mod autobatcher;
mod batch;
pub mod error;
mod index_mapper;
pub mod task;
mod utils;

pub use milli;

pub type Result<T> = std::result::Result<T, Error>;
pub type TaskId = u32;

pub use error::Error;
pub use task::{Kind, KindWithContent, Status, TaskView};

use std::path::PathBuf;
use std::sync::{Arc, RwLock};

use file_store::{File, FileStore};
use roaring::RoaringBitmap;
use serde::Deserialize;
use synchronoise::SignalEvent;
use time::OffsetDateTime;
use uuid::Uuid;

use milli::heed::types::{OwnedType, SerdeBincode, SerdeJson, Str};
use milli::heed::{self, Database, Env};
use milli::update::IndexerConfig;
use milli::{Index, RoaringBitmapCodec, BEU32};

use crate::index_mapper::IndexMapper;
use crate::task::Task;

const DEFAULT_LIMIT: fn() -> u32 = || 20;

#[derive(derive_builder::Builder, Debug, Clone, Deserialize)]
#[serde(rename_all = "camelCase")]
pub struct Query {
    #[serde(default = "DEFAULT_LIMIT")]
    pub limit: u32,
    pub from: Option<u32>,
    pub status: Option<Vec<Status>>,
    #[serde(rename = "type")]
    pub kind: Option<Vec<Kind>>,
    pub index_uid: Option<Vec<String>>,
    pub uid: Option<Vec<TaskId>>,
}

impl Default for Query {
    fn default() -> Self {
        Self {
            limit: DEFAULT_LIMIT(),
            from: None,
            status: None,
            kind: None,
            index_uid: None,
            uid: None,
        }
    }
}

impl Query {
    pub fn with_status(self, status: Status) -> Self {
        let mut status_vec = self.status.unwrap_or_default();
        status_vec.push(status);
        Self {
            status: Some(status_vec),
            ..self
        }
    }

    pub fn with_kind(self, kind: Kind) -> Self {
        let mut kind_vec = self.kind.unwrap_or_default();
        kind_vec.push(kind);
        Self {
            kind: Some(kind_vec),
            ..self
        }
    }

    pub fn with_index(self, index_uid: String) -> Self {
        let mut index_vec = self.index_uid.unwrap_or_default();
        index_vec.push(index_uid);
        Self {
            index_uid: Some(index_vec),
            ..self
        }
    }

    pub fn with_uid(self, uid: TaskId) -> Self {
        let mut task_vec = self.uid.unwrap_or_default();
        task_vec.push(uid);
        Self {
            uid: Some(task_vec),
            ..self
        }
    }

    pub fn with_limit(self, limit: u32) -> Self {
        Self { limit, ..self }
    }
}

/// Database const names for the `IndexScheduler`.
mod db_name {
    pub const ALL_TASKS: &str = "all-tasks";
    pub const STATUS: &str = "status";
    pub const KIND: &str = "kind";
    pub const INDEX_TASKS: &str = "index-tasks";
}

/// This module is responsible for two things;
/// 1. Resolve the name of the indexes.
/// 2. Schedule the tasks.
pub struct IndexScheduler {
    /// The list of tasks currently processing and their starting date.
    pub(crate) processing_tasks: Arc<RwLock<(OffsetDateTime, RoaringBitmap)>>,

    pub(crate) file_store: FileStore,

    /// The LMDB environment which the DBs are associated with.
    pub(crate) env: Env,

    // The main database, it contains all the tasks accessible by their Id.
    pub(crate) all_tasks: Database<OwnedType<BEU32>, SerdeJson<Task>>,

    /// All the tasks ids grouped by their status.
    pub(crate) status: Database<SerdeBincode<Status>, RoaringBitmapCodec>,
    /// All the tasks ids grouped by their kind.
    pub(crate) kind: Database<SerdeBincode<Kind>, RoaringBitmapCodec>,
    /// Store the tasks associated to an index.
    pub(crate) index_tasks: Database<Str, RoaringBitmapCodec>,

    /// In charge of creating, opening, storing and returning indexes.
    pub(crate) index_mapper: IndexMapper,

    /// Get a signal when a batch needs to be processed.
    pub(crate) wake_up: Arc<SignalEvent>,

    // ================= test
    /// The next entry is dedicated to the tests.
    /// It provide a way to break in multiple part of the scheduler.
    #[cfg(test)]
    test_breakpoint_sdr: crossbeam::channel::Sender<Breakpoint>,
}

