mod db;
mod embedding;
mod parsing;
pub mod semantic_index_settings;

#[cfg(test)]
mod semantic_index_tests;

use crate::semantic_index_settings::SemanticIndexSettings;
use anyhow::{anyhow, Result};
use db::VectorDatabase;
use embedding::{EmbeddingProvider, OpenAIEmbeddings};
use futures::{channel::oneshot, Future};
use globset::GlobMatcher;
use gpui::{AppContext, AsyncAppContext, Entity, ModelContext, ModelHandle, Task, WeakModelHandle};
use language::{Anchor, Buffer, Language, LanguageRegistry};
use parking_lot::Mutex;
use parsing::{CodeContextRetriever, Document, PARSEABLE_ENTIRE_FILE_TYPES};
use postage::watch;
use project::{Fs, Project, WorktreeId};
use smol::channel;
use std::{
    collections::HashMap,
    mem,
    ops::Range,
    path::{Path, PathBuf},
    sync::{Arc, Weak},
    time::{Instant, SystemTime},
};
use util::{
    channel::{ReleaseChannel, RELEASE_CHANNEL, RELEASE_CHANNEL_NAME},
    http::HttpClient,
    paths::EMBEDDINGS_DIR,
    ResultExt,
};

const SEMANTIC_INDEX_VERSION: usize = 6;
const EMBEDDINGS_BATCH_SIZE: usize = 80;

pub fn init(
    fs: Arc<dyn Fs>,
    http_client: Arc<dyn HttpClient>,
    language_registry: Arc<LanguageRegistry>,
    cx: &mut AppContext,
) {
    settings::register::<SemanticIndexSettings>(cx);

    let db_file_path = EMBEDDINGS_DIR
        .join(Path::new(RELEASE_CHANNEL_NAME.as_str()))
        .join("embeddings_db");

    if *RELEASE_CHANNEL == ReleaseChannel::Stable
        || !settings::get::<SemanticIndexSettings>(cx).enabled
    {
        return;
    }

    cx.spawn(move |mut cx| async move {
        let semantic_index = SemanticIndex::new(
            fs,
            db_file_path,
            Arc::new(OpenAIEmbeddings {
                client: http_client,
                executor: cx.background(),
            }),
            language_registry,
            cx.clone(),
        )
        .await?;

        cx.update(|cx| {
            cx.set_global(semantic_index.clone());
        });

        anyhow::Ok(())
    })
    .detach();
}

pub struct SemanticIndex {
    fs: Arc<dyn Fs>,
    database_url: Arc<PathBuf>,
    embedding_provider: Arc<dyn EmbeddingProvider>,
    language_registry: Arc<LanguageRegistry>,
    db_update_tx: channel::Sender<DbOperation>,
    parsing_files_tx: channel::Sender<PendingFile>,
    _db_update_task: Task<()>,
    _embed_batch_tasks: Vec<Task<()>>,
    _batch_files_task: Task<()>,
    _parsing_files_tasks: Vec<Task<()>>,
    projects: HashMap<WeakModelHandle<Project>, ProjectState>,
}

struct ProjectState {
    worktree_db_ids: Vec<(WorktreeId, i64)>,
    outstanding_job_count_rx: watch::Receiver<usize>,
    _outstanding_job_count_tx: Arc<Mutex<watch::Sender<usize>>>,
}

struct JobHandle {
    tx: Weak<Mutex<watch::Sender<usize>>>,
}

impl ProjectState {
    fn db_id_for_worktree_id(&self, id: WorktreeId) -> Option<i64> {
        self.worktree_db_ids
            .iter()
            .find_map(|(worktree_id, db_id)| {
                if *worktree_id == id {
                    Some(*db_id)
                } else {
                    None
                }
            })
    }

    fn worktree_id_for_db_id(&self, id: i64) -> Option<WorktreeId> {
        self.worktree_db_ids
            .iter()
            .find_map(|(worktree_id, db_id)| {
                if *db_id == id {
                    Some(*worktree_id)
                } else {
                    None
                }
            })
    }
}

