// Author: simon (ynwdlxm@163.com)
// Date: 2025/9/12 13:24
// Desc: Handling RESP protocol

package handler

import (
	"context"
	"errors"
	"io"
	"net"
	"strings"
	"sync"

	"github.com/runningwater/go-redis/database"
	dbface "github.com/runningwater/go-redis/interface/database"
	"github.com/runningwater/go-redis/lib/logger"
	"github.com/runningwater/go-redis/lib/sync/atomic"
	"github.com/runningwater/go-redis/resp/connection"
	"github.com/runningwater/go-redis/resp/parser"
	"github.com/runningwater/go-redis/resp/reply"
)

// RespHandler handles client connections and RESP protocol
type RespHandler struct {
	activeConn sync.Map
	db         dbface.Database
	closing    atomic.Boolean
}

// NewHandler creates a new RespHandler
func NewHandler() *RespHandler {
	return &RespHandler{
		// db: database.NewEchoDatabase(),
		db: database.NewDatabase(),
	}
}

// Handle processes client connections
func (r *RespHandler) Handle(ctx context.Context, conn net.Conn) {
	if r.closing.Get() {
		_ = conn.Close()
		return
	}
	logger.Info("new connection from ", conn.RemoteAddr().String())
	client := connection.NewConnection(conn)
	r.activeConn.Store(client, struct{}{})

	// Parse data
	ch := parser.ParseStream(conn)
	for payload := range ch {
		logger.Info("received channel data: ", payload)
		// error
		if payload.Err != nil {
			if errors.Is(payload.Err, io.EOF) ||
				errors.Is(payload.Err, io.ErrUnexpectedEOF) ||
				strings.Contains(payload.Err.Error(), "use of closed network connection") {
				r.closeClient(client)
				logger.Info("connection closed: ", client.RemoteAddr().String())
				return
			}
			// Protocol error
			logger.Error("protocol error: ", payload.Err.Error())
			errReply := reply.NewErrReply(payload.Err.Error())

			err := client.Write(errReply.ToBytes())
			if err != nil {
				r.closeClient(client)
				logger.Error("client.Write:", err.Error())
				return
			}
			continue
		}

		// exec
		if payload.Data == nil {
			logger.Error("empty payload")
			continue
		}
		bulkReply, ok := payload.Data.(*reply.MultiBulkReply)
		if !ok {
			logger.Error("require multi bulk reply")
			continue
		}
		// Command execution
		execResult := r.db.Exec(client, bulkReply.Args)
		if execResult == nil {
			execResult = reply.NewUnknownErrReply("aa")
		}
		// Return result
		logger.Info("exec result: ", execResult)

		_ = client.Write(execResult.ToBytes())

	} // for end
}

// Close shuts down the RespHandler and releases resources
// This function closes all active connections and the database connection
// Return value: error - Error information for the close operation, currently always returns nil
func (r *RespHandler) Close() error {
	logger.Info("handler shutting down...")
	r.closing.Set(true)

	// Iterate through all active connections and close them
	r.activeConn.Range(
		func(key, value any) bool {
			client := key.(*connection.Connection)
			_ = client.Close()
			return true
		})

	// Close database connection
	r.db.Close()

	return nil
}

// closeClient closes a client connection
// Parameters:
//
//	client *connection.Connection - The client connection object to close
func (r *RespHandler) closeClient(client *connection.Connection) {
	_ = client.Close()
	r.db.AfterClientClose(client)
	r.activeConn.Delete(client)
}