#[cfg(test)]
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Breakpoint {
    Start,
    BatchCreated,
    BeforeProcessing,
    AfterProcessing,
}

impl IndexScheduler {
    pub fn new(
        tasks_path: PathBuf,
        update_file_path: PathBuf,
        indexes_path: PathBuf,
        index_size: usize,
        indexer_config: IndexerConfig,
        #[cfg(test)] test_breakpoint_sdr: crossbeam::channel::Sender<Breakpoint>,
    ) -> Result<Self> {
        std::fs::create_dir_all(&tasks_path)?;
        std::fs::create_dir_all(&update_file_path)?;
        std::fs::create_dir_all(&indexes_path)?;

        let mut options = heed::EnvOpenOptions::new();
        options.max_dbs(6);

        let env = options.open(tasks_path)?;
        let processing_tasks = (OffsetDateTime::now_utc(), RoaringBitmap::new());
        let file_store = FileStore::new(&update_file_path)?;

        // allow unreachable_code to get rids of the warning in the case of a test build.
        let this = Self {
            // by default there is no processing tasks
            processing_tasks: Arc::new(RwLock::new(processing_tasks)),
            file_store,
            all_tasks: env.create_database(Some(db_name::ALL_TASKS))?,
            status: env.create_database(Some(db_name::STATUS))?,
            kind: env.create_database(Some(db_name::KIND))?,
            index_tasks: env.create_database(Some(db_name::INDEX_TASKS))?,
            index_mapper: IndexMapper::new(&env, indexes_path, index_size, indexer_config)?,
            env,
            // we want to start the loop right away in case meilisearch was ctrl+Ced while processing things
            wake_up: Arc::new(SignalEvent::auto(true)),

            #[cfg(test)]
            test_breakpoint_sdr,
        };

        this.run();
        Ok(this)
    }

    /// This function will execute in a different thread and must be called only once.
    fn run(&self) {
        let run = Self {
            processing_tasks: self.processing_tasks.clone(),
            file_store: self.file_store.clone(),
            env: self.env.clone(),
            all_tasks: self.all_tasks,
            status: self.status,
            kind: self.kind,
            index_tasks: self.index_tasks,
            index_mapper: self.index_mapper.clone(),
            wake_up: self.wake_up.clone(),

            #[cfg(test)]
            test_breakpoint_sdr: self.test_breakpoint_sdr.clone(),
        };

        std::thread::spawn(move || loop {
            run.wake_up.wait();

            match run.tick() {
                Ok(()) => (),
                Err(e) => log::error!("{}", e),
            }
        });
    }

    /// Return the index corresponding to the name. If it wasn't opened before
    /// it'll be opened. But if it doesn't exist on disk it'll throw an
    /// `IndexNotFound` error.
    pub fn index(&self, name: &str) -> Result<Index> {
        let rtxn = self.env.read_txn()?;
        self.index_mapper.index(&rtxn, name)
    }

    /// Return and open all the indexes.
    pub fn indexes(&self) -> Result<Vec<(String, Index)>> {
        let rtxn = self.env.read_txn()?;
        self.index_mapper.indexes(&rtxn)
    }

    /// Returns the tasks corresponding to the query.
    pub fn get_tasks(&self, query: Query) -> Result<Vec<TaskView>> {
        let rtxn = self.env.read_txn()?;
        let last_task_id = match self.last_task_id(&rtxn)? {
            Some(tid) => query.from.map(|from| from.min(tid)).unwrap_or(tid),
            None => return Ok(Vec::new()),
        };

        // This is the list of all the tasks.
        let mut tasks = RoaringBitmap::from_sorted_iter(0..last_task_id).unwrap();

        if let Some(uids) = query.uid {
            tasks &= RoaringBitmap::from_iter(uids);
        }

        if let Some(status) = query.status {
            let mut status_tasks = RoaringBitmap::new();
            for status in status {
                status_tasks |= self.get_status(&rtxn, status)?;
            }
            tasks &= status_tasks;
        }

        if let Some(kind) = query.kind {
            let mut kind_tasks = RoaringBitmap::new();
            for kind in kind {
                kind_tasks |= self.get_kind(&rtxn, kind)?;
            }
            tasks &= kind_tasks;
        }

        if let Some(index) = query.index_uid {
            let mut index_tasks = RoaringBitmap::new();
            for index in index {
                index_tasks |= self.get_index(&rtxn, &index)?;
            }
            tasks &= index_tasks;
        }

        let tasks =
            self.get_existing_tasks(&rtxn, tasks.into_iter().rev().take(query.limit as usize))?;
        let (started_at, processing) = self
            .processing_tasks
            .read()
            .map_err(|_| Error::CorruptedTaskQueue)?
            .clone();

        let ret = tasks.into_iter().map(|task| task.as_task_view());
        if processing.is_empty() {
            Ok(ret.collect())
        } else {
            Ok(ret
                .map(|task| match processing.contains(task.uid) {
                    true => TaskView {
                        status: Status::Processing,
                        started_at: Some(started_at),
                        ..task
                    },
                    false => task,
                })
                .collect())
        }
    }

