// Draftsim server implementation
// TODO: implement reconnect
// TODO: persist draft rates
package main

import (
	"encoding/json"
	"errors"
	"flag"
	"io"
	"log"
	"math/rand"
	"net/http"
	"os"
	"strings"
	"sync"

	"github.com/adrg/xdg"

	"golang.org/x/net/websocket"

	"muhq.space/muhqs-game/go/draftsim/common"
	"muhq.space/muhqs-game/go/game"
)

const DEFAULT_DEADLINE = "5x"

type table struct {
	id       string
	draft    *game.Draft
	deadline common.DeadlineFunc
	lock     sync.Mutex
	rates    draftRates
	rwlock   sync.RWMutex
}

func (t *table) start() {
	packs := t.draft.PreparePacks()
	for pack := range t.draft.PacksPerPlayer() {
		for pick := range t.draft.CardsPerPack() {
			deadline := t.deadline(t.draft.PackSize() - pick + 1)
			for _, p := range t.draft.Players() {
				ctrl := p.Ctrl.(*recordingDraftCtrl)
				ctrl.ws.SetDeadline(deadline)
			}
			t.draft.DealRound(pack, pick, packs)
		}
	}
}

var tables map[string]*table

// Cummulative Average
type ca struct {
	Ca float32
	N  int
}

func (a *ca) add(x float32) {
	a.N = a.N + 1
	a.Ca = a.Ca + float32(float64(x-a.Ca)/float64(a.N))
}

func (a *ca) merge(a2 *ca) {
	a.N = a.N + a2.N
	a.Ca = a.Ca + float32(float64(a2.Ca-a.Ca)/float64(a.N))
}

type draftRates struct {
	rates map[string]*ca
	lock  sync.RWMutex
}

var rates draftRates

func (rates *draftRates) loadFrom(path string) (err error) {
	if path == "" {
		path, err = xdg.DataFile("draftsim/rates.json")
		if err != nil {
			return
		}
	}

	f, err := os.Open(path)
	if err != nil {
		return
	}
	defer f.Close()

	dec := json.NewDecoder(f)

	err = dec.Decode(&rates.rates)
	return
}

func (rates *draftRates) storeTo(path string) (err error) {
	if path == "" {
		path, err = xdg.DataFile("draftsim/rates.json")
		if err != nil {
			return
		}
	}

	f, err := os.OpenFile(path, os.O_CREATE|os.O_RDONLY|os.O_APPEND, 0x660)
	if err != nil {
		return
	}
	defer f.Close()

	enc := json.NewEncoder(f)
	err = enc.Encode(&rates.rates)

	return
}

func (r *draftRates) updateRateUnsafe(card string, rate float32) {
	if _, found := r.rates[card]; !found {
		r.rates[card] = &ca{Ca: rate, N: 1}
	} else {
		r.rates[card].add(rate)
	}
}

func (r *draftRates) updateRate(card string, rate float32) {
	r.lock.Lock()
	r.updateRateUnsafe(card, rate)
	r.lock.Unlock()

	r.lock.RLock()
	if err := r.storeTo(*ratesFile); err != nil {
		log.Fatal(err)
	}
	r.lock.RUnlock()
}

func (r *draftRates) mergeRates(r2 *draftRates) {
	r.lock.Lock()
	defer r.lock.Unlock()

	for c, v := range r2.rates {
		if a, found := r.rates[c]; !found {
			r.rates[c] = v
		} else {
			a.merge(v)
		}
	}
}

type recordingDraftCtrl struct {
	game.RWPlayerControl
	table *table
	ws    *websocket.Conn
}

func newRecordingDraftCrtl(p *game.Player, table *table, c *websocket.Conn) *recordingDraftCtrl {

	ctrl := &recordingDraftCtrl{
		RWPlayerControl: *game.NewRWPlayerControl(p, c),
		table:           table,
		ws:              c,
	}
	return ctrl
}

// Record the received draft pick.
func (ctrl *recordingDraftCtrl) RecvAction() (game.Action, error) {
	_pick, err := ctrl.RWPlayerControl.RecvAction()
	if err != nil {
		return nil, err
	}
	pick := _pick.(*game.DraftPick)
	rate := float32(pick.Pack().Size() / ctrl.table.draft.PackSize())
	ctrl.table.rates.updateRate(pick.Pick().Name, rate)
	return pick, err
}

func joinDraft(c *websocket.Conn) {
	var args common.JoinParams
	err := websocket.JSON.Receive(c, &args)
	if err != nil {
		websocket.JSON.Send(c, "failed to parse request body")
		c.Close()
		return
	}

