pub use ipfs_sqlite_block_store::TempPin;
use ipfs_sqlite_block_store::{
    cache::{CacheTracker, InMemCacheTracker, SqliteCacheTracker},
    BlockStore, Config, Synchronous,
};
use lazy_static::lazy_static;
use libipld::{codec::References, store::StoreParams, Block, Cid, Ipld, Result};
use parking_lot::Mutex;
use prometheus::{
    core::{Collector, Desc},
    proto::MetricFamily,
    HistogramOpts, HistogramVec, IntCounterVec, IntGauge, Opts, Registry,
};
use std::{future::Future, path::PathBuf, sync::Arc, time::Duration};
use tracing::info;

use crate::executor::{Executor, JoinHandle};
use std::collections::HashSet;

/// Storage configuration.
#[derive(Clone, Debug, Eq, PartialEq)]
pub struct StorageConfig {
    /// The path to use for the block store. If it is `None` an in-memory block
    /// store will be used.
    pub path: Option<PathBuf>,
    /// The path to use for the database that persists block accesses times for
    /// the LRU cache. If this is set to 'None', access times will not be
    /// persisted but just tracked in memory.
    ///
    /// You can point this to the same file as the main block store, but this is
    /// not recommended.
    pub access_db_path: Option<PathBuf>,
    /// The target number of blocks.
    ///
    /// Up to this number, the store will retain everything even if
    /// not pinned. Once this number is exceeded, the store will run garbage
    /// collection of all unpinned blocks until the block criterion is met
    /// again.
    ///
    /// To completely disable storing of non-pinned blocks, set this to 0. Even
    /// then, the store will never delete pinned blocks.
    pub cache_size_blocks: u64,
    /// The target store size.
    ///
    /// Up to this size, the store will retain everything even if not pinned.
    /// Once this size is exceeded, the store will run garbage collection of
    /// all unpinned blocks until the size criterion is met again.
    ///
    /// The store will never delete pinned blocks.
    pub cache_size_bytes: u64,
    /// The interval at which the garbage collector is run.
    ///
    /// Note that this is implemented as delays between gcs, so it will not run
    /// exactly at this interval, but there will be some drift if gc takes
    /// long.
    pub gc_interval: Duration,
    /// The minimum number of blocks to collect in any case.
    ///
    /// Using this parameter, it is possible to guarantee a minimum rate with
    /// which the gc will be able to keep up. It is `gc_min_blocks` /
    /// `gc_interval`.
    pub gc_min_blocks: usize,
    /// The target maximum gc duration of a single garbage collector run.
    ///
    /// This can not be guaranteed, since we guarantee to collect at least
    /// `gc_min_blocks`. But as soon as this duration is exceeded, the
    /// incremental gc will stop doing additional work.
    pub gc_target_duration: Duration,
}

impl StorageConfig {
    /// Creates a new `StorageConfig`.
    pub fn new(
        path: Option<PathBuf>,
        access_db_path: Option<PathBuf>,
        cache_size: u64,
        gc_interval: Duration,
    ) -> Self {
        Self {
            path,
            access_db_path,
            cache_size_blocks: cache_size,
            cache_size_bytes: u64::MAX,
            gc_interval,
            gc_min_blocks: usize::MAX,
            gc_target_duration: Duration::new(u64::MAX, 1_000_000_000 - 1),
        }
    }
}

struct StorageServiceInner<S: StoreParams> {
    executor: Executor,
    store: Arc<Mutex<BlockStore<S>>>,
    gc_target_duration: Duration,
    gc_min_blocks: usize,
    gc_task: Option<JoinHandle<()>>,
}

impl<S: StoreParams> Drop for StorageServiceInner<S> {
    fn drop(&mut self) {
        if let Some(t) = self.gc_task.take() {
            t.abort()
        }
    }
}

