use flaredb_proto::kvrpc::kv_cas_client::KvCasClient;
use flaredb_proto::kvrpc::kv_raw_client::KvRawClient;
use flaredb_proto::kvrpc::{
    CasRequest, DeleteRequest, GetRequest, RawDeleteRequest, RawGetRequest, RawPutRequest,
    RawScanRequest,
};
use std::collections::HashMap;
use std::sync::Arc;
use tokio::sync::Mutex;
use tonic::transport::Channel;

use flaredb_proto::pdpb::pd_client::PdClient;
use flaredb_proto::pdpb::tso_client::TsoClient;
use flaredb_proto::pdpb::{GetRegionRequest, TsoRequest};

use crate::region_cache::RegionCache;

pub struct RdbClient {
    // We need a map of addr -> Channel/Client to reuse connections
    // Or just create on fly for MVP? Connection creation is expensive.
    // Let's cache channels.
    channels: Arc<Mutex<HashMap<String, Channel>>>,
    direct_addr: Option<String>,

    // Clients for PD (fixed)
    tso_client: TsoClient<Channel>,
    pd_client: PdClient<Channel>,

    region_cache: RegionCache,
    namespace: String,
}

impl RdbClient {
    pub async fn connect_with_pd(
        _server_addr: String,
        pd_addr: String,
    ) -> Result<Self, tonic::transport::Error> {
        Self::connect_with_pd_namespace(_server_addr, pd_addr, String::new()).await
    }

    pub async fn connect_with_pd_namespace(
        _server_addr: String,
        pd_addr: String,
        namespace: impl Into<String>,
    ) -> Result<Self, tonic::transport::Error> {
        // server_addr is intentionally unused for now; once the region cache is populated we route via PD.

        let pd_ep = format!("http://{}", pd_addr);
        let pd_channel = Channel::from_shared(pd_ep).unwrap().connect().await?;

        Ok(Self {
            channels: Arc::new(Mutex::new(HashMap::new())),
            direct_addr: None,
            tso_client: TsoClient::new(pd_channel.clone()),
            pd_client: PdClient::new(pd_channel),
            region_cache: RegionCache::new(),
            namespace: namespace.into(),
        })
    }

    /// Connect directly to a single FlareDB server without PD/region lookup.
    pub async fn connect_direct(
        server_addr: String,
        namespace: impl Into<String>,
    ) -> Result<Self, tonic::transport::Error> {
        let ep = format!("http://{}", server_addr);
        let channel = Channel::from_shared(ep).unwrap().connect().await?;

        Ok(Self {
            channels: Arc::new(Mutex::new(HashMap::new())),
            direct_addr: Some(server_addr),
            tso_client: TsoClient::new(channel.clone()),
            pd_client: PdClient::new(channel),
            region_cache: RegionCache::new(),
            namespace: namespace.into(),
        })
    }

    async fn resolve_addr(&self, key: &[u8]) -> Result<String, tonic::Status> {
        if let Some(addr) = &self.direct_addr {
            return Ok(addr.clone());
        }

        if let Some(addr) = self.region_cache.get_store_addr(key).await {
            return Ok(addr);
        }

        let mut pd_c = self.pd_client.clone();
        let req = GetRegionRequest { key: key.to_vec() };
        let resp = pd_c.get_region(req).await?.into_inner();
        if let (Some(region), Some(leader)) = (resp.region, resp.leader) {
            self.region_cache.update(region, leader.clone()).await;
            Ok(leader.addr)
        } else {
            Err(tonic::Status::not_found("Region not found"))
        }
    }

    async fn get_channel(&self, addr: &str) -> Result<Channel, tonic::transport::Error> {
        let mut map = self.channels.lock().await;
        if let Some(chan) = map.get(addr) {
            return Ok(chan.clone());
        }

        let ep = format!("http://{}", addr);
        let chan = Channel::from_shared(ep).unwrap().connect().await?;
        map.insert(addr.to_string(), chan.clone());
        Ok(chan)
    }

    pub async fn get_tso(&mut self) -> Result<u64, tonic::Status> {
        let req = TsoRequest { count: 1 };
        let resp = self.tso_client.get_timestamp(req).await?.into_inner();
        Ok(resp.timestamp)
    }

    pub async fn raw_put(&mut self, key: Vec<u8>, value: Vec<u8>) -> Result<(), tonic::Status> {
        let addr = self.resolve_addr(&key).await?;
        let channel = self
            .get_channel(&addr)
            .await
            .map_err(|e| tonic::Status::internal(e.to_string()))?;
        let mut client = KvRawClient::new(channel);

        let req = RawPutRequest {
            key,
            value,
            namespace: self.namespace.clone(),
        };
        client.raw_put(req).await?;
        Ok(())
    }

