use crate::{Block, BlockStore, StoreStats, TempPin};
use futures::future::BoxFuture;
use futures::prelude::*;
use libipld::Cid;
use std::{
    iter::FromIterator,
    sync::{Arc, Mutex},
    time::Duration,
};
use tracing::*;

#[derive(Clone)]
pub struct AsyncBlockStore<R> {
    inner: Arc<Mutex<BlockStore>>,
    runtime: R,
}

impl AsyncTempPin {
    fn new(alias: TempPin) -> Self {
        Self(Arc::new(alias))
    }
}

/// a temp pin that can be freely cloned and shared
#[derive(Debug, Clone)]
pub struct AsyncTempPin(Arc<TempPin>);

/// Adapter for a runtime such as tokio or async_std
pub trait RuntimeAdapter: Clone + 'static {
    /// run a blocking block of code, most likely involving IO, on a different thread.
    fn unblock<F, T>(self, f: F) -> BoxFuture<'static, anyhow::Result<T>>
    where
        F: FnOnce() -> T + Send + 'static,
        T: Send + 'static;

    /// sleep for the given duration
    fn sleep(&self, duration: Duration) -> BoxFuture<()>;
}

type AsyncResult<T> = BoxFuture<'static, crate::Result<T>>;

impl<R: RuntimeAdapter> AsyncBlockStore<R> {
    /// Wrap a block store in an asyc wrapper
    ///
    /// `runtime` A runtime adapter for your runtime of choice
    /// `store` The BlockStore to wrap
    ///
    /// returns the async store and a future that completes when the store is dropped.
    pub fn new(runtime: R, store: BlockStore) -> Self {
        Self {
            runtime,
            inner: Arc::new(Mutex::new(store)),
        }
    }

    pub fn temp_pin(&self) -> AsyncResult<AsyncTempPin> {
        self.unblock(|store| Ok(AsyncTempPin::new(store.temp_pin())))
    }

    pub fn alias(&self, name: Vec<u8>, link: Option<Cid>) -> AsyncResult<()> {
        self.unblock(move |store| store.alias(&name, link.as_ref()))
    }

    /// Resolves an alias to a cid.
    pub fn resolve(&self, name: Vec<u8>) -> AsyncResult<Option<Cid>> {
        self.unblock(move |store| store.resolve(&name))
    }

    pub fn alias_many(
        &self,
        aliases: impl IntoIterator<Item = (impl AsRef<[u8]>, Option<Cid>)> + Send + 'static,
    ) -> AsyncResult<()> {
        self.unblock(move |store| store.alias_many(aliases))
    }

    pub fn gc(&self) -> AsyncResult<()> {
        self.unblock(|store| store.gc())
    }

    pub async fn incremental_gc(
        &self,
        min_blocks: usize,
        max_duration: Duration,
    ) -> crate::Result<bool> {
        self.unblock(move |store| store.incremental_gc(min_blocks, max_duration))
            .await
    }

    pub fn incremental_delete_orphaned(
        &self,
        min_blocks: usize,
        max_duration: Duration,
    ) -> AsyncResult<bool> {
        self.unblock(move |store| store.incremental_delete_orphaned(min_blocks, max_duration))
    }

    pub fn get_block(&self, cid: Cid) -> AsyncResult<Option<Vec<u8>>> {
        self.unblock(move |store| store.get_block(&cid))
    }

    pub fn get_blocks<I: IntoIterator<Item = Cid> + Send + 'static>(
        &self,
        cids: I,
    ) -> AsyncResult<impl Iterator<Item = (Cid, Option<Vec<u8>>)>> {
        self.unblock(move |store| store.get_blocks(cids))
    }

    pub fn has_block(&self, cid: &Cid) -> AsyncResult<bool> {
        let cid = *cid;
        self.unblock(move |store| store.has_block(&cid))
    }

    pub fn has_blocks<I, O>(&self, cids: I) -> AsyncResult<O>
    where
        I: IntoIterator<Item = Cid> + Send + 'static,
        O: FromIterator<(Cid, bool)> + Send + 'static,
    {
        self.unblock(move |store| store.has_blocks(cids))
    }

    pub fn has_cid(&self, cid: Cid) -> AsyncResult<bool> {
        self.unblock(move |store| store.has_cid(&cid))
    }

    pub fn get_missing_blocks<C: FromIterator<Cid> + Send + 'static>(
        &self,
        cid: Cid,
    ) -> AsyncResult<C> {
        self.unblock(move |store| store.get_missing_blocks(&cid))
    }

