astmap-core 0.0.1

// Symbol-level structural diff across git refs.
// Compares parsed symbols from old git blobs against current DB symbols.

use std::collections::HashMap;
use std::path::Path;

use serde::Serialize;
use tracing::warn;

use crate::error::DiffError;
use crate::model::{ExtractedSymbol, FileChangeStatus, ImpactEntry, SymbolKind, SymbolWithParent};
use crate::port::{DiffStore, LanguageRegistry, VcsProvider};

#[derive(Debug, Serialize)]
pub struct SinceResult {
    pub reference: String,
    pub commit_count: usize,
    pub added: Vec<SymbolChange>,
    pub modified: Vec<SymbolChange>,
    pub removed: Vec<SymbolChange>,
    pub downstream_impacts: Vec<ImpactEntry>,
    pub summary: SinceSummary,
}

#[derive(Debug, Serialize)]
pub struct SymbolChange {
    pub name: String,
    pub kind: SymbolKind,
    pub file: String,
    pub line: u32,
    pub parent_name: Option<String>,
    pub old_signature: Option<String>,
    pub new_signature: Option<String>,
}

#[derive(Debug, Serialize)]
pub struct SinceSummary {
    pub added_count: usize,
    pub modified_count: usize,
    pub removed_count: usize,
    pub impact_count: usize,
    pub files_changed: usize,
}

/// Key for matching symbols across git refs: (name, kind, parent_name).
#[derive(Hash, Eq, PartialEq)]
struct SymbolKey {
    name: String,
    kind: SymbolKind,
    parent_name: Option<String>,
}

/// Resolve parent_index in ExtractedSymbol to parent name string.
fn resolve_parent_name(symbols: &[ExtractedSymbol], sym: &ExtractedSymbol) -> Option<String> {
    sym.parent_index
        .and_then(|idx| symbols.get(idx).map(|p| p.name.clone()))
}

/// Max changed symbols per file before skipping per-symbol impact analysis.
const BUDGET_GUARD_THRESHOLD: usize = 5;

/// Show structural changes (added/removed/modified symbols) since a git reference.
///
/// Expects the caller to have run a scan first to ensure the DB matches the current working tree.
/// Parses old file content from git history and compares against current DB symbols.
pub fn since_against_ref(
    vcs: &dyn VcsProvider,
    reference: &str,
    db: &dyn DiffStore,
    impact_depth: i64,
    supported_ext: &[&str],
    lang: &dyn LanguageRegistry,
) -> Result<SinceResult, DiffError> {
    // Phase 1: get changes and commit count from VCS
    let vcs_changes = vcs.changes_between_refs(reference, "HEAD")?;
    let commit_count = vcs.commit_count(reference, "HEAD")?;

    // Phase 2: filter by supported extensions and process deltas
    let (mut added, mut modified, mut removed, mut modified_sym_ids) =
        (Vec::new(), Vec::new(), Vec::new(), Vec::new());

    for change in &vcs_changes {
        // Filter by supported extensions
        let primary_path = if change.status == FileChangeStatus::Deleted {
            change.old_path.as_deref().unwrap_or(&change.path)
        } else {
            &change.path
        };
        let is_supported = Path::new(primary_path)
            .extension()
            .and_then(|e| e.to_str())
            .is_some_and(|ext| supported_ext.contains(&ext));
        if !is_supported {
            continue;
        }

        match change.status {
            FileChangeStatus::Added => {
                let current = db.all_symbols_for_file(&change.path).unwrap_or_default();
                for sym in current {
                    added.push(symbol_change_from_current(sym));
                }
            }
            FileChangeStatus::Deleted => {
                let old_path = change.old_path.as_deref().unwrap_or(&change.path);
                let Some(old_symbols) = parse_old_blob(vcs, reference, old_path, lang) else {
                    warn!("skipping unparseable deleted file: {}", old_path);
                    continue;
                };
                for sym in &old_symbols {
                    removed.push(symbol_change_from_old(sym, &old_symbols, old_path));
                }
            }
            FileChangeStatus::Modified | FileChangeStatus::Renamed => {
                let old_path = change.old_path.as_deref().unwrap_or(&change.path);
                let Some(old_symbols) = parse_old_blob(vcs, reference, old_path, lang) else {
                    warn!("skipping unparseable file: {}", old_path);
                    continue;
                };
                let current = db.all_symbols_for_file(&change.path).unwrap_or_default();

                let (file_added, file_modified, file_removed, file_mod_ids) =
                    compare_symbols(&old_symbols, &current, &change.path);
                added.extend(file_added);
                modified.extend(file_modified);
                removed.extend(file_removed);
                modified_sym_ids.extend(file_mod_ids);
            }
        }
    }