    /// Register a new task in the scheduler. If it fails and data was associated with the task
    /// it tries to delete the file.
    pub fn register(&self, task: KindWithContent) -> Result<TaskView> {
        let mut wtxn = self.env.write_txn()?;

        let task = Task {
            uid: self.next_task_id(&wtxn)?,
            enqueued_at: time::OffsetDateTime::now_utc(),
            started_at: None,
            finished_at: None,
            error: None,
            details: None,
            status: Status::Enqueued,
            kind: task,
        };

        self.all_tasks
            .append(&mut wtxn, &BEU32::new(task.uid), &task)?;

        if let Some(indexes) = task.indexes() {
            for index in indexes {
                self.update_index(&mut wtxn, index, |bitmap| {
                    bitmap.insert(task.uid);
                })?;
            }
        }

        self.update_status(&mut wtxn, Status::Enqueued, |bitmap| {
            bitmap.insert(task.uid);
        })?;

        self.update_kind(&mut wtxn, task.kind.as_kind(), |bitmap| {
            (bitmap.insert(task.uid));
        })?;

        // we persist the file in last to be sure everything before was applied successfuly
        task.persist()?;

        match wtxn.commit() {
            Ok(()) => (),
            e @ Err(_) => {
                task.remove_data()?;
                e?;
            }
        }

        self.notify();

        Ok(task.as_task_view())
    }

    pub fn create_update_file(&self) -> Result<(Uuid, File)> {
        Ok(self.file_store.new_update()?)
    }

    pub fn delete_update_file(&self, uuid: Uuid) -> Result<()> {
        Ok(self.file_store.delete(uuid)?)
    }

    /// Create and execute and store the result of one batch of registered tasks.
    fn tick(&self) -> Result<()> {
        #[cfg(test)]
        self.test_breakpoint_sdr.send(Breakpoint::Start).unwrap();

        let rtxn = self.env.read_txn()?;
        let batch = match self.create_next_batch(&rtxn)? {
            Some(batch) => batch,
            None => return Ok(()),
        };
        // we don't need this transaction any longer.
        drop(rtxn);

        // 1. store the starting date with the bitmap of processing tasks.
        let mut ids = batch.ids();
        ids.sort_unstable();
        let processing_tasks = RoaringBitmap::from_sorted_iter(ids.iter().copied()).unwrap();
        let started_at = OffsetDateTime::now_utc();
        *self.processing_tasks.write().unwrap() = (started_at, processing_tasks);

        #[cfg(test)]
        {
            self.test_breakpoint_sdr
                .send(Breakpoint::BatchCreated)
                .unwrap();
            self.test_breakpoint_sdr
                .send(Breakpoint::BeforeProcessing)
                .unwrap();
        }

        // 2. Process the tasks
        let res = self.process_batch(batch);

        let mut wtxn = self.env.write_txn()?;

        let finished_at = OffsetDateTime::now_utc();
        match res {
            Ok(tasks) => {
                for mut task in tasks {
                    task.started_at = Some(started_at);
                    task.finished_at = Some(finished_at);
                    task.status = Status::Succeeded;
                    // the info field should've been set by the process_batch function

                    self.update_task(&mut wtxn, &task)?;
                    task.remove_data()?;
                }
            }
            // In case of a failure we must get back and patch all the tasks with the error.
            Err(_err) => {
                for id in ids {
                    let mut task = self.get_task(&wtxn, id)?.ok_or(Error::CorruptedTaskQueue)?;
                    task.started_at = Some(started_at);
                    task.finished_at = Some(finished_at);
                    task.status = Status::Failed;
                    // TODO: TAMO: set the error correctly
                    // task.error = Some(err);

                    self.update_task(&mut wtxn, &task)?;
                    task.remove_data()?;
                }
            }
        }

        *self.processing_tasks.write().unwrap() = (finished_at, RoaringBitmap::new());

        wtxn.commit()?;
        log::info!("A batch of tasks was successfully completed.");

        #[cfg(test)]
        self.test_breakpoint_sdr
            .send(Breakpoint::AfterProcessing)
            .unwrap();

        Ok(())
    }

    /// Notify the scheduler there is or may be work to do.
    pub fn notify(&self) {
        self.wake_up.signal()
    }
}

