package cluster

import (
	"context"
	"io"
	"sync"
	"time"

	"github.com/hashicorp/raft"
	"gitlink.org.cn/cloudream/common/utils/serder"
	"gitlink.org.cn/cloudream/jcs-pub/common/ecode"
	"gitlink.org.cn/cloudream/jcs-pub/common/pkgs/rpc"
	clirpc "gitlink.org.cn/cloudream/jcs-pub/common/pkgs/rpc/client"
)

const (
	CmdAppendEntries  = "AppendEntries"
	CmdRequestVote    = "RequestVote"
	CmdRequestPreVote = "RequestPreVote"
	CmdTimeoutNow     = "TimeoutNow"
)

type Transport struct {
	localAddr       string
	shutdownCh      chan any
	shutdownLock    sync.Mutex
	shutdown        bool
	consumeCh       chan raft.RPC
	cliPoolCfg      clirpc.PoolConfig
	cliPools        map[raft.ServerAddress]*clirpc.Pool
	poolLock        sync.Mutex
	heartbeatFn     func(raft.RPC)
	heartbeatFnLock sync.Mutex
}

func NewTransport(localAddr string, cliPoolCfg clirpc.PoolConfig) *Transport {
	return &Transport{
		localAddr:   localAddr,
		shutdownCh:  make(chan any),
		consumeCh:   make(chan raft.RPC),
		cliPoolCfg:  cliPoolCfg,
		cliPools:    make(map[raft.ServerAddress]*clirpc.Pool),
		heartbeatFn: nil,
	}
}

func (t *Transport) Close() {
	t.shutdownLock.Lock()
	defer t.shutdownLock.Unlock()

	if !t.shutdown {
		close(t.shutdownCh)
		t.shutdown = true
	}
}

func (n *Transport) IsClosed() bool {
	select {
	case <-n.shutdownCh:
		return true
	default:
		return false
	}
}

func (t *Transport) Consumer() <-chan raft.RPC {
	return t.consumeCh
}

func (t *Transport) LocalAddr() raft.ServerAddress {
	return raft.ServerAddress(t.localAddr)
}

func (t *Transport) AppendEntriesPipeline(id raft.ServerID, target raft.ServerAddress) (raft.AppendPipeline, error) {
	t.poolLock.Lock()
	defer t.poolLock.Unlock()

	pool := t.cliPools[target]
	if pool == nil {
		cfg := t.cliPoolCfg
		cfg.Address = string(target)
		pool = clirpc.NewPool(cfg)
		t.cliPools[target] = pool
	}

	cli := pool.Get()
	return &AppendPipeline{
		cli:        cli,
		consumerCh: make(chan raft.AppendFuture),
		done:       make(chan any),
	}, nil
}

func (t *Transport) AppendEntries(id raft.ServerID, target raft.ServerAddress, args *raft.AppendEntriesRequest, resp *raft.AppendEntriesResponse) error {
	cli := t.getCli(target)

	reqData, err := serder.ObjectToJSON(args)
	if err != nil {
		return err
	}

	r, cerr := cli.ClusterRaftRPC(context.Background(), &clirpc.ClusterRaftRPC{
		Type: CmdAppendEntries,
		Data: string(reqData),
	})
	if cerr != nil {
		return cerr.ToError()
	}

	err = serder.JSONToObject([]byte(r.Data), resp)
	if err != nil {
		return err
	}

	return nil
}

func (t *Transport) RequestVote(id raft.ServerID, target raft.ServerAddress, args *raft.RequestVoteRequest, resp *raft.RequestVoteResponse) error {
	cli := t.getCli(target)

	reqData, err := serder.ObjectToJSON(args)
	if err != nil {
		return err
	}

	r, cerr := cli.ClusterRaftRPC(context.Background(), &clirpc.ClusterRaftRPC{
		Type: CmdRequestVote,
		Data: string(reqData),
	})
	if cerr != nil {
		return cerr.ToError()
	}

	err = serder.JSONToObject([]byte(r.Data), resp)
	if err != nil {
		return err
	}

	return nil
}

func (t *Transport) RequestPreVote(id raft.ServerID, target raft.ServerAddress, args *raft.RequestPreVoteRequest, resp *raft.RequestPreVoteResponse) error {
	cli := t.getCli(target)

