// Copyright 2016 The G3N Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package window

import (
	"runtime"

	"github.com/g3n/engine/core"
	"github.com/go-gl/glfw/v3.2/glfw"
)

// glfwManager contains data shared by all windows
type glfwManager struct {
	arrowCursor     *glfw.Cursor // Preallocated standard arrow cursor
	ibeamCursor     *glfw.Cursor // Preallocated standard ibeam cursor
	crosshairCursor *glfw.Cursor // Preallocated standard cross hair cursor
	handCursor      *glfw.Cursor // Preallocated standard hand cursor
	hresizeCursor   *glfw.Cursor // Preallocated standard horizontal resize cursor
	vresizeCursor   *glfw.Cursor // Preallocated standard vertical resize cursor
}

// glfwWindow describes one glfw window
type glfwWindow struct {
	core.Dispatcher              // Embedded event dispatcher
	win             *glfw.Window // Pointer to native glfw window
	mgr             *glfwManager // Pointer to window manager
	keyEv           KeyEvent
	charEv          CharEvent
	mouseEv         MouseEvent
	posEv           PosEvent
	sizeEv          SizeEvent
	cursorEv        CursorEvent
	scrollEv        ScrollEvent
	fullScreen      bool
	lastX           int
	lastY           int
	lastWidth       int
	lastHeight      int
	scaleX          float64
	scaleY          float64
}

// glfw manager singleton
var manager *glfwManager

// Glfw returns the glfw window manager
func Glfw() (IWindowManager, error) {

	if manager != nil {
		return manager, nil
	}

	// Initialize glfw
	err := glfw.Init()
	if err != nil {
		return nil, err
	}

	// Sets window hints
	glfw.WindowHint(glfw.ContextVersionMajor, 3)
	glfw.WindowHint(glfw.ContextVersionMinor, 3)
	glfw.WindowHint(glfw.OpenGLProfile, glfw.OpenGLCoreProfile)
	glfw.WindowHint(glfw.Samples, 8)
	// Sets OpenGL forward compatible context only for OSX because it is required for OSX.
	// When this is set, glLineWidth(width) only accepts width=1.0 and generates an  error
	// for any other values although the spec says it should ignore unsupported widths
	// and generate an error only when width <= 0.
	if runtime.GOOS == "darwin" {
		glfw.WindowHint(glfw.OpenGLForwardCompatible, glfw.True)
	}

	manager = new(glfwManager)
	return manager, nil
}

// ScreenResolution returns the screen resolution
func (m *glfwManager) ScreenResolution(p interface{}) (width, height int) {

	mon := glfw.GetPrimaryMonitor()
	vmode := mon.GetVideoMode()
	return vmode.Width, vmode.Height
}

// PollEvents process events in the event queue
func (m *glfwManager) PollEvents() {

	glfw.PollEvents()
}

// SetSwapInterval sets the number of screen updates to wait from the time SwapBuffer()
// is called before swapping the buffers and returning.
func (m *glfwManager) SetSwapInterval(interval int) {

	glfw.SwapInterval(interval)
}

// Terminate destroys any remainding window, cursors and other related objects.
func (m *glfwManager) Terminate() {

	glfw.Terminate()
	manager = nil
}

// CreateWindow creates and returns a new window with the specified width and height in screen coordinates
func (m *glfwManager) CreateWindow(width, height int, title string, fullscreen bool) (IWindow, error) {

	// Creates window and sets it as the current context.
	// The window is created always as not full screen because if it is
	// created as full screen it not possible to revert it to windowed mode.
	// At the end of this function, the window will be set to full screen if requested.
	win, err := glfw.CreateWindow(width, height, title, nil, nil)
	if err != nil {
		return nil, err
	}
	win.MakeContextCurrent()

	// Create wrapper window with dispacher
	w := new(glfwWindow)
	w.win = win
	w.mgr = m
	w.Dispatcher.Initialize()

	fbw, fbh := w.FramebufferSize()
	w.scaleX = float64(fbw) / float64(width)
	w.scaleY = float64(fbh) / float64(height)