    // Phase 3: impact analysis for modified symbols
    let mut downstream_impacts = Vec::new();
    let mut seen_ids = std::collections::HashSet::new();
    for sym_id in &modified_sym_ids {
        seen_ids.insert(*sym_id);
    }
    for sym_id in &modified_sym_ids {
        if let Ok(entries) = db.impact_analysis(*sym_id, impact_depth) {
            for entry in entries {
                if seen_ids.insert(entry.symbol_id) {
                    downstream_impacts.push(entry);
                }
            }
        }
    }

    // Count files that passed the extension filter
    let files_changed = vcs_changes
        .iter()
        .filter(|c| {
            let primary_path = if c.status == FileChangeStatus::Deleted {
                c.old_path.as_deref().unwrap_or(&c.path)
            } else {
                &c.path
            };
            Path::new(primary_path)
                .extension()
                .and_then(|e| e.to_str())
                .is_some_and(|ext| supported_ext.contains(&ext))
        })
        .count();

    let summary = SinceSummary {
        added_count: added.len(),
        modified_count: modified.len(),
        removed_count: removed.len(),
        impact_count: downstream_impacts.len(),
        files_changed,
    };

    Ok(SinceResult {
        reference: reference.to_string(),
        commit_count,
        added,
        modified,
        removed,
        downstream_impacts,
        summary,
    })
}

/// Build a SymbolChange from a current DB symbol (added case).
fn symbol_change_from_current(sym: SymbolWithParent) -> SymbolChange {
    SymbolChange {
        name: sym.name,
        kind: sym.kind,
        file: sym.file_path,
        line: sym.start_line as u32,
        parent_name: sym.parent_name,
        old_signature: None,
        new_signature: sym.signature,
    }
}

/// Build a SymbolChange from an old parsed symbol (removed case).
fn symbol_change_from_old(
    sym: &ExtractedSymbol,
    all_old: &[ExtractedSymbol],
    file_path: &str,
) -> SymbolChange {
    SymbolChange {
        name: sym.name.clone(),
        kind: sym.kind,
        file: file_path.to_string(),
        line: sym.start_line as u32,
        parent_name: resolve_parent_name(all_old, sym),
        old_signature: sym.signature.clone(),
        new_signature: None,
    }
}

/// Parse old file content from a git ref and extract symbols with tree-sitter.
/// Returns `None` on failure (unsupported language, missing blob, binary content)
/// so callers can distinguish "parse failed" from "file has no symbols".
fn parse_old_blob(
    vcs: &dyn VcsProvider,
    reference: &str,
    file_path: &str,
    lang: &dyn LanguageRegistry,
) -> Option<Vec<ExtractedSymbol>> {
    let ext = Path::new(file_path).extension().and_then(|e| e.to_str());
    let parser = match ext.and_then(|e| lang.parser_for(e)) {
        Some(p) => p,
        None => {
            warn!("no parser for old file: {}", file_path);
            return None;
        }
    };

    let source = match vcs.read_file_at_ref(file_path, reference) {
        Ok(Some(s)) => s,
        Ok(None) => {
            warn!("old blob not found or binary for {}", file_path);
            return None;
        }
        Err(e) => {
            warn!("failed to read old blob for {}: {}", file_path, e);
            return None;
        }
    };

    let result = parser.parse(&source, Path::new(file_path));
    Some(result.symbols)
}

