//! `kebab-parse-code::javascript` — tree-sitter JavaScript / JSX AST
//! extractor (P10-1B Task K).
//!
//! Implements [`kebab_core::Extractor`] for [`MediaType::Code("javascript")`].
//! Walks the tree-sitter parse tree (single grammar
//! [`tree_sitter_javascript::LANGUAGE`] — the JS grammar handles `.jsx`
//! as well, no second grammar needed) and emits one [`Block::Code`] per
//! top-level AST semantic unit (free fn, class, each method,
//! recursively per nested class), each carrying [`SourceSpan::Code`]
//! with the unit's dotted symbol path prefixed by
//! [`module_path_for_tsjs`].
//!
//! Glue declarations (`import_statement`, bare `export_statement`
//! re-exports, `lexical_declaration` / `variable_declaration` at the
//! module level, etc.) collapse into one grouped `<top-level>` (or
//! `<module>`) unit.
//!
//! `export_statement` is unwrapped: an `export function|class` is
//! treated as the inner declaration arm but the unit's line range
//! comes from the OUTER `export_statement` so the `export ` prefix is
//! folded in. `export default function () {}` / `export default class
//! {}` (no `name` field) emits `default` as the symbol name.
//!
//! Differs from `typescript.rs` only by: single-grammar (no
//! TS/TSX selection) and no `interface_declaration` /
//! `type_alias_declaration` / `enum_declaration` arms (TS-only). All
//! other walker behavior (export unwrap with `value`-field quirk for
//! default-exported anonymous function/class, class-body method walk,
//! glue flush, post-pass `<module>` → `<top-level>` rewrite) is
//! identical.
//!
//! Scope follows 1A-2 / 1B Task K: AST unit extraction + dotted symbol
//! paths + line ranges. Per design §3.4 / §9.1 / §9 versioning.

use anyhow::Result;
use kebab_core::{
    Block, CanonicalDocument, CodeBlock, CommonBlock, Extractor, Lang, MediaType, Metadata,
    ParserVersion, Provenance, ProvenanceEvent, ProvenanceKind, SourceSpan, SourceType, TrustLevel,
    id_for_block, id_for_doc,
};
use serde_json::Map;
use time::OffsetDateTime;

use crate::scaffold::{filename_from_workspace_path, join_symbol, strip_extension};

pub const PARSER_VERSION: &str = "code-js-v1";

/// JavaScript / JSX AST extractor. Per-unit blocks via
/// tree-sitter-javascript 0.25 (single `LANGUAGE` `LanguageFn` — the
/// JS grammar covers `.jsx` natively, no second grammar) parsed by
/// tree-sitter 0.26.
pub struct JavascriptAstExtractor;

impl JavascriptAstExtractor {
    pub fn new() -> Self {
        Self
    }
}

impl Default for JavascriptAstExtractor {
    fn default() -> Self {
        Self::new()
    }
}

impl Extractor for JavascriptAstExtractor {
    fn supports(&self, m: &MediaType) -> bool {
        matches!(m, MediaType::Code(l) if l == "javascript")
    }

    fn parser_version(&self) -> ParserVersion {
        ParserVersion(PARSER_VERSION.to_string())
    }

    fn extract(
        &self,
        ctx: &kebab_core::ExtractContext<'_>,
        bytes: &[u8],
    ) -> Result<CanonicalDocument> {
        let asset = ctx.asset;
        if !self.supports(&asset.media_type) {
            anyhow::bail!(
                "kebab-parse-code: unsupported media_type for JavascriptAstExtractor: {:?}",
                asset.media_type
            );
        }

        let parser_version = self.parser_version();
        let doc_id = id_for_doc(&asset.workspace_path, &asset.asset_id, &parser_version);

        let source = String::from_utf8(bytes.to_vec()).map_err(|e| {
            anyhow::anyhow!("kebab-parse-code: JavaScript source is not valid UTF-8: {e}")
        })?;

        let mod_prefix = crate::lang::module_path_for_tsjs(&asset.workspace_path.0);
        let language: tree_sitter::Language = tree_sitter_javascript::LANGUAGE.into();
        let blocks = build_blocks(&source, &doc_id, &mod_prefix, language)?;
        let unit_count = blocks.len() as u32;

        let now = OffsetDateTime::now_utc();
        let mut events: Vec<ProvenanceEvent> = Vec::with_capacity(2);
        events.push(ProvenanceEvent {
            at: asset.discovered_at,
            agent: "kb-source-fs".to_string(),
            kind: ProvenanceKind::Discovered,
            note: None,
        });
        events.push(ProvenanceEvent {
            at: now,
            agent: "kb-parse-code".to_string(),
            kind: ProvenanceKind::Parsed,
            note: Some(format!(
                "parser_version={}; unit_count={}",
                parser_version.0, unit_count
            )),
        });

        let title = {
            let fname = filename_from_workspace_path(&asset.workspace_path.0);
            strip_extension(&fname)
        };

