/*
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 (
	"github.com/go-gl/gl"
	"github.com/hajimehoshi/ebiten/internal"
	"github.com/hajimehoshi/ebiten/internal/opengl"
	"github.com/hajimehoshi/ebiten/internal/opengl/internal/shader"
	"image/color"
	"math"
)

// TODO: Rename
type RenderTarget interface {
	Texture() *Texture
	Size() (width, height int)
	Clear() error
	Fill(clr color.Color) error
	DrawTexture(texture *Texture, parts []TexturePart, geo GeometryMatrix, color ColorMatrix) error
}

type renderTarget struct {
	glRenderTarget *opengl.RenderTarget
	texture        *Texture
}

func newRenderTarget(width, height int, filter int) (*renderTarget, error) {
	glTexture, err := opengl.NewTexture(width, height, filter)
	if err != nil {
		return nil, err
	}

	glRenderTarget, err := opengl.NewRenderTargetFromTexture(glTexture)
	if err != nil {
		return nil, err
	}

	texture := &Texture{glTexture}
	renderTarget := &renderTarget{glRenderTarget, texture}
	return renderTarget, nil
}

func (r *renderTarget) Texture() *Texture {
	return r.texture
}

func (r *renderTarget) Size() (width, height int) {
	return r.glRenderTarget.Width(), r.glRenderTarget.Height()
}

func (r *renderTarget) Clear() error {
	return r.Fill(color.RGBA{0, 0, 0, 0})
}

func (r *renderTarget) Fill(clr color.Color) error {
	if err := r.glRenderTarget.SetAsViewport(); err != nil {
		return err
	}
	const max = math.MaxUint16
	cr, cg, cb, ca := clr.RGBA()
	rf := gl.GLclampf(float64(cr) / max)
	gf := gl.GLclampf(float64(cg) / max)
	bf := gl.GLclampf(float64(cb) / max)
	af := gl.GLclampf(float64(ca) / max)
	gl.ClearColor(rf, gf, bf, af)
	gl.Clear(gl.COLOR_BUFFER_BIT)
	return nil
}

func (r *renderTarget) DrawTexture(texture *Texture, parts []TexturePart, geo GeometryMatrix, color ColorMatrix) error {
	if err := r.glRenderTarget.SetAsViewport(); err != nil {
		return err
	}
	glTexture := texture.glTexture
	quads := textureQuads(parts, glTexture.Width(), glTexture.Height())
	targetNativeTexture := gl.Texture(0)
	if r.texture != nil {
		targetNativeTexture = r.texture.glTexture.Native()
	}
	w, h := r.Size()
	projectionMatrix := r.glRenderTarget.ProjectionMatrix()
	shader.DrawTexture(glTexture.Native(), targetNativeTexture, w, h, projectionMatrix, quads, &geo, &color)
	return nil
}

func u(x float64, width int) float32 {
	return float32(x) / float32(internal.AdjustSizeForTexture(width))
}

func v(y float64, height int) float32 {
	return float32(y) / float32(internal.AdjustSizeForTexture(height))
}

func textureQuads(parts []TexturePart, width, height int) []shader.TextureQuad {
	quads := make([]shader.TextureQuad, 0, len(parts))
	for _, part := range parts {
		x1 := float32(part.Dst.X)
		x2 := float32(part.Dst.X + part.Dst.Width)
		y1 := float32(part.Dst.Y)
		y2 := float32(part.Dst.Y + part.Dst.Height)
		u1 := u(part.Src.X, width)
		u2 := u(part.Src.X+part.Src.Width, width)
		v1 := v(part.Src.Y, height)
		v2 := v(part.Src.Y+part.Src.Height, height)
		quad := shader.TextureQuad{x1, x2, y1, y2, u1, u2, v1, v2}
		quads = append(quads, quad)
	}
	return quads
}

type syncer interface {
	Sync(func())
}

type syncRenderTarget struct {
	syncer syncer
	inner  RenderTarget
}

func (c *syncRenderTarget) Texture() *Texture {
	return c.inner.Texture()
}

func (c *syncRenderTarget) Size() (width, height int) {
	return c.inner.Size()
}

func (c *syncRenderTarget) Clear() (err error) {
	c.syncer.Sync(func() {
		err = c.inner.Clear()
	})
	return
}

func (c *syncRenderTarget) Fill(clr color.Color) (err error) {
	c.syncer.Sync(func() {
		err = c.inner.Fill(clr)
	})
	return
}

func (c *syncRenderTarget) DrawTexture(texture *Texture, parts []TexturePart, geo GeometryMatrix, color ColorMatrix) (err error) {
	c.syncer.Sync(func() {
		err = c.inner.DrawTexture(texture, parts, geo, color)
	})
	return
}