package server

import (
	"io"
	"os"
	"fmt"
	"bytes"
	"bufio"
	"compress/gzip"
	"encoding/binary"
	"git.citrons.xyz/metronode/phony"
)

type levelId int32
type blockType byte
type levelPlayerId int8
type levelInfo struct {
	Id levelId
	Size blockPos
	IsSpawn bool
}

type level struct {
	phony.Inbox
	levelInfo
	loadingState int
	server *Server
	blocks []byte
	ids map[levelPlayerId]*player
	players map[*player]levelPlayerId
}

const (
	levelUnloaded = iota
	levelLoading
	levelLoaded
)

func newLevel(s *Server, info levelInfo) *level {
	return &level {
		levelInfo: info,
		server: s,
		loadingState: levelLoaded,
		blocks: make([]byte, info.Size.X * info.Size.Y * info.Size.Z),
		ids: make(map[levelPlayerId]*player),
		players: make(map[*player]levelPlayerId),
	}
}

func loadLevel(s *Server, id levelId, isSpawn bool) *level {
	l := &level {
		levelInfo: levelInfo {Id: id, IsSpawn: isSpawn},
		server: s,
		ids: make(map[levelPlayerId]*player),
		players: make(map[*player]levelPlayerId),
	}
	l.load()
	return l
}

func (l *level) load() {
	if l.loadingState == levelUnloaded {
		l.loadingState = levelLoading
		id := l.Id
		dataManager.Act(l, func() {
			f, err := os.Open(fmt.Sprintf("world/level/%d.bin", id))
			if l.handleLoadError(err) != nil {
				return
			}
			defer f.Close()
			var (
				rd = bufio.NewReader(f)
				info levelInfo
				blocks []byte
			)
			readDataField(rd, &info)
			z, err := gzip.NewReader(rd)
			if l.handleLoadError(err) != nil {
				return
			}
			z.Read(make([]byte, 4))
			blocks, err = io.ReadAll(z)
			if l.handleLoadError(err) != nil {
				return
			}
			l.Act(&dataManager, func() {
				l.loadingState = levelLoaded
				l.levelInfo = info
				l.Id = id
				l.blocks = blocks
				for player := range l.players {
					player.OnLevelData(l, l.levelInfo, l.compressLevelData())
				}
			})
		})
	}
}

func (l *level) handleLoadError(err error) error {
	if err == nil {
		return err
	}
	l.Act(&dataManager, func() {
		l.loadingState = levelUnloaded
		dataManager.errHand.OnLoadError(l, err)
		errString := "load level: " + err.Error()
		if os.IsNotExist(err) {
			errString = "level not found"
		}
		l.LevelError(nil, errString)
	})
	return err
}

func (l *level) LevelError(from phony.Actor, err string) {
	l.Act(from, func() {
		for player := range l.players {
			player.OnLevelError(l, err, l.levelInfo)
		}
	})
}

func (l *level) save(done func()) {
	if done != nil {
		defer dataManager.Act(nil, done)
	}
	if l.loadingState != levelLoaded {
		return
	}
	os.Mkdir("world/level", 0777)
	f, err := createAtomic(l, fmt.Sprintf("world/level/%d.bin", l.Id))
	if err != nil {
		dataManager.errHand.OnSaveError(l, err)
		return
	}
	defer f.Close()

	wr := bufio.NewWriter(f)
	writeDataField(wr, l.levelInfo)
	data := l.compressLevelData()
	defer data.Close()
	io.Copy(wr, data)
	if wr.Flush() != nil {
		dataManager.errHand.OnSaveError(l, err)
		return
	}
}

func (l *level) blockIndex(pos blockPos) int {
	return int(pos.X + pos.Z*l.Size.X + pos.Y*l.Size.X*l.Size.Z)
}

func (l *level) setBlock(pos blockPos, block blockType) {
	l.blocks[l.blockIndex(pos)] = byte(block)
}

func (l *level) getBlock(pos blockPos) blockType {
	return blockType(l.blocks[l.blockIndex(pos)])
}

func (l *level) compressLevelData() io.ReadCloser {
	rd, wr := io.Pipe()
	data := bytes.NewReader(bytes.Clone(l.blocks))
	go func() {
		defer wr.Close()
		z := gzip.NewWriter(wr)
		defer z.Close()
		binary.Write(z, binary.BigEndian, uint32(len(l.blocks)))
		io.Copy(z, data)
	}()
	return rd
}

func (l *level) generateFlat() {
	var p blockPos
	for p.Z = 0; p.Z < l.levelInfo.Size.Z; p.Z++ {
		for p.Y = 0; p.Y < l.levelInfo.Size.Y / 2; p.Y++ {
			for p.X = 0; p.X < l.levelInfo.Size.X; p.X++ {
				var block blockType
				if p.Y == 0 {
					block = 7
				} else if p.Y == l.levelInfo.Size.Y/2 - 1 {
					block = 2
				} else if p.Y > l.levelInfo.Size.Y/2 - 15 {
					block = 3
				} else {
					block = 1
				}
				l.setBlock(p, block)
			}
		}
	}
}

func (l *level) Save(from phony.Actor, done func()) {
	l.Act(from, func() {
		l.save(func() {
			if done != nil {
				from.Act(nil, done)
			}
		})
	})
}

func (l *level) SetBlock(from phony.Actor, pos blockPos, block blockType) {
	if l.loadingState != levelLoaded {
		return
	}
	l.Act(from, func() {
		l.setBlock(pos, block)
		for player := range l.players {
			player.OnSetBlock(l, pos, block)
		}
	})
}

func (l *level) OnAddPlayer(from *player, name string, pos entityPos) {
	l.Act(from, func() {
		l.load()
		if l.loadingState == levelLoaded {
			from.OnLevelData(l, l.levelInfo, l.compressLevelData())
		}
		var newId levelPlayerId
		for newId = 0; newId <= 127; newId++ {
			if l.ids[newId] == nil {
				break
			}
		}
		if newId == -1 {
			from.OnLevelError(
				l, "there are too many players in this area", l.levelInfo,
			)
		}
		for player, id := range l.players {
			if player != from {
				player.OnPlayer(l, newId, name, pos)
				player.GetInfo(l,
					func(name string, state playerState) {
						from.OnPlayer(l, id, name, state.Pos)
					},
				)
			}
		}
		l.ids[newId] = from
		l.players[from] = newId
	})
}

func (l *level) OnRemovePlayer(from *player) {
	l.Act(from, func() {
		delId := l.players[from]
		delete(l.ids, delId)
		delete(l.players, from)
		for player := range l.players {
			player.OnRemovePlayer(l, delId)
		}
	})
}

func (l *level) OnMovePlayer(
		from *player, pos entityPos, facing entityFacing) {
	l.Act(from, func() {
		for player := range l.players {
			if player != from {
				player.OnMovePlayer(l, l.players[from], pos, facing)
			}
		}
	})
}