//! Utility functions on the DBs. Mainly getter and setters.

use std::ops::Bound;

use meilisearch_types::heed::types::{DecodeIgnore, OwnedType};
use meilisearch_types::heed::{Database, RoTxn, RwTxn};
use meilisearch_types::milli::{CboRoaringBitmapCodec, BEU32};
use meilisearch_types::tasks::{Kind, KindWithContent, Status};
use roaring::{MultiOps, RoaringBitmap};
use time::OffsetDateTime;

use crate::{Error, IndexScheduler, Result, Task, TaskId, BEI128};

impl IndexScheduler {
    pub(crate) fn all_task_ids(&self, rtxn: &RoTxn) -> Result<RoaringBitmap> {
        enum_iterator::all().map(|s| self.get_status(rtxn, s)).union()
    }

    pub(crate) fn last_task_id(&self, rtxn: &RoTxn) -> Result<Option<TaskId>> {
        Ok(self.all_tasks.remap_data_type::<DecodeIgnore>().last(rtxn)?.map(|(k, _)| k.get() + 1))
    }

    pub(crate) fn next_task_id(&self, rtxn: &RoTxn) -> Result<TaskId> {
        Ok(self.last_task_id(rtxn)?.unwrap_or_default())
    }

    pub(crate) fn get_task(&self, rtxn: &RoTxn, task_id: TaskId) -> Result<Option<Task>> {
        Ok(self.all_tasks.get(rtxn, &BEU32::new(task_id))?)
    }

    /// Convert an iterator to a `Vec` of tasks. The tasks MUST exist or a
    /// `CorruptedTaskQueue` error will be throwed.
    pub(crate) fn get_existing_tasks(
        &self,
        rtxn: &RoTxn,
        tasks: impl IntoIterator<Item = TaskId>,
    ) -> Result<Vec<Task>> {
        tasks
            .into_iter()
            .map(|task_id| {
                self.get_task(rtxn, task_id).and_then(|task| task.ok_or(Error::CorruptedTaskQueue))
            })
            .collect::<Result<_>>()
    }

    pub(crate) fn update_task(&self, wtxn: &mut RwTxn, task: &Task) -> Result<()> {
        let old_task = self.get_task(wtxn, task.uid)?.ok_or(Error::CorruptedTaskQueue)?;

        debug_assert_eq!(old_task.uid, task.uid);

        if old_task == *task {
            return Ok(());
        }

        if old_task.status != task.status {
            self.update_status(wtxn, old_task.status, |bitmap| {
                bitmap.remove(task.uid);
            })?;
            self.update_status(wtxn, task.status, |bitmap| {
                bitmap.insert(task.uid);
            })?;
        }

        if old_task.kind.as_kind() != task.kind.as_kind() {
            self.update_kind(wtxn, old_task.kind.as_kind(), |bitmap| {
                bitmap.remove(task.uid);
            })?;
            self.update_kind(wtxn, task.kind.as_kind(), |bitmap| {
                bitmap.insert(task.uid);
            })?;
        }

        assert_eq!(
            old_task.enqueued_at, task.enqueued_at,
            "Cannot update a task's enqueued_at time"
        );
        if old_task.started_at != task.started_at {
            assert!(old_task.started_at.is_none(), "Cannot update a task's started_at time");
            if let Some(started_at) = task.started_at {
                insert_task_datetime(wtxn, self.started_at, started_at, task.uid)?;
            }
        }
        if old_task.finished_at != task.finished_at {
            assert!(old_task.finished_at.is_none(), "Cannot update a task's finished_at time");
            if let Some(finished_at) = task.finished_at {
                insert_task_datetime(wtxn, self.finished_at, finished_at, task.uid)?;
            }
        }

        self.all_tasks.put(wtxn, &BEU32::new(task.uid), task)?;
        Ok(())
    }

    /// Returns the whole set of tasks that belongs to this index.
    pub(crate) fn index_tasks(&self, rtxn: &RoTxn, index: &str) -> Result<RoaringBitmap> {
        Ok(self.index_tasks.get(rtxn, index)?.unwrap_or_default())
    }

    pub(crate) fn update_index(
        &self,
        wtxn: &mut RwTxn,
        index: &str,
        f: impl Fn(&mut RoaringBitmap),
    ) -> Result<()> {
        let mut tasks = self.index_tasks(wtxn, index)?;
        f(&mut tasks);
        if tasks.is_empty() {
            self.index_tasks.delete(wtxn, index)?;
        } else {
            self.index_tasks.put(wtxn, index, &tasks)?;
        }

        Ok(())
    }

    pub(crate) fn get_status(&self, rtxn: &RoTxn, status: Status) -> Result<RoaringBitmap> {
        Ok(self.status.get(rtxn, &status)?.unwrap_or_default())
    }

    pub(crate) fn put_status(
        &self,
        wtxn: &mut RwTxn,
        status: Status,
        bitmap: &RoaringBitmap,
    ) -> Result<()> {
        Ok(self.status.put(wtxn, &status, bitmap)?)
    }

    pub(crate) fn update_status(
        &self,
        wtxn: &mut RwTxn,
        status: Status,
        f: impl Fn(&mut RoaringBitmap),
    ) -> Result<()> {
        let mut tasks = self.get_status(wtxn, status)?;
        f(&mut tasks);
        self.put_status(wtxn, status, &tasks)?;