/// Compare old (git blob parsed) symbols against current (DB) symbols for one file.
/// Uses a multimap to handle duplicate symbol names (e.g. overloaded methods).
/// Returns (added, modified, removed, modified_sym_ids).
fn compare_symbols(
    old_symbols: &[ExtractedSymbol],
    current_symbols: &[SymbolWithParent],
    file_path: &str,
) -> (
    Vec<SymbolChange>,
    Vec<SymbolChange>,
    Vec<SymbolChange>,
    Vec<i64>,
) {
    // Build multimaps: key -> Vec<symbol> (preserves insertion order = file order)
    let mut old_map: HashMap<SymbolKey, Vec<&ExtractedSymbol>> = HashMap::new();
    for sym in old_symbols {
        let key = SymbolKey {
            name: sym.name.clone(),
            kind: sym.kind,
            parent_name: resolve_parent_name(old_symbols, sym),
        };
        old_map.entry(key).or_default().push(sym);
    }

    let mut current_map: HashMap<SymbolKey, Vec<&SymbolWithParent>> = HashMap::new();
    for sym in current_symbols {
        let key = SymbolKey {
            name: sym.name.clone(),
            kind: sym.kind,
            parent_name: sym.parent_name.clone(),
        };
        current_map.entry(key).or_default().push(sym);
    }

    let mut added_out = Vec::new();
    let mut modified_out = Vec::new();
    let mut removed_out = Vec::new();
    let mut modified_ids = Vec::new();

    // For each key in current: pair with old by position, extras are "added"
    for (key, cur_syms) in &current_map {
        if let Some(old_syms) = old_map.get(key) {
            let paired = old_syms.len().min(cur_syms.len());
            for i in 0..paired {
                if old_syms[i].signature != cur_syms[i].signature {
                    modified_out.push(SymbolChange {
                        name: cur_syms[i].name.clone(),
                        kind: cur_syms[i].kind,
                        file: file_path.to_string(),
                        line: cur_syms[i].start_line as u32,
                        parent_name: cur_syms[i].parent_name.clone(),
                        old_signature: old_syms[i].signature.clone(),
                        new_signature: cur_syms[i].signature.clone(),
                    });
                    modified_ids.push(cur_syms[i].id);
                }
            }
            for cur in cur_syms.iter().skip(paired) {
                added_out.push(SymbolChange {
                    name: cur.name.clone(),
                    kind: cur.kind,
                    file: file_path.to_string(),
                    line: cur.start_line as u32,
                    parent_name: cur.parent_name.clone(),
                    old_signature: None,
                    new_signature: cur.signature.clone(),
                });
            }
        } else {
            for cur in cur_syms {
                added_out.push(SymbolChange {
                    name: cur.name.clone(),
                    kind: cur.kind,
                    file: file_path.to_string(),
                    line: cur.start_line as u32,
                    parent_name: cur.parent_name.clone(),
                    old_signature: None,
                    new_signature: cur.signature.clone(),
                });
            }
        }
    }

    // For each key in old: extras beyond paired count are "removed"
    for (key, old_syms) in &old_map {
        let paired = current_map
            .get(key)
            .map_or(0, |c| c.len().min(old_syms.len()));
        for old in old_syms.iter().skip(paired) {
            removed_out.push(symbol_change_from_old(old, old_symbols, file_path));
        }
    }

    // Budget guard: skip impact analysis if too many changes in this file
    let total_changes = added_out.len() + modified_out.len() + removed_out.len();
    if total_changes > BUDGET_GUARD_THRESHOLD {
        modified_ids.clear();
    }

    (added_out, modified_out, removed_out, modified_ids)
}

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

    // --- Pure function unit tests for compare_symbols ---

    fn make_old_sym(
        name: &str,
        kind: SymbolKind,
        sig: Option<&str>,
        parent_index: Option<usize>,
    ) -> ExtractedSymbol {
        ExtractedSymbol {
            name: name.to_string(),
            kind,
            signature: sig.map(|s| s.to_string()),
            start_line: 1,
            end_line: 5,
            start_byte: 0,
            end_byte: 100,
            parent_index,
        }
    }

    fn make_cur_sym(
        id: i64,
        name: &str,
        kind: SymbolKind,
        sig: Option<&str>,
        parent_name: Option<&str>,
    ) -> SymbolWithParent {
        SymbolWithParent {
            id,
            name: name.to_string(),
            kind,
            file_path: "src/lib.rs".to_string(),
            start_line: 1,
            end_line: 5,
            signature: sig.map(|s| s.to_string()),
            parent_name: parent_name.map(|s| s.to_string()),
        }
    }

