// Copyright 2023 Greptime Team
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use std::collections::HashMap;
use std::sync::Arc;

use futures::future::BoxFuture;
use futures::TryStreamExt;
use moka::future::Cache;
use moka::ops::compute::Op;
use table::metadata::TableId;

use crate::cache::{CacheContainer, Initializer};
use crate::error::Result;
use crate::instruction::{CacheIdent, CreateFlow, DropFlow};
use crate::key::flow::{TableFlowManager, TableFlowManagerRef};
use crate::kv_backend::KvBackendRef;
use crate::peer::Peer;
use crate::FlownodeId;

type FlownodeSet = Arc<HashMap<FlownodeId, Peer>>;

pub type TableFlownodeSetCacheRef = Arc<TableFlownodeSetCache>;

/// [TableFlownodeSetCache] caches the [TableId] to [FlownodeSet] mapping.
pub type TableFlownodeSetCache = CacheContainer<TableId, FlownodeSet, CacheIdent>;

/// Constructs a [TableFlownodeSetCache].
pub fn new_table_flownode_set_cache(
    name: String,
    cache: Cache<TableId, FlownodeSet>,
    kv_backend: KvBackendRef,
) -> TableFlownodeSetCache {
    let table_flow_manager = Arc::new(TableFlowManager::new(kv_backend));
    let init = init_factory(table_flow_manager);

    CacheContainer::new(name, cache, Box::new(invalidator), init, Box::new(filter))
}

fn init_factory(table_flow_manager: TableFlowManagerRef) -> Initializer<TableId, FlownodeSet> {
    Arc::new(move |&table_id| {
        let table_flow_manager = table_flow_manager.clone();
        Box::pin(async move {
            table_flow_manager
                .flows(table_id)
                .map_ok(|(key, value)| (key.flownode_id(), value.peer))
                .try_collect::<HashMap<_, _>>()
                .await
                // We must cache the `HashSet` even if it's empty,
                // to avoid future requests to the remote storage next time;
                // If the value is added to the remote storage,
                // we have a corresponding cache invalidation mechanism to invalidate `(Key, EmptyHashSet)`.
                .map(Arc::new)
                .map(Some)
        })
    })
}

async fn handle_create_flow(
    cache: &Cache<TableId, FlownodeSet>,
    CreateFlow {
        source_table_ids,
        flownodes: flownode_peers,
    }: &CreateFlow,
) {
    for table_id in source_table_ids {
        let entry = cache.entry(*table_id);
        entry
            .and_compute_with(
                async |entry: Option<moka::Entry<u32, Arc<HashMap<u64, _>>>>| match entry {
                    Some(entry) => {
                        let mut map = entry.into_value().as_ref().clone();
                        map.extend(flownode_peers.iter().map(|peer| (peer.id, peer.clone())));

                        Op::Put(Arc::new(map))
                    }
                    None => Op::Put(Arc::new(HashMap::from_iter(
                        flownode_peers.iter().map(|peer| (peer.id, peer.clone())),
                    ))),
                },
            )
            .await;
    }
}

async fn handle_drop_flow(
    cache: &Cache<TableId, FlownodeSet>,
    DropFlow {
        source_table_ids,
        flownode_ids,
    }: &DropFlow,
) {
    for table_id in source_table_ids {
        let entry = cache.entry(*table_id);
        entry
            .and_compute_with(
                async |entry: Option<moka::Entry<u32, Arc<HashMap<u64, _>>>>| match entry {
                    Some(entry) => {
                        let mut set = entry.into_value().as_ref().clone();
                        for flownode_id in flownode_ids {
                            set.remove(flownode_id);
                        }

                        Op::Put(Arc::new(set))
                    }
                    None => {
                        // Do nothing
                        Op::Nop
                    }
                },
            )
            .await;
    }
}

fn invalidator<'a>(
    cache: &'a Cache<TableId, FlownodeSet>,
    ident: &'a CacheIdent,
) -> BoxFuture<'a, Result<()>> {
    Box::pin(async move {
        match ident {
            CacheIdent::CreateFlow(create_flow) => handle_create_flow(cache, create_flow).await,
            CacheIdent::DropFlow(drop_flow) => handle_drop_flow(cache, drop_flow).await,
            _ => {}
        }
        Ok(())
    })
}

fn filter(ident: &CacheIdent) -> bool {
    matches!(ident, CacheIdent::CreateFlow(_) | CacheIdent::DropFlow(_))
}

#[cfg(test)]
mod tests {
    use std::collections::{BTreeMap, HashMap};
    use std::sync::Arc;

    use common_catalog::consts::{DEFAULT_CATALOG_NAME, DEFAULT_SCHEMA_NAME};
    use moka::future::CacheBuilder;
    use table::table_name::TableName;

    use crate::cache::flow::table_flownode::new_table_flownode_set_cache;
    use crate::instruction::{CacheIdent, CreateFlow, DropFlow};
    use crate::key::flow::flow_info::FlowInfoValue;
    use crate::key::flow::flow_route::FlowRouteValue;
    use crate::key::flow::FlowMetadataManager;
    use crate::kv_backend::memory::MemoryKvBackend;
    use crate::peer::Peer;

