use std::fmt::Debug;

pub(crate) mod rdb;

pub struct Arena;

pub trait Base {
  type Error: Debug;
  type PinnedBytes<'a>: AsRef<[u8]>;
}
pub trait Value<'a>: 'a {}

pub trait ComposableValue<'a> {}

pub trait KeyPrefix<'a, K>: Value<'a> {}

pub trait WriteBatch {
  fn size(&self) -> usize;
}

pub trait Cursor<'k, 'v, T: Table<'k, 'v, Error = Self::Error>>: Base + Sized {
  fn move_next(&mut self) -> Result<(), Self::Error>;
  fn move_prev(&mut self) -> Result<(), Self::Error>;

  fn seek_to_first(&mut self) -> Result<(), Self::Error>;
  fn seek<'a>(
    &mut self,
    key: &dyn KeyPrefix<'a, T::Key>,
    arena: &'a Arena,
  ) -> Result<(), Self::Error>;
  fn seek_before<'a>(
    &mut self,
    key: &dyn KeyPrefix<'a, T::Key>,
    arena: &'a Arena,
  ) -> Result<(), Self::Error>;
  fn seek_to_last(&mut self) -> Result<(), Self::Error>;

  fn refresh(&mut self) -> Result<(), Self::Error>;

  fn key(&'k self, arena: &'k Arena) -> Option<T::Key>;
  fn value(&'v self, arena: &'v Arena) -> Option<T::Value>;
  fn key_value<'a: 'k + 'v>(&'a self, arena: &'a Arena) -> Option<(T::Key, T::Value)>;
}

pub trait Table<'k, 'v>: Base + Sized + Clone {
  type Snapshot;
  type WriteBatch;
  type Cursor: Cursor<'k, 'v, Self, Error = Self::Error>;

  type Key: Value<'k>;
  type Value: Value<'v>;

  fn get<'this: 'v, 'a: 'k + 'v>(
    &'this self,
    snap: &Self::Snapshot,
    key: &'k Self::Key,
    arena: &'a Arena,
    pinned: &'v mut Option<Self::PinnedBytes<'this>>,
  ) -> Result<Option<Self::Value>, Self::Error>;

  fn put<'a: 'k + 'v>(
    &self,
    wb: &mut Self::WriteBatch,
    arena: &'a Arena,
    key: &'k Self::Key,
    value: &'v Self::Value,
  ) -> Result<(), Self::Error>;

  fn delete<'a: 'k>(
    &self,
    wb: &mut Self::WriteBatch,
    arena: &'a Arena,
    key: &'k Self::Key,
  ) -> Result<(), Self::Error>;

  fn cursor(&self, snap: &Self::Snapshot) -> Self::Cursor;
}

pub trait TableMerge<'k, 'v>: Table<'k, 'v> {
  type Merge: Value<'v>;

  fn merge<'a: 'k + 'v>(
    &self,
    wb: &mut Self::WriteBatch,
    arena: &'a Arena,
    key: &'k Self::Key,
    value: &'v Self::Merge,
  ) -> Result<(), Self::Error>;
}

pub trait Singleton<'v>: Base + Sized + Clone {
  type Snapshot;
  type WriteBatch;

  type Value: Value<'v>;

  fn get<'this: 'v, 'a: 'v>(
    &'this self,
    snap: &Self::Snapshot,
    arena: &'a Arena,
    pinned: &'v mut Option<Self::PinnedBytes<'this>>,
  ) -> Result<Option<Self::Value>, Self::Error>;

  fn put<'a: 'v>(
    &self,
    wb: &mut Self::WriteBatch,
    arena: &'a Arena,
    value: &'v Self::Value,
  ) -> Result<(), Self::Error>;

  fn delete(&self, wb: &mut Self::WriteBatch, arena: &Arena) -> Result<(), Self::Error>;
}

pub trait SingletonMerge<'v>: Singleton<'v> {
  type Merge: Value<'v>;

  fn merge<'a: 'v>(
    &self,
    wb: &mut Self::WriteBatch,
    arena: &'a Arena,
    value: &'v Self::Merge,
  ) -> Result<(), Self::Error>;
}

pub trait TableParams<D: Db> {
  fn params(&self) -> D::TableParams;
}

pub trait OpenTable<D: Db> {
  type Table: for<'k, 'v> Table<'k, 'v, Error = D::Error>;
  fn open(db: &D) -> Self::Table;
}

pub trait OpenSingleton<D: Db> {
  type Singleton: for<'v> Singleton<'v, Error = D::Error>;
  fn open(self, db: &D) -> Self::Singleton;
}

pub trait Db: Base + Clone {
  type Snapshot;
  type WriteBatch: WriteBatch;

