sift-core 0.2.0

pub mod meta;
mod snapshot;
pub mod store;
pub mod trigram;

use std::collections::HashSet;
use std::path::{Path, PathBuf};

use serde::{Deserialize, Serialize};

use crate::search::filter::VisibilityConfig;
use crate::search::output::mode::CandidateCoverage;

pub use trigram::TrigramIndexError;

/// How an index query plan resolves candidates.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Default, Serialize, Deserialize)]
pub enum PlanMode {
    /// The query was narrowed using trigram candidates from the index.
    #[default]
    IndexedCandidates,
    /// No trigrams were usable — all indexed files must be scanned.
    FullScan,
}

#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub struct QueryPlanOutput {
    pub pattern: String,
    pub mode: PlanMode,
}

/// Whether the index was built from a directory or a single file.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Default, Serialize, Deserialize)]
pub enum CorpusKind {
    /// Built from a directory path — all discovered files were indexed.
    #[default]
    Directory,
    /// Built from a single file path — only that file was indexed.
    SingleFile,
}

/// Configuration for building or updating an index over a corpus.
pub struct IndexConfig<'a> {
    pub corpus: CorpusSpec<'a>,
    pub visibility: VisibilityConfig,
}

/// Description of a corpus to index.
pub struct CorpusSpec<'a> {
    pub root: &'a Path,
    pub kind: CorpusKind,
    pub follow_links: bool,
    pub include_paths: &'a [PathBuf],
    pub exclude_paths: &'a [PathBuf],
}

/// Errors specific to the index registry layer.
#[derive(Debug, thiserror::Error)]
pub enum IndexError {
    #[error("invalid index layout: {path}")]
    InvalidLayout { path: PathBuf },

    #[error(transparent)]
    Trigram(#[from] TrigramIndexError),

    #[error("IO error inspecting index path {path}: {source}")]
    Io {
        path: PathBuf,
        source: std::io::Error,
    },

    #[error("unknown index kind: {0}")]
    UnknownIndexKind(String),

    #[error("invalid snapshot manifest at {path}: {source}")]
    InvalidManifest {
        path: PathBuf,
        source: serde_json::Error,
    },
}

/// Tag identifying an index kind for lifecycle dispatch (build, open, update).
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Serialize, Deserialize)]
#[serde(rename_all = "lowercase")]
pub enum IndexKind {
    Trigram,
}

impl IndexKind {
    pub const ALL: &[Self] = &[Self::Trigram];

    #[must_use]
    pub const fn as_str(self) -> &'static str {
        match self {
            Self::Trigram => "trigram",
        }
    }

    pub(crate) fn build(self, config: &IndexConfig<'_>, output_dir: &Path) -> crate::Result<()> {
        match self {
            Self::Trigram => {
                trigram::TrigramIndex::build(config, output_dir)?;
                Ok(())
            }
        }
    }

    pub(crate) fn open_from_dir(
        self,
        index_dir: &Path,
        root: &Path,
        corpus_kind: CorpusKind,
    ) -> crate::Result<Index> {
        match self {
            Self::Trigram => Ok(Index::Trigram(trigram::TrigramIndex::open(
                index_dir,
                root,
                corpus_kind,
            )?)),
        }
    }

    /// Returns `true` if a new index was written.
    pub(crate) fn update(
        self,
        snapshot_dir: &Path,
        config: &IndexConfig<'_>,
        output_dir: &Path,
    ) -> crate::Result<bool> {
        let existing_dir = snapshot_dir.join(self.as_str());
        if !existing_dir.exists() {
            self.build(config, output_dir)?;
            return Ok(true);
        }
        let root = config
            .corpus
            .root
            .canonicalize()
            .unwrap_or_else(|_| config.corpus.root.to_path_buf());
        match self {
            Self::Trigram => {
                let existing =
                    trigram::TrigramIndex::open(&existing_dir, &root, config.corpus.kind)?;
                Ok(existing.update(config, output_dir)?.is_some())
            }
        }
    }
}

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

impl std::str::FromStr for IndexKind {
    type Err = String;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        match s {
            "trigram" => Ok(Self::Trigram),
            other => Err(format!("unknown index kind: {other}")),
        }
    }
}

/// An opened index instance, used for search-time dispatch.
pub enum Index {
    Trigram(trigram::TrigramIndex),
}

impl Index {
    #[must_use]
    pub fn root(&self) -> &Path {
        match self {
            Self::Trigram(idx) => idx.root(),
        }
    }

    #[must_use]
    pub const fn corpus_kind(&self) -> CorpusKind {
        match self {
            Self::Trigram(idx) => idx.corpus_kind(),
        }
    }

    #[must_use]
    pub fn candidates(&self, query: &crate::query::QuerySpec<'_>) -> Vec<crate::Candidate> {
        match self {
            Self::Trigram(idx) => idx.candidates(query),
        }
    }

    #[must_use]
    pub fn all_files(&self) -> Vec<crate::Candidate> {
        match self {
            Self::Trigram(idx) => idx.all_files(),
        }
    }
}

/// Registry of opened indexes read from a snapshot store.
pub struct Indexes {
    inner: Vec<Index>,
    root: PathBuf,
}

impl Indexes {
    /// Create an Indexes registry from a single index and its root.
    ///
    /// Useful for testing and benchmarking.
    #[must_use]
    pub fn from_single(index: Index, root: PathBuf) -> Self {
        Self {
            inner: vec![index],
            root,
        }
    }

