// Copyright 2015 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.

// +build darwin freebsd linux windows
// +build !js
// +build !android
// +build !ios

package ui

import (
	"image"
	"math"
	"runtime"
	"sync"
	"time"

	"github.com/go-gl/glfw/v3.2/glfw"

	"github.com/hajimehoshi/ebiten/internal/devicescale"
	"github.com/hajimehoshi/ebiten/internal/hooks"
	"github.com/hajimehoshi/ebiten/internal/input"
	"github.com/hajimehoshi/ebiten/internal/mainthread"
)

type userInterface struct {
	title                string
	window               *glfw.Window
	width                int
	windowWidth          int
	height               int
	initMonitor          *glfw.Monitor
	initFullscreenWidth  int
	initFullscreenHeight int

	scale           float64
	fullscreenScale float64

	running              bool
	toChangeSize         bool
	origPosX             int
	origPosY             int
	runnableInBackground bool
	vsync                bool

	lastActualScale float64

	initFullscreen      bool
	initCursorVisible   bool
	initWindowDecorated bool
	initIconImages      []image.Image

	m sync.Mutex
}

var (
	currentUI = &userInterface{
		origPosX:            -1,
		origPosY:            -1,
		initCursorVisible:   true,
		initWindowDecorated: true,
		vsync:               true,
	}
)

func init() {
	runtime.LockOSThread()
	hideConsoleWindowOnWindows()
	if err := initialize(); err != nil {
		panic(err)
	}
	glfw.SetMonitorCallback(func(monitor *glfw.Monitor, event glfw.MonitorEvent) {
		cacheMonitors()
	})
	cacheMonitors()
}

func initialize() error {
	if err := glfw.Init(); err != nil {
		return err
	}
	glfw.WindowHint(glfw.Visible, glfw.False)
	glfw.WindowHint(glfw.Resizable, glfw.False)

	// Create a window to set the initial monitor.
	w, err := glfw.CreateWindow(16, 16, "", nil, nil)
	if err != nil {
		return err
	}
	// TODO: Fix this hack. currentMonitorImpl now requires u.window on POSIX.
	currentUI.window = w
	currentUI.initMonitor = currentUI.currentMonitorImpl()
	v := currentUI.initMonitor.GetVideoMode()
	s := glfwScale()
	currentUI.initFullscreenWidth = int(float64(v.Width) / s)
	currentUI.initFullscreenHeight = int(float64(v.Height) / s)
	currentUI.window.Destroy()
	currentUI.window = nil

	return nil
}

type cachedMonitor struct {
	m  *glfw.Monitor
	vm *glfw.VidMode
	// Pos of monitor in virtual coords
	x int
	y int
}

// monitors is the monitor list cache for desktop glfw compile targets.
// populated by 'cacheMonitors' which is called on init and every
// monitor config change event.
//
// monitors must be manipulated on the main thread.
var monitors []*cachedMonitor

func cacheMonitors() {
	monitors = nil
	ms := glfw.GetMonitors()
	for _, m := range ms {
		x, y := m.GetPos()
		monitors = append(monitors, &cachedMonitor{
			m:  m,
			vm: m.GetVideoMode(),
			x:  x,
			y:  y,
		})
	}
}

// getCachedMonitor returns a monitor for the given window x/y
// returns false if monitor is not found.
//
// getCachedMonitor must be called on the main thread.
func getCachedMonitor(wx, wy int) (*cachedMonitor, bool) {
	for _, m := range monitors {
		if m.x <= wx && wx < m.x+m.vm.Width && m.y <= wy && wy < m.y+m.vm.Height {
			return m, true
		}
	}
	return nil, false
}

func Loop(ch <-chan error) error {
	currentUI.setRunning(true)
	if err := mainthread.Loop(ch); err != nil {
		return err
	}
	currentUI.setRunning(false)
	return nil
}

func (u *userInterface) isRunning() bool {
	u.m.Lock()
	v := u.running
	u.m.Unlock()
	return v
}

