// Copyright 2018 The Ebiten Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// +build example jsgo

package main

import (
	"bytes"
	"errors"
	"fmt"
	"image"
	"image/color"
	_ "image/jpeg"
	"log"
	"math"

	"github.com/golang/freetype/truetype"
	"golang.org/x/image/font"

	"github.com/hajimehoshi/ebiten"
	"github.com/hajimehoshi/ebiten/examples/resources/fonts"
	"github.com/hajimehoshi/ebiten/examples/resources/images"
	"github.com/hajimehoshi/ebiten/text"
)

var (
	count              = 0
	gophersImage       *ebiten.Image
	mplusFont          font.Face
	regularTermination = errors.New("regular termination")
)

func init() {
	// Decode image from a byte slice instead of a file so that
	// this example works in any working directory.
	// If you want to use a file, there are some options:
	// 1) Use os.Open and pass the file to the image decoder.
	//    This is a very regular way, but doesn't work on browsers.
	// 2) Use ebitenutil.OpenFile and pass the file to the image decoder.
	//    This works even on browsers.
	// 3) Use ebitenutil.NewImageFromFile to create an ebiten.Image directly from a file.
	//    This also works on browsers.
	img, _, err := image.Decode(bytes.NewReader(images.Gophers_jpg))
	if err != nil {
		log.Fatal(err)
	}
	gophersImage, _ = ebiten.NewImageFromImage(img, ebiten.FilterDefault)
}

func initFont() {
	tt, err := truetype.Parse(fonts.MPlus1pRegular_ttf)
	if err != nil {
		log.Fatal(err)
	}

	const dpi = 72
	mplusFont = truetype.NewFace(tt, &truetype.Options{
		Size:    12 * ebiten.DeviceScaleFactor(),
		DPI:     dpi,
		Hinting: font.HintingFull,
	})
}

func update(screen *ebiten.Image) error {
	count++

	if ebiten.IsKeyPressed(ebiten.KeyQ) {
		return regularTermination
	}

	if ebiten.IsRunningSlowly() {
		return nil
	}

	scale := ebiten.DeviceScaleFactor()

	w, h := gophersImage.Size()
	op := &ebiten.DrawImageOptions{}

	op.GeoM.Translate(-float64(w)/2, -float64(h)/2)
	op.GeoM.Scale(scale, scale)
	op.GeoM.Rotate(float64(count%360) * 2 * math.Pi / 360)
	sw, sh := screen.Size()
	op.GeoM.Translate(float64(sw)/2, float64(sh)/2)
	op.Filter = ebiten.FilterLinear
	screen.DrawImage(gophersImage, op)

	mw, mh := ebiten.MonitorSize()
	msgs := []string{
		"This is an example of the finest fullscreen. Press Q to quit.",
		fmt.Sprintf("Monitor size: %d, %d", mw, mh),
		fmt.Sprintf("Game's screen size: %d, %d", sw, sh),
		fmt.Sprintf("Device scale factor: %0.2f", scale),
	}

	for i, msg := range msgs {
		text.Draw(screen, msg, mplusFont, 100, 100+int(float64(i)*16*scale), color.White)
	}

	return nil
}

func main() {
	// Call initFont here instead of init funcs since ebiten.DeviceScaleFactor is not available in init.
	initFont()

	ebiten.SetFullscreen(true)

	w, h := ebiten.MonitorSize()
	// On mobiles, ebiten.MonitorSize is not available so far.
	// Use arbitrary values.
	if w == 0 || h == 0 {
		w = 300
		h = 450
	}

	s := ebiten.DeviceScaleFactor()
	if err := ebiten.Run(update, int(float64(w)*s), int(float64(h)*s), 1/s, "Rotate (Ebiten Demo)"); err != nil && err != regularTermination {
		log.Fatal(err)
	}
}