package gui

import (
	"math"

	"github.com/go-gl/gl/all-core/gl"
	"gitlab.com/liamg/raft/buffer"
	"gitlab.com/liamg/raft/config"
	"gitlab.com/liamg/raft/glfont"
)

type Renderer interface {
	SetArea(areaX int, areaY int, areaWidth int, areaHeight int)
	DrawCellBg(cell buffer.Cell, col uint, row uint)
	DrawCellText(cell buffer.Cell, col uint, row uint)
	DrawCursor(col uint, row uint, colour config.Colour)
	GetTermSize() (uint, uint)
	CellWidth() float32
	CellHeight() float32
}

type OpenGLRenderer struct {
	font          *glfont.Font
	areaWidth     int
	areaHeight    int
	areaX         int
	areaY         int
	cellWidth     float32
	cellHeight    float32
	termCols      uint
	termRows      uint
	cellPositions map[[2]uint][2]float32
	rectangles    map[[2]uint]*rectangle
	config        *config.Config
	colourAttr    uint32
	program       uint32
}

type rectangle struct {
	vao        uint32
	vbo        uint32
	cv         uint32
	colourAttr uint32
	colour     [3]float32
	points     []float32
	prog       uint32
}

func (r *OpenGLRenderer) CellWidth() float32 {
	return r.cellWidth
}

func (r *OpenGLRenderer) CellHeight() float32 {
	return r.cellHeight
}

func (r *OpenGLRenderer) newRectangle(x float32, y float32, colourAttr uint32) *rectangle {

	halfAreaWidth := float32(r.areaWidth / 2)
	halfAreaHeight := float32(r.areaHeight / 2)

	x = (x - halfAreaWidth) / halfAreaWidth
	y = -(y - halfAreaHeight) / halfAreaHeight
	w := r.cellWidth / halfAreaWidth
	h := r.cellHeight / halfAreaHeight

	rect := &rectangle{
		points: []float32{
			x, y, 0,
			x, y + h, 0,
			x + w, y + h, 0,

			x + w, y, 0,
			x, y, 0,
			x + w, y + h, 0,
		},
		colourAttr: colourAttr,
		prog:       r.program,
	}

	gl.UseProgram(rect.prog)

	// SHAPE
	gl.GenBuffers(1, &rect.vbo)
	gl.BindBuffer(gl.ARRAY_BUFFER, rect.vbo)
	gl.BufferData(gl.ARRAY_BUFFER, 4*len(rect.points), gl.Ptr(rect.points), gl.STATIC_DRAW)

	gl.GenVertexArrays(1, &rect.vao)
	gl.BindVertexArray(rect.vao)
	gl.EnableVertexAttribArray(0)

	gl.BindBuffer(gl.ARRAY_BUFFER, rect.vbo)
	gl.VertexAttribPointer(0, 3, gl.FLOAT, false, 0, nil)

	// colour
	gl.GenBuffers(1, &rect.cv)

	rect.setColour([3]float32{0, 1, 0})

	return rect
}

func (rect *rectangle) Draw() {
	gl.UseProgram(rect.prog)
	gl.BindVertexArray(rect.vao)
	gl.DrawArrays(gl.TRIANGLES, 0, 6)
}

func (rect *rectangle) setColour(colour [3]float32) {
	if rect.colour == colour {
		return
	}

	c := []float32{
		colour[0], colour[1], colour[2],
		colour[0], colour[1], colour[2],
		colour[0], colour[1], colour[2],
		colour[0], colour[1], colour[2],
		colour[0], colour[1], colour[2],
		colour[0], colour[1], colour[2],
	}

	gl.UseProgram(rect.prog)
	gl.BindBuffer(gl.ARRAY_BUFFER, rect.cv)
	gl.BufferData(gl.ARRAY_BUFFER, len(c)*4, gl.Ptr(c), gl.STATIC_DRAW)
	gl.EnableVertexAttribArray(rect.colourAttr)
	gl.VertexAttribPointer(rect.colourAttr, 3, gl.FLOAT, false, 0, gl.PtrOffset(0))

