eq: Range<usize>,
    /// The equals sign; absent for bare declarations.
    pub eq: Option<Range<usize>>,
    /// Whitespace between equals and the value.
    pub space_after_eq: Range<usize>,
    /// The raw value token, including any quotes; absent for bare declarations.
    pub value: Option<Range<usize>>,
    /// The raw value body, excluding quotes.
    pub body: Option<Range<usize>>,
    /// Whitespace after the value and before any comment.
    pub trailing_space: Range<usize>,
    /// An inline comment, including its hash.
    pub inline_comment: Option<Range<usize>>,
}

#[derive(Debug, Clone, PartialEq, Eq)]
pub(crate) struct DecodeSegment {
    pub decoded: Range<usize>,
    pub raw: Range<usize>,
}

#[derive(Debug, Clone, PartialEq, Eq)]
pub(crate) struct EntryData {
    pub item: usize,
    pub line: usize,
    pub tokens: EntryTokens,
    pub quote: Quote,
    pub state: AssignmentState,
    pub decoded: Option<String>,
    pub map: Vec<DecodeSegment>,
}

#[derive(Debug, Clone, PartialEq, Eq)]
pub(crate) struct ItemData {
    pub kind: ItemKind,
    pub span: Range<usize>,
    pub ending: LineEnding,
    pub entry: Option<usize>,
    pub comment: Option<Range<usize>>,
    pub invalid: Option<Diagnostic>,
}

/// A lossless Portable document retaining borrowed or explicitly owned UTF-8 source.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct Document<'src> {
    pub(crate) source: Cow<'src, str>,
    pub(crate) items: Vec<ItemData>,
    pub(crate) entries: Vec<EntryData>,
    pub(crate) bom: bool,
}

impl Document<'_> {
    /// The complete, unmodified input, including the BOM and malformed syntax.
    #[must_use]
    pub fn source(&self) -> &str {
        &self.source
    }
    /// All source items in order; a leading BOM is the separate prelude.
    pub fn items(&self) -> impl DoubleEndedIterator<Item = Item<'_>> + ExactSizeIterator {
        (0..self.items.len()).map(|index| Item {
            document: self,
            index,
        })
    }
    /// One source item by its zero-based snapshot-local identity.
    #[must_use]
    pub fn item(&self, index: usize) -> Option<Item<'_>> {
        (index < self.items.len()).then_some(Item {
            document: self,
            index,
        })
    }
    /// Valid declarations in source order, including duplicates and bare keys.
    pub fn entries(&self) -> impl DoubleEndedIterator<Item = Entry<'_>> + ExactSizeIterator {
        (0..self.entries.len()).map(|index| Entry {
            document: self,
            index,
        })
    }
    /// One declaration by its zero-based snapshot-local identity.
    #[must_use]
    pub fn entry(&self, index: usize) -> Option<Entry<'_>> {
        (index < self.entries.len()).then_some(Entry {
            document: self,
            index,
        })
    }
    /// Every occurrence of a key in source order.
    pub fn get_all<'doc, 'key>(
        &'doc self,
        key: &'key str,
    ) -> impl DoubleEndedIterator<Item = Entry<'doc>> + 'key
    where
        'doc: 'key,
    {
        self.entries().filter(move |entry| entry.key() == key)
    }
    /// The last declaration of a key, retaining its bare/empty/value state.
    #[must_use]
    pub fn get_entry(&self, key: &str) -> Option<Entry<'_>> {
        self.entries().rev().find(|entry| entry.key() == key)
    }
    /// The last assigned literal value. A final bare declaration returns `None`.
    #[must_use]
    pub fn get(&self, key: &str) -> Option<&str> {
        self.get_entry(key).and_then(Entry::value)
    }
    /// Select a unique declaration without guessing between duplicate occurrences.
    ///
    /// # Errors
    /// Returns [`EditError::Missing`] or [`EditError::Duplicate`].
    pub fn unique(&self, key: &str) -> Result<Entry<'_>, EditError> {
        let mut entries = self.entries().filter(|entry| entry.key() == key);
        let first = entries.next().ok_or(EditError::Missing)?;
        let remaining = entries.count();
        if remaining == 0 {
            Ok(first)
        } else {
            Err(EditError::Duplicate(remaining + 1))
        }
    }
    /// Whether the input begins with one retained UTF-8 BOM.
    #[must_use]
    pub const fn has_bom(&self) -> bool {
        self.bom
    }
    /// The BOM byte range, when present.
    #[must_use]
    pub fn bom_span(&self) -> Option<Range<usize>> {
        self.bom.then_some(0..3)
    }
    /// Whether the source ends in LF, CRLF or lone CR.
    #[must_use]
    pub fn has_final_newline(&self) -> bool {
        self.source.ends_with(['\n', '\r'])
    }
    /// Build an explicit source index without imposing an index allocation on parsing.
    #[must_use]
    pub fn line_index(&self) -> LineIndex<'_> {
        LineIndex::new(self.source())
    }
    /// Retain all metadata and consume owned source, copying borrowed source only here.
    #[must_use]
    pub fn into_owned(self) -> Document<'static> {
        Document {
            source: Cow::Owned(self.source.into_owned()),
            items: self.items,
            entries: self.entries,
            bom: self.bom,
        }
    }
    /// The dominant source line ending, or LF for a document without endings.
    pub(crate) fn preferred_ending(&self) -> &'static str {
        let mut counts = [0usize; 3];
        let bytes = self.source.as_bytes();
        let mut at = 0;
        while at < bytes.len() {
            match bytes[at] {
                b'\r' if bytes.get(at + 1) == Some(&b'\n') => {
                    counts[1] += 1;
                    at += 1;
                }
                b'\r' => counts[2] += 1,
                b'\n' => counts[0] += 1,
                _ => {}
            }
            at += 1;
        }
        if counts[1] > counts[0] && counts[1] >= counts[2] {
            "\r\n"
        } else if counts[2] > counts[0] && counts[2] > counts[1] {
            "\r"
        } else {
            "\n"
        }
    }
}

