basemind 0.12.1

//! Helper bodies for the `find_references` / `find_callers` MCP tools.
//!
//! Extracted out of `helpers.rs` so the parent file stays under the 1000-line per-file
//! cap. Both tools share the same `calls_by_callee` range scan; the only difference is
//! `find_callers` resolves a definition first.

use std::ops::Bound;

use rmcp::ErrorData as McpError;
use rmcp::model::CallToolResult;

use super::cursor::Cursor;
use super::helpers::{
    SEARCH_LIMIT_DEFAULT, SEARCH_LIMIT_MAX, json_result, kind_to_str, parse_kind,
};
use super::types::ReferenceHit;

/// Point-lookup a `Call` value in the index by `(path, start_byte)` and return its
/// `(line, column)` as 1-based / 0-based respectively. Falls back to `(0, 0)` when the
/// row/col fields aren't populated (older L2 blobs predating the field's introduction).
pub(super) fn resolve_call_line_col(
    idx: &crate::index::IndexDb,
    rel: &crate::path::RelPath,
    start_byte: u32,
) -> (u32, u32) {
    let key = crate::index::keys::call_by_path(rel, start_byte);
    let value = match idx.calls_by_path.get(key) {
        Ok(Some(v)) => v,
        _ => return (0, 0),
    };
    let call: crate::extract::Call = match rmp_serde::from_slice(&value) {
        Ok(c) => c,
        Err(_) => return (0, 0),
    };
    // `start_row` is 0-based; emit 1-based for line numbers per editor convention.
    (call.start_row + 1, call.start_col)
}

/// Body of the `find_references` MCP tool — pulled out so the `#[tool]` wrapper in
/// `tools.rs` stays small. Takes a snapshot of the IndexDb (cheap clone) so the caller
/// can release the store lock before iterating.
pub(super) fn run_find_references(
    idx: Option<&crate::index::IndexDb>,
    params: super::types::FindReferencesParams,
    cache: &super::MapCache,
) -> Result<CallToolResult, McpError> {
    use super::types::FindReferencesResponse;
    let format = super::toon::ResponseFormat::parse(params.format.as_deref());
    let limit = params
        .limit
        .unwrap_or(SEARCH_LIMIT_DEFAULT)
        .min(SEARCH_LIMIT_MAX) as usize;
    let cursor_bytes = params
        .cursor
        .as_ref()
        .map(|c| c.decode_fjall())
        .transpose()?;
    let scan = scan_calls(idx, cache, &params.name, limit, cursor_bytes.as_deref())?;
    let total = scan.total;
    let total_is_partial = scan.total_is_partial;
    let budgeted = budget_call_page(scan, params.max_tokens);
    super::toon::format_result(
        &FindReferencesResponse {
            name: params.name,
            total,
            total_is_partial,
            budgeted: budgeted.budgeted,
            hits: budgeted.hits,
            next_cursor: budgeted.next_cursor,
        },
        format,
    )
}

/// Body of the `find_callers` MCP tool. Resolves the definition via the in-RAM cache (the
/// same source `outline` uses) for context, then delegates to the same callee-substring scan.
pub(super) fn run_find_callers(
    idx: Option<&crate::index::IndexDb>,
    params: super::types::FindCallersParams,
    cache: &super::MapCache,
) -> Result<CallToolResult, McpError> {
    use super::types::{DefinitionView, FindCallersResponse};
    let limit = params
        .limit
        .unwrap_or(SEARCH_LIMIT_DEFAULT)
        .min(SEARCH_LIMIT_MAX) as usize;
    let kind_filter = params.kind.as_deref().map(parse_kind).transpose()?;
    let definition: Option<DefinitionView> = cache
        .by_path
        .get(&params.path)
        .and_then(|l1| {
            l1.symbols
                .iter()
                .find(|s| s.name == params.name && kind_filter.is_none_or(|k| s.kind == k))
        })
        .map(|sym| DefinitionView {
            path: params.path.clone(),
            name: sym.name.clone(),
            kind: kind_to_str(sym.kind),
            start_row: sym.start_row,
            start_col: sym.start_col,
        });
    let cursor_bytes = params
        .cursor
        .as_ref()
        .map(|c| c.decode_fjall())
        .transpose()?;
    let scan = scan_calls(idx, cache, &params.name, limit, cursor_bytes.as_deref())?;
    let total = scan.total;
    let total_is_partial = scan.total_is_partial;
    let budgeted = budget_call_page(scan, params.max_tokens);
    json_result(&FindCallersResponse {
        definition,
        total,
        total_is_partial,
        budgeted: budgeted.budgeted,
        hits: budgeted.hits,
        next_cursor: budgeted.next_cursor,
    })
}

pub(super) struct CallScanPage {
    pub total: u32,
    pub total_is_partial: bool,
    pub hits: Vec<ReferenceHit>,
    pub next_cursor: Option<Cursor>,
    /// Parallel to `hits`: the Fjall key for each emitted hit. Retained so a token budget can
    /// re-anchor `next_cursor` to the last KEPT hit, not the last scanned one.
    pub hit_keys: Vec<Vec<u8>>,
}

