package websockets

import (
	"context"
	"net/http"
	"sync"
	"time"

	"github.com/fasthttp/websocket"
	"github.com/google/uuid"
	json "github.com/json-iterator/go"
	"github.com/spiral/errors"
	"github.com/spiral/roadrunner/v2/common/pubsub"
	"github.com/spiral/roadrunner/v2/pkg/payload"
	phpPool "github.com/spiral/roadrunner/v2/pkg/pool"
	"github.com/spiral/roadrunner/v2/pkg/state/process"
	"github.com/spiral/roadrunner/v2/pkg/worker"
	"github.com/spiral/roadrunner/v2/plugins/broadcast"
	"github.com/spiral/roadrunner/v2/plugins/config"
	"github.com/spiral/roadrunner/v2/plugins/http/attributes"
	"github.com/spiral/roadrunner/v2/plugins/logger"
	"github.com/spiral/roadrunner/v2/plugins/server"
	"github.com/spiral/roadrunner/v2/plugins/websockets/connection"
	"github.com/spiral/roadrunner/v2/plugins/websockets/executor"
	"github.com/spiral/roadrunner/v2/plugins/websockets/pool"
	"github.com/spiral/roadrunner/v2/plugins/websockets/validator"
)

const (
	PluginName string = "websockets"

	RrMode          string = "RR_MODE"
	RrBroadcastPath string = "RR_BROADCAST_PATH"
)

type Plugin struct {
	sync.RWMutex

	// subscriber+reader interfaces
	subReader pubsub.SubReader
	// broadcaster
	broadcaster broadcast.Broadcaster

	cfg *Config
	log logger.Logger

	// global connections map
	connections sync.Map

	// GO workers pool
	workersPool *pool.WorkersPool

	wsUpgrade *websocket.Upgrader
	serveExit chan struct{}

	// workers pool
	phpPool phpPool.Pool
	// server which produces commands to the pool
	server server.Server

	// stop receiving messages
	cancel context.CancelFunc
	ctx    context.Context

	// function used to validate access to the requested resource
	accessValidator validator.AccessValidatorFn
}

func (p *Plugin) Init(cfg config.Configurer, log logger.Logger, server server.Server, b broadcast.Broadcaster) error {
	const op = errors.Op("websockets_plugin_init")
	if !cfg.Has(PluginName) {
		return errors.E(op, errors.Disabled)
	}

	err := cfg.UnmarshalKey(PluginName, &p.cfg)
	if err != nil {
		return errors.E(op, err)
	}

	err = p.cfg.InitDefault()
	if err != nil {
		return errors.E(op, err)
	}

	p.wsUpgrade = &websocket.Upgrader{
		HandshakeTimeout: time.Second * 60,
		ReadBufferSize:   1024,
		WriteBufferSize:  1024,
		CheckOrigin: func(r *http.Request) bool {
			return isOriginAllowed(r.Header.Get("Origin"), p.cfg)
		},
	}
	p.serveExit = make(chan struct{})
	p.server = server
	p.log = log
	p.broadcaster = b

	ctx, cancel := context.WithCancel(context.Background())
	p.ctx = ctx
	p.cancel = cancel
	return nil
}

func (p *Plugin) Serve() chan error {
	const op = errors.Op("websockets_plugin_serve")
	errCh := make(chan error, 1)
	// init broadcaster
	var err error
	p.subReader, err = p.broadcaster.GetDriver(p.cfg.Broker)
	if err != nil {
		errCh <- errors.E(op, err)
		return errCh
	}

	go func() {
		var err error
		p.Lock()
		defer p.Unlock()

		p.phpPool, err = p.server.NewWorkerPool(context.Background(), &phpPool.Config{
			Debug:           p.cfg.Pool.Debug,
			NumWorkers:      p.cfg.Pool.NumWorkers,
			MaxJobs:         p.cfg.Pool.MaxJobs,
			AllocateTimeout: p.cfg.Pool.AllocateTimeout,
			DestroyTimeout:  p.cfg.Pool.DestroyTimeout,
			Supervisor:      p.cfg.Pool.Supervisor,
		}, map[string]string{RrMode: "http", RrBroadcastPath: p.cfg.Path})
		if err != nil {
			errCh <- errors.E(op, err)
			return
		}

		p.accessValidator = p.defaultAccessValidator(p.phpPool)
	}()

	p.workersPool = pool.NewWorkersPool(p.subReader, &p.connections, p.log)

	// we need here only Reader part of the interface
	go func(ps pubsub.Reader) {
		for {
			data, err := ps.Next(p.ctx)
			if err != nil {
				if errors.Is(errors.TimeOut, err) {
					return
				}

				errCh <- errors.E(op, err)
				return
			}

			p.workersPool.Queue(data)
		}
	}(p.subReader)

	return errCh
}

func (p *Plugin) Stop() error {
	// close workers pool
	p.workersPool.Stop()
	// cancel context
	p.cancel()
	p.Lock()
	if p.phpPool == nil {
		p.Unlock()
		return nil
	}
	p.phpPool.Destroy(context.Background())
	p.Unlock()

	return nil
}

func (p *Plugin) Available() {}

func (p *Plugin) Name() string {
	return PluginName
}

func (p *Plugin) Middleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if r.URL.Path != p.cfg.Path {
			next.ServeHTTP(w, r)
			return
		}