impl fmt::Display for Document<'_> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str(self.source())
    }
}

/// A borrowed view of a declaration; identities belong to this document snapshot.
#[derive(Debug, Clone, Copy)]
pub struct Entry<'doc> {
    pub(crate) document: &'doc Document<'doc>,
    pub(crate) index: usize,
}
impl<'doc> Entry<'doc> {
    fn data(self) -> &'doc EntryData {
        &self.document.entries[self.index]
    }
    /// Zero-based declaration identity for explicit native edits on this snapshot.
    #[must_use]
    pub const fn id(self) -> usize {
        self.index
    }
    /// The source item containing this declaration.
    #[must_use]
    pub fn item_id(self) -> usize {
        self.data().item
    }
    /// The original key spelling, borrowed without copying.
    #[must_use]
    pub fn key(self) -> &'doc str {
        &self.document.source[self.data().tokens.key.clone()]
    }
    /// Literal decoded value; `None` is a bare declaration, not an empty string.
    #[must_use]
    pub fn value(self) -> Option<&'doc str> {
        let data = self.data();
        data.tokens.body.as_ref().map(|body| {
            data.decoded
                .as_deref()
                .unwrap_or(&self.document.source[body.clone()])
        })
    }
    /// Exact original token, including quotes, or `None` for a bare declaration.
    #[must_use]
    pub fn raw_value(self) -> Option<&'doc str> {
        self.data()
            .tokens
            .value
            .as_ref()
            .map(|span| &self.document.source[span.clone()])
    }
    /// How the assigned value is quoted.
    #[must_use]
    pub fn quote(self) -> Quote {
        self.data().quote
    }
    /// Whether this declaration has the export prefix.
    #[must_use]
    pub fn exported(self) -> bool {
        self.data().tokens.export.is_some()
    }
    /// Bare/empty/non-empty state, without implicit environment interpretation.
    #[must_use]
    pub fn state(self) -> AssignmentState {
        self.data().state
    }
    /// Explicitly one-based physical line of the key.
    #[must_use]
    pub fn line(self) -> usize {
        self.data().line
    }
    /// Whole statement, including its final line ending, excluding the BOM prelude.
    #[must_use]
    pub fn line_span(self) -> Range<usize> {
        self.document.items[self.item_id()].span.clone()
    }
    /// Original key byte range.
    #[must_use]
    pub fn key_span(self) -> Range<usize> {
        self.data().tokens.key.clone()
    }
    /// Original value token byte range, or `None` for bare declarations.
    #[must_use]
    pub fn value_span(self) -> Option<Range<usize>> {
        self.data().tokens.value.clone()
    }
    /// All raw token metadata.
    #[must_use]
    pub fn tokens(self) -> &'doc EntryTokens {
        &self.data().tokens
    }
    /// An inline comment including its marker.
    #[must_use]
    pub fn inline_comment(self) -> Option<&'doc str> {
        self.data()
            .tokens
            .inline_comment
            .as_ref()
            .map(|span| &self.document.source[span.clone()])
    }
    /// Map a decoded-value byte boundary back into original source bytes.
    ///
    /// Lookup is logarithmic in the number of decoded escape segments.
    ///
    /// # Errors
    /// Rejects absent values, out-of-range offsets and interior UTF-8 boundaries.
    pub fn decoded_offset_to_raw(self, offset: usize) -> Result<usize, PositionError> {
        let value = self.value().ok_or(PositionError::OutOfBounds)?;
        if offset > value.len() {
            return Err(PositionError::OutOfBounds);
        }
        if !value.is_char_boundary(offset) {
            return Err(PositionError::InvalidUtf8Boundary);
        }
        let data = self.data();
        let body = data
            .tokens
            .body
            .as_ref()
            .ok_or(PositionError::OutOfBounds)?;
        let count = data
            .map
            .partition_point(|segment| segment.decoded.start <= offset);
        let Some(index) = count.checked_sub(1) else {
            return Ok(body.start + offset);
        };
        let segment = &data.map[index];
        if offset == segment.decoded.start {
            return Ok(segment.raw.start);
        }
        if offset < segment.decoded.end {
            return Err(PositionError::InvalidUtf8Boundary);
        }
        Ok(segment.raw.end + offset - segment.decoded.end)
    }
    /// Map a decoded-value byte range to its exact original source region.
    ///
    /// # Errors
    /// Rejects reversed ranges and invalid decoded boundaries.
    pub fn decoded_span_to_raw(self, span: Range<usize>) -> Result<Range<usize>, PositionError> {
        if span.start > span.end {
            return Err(PositionError::OutOfBounds);
        }
        Ok(self.decoded_offset_to_raw(span.start)?..self.decoded_offset_to_raw(span.end)?)
    }
}