#[cfg(test)]
mod tests {
    use big_s::S;
    use insta::*;
    use milli::update::IndexDocumentsMethod::{self, ReplaceDocuments, UpdateDocuments};
    use tempfile::TempDir;
    use uuid::Uuid;

    use crate::assert_smol_debug_snapshot;

    use super::*;

    impl IndexScheduler {
        pub fn test() -> (Self, IndexSchedulerHandle) {
            let tempdir = TempDir::new().unwrap();
            let (sender, receiver) = crossbeam::channel::bounded(0);

            let index_scheduler = Self::new(
                tempdir.path().join("db_path"),
                tempdir.path().join("file_store"),
                tempdir.path().join("indexes"),
                1024 * 1024,
                IndexerConfig::default(),
                sender,
            )
            .unwrap();

            let index_scheduler_handle = IndexSchedulerHandle {
                _tempdir: tempdir,
                test_breakpoint_rcv: receiver,
            };

            (index_scheduler, index_scheduler_handle)
        }
    }

    pub struct IndexSchedulerHandle {
        _tempdir: TempDir,
        test_breakpoint_rcv: crossbeam::channel::Receiver<Breakpoint>,
    }

    impl IndexSchedulerHandle {
        /// Wait until the provided breakpoint is reached.
        fn wait_till(&self, breakpoint: Breakpoint) {
            self.test_breakpoint_rcv.iter().find(|b| *b == breakpoint);
        }

        /// Wait until the provided breakpoint is reached.
        fn next_breakpoint(&self) -> Breakpoint {
            self.test_breakpoint_rcv.recv().unwrap()
        }

        /// The scheduler will not stop on breakpoints anymore.
        fn dont_block(self) {
            std::thread::spawn(move || loop {
                // unroll and ignore all the state the scheduler is going to send us.
                self.test_breakpoint_rcv.iter().last();
            });
        }
    }

    #[test]
    fn register() {
        let (index_scheduler, handle) = IndexScheduler::test();
        handle.dont_block();

        let kinds = [
            KindWithContent::IndexCreation {
                index_uid: S("catto"),
                primary_key: Some(S("mouse")),
            },
            KindWithContent::DocumentImport {
                index_uid: S("catto"),
                primary_key: None,
                method: ReplaceDocuments,
                content_file: Uuid::new_v4(),
                documents_count: 12,
                allow_index_creation: true,
            },
            KindWithContent::CancelTask { tasks: vec![0, 1] },
            KindWithContent::DocumentImport {
                index_uid: S("catto"),
                primary_key: None,
                method: ReplaceDocuments,
                content_file: Uuid::new_v4(),
                documents_count: 50,
                allow_index_creation: true,
            },
            KindWithContent::DocumentImport {
                index_uid: S("doggo"),
                primary_key: Some(S("bone")),
                method: ReplaceDocuments,
                content_file: Uuid::new_v4(),
                documents_count: 5000,
                allow_index_creation: true,
            },
        ];
        let mut inserted_tasks = Vec::new();
        for (idx, kind) in kinds.into_iter().enumerate() {
            let k = kind.as_kind();
            let task = index_scheduler.register(kind).unwrap();

            assert_eq!(task.uid, idx as u32);
            assert_eq!(task.status, Status::Enqueued);
            assert_eq!(task.kind, k);

            inserted_tasks.push(task);
        }

        let rtxn = index_scheduler.env.read_txn().unwrap();
        let mut all_tasks = Vec::new();
        for ret in index_scheduler.all_tasks.iter(&rtxn).unwrap() {
            all_tasks.push(ret.unwrap().0);
        }

        // we can't assert on the content of the tasks because there is the date and uuid that changes everytime.
        assert_smol_debug_snapshot!(all_tasks, @"[U32(0), U32(1), U32(2), U32(3), U32(4)]");

        let mut status = Vec::new();
        for ret in index_scheduler.status.iter(&rtxn).unwrap() {
            status.push(ret.unwrap());
        }

        assert_smol_debug_snapshot!(status, @"[(Enqueued, RoaringBitmap<[0, 1, 2, 3, 4]>)]");

        let mut kind = Vec::new();
        for ret in index_scheduler.kind.iter(&rtxn).unwrap() {
            kind.push(ret.unwrap());
        }

        assert_smol_debug_snapshot!(kind, @"[(DocumentAddition, RoaringBitmap<[1, 3, 4]>), (IndexCreation, RoaringBitmap<[0]>), (CancelTask, RoaringBitmap<[2]>)]");

        let mut index_tasks = Vec::new();
        for ret in index_scheduler.index_tasks.iter(&rtxn).unwrap() {
            index_tasks.push(ret.unwrap());
        }

        assert_smol_debug_snapshot!(index_tasks, @r###"[("catto", RoaringBitmap<[0, 1, 3]>), ("doggo", RoaringBitmap<[4]>)]"###);
    }