    /// Open all indexes found under `sift_dir`.
    ///
    /// # Errors
    ///
    /// Returns [`IndexError::InvalidManifest`] if a snapshot manifest is
    /// malformed, or [`IndexError::Trigram`] if a trigram index is malformed.
    ///
    /// Returns an empty registry if no current snapshot exists (walk fallback).
    pub fn open(sift_dir: &Path) -> Result<Self, IndexError> {
        let store = store::IndexStore::open(sift_dir).map_err(|e| match e {
            crate::Error::Index(ie) => ie,
            crate::Error::Io(io) => IndexError::Io {
                path: sift_dir.to_path_buf(),
                source: io,
            },
            _ => IndexError::Io {
                path: sift_dir.to_path_buf(),
                source: std::io::Error::other(e.to_string()),
            },
        })?;

        let inner = store.open_current().map_err(|e| match e {
            crate::Error::Index(ie) => ie,
            crate::Error::Io(io) => IndexError::Io {
                path: sift_dir.to_path_buf(),
                source: io,
            },
            _ => IndexError::Io {
                path: sift_dir.to_path_buf(),
                source: std::io::Error::other(e.to_string()),
            },
        })?;

        let root = meta::StoreMeta::read(sift_dir)
            .ok()
            .map(|m| m.root)
            .unwrap_or_default();

        Ok(Self { inner, root })
    }

    #[must_use]
    pub const fn is_empty(&self) -> bool {
        self.inner.is_empty()
    }

    #[must_use]
    pub fn root(&self) -> &Path {
        &self.root
    }

    /// Resolve candidates for a query across all registered indexes.
    ///
    /// Conservative sets from each [`SearchIndex`] are intersected using
    /// `Candidate::rel_path` equality (no hashing), so distinct paths are never
    /// merged by accident.
    #[must_use]
    pub fn resolve_candidates(&self, query: &crate::query::QuerySpec<'_>) -> Vec<crate::Candidate> {
        let mut iter = self.inner.iter();
        let Some(first) = iter.next() else {
            return Vec::new();
        };

        let mut candidates = first.candidates(query);

        for index in iter {
            let next: HashSet<PathBuf> = index
                .candidates(query)
                .into_iter()
                .map(|c| c.rel_path().to_path_buf())
                .collect();
            candidates.retain(|c| next.contains(c.rel_path()));
            if candidates.is_empty() {
                break;
            }
        }

        candidates
    }

    /// Resolve candidates for a query, selecting narrowed or complete coverage.
    #[must_use]
    pub fn candidates(
        &self,
        query: &crate::query::QuerySpec<'_>,
        coverage: CandidateCoverage,
    ) -> Vec<crate::Candidate> {
        match coverage {
            CandidateCoverage::Narrowed => self.resolve_candidates(query),
            CandidateCoverage::Complete => self.resolve_all_files(),
        }
    }

    /// Return all indexed files across all registered indexes.
    #[must_use]
    pub fn resolve_all_files(&self) -> Vec<crate::Candidate> {
        let mut iter = self.inner.iter();
        let Some(first) = iter.next() else {
            return Vec::new();
        };

        let mut files = first.all_files();

        for index in iter {
            let next: HashSet<PathBuf> = index
                .all_files()
                .into_iter()
                .map(|c| c.rel_path().to_path_buf())
                .collect();
            files.retain(|c| next.contains(c.rel_path()));
            if files.is_empty() {
                break;
            }
        }

        files
    }

    #[must_use]
    pub fn first(&self) -> Option<&Index> {
        self.inner.first()
    }

    /// Returns the corpus kind if all indexes agree, or `None` for mixed/empty.
    #[must_use]
    pub fn corpus_kind(&self) -> Option<CorpusKind> {
        let kind = self.inner.first()?.corpus_kind();
        if self.inner.iter().any(|idx| idx.corpus_kind() != kind) {
            return None;
        }
        Some(kind)
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct FileId(usize);

impl FileId {
    #[must_use]
    pub const fn new(value: usize) -> Self {
        Self(value)
    }

    #[must_use]
    pub const fn get(self) -> usize {
        self.0
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct IndexId(usize);

impl IndexId {
    #[must_use]
    pub const fn new(value: usize) -> Self {
        Self(value)
    }

    #[must_use]
    pub const fn get(self) -> usize {
        self.0
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::fs;
    use tempfile::TempDir;

    #[test]
    fn file_id_new_and_get() {
        let id = FileId::new(42);
        assert_eq!(id.get(), 42);
    }

    #[test]
    fn index_id_new_and_get() {
        let id = IndexId::new(7);
        assert_eq!(id.get(), 7);
    }

    #[test]
    fn indexes_open_empty_when_no_current_file() {
        let tmp = TempDir::new().expect("create temp dir");
        let sift_dir = tmp.path().join(".sift");
        fs::create_dir_all(&sift_dir).expect("create sift dir");
        let indexes = Indexes::open(&sift_dir).expect("open indexes");
        assert!(indexes.is_empty());
        assert!(indexes.root().as_os_str().is_empty());
    }

    #[test]
    fn indexes_first_returns_none_when_empty() {
        let tmp = TempDir::new().expect("create temp dir");
        let sift_dir = tmp.path().join(".sift");
        fs::create_dir_all(&sift_dir).expect("create sift dir");
        let indexes = Indexes::open(&sift_dir).expect("open indexes");
        assert!(indexes.first().is_none());
    }
}