    #[test]
    fn test_compare_symbols_added_new_key() {
        let old_symbols = vec![];
        let current_symbols = vec![make_cur_sym(
            1,
            "new_fn",
            SymbolKind::Function,
            Some("fn new_fn()"),
            None,
        )];
        let (added, modified, removed, _) =
            compare_symbols(&old_symbols, &current_symbols, "src/lib.rs");
        assert_eq!(added.len(), 1);
        assert_eq!(added[0].name, "new_fn");
        assert!(modified.is_empty());
        assert!(removed.is_empty());
    }

    #[test]
    fn test_compare_symbols_removed_key() {
        let old_symbols = vec![make_old_sym(
            "old_fn",
            SymbolKind::Function,
            Some("fn old_fn()"),
            None,
        )];
        let current_symbols = vec![];
        let (added, modified, removed, _) =
            compare_symbols(&old_symbols, &current_symbols, "src/lib.rs");
        assert!(added.is_empty());
        assert!(modified.is_empty());
        assert_eq!(removed.len(), 1);
        assert_eq!(removed[0].name, "old_fn");
    }

    #[test]
    fn test_compare_symbols_modified_signature() {
        let old_symbols = vec![make_old_sym(
            "foo",
            SymbolKind::Function,
            Some("fn foo()"),
            None,
        )];
        let current_symbols = vec![make_cur_sym(
            1,
            "foo",
            SymbolKind::Function,
            Some("fn foo(x: i32)"),
            None,
        )];
        let (added, modified, removed, mod_ids) =
            compare_symbols(&old_symbols, &current_symbols, "src/lib.rs");
        assert!(added.is_empty());
        assert_eq!(modified.len(), 1);
        assert_eq!(modified[0].name, "foo");
        assert_eq!(modified[0].old_signature.as_deref(), Some("fn foo()"));
        assert_eq!(modified[0].new_signature.as_deref(), Some("fn foo(x: i32)"));
        assert_eq!(mod_ids, vec![1]);
        assert!(removed.is_empty());
    }

    #[test]
    fn test_compare_symbols_unchanged_signature() {
        let old_symbols = vec![make_old_sym(
            "foo",
            SymbolKind::Function,
            Some("fn foo()"),
            None,
        )];
        let current_symbols = vec![make_cur_sym(
            1,
            "foo",
            SymbolKind::Function,
            Some("fn foo()"),
            None,
        )];
        let (added, modified, removed, _) =
            compare_symbols(&old_symbols, &current_symbols, "src/lib.rs");
        assert!(added.is_empty());
        assert!(modified.is_empty());
        assert!(removed.is_empty());
    }

    #[test]
    fn test_compare_symbols_extra_current_beyond_paired() {
        let old_symbols = vec![make_old_sym(
            "foo",
            SymbolKind::Function,
            Some("fn foo()"),
            None,
        )];
        let current_symbols = vec![
            make_cur_sym(1, "foo", SymbolKind::Function, Some("fn foo()"), None),
            make_cur_sym(2, "foo", SymbolKind::Function, Some("fn foo(x: i32)"), None),
        ];
        let (added, modified, removed, _) =
            compare_symbols(&old_symbols, &current_symbols, "src/lib.rs");
        assert_eq!(added.len(), 1, "extra current symbol should be added");
        assert_eq!(added[0].new_signature.as_deref(), Some("fn foo(x: i32)"));
        assert!(modified.is_empty());
        assert!(removed.is_empty());
    }