func (u *userInterface) setRunning(running bool) {
	u.m.Lock()
	u.running = running
	u.m.Unlock()
}

func (u *userInterface) isInitFullscreen() bool {
	u.m.Lock()
	v := u.initFullscreen
	u.m.Unlock()
	return v
}

func (u *userInterface) setInitFullscreen(initFullscreen bool) {
	u.m.Lock()
	u.initFullscreen = initFullscreen
	u.m.Unlock()
}

func (u *userInterface) isInitCursorVisible() bool {
	u.m.Lock()
	v := u.initCursorVisible
	u.m.Unlock()
	return v
}

func (u *userInterface) setInitCursorVisible(visible bool) {
	u.m.Lock()
	u.initCursorVisible = visible
	u.m.Unlock()
}

func (u *userInterface) isInitWindowDecorated() bool {
	u.m.Lock()
	v := u.initWindowDecorated
	u.m.Unlock()
	return v
}

func (u *userInterface) setInitWindowDecorated(decorated bool) {
	u.m.Lock()
	u.initWindowDecorated = decorated
	u.m.Unlock()
}

func (u *userInterface) isRunnableInBackground() bool {
	u.m.Lock()
	v := u.runnableInBackground
	u.m.Unlock()
	return v
}

func (u *userInterface) setRunnableInBackground(runnableInBackground bool) {
	u.m.Lock()
	u.runnableInBackground = runnableInBackground
	u.m.Unlock()
}

func (u *userInterface) getInitIconImages() []image.Image {
	u.m.Lock()
	i := u.initIconImages
	u.m.Unlock()
	return i
}

func (u *userInterface) setInitIconImages(iconImages []image.Image) {
	u.m.Lock()
	u.initIconImages = iconImages
	u.m.Unlock()
}

func ScreenSizeInFullscreen() (int, int) {
	u := currentUI
	if !u.isRunning() {
		return u.initFullscreenWidth, u.initFullscreenHeight
	}

	var v *glfw.VidMode
	s := 0.0
	_ = mainthread.Run(func() error {
		v = u.currentMonitor().GetVideoMode()
		s = glfwScale()
		return nil
	})
	return int(float64(v.Width) / s), int(float64(v.Height) / s)
}

func SetScreenSize(width, height int) bool {
	u := currentUI
	if !u.isRunning() {
		panic("ui: Run is not called yet")
	}
	r := false
	_ = mainthread.Run(func() error {
		r = u.setScreenSize(width, height, u.scale, u.fullscreen(), u.vsync)
		return nil
	})
	return r
}

func SetScreenScale(scale float64) bool {
	u := currentUI
	if !u.isRunning() {
		panic("ui: Run is not called yet")
	}
	r := false
	_ = mainthread.Run(func() error {
		r = u.setScreenSize(u.width, u.height, scale, u.fullscreen(), u.vsync)
		return nil
	})
	return r
}

func ScreenScale() float64 {
	u := currentUI
	if !u.isRunning() {
		return 0
	}
	s := 0.0
	_ = mainthread.Run(func() error {
		s = u.scale
		return nil
	})
	return s
}

// fullscreen must be called from the main thread.
func (u *userInterface) fullscreen() bool {
	if !u.isRunning() {
		panic("not reached")
	}
	return u.window.GetMonitor() != nil
}

func IsFullscreen() bool {
	u := currentUI
	if !u.isRunning() {
		return u.isInitFullscreen()
	}
	b := false
	_ = mainthread.Run(func() error {
		b = u.fullscreen()
		return nil
	})
	return b
}

func SetFullscreen(fullscreen bool) {
	u := currentUI
	if !u.isRunning() {
		u.setInitFullscreen(fullscreen)
		return
	}
	_ = mainthread.Run(func() error {
		u := currentUI
		u.setScreenSize(u.width, u.height, u.scale, fullscreen, u.vsync)
		return nil
	})
}

func SetRunnableInBackground(runnableInBackground bool) {
	currentUI.setRunnableInBackground(runnableInBackground)
}

