package draftbot

import (
	"errors"
	"fmt"
	"math"
	"math/rand"

	room "git.fromouter.space/mcg/cardgage/room/api"

	"git.fromouter.space/mcg/draft"
	"git.fromouter.space/mcg/draft/mlp"
	"git.fromouter.space/mcg/draftbot/bot"
)

// Session-related errors
var (
	ErrTooManyPlayers   = errors.New("too many players")
	ErrNotEnoughPlayers = errors.New("not enough players")
)

type session struct {
	Options DraftOptions
	Players map[string]*draft.Player
	Bots    []*bot.Bot
	Pod     *draft.Pod

	// State management variables
	started bool // Has the draft started already?

	// Channels for communication while the session is running
	messages chan room.Message
	exit     chan bool
}

// Types of drafts
const (
	DraftBlock   = "block"
	DraftSet     = "set"
	DraftCube    = "cube"
	DraftI8PCube = "i8pcube"
)

// Ways in which players can be positioned along the draft pod
const (
	PosRandom = "random" // Place players randomly
	PosEven   = "even"   // Place players spaced as evenly as possible
)

// SessionOptions is the data contained in a create session request
type SessionOptions struct {
	Players int          `json:"players"`
	Options DraftOptions `json:"options"`
}

// DraftOptions are the options needed for a draft session
type DraftOptions struct {
	Type        string `json:"type"`
	Positioning string `json:"positioning"`

	// Block draft properties
	Block mlp.BlockID `json:"block,omitempty"`

	// Set draft properties
	Set mlp.SetID `json:"set,omitempty"`

	// Cube draft properties
	CubeURL  string `json:"cube_url,omitempty"`
	PackSize int    `json:"pack_size,omitempty"`

	// I8PCube properties
	MainCount    int `json:"main_count,omitempty"`
	ProblemCount int `json:"problem_count,omitempty"`

	// Shared
	PackCount int `json:"pack_count,omitempty"` // Set and Cube
}

func (do DraftOptions) getProvider() (draft.PackProvider, error) {
	switch do.Type {
	case DraftBlock:
		return mlp.BlockPacks(do.Block)
	case DraftSet:
		set, err := mlp.LoadSetHTTP(do.Set)
		if err != nil {
			return nil, err
		}
		return draft.PacksFromSet(do.PackCount, set), nil
	case DraftCube:
		cards, err := loadCube(do.CubeURL)
		if err != nil {
			return nil, err
		}
		cube := &draft.GenericCube{
			Cards:    cards,
			PackSize: do.PackSize,
		}
		return draft.PacksFromSet(do.PackCount, cube), nil
	case DraftI8PCube:
		cube, err := loadI8PCube(do.CubeURL)
		if err != nil {
			return nil, err
		}
		return cube.PackProvider(do.MainCount, do.ProblemCount), nil
	}
	return nil, errors.New("unknown draft type")
}

func newSession(playerCount int, opt DraftOptions) (*session, error) {
	// Get pack provider for given options
	provider, err := opt.getProvider()
	if err != nil {
		return nil, err
	}

	return &session{
		Options:  opt,
		Pod:      draft.MakePod(playerCount, provider),
		Players:  make(map[string]*draft.Player),
		messages: make(chan room.Message),
		exit:     make(chan bool),
	}, nil
}

func (s *session) Start() error {
	// Figure out how many players there are vs spots to be filled
	spots := len(s.Pod.Players)
	players := len(s.Players)
	if players > spots {
		return ErrTooManyPlayers
	}

	if players < 1 {
		return ErrNotEnoughPlayers
	}

	// Assign players to their spot on the drafting pod
	playerSpot := make(map[int]string)

	switch s.Options.Positioning {
	case PosRandom:
		// Assign a random number to each player
		for pname := range s.Players {
			var pos int
			for {
				pos = rand.Intn(spots)
				// Make sure chosen number wasn't already picked
				if _, ok := playerSpot[pos]; !ok {
					break
				}
			}
			playerSpot[pos] = pname
		}
	case PosEven:
		// Space players evenly
		playerRatio := float64(spots) / float64(players)
		i := 0
		for name := range s.Players {
			pos := int(math.Floor(playerRatio * float64(i)))
			playerSpot[pos] = name
			i++
		}
	}

	// Prepare order to be broadcasted after all spots have been assigned
	order := make([]string, len(s.Pod.Players))

	// Assign player instances and make bots where needed
	for i := range s.Pod.Players {
		if name, ok := playerSpot[i]; ok {
			s.Players[name] = s.Pod.Players[i]
			order[i] = "player:" + name
		} else {
			s.Bots = append(s.Bots, bot.MakeBot(s.Pod.Players[i]))
			order[i] = "bot"
		}
	}

	// Notify players of the order
	s.messages <- room.Message{
		Channel: "draft",
		Type:    "draft-order",
		Data:    order,
	}

	// Start handling packs
	s.started = true
	go s.handlePicks()
	return nil
}

func (s *session) handlePicks() {
	// Pack loop, this `for` handles an entire draft session
	totalPacks := len(s.Pod.Players[0].Packs)
	currentPack := 0
	for {
		err := s.Pod.OpenPacks()
		if err != nil {
			if err == draft.ErrNoPacksLeft {
				// Notify players that the draft is over
				s.messages <- room.Message{
					Channel: "draft",
					Type:    "draft-finish",
					Message: "No more packs, the draft is over!",
				}
				// Send each player their deck
				for pname, pdata := range s.Players {
					s.messages <- room.Message{
						To:      pname,
						Type:    "draft-picks",
						Data:    draft.Pack(pdata.Picks).IDs(),
						Message: fmt.Sprintf("Your picks are: %s", pdata.Picks),
					}
				}
				return
			}
			// Something is wrong!
			//TODO
			return
		}
		currentPack++
		s.messages <- room.Message{
			Channel: "draft",
			Type:    "draft-newpack",
			Data:    []int{currentPack, totalPacks},
			Message: fmt.Sprintf("Opening pack %d (of %d)", currentPack, totalPacks),
		}
		// Pick loop, this `for` handles exactly one round of packs
		for {
			s.messages <- room.Message{
				Channel: "draft",
				Type:    "draft-newpick",
				Message: fmt.Sprintf("New pick for pack #%d", currentPack),
			}

			// Make bots pick their cards
			for _, bot := range s.Bots {
				bot.PickNext()
			}

			// Tell every players their new cards
			for pname, player := range s.Players {
				s.messages <- room.Message{
					To:      pname,
					Type:    "draft-availablepicks",
					Data:    player.CurrentPack,
					Message: fmt.Sprintf("You got these cards: %s", player.CurrentPack),
				}
			}

			nextPack := false
			select {
			case <-s.Pod.ReadyNextPack:
				// Break of pick loop, get next packs
				nextPack = true
			case <-s.Pod.ReadyNextPick:
				// Pass packs around
				err := s.Pod.NextPacks()
				if err != nil {
					if err == draft.ErrNoPendingPack {
						// No more picks to do for this round of packs, go to next
						break
					} else {
						// Something is wrong!
						//TODO
						return
					}
				}
			case <-s.exit:
				// Room closed, exit early
				close(s.messages)
				close(s.exit)
				return
			}

			if nextPack {
				break
			}
		}
	}
}