package main

import (
	"bytes"
	"flag"
	"image/color"
	"log"
	"math"
	"os"
	"path/filepath"

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

	"ur.gs/chaos-gate/internal/data"
	"ur.gs/chaos-gate/internal/sets"
	"ur.gs/chaos-gate/internal/ui"
)

var (
	gamePath = flag.String("game-path", "./orig", "Path to a WH40K: Chaos Gate installation")
	setFile  = flag.String("set", "", "Path to a .set file, e.g. ./orig/Sets/map01.set")
)

type env struct {
	set     *sets.MapSet
	objects map[string]*data.Object
}

type state struct {
	env *env

	step      int
	objIdx    int
	spriteIdx int

	zoom float64

	cam    pixel.Matrix
	camPos pixel.Vec
}

func main() {
	flag.Parse()

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

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

	objects := make(map[string]*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)
		}

		objects[filepath.Base(objFile)] = obj
	}

	env := &env{objects: objects, set: mapSet}

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

func (e *env) run() {
	win, err := ui.NewWindow("View Set: " + *setFile)
	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)),
		zoom:   8.0,
	}

	// For now, just try to display the various objects
	// left + right to change object, up + down to change frame
	win.Run(func() {
		oldState := *state
		state = state.runStep(pWin)

		if oldState != *state || oldState.step == 0 {
			log.Printf(
				"new state: numObj=%d object=%d (%s) numFrames=%d sprite=%d zoom=%.2f",
				state.env.set.Count(),
				state.objIdx,
				state.env.set.Palette[state.objIdx], // FIXME: palette is a confusing name
				state.curObject().NumSprites,
				state.spriteIdx,
				state.zoom,
			)
			state.step += 1

			state.present(pWin)
		}
	})
}

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

	return &newState
}

// WIP. Try to convert the pixeldata into a picture.
func spriteToPic(sprite *data.Sprite) *pixel.PictureData {
	pic := pixel.MakePictureData(pixel.R(float64(0), float64(0), float64(sprite.Width), float64(sprite.Height)))

	buf := bytes.NewBuffer(sprite.PixelData)

	// The pixeldata seems to be formed of Y null-terminated records, with
	// varying numbers of bytes in each row. Probably [type, *data] but ignore
	// type for now.
	//
	// Theory: perhaps the data in each X is centered around the origin?
	for y := 0; y < int(sprite.Height); y++ {
		rowData, err := buf.ReadBytes(0)
		if err != nil {
			log.Printf("Error at y=%d: %v", y, err)
			continue
		}

		leftPad := (int(sprite.Width) - len(rowData)) / 2

		for x, b := range rowData {
			idx := pic.Index(pixel.V(float64(leftPad+x), float64(y)))
			pic.Pix[idx] = color.RGBA{
				R: b,
				G: b,
				B: b,
				A: 255,
			}
		}
	}

	return pic
}

func (s *state) present(pWin *pixelgl.Window) {
	obj := s.curObject()
	sprite := obj.Sprites[s.spriteIdx]
	pic := spriteToPic(sprite)

	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
	//cam = cam.Rotated(center, -0.785) // Apply isometric angle
	s.cam = cam
	pWin.SetMatrix(s.cam)

	pWin.Clear(colornames.Black)
	pixel.NewSprite(pic, pic.Bounds()).Draw(pWin, pixel.IM.Moved(center))
}

func (s *state) handleKeys(pWin *pixelgl.Window) {
	if pWin.JustPressed(pixelgl.KeyLeft) {
		if s.objIdx > 0 {
			s.objIdx -= 1
			s.spriteIdx = 0
		}
	}

	if pWin.JustPressed(pixelgl.KeyRight) {
		if s.objIdx < s.env.set.Count()-1 {
			s.objIdx += 1
			s.spriteIdx = 0
		}
	}

	if pWin.JustPressed(pixelgl.KeyDown) {
		if s.spriteIdx > 0 {
			s.spriteIdx -= 1
		}
	}

	if pWin.JustPressed(pixelgl.KeyUp) {
		if s.spriteIdx < int(s.curObject().NumSprites)-1 {
			s.spriteIdx += 1
		}
	}

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

func (s *state) curObject() *data.Object {
	name := s.env.set.Palette[s.objIdx] + ".obj"

	return s.env.objects[name] // FIXME: we should use consistent naming!
}