// Copyright 2014 Hajime Hoshi
//
// 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.

package ebiten

import (
	"sync/atomic"

	"github.com/hajimehoshi/ebiten/internal/clock"
	"github.com/hajimehoshi/ebiten/internal/driver"
)

// Game defines necessary functions for a game.
type Game interface {
	// Update updates a game by one tick. The given argument represents a screen image.
	//
	// Basically Update updates the game logic. Whether Update also draws the screen or not depends on the
	// existence of Draw implementation.
	//
	// The Draw function's definition is:
	//
	//     Draw(screen *Image)
	//
	// With Draw (the recommended way), Update updates only the game logic and Draw draws the screen.
	// In this case, the argument screen's updated content by Update is not adopted for the actual game screen,
	// and the screen's updated content by Draw is adopted instead.
	// In the first frame, it is ensured that Update is called at least once before Draw. You can use Update
	// to initialize the game state. After the first frame, Update might not be called or might be called once
	// or more for one frame. The frequency is determined by the current TPS (tick-per-second).
	//
	// Without Draw (the legacy way), Update updates the game logic and also draws the screen.
	// In this case, the argument screen's updated content by Update is adopted for the actual game screen.
	Update(screen *Image) error

	// Draw draws the game screen by one frame.
	//
	// The give argument represents a screen image. The updated content is adopted as the game screen.
	//
	// Draw is an optional function for backward compatibility.
	//
	// Draw(screen *Image)

	// Layout accepts a native outside size in device-independent pixels and returns the game's logical screen
	// size.
	//
	// On desktops, the outside is a window or a monitor (fullscreen mode). On browsers, the outside is a body
	// element. On mobiles, the outside is the view's size.
	//
	// Even though the outside size and the screen size differ, the rendering scale is automatically adjusted to
	// fit with the outside.
	//
	// Layout is called almost every frame.
	//
	// If Layout returns non-positive numbers, the caller can panic.
	//
	// You can return a fixed screen size if you don't care, or you can also return a calculated screen size
	// adjusted with the given outside size.
	Layout(outsideWidth, outsideHeight int) (screenWidth, screenHeight int)
}

// TPS represents a default ticks per second, that represents how many times game updating happens in a second.
const DefaultTPS = 60

// FPS is deprecated as of 1.8.0-alpha: Use DefaultTPS instead.
const FPS = DefaultTPS

// CurrentFPS returns the current number of FPS (frames per second), that represents
// how many swapping buffer happens per second.
//
// On some environments, CurrentFPS doesn't return a reliable value since vsync doesn't work well there.
// If you want to measure the application's speed, Use CurrentTPS.
//
// CurrentFPS is concurrent-safe.
func CurrentFPS() float64 {
	return clock.CurrentFPS()
}

var (
	isDrawingSkipped = int32(0)
	currentMaxTPS    = int32(DefaultTPS)
)

func setDrawingSkipped(skipped bool) {
	v := int32(0)
	if skipped {
		v = 1
	}
	atomic.StoreInt32(&isDrawingSkipped, v)
}

// IsDrawingSkipped returns true if rendering result is not adopted.
// It is recommended to skip drawing images or screen
// when IsDrawingSkipped is true.
//
// The typical code with IsDrawingSkipped is this:
//
//    func update(screen *ebiten.Image) error {
//
//        // Update the state.
//
//        // When IsDrawingSkipped is true, the rendered result is not adopted.
//        // Skip rendering then.
//        if ebiten.IsDrawingSkipped() {
//            return nil
//        }
//
//        // Draw something to the screen.
//
//        return nil
//    }
//
// IsDrawingSkipped is useful if you use Run function or RunGame function without implementing Game's Draw.
// Otherwise, i.e., if you use RunGame function with implementing Game's Draw, IsDrawingSkipped should not be used.
// If you use RunGame and Draw, IsDrawingSkipped always returns true.
//
// IsDrawingSkipped is concurrent-safe.
func IsDrawingSkipped() bool {
	return atomic.LoadInt32(&isDrawingSkipped) != 0
}

