package levels

import (
	mgl "github.com/go-gl/mathgl/mgl32"

	"github.com/inkyblackness/hacked/editor/graphics"
	"github.com/inkyblackness/hacked/editor/render"
	"github.com/inkyblackness/hacked/ui/opengl"
)

var mapIconsVertexShaderSource = `
#version 150
precision mediump float;

in vec3 vertexPosition;
in vec3 uvPosition;

uniform mat4 modelMatrix;
uniform mat4 viewMatrix;
uniform mat4 projectionMatrix;
uniform vec4 uvLimit;

out vec2 uv;

void main(void) {
	gl_Position = projectionMatrix * viewMatrix * modelMatrix * vec4(vertexPosition, 1.0);

	uv = vec2(uvPosition.x * uvLimit.x, uvPosition.y * uvLimit.y);
}
`

var mapIconsFragmentShaderSource = `
#version 150
precision mediump float;

uniform sampler2D palette;
uniform sampler2D bitmap;

in vec2 uv;
out vec4 fragColor;

void main(void) {
	vec4 pixel = texture(bitmap, uv);

	if (pixel.r > 0.0) {
		fragColor = texture(palette, vec2(pixel.r, 0.5));
	} else {
		discard;
	}
}
`

// MapIcons is a renderable for simple bitmaps.
type MapIcons struct {
	context *render.Context

	program                 uint32
	vao                     *opengl.VertexArrayObject
	vertexPositionBuffer    uint32
	vertexPositionAttrib    int32
	uvPositionBuffer        uint32
	uvPositionAttrib        int32
	modelMatrixUniform      opengl.Matrix4Uniform
	viewMatrixUniform       opengl.Matrix4Uniform
	projectionMatrixUniform opengl.Matrix4Uniform
	uvLimitUniform          opengl.Vector4Uniform

	paletteUniform int32
	bitmapUniform  int32
}

type iconData struct {
	pos     MapPosition
	texture *graphics.BitmapTexture
}

// NewMapIcons returns a new instance.
func NewMapIcons(context *render.Context) *MapIcons {
	gl := context.OpenGL
	program, programErr := opengl.LinkNewStandardProgram(gl, mapIconsVertexShaderSource, mapIconsFragmentShaderSource)

	if programErr != nil {
		panic(opengl.NamedShaderError{Name: "MapIconsShader", Nested: programErr})
	}
	renderable := &MapIcons{
		context: context,
		program: program,

		vao:                     opengl.NewVertexArrayObject(gl, program),
		vertexPositionBuffer:    gl.GenBuffers(1)[0],
		vertexPositionAttrib:    gl.GetAttribLocation(program, "vertexPosition"),
		uvPositionBuffer:        gl.GenBuffers(1)[0],
		uvPositionAttrib:        gl.GetAttribLocation(program, "uvPosition"),
		modelMatrixUniform:      opengl.Matrix4Uniform(gl.GetUniformLocation(program, "modelMatrix")),
		viewMatrixUniform:       opengl.Matrix4Uniform(gl.GetUniformLocation(program, "viewMatrix")),
		projectionMatrixUniform: opengl.Matrix4Uniform(gl.GetUniformLocation(program, "projectionMatrix")),
		uvLimitUniform:          opengl.Vector4Uniform(gl.GetUniformLocation(program, "uvLimit")),

		paletteUniform: gl.GetUniformLocation(program, "palette"),
		bitmapUniform:  gl.GetUniformLocation(program, "bitmap")}

	{
		half := float32(0.5)
		var vertices = []float32{
			-half, half, 0.0,
			half, half, 0.0,
			half, -half, 0.0,

			half, -half, 0.0,
			-half, -half, 0.0,
			-half, half, 0.0,
		}
		gl.BindBuffer(opengl.ARRAY_BUFFER, renderable.vertexPositionBuffer)
		gl.BufferData(opengl.ARRAY_BUFFER, len(vertices)*4, vertices, opengl.STATIC_DRAW)
		gl.BindBuffer(opengl.ARRAY_BUFFER, 0)
	}
	{
		var uv = []float32{
			0.0, 0.0, 0.0,
			1.0, 0.0, 0.0,
			1.0, 1.0, 0.0,

			1.0, 1.0, 0.0,
			0.0, 1.0, 0.0,
			0.0, 0.0, 0.0,
		}
		gl.BindBuffer(opengl.ARRAY_BUFFER, renderable.uvPositionBuffer)
		gl.BufferData(opengl.ARRAY_BUFFER, len(uv)*4, uv, opengl.STATIC_DRAW)
		gl.BindBuffer(opengl.ARRAY_BUFFER, 0)
	}
	renderable.vao.WithSetter(func(gl opengl.OpenGL) {
		gl.EnableVertexAttribArray(uint32(renderable.vertexPositionAttrib))
		gl.BindBuffer(opengl.ARRAY_BUFFER, renderable.vertexPositionBuffer)
		gl.VertexAttribOffset(uint32(renderable.vertexPositionAttrib), 3, opengl.FLOAT, false, 0, 0)
		gl.EnableVertexAttribArray(uint32(renderable.uvPositionAttrib))
		gl.BindBuffer(opengl.ARRAY_BUFFER, renderable.uvPositionBuffer)
		gl.VertexAttribOffset(uint32(renderable.uvPositionAttrib), 3, opengl.FLOAT, false, 0, 0)
		gl.BindBuffer(opengl.ARRAY_BUFFER, 0)
	})

	return renderable
}

// Render renders the icons with their center at given position.
func (renderable *MapIcons) Render(paletteTexture *graphics.PaletteTexture, iconSize float32, icons []iconData) {
	gl := renderable.context.OpenGL

	renderable.vao.OnShader(func() {
		renderable.viewMatrixUniform.Set(gl, renderable.context.ViewMatrix)
		renderable.projectionMatrixUniform.Set(gl, &renderable.context.ProjectionMatrix)

		textureUnit := int32(0)
		gl.ActiveTexture(opengl.TEXTURE0 + uint32(textureUnit))
		gl.BindTexture(opengl.TEXTURE_2D, paletteTexture.Handle())
		gl.Uniform1i(renderable.paletteUniform, textureUnit)

		textureUnit = 1
		gl.ActiveTexture(opengl.TEXTURE0 + uint32(textureUnit))
		gl.Uniform1i(renderable.bitmapUniform, textureUnit)
		for _, icon := range icons {
			x, y := float32(icon.pos.X), float32(icon.pos.Y)
			u, v := icon.texture.UV()
			width, height := renderable.limitedSize(iconSize, icon.texture)
			modelMatrix := mgl.Ident4().
				Mul4(mgl.Translate3D(x, y, 0.0)).
				Mul4(mgl.Scale3D(width, height, 1.0))

			renderable.modelMatrixUniform.Set(gl, &modelMatrix)

			uvLimit := [4]float32{u, v, 0, 0}
			renderable.uvLimitUniform.Set(gl, &uvLimit)

			gl.BindTexture(opengl.TEXTURE_2D, icon.texture.Handle())
			gl.DrawArrays(opengl.TRIANGLES, 0, 6)
		}
		gl.BindTexture(opengl.TEXTURE_2D, 0)
	})
}

func (renderable *MapIcons) limitedSize(iconSize float32, texture *graphics.BitmapTexture) (width, height float32) {
	width, height = texture.Size()
	referenceSize := float32(16.0)
	larger := width

	if larger < height {
		larger = height
	}
	if larger > referenceSize {
		ratio := referenceSize / larger
		width *= ratio
		height *= ratio
	}
	factor := iconSize / referenceSize
	width *= factor
	height *= factor

	return
}