func IsRunnableInBackground() bool {
	return currentUI.isRunnableInBackground()
}

func SetVsyncEnabled(enabled bool) {
	u := currentUI
	if !u.isRunning() {
		// In general, m is used for locking init* values.
		// m is not used for updating vsync in setScreenSize so far, but
		// it should be OK since any goroutines can't reach here when
		// the game already starts and setScreenSize can be called.
		u.m.Lock()
		u.vsync = enabled
		u.m.Unlock()
		return
	}
	_ = mainthread.Run(func() error {
		u := currentUI
		u.setScreenSize(u.width, u.height, u.scale, u.fullscreen(), enabled)
		return nil
	})
}

func IsVsyncEnabled() bool {
	u := currentUI
	u.m.Lock()
	r := u.vsync
	u.m.Unlock()
	return r
}

func SetWindowTitle(title string) {
	if !currentUI.isRunning() {
		return
	}
	_ = mainthread.Run(func() error {
		currentUI.window.SetTitle(title)
		return nil
	})
}

func SetWindowIcon(iconImages []image.Image) {
	if !currentUI.isRunning() {
		currentUI.setInitIconImages(iconImages)
		return
	}
	_ = mainthread.Run(func() error {
		currentUI.window.SetIcon(iconImages)
		return nil
	})
}

func ScreenPadding() (x0, y0, x1, y1 float64) {
	u := currentUI
	if !u.isRunning() {
		return 0, 0, 0, 0
	}
	if !IsFullscreen() {
		if u.width == u.windowWidth {
			return 0, 0, 0, 0
		}
		// The window width can be bigger than the game screen width (#444).
		ox := (float64(u.windowWidth)*u.actualScreenScale() - float64(u.width)*u.actualScreenScale()) / 2
		return ox, 0, ox, 0
	}

	m := u.window.GetMonitor()
	d := devicescale.GetAt(m.GetPos())
	v := m.GetVideoMode()

	sx := 0.0
	sy := 0.0
	gs := 0.0
	_ = mainthread.Run(func() error {
		sx = float64(u.width) * u.actualScreenScale()
		sy = float64(u.height) * u.actualScreenScale()
		gs = glfwScale()
		return nil
	})
	mx := float64(v.Width) * d / gs
	my := float64(v.Height) * d / gs

	ox := (mx - sx) / 2
	oy := (my - sy) / 2
	return ox, oy, (mx - sx) - ox, (my - sy) - oy
}

func AdjustedCursorPosition() (x, y int) {
	return adjustCursorPosition(input.Get().CursorPosition())
}

func adjustCursorPosition(x, y int) (int, int) {
	u := currentUI
	if !u.isRunning() {
		return x, y
	}
	ox, oy, _, _ := ScreenPadding()
	s := 0.0
	_ = mainthread.Run(func() error {
		s = currentUI.actualScreenScale()
		return nil
	})
	return x - int(ox/s), y - int(oy/s)
}

func AdjustedTouches() []*input.Touch {
	// TODO: Apply adjustCursorPosition
	return input.Get().Touches()
}

func IsCursorVisible() bool {
	u := currentUI
	if !u.isRunning() {
		return u.isInitCursorVisible()
	}
	v := false
	_ = mainthread.Run(func() error {
		v = currentUI.window.GetInputMode(glfw.CursorMode) == glfw.CursorNormal
		return nil
	})
	return v
}

func SetCursorVisible(visible bool) {
	u := currentUI
	if !u.isRunning() {
		u.setInitCursorVisible(visible)
		return
	}
	_ = mainthread.Run(func() error {
		c := glfw.CursorNormal
		if !visible {
			c = glfw.CursorHidden
		}
		currentUI.window.SetInputMode(glfw.CursorMode, c)
		return nil
	})
}

func IsWindowDecorated() bool {
	u := currentUI
	if !u.isRunning() {
		return u.isInitWindowDecorated()
	}
	v := false
	_ = mainthread.Run(func() error {
		v = currentUI.window.GetAttrib(glfw.Decorated) == glfw.True
		return nil
	})
	return v
}

func SetWindowDecorated(decorated bool) {
	u := currentUI
	if !u.isRunning() {
		u.setInitWindowDecorated(decorated)
		return
	}

	panic("ui: SetWindowDecorated can't be called after Run so far.")