        // Resolve the file's absolute path for repo detection. If the
        // source URI carries a relative path, anchor it at the workspace
        // root so the `.git/` walk-up starts from the right place.
        let abs_path = match &asset.source_uri {
            kebab_core::SourceUri::File(p) => {
                if p.is_absolute() {
                    p.clone()
                } else {
                    ctx.workspace_root.join(p)
                }
            }
            kebab_core::SourceUri::Kb(_) => ctx.workspace_root.to_path_buf(),
        };
        let (repo, git_branch, git_commit) = match crate::repo::detect_repo(&abs_path) {
            Some(r) => (Some(r.name), r.branch, r.commit),
            None => (None, None, None),
        };

        let metadata = Metadata {
            aliases: Vec::new(),
            tags: Vec::new(),
            created_at: asset.discovered_at,
            updated_at: asset.discovered_at,
            source_type: SourceType::Note,
            trust_level: TrustLevel::Primary,
            user_id_alias: None,
            user: Map::new(),
            repo,
            git_branch,
            git_commit,
            code_lang: Some("javascript".to_string()),
        };

        tracing::debug!(
            target: "kebab-parse-code",
            "extracted JavaScript doc_id={} workspace_path={} units={}",
            doc_id.0,
            asset.workspace_path.0,
            unit_count
        );

        Ok(CanonicalDocument {
            doc_id,
            source_asset_id: asset.asset_id.clone(),
            workspace_path: asset.workspace_path.clone(),
            title,
            lang: Lang("und".to_string()),
            blocks,
            metadata,
            provenance: Provenance { events },
            parser_version,
            schema_version: 1,
            doc_version: 1,
            last_chunker_version: None,
            last_embedding_version: None,
        })
    }
}

fn build_blocks(
    source: &str,
    doc_id: &kebab_core::DocumentId,
    mod_prefix: &str,
    language: tree_sitter::Language,
) -> anyhow::Result<Vec<kebab_core::Block>> {
    let mut parser = tree_sitter::Parser::new();
    parser
        .set_language(&language)
        .map_err(|e| anyhow::anyhow!("set tree-sitter-javascript language: {e}"))?;
    let tree = parser
        .parse(source.as_bytes(), None)
        .ok_or_else(|| anyhow::anyhow!("tree-sitter failed to parse JavaScript source"))?;
    let lines: Vec<&str> = source.split('\n').collect();

    // units: (symbol, line_start, line_end, is_real_semantic_unit).
    // Glue groups are pushed with a sentinel symbol + is_real=false so a
    // post-pass can decide `<module>` vs `<top-level>` (same algorithm
    // as 1A Gap 1 / 1B Python / 1B TS).
    let mut units: Vec<(String, u32, u32, bool)> = Vec::new();
    // (is_module_only_kind 0/1, s, e). `is_module_only_kind` flags
    // `import_statement` and bare re-export `export_statement`s — used by
    // the glue flush to pick `<module>` vs `<top-level>` provisional
    // label (1A's `is_mod_decl` analog).
    let mut glue: Vec<(usize, u32, u32)> = Vec::new();