	reqData, err := serder.ObjectToJSON(args)
	if err != nil {
		return err
	}

	r, cerr := cli.ClusterRaftRPC(context.Background(), &clirpc.ClusterRaftRPC{
		Type: CmdRequestPreVote,
		Data: string(reqData),
	})
	if cerr != nil {
		return cerr.ToError()
	}

	err = serder.JSONToObject([]byte(r.Data), resp)
	if err != nil {
		return err
	}

	return nil
}

func (t *Transport) InstallSnapshot(id raft.ServerID, target raft.ServerAddress, args *raft.InstallSnapshotRequest, resp *raft.InstallSnapshotResponse, data io.Reader) error {
	cli := t.getCli(target)
	r, cerr := cli.ClusterRaftInstallSnapshot(context.Background(), &clirpc.ClusterRaftInstallSnapshot{
		Args: args,
		Data: data,
	})
	if cerr != nil {
		return cerr.ToError()
	}

	*resp = *r.Resp
	return nil
}

func (t *Transport) EncodePeer(id raft.ServerID, addr raft.ServerAddress) []byte {
	return []byte(addr)
}
func (t *Transport) DecodePeer(data []byte) raft.ServerAddress {
	return raft.ServerAddress(string(data))
}
func (t *Transport) SetHeartbeatHandler(cb func(rpc raft.RPC)) {
	t.heartbeatFnLock.Lock()
	defer t.heartbeatFnLock.Unlock()
	t.heartbeatFn = cb
}
func (t *Transport) TimeoutNow(id raft.ServerID, target raft.ServerAddress, args *raft.TimeoutNowRequest, resp *raft.TimeoutNowResponse) error {
	cli := t.getCli(target)

	reqData, err := serder.ObjectToJSON(args)
	if err != nil {
		return err
	}

	r, cerr := cli.ClusterRaftRPC(context.Background(), &clirpc.ClusterRaftRPC{
		Type: CmdTimeoutNow,
		Data: string(reqData),
	})
	if cerr != nil {
		return cerr.ToError()
	}

	err = serder.JSONToObject([]byte(r.Data), resp)
	if err != nil {
		return err
	}

	return nil
}

func (t *Transport) OnRPC(req *clirpc.ClusterRaftRPC) (*clirpc.ClusterRaftRPCResp, *rpc.CodeError) {
	respChan := make(chan raft.RPCResponse, 1)
	rp := raft.RPC{
		RespChan: respChan,
	}

	isHeartbeat := false

	switch req.Type {
	case CmdAppendEntries:
		var r raft.AppendEntriesRequest
		err := serder.JSONToObject([]byte(req.Data), &r)
		if err != nil {
			return nil, rpc.Failed(ecode.OperationFailed, err.Error())
		}
		rp.Command = &r

		leaderAddr := r.RPCHeader.Addr

		// Check if this is a heartbeat
		if r.Term != 0 && leaderAddr != nil &&
			r.PrevLogEntry == 0 && r.PrevLogTerm == 0 &&
			len(r.Entries) == 0 && r.LeaderCommitIndex == 0 {
			isHeartbeat = true
		}

	case CmdRequestVote:
		var r raft.RequestVoteRequest
		err := serder.JSONToObject([]byte(req.Data), &r)
		if err != nil {
			return nil, rpc.Failed(ecode.OperationFailed, err.Error())
		}
		rp.Command = &r

	case CmdRequestPreVote:
		var r raft.RequestPreVoteRequest
		err := serder.JSONToObject([]byte(req.Data), &r)
		if err != nil {
			return nil, rpc.Failed(ecode.OperationFailed, err.Error())
		}
		rp.Command = &r

	case CmdTimeoutNow:
		var r raft.TimeoutNowRequest
		err := serder.JSONToObject([]byte(req.Data), &r)
		if err != nil {
			return nil, rpc.Failed(ecode.OperationFailed, err.Error())
		}
		rp.Command = &r
	}

	if isHeartbeat {
		t.heartbeatFnLock.Lock()
		fn := t.heartbeatFn
		t.heartbeatFnLock.Unlock()

		if fn != nil {
			fn(rp)
			goto RESP
		}
	}

	// Dispatch the RPC
	select {
	case t.consumeCh <- rp:
	case <-t.shutdownCh:
		return nil, rpc.Failed(ecode.OperationFailed, raft.ErrTransportShutdown.Error())
	}