		// we need to lock here, because accessValidator might not be set in the Serve func at the moment
		p.RLock()
		// before we hijacked connection, we still can write to the response headers
		val, err := p.accessValidator(r)
		p.RUnlock()
		if err != nil {
			p.log.Error("access validation")
			w.WriteHeader(400)
			return
		}

		if val.Status != http.StatusOK {
			for k, v := range val.Header {
				for i := 0; i < len(v); i++ {
					w.Header().Add(k, v[i])
				}
			}
			w.WriteHeader(val.Status)
			_, _ = w.Write(val.Body)
			return
		}

		// upgrade connection to websocket connection
		_conn, err := p.wsUpgrade.Upgrade(w, r, nil)
		if err != nil {
			// connection hijacked, do not use response.writer or request
			p.log.Error("upgrade connection", "error", err)
			return
		}

		// construct safe connection protected by mutexes
		safeConn := connection.NewConnection(_conn, p.log)
		// generate UUID from the connection
		connectionID := uuid.NewString()
		// store connection
		p.connections.Store(connectionID, safeConn)

		// Executor wraps a connection to have a safe abstraction
		e := executor.NewExecutor(safeConn, p.log, connectionID, p.subReader, p.accessValidator, r)
		p.log.Info("websocket client connected", "uuid", connectionID)

		err = e.StartCommandLoop()
		if err != nil {
			p.log.Error("command loop error, disconnecting", "error", err.Error())
			return
		}

		// when exiting - delete the connection
		p.connections.Delete(connectionID)

		// remove connection from all topics from all pub-sub drivers
		e.CleanUp()

		err = r.Body.Close()
		if err != nil {
			p.log.Error("body close", "error", err)
		}

		// close the connection on exit
		err = safeConn.Close()
		if err != nil {
			p.log.Error("connection close", "error", err)
		}

		safeConn = nil
		p.log.Info("disconnected", "connectionID", connectionID)
	})
}

// Workers returns slice with the process states for the workers
func (p *Plugin) Workers() []*process.State {
	p.RLock()
	defer p.RUnlock()

	workers := p.workers()

	ps := make([]*process.State, 0, len(workers))
	for i := 0; i < len(workers); i++ {
		state, err := process.WorkerProcessState(workers[i])
		if err != nil {
			return nil
		}
		ps = append(ps, state)
	}

	return ps
}

// internal
func (p *Plugin) workers() []worker.BaseProcess {
	return p.phpPool.Workers()
}

// Reset destroys the old pool and replaces it with new one, waiting for old pool to die
func (p *Plugin) Reset() error {
	p.Lock()
	defer p.Unlock()
	const op = errors.Op("ws_plugin_reset")
	p.log.Info("WS plugin got restart request. Restarting...")
	p.phpPool.Destroy(context.Background())
	p.phpPool = nil

	var err error
	p.phpPool, err = p.server.NewWorkerPool(context.Background(), &phpPool.Config{
		Debug:           p.cfg.Pool.Debug,
		NumWorkers:      p.cfg.Pool.NumWorkers,
		MaxJobs:         p.cfg.Pool.MaxJobs,
		AllocateTimeout: p.cfg.Pool.AllocateTimeout,
		DestroyTimeout:  p.cfg.Pool.DestroyTimeout,
		Supervisor:      p.cfg.Pool.Supervisor,
	}, map[string]string{RrMode: "http", RrBroadcastPath: p.cfg.Path})
	if err != nil {
		return errors.E(op, err)
	}

	// attach validators
	p.accessValidator = p.defaultAccessValidator(p.phpPool)

	p.log.Info("WS plugin successfully restarted")
	return nil
}

func (p *Plugin) defaultAccessValidator(pool phpPool.Pool) validator.AccessValidatorFn {
	return func(r *http.Request, topics ...string) (*validator.AccessValidator, error) {
		const op = errors.Op("access_validator")

		p.log.Debug("validation", "topics", topics)
		r = attributes.Init(r)

		// if channels len is eq to 0, we use serverValidator
		if len(topics) == 0 {
			ctx, err := validator.ServerAccessValidator(r)
			if err != nil {
				return nil, errors.E(op, err)
			}

			val, err := exec(ctx, pool)
			if err != nil {
				return nil, errors.E(err)
			}

			return val, nil
		}

		ctx, err := validator.TopicsAccessValidator(r, topics...)
		if err != nil {
			return nil, errors.E(op, err)
		}

		val, err := exec(ctx, pool)
		if err != nil {
			return nil, errors.E(op)
		}

		if val.Status != http.StatusOK {
			return val, errors.E(op, errors.Errorf("access forbidden, code: %d", val.Status))
		}

		return val, nil
	}
}

func exec(ctx []byte, pool phpPool.Pool) (*validator.AccessValidator, error) {
	const op = errors.Op("exec")
	pd := &payload.Payload{
		Context: ctx,
	}

	resp, err := pool.Exec(pd)
	if err != nil {
		return nil, errors.E(op, err)
	}

	val := &validator.AccessValidator{
		Body: resp.Body,
	}

	err = json.Unmarshal(resp.Context, val)
	if err != nil {
		return nil, errors.E(op, err)
	}

	return val, nil
}