	tableId := args.Table

	var found bool
	var t *table
	if t, found = tables[tableId]; !found {
		d, err := game.NewDraftFromDesc([]*game.Player{}, args.Desc)
		if err != nil {
			websocket.JSON.Send(c, "failed to create draft")
			c.Close()
			return
		}

		log.Println("add", args.NPlayers, "AI players")
		for range args.NPlayers {
			d.AddRandomAi()
		}

		deadline, err := common.GenDeadline(DEFAULT_DEADLINE)
		if err != nil {
			// FIXME
		}
		t = &table{
			id:       tableId,
			draft:    d,
			deadline: deadline,
		}
		// FIXME: prevent data race
		tables[tableId] = t
	}

	p := game.NewDraftPlayer(args.Name)
	p.Id = rand.Int()
	p.Ctrl = newRecordingDraftCrtl(p, t, c)

	t.lock.Lock()
	t.draft.AddPlayerReplacingAI(p)
	joinInfo := common.JoinInfo{
		Players:  t.draft.PlayerNames(),
		Desc:     t.draft.Desc(),
		Sets:     t.draft.Sets(),
		PlayerId: p.Id,
		Deadline: DEFAULT_DEADLINE,
	}
	t.lock.Unlock()

	log.Println("send join info")
	err = websocket.JSON.Send(c, joinInfo)
	if err != nil {
		log.Println("send joinInfo:", err)
		c.Close()
		return
	}

	joinNotification := game.NewJoinedPlayerNotification(p)
	for _, _p := range t.draft.Players() {
		if _p != p {
			log.Println("send join notification")
			_p.Ctrl.SendNotification(joinNotification)
		}
	}
}

func startDraft(w http.ResponseWriter, r *http.Request) {
	body, err := io.ReadAll(r.Body)
	w.Header().Set("Access-Control-Allow-Origin", "*")
	if err != nil {
		http.Error(w, "failed to read request body", 400)
	}
	tableId := string(body)
	if t, found := tables[tableId]; found {
		log.Println("starting draft", tableId)
		go func() {
			t.start()
			for _, p := range t.draft.Players() {
				p.Ctrl.(*recordingDraftCtrl).Close()
			}
			rates.mergeRates(&t.rates)
		}()
	} else {
		http.Error(w, "table not found", 404)
	}
}

func allStats(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Access-Control-Allow-Origin", "*")
	w.Header().Set("Content-Type", "application/json")
	rates.lock.RLock()
	resp, _ := json.Marshal(rates.rates)
	rates.lock.RUnlock()
	w.Write(resp)
}

func specificStats(w http.ResponseWriter, r *http.Request) {
	body, err := io.ReadAll(r.Body)
	if err != nil {
		http.Error(w, "failed to read request body", 400)
	}
	cards := string(body)

	specific := make(map[string]ca)

	rates.lock.RLock()
	for card := range strings.SplitSeq(cards, "\n") {
		if ca, found := rates.rates[card]; found {
			specific[card] = *ca
		}
	}
	rates.lock.RUnlock()

	resp, _ := json.Marshal(specific)
	w.Header().Set("Access-Control-Allow-Origin", "*")
	w.Header().Set("Content-Type", "application/json")
	w.Write(resp)
}

func cardStat(w http.ResponseWriter, r *http.Request) {
	card := r.PathValue("card")
	rates.lock.RLock()
	resp, _ := json.Marshal(rates.rates[card])
	rates.lock.RUnlock()
	w.Header().Set("Access-Control-Allow-Origin", "*")
	w.Header().Set("Content-Type", "application/json")
	w.Write(resp)
}

var ratesFile = flag.String("ratesfile", "", "file to persist the rates")

var addr = flag.String("addr", ":8080", "http service address")

func main() {
	tables = make(map[string]*table)
	rates = draftRates{rates: make(map[string]*ca)}
	flag.Parse()

	if err := rates.loadFrom(*ratesFile); err != nil && !errors.Is(err, os.ErrNotExist) {
		log.Fatal(err)
	}

	wsServer := websocket.Server{
		Handshake: func(*websocket.Config, *http.Request) error { return nil },
		Handler:   joinDraft,
	}

	http.HandleFunc("/join", wsServer.ServeHTTP)
	http.HandleFunc("POST /start", startDraft)
	http.HandleFunc("GET /stats", allStats)
	http.HandleFunc("POST /stats", specificStats)
	http.HandleFunc("GET /stats/{card}", cardStat)
	log.Println("listening on", *addr)
	if err := http.ListenAndServe(*addr, nil); err != nil {
		log.Fatal(err)
	}
}