package cli

import (
	"context"
	"errors"
	"fmt"
	"math"
	"net"
	"path"
	"runtime"
	"strings"
	"sync"
	"sync/atomic"
	"time"

	"git.nobla.cn/golang/kos/util/env"
	"github.com/sourcegraph/conc"
)

var (
	ctxPool sync.Pool
)

type Server struct {
	ctx            context.Context
	sequenceLocker sync.Mutex
	sequence       int64
	ctxMap         sync.Map
	waitGroup      conc.WaitGroup
	middleware     []Middleware
	router         *Router
	l              net.Listener
	exitFlag       int32
}

func (svr *Server) applyContext() *Context {
	if v := ctxPool.Get(); v != nil {
		if ctx, ok := v.(*Context); ok {
			return ctx
		}
	}
	return &Context{}
}

func (svr *Server) releaseContext(ctx *Context) {
	ctxPool.Put(ctx)
}

func (svr *Server) execute(ctx *Context, frame *Frame) (err error) {
	var (
		params map[string]string
		tokens []string
		args   []string
		r      *Router
	)
	cmd := string(frame.Data)
	tokens = strings.Fields(cmd)
	if frame.Timeout > 0 {
		childCtx, cancelFunc := context.WithTimeout(svr.ctx, time.Duration(frame.Timeout))
		ctx.setContext(childCtx)
		defer func() {
			cancelFunc()
		}()
	} else {
		ctx.setContext(svr.ctx)
	}
	if r, args, err = svr.router.Lookup(tokens); err != nil {
		if errors.Is(err, ErrNotFound) {
			err = ctx.Error(errNotFound, fmt.Sprintf("Command %s not found", cmd))
		} else {
			err = ctx.Error(errExecuteFailed, err.Error())
		}
	} else {
		if len(r.params) > len(args) {
			err = ctx.Error(errExecuteFailed, r.Usage())
			return
		}
		if len(r.params) > 0 {
			params = make(map[string]string)
			for i, s := range r.params {
				params[s] = args[i]
			}
		}
		ctx.setArgs(args)
		ctx.setParam(params)
		err = r.command.Handle(ctx)
	}
	return
}

func (svr *Server) nextSequence() int64 {
	svr.sequenceLocker.Lock()
	defer svr.sequenceLocker.Unlock()
	if svr.sequence >= math.MaxInt64 {
		svr.sequence = 1
	}
	svr.sequence++
	return svr.sequence
}

func (svr *Server) process(conn net.Conn) {
	var (
		err   error
		ctx   *Context
		frame *Frame
	)
	ctx = svr.applyContext()
	ctx.reset(svr.nextSequence(), conn)
	svr.ctxMap.Store(ctx.Id, ctx)
	defer func() {
		_ = conn.Close()
		svr.ctxMap.Delete(ctx.Id)
		svr.releaseContext(ctx)
	}()
	for {
		if frame, err = readFrame(conn); err != nil {
			break
		}
		//reset frame
		ctx.seq = frame.Seq
		switch frame.Type {
		case PacketTypeHandshake:
			if err = ctx.send(responsePayload{
				Type: PacketTypeHandshake,
				Data: &Info{
					ID:         ctx.Id,
					Name:       env.Get("VOX_NAME", ""),
					Version:    env.Get("VOX_VERSION", ""),
					OS:         runtime.GOOS,
					ServerTime: time.Now(),
					RemoteAddr: conn.RemoteAddr().String(),
				},
			}); err != nil {
				break
			}
		case PacketTypeCompleter:
			if err = ctx.send(responsePayload{
				Type: PacketTypeCompleter,
				Data: svr.router.Completer(strings.Fields(string(frame.Data))...),
			}); err != nil {
				break
			}
		case PacketTypeCommand:
			if err = svr.execute(ctx, frame); err != nil {
				break
			}
		default:
			break
		}
	}
}

func (svr *Server) serve() {
	for {
		conn, err := svr.l.Accept()
		if err != nil {
			break
		}
		svr.waitGroup.Go(func() {
			svr.process(conn)
		})
	}
}

func (svr *Server) wrapHandle(pathname, desc string, cb HandleFunc, middleware ...Middleware) Command {
	h := func(ctx *Context) (err error) {
		for i := len(svr.middleware) - 1; i >= 0; i-- {
			cb = svr.middleware[i](cb)
		}
		for i := len(middleware) - 1; i >= 0; i-- {
			cb = middleware[i](cb)
		}
		return cb(ctx)
	}
	if desc == "" {
		desc = strings.Join(strings.Split(strings.TrimPrefix(pathname, "/"), "/"), " ")
	}
	return Command{
		Path:        pathname,
		Handle:      h,
		Description: desc,
	}
}

func (svr *Server) Use(middleware ...Middleware) {
	svr.middleware = append(svr.middleware, middleware...)
}

func (svr *Server) Group(prefix string, commands []Command, middleware ...Middleware) {
	for _, cmd := range commands {
		svr.Handle(path.Join(prefix, cmd.Path), cmd.Description, cmd.Handle, middleware...)
	}
}

func (svr *Server) Handle(pathname string, desc string, cb HandleFunc, middleware ...Middleware) {
	svr.router.Handle(pathname, svr.wrapHandle(pathname, desc, cb, middleware...))
}

func (svr *Server) Serve(l net.Listener) (err error) {
	svr.l = l
	svr.Handle("/help", "Display help information", func(ctx *Context) (err error) {
		return ctx.Success(svr.router.String())
	})
	svr.serve()
	atomic.StoreInt32(&svr.exitFlag, 0)
	return
}

func (svr *Server) Shutdown() (err error) {
	if !atomic.CompareAndSwapInt32(&svr.exitFlag, 0, 1) {
		return
	}
	if svr.l != nil {
		err = svr.l.Close()
	}
	svr.ctxMap.Range(func(key, value any) bool {
		if ctx, ok := value.(*Context); ok {
			err = ctx.Close()
		}
		return true
	})
	svr.waitGroup.Wait()
	return
}

func New(ctx context.Context) *Server {
	return &Server{
		ctx:        ctx,
		router:     newRouter(""),
		middleware: make([]Middleware, 0, 10),
	}
}