    /// Walk preceding `comment` siblings to extend the unit's line range
    /// upward, folding leading doc / line comments into the unit.
    fn unit_start(n: &tree_sitter::Node) -> u32 {
        let mut start = n.start_position().row as u32 + 1;
        let mut prev = n.prev_sibling();
        while let Some(p) = prev {
            if p.kind() == "comment" {
                start = p.start_position().row as u32 + 1;
                prev = p.prev_sibling();
            } else {
                break;
            }
        }
        start
    }
    fn name_text<'a>(n: &tree_sitter::Node, src: &'a str) -> Option<&'a str> {
        n.child_by_field_name("name")
            .map(|c| &src[c.start_byte()..c.end_byte()])
    }
    /// Walk a class body, emitting one unit per `method_definition`.
    /// Class names already pushed onto `mod_path` by the caller, so
    /// method symbols come out as `<mod_prefix>.<Class>.<method>`.
    fn walk_class_body(
        body: tree_sitter::Node,
        src: &str,
        mod_prefix: &str,
        mod_path: &[String],
        units: &mut Vec<(String, u32, u32, bool)>,
    ) {
        let mut cur = body.walk();
        for child in body.named_children(&mut cur) {
            if child.kind() == "method_definition" {
                if let Some(name) = name_text(&child, src) {
                    let s = unit_start(&child);
                    let e = child.end_position().row as u32 + 1;
                    let sym = join_symbol(mod_prefix, mod_path, name);
                    units.push((sym, s, e, true));
                }
            }
        }
    }
    fn walk(
        node: tree_sitter::Node,
        src: &str,
        mod_prefix: &str,
        mod_path: &[String],
        units: &mut Vec<(String, u32, u32, bool)>,
        glue: &mut Vec<(usize, u32, u32)>,
    ) {
        let mut cur = node.walk();
        for child in node.named_children(&mut cur) {
            let s = unit_start(&child);
            let e = child.end_position().row as u32 + 1;
            match child.kind() {
                "function_declaration" => {
                    if let Some(name) = name_text(&child, src) {
                        glue.retain(|(_, gs, _)| *gs < s);
                        flush_glue(glue, units, mod_prefix, mod_path);
                        let sym = join_symbol(mod_prefix, mod_path, name);
                        units.push((sym, s, e, true));
                    }
                }
                "class_declaration" => {
                    if let Some(name) = name_text(&child, src) {
                        glue.retain(|(_, gs, _)| *gs < s);
                        flush_glue(glue, units, mod_prefix, mod_path);
                        let sym = join_symbol(mod_prefix, mod_path, name);
                        units.push((sym, s, e, true));
                        if let Some(body) = child.child_by_field_name("body") {
                            let mut np = mod_path.to_vec();
                            np.push(name.to_string());
                            walk_class_body(body, src, mod_prefix, &np, units);
                        }
                    }
                }
                "export_statement" => {
                    // Try field "declaration" first (export class /
                    // function). If absent, fall back to "value" —
                    // `export default function () {}` / `export default
                    // class {}` expose the anonymous function_expression
                    // / class under the `value` field (same grammar
                    // quirk as TS 0.23).
                    let outer_s = s; // includes `export ` prefix line
                    let outer_e = e;
                    if let Some(inner) = child.child_by_field_name("declaration") {
                        let inner_kind = inner.kind();
                        match inner_kind {
                            "function_declaration" | "class_declaration" => {
                                let name_opt = name_text(&inner, src).map(|s| s.to_string());
                                if let Some(name) = name_opt {
                                    glue.retain(|(_, gs, _)| *gs < outer_s);
                                    flush_glue(glue, units, mod_prefix, mod_path);
                                    let sym = join_symbol(mod_prefix, mod_path, &name);
                                    units.push((sym, outer_s, outer_e, true));
                                    if inner_kind == "class_declaration" {
                                        if let Some(body) = inner.child_by_field_name("body") {
                                            let mut np = mod_path.to_vec();
                                            np.push(name);
                                            walk_class_body(body, src, mod_prefix, &np, units);
                                        }
                                    }
                                } else {
                                    // Defensive: `export default` with a
                                    // function_declaration that somehow
                                    // lacks `name`. Emit `default`.
                                    glue.retain(|(_, gs, _)| *gs < outer_s);
                                    flush_glue(glue, units, mod_prefix, mod_path);
                                    let sym = join_symbol(mod_prefix, mod_path, "default");
                                    units.push((sym, outer_s, outer_e, true));
                                }
                            }
                            // `lexical_declaration` etc. wrapped in
                            // export: treat as glue (assigned arrow
                            // fns / consts don't get their own unit).
                            _ => {
                                glue.push((0, s, e));
                            }
                        }
                    } else if let Some(value) = child.child_by_field_name("value") {
                        // `export default <expr>`. We emit a unit only
                        // for the function / class shapes (named or
                        // anonymous); other value shapes are glue.
                        match value.kind() {
                            "function_expression"
                            | "function_declaration"
                            | "class"
                            | "class_declaration" => {
                                let name_opt = name_text(&value, src).map(|s| s.to_string());
                                let leaf =
                                    name_opt.as_deref().unwrap_or("default").to_string();
                                glue.retain(|(_, gs, _)| *gs < outer_s);
                                flush_glue(glue, units, mod_prefix, mod_path);
                                let sym = join_symbol(mod_prefix, mod_path, &leaf);
                                units.push((sym, outer_s, outer_e, true));
                                // Recurse into class body if we have one.
                                if matches!(value.kind(), "class" | "class_declaration") {
                                    if let Some(body) = value.child_by_field_name("body") {
                                        let mut np = mod_path.to_vec();
                                        np.push(leaf);
                                        walk_class_body(body, src, mod_prefix, &np, units);
                                    }
                                }
                            }
                            _ => {
                                glue.push((0, s, e));
                            }
                        }
                    } else {
                        // Bare `export { x };` / `export * from "..."` —
                        // a re-export, glue with module-only flag set
                        // (we have no `declaration` / `value` field for
                        // it).
                        glue.push((1, s, e));
                    }
                }
                "import_statement" => {
                    glue.push((1, s, e));
                }
                "lexical_declaration" | "variable_declaration" => {
                    glue.push((0, s, e));
                }
                _ => {}
            }
        }
        flush_glue(glue, units, mod_prefix, mod_path);
    }
    fn flush_glue(
        glue: &mut Vec<(usize, u32, u32)>,
        units: &mut Vec<(String, u32, u32, bool)>,
        mod_prefix: &str,
        mod_path: &[String],
    ) {
        if glue.is_empty() {
            return;
        }
        let s = glue.iter().map(|(_, a, _)| *a).min().unwrap();
        let e = glue.iter().map(|(_, _, b)| *b).max().unwrap();
        let only_module = glue.iter().all(|(is_mod, _, _)| *is_mod == 1);
        let label = if only_module { "<module>" } else { "<top-level>" };
        units.push((join_symbol(mod_prefix, mod_path, label), s, e, false));
        glue.clear();
    }