        Ok(())
    }

    pub(crate) fn get_kind(&self, rtxn: &RoTxn, kind: Kind) -> Result<RoaringBitmap> {
        Ok(self.kind.get(rtxn, &kind)?.unwrap_or_default())
    }

    pub(crate) fn put_kind(
        &self,
        wtxn: &mut RwTxn,
        kind: Kind,
        bitmap: &RoaringBitmap,
    ) -> Result<()> {
        Ok(self.kind.put(wtxn, &kind, bitmap)?)
    }

    pub(crate) fn update_kind(
        &self,
        wtxn: &mut RwTxn,
        kind: Kind,
        f: impl Fn(&mut RoaringBitmap),
    ) -> Result<()> {
        let mut tasks = self.get_kind(wtxn, kind)?;
        f(&mut tasks);
        self.put_kind(wtxn, kind, &tasks)?;

        Ok(())
    }
}

pub(crate) fn insert_task_datetime(
    wtxn: &mut RwTxn,
    database: Database<OwnedType<BEI128>, CboRoaringBitmapCodec>,
    time: OffsetDateTime,
    task_id: TaskId,
) -> Result<()> {
    let timestamp = BEI128::new(time.unix_timestamp_nanos());
    let mut task_ids = database.get(wtxn, &timestamp)?.unwrap_or_default();
    task_ids.insert(task_id);
    database.put(wtxn, &timestamp, &RoaringBitmap::from_iter([task_id]))?;
    Ok(())
}

pub(crate) fn remove_task_datetime(
    wtxn: &mut RwTxn,
    database: Database<OwnedType<BEI128>, CboRoaringBitmapCodec>,
    time: OffsetDateTime,
    task_id: TaskId,
) -> Result<()> {
    let timestamp = BEI128::new(time.unix_timestamp_nanos());
    if let Some(mut existing) = database.get(wtxn, &timestamp)? {
        existing.remove(task_id);
        if existing.is_empty() {
            database.delete(wtxn, &timestamp)?;
        } else {
            database.put(wtxn, &timestamp, &RoaringBitmap::from_iter([task_id]))?;
        }
    }

    Ok(())
}

pub(crate) fn keep_tasks_within_datetimes(
    rtxn: &RoTxn,
    tasks: &mut RoaringBitmap,
    database: Database<OwnedType<BEI128>, CboRoaringBitmapCodec>,
    after: Option<OffsetDateTime>,
    before: Option<OffsetDateTime>,
) -> Result<()> {
    let (start, end) = match (&after, &before) {
        (None, None) => return Ok(()),
        (None, Some(before)) => (Bound::Unbounded, Bound::Excluded(*before)),
        (Some(after), None) => (Bound::Excluded(*after), Bound::Unbounded),
        (Some(after), Some(before)) => (Bound::Excluded(*after), Bound::Excluded(*before)),
    };
    let mut collected_task_ids = RoaringBitmap::new();
    let start = map_bound(start, |b| BEI128::new(b.unix_timestamp_nanos()));
    let end = map_bound(end, |b| BEI128::new(b.unix_timestamp_nanos()));
    let iter = database.range(rtxn, &(start, end))?;
    for r in iter {
        let (_timestamp, task_ids) = r?;
        collected_task_ids |= task_ids;
    }
    *tasks &= collected_task_ids;
    Ok(())
}

// TODO: remove when Bound::map ( https://github.com/rust-lang/rust/issues/86026 ) is available on stable
fn map_bound<T, U>(bound: Bound<T>, map: impl FnOnce(T) -> U) -> Bound<U> {
    match bound {
        Bound::Included(x) => Bound::Included(map(x)),
        Bound::Excluded(x) => Bound::Excluded(map(x)),
        Bound::Unbounded => Bound::Unbounded,
    }
}

pub fn swap_index_uid_in_task(task: &mut Task, swap: (&str, &str)) {
    use KindWithContent as K;
    let mut index_uids = vec![];
    match &mut task.kind {
        K::DocumentAdditionOrUpdate { index_uid, .. } => index_uids.push(index_uid),
        K::DocumentDeletion { index_uid, .. } => index_uids.push(index_uid),
        K::DocumentClear { index_uid } => index_uids.push(index_uid),
        K::SettingsUpdate { index_uid, .. } => index_uids.push(index_uid),
        K::IndexDeletion { index_uid } => index_uids.push(index_uid),
        K::IndexCreation { index_uid, .. } => index_uids.push(index_uid),
        K::IndexUpdate { index_uid, .. } => index_uids.push(index_uid),
        K::IndexSwap { swaps } => {
            for (lhs, rhs) in swaps.iter_mut() {
                if lhs == swap.0 || lhs == swap.1 {
                    index_uids.push(lhs);
                }
                if rhs == swap.0 || rhs == swap.1 {
                    index_uids.push(rhs);
                }
            }
        }
        K::TaskCancelation { .. } | K::TaskDeletion { .. } | K::DumpExport { .. } | K::Snapshot => {
        }
    };
    for index_uid in index_uids {
        if index_uid == swap.0 {
            *index_uid = swap.1.to_owned();
        } else if index_uid == swap.1 {
            *index_uid = swap.0.to_owned();
        }
    }
}