/// Result of applying a `max_tokens` budget to a call-scan page.
pub(super) struct BudgetedCallPage {
    pub hits: Vec<ReferenceHit>,
    pub next_cursor: Option<Cursor>,
    pub budgeted: bool,
}

/// Apply a `max_tokens` budget to an already-built call-scan page and recompute its cursor.
///
/// Hits are best-first (scan order). When the budget drops trailing hits the cursor is
/// re-anchored to the last KEPT hit's Fjall key so the next page resumes immediately after
/// it with no gap or overlap. `max_tokens = None` is a no-op (original page passes through).
pub(super) fn budget_call_page(page: CallScanPage, max_tokens: Option<u32>) -> BudgetedCallPage {
    if max_tokens.is_none() {
        return BudgetedCallPage {
            hits: page.hits,
            next_cursor: page.next_cursor,
            budgeted: false,
        };
    }
    let budget = super::budget::apply_budget(page.hits, max_tokens);
    if !budget.budgeted {
        // Budget kept every hit on the page — leave the original scan cursor untouched.
        return BudgetedCallPage {
            hits: budget.items,
            next_cursor: page.next_cursor,
            budgeted: false,
        };
    }
    // Re-anchor the cursor to the last kept hit. `budgeted` implies at least one drop and a
    // non-empty page, so `kept >= 1` and the index is in range.
    let kept = budget.items.len();
    let next_cursor = page.hit_keys.get(kept - 1).map(|k| Cursor::encode_fjall(k));
    BudgetedCallPage {
        hits: budget.items,
        next_cursor,
        budgeted: true,
    }
}

/// Shared inner loop for `find_references` / `find_callers`: full-partition scan of
/// `calls_by_callee` with a `memmem` case-sensitive substring filter on the callee name.
/// Materializes up to `limit` hits and caps at `scan_cap = limit * 8` matching entries
/// to bound work on extremely common names.
///
/// When `cursor_after` is `Some`, the scan resumes from the key immediately following
/// the cursor (exclusive). The cursor returned in [`CallScanPage::next_cursor`] is the
/// last key emitted on this page — pass it back on the next call to advance.
fn scan_calls_by_name(
    idx: &crate::index::IndexDb,
    name: &str,
    limit: usize,
    cursor_after: Option<&[u8]>,
) -> Result<CallScanPage, McpError> {
    // Build the finder once; full-partition substring scan per the B3/I14 spec.
    let finder = memchr::memmem::Finder::new(name.as_bytes());

    let lower: Bound<Vec<u8>> = match cursor_after {
        Some(k) => Bound::Excluded(k.to_vec()),
        None => Bound::Unbounded,
    };
    let mut hits: Vec<ReferenceHit> = Vec::with_capacity(limit.min(64));
    // Parallel to `hits`: the Fjall key for each emitted hit, so a later token budget can
    // re-anchor the cursor to the last KEPT hit instead of the last scanned one.
    let mut hit_keys: Vec<Vec<u8>> = Vec::with_capacity(limit.min(64));
    let mut total: u32 = 0;
    let mut total_is_partial = false;
    let scan_cap = limit.saturating_mul(8).max(2_000);
    let mut has_more = false;
    let mut matched: usize = 0;
    for guard in idx
        .calls_by_callee
        .range::<Vec<u8>, _>((lower, Bound::Unbounded))
    {
        let (k, _) = guard
            .into_inner()
            .map_err(|e| McpError::internal_error(format!("index iter: {e}"), None))?;
        let Some((callee, rel, start)) = crate::index::keys::parse_call_by_callee(&k) else {
            continue;
        };
        // Case-sensitive substring filter — skip non-matching callees cheaply.
        if finder.find(callee.as_bytes()).is_none() {
            continue;
        }
        total += 1;
        matched += 1;
        if hits.len() < limit {
            let (line, column) = resolve_call_line_col(idx, &rel, start);
            hits.push(ReferenceHit {
                path: rel,
                line,
                column,
                callee,
            });
            hit_keys.push(k.to_vec());
        } else {
            // We collected a full page; this extra entry proves more remain on disk.
            has_more = true;
        }
        if matched >= scan_cap {
            total_is_partial = true;
            break;
        }
    }
    let next_cursor = if has_more {
        hit_keys.last().map(|k| Cursor::encode_fjall(k))
    } else {
        None
    };
    Ok(CallScanPage {
        total,
        total_is_partial,
        hits,
        next_cursor,
        hit_keys,
    })
}