// IsRunningSlowly is deprecated as of 1.8.0-alpha. Use Game's Draw function instead.
func IsRunningSlowly() bool {
	return IsDrawingSkipped()
}

// Run starts the main loop and runs the game.
// f is a function which is called at every frame.
// The argument (*Image) is the render target that represents the screen.
// The screen size is based on the given values (width and height).
//
// Run is a shorthand for RunGame, but there are some restrictions.
// If you want to resize the window by dragging, use RunGame instead.
//
// A window size is based on the given values (width, height and scale).
//
// scale is used to enlarge the screen on desktops.
// scale is ignored on browsers or mobiles.
// Note that the actual screen is multiplied not only by the given scale but also
// by the device scale on high-DPI display.
// If you pass inverse of the device scale,
// you can disable this automatical device scaling as a result.
// You can get the device scale by DeviceScaleFactor function.
//
// On browsers, the scale is automatically adjusted.
// It is strongly recommended to use iframe if you embed an Ebiten application in your website.
// scale works as this as of 1.10.0-alpha.
// Before that, scale affected the rendering scale.
//
// On mobiles, if you use ebitenmobile command, the scale is automatically adjusted.
//
// Run must be called on the main thread.
// Note that Ebiten bounds the main goroutine to the main OS thread by runtime.LockOSThread.
//
// Ebiten tries to call f 60 times a second by default. In other words,
// TPS (ticks per second) is 60 by default.
// This is not related to framerate (display's refresh rate).
//
// f is not called when the window is in background by default.
// This setting is configurable with SetRunnableOnUnfocused.
//
// The given scale is ignored on fullscreen mode or gomobile-build mode.
//
// On non-GopherJS environments, Run returns error when 1) OpenGL error happens, 2) audio error happens or
// 3) f returns error. In the case of 3), Run returns the same error.
//
// On GopherJS, Run returns immediately.
// It is because the 'main' goroutine cannot be blocked on GopherJS due to the bug (gopherjs/gopherjs#826).
// When an error happens, this is shown as an error on the console.
//
// The size unit is device-independent pixel.
//
// Don't call Run twice or more in one process.
func Run(f func(*Image) error, width, height int, scale float64, title string) error {
	if IsWindowResizable() {
		panic("ebiten: a resizable window works with RunGame, not Run")
	}
	game := &defaultGame{
		update: (&imageDumper{f: f}).update,
		width:  width,
		height: height,
	}
	ww, wh := int(float64(width)*scale), int(float64(height)*scale)
	fixWindowPosition(ww, wh)
	SetWindowSize(ww, wh)
	SetWindowTitle(title)
	return runGame(game, scale)
}

type imageDumperGame struct {
	game Game
	d    *imageDumper
}

func (i *imageDumperGame) Update(screen *Image) error {
	if i.d == nil {
		i.d = &imageDumper{f: i.game.Update}
	}
	return i.d.update(screen)
}

func (i *imageDumperGame) Layout(outsideWidth, outsideHeight int) (screenWidth, screenHeight int) {
	return i.game.Layout(outsideWidth, outsideHeight)
}

type imageDumperGameWithDraw struct {
	imageDumperGame
	err error
}

func (i *imageDumperGameWithDraw) Update(screen *Image) error {
	if i.err != nil {
		return i.err
	}
	return i.imageDumperGame.Update(screen)
}

func (i *imageDumperGameWithDraw) Draw(screen *Image) {
	if i.err != nil {
		return
	}

	i.game.(interface{ Draw(*Image) }).Draw(screen)

	// Call dump explicitly. IsDrawingSkipped always returns true when Draw is defined.
	if i.d == nil {
		i.d = &imageDumper{f: i.game.Update}
	}
	i.err = i.d.dump(screen)
}

