use std::borrow::Cow;
use std::mem;
use std::num::NonZeroUsize;

use lru::LruCache;
use roaring::RoaringBitmap;
use smallvec::SmallVec;

use crate::update::del_add::{DelAdd, KvWriterDelAdd};
use crate::CboRoaringBitmapCodec;

pub struct SorterCacheDelAddCboRoaringBitmap<const N: usize, MF> {
    cache: LruCache<SmallVec<[u8; N]>, DelAddRoaringBitmap>,
    sorter: grenad::Sorter<MF>,
    deladd_buffer: Vec<u8>,
    cbo_buffer: Vec<u8>,
    conn: redis::Connection,
}

impl<const N: usize, MF> SorterCacheDelAddCboRoaringBitmap<N, MF> {
    pub fn new(cap: NonZeroUsize, sorter: grenad::Sorter<MF>, conn: redis::Connection) -> Self {
        SorterCacheDelAddCboRoaringBitmap {
            cache: LruCache::new(cap),
            sorter,
            deladd_buffer: Vec::new(),
            cbo_buffer: Vec::new(),
            conn,
        }
    }
}

impl<const N: usize, MF, U> SorterCacheDelAddCboRoaringBitmap<N, MF>
where
    MF: for<'a> Fn(&[u8], &[Cow<'a, [u8]>]) -> Result<Cow<'a, [u8]>, U>,
{
    pub fn insert_del_u32(&mut self, key: &[u8], n: u32) -> Result<(), grenad::Error<U>> {
        match self.cache.get_mut(key) {
            Some(DelAddRoaringBitmap { del, add: _ }) => {
                del.get_or_insert_with(RoaringBitmap::new).insert(n);
                Ok(())
            }
            None => match self.cache.push(key.into(), DelAddRoaringBitmap::new_del_u32(n)) {
                Some((key, deladd)) => self.write_entry_to_sorter(key, deladd),
                None => Ok(()),
            },
        }
    }

    pub fn insert_del(
        &mut self,
        key: &[u8],
        bitmap: RoaringBitmap,
    ) -> Result<(), grenad::Error<U>> {
        match self.cache.get_mut(key) {
            Some(DelAddRoaringBitmap { del, add: _ }) => {
                *del.get_or_insert_with(RoaringBitmap::new) |= bitmap;
                Ok(())
            }
            None => match self.cache.push(key.into(), DelAddRoaringBitmap::new_del(bitmap)) {
                Some((key, deladd)) => self.write_entry_to_sorter(key, deladd),
                None => Ok(()),
            },
        }
    }

    pub fn insert_add_u32(&mut self, key: &[u8], n: u32) -> Result<(), grenad::Error<U>> {
        match self.cache.get_mut(key) {
            Some(DelAddRoaringBitmap { del: _, add }) => {
                add.get_or_insert_with(RoaringBitmap::new).insert(n);
                Ok(())
            }
            None => match self.cache.push(key.into(), DelAddRoaringBitmap::new_add_u32(n)) {
                Some((key, deladd)) => self.write_entry_to_sorter(key, deladd),
                None => Ok(()),
            },
        }
    }

    pub fn insert_add(
        &mut self,
        key: &[u8],
        bitmap: RoaringBitmap,
    ) -> Result<(), grenad::Error<U>> {
        match self.cache.get_mut(key) {
            Some(DelAddRoaringBitmap { del: _, add }) => {
                *add.get_or_insert_with(RoaringBitmap::new) |= bitmap;
                Ok(())
            }
            None => match self.cache.push(key.into(), DelAddRoaringBitmap::new_add(bitmap)) {
                Some((key, deladd)) => self.write_entry_to_sorter(key, deladd),
                None => Ok(()),
            },
        }
    }

    pub fn insert_del_add_u32(&mut self, key: &[u8], n: u32) -> Result<(), grenad::Error<U>> {
        match self.cache.get_mut(key) {
            Some(DelAddRoaringBitmap { del, add }) => {
                del.get_or_insert_with(RoaringBitmap::new).insert(n);
                add.get_or_insert_with(RoaringBitmap::new).insert(n);
                Ok(())
            }
            None => match self.cache.push(key.into(), DelAddRoaringBitmap::new_del_add_u32(n)) {
                Some((key, deladd)) => self.write_entry_to_sorter(key, deladd),
                None => Ok(()),
            },
        }
    }

    fn write_entry_to_sorter(
        &mut self,
        key: SmallVec<[u8; N]>,
        deladd: DelAddRoaringBitmap,
    ) -> Result<(), grenad::Error<U>> {
        self.deladd_buffer.clear();
        let mut value_writer = KvWriterDelAdd::new(&mut self.deladd_buffer);
        match deladd {
            DelAddRoaringBitmap { del: Some(del), add: None } => {
                self.cbo_buffer.clear();
                CboRoaringBitmapCodec::serialize_into(&del, &mut self.cbo_buffer);
                value_writer.insert(DelAdd::Deletion, &self.cbo_buffer)?;
            }
            DelAddRoaringBitmap { del: None, add: Some(add) } => {
                self.cbo_buffer.clear();
                CboRoaringBitmapCodec::serialize_into(&add, &mut self.cbo_buffer);
                value_writer.insert(DelAdd::Addition, &self.cbo_buffer)?;
            }
            DelAddRoaringBitmap { del: Some(del), add: Some(add) } => {
                self.cbo_buffer.clear();
                CboRoaringBitmapCodec::serialize_into(&del, &mut self.cbo_buffer);
                value_writer.insert(DelAdd::Deletion, &self.cbo_buffer)?;

                self.cbo_buffer.clear();
                CboRoaringBitmapCodec::serialize_into(&add, &mut self.cbo_buffer);
                value_writer.insert(DelAdd::Addition, &self.cbo_buffer)?;
            }
            DelAddRoaringBitmap { del: None, add: None } => return Ok(()),
        }
        redis::cmd("INCR").arg(key.as_ref()).query::<usize>(&mut self.conn).unwrap();
        self.sorter.insert(key, value_writer.into_inner().unwrap())
    }

    pub fn direct_insert(&mut self, key: &[u8], val: &[u8]) -> Result<(), grenad::Error<U>> {
        self.sorter.insert(key, val)
    }

    pub fn into_sorter(mut self) -> Result<grenad::Sorter<MF>, grenad::Error<U>> {
        let default_lru = LruCache::new(NonZeroUsize::MIN);
        for (key, deladd) in mem::replace(&mut self.cache, default_lru) {
            self.write_entry_to_sorter(key, deladd)?;
        }
        Ok(self.sorter)
    }
}

pub struct DelAddRoaringBitmap {
    pub del: Option<RoaringBitmap>,
    pub add: Option<RoaringBitmap>,
}

impl DelAddRoaringBitmap {
    fn new_del_add_u32(n: u32) -> Self {
        DelAddRoaringBitmap {
            del: Some(RoaringBitmap::from([n])),
            add: Some(RoaringBitmap::from([n])),
        }
    }

    fn new_del(bitmap: RoaringBitmap) -> Self {
        DelAddRoaringBitmap { del: Some(bitmap), add: None }
    }

    fn new_del_u32(n: u32) -> Self {
        DelAddRoaringBitmap { del: Some(RoaringBitmap::from([n])), add: None }
    }

    fn new_add(bitmap: RoaringBitmap) -> Self {
        DelAddRoaringBitmap { del: None, add: Some(bitmap) }
    }

    fn new_add_u32(n: u32) -> Self {
        DelAddRoaringBitmap { del: None, add: Some(RoaringBitmap::from([n])) }
    }
}