/// A borrowed view of a raw source item.
#[derive(Debug, Clone, Copy)]
pub struct Item<'doc> {
    pub(crate) document: &'doc Document<'doc>,
    pub(crate) index: usize,
}
impl<'doc> Item<'doc> {
    fn data(self) -> &'doc ItemData {
        &self.document.items[self.index]
    }
    /// Zero-based identity, valid only for this document snapshot.
    #[must_use]
    pub const fn id(self) -> usize {
        self.index
    }
    /// The item's syntax classification.
    #[must_use]
    pub fn kind(self) -> ItemKind {
        self.data().kind
    }
    /// Complete raw byte range, including its final line ending.
    #[must_use]
    pub fn span(self) -> Range<usize> {
        self.data().span.clone()
    }
    /// Original source text, without normalization.
    #[must_use]
    pub fn raw(self) -> &'doc str {
        &self.document.source[self.span()]
    }
    /// The final physical line ending of the item.
    #[must_use]
    pub fn line_ending(self) -> LineEnding {
        self.data().ending
    }
    /// Item bytes excluding the final line ending.
    #[must_use]
    pub fn content_span(self) -> Range<usize> {
        let span = self.span();
        span.start..span.end - self.line_ending().as_str().len()
    }
    /// Declaration view when this is an entry item.
    #[must_use]
    pub fn entry(self) -> Option<Entry<'doc>> {
        self.data().entry.map(|index| Entry {
            document: self.document,
            index,
        })
    }
    /// Comment body after `#`, preserving its spaces.
    #[must_use]
    pub fn comment_text(self) -> Option<&'doc str> {
        self.data()
            .comment
            .as_ref()
            .map(|span| &self.document.source[span.clone()])
    }
    /// The error explaining an invalid statement, if this item is invalid.
    #[must_use]
    pub fn diagnostic(self) -> Option<&'doc Diagnostic> {
        self.data().invalid.as_ref()
    }
    /// Stable invalid-statement identity, convenient for source-preserving checks.
    #[must_use]
    pub fn invalid_code(self) -> Option<DiagnosticCode> {
        self.diagnostic().map(Diagnostic::code)
    }
}