use std::collections::{BTreeSet, HashMap};
use std::fs::File;
use std::ops::Bound;
use std::path::{Path, PathBuf};
use std::sync::atomic::AtomicUsize;
use std::sync::Arc;

use anyhow::{Context, Result};
use bytes::Bytes;
use parking_lot::{Mutex, RwLock};

use crate::block::Block;
use crate::compact::{
    CompactionController, CompactionOptions, LeveledCompactionController, LeveledCompactionOptions,
    SimpleLeveledCompactionController, SimpleLeveledCompactionOptions, TieredCompactionController,
};
use crate::iterators::merge_iterator::MergeIterator;
use crate::iterators::two_merge_iterator::TwoMergeIterator;
use crate::iterators::StorageIterator;
use crate::lsm_iterator::{FusedIterator, LsmIterator};
use crate::manifest::{Manifest, ManifestRecord};
use crate::mem_table::{map_bound, MemTable};
use crate::table::{FileObject, SsTable, SsTableBuilder, SsTableIterator};

pub type BlockCache = moka::sync::Cache<(usize, usize), Arc<Block>>;

#[derive(Clone)]
pub struct LsmStorageState {
    /// The current memtable.
    pub memtable: Arc<MemTable>,
    /// Immutable memtables, from earliest to latest.
    pub imm_memtables: Vec<Arc<MemTable>>,
    /// L0 SSTs, from earliest to latest.
    pub l0_sstables: Vec<usize>,
    /// SsTables sorted by key range; L1 - L_max for leveled compaction, or tiers for tiered
    /// compaction.
    pub levels: Vec<(usize, Vec<usize>)>,
    /// SST objects.
    pub sstables: HashMap<usize, Arc<SsTable>>,
}

impl LsmStorageState {
    fn create(options: &LsmStorageOptions) -> Self {
        let levels = match &options.compaction_options {
            CompactionOptions::Leveled(LeveledCompactionOptions { max_levels, .. })
            | CompactionOptions::Simple(SimpleLeveledCompactionOptions { max_levels, .. }) => (1
                ..=*max_levels)
                .map(|level| (level, Vec::new()))
                .collect::<Vec<_>>(),
            CompactionOptions::Tiered(_) | CompactionOptions::NoCompaction => Vec::new(),
        };
        Self {
            memtable: Arc::new(MemTable::create(0)),
            imm_memtables: Vec::new(),
            l0_sstables: Vec::new(),
            levels,
            sstables: Default::default(),
        }
    }
}

pub struct LsmStorageOptions {
    pub block_size: usize,
    pub target_sst_size: usize,
    pub num_memtable_limit: usize,
    pub compaction_options: CompactionOptions,
    pub enable_wal: bool,
}

impl LsmStorageOptions {
    pub fn default_for_week1_test() -> Self {
        Self {
            block_size: 4096,
            target_sst_size: 2 << 20,
            compaction_options: CompactionOptions::NoCompaction,
            enable_wal: false,
            num_memtable_limit: 3,
        }
    }
}

/// The storage interface of the LSM tree.
pub(crate) struct LsmStorageInner {
    pub(crate) state: Arc<RwLock<Arc<LsmStorageState>>>,
    pub(crate) state_lock: Mutex<()>,
    path: PathBuf,
    pub(crate) block_cache: Arc<BlockCache>,
    next_sst_id: AtomicUsize,
    pub(crate) options: Arc<LsmStorageOptions>,
    pub(crate) compaction_controller: CompactionController,
    pub(crate) manifest: Manifest,
}

pub struct MiniLsm {
    pub(crate) inner: Arc<LsmStorageInner>,
    compaction_notifier: crossbeam_channel::Sender<()>,
    compaction_thread: Mutex<Option<std::thread::JoinHandle<()>>>,
}

impl Drop for MiniLsm {
    fn drop(&mut self) {
        self.compaction_notifier.send(()).ok();
    }
}

impl MiniLsm {
    pub fn close(&self) -> Result<()> {
        unimplemented!()
    }

    pub fn open(path: impl AsRef<Path>, options: LsmStorageOptions) -> Result<Arc<Self>> {
        unimplemented!()
    }

    pub fn get(&self, key: &[u8]) -> Result<Option<Bytes>> {
        self.inner.get(key)
    }

    pub fn put(&self, key: &[u8], value: &[u8]) -> Result<()> {
        self.inner.put(key, value)
    }

    pub fn delete(&self, key: &[u8]) -> Result<()> {
        self.inner.delete(key)
    }

    pub fn scan(
        &self,
        lower: Bound<&[u8]>,
        upper: Bound<&[u8]>,
    ) -> Result<FusedIterator<LsmIterator>> {
        self.inner.scan(lower, upper)
    }

    pub fn force_flush(&self) -> Result<()> {
        self.inner.force_freeze_memtable()?;
        self.inner.force_flush_next_imm_memtable()
    }
}

impl LsmStorageInner {
    pub(crate) fn next_sst_id(&self) -> usize {
        self.next_sst_id
            .fetch_add(1, std::sync::atomic::Ordering::SeqCst)
    }

    pub(crate) fn open(path: impl AsRef<Path>, options: LsmStorageOptions) -> Result<Self> {
        unimplemented!()
    }

    /// Get a key from the storage. In day 7, this can be further optimized by using a bloom filter.
    pub fn get(&self, key: &[u8]) -> Result<Option<Bytes>> {
        unimplemented!()
    }

    /// Put a key-value pair into the storage by writing into the current memtable.
    pub fn put(&self, key: &[u8], value: &[u8]) -> Result<()> {
        unimplemented!()
    }

    /// Remove a key from the storage by writing an empty value.
    pub fn delete(&self, key: &[u8]) -> Result<()> {
        unimplemented!()
    }

    pub(crate) fn path_of_sst_static(path: impl AsRef<Path>, id: usize) -> PathBuf {
        path.as_ref().join(format!("{:05}.sst", id))
    }

    pub(crate) fn path_of_sst(&self, id: usize) -> PathBuf {
        Self::path_of_sst_static(&self.path, id)
    }

    pub(crate) fn path_of_wal_static(path: impl AsRef<Path>, id: usize) -> PathBuf {
        path.as_ref().join(format!("{:05}.wal", id))
    }

    pub(crate) fn path_of_wal(&self, id: usize) -> PathBuf {
        Self::path_of_wal_static(&self.path, id)
    }

    fn sync_dir(&self) -> Result<()> {
        unimplemented!()
    }

    /// Force freeze the current memetable to an immutable memtable
    pub fn force_freeze_memtable(&self) -> Result<()> {
        unimplemented!()
    }

    /// Force flush the earliest-created immutable memtable to disk
    pub fn force_flush_next_imm_memtable(&self) -> Result<()> {
        unimplemented!()
    }

    /// Create an iterator over a range of keys.
    pub fn scan(
        &self,
        lower: Bound<&[u8]>,
        upper: Bound<&[u8]>,
    ) -> Result<FusedIterator<LsmIterator>> {
        unimplemented!()
    }
}