package main

import (
	"flag"
	"log"
	"math"
	"os"
	"time"

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

	"ur.gs/chaos-gate/internal/maps"
)

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")

	winX = flag.Int("win-x", 1280, "width of the view-map window")
	winY = flag.Int("win-y", 1024, "height of the view-map window")
)

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)
	}

	// The main thread now belongs to pixelgl
	pixelgl.Run(func() { run(gameMap) })
}

type runState struct {
	redraw     bool
	started    time.Time
	autoUpdate bool
	gameMap    *maps.GameMap

	zoom float64

	zIdx    int
	cellIdx int
}

func run(gameMap *maps.GameMap) {
	cfg := pixelgl.WindowConfig{
		Title:  "View Map " + *mapFile,
		Bounds: pixel.R(0, 0, float64(*winX), float64(*winY)),
		VSync:  true,
	}

	win, err := pixelgl.NewWindow(cfg)
	if err != nil {
		log.Fatal("Couldn't create window: %v", err)
	}

	state := &runState{
		redraw:     true,
		started:    time.Now(),
		autoUpdate: true,
		gameMap:    gameMap,
		zoom:       1.0,
	}

	for !win.Closed() {
		if state.redraw {
			log.Printf("z=%d cellIdx=%d", state.zIdx, state.cellIdx)
			presentFull(win, state)
		}

		state = runStep(win, state)

		win.Update()
	}
}

// TODO: cut this down to showing just the viewport?
// The naive approach using gameMap.Width() / Height() cuts half the map off :/
func presentFull(win *pixelgl.Window, state *runState) {
	gameMap := state.gameMap
	center := win.Bounds().Center()
	sz := win.Bounds().Size()
	imd := imdraw.New(nil)

	// Rotate everything 45' anticlockwise to get an isometric view with the
	// lowest coordinates at the (now) top corner
	imd.SetMatrix(pixel.IM.Rotated(center, -math.Pi/4))

	xPerCell := sz.X / float64(maps.MaxWidth)
	yPerCell := sz.Y / float64(maps.MaxLength)

	for y := 0; y < maps.MaxLength; y++ {
		for x := 0; x < maps.MaxWidth; x++ {
			min := pixel.Vec{X: float64(x) * xPerCell, Y: float64(y) * yPerCell}
			max := pixel.Vec{X: min.X + xPerCell, Y: min.Y + yPerCell}

			cell := gameMap.Cells.At(int(x), int(y), int(state.zIdx))
			// TODO: represent the state of the cell *sensibly*, using colour.
			// Need to understand the contents better first, so for now optimize
			// for exploration
			//
			// CellIndex=3 shows walls & elevation changes
			imd.Color = makeColour(cell, state.cellIdx)
			imd.Push(min, max)
			imd.Rectangle(0.0)
		}
	}

	cam := pixel.IM.Scaled(center, state.zoom)
	win.SetMatrix(cam)
	win.Clear(colornames.Black)
	imd.Draw(win)
}

func makeColour(cell maps.Cell, colIdx int) pixel.RGBA {
	return pixel.RGB(
		float64(cell[colIdx]),
		float64(cell[colIdx]),
		float64(cell[colIdx]),
	)
}

func runStep(win *pixelgl.Window, state *runState) *runState {
	nextState := *state
	nextState.redraw = false

	// Enable / disable auto-update with the enter key
	if win.JustPressed(pixelgl.KeyEnter) {
		nextState.autoUpdate = !state.autoUpdate
		log.Printf("autoUpdate=%v", nextState.autoUpdate)

		if nextState.autoUpdate {
			nextState.started = time.Now()
		}
	}

	// Automatically cycle every second when auto-update is on
	if nextState.autoUpdate && time.Now().Sub(nextState.started) > time.Second {
		nextState.redraw = true
		nextState.cellIdx = nextState.cellIdx + 1
		if nextState.cellIdx >= maps.CellSize {
			nextState.cellIdx = 0
			nextState.zIdx = nextState.zIdx + 1
		}

		if nextState.zIdx >= maps.MaxHeight {
			nextState.zIdx = 0
		}

		nextState.started = time.Now()
	}

	if win.JustPressed(pixelgl.KeyDown) {
		if nextState.zIdx <= 0 {
			log.Printf("z index is already at minimum")
		} else {
			nextState.redraw = true
			nextState.zIdx = nextState.zIdx - 1
		}
	}

	if win.JustPressed(pixelgl.KeyUp) {
		if nextState.zIdx >= maps.MaxHeight-1 {
			log.Printf("z index is already at maximum")
		} else {
			nextState.redraw = true
			nextState.zIdx = nextState.zIdx + 1
		}
	}

	if win.JustPressed(pixelgl.KeyLeft) {
		if nextState.cellIdx <= 0 {
			log.Printf("cell index is already at minimum")
		} else {
			nextState.redraw = true
			nextState.cellIdx = nextState.cellIdx - 1
		}
	}

	if win.JustPressed(pixelgl.KeyRight) {
		if nextState.cellIdx >= maps.CellSize-1 {
			log.Printf("cell index is already at maximum")
		} else {
			nextState.redraw = true
			nextState.cellIdx = nextState.cellIdx + 1
		}
	}

	// Zoom in and out with the mouse wheel
	nextState.zoom *= math.Pow(1.2, win.MouseScroll().Y)
	if nextState.zoom != state.zoom {
		log.Printf("zoom=%.2f", nextState.zoom)
		nextState.redraw = true
	}

	return &nextState
}