  type Options;
  type TableParams;

  fn new(
    path: &std::path::Path,
    opts: &Self::Options,
    tables: &[&dyn TableParams<Self>],
  ) -> Result<Self, Self::Error>;

  fn new_read_only(
    path: &std::path::Path,
    opts: &Self::Options,
    tables: &[&dyn TableParams<Self>],
  ) -> Result<Self, Self::Error>;

  fn snapshot(&self) -> Self::Snapshot;

  fn new_write_batch(&self) -> Self::WriteBatch;
  fn commit(&self, wb: Self::WriteBatch) -> Result<(), Self::Error>;
  fn commit_no_wal(&self, wb: Self::WriteBatch) -> Result<(), Self::Error>;
}

use std::{marker::PhantomData, sync::Arc};

use higher_kinded_types as hkt;

use crate::*;

mod rocksdb {
  pub struct MultiThreaded;
  pub type DBWithThreadMode<T> = std::marker::PhantomData<T>;
  pub struct WriteBatch;
  pub type SnapshotWithThreadMode<'a, T> = std::marker::PhantomData<T>;
  pub type DBRawIteratorWithThreadMode<'a, T> = std::marker::PhantomData<T>;
  pub type Error = ();
  pub type DBPinnableSlice<'a> = &'a [u8];
  pub type BoundColumnFamily<'a> = ();
  pub type ReadOptions = ();
  pub type Options = ();
  pub type ColumnFamilyDescriptor = ();
}

// RocksDB Database Implementation:

#[derive(Clone)]
pub(crate) struct RocksDb(pub(crate) Arc<rocksdb::DBWithThreadMode<rocksdb::MultiThreaded>>);

impl WriteBatch for rocksdb::WriteBatch {
  fn size(&self) -> usize {
    0
  }
}

pub(crate) struct RocksDbSnapshot(
  rocksdb::SnapshotWithThreadMode<'static, rocksdb::DBWithThreadMode<rocksdb::MultiThreaded>>,
  RocksDb,
);

pub(crate) struct RocksDbCursor<T> {
  db: Arc<rocksdb::DBWithThreadMode<rocksdb::MultiThreaded>>,
  pub(crate) iter: rocksdb::DBRawIteratorWithThreadMode<
    'static,
    rocksdb::DBWithThreadMode<rocksdb::MultiThreaded>,
  >,
  table: PhantomData<T>,
}

impl<T> Base for RocksDbCursor<T> {
  type Error = rocksdb::Error;
  type PinnedBytes<'a> = rocksdb::DBPinnableSlice<'a>;
}

impl<'k, 'v, T: Table<'k, 'v, Error = Self::Error>> Cursor<'k, 'v, T> for RocksDbCursor<T> {
  fn move_next(&mut self) -> Result<(), Self::Error> {
    unimplemented!()
  }

  fn move_prev(&mut self) -> Result<(), Self::Error> {
    unimplemented!()
  }

  fn seek_to_first(&mut self) -> Result<(), Self::Error> {
    unimplemented!()
  }

  fn seek<'a>(
    &mut self,
    key: &dyn KeyPrefix<'a, T::Key>,
    arena: &'a Arena,
  ) -> Result<(), Self::Error> {
    unimplemented!()
  }

  fn seek_before<'a>(
    &mut self,
    key: &dyn KeyPrefix<'a, T::Key>,
    arena: &'a Arena,
  ) -> Result<(), Self::Error> {
    unimplemented!()
  }

  fn seek_to_last(&mut self) -> Result<(), Self::Error> {
    unimplemented!()
  }

  fn refresh(&mut self) -> Result<(), Self::Error> {
    unimplemented!()
  }

  fn key(&'k self, arena: &'k Arena) -> Option<T::Key> {
    unimplemented!()
  }

  fn value(&'v self, arena: &'v Arena) -> Option<T::Value> {
    unimplemented!()
  }

  fn key_value<'a: 'k + 'v>(&'a self, arena: &'a Arena) -> Option<(T::Key, T::Value)> {
    unimplemented!()
  }
}

pub(crate) struct RocksDbTable<M, K, V> {
  pub(crate) cf: Arc<rocksdb::BoundColumnFamily<'static>>,
  pub(crate) db: RocksDb,
  pub(crate) _pd: PhantomData<(M, K, V)>,
}

impl<M, K, V> Clone for RocksDbTable<M, K, V> {
  fn clone(&self) -> Self {
    Self {
      cf: self.cf.clone(),
      db: self.db.clone(),
      _pd: PhantomData,
    }
  }
}