#[derive(Clone)]
pub struct StorageService<S: StoreParams> {
    inner: Arc<StorageServiceInner<S>>,
}

impl<S: StoreParams> StorageService<S>
where
    Ipld: References<S::Codecs>,
{
    pub fn open(config: StorageConfig, executor: Executor) -> Result<Self> {
        let inner = StorageServiceInner::open(config, executor)?;
        Ok(Self {
            inner: Arc::new(inner),
        })
    }
}

impl<S: StoreParams> StorageServiceInner<S>
where
    Ipld: References<S::Codecs>,
{
    pub fn open(config: StorageConfig, executor: Executor) -> Result<Self> {
        let store_config = Config::default()
            .with_size_targets(config.cache_size_blocks, config.cache_size_bytes)
            .with_pragma_synchronous(Synchronous::Normal);
        let tracker: Arc<dyn CacheTracker> = if let Some(path) = config.access_db_path {
            let path = if path.is_file() {
                path
            } else {
                std::fs::create_dir_all(&path)?;
                path.join("access")
            };
            Arc::new(SqliteCacheTracker::open(&path, |access, _| Some(access))?)
        } else {
            Arc::new(InMemCacheTracker::new(|access, _| Some(access)))
        };

        let is_memory = config.path.is_none();
        // create DB connection
        let store = if let Some(path) = config.path {
            let path = if path.is_file() {
                path
            } else {
                std::fs::create_dir_all(&path)?;
                path.join("db")
            };
            BlockStore::open(path, store_config.with_cache_tracker(tracker))?
        } else {
            BlockStore::memory(store_config.with_cache_tracker(tracker))?
        };
        let store = Arc::new(Mutex::new(store));

        // spawn GC task
        let gc_interval = config.gc_interval;
        let gc_min_blocks = config.gc_min_blocks;
        let gc_target_duration = config.gc_target_duration;
        let gc_task = if is_memory {
            let gc = store.clone();
            executor.spawn(async move {
                loop {
                    futures_timer::Delay::new(gc_interval).await;
                    info!("going for gc!");
                    gc.lock()
                        .incremental_gc(gc_min_blocks, gc_target_duration)
                        .map_err(|e| {
                            tracing::warn!("failure during incremental gc: {:#}", e);
                            e
                        })
                        .ok();
                }
            })
        } else {
            let mut gc = store.lock().additional_connection()?;
            executor.spawn(async move {
                loop {
                    futures_timer::Delay::new(gc_interval).await;
                    info!("going for gc!");
                    gc.incremental_gc(gc_min_blocks, gc_target_duration)
                        .map_err(|e| {
                            tracing::warn!("failure during incremental gc: {:#}", e);
                            e
                        })
                        .ok();
                }
            })
        };
        Ok(Self {
            executor,
            gc_target_duration: config.gc_target_duration,
            gc_min_blocks: config.gc_min_blocks,
            store,
            gc_task: Some(gc_task),
        })
    }
}

impl<S: StoreParams> StorageService<S>
where
    Ipld: References<S::Codecs>,
{
    pub fn rw<F: FnOnce(&mut Batch<'_, S>) -> Result<R>, R>(
        &self,
        op: &'static str,
        f: F,
    ) -> Result<R> {
        QUERIES_TOTAL.with_label_values(&[op]).inc();
        let timer = QUERY_DURATION
            .with_label_values(&["lock_wait"])
            .start_timer();
        let mut lock = self.inner.store.lock();
        let t = timer.stop_and_record();
        if t > 1.0 {
            tracing::warn!(op, "very long storage lock wait time of {:.1}s", t);
        }
        let _timer = QUERY_DURATION.with_label_values(&[op]).start_timer();
        let mut txn = Batch(lock.transaction());
        let res = f(&mut txn);
        if res.is_ok() {
            txn.0.commit()?;
        }
        res
    }

    pub fn create_temp_pin(&self) -> Result<TempPin> {
        self.rw("create_temp_pin", |x| x.create_temp_pin())
    }

    pub fn temp_pin(
        &self,
        temp: &mut TempPin,
        iter: impl IntoIterator<Item = Cid> + Send + 'static,
    ) -> Result<()> {
        self.rw("temp_pin", |x| x.temp_pin(temp, iter))
    }