// RunGame starts the main loop and runs the game.
// game's Update function is called every tick to update the gmae logic.
// game's Draw function is, if it exists, called every frame to draw the screen.
// game's Layout function is called when necessary, and you can specify the logical screen size by the function.
//
// game must implement Game interface.
// Game's Draw function is optional, but it is recommended to implement Draw to seperate updating the logic and
// rendering.
//
// RunGame is a more flexibile form of Run due to game's Layout function.
// You can make a resizable window if you use RunGame, while you cannot if you use Run.
// RunGame is more sophisticated way than Run and hides the notion of 'scale'.
//
// While Run specifies the window size, RunGame does not.
// You need to call SetWindowSize before RunGame if you want.
// Otherwise, a default window size is adopted.
//
// Some functions (ScreenScale, SetScreenScale, SetScreenSize) are not available with RunGame.
//
// On browsers, it is strongly recommended to use iframe if you embed an Ebiten application in your website.
//
// RunGame must be called on the main thread.
// Note that Ebiten bounds the main goroutine to the main OS thread by runtime.LockOSThread.
//
// Ebiten tries to call game's Update function 60 times a second by default. In other words,
// TPS (ticks per second) is 60 by default.
// This is not related to framerate (display's refresh rate).
//
// game's Update is not called when the window is in background by default.
// This setting is configurable with SetRunnableOnUnfocused.
//
// On non-GopherJS environments, RunGame returns error when 1) OpenGL error happens, 2) audio error happens or
// 3) f returns error. In the case of 3), RunGame returns the same error.
//
// On GopherJS, RunGame returns immediately.
// It is because the 'main' goroutine cannot be blocked on GopherJS due to the bug (gopherjs/gopherjs#826).
// When an error happens, this is shown as an error on the console.
//
// The size unit is device-independent pixel.
//
// Don't call RunGame twice or more in one process.
func RunGame(game Game) error {
	fixWindowPosition(WindowSize())
	if _, ok := game.(interface{ Draw(*Image) }); ok {
		return runGame(&imageDumperGameWithDraw{
			imageDumperGame: imageDumperGame{game: game},
		}, 0)
	}
	return runGame(&imageDumperGame{game: game}, 0)
}

func runGame(game Game, scale float64) error {
	theUIContext.set(game, scale)
	if err := uiDriver().Run(theUIContext); err != nil {
		if err == driver.RegularTermination {
			return nil
		}
		return err
	}
	return nil
}

// RunGameWithoutMainLoop runs the game, but don't call the loop on the main (UI) thread.
// Different from Run, RunGameWithoutMainLoop returns immediately.
//
// Ebiten users should NOT call RunGameWithoutMainLoop.
// Instead, functions in github.com/hajimehoshi/ebiten/mobile package calls this.
func RunGameWithoutMainLoop(game Game) {
	fixWindowPosition(WindowSize())
	if _, ok := game.(interface{ Draw(*Image) }); ok {
		game = &imageDumperGameWithDraw{
			imageDumperGame: imageDumperGame{game: game},
		}
	} else {
		game = &imageDumperGame{game: game}
	}
	theUIContext.set(game, 0)
	uiDriver().RunWithoutMainLoop(theUIContext)
}

// ScreenSizeInFullscreen returns the size in device-independent pixels when the game is fullscreen.
// The adopted monitor is the 'current' monitor which the window belongs to.
// The returned value can be given to Run or SetSize function if the perfectly fit fullscreen is needed.
//
// On browsers, ScreenSizeInFullscreen returns the 'window' (global object) size, not 'screen' size since an Ebiten
// game should not know the outside of the window object. For more details, see SetFullscreen API comment.
//
// On mobiles, ScreenSizeInFullscreen returns (0, 0) so far.
//
// ScreenSizeInFullscreen's use cases are limited. If you are making a fullscreen application, you can use RunGame and
// the Game interface's Layout function instead. If you are making a not-fullscreen application but the application's
// behavior depends on the monitor size, ScreenSizeInFullscreen is useful.
//
// ScreenSizeInFullscreen must be called on the main thread before ebiten.Run, and is concurrent-safe after
// ebiten.Run.
func ScreenSizeInFullscreen() (int, int) {
	return uiDriver().ScreenSizeInFullscreen()
}

// MonitorSize is deprecated as of 1.8.0-alpha. Use ScreenSizeInFullscreen instead.
func MonitorSize() (int, int) {
	return ScreenSizeInFullscreen()
}