impl<M, K, V> Base for RocksDbTable<M, K, V> {
  type Error = rocksdb::Error;
  type PinnedBytes<'a> = rocksdb::DBPinnableSlice<'a>;
}

impl<'k, 'v, M, K: for<'a> hkt::ForLt<Of<'a>: Value<'a>>, V: for<'a> hkt::ForLt<Of<'a>: Value<'a>>>
  Table<'k, 'v> for RocksDbTable<M, K, V>
{
  type Snapshot = RocksDbSnapshot;
  type WriteBatch = rocksdb::WriteBatch;
  type Cursor = RocksDbCursor<Self>;

  type Key = K::Of<'k>;
  type Value = V::Of<'v>;

  fn get<'this: 'v, 'a: 'k + 'v>(
    &'this self,
    snap: &Self::Snapshot,
    key: &'k Self::Key,
    arena: &'a Arena,
    pinned: &'v mut Option<Self::PinnedBytes<'this>>,
  ) -> Result<Option<Self::Value>, Self::Error> {
    unimplemented!()
  }

  fn put<'a: 'k + 'v>(
    &self,
    wb: &mut Self::WriteBatch,
    arena: &'a Arena,
    key: &'k Self::Key,
    value: &'v Self::Value,
  ) -> Result<(), Self::Error> {
    unimplemented!()
  }

  fn delete<'a: 'k>(
    &self,
    wb: &mut Self::WriteBatch,
    arena: &'a Arena,
    key: &'k Self::Key,
  ) -> Result<(), Self::Error> {
    unimplemented!()
  }

  fn cursor(&self, snap: &Self::Snapshot) -> Self::Cursor {
    unimplemented!()
  }
}

pub(crate) struct RocksDbSingleton<M, V> {
  pub(crate) key: &'static [u8],
  pub(crate) table: RocksDbTable<(), hkt::ForLt!(&[u8]), V>,
  pub(crate) _pd: PhantomData<M>,
}

impl<M, V> Clone for RocksDbSingleton<M, V> {
  fn clone(&self) -> Self {
    let Self {
      key,
      ref table,
      _pd,
    } = *self;
    Self {
      key,
      table: table.clone(),
      _pd,
    }
  }
}

impl<M, V> Base for RocksDbSingleton<M, V> {
  type Error = rocksdb::Error;
  type PinnedBytes<'a> = rocksdb::DBPinnableSlice<'a>;
}

impl<'v, M, V: for<'a> hkt::ForLt<Of<'a>: Value<'a>>> Singleton<'v> for RocksDbSingleton<M, V> {
  type Snapshot = RocksDbSnapshot;
  type WriteBatch = rocksdb::WriteBatch;

  type Value = V::Of<'v>;

  fn get<'this: 'v, 'a: 'v>(
    &'this self,
    snap: &Self::Snapshot,
    arena: &'a Arena,
    pinned: &'v mut Option<Self::PinnedBytes<'this>>,
  ) -> Result<Option<Self::Value>, Self::Error> {
    unimplemented!()
  }

  fn put<'a: 'v>(
    &self,
    wb: &mut Self::WriteBatch,
    arena: &'a Arena,
    value: &'v Self::Value,
  ) -> Result<(), Self::Error> {
    unimplemented!()
  }

  fn delete(&self, wb: &mut Self::WriteBatch, arena: &Arena) -> Result<(), Self::Error> {
    unimplemented!()
  }
}

impl Base for RocksDb {
  type Error = rocksdb::Error;
  type PinnedBytes<'a> = rocksdb::DBPinnableSlice<'a>;
}

impl Db for RocksDb {
  type Snapshot = RocksDbSnapshot;
  type WriteBatch = rocksdb::WriteBatch;

  type Options = rocksdb::Options;
  type TableParams = rocksdb::ColumnFamilyDescriptor;

  fn new(
    path: &std::path::Path,
    opts: &Self::Options,
    tables: &[&dyn TableParams<Self>],
  ) -> Result<Self, Self::Error> {
    unimplemented!()
  }

  fn new_read_only(
    path: &std::path::Path,
    opts: &Self::Options,
    tables: &[&dyn TableParams<Self>],
  ) -> Result<Self, Self::Error> {
    unimplemented!()
  }

  fn snapshot(&self) -> Self::Snapshot {
    unimplemented!()
  }

  fn new_write_batch(&self) -> Self::WriteBatch {
    unimplemented!()
  }

  fn commit(&self, wb: Self::WriteBatch) -> Result<(), rocksdb::Error> {
    unimplemented!()
  }

  fn commit_no_wal(&self, wb: Self::WriteBatch) -> Result<(), rocksdb::Error> {
    unimplemented!()
  }
}