package main

import (
	"flag"
	"fmt"
	"log"
	"math"
	"os"
	"path/filepath"
	"time"

	"github.com/faiface/pixel"
	"github.com/faiface/pixel/pixelgl"
	"golang.org/x/image/colornames"

	"ur.gs/ordoor/internal/conv"
	"ur.gs/ordoor/internal/data"
	"ur.gs/ordoor/internal/maps"
	"ur.gs/ordoor/internal/sets"
	"ur.gs/ordoor/internal/ui"
)

var (
	gamePath = flag.String("game-path", "./orig", "Path to a WH40K: Chaos Gate installation")
	mapFile  = flag.String("map", "", "Prefix path to a .map file, e.g. ./orig/Maps/Chapter01.MAP")
	txtFile  = flag.String("txt", "", "Prefix path to a .txt file, e.g. ./orig/Maps/Chapter01.txt")
)

type env struct {
	gameMap *maps.GameMap
	set     *sets.MapSet
	objects map[string]*conv.Object
	sprites map[string][]*pixel.Sprite
	batch   *pixel.Batch
}

type state struct {
	env *env

	step      int
	fpsTicker <-chan time.Time

	cam    pixel.Matrix
	camPos pixel.Vec

	zoom float64
	rot  float64

	zIdx int
}

func main() {
	flag.Parse()

	if *gamePath == "" || *mapFile == "" || *txtFile == "" {
		flag.Usage()
		os.Exit(1)
	}

	gameMap, err := maps.LoadGameMapByFiles(*mapFile, *txtFile)
	if err != nil {
		log.Fatalf("Couldn't load map file: %v", err)
	}

	setFile := filepath.Join(*gamePath, "Sets", gameMap.MapSetFilename())
	log.Println(setFile)
	mapSet, err := sets.LoadSet(setFile)
	if err != nil {
		log.Fatalf("Couldn't load set file %s: %v", setFile, err)
	}

	rawObjs := []*data.Object{}
	for _, name := range mapSet.Palette {
		objFile := filepath.Join(*gamePath, "Obj", name+".obj")
		obj, err := data.LoadObject(objFile)
		if err != nil {
			log.Fatalf("Failed to load %s: %v", name, err)
		}

		obj.Name = name
		rawObjs = append(rawObjs, obj)
	}

	objects, spritesheet := conv.ConvertObjects(rawObjs)
	batch := pixel.NewBatch(&pixel.TrianglesData{}, spritesheet)

	env := &env{
		gameMap: gameMap,
		set:     mapSet,
		objects: conv.MapByName(objects),
		batch:   batch,
	}

	// The main thread now belongs to pixelgl
	pixelgl.Run(env.run)
}

func (e *env) run() {
	title := "View Map " + *mapFile
	win, err := ui.NewWindow(title + " | FPS: ?")
	if err != nil {
		log.Fatal("Couldn't create window: %v", err)
	}

	pWin := win.PixelWindow
	state := &state{
		env: e,
		//		camPos: pixel.V(0, float64(-pWin.Bounds().Size().Y)),
		//		camPos: pixel.V(float64(3700), float64(0)),
		zoom:      1.0,
		rot:       0.785,
		step:      -1,
		fpsTicker: time.Tick(time.Second),
	}
	pWin.SetSmooth(true)

	win.Run(func() {
		oldState := *state
		state = state.runStep(pWin)

		if oldState != *state || oldState.step == -1 {
			log.Printf("zoom=%.2f rot=%.4f zIdx=%v camPos=%#v", state.zoom, state.rot, state.zIdx, state.camPos)
			state.present(pWin)
		}

		state.step += 1
		select {
		case <-state.fpsTicker:
			pWin.SetTitle(fmt.Sprintf("%s | FPS: %d", title, state.step))
			state.step = 0
		default:
		}

	})
}

func (e *env) getSprite(palette []string, ref maps.ObjRef) (*conv.Sprite, error) {
	// There seems to be an active bit that hides many sins
	if !ref.IsActive() {
		return nil, nil
	}

	if ref.Index() >= len(palette) {
		return nil, fmt.Errorf("Palette too small: %v requested", ref.Index())
	}

	name := palette[ref.Index()]

	obj := e.objects[name]
	if obj == nil {
		return nil, fmt.Errorf("Failed to find surface sprite %#v -> %q", ref, name)
	}

	if ref.Sprite() >= len(obj.Sprites) {
		return nil, fmt.Errorf("Out-of-index sprite %v requested for %v", ref.Sprite(), name)
	}

	return obj.Sprites[ref.Sprite()], nil
}

func (s *state) present(pWin *pixelgl.Window) {
	pWin.Clear(colornames.Black)
	s.env.batch.Clear()

	center := pWin.Bounds().Center()

	cam := pixel.IM
	cam = cam.ScaledXY(center, pixel.Vec{1.0, -1.0}) // invert the Y axis
	cam = cam.Scaled(center, s.zoom)                 // apply current zoom factor
	cam = cam.Moved(center.Sub(s.camPos))            // Make it central
	s.cam = cam
	pWin.SetMatrix(cam)