// SetScreenSize is deprecated as of 1.11.0-alpha. Use SetWindowSize and RunGame (Game's Layout) instead.
func SetScreenSize(width, height int) {
	if width <= 0 || height <= 0 {
		panic("ebiten: width and height must be positive")
	}
	theUIContext.setScreenSize(width, height)
}

// SetScreenScale is deprecated as of 1.11.0-alpha. Use SetWindowSize instead.
func SetScreenScale(scale float64) {
	if scale <= 0 {
		panic("ebiten: scale must be positive")
	}
	theUIContext.setScaleForWindow(scale)
}

// ScreenScale is deprecated as of 1.11.0-alpha. Use WindowSize instead.
func ScreenScale() float64 {
	return theUIContext.getScaleForWindow()
}

// CursorMode returns the current cursor mode.
//
// On browsers, only CursorModeVisible and CursorModeHidden are supported.
//
// CursorMode returns CursorModeHidden on mobiles.
//
// CursorMode is concurrent-safe.
func CursorMode() CursorModeType {
	return CursorModeType(uiDriver().CursorMode())
}

// SetCursorMode sets the render and capture mode of the mouse cursor.
// CursorModeVisible sets the cursor to always be visible.
// CursorModeHidden hides the system cursor when over the window.
// CursorModeCaptured hides the system cursor and locks it to the window.
//
// On browsers, only CursorModeVisible and CursorModeHidden are supported.
//
// SetCursorMode does nothing on mobiles.
//
// SetCursorMode is concurrent-safe.
func SetCursorMode(mode CursorModeType) {
	uiDriver().SetCursorMode(driver.CursorMode(mode))
}

// IsCursorVisible is deprecated as of 1.11.0-alpha. Use CursorMode instead.
func IsCursorVisible() bool {
	return CursorMode() == CursorModeVisible
}

// SetCursorVisible is deprecated as of 1.11.0-alpha. Use SetCursorMode instead.
func SetCursorVisible(visible bool) {
	if visible {
		SetCursorMode(CursorModeVisible)
	} else {
		SetCursorMode(CursorModeHidden)
	}
}

// SetCursorVisibility is deprecated as of 1.6.0-alpha. Use SetCursorMode instead.
func SetCursorVisibility(visible bool) {
	SetCursorVisible(visible)
}

// IsFullscreen reports whether the current mode is fullscreen or not.
//
// IsFullscreen always returns false on browsers.
// IsFullscreen works as this as of 1.10.0-alpha.
// Before that, IsFullscreen reported whether the current mode is fullscreen or not.
//
// IsFullscreen always returns false on mobiles.
//
// IsFullscreen is concurrent-safe.
func IsFullscreen() bool {
	return uiDriver().IsFullscreen()
}

// SetFullscreen changes the current mode to fullscreen or not on desktops.
//
// On fullscreen mode, the game screen is automatically enlarged
// to fit with the monitor. The current scale value is ignored.
//
// On desktops, Ebiten uses 'windowed' fullscreen mode, which doesn't change
// your monitor's resolution.
//
// SetFullscreen does nothing on browsers.
// SetFullscreen works as this as of 1.10.0-alpha.
// Before that, SetFullscreen affected the fullscreen mode.
//
// SetFullscreen does nothing on mobiles.
//
// SetFullscreen is concurrent-safe.
func SetFullscreen(fullscreen bool) {
	uiDriver().SetFullscreen(fullscreen)
}

// IsFocused returns a boolean value indicating whether
// the game is in focus or in the foreground.
//
// IsFocused will only return true if IsRunnableOnUnfocused is false.
//
// IsFocused is concurrent-safe.
func IsFocused() bool {
	return uiDriver().IsFocused()
}

// IsRunnableOnUnfocused returns a boolean value indicating whether
// the game runs even in background.
//
// IsRunnableOnUnfocused is concurrent-safe.
func IsRunnableOnUnfocused() bool {
	return uiDriver().IsRunnableOnUnfocused()
}

// IsRunnableInBackground is deprecated as of 1.11.0-alpha. Use IsRunnableOnUnfocused instead.
func IsRunnableInBackground() bool {
	return IsRunnableOnUnfocused()
}