pub struct PendingFile {
    worktree_db_id: i64,
    relative_path: PathBuf,
    absolute_path: PathBuf,
    language: Arc<Language>,
    modified_time: SystemTime,
    job_handle: JobHandle,
}

pub struct SearchResult {
    pub buffer: ModelHandle<Buffer>,
    pub range: Range<Anchor>,
}

enum DbOperation {
    InsertFile {
        worktree_id: i64,
        documents: Vec<Document>,
        path: PathBuf,
        mtime: SystemTime,
        job_handle: JobHandle,
    },
    Delete {
        worktree_id: i64,
        path: PathBuf,
    },
    FindOrCreateWorktree {
        path: PathBuf,
        sender: oneshot::Sender<Result<i64>>,
    },
    FileMTimes {
        worktree_id: i64,
        sender: oneshot::Sender<Result<HashMap<PathBuf, SystemTime>>>,
    },
    WorktreePreviouslyIndexed {
        path: Arc<Path>,
        sender: oneshot::Sender<Result<bool>>,
    },
}

enum EmbeddingJob {
    Enqueue {
        worktree_id: i64,
        path: PathBuf,
        mtime: SystemTime,
        documents: Vec<Document>,
        job_handle: JobHandle,
    },
    Flush,
}

impl SemanticIndex {
    pub fn global(cx: &AppContext) -> Option<ModelHandle<SemanticIndex>> {
        if cx.has_global::<ModelHandle<Self>>() {
            Some(cx.global::<ModelHandle<SemanticIndex>>().clone())
        } else {
            None
        }
    }

    pub fn enabled(cx: &AppContext) -> bool {
        settings::get::<SemanticIndexSettings>(cx).enabled
            && *RELEASE_CHANNEL != ReleaseChannel::Stable
    }

    async fn new(
        fs: Arc<dyn Fs>,
        database_url: PathBuf,
        embedding_provider: Arc<dyn EmbeddingProvider>,
        language_registry: Arc<LanguageRegistry>,
        mut cx: AsyncAppContext,
    ) -> Result<ModelHandle<Self>> {
        let t0 = Instant::now();
        let database_url = Arc::new(database_url);

        let db = cx
            .background()
            .spawn(VectorDatabase::new(fs.clone(), database_url.clone()))
            .await?;

        log::trace!(
            "db initialization took {:?} milliseconds",
            t0.elapsed().as_millis()
        );

        Ok(cx.add_model(|cx| {
            let t0 = Instant::now();
            // Perform database operations
            let (db_update_tx, db_update_rx) = channel::unbounded();
            let _db_update_task = cx.background().spawn({
                async move {
                    while let Ok(job) = db_update_rx.recv().await {
                        Self::run_db_operation(&db, job)
                    }
                }
            });

            // Group documents into batches and send them to the embedding provider.
            let (embed_batch_tx, embed_batch_rx) =
                channel::unbounded::<Vec<(i64, Vec<Document>, PathBuf, SystemTime, JobHandle)>>();
            let mut _embed_batch_tasks = Vec::new();
            for _ in 0..cx.background().num_cpus() {
                let embed_batch_rx = embed_batch_rx.clone();
                _embed_batch_tasks.push(cx.background().spawn({
                    let db_update_tx = db_update_tx.clone();
                    let embedding_provider = embedding_provider.clone();
                    async move {
                        while let Ok(embeddings_queue) = embed_batch_rx.recv().await {
                            Self::compute_embeddings_for_batch(
                                embeddings_queue,
                                &embedding_provider,
                                &db_update_tx,
                            )
                            .await;
                        }
                    }
                }));
            }

            // Group documents into batches and send them to the embedding provider.
            let (batch_files_tx, batch_files_rx) = channel::unbounded::<EmbeddingJob>();
            let _batch_files_task = cx.background().spawn(async move {
                let mut queue_len = 0;
                let mut embeddings_queue = vec![];
                while let Ok(job) = batch_files_rx.recv().await {
                    Self::enqueue_documents_to_embed(
                        job,
                        &mut queue_len,
                        &mut embeddings_queue,
                        &embed_batch_tx,
                    );
                }
            });