	// TODO: we should be able to perform bounds clipping on these
	minX := int(s.env.gameMap.MinWidth)
	maxX := int(s.env.gameMap.MaxWidth)
	minY := int(s.env.gameMap.MinLength)
	maxY := int(s.env.gameMap.MaxLength)
	minZ := 0
	maxZ := int(s.zIdx) + 1

	for z := minZ; z < maxZ; z++ {
		for y := minY; y < maxY; y++ {
			for x := minX; x < maxX; x++ {
				s.renderCell(x, y, z, s.env.batch)
			}
		}
	}

	s.env.batch.Draw(pWin)
	pWin.Update()
}

func (s *state) renderCell(x, y, z int, target pixel.Target) {
	var sprites []*conv.Sprite

	cell := s.env.gameMap.Cells.At(x, y, z)

	if spr, err := s.env.getSprite(s.env.set.Palette, cell.Surface); err != nil {
		log.Printf("%v %v %v surface: %v", x, y, z, err)
	} else if spr != nil {
		sprites = append(sprites, spr)
	}

	if spr, err := s.env.getSprite(s.env.set.Palette, cell.Center); err != nil {
		log.Printf("%v %v %v center: %v", x, y, z, err)
	} else if spr != nil {
		sprites = append(sprites, spr)
	}

	if spr, err := s.env.getSprite(s.env.set.Palette, cell.Left); err != nil {
		log.Printf("%v %v %v left: %v", x, y, z, err)
	} else if spr != nil {
		sprites = append(sprites, spr)
	}

	if spr, err := s.env.getSprite(s.env.set.Palette, cell.Right); err != nil {
		log.Printf("%v %v %v right: %v", x, y, z, err)
	} else if spr != nil {
		sprites = append(sprites, spr)
	}

	// Taking the Z index away *seems* to draw the object in the correct place.
	// FIXME: There are some artifacts, investigate more
	fX := float64(x)
	fY := float64(y)

	iso := s.cellToPix(pixel.V(fX, fY))
	iso = iso.Add(pixel.Vec{0.0, -float64(z * 48.0)})

	for _, sprite := range sprites {
		sprite.Spr.Draw(target, pixel.IM.Moved(iso))
	}
}

var (
	cellWidth  = 64.0
	cellHeight = 64.0
)

// Doesn't take the camera or Z level into account
func (s *state) cellToPix(cell pixel.Vec) pixel.Vec {
	return pixel.V(
		(cell.X-cell.Y)*cellWidth,
		(cell.X+cell.Y)*cellHeight/2.0,
	)
}

// Doesn't take the camera or Z level into account
func (s *state) pixToCell(pix pixel.Vec) pixel.Vec {
	return pixel.V(
		pix.Y/cellHeight+pix.X/(cellWidth*2.0),
		pix.Y/cellHeight-pix.X/(cellWidth*2.0),
	)
}

func (s *state) runStep(pWin *pixelgl.Window) *state {
	newState := *s
	newState.handleKeys(pWin)

	return &newState
}

func (s *state) handleKeys(pWin *pixelgl.Window) {
	// Do this first to avoid taking the below mutations into account
	// FIXME: this suggests we should pass the next state into here and
	// modify it instead
	if pWin.JustPressed(pixelgl.MouseButton1) {
		if s.zIdx != 0 {
			log.Printf("WARNING: z-index not yet taken into account")
		}

		log.Printf("cam: %#v", s.cam)

		pos := s.pixToCell(s.cam.Unproject(pWin.MousePosition()))
		log.Printf("X=%v Y=%v, zIdx=%v", pos.X, pos.Y, s.zIdx)

		cell := s.env.gameMap.Cells.At(int(pos.X), int(pos.Y), s.zIdx)
		log.Printf("Cell=%#v", cell)
	}

	if pWin.Pressed(pixelgl.KeyLeft) {
		s.camPos.X -= 64
	}

	if pWin.Pressed(pixelgl.KeyRight) {
		s.camPos.X += 64
	}

	if pWin.Pressed(pixelgl.KeyDown) {
		s.camPos.Y -= 64
	}

	if pWin.Pressed(pixelgl.KeyUp) {
		s.camPos.Y += 64
	}

	for i := 1; i <= 7; i++ {
		if pWin.JustPressed(pixelgl.Key0 + pixelgl.Button(i)) {
			s.zIdx = i - 1
		}
	}

	if pWin.Pressed(pixelgl.KeyMinus) {
		s.rot -= 0.001
	}

	if pWin.Pressed(pixelgl.KeyEqual) {
		s.rot += 0.001
	}

	// Zoom in and out with the mouse wheel
	s.zoom *= math.Pow(1.2, pWin.MouseScroll().Y)
}