// SetRunnableOnUnfocused sets the state if the game runs even in background.
//
// If the given value is true, the game runs in background e.g. when losing focus.
// The initial state is false.
//
// Known issue: On browsers, even if the state is on, the game doesn't run in background tabs.
// This is because browsers throttles background tabs not to often update.
//
// SetRunnableOnUnfocused does nothing on mobiles so far.
//
// SetRunnableOnUnfocused is concurrent-safe.
func SetRunnableOnUnfocused(runnableOnUnfocused bool) {
	uiDriver().SetRunnableOnUnfocused(runnableOnUnfocused)
}

// SetRunnableInBackground is deprecated as of 1.11.0-alpha. Use SetRunnableOnUnfocused instead.
func SetRunnableInBackground(runnableInBackground bool) {
	SetRunnableOnUnfocused(runnableInBackground)
}

// DeviceScaleFactor returns a device scale factor value of the current monitor which the window belongs to.
//
// DeviceScaleFactor returns a meaningful value on high-DPI display environment,
// otherwise DeviceScaleFactor returns 1.
//
// DeviceScaleFactor might panic on init function on some devices like Android.
// Then, it is not recommended to call DeviceScaleFactor from init functions.
//
// DeviceScaleFactor must be called on the main thread before the main loop, and is concurrent-safe after the main loop.
func DeviceScaleFactor() float64 {
	return uiDriver().DeviceScaleFactor()
}

// IsVsyncEnabled returns a boolean value indicating whether
// the game uses the display's vsync.
//
// IsVsyncEnabled is concurrent-safe.
func IsVsyncEnabled() bool {
	return uiDriver().IsVsyncEnabled()
}

// SetVsyncEnabled sets a boolean value indicating whether
// the game uses the display's vsync.
//
// If the given value is true, the game tries to sync the display's refresh rate.
// If false, the game ignores the display's refresh rate.
// The initial value is true.
// By disabling vsync, the game works more efficiently but consumes more CPU.
//
// Note that the state doesn't affect TPS (ticks per second, i.e. how many the run function is
// updated per second).
//
// SetVsyncEnabled does nothing on mobiles so far.
//
// SetVsyncEnabled is concurrent-safe.
func SetVsyncEnabled(enabled bool) {
	uiDriver().SetVsyncEnabled(enabled)
}

// MaxTPS returns the current maximum TPS.
//
// MaxTPS is concurrent-safe.
func MaxTPS() int {
	return int(atomic.LoadInt32(&currentMaxTPS))
}

// CurrentTPS returns the current TPS (ticks per second),
// that represents how many update function is called in a second.
//
// CurrentTPS is concurrent-safe.
func CurrentTPS() float64 {
	return clock.CurrentTPS()
}

// UncappedTPS is a special TPS value that means the game doesn't have limitation on TPS.
const UncappedTPS = clock.UncappedTPS

// SetMaxTPS sets the maximum TPS (ticks per second),
// that represents how many updating function is called per second.
// The initial value is 60.
//
// If tps is UncappedTPS, TPS is uncapped and the game is updated per frame.
// If tps is negative but not UncappedTPS, SetMaxTPS panics.
//
// SetMaxTPS is concurrent-safe.
func SetMaxTPS(tps int) {
	if tps < 0 && tps != UncappedTPS {
		panic("ebiten: tps must be >= 0 or UncappedTPS")
	}
	atomic.StoreInt32(&currentMaxTPS, int32(tps))
}

// IsScreenTransparent reports whether the window is transparent.
//
// IsScreenTransparent is concurrent-safe.
func IsScreenTransparent() bool {
	return uiDriver().IsScreenTransparent()
}

// SetScreenTransparent sets the state if the window is transparent.
//
// SetScreenTransparent panics if SetScreenTransparent is called after the main loop.
//
// SetScreenTransparent does nothing on mobiles.
//
// SetScreenTransparent is concurrent-safe.
func SetScreenTransparent(transparent bool) {
	uiDriver().SetScreenTransparent(transparent)
}