    #[tokio::test]
    async fn test_cache_empty_set() {
        let mem_kv = Arc::new(MemoryKvBackend::default());
        let cache = CacheBuilder::new(128).build();
        let cache = new_table_flownode_set_cache("test".to_string(), cache, mem_kv);
        let set = cache.get(1024).await.unwrap().unwrap();
        assert!(set.is_empty());
    }

    #[tokio::test]
    async fn test_get() {
        let mem_kv = Arc::new(MemoryKvBackend::default());
        let flownode_metadata_manager = FlowMetadataManager::new(mem_kv.clone());
        flownode_metadata_manager
            .create_flow_metadata(
                1024,
                FlowInfoValue {
                    source_table_ids: vec![1024, 1025],
                    sink_table_name: TableName {
                        catalog_name: DEFAULT_CATALOG_NAME.to_string(),
                        schema_name: DEFAULT_SCHEMA_NAME.to_string(),
                        table_name: "sink_table".to_string(),
                    },
                    flownode_ids: BTreeMap::from([(0, 1), (1, 2), (2, 3)]),
                    catalog_name: DEFAULT_CATALOG_NAME.to_string(),
                    flow_name: "my_flow".to_string(),
                    raw_sql: "sql".to_string(),
                    expire_after: Some(300),
                    comment: "comment".to_string(),
                    options: Default::default(),
                },
                (1..=3)
                    .map(|i| {
                        (
                            (i - 1) as u32,
                            FlowRouteValue {
                                peer: Peer::empty(i),
                            },
                        )
                    })
                    .collect::<Vec<_>>(),
            )
            .await
            .unwrap();
        let cache = CacheBuilder::new(128).build();
        let cache = new_table_flownode_set_cache("test".to_string(), cache, mem_kv);
        let set = cache.get(1024).await.unwrap().unwrap();
        assert_eq!(
            set.as_ref().clone(),
            HashMap::from_iter((1..=3).map(|i| { (i, Peer::empty(i),) }))
        );
        let set = cache.get(1025).await.unwrap().unwrap();
        assert_eq!(
            set.as_ref().clone(),
            HashMap::from_iter((1..=3).map(|i| { (i, Peer::empty(i),) }))
        );
        let result = cache.get(1026).await.unwrap().unwrap();
        assert_eq!(result.len(), 0);
    }

    #[tokio::test]
    async fn test_create_flow() {
        let mem_kv = Arc::new(MemoryKvBackend::default());
        let cache = CacheBuilder::new(128).build();
        let cache = new_table_flownode_set_cache("test".to_string(), cache, mem_kv);
        let ident = vec![CacheIdent::CreateFlow(CreateFlow {
            source_table_ids: vec![1024, 1025],
            flownodes: (1..=5).map(Peer::empty).collect(),
        })];
        cache.invalidate(&ident).await.unwrap();
        let set = cache.get(1024).await.unwrap().unwrap();
        assert_eq!(set.len(), 5);
        let set = cache.get(1025).await.unwrap().unwrap();
        assert_eq!(set.len(), 5);
    }

    #[tokio::test]
    async fn test_drop_flow() {
        let mem_kv = Arc::new(MemoryKvBackend::default());
        let cache = CacheBuilder::new(128).build();
        let cache = new_table_flownode_set_cache("test".to_string(), cache, mem_kv);
        let ident = vec![
            CacheIdent::CreateFlow(CreateFlow {
                source_table_ids: vec![1024, 1025],
                flownodes: (1..=5).map(Peer::empty).collect(),
            }),
            CacheIdent::CreateFlow(CreateFlow {
                source_table_ids: vec![1024, 1025],
                flownodes: (11..=12).map(Peer::empty).collect(),
            }),
        ];
        cache.invalidate(&ident).await.unwrap();
        let set = cache.get(1024).await.unwrap().unwrap();
        assert_eq!(set.len(), 7);
        let set = cache.get(1025).await.unwrap().unwrap();
        assert_eq!(set.len(), 7);

        let ident = vec![CacheIdent::DropFlow(DropFlow {
            source_table_ids: vec![1024, 1025],
            flownode_ids: vec![1, 2, 3, 4, 5],
        })];
        cache.invalidate(&ident).await.unwrap();
        let set = cache.get(1024).await.unwrap().unwrap();
        assert_eq!(
            set.as_ref().clone(),
            HashMap::from_iter((11..=12).map(|i| { (i, Peer::empty(i),) }))
        );
        let set = cache.get(1025).await.unwrap().unwrap();
        assert_eq!(
            set.as_ref().clone(),
            HashMap::from_iter((11..=12).map(|i| { (i, Peer::empty(i),) }))
        );
    }
}