    walk(
        tree.root_node(),
        source,
        mod_prefix,
        &[],
        &mut units,
        &mut glue,
    );

    // `<module>` is correct only when the file produced no real unit.
    // Otherwise the import-only group becomes `<top-level>` (same
    // post-pass as 1A Gap 1 / Python / TS).
    let has_real_unit = units.iter().any(|(_, _, _, is_real)| *is_real);
    if has_real_unit {
        for (sym, _, _, is_real) in units.iter_mut() {
            if !*is_real && sym.ends_with("<module>") {
                let pre = &sym[..sym.len() - "<module>".len()];
                *sym = format!("{pre}<top-level>");
            }
        }
    }

    let total_lines = lines.len() as u32;
    let mut blocks = Vec::with_capacity(units.len());
    for (ordinal, (symbol, ls, le, _is_real)) in units.into_iter().enumerate() {
        let line_start = ls.max(1);
        let line_end = le.min(total_lines.max(1));
        let span = SourceSpan::Code {
            line_start,
            line_end,
            symbol: Some(symbol),
            lang: Some("javascript".to_string()),
        };
        let block_id = id_for_block(doc_id, "code", &[], ordinal as u32, &span);
        let code = lines[(line_start as usize - 1)..=(line_end as usize - 1)].join("\n");
        blocks.push(Block::Code(CodeBlock {
            common: CommonBlock {
                block_id,
                heading_path: Vec::new(),
                source_span: span,
            },
            lang: Some("javascript".to_string()),
            code,
        }));
    }
    Ok(blocks)
}

#[cfg(test)]
mod tests {
    use super::*;
    use kebab_core::{Block, MediaType, SourceSpan};

