package registry

import (
	"sync"
	"time"

	"github.com/google/uuid"
	"github.com/micro/go-micro/v3/logger"
	"github.com/micro/go-micro/v3/router"
)

// table is an in-memory routing table
type table struct {
	sync.RWMutex
	// routes stores service routes
	routes map[string]map[uint64]*route
	// watchers stores table watchers
	watchers map[string]*tableWatcher
}

type route struct {
	route   router.Route
	updated time.Time
}

// newtable creates a new routing table and returns it
func newTable() *table {
	return &table{
		routes:   make(map[string]map[uint64]*route),
		watchers: make(map[string]*tableWatcher),
	}
}

// pruneRoutes will prune routes older than the time specified
func (t *table) pruneRoutes(olderThan time.Duration) {
	var routes []router.Route

	t.Lock()

	// search for all the routes
	for _, routeList := range t.routes {
		for _, r := range routeList {
			// if any route is older than
			if time.Since(r.updated).Seconds() > olderThan.Seconds() {
				routes = append(routes, r.route)
			}
		}
	}

	t.Unlock()

	// delete the routes we've found
	for _, route := range routes {
		t.Delete(route)
	}
}

// deleteService removes the entire service
func (t *table) deleteService(service, network string) {
	t.Lock()
	defer t.Unlock()

	routes, ok := t.routes[service]
	if !ok {
		return
	}

	// delete the routes for the service
	for hash, rt := range routes {
		// TODO: check if this causes a problem
		// with * in the network if that is a thing
		// or blank strings
		if rt.route.Network != network {
			continue
		}
		delete(routes, hash)
	}

	// delete the map for the service if its empty
	if len(routes) == 0 {
		delete(t.routes, service)
		return
	}

	// save the routes
	t.routes[service] = routes
}

// sendEvent sends events to all subscribed watchers
func (t *table) sendEvent(e *router.Event) {
	t.RLock()
	defer t.RUnlock()

	if len(e.Id) == 0 {
		e.Id = uuid.New().String()
	}

	for _, w := range t.watchers {
		select {
		case w.resChan <- e:
		case <-w.done:
		// don't block forever
		case <-time.After(time.Second):
		}
	}
}

// Create creates new route in the routing table
func (t *table) Create(r router.Route) error {
	service := r.Service
	sum := r.Hash()

	t.Lock()
	defer t.Unlock()

	// check if there are any routes in the table for the route destination
	if _, ok := t.routes[service]; !ok {
		t.routes[service] = make(map[uint64]*route)
	}

	// add new route to the table for the route destination
	if _, ok := t.routes[service][sum]; ok {
		return router.ErrDuplicateRoute
	}

	// create the route
	t.routes[service][sum] = &route{r, time.Now()}

	if logger.V(logger.DebugLevel, logger.DefaultLogger) {
		logger.Debugf("Router emitting %s for route: %s", router.Create, r.Address)
	}

	// send a route created event
	go t.sendEvent(&router.Event{Type: router.Create, Timestamp: time.Now(), Route: r})

	return nil
}

// Delete deletes the route from the routing table
func (t *table) Delete(r router.Route) error {
	service := r.Service
	sum := r.Hash()

	t.Lock()
	defer t.Unlock()

	if _, ok := t.routes[service]; !ok {
		return router.ErrRouteNotFound
	}

	if _, ok := t.routes[service][sum]; !ok {
		return router.ErrRouteNotFound
	}

	// delete the route from the service
	delete(t.routes[service], sum)

	// delete the whole map if there are no routes left
	if len(t.routes[service]) == 0 {
		delete(t.routes, service)
	}

	if logger.V(logger.DebugLevel, logger.DefaultLogger) {
		logger.Debugf("Router emitting %s for route: %s", router.Delete, r.Address)
	}
	go t.sendEvent(&router.Event{Type: router.Delete, Timestamp: time.Now(), Route: r})

	return nil
}

// Update updates routing table with the new route
func (t *table) Update(r router.Route) error {
	service := r.Service
	sum := r.Hash()

	t.Lock()
	defer t.Unlock()

	// check if the route destination has any routes in the table
	if _, ok := t.routes[service]; !ok {
		t.routes[service] = make(map[uint64]*route)
	}

	if _, ok := t.routes[service][sum]; !ok {
		// update the route
		t.routes[service][sum] = &route{r, time.Now()}

		if logger.V(logger.DebugLevel, logger.DefaultLogger) {
			logger.Debugf("Router emitting %s for route: %s", router.Update, r.Address)
		}
		go t.sendEvent(&router.Event{Type: router.Update, Timestamp: time.Now(), Route: r})
		return nil
	}

	// just update the route, but dont emit Update event
	t.routes[service][sum] = &route{r, time.Now()}

	return nil
}

// Read entries from the table
func (t *table) Read(opts ...router.ReadOption) ([]router.Route, error) {
	var options router.ReadOptions
	for _, o := range opts {
		o(&options)
	}

	t.RLock()
	defer t.RUnlock()

	var routes []router.Route

	// get the routes based on options passed
	if len(options.Service) > 0 {
		routeMap, ok := t.routes[options.Service]
		if !ok {
			return nil, router.ErrRouteNotFound
		}
		for _, rt := range routeMap {
			routes = append(routes, rt.route)
		}
		return routes, nil
	}

	// otherwise get all routes
	for _, serviceRoutes := range t.routes {
		for _, rt := range serviceRoutes {
			routes = append(routes, rt.route)
		}
	}

	return routes, nil
}

// Watch returns routing table entry watcher
func (t *table) Watch(opts ...router.WatchOption) (router.Watcher, error) {
	// by default watch everything
	wopts := router.WatchOptions{
		Service: "*",
	}

	for _, o := range opts {
		o(&wopts)
	}

	w := &tableWatcher{
		id:      uuid.New().String(),
		opts:    wopts,
		resChan: make(chan *router.Event, 10),
		done:    make(chan struct{}),
	}

	// when the watcher is stopped delete it
	go func() {
		<-w.done
		t.Lock()
		delete(t.watchers, w.id)
		t.Unlock()
	}()

	// save the watcher
	t.Lock()
	t.watchers[w.id] = w
	t.Unlock()

	return w, nil
}