    pub fn get_descendants<C: FromIterator<Cid> + Send + 'static>(
        &self,
        cid: Cid,
    ) -> AsyncResult<C> {
        self.unblock(move |store| store.get_descendants(&cid))
    }

    pub fn reverse_alias(&self, cid: Cid) -> AsyncResult<Option<Vec<Vec<u8>>>> {
        self.unblock(move |store| store.reverse_alias(&cid))
    }

    pub fn get_known_cids<C: FromIterator<Cid> + Send + 'static>(&self) -> AsyncResult<C> {
        self.unblock(move |store| store.get_known_cids())
    }

    pub fn get_block_cids<C: FromIterator<Cid> + Send + 'static>(&self) -> AsyncResult<C> {
        self.unblock(move |store| store.get_block_cids())
    }

    pub fn get_store_stats(&self) -> AsyncResult<StoreStats> {
        self.unblock(move |store| store.get_store_stats())
    }

    pub fn put_blocks<B: Block + Send + 'static>(
        &self,
        blocks: impl IntoIterator<Item = B> + Send + 'static,
        alias: Option<AsyncTempPin>,
    ) -> AsyncResult<()> {
        self.unblock(move |store| {
            let alias = alias.as_ref().map(|x| x.0.as_ref());
            store.put_blocks(blocks, alias)
        })
    }

    pub fn put_block(
        &self,
        block: impl Block + Send + 'static,
        alias: Option<&AsyncTempPin>,
    ) -> AsyncResult<()> {
        let alias = alias.cloned();
        self.unblock(move |store| {
            let alias = alias.as_ref().map(|x| x.0.as_ref());
            store.put_block(&block, alias)
        })
    }

    /// A gc loop that runs incremental gc in regular intervals
    ///
    /// Gc will run as long as this future is polled. GC is a two step process. First, the
    /// metadata of expendable non-pinned blocks will be deleted, then the actual data will
    /// be removed. This will run the first step and the second step interleaved to minimize
    /// gc interruptions.
    pub async fn gc_loop(self, config: GcConfig) -> crate::Result<()> {
        // initial delay so we don't start gc directly on startup
        self.runtime.sleep(config.interval / 2).await;
        // stop the loop as soon as we are the only thing left running
        while self.ref_count() > 1 {
            debug!("gc_loop running incremental gc");
            self.incremental_gc(config.min_blocks, config.target_duration)
                .await?;
            self.runtime.sleep(config.interval / 2).await;
            debug!("gc_loop running incremental delete orphaned");
            self.incremental_delete_orphaned(config.min_blocks, config.target_duration)
                .await?;
            self.runtime.sleep(config.interval / 2).await;
        }
        Ok(())
    }

    /// helper to give a piece of code mutable, blocking access on the store
    fn unblock<T: Send + 'static>(
        &self,
        f: impl FnOnce(&mut BlockStore) -> crate::Result<T> + Send + 'static,
    ) -> AsyncResult<T> {
        let runtime = self.runtime.clone();
        let inner = self.inner.clone();
        runtime
            .unblock(move || f(&mut inner.lock().unwrap()))
            .err_into()
            .map(|x| x.and_then(|x| x))
            .boxed()
    }
}

impl<R> AsyncBlockStore<R> {
    /// number of references to this async wrapper
    pub fn ref_count(&self) -> usize {
        Arc::strong_count(&self.inner)
    }
}

/// Configuration for the gc loop
///
/// This is done as a config struct since we might have additional parameters here in the future,
/// such as limits at which to do a full gc.
#[derive(PartialEq, Eq, Clone, Debug)]
pub struct GcConfig {
    /// interval at which gc runs
    ///
    /// 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 interval: Duration,

    /// minimum number of blocks to collect in any case
    ///
    /// Using this parameter, it is possible to guarantee a minimum rate with which gc will be
    /// able to keep up. It is min_blocks / interval.
    pub min_blocks: usize,

    /// The target maximum gc duration of a single gc.
    ///
    /// This can not be guaranteed, since we guarantee to collect at least `min_blocks`.
    /// But as soon as this duration is exceeded, the incremental gc will stop doing additional
    /// work.
    pub target_duration: Duration,
}

impl GcConfig {
    pub fn with_interval(self, interval: Duration) -> Self {
        Self { interval, ..self }
    }
}

impl Default for GcConfig {
    fn default() -> Self {
        Self {
            interval: Duration::from_secs(60),
            min_blocks: 10000,
            target_duration: Duration::from_secs(1),
        }
    }
}