/// Route a call scan to the Fjall index when it's open, or to the in-RAM index
/// built from the L2 blobs when it isn't.
///
/// `index_db == None` happens on a read-only `serve` session that lost the
/// single-holder Fjall lock to another process (fjall is single-process; see
/// `tests/multisession_smoke.rs`). Such a session still has the concurrently
/// readable blobs, so `find_references` / `find_callers` answer from
/// [`InRamCallIndex`] instead of failing — letting many sessions share one repo.
fn scan_calls(
    idx: Option<&crate::index::IndexDb>,
    cache: &super::MapCache,
    name: &str,
    limit: usize,
    cursor_after: Option<&[u8]>,
) -> Result<CallScanPage, McpError> {
    match idx {
        Some(idx) => scan_calls_by_name(idx, name, limit, cursor_after),
        None => Ok(match cache.calls.as_ref() {
            Some(calls) => scan_calls_in_ram(calls, name, limit, cursor_after),
            None => empty_call_page(),
        }),
    }
}

fn empty_call_page() -> CallScanPage {
    CallScanPage {
        total: 0,
        total_is_partial: false,
        hits: Vec::new(),
        next_cursor: None,
        hit_keys: Vec::new(),
    }
}

/// In-RAM `scan_calls_by_name` twin over [`InRamCallIndex`]. Same case-sensitive
/// `memmem` substring filter, same `limit` / `scan_cap` / cursor semantics — the
/// entries carry the exact Fjall key the writer would persist, so cursors and
/// scan order round-trip identically between the two paths.
fn scan_calls_in_ram(
    index: &InRamCallIndex,
    name: &str,
    limit: usize,
    cursor_after: Option<&[u8]>,
) -> CallScanPage {
    let finder = memchr::memmem::Finder::new(name.as_bytes());
    // Entries are sorted by key, so resume = first entry strictly past the cursor.
    let start = match cursor_after {
        Some(cursor) => index
            .entries
            .partition_point(|e| e.key.as_slice() <= cursor),
        None => 0,
    };
    let mut hits: Vec<ReferenceHit> = Vec::with_capacity(limit.min(64));
    let mut hit_keys: Vec<Vec<u8>> = Vec::with_capacity(limit.min(64));
    let mut total: u32 = 0;
    let mut total_is_partial = false;
    let scan_cap = limit.saturating_mul(8).max(2_000);
    let mut has_more = false;
    let mut matched: usize = 0;
    for entry in &index.entries[start..] {
        if finder.find(entry.callee.as_bytes()).is_none() {
            continue;
        }
        total += 1;
        matched += 1;
        if hits.len() < limit {
            hits.push(ReferenceHit {
                path: entry.rel.clone(),
                line: entry.line,
                column: entry.column,
                callee: entry.callee.clone(),
            });
            hit_keys.push(entry.key.clone());
        } else {
            has_more = true;
        }
        if matched >= scan_cap {
            total_is_partial = true;
            break;
        }
    }
    let next_cursor = if has_more {
        hit_keys.last().map(|k| Cursor::encode_fjall(k))
    } else {
        None
    };
    CallScanPage {
        total,
        total_is_partial,
        hits,
        next_cursor,
        hit_keys,
    }
}

/// In-RAM mirror of the Fjall `calls_by_callee` + `calls_by_path` keyspaces, built
/// from the L2 call blobs for read-only `serve` sessions that can't open the
/// single-holder Fjall index. Lets unlimited concurrent sessions answer
/// `find_references` / `find_callers` / `call_graph` from the shared, immutable,
/// concurrently-readable blobs.
pub(crate) struct InRamCallIndex {
    /// Sorted ascending by `key` to match Fjall's `range` iteration order
    /// (drives `find_references` / `find_callers`).
    entries: Vec<InRamCall>,
    /// path → its call sites (the `calls_by_path` keyspace), for the call-graph
    /// "callees" direction.
    by_path: ahash::AHashMap<crate::path::RelPath, Vec<CallRef>>,
}

struct InRamCall {
    /// `keys::call_by_callee(callee, rel, start_byte)` — the exact key the writer
    /// persists, reused so cursors round-trip identically across the two paths.
    key: Vec<u8>,
    callee: String,
    rel: crate::path::RelPath,
    /// 0-based byte offset of the call site (for containing-function resolution).
    start_byte: u32,
    /// 1-based line (`start_row + 1`), matching [`resolve_call_line_col`].
    line: u32,
    /// 0-based byte column.
    column: u32,
}