            // Parse files into embeddable documents.
            let (parsing_files_tx, parsing_files_rx) = channel::unbounded::<PendingFile>();
            let mut _parsing_files_tasks = Vec::new();
            for _ in 0..cx.background().num_cpus() {
                let fs = fs.clone();
                let parsing_files_rx = parsing_files_rx.clone();
                let batch_files_tx = batch_files_tx.clone();
                let db_update_tx = db_update_tx.clone();
                _parsing_files_tasks.push(cx.background().spawn(async move {
                    let mut retriever = CodeContextRetriever::new();
                    while let Ok(pending_file) = parsing_files_rx.recv().await {
                        Self::parse_file(
                            &fs,
                            pending_file,
                            &mut retriever,
                            &batch_files_tx,
                            &parsing_files_rx,
                            &db_update_tx,
                        )
                        .await;
                    }
                }));
            }

            log::trace!(
                "semantic index task initialization took {:?} milliseconds",
                t0.elapsed().as_millis()
            );
            Self {
                fs,
                database_url,
                embedding_provider,
                language_registry,
                db_update_tx,
                parsing_files_tx,
                _db_update_task,
                _embed_batch_tasks,
                _batch_files_task,
                _parsing_files_tasks,
                projects: HashMap::new(),
            }
        }))
    }

    fn run_db_operation(db: &VectorDatabase, job: DbOperation) {
        match job {
            DbOperation::InsertFile {
                worktree_id,
                documents,
                path,
                mtime,
                job_handle,
            } => {
                db.insert_file(worktree_id, path, mtime, documents)
                    .log_err();
                drop(job_handle)
            }
            DbOperation::Delete { worktree_id, path } => {
                db.delete_file(worktree_id, path).log_err();
            }
            DbOperation::FindOrCreateWorktree { path, sender } => {
                let id = db.find_or_create_worktree(&path);
                sender.send(id).ok();
            }
            DbOperation::FileMTimes {
                worktree_id: worktree_db_id,
                sender,
            } => {
                let file_mtimes = db.get_file_mtimes(worktree_db_id);
                sender.send(file_mtimes).ok();
            }
            DbOperation::WorktreePreviouslyIndexed { path, sender } => {
                let worktree_indexed = db.worktree_previously_indexed(path.as_ref());
                sender.send(worktree_indexed).ok();
            }
        }
    }

    async fn compute_embeddings_for_batch(
        mut embeddings_queue: Vec<(i64, Vec<Document>, PathBuf, SystemTime, JobHandle)>,
        embedding_provider: &Arc<dyn EmbeddingProvider>,
        db_update_tx: &channel::Sender<DbOperation>,
    ) {
        let mut batch_documents = vec![];
        for (_, documents, _, _, _) in embeddings_queue.iter() {
            batch_documents.extend(documents.iter().map(|document| document.content.as_str()));
        }

        if let Ok(embeddings) = embedding_provider.embed_batch(batch_documents).await {
            log::trace!(
                "created {} embeddings for {} files",
                embeddings.len(),
                embeddings_queue.len(),
            );

            let mut i = 0;
            let mut j = 0;

            for embedding in embeddings.iter() {
                while embeddings_queue[i].1.len() == j {
                    i += 1;
                    j = 0;
                }

                embeddings_queue[i].1[j].embedding = embedding.to_owned();
                j += 1;
            }

            for (worktree_id, documents, path, mtime, job_handle) in embeddings_queue.into_iter() {
                db_update_tx
                    .send(DbOperation::InsertFile {
                        worktree_id,
                        documents,
                        path,
                        mtime,
                        job_handle,
                    })
                    .await
                    .unwrap();
            }
        }
    }