	// TODO: Now SetAttrib doesn't exist on GLFW 3.2. Revisit later (#556).
	// If SetAttrib exists, the implementation would be:
	//
	//     _ = mainthread.Run(func() error {
	//         v := glfw.False
	//         if decorated {
	//             v = glfw.True
	//         }
	//     })
	//     currentUI.window.SetAttrib(glfw.Decorated, v)
	//     return nil
}

func DeviceScaleFactor() float64 {
	f := 0.0
	u := currentUI
	if !u.isRunning() {
		return devicescale.GetAt(u.initMonitor.GetPos())
	}

	_ = mainthread.Run(func() error {
		m := u.currentMonitor()
		f = devicescale.GetAt(m.GetPos())
		return nil
	})
	return f
}

func Run(width, height int, scale float64, title string, g GraphicsContext, mainloop bool) error {
	u := currentUI
	_ = mainthread.Run(func() error {
		glfw.WindowHint(glfw.ContextVersionMajor, 2)
		glfw.WindowHint(glfw.ContextVersionMinor, 1)

		// 'decorated' must be solved before creating a window (#556).
		decorated := glfw.False
		if u.isInitWindowDecorated() {
			decorated = glfw.True
		}
		glfw.WindowHint(glfw.Decorated, decorated)

		// As a start, create a window with temporary size to create OpenGL context thread.
		window, err := glfw.CreateWindow(16, 16, "", nil, nil)
		if err != nil {
			return err
		}
		u.window = window

		u.window.MakeContextCurrent()

		u.window.SetInputMode(glfw.StickyMouseButtonsMode, glfw.True)
		u.window.SetInputMode(glfw.StickyKeysMode, glfw.True)

		// Solve the initial properties of the window.
		mode := glfw.CursorNormal
		if !u.isInitCursorVisible() {
			mode = glfw.CursorHidden
		}
		u.window.SetInputMode(glfw.CursorMode, mode)

		if i := u.getInitIconImages(); i != nil {
			u.window.SetIcon(i)
		}

		// Get the monitor before showing the window.
		//
		// On Windows, there are two types of windows:
		//
		//   active window:     The window that has input-focus and attached to the calling thread.
		//   foreground window: The window that has input-focus: this can be in another process
		//
		// currentMonitor returns the monitor for the active window when possible and then the monitor for
		// the foreground window as fallback. In the current situation, the current window is hidden and
		// there is not the active window but the foreground window. After showing the current window, the
		// current window will be the active window. Thus, currentMonitor retuls varies before and after
		// showing the window.
		m := u.currentMonitor()
		mx, my := m.GetPos()
		v := m.GetVideoMode()

		// The game is in window mode (not fullscreen mode) at the first state.
		// Don't refer u.initFullscreen here to avoid some GLFW problems.
		u.setScreenSize(width, height, scale, false, u.vsync)
		// Get the window size before showing since window.Show might change the current
		// monitor which affects glfwSize result.
		w, h := u.glfwSize()

		u.title = title
		u.window.SetTitle(title)
		u.window.Show()

		x := mx + (v.Width-w)/2
		y := my + (v.Height-h)/3
		x, y = adjustWindowPosition(x, y)
		u.window.SetPos(x, y)
		return nil
	})
	return u.loop(g)
}

// getSize must be called from the main thread.
func (u *userInterface) glfwSize() (int, int) {
	w := int(float64(u.windowWidth) * u.getScale() * glfwScale())
	h := int(float64(u.height) * u.getScale() * glfwScale())
	return w, h
}