    fn extract_fixture(workspace_path: &str) -> kebab_core::CanonicalDocument {
        let bytes = std::fs::read(
            concat!(env!("CARGO_MANIFEST_DIR"), "/tests/fixtures/sample.js"),
        )
        .unwrap();
        let asset = crate::rust::tests_support::fixed_code_asset(workspace_path, "javascript");
        let cfg = kebab_core::ExtractConfig::default();
        let root = std::path::PathBuf::from("/tmp");
        let ctx = kebab_core::ExtractContext {
            asset: &asset,
            workspace_root: &root,
            config: &cfg,
        };
        JavascriptAstExtractor::new().extract(&ctx, &bytes).unwrap()
    }
    fn symbols(doc: &kebab_core::CanonicalDocument) -> Vec<String> {
        let mut s: Vec<String> = doc
            .blocks
            .iter()
            .filter_map(|b| match b {
                Block::Code(c) => match &c.common.source_span {
                    SourceSpan::Code { symbol, lang, .. } => {
                        assert_eq!(lang.as_deref(), Some("javascript"));
                        symbol.clone()
                    }
                    _ => None,
                },
                _ => None,
            })
            .collect();
        s.sort();
        s
    }
    #[test]
    fn extractor_supports_only_media_code_javascript() {
        let e = JavascriptAstExtractor::new();
        assert!(e.supports(&MediaType::Code("javascript".into())));
        assert!(!e.supports(&MediaType::Code("typescript".into())));
        assert!(!e.supports(&MediaType::Markdown));
    }
    #[test]
    fn js_units_match_design_3_4_symbols() {
        let doc = extract_fixture("src/sample.js");
        let syms = symbols(&doc);
        assert!(syms.iter().any(|s| s == "src/sample.add"), "got {syms:?}");
        assert!(syms.iter().any(|s| s == "src/sample.Retriever"));
        assert!(syms.iter().any(|s| s == "src/sample.Retriever.search"));
        assert!(syms.iter().any(|s| s == "src/sample.Retriever.create"));
        assert!(syms.iter().any(|s| s == "src/sample.default"));
        assert!(syms.iter().any(|s| s == "src/sample.<top-level>"));
    }
    #[test]
    fn jsx_via_js_grammar() {
        // tree-sitter-javascript handles .jsx via the same single grammar.
        let bytes = b"export function App() { return null; }\n";
        let asset = crate::rust::tests_support::fixed_code_asset("src/App.jsx", "javascript");
        let cfg = kebab_core::ExtractConfig::default();
        let root = std::path::PathBuf::from("/tmp");
        let ctx = kebab_core::ExtractContext {
            asset: &asset,
            workspace_root: &root,
            config: &cfg,
        };
        let doc = JavascriptAstExtractor::new().extract(&ctx, bytes).unwrap();
        let syms = symbols(&doc);
        assert!(syms.iter().any(|s| s == "src/App.App"), "got {syms:?}");
    }
    #[test]
    fn deterministic_across_runs() {
        let a = extract_fixture("src/sample.js");
        for _ in 0..30 {
            assert_eq!(extract_fixture("src/sample.js").blocks, a.blocks);
        }
    }

    /// In tree-sitter-javascript, `decorator` is a CHILD of
    /// `method_definition` (stored in the `decorator` field), so
    /// `method_definition.start_row` already covers the decorator line
    /// without any sibling walk. Verify that the emitted unit already
    /// includes the decorator line and line_start is 2 (the @Log() line).
    #[test]
    fn js_class_method_decorator_already_folded_by_grammar() {
        // Line 1 (1-indexed): "class Foo {"
        // Line 2:             "    @Log()"   <- decorator (child of method_definition in JS grammar)
        // Line 3:             "    bar() { return 1; }"
        // Line 4:             "}"
        let bytes = b"class Foo {\n    @Log()\n    bar() { return 1; }\n}\n";
        let asset = crate::rust::tests_support::fixed_code_asset("src/foo.js", "javascript");
        let cfg = kebab_core::ExtractConfig::default();
        let root = std::path::PathBuf::from("/tmp");
        let ctx = kebab_core::ExtractContext {
            asset: &asset,
            workspace_root: &root,
            config: &cfg,
        };
        let doc = JavascriptAstExtractor::new().extract(&ctx, bytes).unwrap();

        let bar_block = doc
            .blocks
            .iter()
            .find_map(|b| match b {
                Block::Code(c) => match &c.common.source_span {
                    SourceSpan::Code { symbol, .. }
                        if symbol.as_deref() == Some("src/foo.Foo.bar") =>
                    {
                        Some(c)
                    }
                    _ => None,
                },
                _ => None,
            })
            .expect("src/foo.Foo.bar block should be present");

        // JS grammar: method_definition.start_row == decorator row, so
        // no sibling walk change needed -- decorator is already included.
        assert!(
            bar_block.code.contains("@Log()"),
            "JS method unit must include decorator (grammar folds it natively); got: {:?}",
            bar_block.code
        );
        match &bar_block.common.source_span {
            SourceSpan::Code { line_start, .. } => {
                assert_eq!(
                    *line_start, 2,
                    "JS line_start must cover the @Log() decorator line (got {line_start})"
                );
            }
            _ => unreachable!(),
        }
    }
}