	rect.colour = colour
}

func (rect *rectangle) Free() {
	gl.UseProgram(rect.prog)
	gl.DeleteVertexArrays(1, &rect.vao)
	gl.DeleteBuffers(1, &rect.vbo)
	gl.DeleteBuffers(1, &rect.cv)
}

func NewOpenGLRenderer(config *config.Config, font *glfont.Font, areaX int, areaY int, areaWidth int, areaHeight int, colourAttr uint32, program uint32) *OpenGLRenderer {
	r := &OpenGLRenderer{
		areaWidth:     areaWidth,
		areaHeight:    areaHeight,
		areaX:         areaX,
		areaY:         areaY,
		cellPositions: map[[2]uint][2]float32{},
		rectangles:    map[[2]uint]*rectangle{},
		config:        config,
		colourAttr:    colourAttr,
		program:       program,
	}
	r.SetFont(font)
	return r
}

func (r *OpenGLRenderer) GetTermSize() (uint, uint) {
	return r.termCols, r.termRows
}

func (r *OpenGLRenderer) SetArea(areaX int, areaY int, areaWidth int, areaHeight int) {
	r.areaWidth = areaWidth
	r.areaHeight = areaHeight
	r.areaX = areaX
	r.areaY = areaY
	r.SetFont(r.font)
}

func (r *OpenGLRenderer) SetFont(font *glfont.Font) { // @todo check for monospace and return error if not?
	r.font = font
	r.cellWidth, _ = font.Size("X")
	r.cellHeight = font.LineHeight() // vertical padding
	r.termCols = uint(math.Floor(float64(float32(r.areaWidth) / r.cellWidth)))
	r.termRows = uint(math.Floor(float64(float32(r.areaHeight) / r.cellHeight)))
	r.rectangles = map[[2]uint]*rectangle{}
}

func (r *OpenGLRenderer) getRectangle(col uint, row uint) *rectangle {
	if rect, ok := r.rectangles[[2]uint{col, row}]; ok {
		return rect
	}
	return r.generateRectangle(col, row)
}

func (r *OpenGLRenderer) generateRectangle(col uint, line uint) *rectangle {

	rect, ok := r.rectangles[[2]uint{col, line}]
	if ok {
		rect.Free()
	}

	// rounding to whole pixels makes everything nice
	x := float32(float32(col) * r.cellWidth)
	y := float32((float32(line) * r.cellHeight)) + r.cellHeight + (r.font.LinePadding() / 2)
	r.rectangles[[2]uint{col, line}] = r.newRectangle(x, y, r.colourAttr)
	return r.rectangles[[2]uint{col, line}]
}

func (r *OpenGLRenderer) DrawCursor(col uint, row uint, colour config.Colour) {
	rect := r.getRectangle(col, row)
	rect.setColour(colour)
	rect.Draw()
}

func (r *OpenGLRenderer) DrawCellBg(cell buffer.Cell, col uint, row uint) {

	var bg [3]float32

	if cell.Attr().Reverse {
		bg = cell.Fg()
	} else {
		bg = cell.Bg()
	}

	if bg != r.config.ColourScheme.Background {
		rect := r.getRectangle(col, row)
		rect.setColour(bg)
		rect.Draw()
	}
}

func (r *OpenGLRenderer) DrawCellText(cell buffer.Cell, col uint, row uint) {

	var fg [3]float32

	if cell.Attr().Reverse {
		fg = cell.Bg()
	} else {
		fg = cell.Fg()
	}

	var alpha float32 = 1
	if cell.Attr().Dim {
		alpha = 0.5
	}
	r.font.SetColor(fg[0], fg[1], fg[2], alpha)

	x := float32(col) * r.cellWidth
	y := (float32(row+1) * r.cellHeight) - (r.font.LinePadding() / 2)

	if cell.Attr().Bold { // bold means draw text again one pixel to right, so it's fatter
		r.font.Print(x+1, y, string(cell.Rune()))
	}
	r.font.Print(x, y, string(cell.Rune()))

}