    pub fn iter(&self) -> Result<impl Iterator<Item = Cid>> {
        self.rw("iter", |x| x.iter())
    }

    pub fn contains(&self, cid: &Cid) -> Result<bool> {
        self.rw("contains", |x| x.contains(cid))
    }

    pub fn get(&self, cid: &Cid) -> Result<Option<Vec<u8>>> {
        self.rw("get", |x| x.get(cid))
    }

    pub fn insert(&self, block: Block<S>) -> Result<()> {
        self.rw("insert", |x| x.insert(block))
    }

    pub fn alias(&self, alias: &[u8], cid: Option<&Cid>) -> Result<()> {
        self.rw("alias", |x| x.alias(alias, cid))
    }

    pub fn aliases(&self) -> Result<Vec<(Vec<u8>, Cid)>> {
        self.rw("aliases", |x| x.aliases())
    }

    pub fn resolve(&self, alias: &[u8]) -> Result<Option<Cid>> {
        self.rw("resolve", |x| x.resolve(alias))
    }

    pub fn reverse_alias(&self, cid: &Cid) -> Result<Option<HashSet<Vec<u8>>>> {
        self.rw("reverse_alias", |x| x.reverse_alias(cid))
    }

    pub fn missing_blocks(&self, cid: &Cid) -> Result<Vec<Cid>> {
        self.rw("missing_blocks", |x| x.missing_blocks(cid))
    }

    pub async fn evict(&self) -> Result<()> {
        let store = self.inner.store.clone();
        let gc_min_blocks = self.inner.gc_min_blocks;
        let gc_target_duration = self.inner.gc_target_duration;
        self.inner
            .executor
            .spawn_blocking(move || {
                while !store
                    .lock()
                    .incremental_gc(gc_min_blocks, gc_target_duration)?
                {
                    tracing::trace!("x");
                }
                Ok(())
            })
            .await?
    }

    pub async fn flush(&self) -> Result<()> {
        let store = self.inner.store.clone();
        let flush = self
            .inner
            .executor
            .spawn_blocking(move || store.lock().flush());
        Ok(observe_future("flush", flush).await??)
    }

    pub fn register_metrics(&self, registry: &Registry) -> Result<()> {
        registry.register(Box::new(QUERIES_TOTAL.clone()))?;
        registry.register(Box::new(QUERY_DURATION.clone()))?;
        registry.register(Box::new(SqliteStoreCollector::new(
            self.inner.store.clone(),
        )))?;
        Ok(())
    }
}

lazy_static! {
    pub static ref QUERIES_TOTAL: IntCounterVec = IntCounterVec::new(
        Opts::new(
            "block_store_queries_total",
            "Number of block store requests labelled by type."
        ),
        &["type"],
    )
    .unwrap();
    pub static ref QUERY_DURATION: HistogramVec = HistogramVec::new(
        HistogramOpts::new(
            "block_store_query_duration",
            "Duration of store queries labelled by type.",
        )
        .buckets(vec![
            0.0001, 0.0002, 0.0005, 0.001, 0.002, 0.005, 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, 1.0, 2.0,
            5.0, 10.0
        ]),
        &["type"],
    )
    .unwrap();
}

async fn observe_future<T, F>(name: &'static str, query: F) -> Result<T>
where
    F: Future<Output = anyhow::Result<T>>,
{
    QUERIES_TOTAL.with_label_values(&[name]).inc();
    let timer = QUERY_DURATION.with_label_values(&[name]).start_timer();
    let res = query.await;
    if res.is_ok() {
        timer.observe_duration();
    } else {
        timer.stop_and_discard();
    }
    Ok(res?)
}

struct SqliteStoreCollector<S: StoreParams> {
    store: Arc<Mutex<BlockStore<S>>>,
    desc: Desc,
}

impl<S: StoreParams> Collector for SqliteStoreCollector<S>
where
    Ipld: References<S::Codecs>,
{
    fn desc(&self) -> Vec<&Desc> {
        vec![&self.desc]
    }