    #[test]
    fn insert_task_while_another_task_is_processing() {
        let (index_scheduler, handle) = IndexScheduler::test();

        index_scheduler.register(KindWithContent::Snapshot).unwrap();
        handle.wait_till(Breakpoint::BatchCreated);
        // while the task is processing can we register another task?
        index_scheduler.register(KindWithContent::Snapshot).unwrap();
        index_scheduler
            .register(KindWithContent::IndexDeletion {
                index_uid: S("doggos"),
            })
            .unwrap();

        let mut tasks = index_scheduler.get_tasks(Query::default()).unwrap();
        tasks.reverse();
        assert_eq!(tasks.len(), 3);
        assert_eq!(tasks[0].status, Status::Processing);
        assert_eq!(tasks[1].status, Status::Enqueued);
        assert_eq!(tasks[2].status, Status::Enqueued);
    }

    #[test]
    fn document_addition() {
        let (index_scheduler, handle) = IndexScheduler::test();

        let content = r#"
        {
            "id": 1,
            "doggo": "bob"
        }"#;

        let (uuid, mut file) = index_scheduler.create_update_file().unwrap();
        let documents_count =
            document_formats::read_json(content.as_bytes(), file.as_file_mut()).unwrap();
        index_scheduler
            .register(KindWithContent::DocumentImport {
                index_uid: S("doggos"),
                primary_key: Some(S("id")),
                method: ReplaceDocuments,
                content_file: uuid,
                documents_count,
                allow_index_creation: true,
            })
            .unwrap();
        file.persist().unwrap();

        // After registering the task we should see the update being enqueued
        let task = index_scheduler.get_tasks(Query::default()).unwrap();
        assert_json_snapshot!(task,
            { "[].enqueuedAt" => "date", "[].startedAt" => "date", "[].finishedAt" => "date", "[].duration" => "duration" }
            ,@r###"
        [
          {
            "uid": 0,
            "indexUid": "doggos",
            "status": "enqueued",
            "type": "documentAddition",
            "enqueuedAt": "date"
          }
        ]
        "###);

        handle.wait_till(Breakpoint::BatchCreated);

        // Once the task has started being batched it should be marked as processing
        let task = index_scheduler.get_tasks(Query::default()).unwrap();
        assert_json_snapshot!(task,
            { "[].enqueuedAt" => "date", "[].startedAt" => "date", "[].finishedAt" => "date", "[].duration" => "duration" }
            ,@r###"
        [
          {
            "uid": 0,
            "indexUid": "doggos",
            "status": "processing",
            "type": "documentAddition",
            "enqueuedAt": "date",
            "startedAt": "date"
          }
        ]
        "###);
        handle.wait_till(Breakpoint::AfterProcessing);

        let task = index_scheduler.get_tasks(Query::default()).unwrap();
        assert_json_snapshot!(task,
            { "[].enqueuedAt" => "date", "[].startedAt" => "date", "[].finishedAt" => "date", "[].duration" => "duration" }
            ,@r###"
        [
          {
            "uid": 0,
            "indexUid": "doggos",
            "status": "succeeded",
            "type": "documentAddition",
            "details": {
              "receivedDocuments": 1,
              "indexedDocuments": 1
            },
            "duration": "duration",
            "enqueuedAt": "date",
            "startedAt": "date",
            "finishedAt": "date"
          }
        ]
        "###);

        let doggos = index_scheduler.index("doggos").unwrap();

        let rtxn = doggos.read_txn().unwrap();
        let documents: Vec<_> = doggos
            .all_documents(&rtxn)
            .unwrap()
            .collect::<std::result::Result<_, _>>()
            .unwrap();

        assert_smol_debug_snapshot!(documents, @r###"[{"id": Number(1), "doggo": String("bob")}]"###);
    }

    #[macro_export]
    macro_rules! assert_smol_debug_snapshot {
        ($value:expr, @$snapshot:literal) => {{
            let value = format!("{:?}", $value);
            insta::assert_snapshot!(value, stringify!($value), @$snapshot);
        }};
        ($name:expr, $value:expr) => {{
            let value = format!("{:?}", $value);
            insta::assert_snapshot!(Some($name), value, stringify!($value));
        }};
        ($value:expr) => {{
            let value = format!("{:?}", $value);
            insta::assert_snapshot!($crate::_macro_support::AutoName, value, stringify!($value));
        }};
    }

    #[test]
    fn simple_new() {
        crate::IndexScheduler::test();
    }
}