// Copyright 2019 The Ebiten Authors
//
// 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 buffered

import (
	"fmt"
	"image"

	"github.com/hajimehoshi/ebiten/v2/internal/atlas"
	"github.com/hajimehoshi/ebiten/v2/internal/graphics"
	"github.com/hajimehoshi/ebiten/v2/internal/graphicsdriver"
	"github.com/hajimehoshi/ebiten/v2/internal/shaderir"
)

type Image struct {
	img    *atlas.Image
	width  int
	height int

	pixels []byte
}

func BeginFrame(graphicsDriver graphicsdriver.Graphics) error {
	if err := atlas.BeginFrame(graphicsDriver); err != nil {
		return err
	}
	flushDelayedCommands()
	return nil
}

func EndFrame(graphicsDriver graphicsdriver.Graphics) error {
	return atlas.EndFrame(graphicsDriver)
}

func NewImage(width, height int, imageType atlas.ImageType) *Image {
	i := &Image{
		width:  width,
		height: height,
	}
	i.initialize(imageType)
	return i
}

func (i *Image) initialize(imageType atlas.ImageType) {
	if maybeCanAddDelayedCommand() {
		if tryAddDelayedCommand(func() {
			i.initialize(imageType)
		}) {
			return
		}
	}
	i.img = atlas.NewImage(i.width, i.height, imageType)
}

func (i *Image) invalidatePixels() {
	i.pixels = nil
}

func (i *Image) MarkDisposed() {
	if maybeCanAddDelayedCommand() {
		if tryAddDelayedCommand(func() {
			i.MarkDisposed()
		}) {
			return
		}
	}
	i.invalidatePixels()
	i.img.MarkDisposed()
}

func (i *Image) ReadPixels(graphicsDriver graphicsdriver.Graphics, pixels []byte, x, y, width, height int) error {
	checkDelayedCommandsFlushed("ReadPixels")

	r := image.Rect(x, y, x+width, y+height).Intersect(image.Rect(0, 0, i.width, i.height))
	if r.Empty() {
		for i := range pixels {
			pixels[i] = 0
		}
		return nil
	}

	if i.pixels == nil {
		pix := make([]byte, 4*i.width*i.height)
		if err := i.img.ReadPixels(graphicsDriver, pix); err != nil {
			return err
		}
		i.pixels = pix
	}

	dstBaseX := r.Min.X - x
	dstBaseY := r.Min.Y - y
	srcBaseX := r.Min.X
	srcBaseY := r.Min.Y
	lineWidth := 4 * r.Dx()
	for j := 0; j < r.Dy(); j++ {
		dstX := 4 * ((dstBaseY+j)*width + dstBaseX)
		srcX := 4 * ((srcBaseY+j)*i.width + srcBaseX)
		copy(pixels[dstX:dstX+lineWidth], i.pixels[srcX:srcX+lineWidth])
	}
	return nil
}

func (i *Image) DumpScreenshot(graphicsDriver graphicsdriver.Graphics, name string, blackbg bool) (string, error) {
	checkDelayedCommandsFlushed("Dump")
	return i.img.DumpScreenshot(graphicsDriver, name, blackbg)
}

// WritePixels replaces the pixels at the specified region.
func (i *Image) WritePixels(pix []byte, x, y, width, height int) {
	if l := 4 * width * height; len(pix) != l {
		panic(fmt.Sprintf("buffered: len(pix) was %d but must be %d", len(pix), l))
	}

	if maybeCanAddDelayedCommand() {
		copied := make([]byte, len(pix))
		copy(copied, pix)
		if tryAddDelayedCommand(func() {
			i.WritePixels(copied, x, y, width, height)
		}) {
			return
		}
	}

	i.invalidatePixels()
	i.img.WritePixels(pix, x, y, width, height)
}

// DrawTriangles draws the src image with the given vertices.
//
// Copying vertices and indices is the caller's responsibility.
func (i *Image) DrawTriangles(srcs [graphics.ShaderImageCount]*Image, vertices []float32, indices []uint16, blend graphicsdriver.Blend, dstRegion, srcRegion graphicsdriver.Region, subimageOffsets [graphics.ShaderImageCount - 1][2]float32, shader *Shader, uniforms [][]uint32, evenOdd bool) {
	for _, src := range srcs {
		if i == src {
			panic("buffered: Image.DrawTriangles: source images must be different from the receiver")
		}
	}

	if maybeCanAddDelayedCommand() {
		if tryAddDelayedCommand(func() {
			// Arguments are not copied. Copying is the caller's responsibility.
			i.DrawTriangles(srcs, vertices, indices, blend, dstRegion, srcRegion, subimageOffsets, shader, uniforms, evenOdd)
		}) {
			return
		}
	}

	var imgs [graphics.ShaderImageCount]*atlas.Image
	for i, img := range srcs {
		if img == nil {
			continue
		}
		imgs[i] = img.img
	}

	i.invalidatePixels()
	i.img.DrawTriangles(imgs, vertices, indices, blend, dstRegion, srcRegion, subimageOffsets, shader.shader, uniforms, evenOdd)
}

type Shader struct {
	shader *atlas.Shader
}

func NewShader(ir *shaderir.Program) *Shader {
	s := &Shader{}
	s.initialize(ir)
	return s
}

func (s *Shader) initialize(ir *shaderir.Program) {
	if maybeCanAddDelayedCommand() {
		if tryAddDelayedCommand(func() {
			s.initialize(ir)
		}) {
			return
		}
	}
	s.shader = atlas.NewShader(ir)
}

func (s *Shader) MarkDisposed() {
	if maybeCanAddDelayedCommand() {
		if tryAddDelayedCommand(func() {
			s.MarkDisposed()
		}) {
			return
		}
	}
	s.shader.MarkDisposed()
	s.shader = nil
}

var (
	NearestFilterShader = &Shader{shader: atlas.NearestFilterShader}
	LinearFilterShader  = &Shader{shader: atlas.LinearFilterShader}
)