/// A call site within a file: the callee identifier and its start byte offset.
pub(crate) struct CallRef {
    pub callee: String,
    pub start_byte: u32,
}

impl InRamCallIndex {
    /// Build the index by decoding the L2 calls from every file's combined blob.
    /// File reads/decodes run in parallel (pure read, like `MapCache::build`); the
    /// two views are assembled serially afterward.
    pub(crate) fn build(store: &crate::store::Store) -> Self {
        use rayon::prelude::*;
        let per_file: Vec<(crate::path::RelPath, Vec<crate::extract::Call>)> = store
            .index
            .files
            .par_iter()
            .filter_map(|(rel, entry)| {
                let calls = store.read_l2_by_hex(&entry.hash_hex).ok().flatten()?.calls;
                Some((rel.clone(), calls))
            })
            .collect();
        let mut entries: Vec<InRamCall> = Vec::new();
        let mut by_path: ahash::AHashMap<crate::path::RelPath, Vec<CallRef>> =
            ahash::AHashMap::with_capacity(per_file.len());
        for (rel, calls) in per_file {
            let mut refs: Vec<CallRef> = Vec::with_capacity(calls.len());
            for call in calls {
                if let Some(key) =
                    crate::index::keys::call_by_callee(&call.callee, &rel, call.start_byte)
                {
                    entries.push(InRamCall {
                        key,
                        callee: call.callee.clone(),
                        rel: rel.clone(),
                        start_byte: call.start_byte,
                        line: call.start_row + 1,
                        column: call.start_col,
                    });
                }
                refs.push(CallRef {
                    callee: call.callee,
                    start_byte: call.start_byte,
                });
            }
            by_path.insert(rel, refs);
        }
        entries.sort_unstable_by(|a, b| a.key.cmp(&b.key));
        Self { entries, by_path }
    }

    /// Call sites whose callee is exactly `name`, as `(path, start_byte)`. Mirrors a
    /// `calls_by_callee` exact-name scan for the call-graph "callers" direction.
    pub(crate) fn callers_of<'a>(
        &'a self,
        name: &'a str,
    ) -> impl Iterator<Item = (&'a crate::path::RelPath, u32)> + 'a {
        self.entries
            .iter()
            .filter(move |c| c.callee == name)
            .map(|c| (&c.rel, c.start_byte))
    }

    /// All call sites in `rel`, for the call-graph "callees" direction (the
    /// `calls_by_path` keyspace).
    pub(crate) fn calls_in_file(&self, rel: &crate::path::RelPath) -> &[CallRef] {
        self.by_path.get(rel).map_or(&[], Vec::as_slice)
    }
}

#[cfg(test)]
mod tests {
    use super::{InRamCallIndex, scan_calls_in_ram};
    use crate::config::ConfigV1;
    use crate::scanner::{ScanSource, scan};
    use crate::store::{Store, VIEW_WORKING};

    /// The in-RAM index (built from blobs, used by read-only sessions) must return
    /// the same references the Fjall path would — this is what keeps `find_references`
    /// working for the 2nd+ concurrent session that can't open the Fjall lock.
    #[test]
    fn in_ram_call_index_resolves_references() {
        let dir = tempfile::tempdir().expect("tempdir");
        let root = dir.path();
        std::fs::write(root.join("a.rs"), b"pub fn alpha() {}\n").expect("a.rs");
        std::fs::write(root.join("b.rs"), b"fn beta() { alpha(); alpha(); }\n").expect("b.rs");
        let mut store = Store::open(root, VIEW_WORKING).expect("open");
        scan(
            root,
            &mut store,
            &ConfigV1::with_defaults(),
            ScanSource::WorkingTree,
        )
        .expect("scan");

        let index = InRamCallIndex::build(&store);
        let page = scan_calls_in_ram(&index, "alpha", 100, None);
        assert_eq!(page.total, 2, "two alpha() call sites in b.rs");
        assert_eq!(page.hits.len(), 2);
        assert!(page.hits.iter().all(|h| h.callee == "alpha"));
        assert!(
            page.hits.iter().all(|h| h.path.as_str() == Some("b.rs")),
            "both references live in b.rs"
        );
    }
}