    fn collect(&self) -> Vec<MetricFamily> {
        let mut family = vec![];

        if let Ok(stats) = self.store.lock().get_store_stats() {
            let store_block_count =
                IntGauge::new("block_store_block_count", "Number of stored blocks").unwrap();
            store_block_count.set(stats.count() as _);
            family.push(store_block_count.collect()[0].clone());

            let store_size =
                IntGauge::new("block_store_size", "Size in bytes of stored blocks").unwrap();
            store_size.set(stats.size() as _);
            family.push(store_size.collect()[0].clone());
        }

        family
    }
}

impl<S: StoreParams> SqliteStoreCollector<S> {
    pub fn new(store: Arc<Mutex<BlockStore<S>>>) -> Self {
        let desc = Desc::new(
            "block_store_stats".into(),
            ".".into(),
            Default::default(),
            Default::default(),
        )
        .unwrap();
        Self { store, desc }
    }
}

/// A handle for performing batch operations on an ipfs storage
pub struct Batch<'a, S>(ipfs_sqlite_block_store::Transaction<'a, S>);

impl<'a, S: StoreParams> Batch<'a, S>
where
    S: StoreParams,
    Ipld: References<S::Codecs>,
{
    pub fn create_temp_pin(&mut self) -> Result<TempPin> {
        Ok(self.0.temp_pin())
    }

    pub fn temp_pin(
        &mut self,
        temp: &mut TempPin,
        iter: impl IntoIterator<Item = Cid> + Send + 'static,
    ) -> Result<()> {
        for link in iter {
            self.0.extend_temp_pin(temp, &link)?;
        }
        Ok(())
    }

    pub fn iter(&mut self) -> Result<impl Iterator<Item = Cid>> {
        let cids = self.0.get_block_cids::<Vec<Cid>>()?;
        Ok(cids.into_iter())
    }

    pub fn contains(&mut self, cid: &Cid) -> Result<bool> {
        Ok(self.0.has_block(cid)?)
    }

    pub fn get(&mut self, cid: &Cid) -> Result<Option<Vec<u8>>> {
        Ok(self.0.get_block(cid)?)
    }

    pub fn insert(&mut self, block: Block<S>) -> Result<()> {
        Ok(self.0.put_block(block, None)?)
    }

    pub fn resolve(&mut self, alias: &[u8]) -> Result<Option<Cid>> {
        Ok(self.0.resolve(alias)?)
    }

    pub fn alias(&mut self, alias: &[u8], cid: Option<&Cid>) -> Result<()> {
        Ok(self.0.alias(alias, cid)?)
    }

    pub fn aliases(&mut self) -> Result<Vec<(Vec<u8>, Cid)>> {
        Ok(self.0.aliases()?)
    }

    pub fn reverse_alias(&mut self, cid: &Cid) -> Result<Option<HashSet<Vec<u8>>>> {
        Ok(self.0.reverse_alias(cid)?)
    }

    pub fn missing_blocks(&mut self, cid: &Cid) -> Result<Vec<Cid>> {
        Ok(self.0.get_missing_blocks(cid)?)
    }
}

#[cfg(test)]
mod tests {
    use crate::executor::Executor;

    use super::*;
    use libipld::{alias, cbor::DagCborCodec, ipld, multihash::Code, store::DefaultParams};

    fn create_block(ipld: &Ipld) -> Block<DefaultParams> {
        Block::encode(DagCborCodec, Code::Blake3_256, ipld).unwrap()
    }

    macro_rules! assert_evicted {
        ($store:expr, $block:expr) => {
            assert_eq!($store.reverse_alias($block.cid()).unwrap(), None);
        };
    }

    macro_rules! assert_pinned {
        ($store:expr, $block:expr) => {
            assert_eq!(
                $store
                    .reverse_alias($block.cid())
                    .unwrap()
                    .map(|a| !a.is_empty()),
                Some(true)
            );
        };
    }

    macro_rules! assert_unpinned {
        ($store:expr, $block:expr) => {
            assert_eq!(
                $store
                    .reverse_alias($block.cid())
                    .unwrap()
                    .map(|a| !a.is_empty()),
                Some(false)
            );
        };
    }

    fn tracing_try_init() {
        tracing_subscriber::fmt()
            .with_env_filter(tracing_subscriber::EnvFilter::from_default_env())
            .try_init()
            .ok();
    }

    fn create_store() -> StorageService<DefaultParams> {
        let config = StorageConfig::new(None, None, 2, Duration::from_secs(100));
        StorageService::open(config, Executor::new()).unwrap()
    }