// getScale must be called from the main thread.
func (u *userInterface) getScale() float64 {
	if !u.fullscreen() {
		return u.scale
	}
	if u.fullscreenScale == 0 {
		v := u.window.GetMonitor().GetVideoMode()
		sw := float64(v.Width) / glfwScale() / float64(u.width)
		sh := float64(v.Height) / glfwScale() / float64(u.height)
		s := sw
		if s > sh {
			s = sh
		}
		u.fullscreenScale = s
	}
	return u.fullscreenScale
}

// actualScreenScale must be called from the main thread.
func (u *userInterface) actualScreenScale() float64 {
	// Avoid calling monitor.GetPos if we have the monitor position cached already.
	if cm, ok := getCachedMonitor(u.window.GetPos()); ok {
		return u.getScale() * devicescale.GetAt(cm.x, cm.y)
	}
	return u.getScale() * devicescale.GetAt(u.currentMonitor().GetPos())
}

// pollEvents must be called from the main thread.
func (u *userInterface) pollEvents() {
	glfw.PollEvents()
	input.Get().Update(u.window, u.getScale()*glfwScale())
}

func (u *userInterface) updateGraphicsContext(g GraphicsContext) {
	actualScale := 0.0
	sizeChanged := false
	// TODO: Is it possible to reduce 'runOnMainThread' calls?
	_ = mainthread.Run(func() error {
		actualScale = u.actualScreenScale()
		if u.lastActualScale != actualScale {
			u.forceSetScreenSize(u.width, u.height, u.scale, u.fullscreen(), u.vsync)
		}
		u.lastActualScale = actualScale

		if !u.toChangeSize {
			return nil
		}

		u.toChangeSize = false
		sizeChanged = true
		return nil
	})
	if sizeChanged {
		g.SetSize(u.width, u.height, actualScale)
	}
}

func (u *userInterface) update(g GraphicsContext) error {
	shouldClose := false
	_ = mainthread.Run(func() error {
		shouldClose = u.window.ShouldClose()
		return nil
	})
	if shouldClose {
		return RegularTermination
	}

	_ = mainthread.Run(func() error {
		if u.isInitFullscreen() {
			u := currentUI
			u.setScreenSize(u.width, u.height, u.scale, true, u.vsync)
			u.setInitFullscreen(false)
		}
		return nil
	})

	// This call is needed for initialization.
	u.updateGraphicsContext(g)

	_ = mainthread.Run(func() error {
		u.pollEvents()
		defer hooks.ResumeAudio()
		for !u.isRunnableInBackground() && u.window.GetAttrib(glfw.Focused) == 0 {
			hooks.SuspendAudio()
			// Wait for an arbitrary period to avoid busy loop.
			time.Sleep(time.Second / 60)
			u.pollEvents()
			if u.window.ShouldClose() {
				return nil
			}
		}
		return nil
	})
	if err := g.Update(func() {
		input.Get().ClearRuneBuffer()
		input.Get().ResetScrollValues()
		// The offscreens must be updated every frame (#490).
		u.updateGraphicsContext(g)
	}); err != nil {
		return err
	}
	return nil
}

func (u *userInterface) loop(g GraphicsContext) error {
	defer func() {
		_ = mainthread.Run(func() error {
			glfw.Terminate()
			return nil
		})
	}()
	for {
		if err := u.update(g); err != nil {
			return err
		}

		u.m.Lock()
		vsync := u.vsync
		u.m.Unlock()

		_ = mainthread.Run(func() error {
			if !vsync {
				u.swapBuffers()
				return nil
			}

			n1 := time.Now().UnixNano()
			u.swapBuffers()
			n2 := time.Now().UnixNano()
			d := time.Duration(n2 - n1)

			// On macOS Mojave, vsync might not work (#692).
			// As a tempoarry fix, just wait for a while not to consume CPU too much.
			const threshold = 4 * time.Millisecond // 250 [Hz]
			if d < threshold {
				time.Sleep(threshold - d)
			}
			return nil
		})
	}
}