    #[test]
    fn test_compare_symbols_extra_old_beyond_paired() {
        let old_symbols = vec![
            make_old_sym("foo", SymbolKind::Function, Some("fn foo()"), None),
            make_old_sym("foo", SymbolKind::Function, Some("fn foo(x: i32)"), None),
        ];
        let current_symbols = vec![make_cur_sym(
            1,
            "foo",
            SymbolKind::Function,
            Some("fn foo()"),
            None,
        )];
        let (added, modified, removed, _) =
            compare_symbols(&old_symbols, &current_symbols, "src/lib.rs");
        assert!(added.is_empty());
        assert!(modified.is_empty());
        assert_eq!(removed.len(), 1, "extra old symbol should be removed");
        assert_eq!(removed[0].old_signature.as_deref(), Some("fn foo(x: i32)"));
    }

    #[test]
    fn test_compare_symbols_budget_guard_clears_modified_ids() {
        let old_symbols: Vec<ExtractedSymbol> = (0..6)
            .map(|i| {
                make_old_sym(
                    &format!("fn_{}", i),
                    SymbolKind::Function,
                    Some(&format!("fn fn_{}()", i)),
                    None,
                )
            })
            .collect();
        let current_symbols: Vec<SymbolWithParent> = Vec::new();

        let (_, _, removed, mod_ids) =
            compare_symbols(&old_symbols, &current_symbols, "src/lib.rs");
        assert_eq!(removed.len(), 6);
        assert!(
            mod_ids.is_empty(),
            "budget guard should clear modified_ids when total_changes > {}",
            BUDGET_GUARD_THRESHOLD
        );
    }

    #[test]
    fn test_resolve_parent_name_with_parent() {
        let symbols = vec![
            make_old_sym("MyClass", SymbolKind::Class, None, None),
            make_old_sym("method", SymbolKind::Method, None, Some(0)),
        ];
        let parent = resolve_parent_name(&symbols, &symbols[1]);
        assert_eq!(parent, Some("MyClass".to_string()));
    }

    #[test]
    fn test_resolve_parent_name_without_parent() {
        let symbols = vec![make_old_sym("top_fn", SymbolKind::Function, None, None)];
        let parent = resolve_parent_name(&symbols, &symbols[0]);
        assert_eq!(parent, None);
    }

    #[test]
    fn test_resolve_parent_name_out_of_bounds() {
        let symbols = vec![make_old_sym("orphan", SymbolKind::Method, None, Some(99))];
        let parent = resolve_parent_name(&symbols, &symbols[0]);
        assert_eq!(
            parent, None,
            "out-of-bounds parent_index should return None"
        );
    }

    #[test]
    fn test_symbol_change_from_current_fields() {
        let sym = SymbolWithParent {
            id: 42,
            name: "my_fn".to_string(),
            kind: SymbolKind::Function,
            file_path: "src/lib.rs".to_string(),
            start_line: 10,
            end_line: 20,
            signature: Some("fn my_fn(x: i32)".to_string()),
            parent_name: Some("MyStruct".to_string()),
        };
        let change = symbol_change_from_current(sym);
        assert_eq!(change.name, "my_fn");
        assert_eq!(change.kind, SymbolKind::Function);
        assert_eq!(change.file, "src/lib.rs");
        assert_eq!(change.line, 10);
        assert_eq!(change.parent_name, Some("MyStruct".to_string()));
        assert!(change.old_signature.is_none());
        assert_eq!(change.new_signature, Some("fn my_fn(x: i32)".to_string()));
    }

    #[test]
    fn test_symbol_change_from_old_fields() {
        let symbols = vec![
            make_old_sym("Parent", SymbolKind::Class, None, None),
            ExtractedSymbol {
                name: "child".to_string(),
                kind: SymbolKind::Method,
                signature: Some("def child(self)".to_string()),
                start_line: 5,
                end_line: 10,
                start_byte: 50,
                end_byte: 200,
                parent_index: Some(0),
            },
        ];
        let change = symbol_change_from_old(&symbols[1], &symbols, "src/app.py");
        assert_eq!(change.name, "child");
        assert_eq!(change.kind, SymbolKind::Method);
        assert_eq!(change.file, "src/app.py");
        assert_eq!(change.line, 5);
        assert_eq!(change.parent_name, Some("Parent".to_string()));
        assert_eq!(change.old_signature, Some("def child(self)".to_string()));
        assert!(change.new_signature.is_none());
    }
}