    fn enqueue_documents_to_embed(
        job: EmbeddingJob,
        queue_len: &mut usize,
        embeddings_queue: &mut Vec<(i64, Vec<Document>, PathBuf, SystemTime, JobHandle)>,
        embed_batch_tx: &channel::Sender<Vec<(i64, Vec<Document>, PathBuf, SystemTime, JobHandle)>>,
    ) {
        let should_flush = match job {
            EmbeddingJob::Enqueue {
                documents,
                worktree_id,
                path,
                mtime,
                job_handle,
            } => {
                *queue_len += &documents.len();
                embeddings_queue.push((worktree_id, documents, path, mtime, job_handle));
                *queue_len >= EMBEDDINGS_BATCH_SIZE
            }
            EmbeddingJob::Flush => true,
        };

        if should_flush {
            embed_batch_tx
                .try_send(mem::take(embeddings_queue))
                .unwrap();
            *queue_len = 0;
        }
    }

    async fn parse_file(
        fs: &Arc<dyn Fs>,
        pending_file: PendingFile,
        retriever: &mut CodeContextRetriever,
        batch_files_tx: &channel::Sender<EmbeddingJob>,
        parsing_files_rx: &channel::Receiver<PendingFile>,
        db_update_tx: &channel::Sender<DbOperation>,
    ) {
        if let Some(content) = fs.load(&pending_file.absolute_path).await.log_err() {
            if let Some(documents) = retriever
                .parse_file_with_template(
                    &pending_file.relative_path,
                    &content,
                    pending_file.language,
                )
                .log_err()
            {
                log::trace!(
                    "parsed path {:?}: {} documents",
                    pending_file.relative_path,
                    documents.len()
                );

                if documents.len() == 0 {
                    db_update_tx
                        .send(DbOperation::InsertFile {
                            worktree_id: pending_file.worktree_db_id,
                            documents,
                            path: pending_file.relative_path,
                            mtime: pending_file.modified_time,
                            job_handle: pending_file.job_handle,
                        })
                        .await
                        .unwrap();
                } else {
                    batch_files_tx
                        .try_send(EmbeddingJob::Enqueue {
                            worktree_id: pending_file.worktree_db_id,
                            path: pending_file.relative_path,
                            mtime: pending_file.modified_time,
                            job_handle: pending_file.job_handle,
                            documents,
                        })
                        .unwrap();
                }
            }
        }

        if parsing_files_rx.len() == 0 {
            batch_files_tx.try_send(EmbeddingJob::Flush).unwrap();
        }
    }

    fn find_or_create_worktree(&self, path: PathBuf) -> impl Future<Output = Result<i64>> {
        let (tx, rx) = oneshot::channel();
        self.db_update_tx
            .try_send(DbOperation::FindOrCreateWorktree { path, sender: tx })
            .unwrap();
        async move { rx.await? }
    }

    fn get_file_mtimes(
        &self,
        worktree_id: i64,
    ) -> impl Future<Output = Result<HashMap<PathBuf, SystemTime>>> {
        let (tx, rx) = oneshot::channel();
        self.db_update_tx
            .try_send(DbOperation::FileMTimes {
                worktree_id,
                sender: tx,
            })
            .unwrap();
        async move { rx.await? }
    }

    fn worktree_previously_indexed(&self, path: Arc<Path>) -> impl Future<Output = Result<bool>> {
        let (tx, rx) = oneshot::channel();
        self.db_update_tx
            .try_send(DbOperation::WorktreePreviouslyIndexed { path, sender: tx })
            .unwrap();
        async move { rx.await? }
    }

    pub fn project_previously_indexed(
        &mut self,
        project: ModelHandle<Project>,
        cx: &mut ModelContext<Self>,
    ) -> Task<Result<bool>> {
        let worktree_scans_complete = project
            .read(cx)
            .worktrees(cx)
            .map(|worktree| {
                let scan_complete = worktree.read(cx).as_local().unwrap().scan_complete();
                async move {
                    scan_complete.await;
                }
            })
            .collect::<Vec<_>>();

        let worktrees_indexed_previously = project
            .read(cx)
            .worktrees(cx)
            .map(|worktree| self.worktree_previously_indexed(worktree.read(cx).abs_path()))
            .collect::<Vec<_>>();

        cx.spawn(|_, _cx| async move {
            futures::future::join_all(worktree_scans_complete).await;

            let worktree_indexed_previously =
                futures::future::join_all(worktrees_indexed_previously).await;

