package main

import (
	"flag"
	"fmt"
	"github.com/Tnze/go-mc/data/block"
	"github.com/Tnze/go-mc/save"
	"github.com/Tnze/go-mc/save/region"
	"image"
	"image/color"
	"image/draw"
	"log"
	"os"
	"path/filepath"
	"runtime"
	"sync"
	"unsafe"
)

var colors []color.RGBA64
var regionWorkerNum = runtime.NumCPU()
var sectionWorkerNum = 1

var (
	regionsFold = flag.String("region", filepath.Join(os.Getenv("AppData"), ".minecraft", "saves", "World", "region"), "region directory path")
)

func main() {
	flag.Usage = usage
	flag.Parse()

	de, err := os.ReadDir(*regionsFold)
	if err != nil {
		log.Fatal(err)
	}

	var min, max [2]int
	updateMinMax := func(pos [2]int) {
		mkmax(&max[0], &pos[0])
		mkmax(&max[1], &pos[1])
		mkmin(&min[0], &pos[0])
		mkmin(&min[1], &pos[1])
	}

	// Open mca files
	var rs = make(map[[2]int]*region.Region, len(de))
	for _, dir := range de {
		name := dir.Name()
		path := filepath.Join(*regionsFold, name)
		var pos [2]int // {x, z}
		if _, err := fmt.Sscanf(name, "r.%d.%d.mca", &pos[0], &pos[1]); err != nil {
			log.Printf("Error parsing file name of %s: %v, ignoring", name, err)
			continue
		}
		updateMinMax(pos)

		r, err := region.Open(path)
		if err != nil {
			log.Printf("Error when opening %s: %v, ignoring", name, err)
			continue
		}
		rs[pos] = r
	}
	// To close mca files
	defer func() {
		for pos, r := range rs {
			if err := r.Close(); err != nil {
				log.Printf("Close r.%d.%d.mca error: %v", pos[0], pos[1], err)
			}
		}
	}()
	// draw columns
	for pos, r := range rs {
		img := image.NewRGBA(image.Rect(0, 0, 32*16, 32*16))
		type task struct {
			data []byte
			pos  [2]int
		}
		c := make(chan task)
		var wg sync.WaitGroup
		for i := 0; i < regionWorkerNum; i++ {
			go func() {
				var column save.Column
				for task := range c {
					if err := column.Load(task.data); err != nil {
						log.Printf("Decode column (%d.%d) error: %v", task.pos[0], task.pos[1], err)
					}
					pos := [2]int{int(column.Level.PosX), int(column.Level.PosZ)}
					if pos != task.pos {
						fmt.Printf("chunk position not match: want %v, get %v\n", task.pos, pos)
					}
					draw.Draw(
						img, image.Rect(task.pos[0]*16, task.pos[1]*16, task.pos[0]*16+16, task.pos[1]*16+16),
						drawColumn(&column), image.Pt(0, 0),
						draw.Over,
					)
					wg.Done()
				}
			}()
		}

		for x := 0; x < 32; x++ {
			for z := 0; z < 32; z++ {
				if !r.ExistSector(x, z) {
					continue
				}
				data, err := r.ReadSector(x, z)
				if err != nil {
					log.Printf("Read sector (%d.%d) error: %v", x, z, err)
				}
				wg.Add(1)
				c <- task{data: data, pos: [2]int{x, z}}
			}
		}
		close(c)
		wg.Wait()
		savePng(img, fmt.Sprintf("r.%d.%d.png", pos[0], pos[1]))
		log.Print("Draw: ", pos)
	}
}

func drawColumn(column *save.Column) (img *image.RGBA) {
	img = image.NewRGBA(image.Rect(0, 0, 16, 16))
	s := column.Level.Sections
	c := make(chan *save.Chunk)
	var wg sync.WaitGroup
	for i := 0; i < sectionWorkerNum; i++ {
		go func() {
			for s := range c {
				drawSection(s, img)
				wg.Done()
			}
		}()
	}
	defer close(c)

	wg.Add(len(s))
	for i := range s {
		c <- &s[i]
	}
	wg.Wait()

	return
}

func drawSection(s *save.Chunk, img *image.RGBA) {
	// calculate bits per block
	bpb := len(s.BlockStates) * 64 / (16 * 16 * 16)
	// skip empty
	if len(s.BlockStates) == 0 {
		return
	}
	// decode section
	//n := int(math.Max(4, math.Ceil(math.Log2(float64(len(s.Palette))))))

	// decode status
	data := *(*[]uint64)(unsafe.Pointer(&s.BlockStates)) // convert []int64 into []uint64
	bs := save.NewBitStorage(bpb, 4096, data)
	for y := 0; y < 16; y++ {
		layerImg := image.NewRGBA(image.Rect(0, 0, 16, 16))
		for i := 16*16 - 1; i >= 0; i-- {
			b := block.ByID[block.StateID[uint32(bs.Get(y*16*16+i))]]
			c := colors[b.ID]
			layerImg.Set(i/16, i%16, c)
		}
		draw.Draw(
			img, image.Rect(0, 0, 16, 16),
			layerImg, image.Pt(0, 0),
			draw.Over,
		)
	}
	return
}