	// Set key callback to dispatch event
	win.SetKeyCallback(func(x *glfw.Window, key glfw.Key, scancode int, action glfw.Action, mods glfw.ModifierKey) {

		w.keyEv.W = w
		w.keyEv.Keycode = Key(key)
		w.keyEv.Scancode = scancode
		w.keyEv.Action = Action(action)
		w.keyEv.Mods = ModifierKey(mods)
		if action == glfw.Press {
			w.Dispatch(OnKeyDown, &w.keyEv)
			return
		}
		if action == glfw.Release {
			w.Dispatch(OnKeyUp, &w.keyEv)
			return
		}
		if action == glfw.Repeat {
			w.Dispatch(OnKeyRepeat, &w.keyEv)
			return
		}
	})

	// Set char callback
	win.SetCharModsCallback(func(x *glfw.Window, char rune, mods glfw.ModifierKey) {

		w.charEv.W = w
		w.charEv.Char = char
		w.charEv.Mods = ModifierKey(mods)
		w.Dispatch(OnChar, &w.charEv)
	})

	// Set mouse button callback to dispatch event
	win.SetMouseButtonCallback(func(x *glfw.Window, button glfw.MouseButton, action glfw.Action, mods glfw.ModifierKey) {

		xpos, ypos := x.GetCursorPos()

		w.mouseEv.W = w
		w.mouseEv.Button = MouseButton(button)
		w.mouseEv.Action = Action(action)
		w.mouseEv.Mods = ModifierKey(mods)
		w.mouseEv.Xpos = float32(xpos * w.scaleX)
		w.mouseEv.Ypos = float32(ypos * w.scaleY)

		if action == glfw.Press {
			w.Dispatch(OnMouseDown, &w.mouseEv)
			return
		}
		if action == glfw.Release {
			w.Dispatch(OnMouseUp, &w.mouseEv)
			return
		}
	})

	// Set window size callback to dispatch event
	win.SetSizeCallback(func(x *glfw.Window, width int, height int) {

		fbw, fbh := x.GetFramebufferSize()
		w.sizeEv.W = w
		w.sizeEv.Width = width
		w.sizeEv.Height = height
		w.scaleX = float64(fbw) / float64(width)
		w.scaleY = float64(fbh) / float64(height)
		w.Dispatch(OnWindowSize, &w.sizeEv)
	})

	// Set window position event callback to dispatch event
	win.SetPosCallback(func(x *glfw.Window, xpos int, ypos int) {

		w.posEv.W = w
		w.posEv.Xpos = xpos
		w.posEv.Ypos = ypos
		w.Dispatch(OnWindowPos, &w.posEv)
	})

	// Set window cursor position event callback to dispatch event
	win.SetCursorPosCallback(func(x *glfw.Window, xpos float64, ypos float64) {

		w.cursorEv.W = w
		w.cursorEv.Xpos = float32(xpos * w.scaleX)
		w.cursorEv.Ypos = float32(ypos * w.scaleY)
		w.Dispatch(OnCursor, &w.cursorEv)
	})

	// Set mouse wheel scroll event callback to dispatch event
	win.SetScrollCallback(func(x *glfw.Window, xoff float64, yoff float64) {

		w.scrollEv.W = w
		w.scrollEv.Xoffset = float32(xoff)
		w.scrollEv.Yoffset = float32(yoff)
		w.Dispatch(OnScroll, &w.scrollEv)
	})

	// Preallocate standard cursors
	w.mgr.arrowCursor = glfw.CreateStandardCursor(glfw.ArrowCursor)
	w.mgr.ibeamCursor = glfw.CreateStandardCursor(glfw.IBeamCursor)
	w.mgr.crosshairCursor = glfw.CreateStandardCursor(glfw.CrosshairCursor)
	w.mgr.handCursor = glfw.CreateStandardCursor(glfw.HandCursor)
	w.mgr.hresizeCursor = glfw.CreateStandardCursor(glfw.HResizeCursor)
	w.mgr.vresizeCursor = glfw.CreateStandardCursor(glfw.VResizeCursor)

	// Sets full screen if requested
	if fullscreen {
		w.SetFullScreen(true)
	}
	return w, nil
}

// MakeContextCurrent makes the OpenGL context of this window current on the calling thread
func (w *glfwWindow) MakeContextCurrent() {

	w.win.MakeContextCurrent()
}

// FullScreen returns this window full screen state for the primary monitor
func (w *glfwWindow) FullScreen() bool {

	return w.fullScreen
}

// SetFullScreen sets this window full screen state for the primary monitor
func (w *glfwWindow) SetFullScreen(full bool) {