// swapBuffers must be called from the main thread.
func (u *userInterface) swapBuffers() {
	u.window.SwapBuffers()
}

// setScreenSize must be called from the main thread.
func (u *userInterface) setScreenSize(width, height int, scale float64, fullscreen bool, vsync bool) bool {
	if u.width == width && u.height == height && u.scale == scale && u.fullscreen() == fullscreen && u.vsync == vsync {
		return false
	}
	u.forceSetScreenSize(width, height, scale, fullscreen, vsync)
	return true
}

// forceSetScreenSize must be called from the main thread.
func (u *userInterface) forceSetScreenSize(width, height int, scale float64, fullscreen bool, vsync bool) {
	// On Windows, giving a too small width doesn't call a callback (#165).
	// To prevent hanging up, return asap if the width is too small.
	// 252 is an arbitrary number and I guess this is small enough.
	const minWindowWidth = 252

	u.width = width
	u.windowWidth = width
	s := scale * devicescale.GetAt(u.currentMonitor().GetPos())
	if int(float64(width)*s) < minWindowWidth {
		u.windowWidth = int(math.Ceil(minWindowWidth / s))
	}
	u.height = height
	u.scale = scale
	u.fullscreenScale = 0
	u.vsync = vsync

	// To make sure the current existing framebuffers are rendered,
	// swap buffers here before SetSize is called.
	u.swapBuffers()

	if fullscreen {
		if u.origPosX < 0 && u.origPosY < 0 {
			u.origPosX, u.origPosY = u.window.GetPos()
		}
		m := u.currentMonitor()
		v := m.GetVideoMode()
		u.window.SetMonitor(m, 0, 0, v.Width, v.Height, v.RefreshRate)
	} else {
		if u.window.GetMonitor() != nil {
			// Give dummy values as the window position and size.
			// The new window position should be specifying after SetSize.
			u.window.SetMonitor(nil, 0, 0, 16, 16, 0)
		}

		oldW, oldH := u.window.GetSize()
		newW, newH := u.glfwSize()
		if oldW != newW || oldH != newH {
			ch := make(chan struct{})
			u.window.SetFramebufferSizeCallback(func(_ *glfw.Window, _, _ int) {
				u.window.SetFramebufferSizeCallback(nil)
				close(ch)
			})
			u.window.SetSize(u.glfwSize())
		event:
			for {
				glfw.PollEvents()
				select {
				case <-ch:
					break event
				default:
				}
			}
		}

		if u.origPosX >= 0 && u.origPosY >= 0 {
			x := u.origPosX
			y := u.origPosY
			u.window.SetPos(x, y)
			// Dirty hack for macOS (#703). Rendering doesn't work correctly with one SetPos, but work
			// with two or more SetPos.
			if runtime.GOOS == "darwin" {
				u.window.SetPos(x+1, y)
				u.window.SetPos(x, y)
			}
			u.origPosX = -1
			u.origPosY = -1
		}

		// Window title might be lost on macOS after coming back from fullscreen.
		u.window.SetTitle(u.title)
	}

	// SwapInterval is affected by the current monitor of the window.
	// This needs to be called at least after SetMonitor.
	// Without SwapInterval after SetMonitor, vsynch doesn't work (#375).
	//
	// TODO: (#405) If triple buffering is needed, SwapInterval(0) should be called,
	// but is this correct? If glfw.SwapInterval(0) and the driver doesn't support triple
	// buffering, what will happen?
	if u.vsync {
		glfw.SwapInterval(1)
	} else {
		glfw.SwapInterval(0)
	}

	u.toChangeSize = true
}

// currentMonitor returns the monitor most suitable with the current window.
//
// currentMonitor must be called on the main thread.
func (u *userInterface) currentMonitor() *glfw.Monitor {
	w := u.window
	if m := w.GetMonitor(); m != nil {
		return m
	}
	// Get the monitor which the current window belongs to. This requires OS API.
	return u.currentMonitorImpl()
}