            Ok(worktree_indexed_previously
                .iter()
                .filter(|worktree| worktree.is_ok())
                .all(|v| v.as_ref().log_err().is_some_and(|v| v.to_owned())))
        })
    }

    pub fn index_project(
        &mut self,
        project: ModelHandle<Project>,
        cx: &mut ModelContext<Self>,
    ) -> Task<Result<(usize, watch::Receiver<usize>)>> {
        let t0 = Instant::now();
        let worktree_scans_complete = project
            .read(cx)
            .worktrees(cx)
            .map(|worktree| {
                let scan_complete = worktree.read(cx).as_local().unwrap().scan_complete();
                async move {
                    scan_complete.await;
                }
            })
            .collect::<Vec<_>>();
        let worktree_db_ids = project
            .read(cx)
            .worktrees(cx)
            .map(|worktree| {
                self.find_or_create_worktree(worktree.read(cx).abs_path().to_path_buf())
            })
            .collect::<Vec<_>>();

        let language_registry = self.language_registry.clone();
        let db_update_tx = self.db_update_tx.clone();
        let parsing_files_tx = self.parsing_files_tx.clone();

        cx.spawn(|this, mut cx| async move {
            futures::future::join_all(worktree_scans_complete).await;

            let worktree_db_ids = futures::future::join_all(worktree_db_ids).await;

            let worktrees = project.read_with(&cx, |project, cx| {
                project
                    .worktrees(cx)
                    .map(|worktree| worktree.read(cx).snapshot())
                    .collect::<Vec<_>>()
            });

            let mut worktree_file_mtimes = HashMap::new();
            let mut db_ids_by_worktree_id = HashMap::new();
            for (worktree, db_id) in worktrees.iter().zip(worktree_db_ids) {
                let db_id = db_id?;
                db_ids_by_worktree_id.insert(worktree.id(), db_id);
                worktree_file_mtimes.insert(
                    worktree.id(),
                    this.read_with(&cx, |this, _| this.get_file_mtimes(db_id))
                        .await?,
                );
            }

            let (job_count_tx, job_count_rx) = watch::channel_with(0);
            let job_count_tx = Arc::new(Mutex::new(job_count_tx));
            this.update(&mut cx, |this, _| {
                this.projects.insert(
                    project.downgrade(),
                    ProjectState {
                        worktree_db_ids: db_ids_by_worktree_id
                            .iter()
                            .map(|(a, b)| (*a, *b))
                            .collect(),
                        outstanding_job_count_rx: job_count_rx.clone(),
                        _outstanding_job_count_tx: job_count_tx.clone(),
                    },
                );
            });

            cx.background()
                .spawn(async move {
                    let mut count = 0;
                    for worktree in worktrees.into_iter() {
                        let mut file_mtimes = worktree_file_mtimes.remove(&worktree.id()).unwrap();
                        for file in worktree.files(false, 0) {
                            let absolute_path = worktree.absolutize(&file.path);

                            if let Ok(language) = language_registry
                                .language_for_file(&absolute_path, None)
                                .await
                            {
                                if !PARSEABLE_ENTIRE_FILE_TYPES.contains(&language.name().as_ref())
                                    && language
                                        .grammar()
                                        .and_then(|grammar| grammar.embedding_config.as_ref())
                                        .is_none()
                                {
                                    continue;
                                }

                                let path_buf = file.path.to_path_buf();
                                let stored_mtime = file_mtimes.remove(&file.path.to_path_buf());
                                let already_stored = stored_mtime
                                    .map_or(false, |existing_mtime| existing_mtime == file.mtime);