    pub async fn raw_get(&mut self, key: Vec<u8>) -> Result<Option<Vec<u8>>, tonic::Status> {
        let addr = self.resolve_addr(&key).await?;
        let channel = self
            .get_channel(&addr)
            .await
            .map_err(|e| tonic::Status::internal(e.to_string()))?;
        let mut client = KvRawClient::new(channel);
        let req = RawGetRequest {
            key,
            namespace: self.namespace.clone(),
        };
        let resp = client.raw_get(req).await?.into_inner();
        if resp.found {
            Ok(Some(resp.value))
        } else {
            Ok(None)
        }
    }

    pub async fn raw_delete(&mut self, key: Vec<u8>) -> Result<bool, tonic::Status> {
        let addr = self.resolve_addr(&key).await?;
        let channel = self
            .get_channel(&addr)
            .await
            .map_err(|e| tonic::Status::internal(e.to_string()))?;
        let mut client = KvRawClient::new(channel);
        let req = RawDeleteRequest {
            key,
            namespace: self.namespace.clone(),
        };
        let resp = client.raw_delete(req).await?.into_inner();
        Ok(resp.existed)
    }

    /// Scan a range of keys in raw (eventual consistency) mode.
    ///
    /// Returns (keys, values, next_key if has_more).
    pub async fn raw_scan(
        &mut self,
        start_key: Vec<u8>,
        end_key: Vec<u8>,
        limit: u32,
    ) -> Result<(Vec<Vec<u8>>, Vec<Vec<u8>>, Option<Vec<u8>>), tonic::Status> {
        let addr = self.resolve_addr(&start_key).await?;
        let channel = self
            .get_channel(&addr)
            .await
            .map_err(|e| tonic::Status::internal(e.to_string()))?;
        let mut client = KvRawClient::new(channel);
        let req = RawScanRequest {
            start_key,
            end_key,
            limit,
            namespace: self.namespace.clone(),
        };
        let resp = client.raw_scan(req).await?.into_inner();
        let next = if resp.has_more {
            Some(resp.next_key)
        } else {
            None
        };
        Ok((resp.keys, resp.values, next))
    }

    pub async fn cas(
        &mut self,
        key: Vec<u8>,
        value: Vec<u8>,
        expected_version: u64,
    ) -> Result<(bool, u64, u64), tonic::Status> {
        let addr = self.resolve_addr(&key).await?;

        let channel = self
            .get_channel(&addr)
            .await
            .map_err(|e| tonic::Status::internal(e.to_string()))?;
        let mut client = KvCasClient::new(channel);

        let req = CasRequest {
            key,
            value,
            expected_version,
            namespace: self.namespace.clone(),
        };
        let resp = client.compare_and_swap(req).await?.into_inner();
        Ok((resp.success, resp.current_version, resp.new_version))
    }

    pub async fn cas_get(&mut self, key: Vec<u8>) -> Result<Option<(u64, Vec<u8>)>, tonic::Status> {
        let addr = self.resolve_addr(&key).await?;
        let channel = self
            .get_channel(&addr)
            .await
            .map_err(|e| tonic::Status::internal(e.to_string()))?;
        let mut client = KvCasClient::new(channel);
        let req = GetRequest {
            key,
            namespace: self.namespace.clone(),
        };
        let resp = client.get(req).await?.into_inner();
        if resp.found {
            Ok(Some((resp.version, resp.value)))
        } else {
            Ok(None)
        }
    }

    pub async fn cas_scan(
        &mut self,
        start_key: Vec<u8>,
        end_key: Vec<u8>,
        limit: u32,
    ) -> Result<(Vec<(Vec<u8>, Vec<u8>, u64)>, Option<Vec<u8>>), tonic::Status> {
        let addr = self.resolve_addr(&start_key).await?;
        let channel = self
            .get_channel(&addr)
            .await
            .map_err(|e| tonic::Status::internal(e.to_string()))?;
        let mut client = KvCasClient::new(channel);
        let req = flaredb_proto::kvrpc::ScanRequest {
            start_key,
            end_key,
            limit,
            namespace: self.namespace.clone(),
        };
        let resp = client.scan(req).await?.into_inner();
        let entries: Vec<(Vec<u8>, Vec<u8>, u64)> = resp
            .entries
            .into_iter()
            .map(|kv| (kv.key, kv.value, kv.version))
            .collect();
        let next = if resp.has_more { Some(resp.next_key) } else { None };
        Ok((entries, next))
    }

    pub async fn cas_delete(
        &mut self,
        key: Vec<u8>,
        expected_version: u64,
    ) -> Result<(bool, u64, bool), tonic::Status> {
        let addr = self.resolve_addr(&key).await?;
        let channel = self
            .get_channel(&addr)
            .await
            .map_err(|e| tonic::Status::internal(e.to_string()))?;
        let mut client = KvCasClient::new(channel);
        let req = DeleteRequest {
            key,
            expected_version,
            namespace: self.namespace.clone(),
        };
        let resp = client.delete(req).await?.into_inner();
        Ok((resp.success, resp.current_version, resp.existed))
    }
}