	// If already in the desired state, nothing to do
	if w.fullScreen == full {
		return
	}
	// Sets this window full screen for the primary monitor
	if full {
		// Get primary monitor
		mon := glfw.GetPrimaryMonitor()
		vmode := mon.GetVideoMode()
		width := vmode.Width
		height := vmode.Height
		// Saves current position and size of the window
		w.lastX, w.lastY = w.win.GetPos()
		w.lastWidth, w.lastHeight = w.win.GetSize()
		// Sets monitor for full screen
		w.win.SetMonitor(mon, 0, 0, width, height, vmode.RefreshRate)
		w.fullScreen = true
	} else {
		// Restore window to previous position and size
		w.win.SetMonitor(nil, w.lastX, w.lastY, w.lastWidth, w.lastHeight, glfw.DontCare)
		w.fullScreen = false
	}
}

// Destroy destroys this window and its context
func (w *glfwWindow) Destroy() {

	w.win.Destroy()
	w.win = nil
}

// SwapBuffers swaps the front and back buffers of this window.
// If the swap interval is greater than zero,
// the GPU driver waits the specified number of screen updates before swapping the buffers.
func (w *glfwWindow) SwapBuffers() {

	w.win.SwapBuffers()
}

// FramebufferSize returns framebuffer size of this window
func (w *glfwWindow) FramebufferSize() (width int, height int) {

	return w.win.GetFramebufferSize()
}

// Scale returns this window's DPI scale factor (FramebufferSize / Size)
func (w *glfwWindow) Scale() (x float64, y float64) {

	return w.scaleX, w.scaleY
}

// Size returns this window's size in screen coordinates
func (w *glfwWindow) Size() (width int, height int) {

	return w.win.GetSize()
}

// SetSize sets the size, in screen coordinates, of the client area of this window
func (w *glfwWindow) SetSize(width int, height int) {

	w.win.SetSize(width, height)
}

// Pos returns the position, in screen coordinates, of the upper-left corner of the client area of this window
func (w *glfwWindow) Pos() (xpos, ypos int) {

	return w.win.GetPos()
}

// SetPos sets the position, in screen coordinates, of the upper-left corner of the client area of this window.
// If the window is a full screen window, this function does nothing.
func (w *glfwWindow) SetPos(xpos, ypos int) {

	w.win.SetPos(xpos, ypos)
}

// SetTitle sets this window title, encoded as UTF-8
func (w *glfwWindow) SetTitle(title string) {

	w.win.SetTitle(title)
}

// ShouldClose returns the current state of this window  should close flag
func (w *glfwWindow) ShouldClose() bool {

	return w.win.ShouldClose()
}

// SetShouldClose sets the state of this windows should close flag
func (w *glfwWindow) SetShouldClose(v bool) {

	w.win.SetShouldClose(v)
}

// SetStandardCursor sets this window standard cursor type
func (w *glfwWindow) SetStandardCursor(cursor StandardCursor) {

	switch cursor {
	case ArrowCursor:
		w.win.SetCursor(w.mgr.arrowCursor)
	case IBeamCursor:
		w.win.SetCursor(w.mgr.ibeamCursor)
	case CrosshairCursor:
		w.win.SetCursor(w.mgr.crosshairCursor)
	case HandCursor:
		w.win.SetCursor(w.mgr.handCursor)
	case HResizeCursor:
		w.win.SetCursor(w.mgr.hresizeCursor)
	case VResizeCursor:
		w.win.SetCursor(w.mgr.vresizeCursor)
	default:
		panic("Invalid cursor")
	}
}

// SetInputMode changes specified input to specified state
// Reference: http://www.glfw.org/docs/latest/group__input.html#gaa92336e173da9c8834558b54ee80563b
func (w *glfwWindow) SetInputMode(mode InputMode, state int) {

	w.win.SetInputMode(glfw.InputMode(mode), state)
}

// SetCursorPos sets cursor position in window coordinates
// Reference: http://www.glfw.org/docs/latest/group__input.html#ga04b03af936d906ca123c8f4ee08b39e7
func (w *glfwWindow) SetCursorPos(xpos, ypos float64) {

	w.win.SetCursorPos(xpos, ypos)
}