                                if !already_stored {
                                    count += 1;
                                    *job_count_tx.lock().borrow_mut() += 1;
                                    let job_handle = JobHandle {
                                        tx: Arc::downgrade(&job_count_tx),
                                    };
                                    parsing_files_tx
                                        .try_send(PendingFile {
                                            worktree_db_id: db_ids_by_worktree_id[&worktree.id()],
                                            relative_path: path_buf,
                                            absolute_path,
                                            language,
                                            job_handle,
                                            modified_time: file.mtime,
                                        })
                                        .unwrap();
                                }
                            }
                        }
                        for file in file_mtimes.keys() {
                            db_update_tx
                                .try_send(DbOperation::Delete {
                                    worktree_id: db_ids_by_worktree_id[&worktree.id()],
                                    path: file.to_owned(),
                                })
                                .unwrap();
                        }
                    }

                    log::trace!(
                        "walking worktree took {:?} milliseconds",
                        t0.elapsed().as_millis()
                    );
                    anyhow::Ok((count, job_count_rx))
                })
                .await
        })
    }

    pub fn outstanding_job_count_rx(
        &self,
        project: &ModelHandle<Project>,
    ) -> Option<watch::Receiver<usize>> {
        Some(
            self.projects
                .get(&project.downgrade())?
                .outstanding_job_count_rx
                .clone(),
        )
    }

    pub fn search_project(
        &mut self,
        project: ModelHandle<Project>,
        phrase: String,
        limit: usize,
        include_globs: Vec<GlobMatcher>,
        exclude_globs: Vec<GlobMatcher>,
        cx: &mut ModelContext<Self>,
    ) -> Task<Result<Vec<SearchResult>>> {
        let project_state = if let Some(state) = self.projects.get(&project.downgrade()) {
            state
        } else {
            return Task::ready(Err(anyhow!("project not added")));
        };

        let worktree_db_ids = project
            .read(cx)
            .worktrees(cx)
            .filter_map(|worktree| {
                let worktree_id = worktree.read(cx).id();
                project_state.db_id_for_worktree_id(worktree_id)
            })
            .collect::<Vec<_>>();

        let embedding_provider = self.embedding_provider.clone();
        let database_url = self.database_url.clone();
        let fs = self.fs.clone();
        cx.spawn(|this, mut cx| async move {
            let documents = cx
                .background()
                .spawn(async move {
                    let database = VectorDatabase::new(fs, database_url).await?;

                    let phrase_embedding = embedding_provider
                        .embed_batch(vec![&phrase])
                        .await?
                        .into_iter()
                        .next()
                        .unwrap();

                    database.top_k_search(
                        &worktree_db_ids,
                        &phrase_embedding,
                        limit,
                        include_globs,
                        exclude_globs,
                    )
                })
                .await?;

            let mut tasks = Vec::new();
            let mut ranges = Vec::new();
            let weak_project = project.downgrade();
            project.update(&mut cx, |project, cx| {
                for (worktree_db_id, file_path, byte_range) in documents {
                    let project_state =
                        if let Some(state) = this.read(cx).projects.get(&weak_project) {
                            state
                        } else {
                            return Err(anyhow!("project not added"));
                        };
                    if let Some(worktree_id) = project_state.worktree_id_for_db_id(worktree_db_id) {
                        tasks.push(project.open_buffer((worktree_id, file_path), cx));
                        ranges.push(byte_range);
                    }
                }

                Ok(())
            })?;

            let buffers = futures::future::join_all(tasks).await;

            Ok(buffers
                .into_iter()
                .zip(ranges)
                .filter_map(|(buffer, range)| {
                    let buffer = buffer.log_err()?;
                    let range = buffer.read_with(&cx, |buffer, _| {
                        buffer.anchor_before(range.start)..buffer.anchor_after(range.end)
                    });
                    Some(SearchResult { buffer, range })
                })
                .collect::<Vec<_>>())
        })
    }
}

impl Entity for SemanticIndex {
    type Event = ();
}

impl Drop for JobHandle {
    fn drop(&mut self) {
        if let Some(tx) = self.tx.upgrade() {
            let mut tx = tx.lock();
            *tx.borrow_mut() -= 1;
        }
    }
}