	// Wait for response
RESP:
	select {
	case resp := <-respChan:
		if resp.Error != nil {
			return nil, rpc.Failed(ecode.OperationFailed, resp.Error.Error())
		}

		data, err := serder.ObjectToJSON(resp.Response)
		if err != nil {
			return nil, rpc.Failed(ecode.OperationFailed, err.Error())
		}

		return &clirpc.ClusterRaftRPCResp{
			Data: string(data),
		}, nil

	case <-t.shutdownCh:
		return nil, rpc.Failed(ecode.OperationFailed, raft.ErrTransportShutdown.Error())
	}
}

func (t *Transport) OnInstallSnapshot(req *clirpc.ClusterRaftInstallSnapshot) (*clirpc.ClusterRaftInstallSnapshotResp, *rpc.CodeError) {
	respChan := make(chan raft.RPCResponse, 1)
	rp := raft.RPC{
		Command:  req.Args,
		Reader:   req.Data,
		RespChan: respChan,
	}

	select {
	case t.consumeCh <- rp:
	case <-t.shutdownCh:
		return nil, rpc.Failed(ecode.OperationFailed, raft.ErrTransportShutdown.Error())
	}

	select {
	case resp := <-respChan:
		if resp.Error != nil {
			return nil, rpc.Failed(ecode.OperationFailed, resp.Error.Error())
		}

		return &clirpc.ClusterRaftInstallSnapshotResp{
			Resp: resp.Response.(*raft.InstallSnapshotResponse),
		}, nil

	case <-t.shutdownCh:
		return nil, rpc.Failed(ecode.OperationFailed, raft.ErrTransportShutdown.Error())
	}
}

func (t *Transport) getCli(target raft.ServerAddress) *clirpc.PoolClient {
	t.poolLock.Lock()
	defer t.poolLock.Unlock()
	pool := t.cliPools[target]
	if pool == nil {
		cfg := t.cliPoolCfg
		cfg.Address = string(target)
		pool = clirpc.NewPool(cfg)
		t.cliPools[target] = pool
	}

	return pool.Get()
}

var _ raft.Transport = (*Transport)(nil)
var _ raft.WithPreVote = (*Transport)(nil)

type AppendPipeline struct {
	cli        *clirpc.PoolClient
	consumerCh chan raft.AppendFuture
	done       chan any
	closeLock  sync.Mutex
}

func (c *AppendPipeline) AppendEntries(args *raft.AppendEntriesRequest, resp *raft.AppendEntriesResponse) (raft.AppendFuture, error) {
	reqData, err := serder.ObjectToJSON(args)
	if err != nil {
		return nil, err
	}

	startTime := time.Now()
	r, cerr := c.cli.ClusterRaftRPC(context.Background(), &clirpc.ClusterRaftRPC{
		Type: CmdAppendEntries,
		Data: string(reqData),
	})
	if cerr != nil {
		return nil, cerr.ToError()
	}

	err = serder.JSONToObject([]byte(r.Data), resp)
	if err != nil {
		return nil, err
	}

	f := &appendFuture{
		startTime: startTime,
		req:       args,
		resp:      resp,
	}

	select {
	case c.consumerCh <- f:
		return f, nil

	case <-c.done:
		return nil, raft.ErrPipelineShutdown
	}
}

func (c *AppendPipeline) Consumer() <-chan raft.AppendFuture {
	return c.consumerCh
}

func (c *AppendPipeline) Close() error {
	c.closeLock.Lock()
	defer c.closeLock.Unlock()

	if c.done == nil {
		return nil
	}

	close(c.done)
	c.done = nil
	c.cli.Release()
	return nil
}

var _ raft.AppendPipeline = (*AppendPipeline)(nil)

type appendFuture struct {
	startTime time.Time
	req       *raft.AppendEntriesRequest
	resp      *raft.AppendEntriesResponse
}

func (f *appendFuture) Error() error {
	return nil
}

func (f *appendFuture) Start() time.Time {
	return f.startTime
}

func (f *appendFuture) Request() *raft.AppendEntriesRequest {
	return f.req
}

func (f *appendFuture) Response() *raft.AppendEntriesResponse {
	return f.resp
}