    #[async_std::test]
    async fn test_store_evict() {
        tracing_try_init();
        let store = create_store();
        let a = create_block(&ipld!(0));
        let b = create_block(&ipld!(1));
        let c = create_block(&ipld!(2));
        let d = create_block(&ipld!(3));
        store.insert(a.clone()).unwrap();
        store.insert(b.clone()).unwrap();
        store.flush().await.unwrap();
        store.evict().await.unwrap();
        assert_unpinned!(&store, &a);
        assert_unpinned!(&store, &b);
        store.insert(c.clone()).unwrap();
        store.flush().await.unwrap();
        store.evict().await.unwrap();
        assert_evicted!(&store, &a);
        assert_unpinned!(&store, &b);
        assert_unpinned!(&store, &c);
        store.get(b.cid()).unwrap();
        store.insert(d.clone()).unwrap();
        store.flush().await.unwrap();
        store.evict().await.unwrap();
        assert_unpinned!(&store, &b);
        assert_evicted!(&store, &c);
        assert_unpinned!(&store, &d);
    }

    #[async_std::test]
    #[allow(clippy::many_single_char_names)]
    async fn test_store_unpin() {
        tracing_try_init();
        let store = create_store();
        let a = create_block(&ipld!({ "a": [] }));
        let b = create_block(&ipld!({ "b": [a.cid()] }));
        let c = create_block(&ipld!({ "c": [a.cid()] }));
        let x = alias!(x).as_bytes().to_vec();
        let y = alias!(y).as_bytes().to_vec();
        store.insert(a.clone()).unwrap();
        store.insert(b.clone()).unwrap();
        store.insert(c.clone()).unwrap();
        store.alias(&x, Some(b.cid())).unwrap();
        store.alias(&y, Some(c.cid())).unwrap();
        store.flush().await.unwrap();
        assert_pinned!(&store, &a);
        assert_pinned!(&store, &b);
        assert_pinned!(&store, &c);
        store.alias(&x, None).unwrap();
        store.flush().await.unwrap();
        assert_pinned!(&store, &a);
        assert_unpinned!(&store, &b);
        assert_pinned!(&store, &c);
        store.alias(&y, None).unwrap();
        store.flush().await.unwrap();
        assert_unpinned!(&store, &a);
        assert_unpinned!(&store, &b);
        assert_unpinned!(&store, &c);
    }

    #[async_std::test]
    #[allow(clippy::many_single_char_names)]
    async fn test_store_unpin2() {
        tracing_try_init();
        let store = create_store();
        let a = create_block(&ipld!({ "a": [] }));
        let b = create_block(&ipld!({ "b": [a.cid()] }));
        let x = alias!(x).as_bytes().to_vec();
        let y = alias!(y).as_bytes().to_vec();
        store.insert(a.clone()).unwrap();
        store.insert(b.clone()).unwrap();
        store.alias(&x, Some(b.cid())).unwrap();
        store.alias(&y, Some(b.cid())).unwrap();
        store.flush().await.unwrap();
        assert_pinned!(&store, &a);
        assert_pinned!(&store, &b);
        store.alias(&x, None).unwrap();
        store.flush().await.unwrap();
        assert_pinned!(&store, &a);
        assert_pinned!(&store, &b);
        store.alias(&y, None).unwrap();
        store.flush().await.unwrap();
        assert_unpinned!(&store, &a);
        assert_unpinned!(&store, &b);
    }
}