// 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 (
	"fmt"
	"image"
	"image/color"

	"github.com/hajimehoshi/ebiten/internal/buffered"
	"github.com/hajimehoshi/ebiten/internal/driver"
	"github.com/hajimehoshi/ebiten/internal/graphics"
)

// Image represents a rectangle set of pixels.
// The pixel format is alpha-premultiplied RGBA.
// Image implements image.Image and draw.Image.
//
// Functions of Image never returns error as of 1.5.0-alpha, and error values are always nil.
type Image struct {
	// addr holds self to check copying.
	// See strings.Builder for similar examples.
	addr *Image

	buffered *buffered.Image

	bounds   image.Rectangle
	original *Image

	filter Filter
}

func (i *Image) copyCheck() {
	if i.addr != i {
		panic("ebiten: illegal use of non-zero Image copied by value")
	}
}

// Size returns the size of the image.
func (i *Image) Size() (width, height int) {
	s := i.Bounds().Size()
	return s.X, s.Y
}

func (i *Image) isDisposed() bool {
	return i.buffered == nil
}

func (i *Image) isSubImage() bool {
	return i.original != nil
}

// Clear resets the pixels of the image into 0.
//
// When the image is disposed, Clear does nothing.
//
// Clear always returns nil as of 1.5.0-alpha.
func (i *Image) Clear() error {
	i.Fill(color.Transparent)
	return nil
}

// Fill fills the image with a solid color.
//
// When the image is disposed, Fill does nothing.
//
// Fill always returns nil as of 1.5.0-alpha.
func (i *Image) Fill(clr color.Color) error {
	i.copyCheck()

	if i.isDisposed() {
		return nil
	}

	// TODO: Implement this.
	if i.isSubImage() {
		panic("ebiten: render to a subimage is not implemented (Fill)")
	}

	i.buffered.Fill(color.RGBAModel.Convert(clr).(color.RGBA))
	return nil
}

// DrawImage draws the given image on the image i.
//
// DrawImage accepts the options. For details, see the document of
// DrawImageOptions.
//
// For drawing, the pixels of the argument image at the time of this call is
// adopted. Even if the argument image is mutated after this call, the drawing
// result is never affected.
//
// When the image i is disposed, DrawImage does nothing.
// When the given image img is disposed, DrawImage panics.
//
// When the given image is as same as i, DrawImage panics.
//
// DrawImage works more efficiently as batches
// when the successive calls of DrawImages satisfy the below conditions:
//
//   * All render targets are same (A in A.DrawImage(B, op))
//   * Either all ColorM element values are same or all the ColorM have only
//      diagonal ('scale') elements
//     * If only (*ColorM).Scale is applied to a ColorM, the ColorM has only
//       diagonal elements. The other ColorM functions might modify the other
//       elements.
//   * All CompositeMode values are same
//   * All Filter values are same
//
// Even when all the above conditions are satisfied, multiple draw commands can
// be used in really rare cases. Ebiten images usually share an internal
// automatic texture atlas, but when you consume the atlas, or you create a huge
// image, those images cannot be on the same texture atlas. In this case, draw
// commands are separated. The texture atlas size is 4096x4096 so far. Another
// case is when you use an offscreen as a render source. An offscreen doesn't
// share the texture atlas with high probability.
//
// For more performance tips, see https://ebiten.org/documents/performancetips.html
//
// DrawImage always returns nil as of 1.5.0-alpha.
func (i *Image) DrawImage(img *Image, options *DrawImageOptions) error {
	i.copyCheck()

	if img.isDisposed() {
		panic("ebiten: the given image to DrawImage must not be disposed")
	}
	if i.isDisposed() {
		return nil
	}

	// TODO: Implement this.
	if i.isSubImage() {
		panic("ebiten: render to a subimage is not implemented (drawImage)")
	}

	// Calculate vertices before locking because the user can do anything in
	// options.ImageParts interface without deadlock (e.g. Call Image functions).
	if options == nil {
		options = &DrawImageOptions{}
	}

	parts := options.ImageParts
	// Parts is deprecated. This implementations is for backward compatibility.
	if parts == nil && options.Parts != nil {
		parts = imageParts(options.Parts)
	}

	// ImageParts is deprecated. This implementations is for backward compatibility.
	if parts != nil {
		l := parts.Len()
		for idx := 0; idx < l; idx++ {
			sx0, sy0, sx1, sy1 := parts.Src(idx)
			dx0, dy0, dx1, dy1 := parts.Dst(idx)
			op := &DrawImageOptions{
				ColorM:        options.ColorM,
				CompositeMode: options.CompositeMode,
				Filter:        options.Filter,
			}
			op.GeoM.Scale(
				float64(dx1-dx0)/float64(sx1-sx0),
				float64(dy1-dy0)/float64(sy1-sy0))
			op.GeoM.Translate(float64(dx0), float64(dy0))
			op.GeoM.Concat(options.GeoM)
			i.DrawImage(img.SubImage(image.Rect(sx0, sy0, sx1, sy1)).(*Image), op)
		}
		return nil
	}

	bounds := img.Bounds()

	// SourceRect is deprecated. This implementation is for backward compatibility.
	if options.SourceRect != nil {
		bounds = bounds.Intersect(*options.SourceRect)
		if bounds.Empty() {
			return nil
		}
	}

	geom := &options.GeoM
	mode := driver.CompositeMode(options.CompositeMode)

	filter := driver.FilterNearest
	if options.Filter != FilterDefault {
		filter = driver.Filter(options.Filter)
	} else if img.filter != FilterDefault {
		filter = driver.Filter(img.filter)
	}

	a, b, c, d, tx, ty := geom.elements()
	i.buffered.DrawImage(img.buffered, img.Bounds(), a, b, c, d, tx, ty, options.ColorM.impl, mode, filter)
	return nil
}

// Vertex represents a vertex passed to DrawTriangles.
//
// Note that this API is experimental.
type Vertex struct {
	// DstX and DstY represents a point on a destination image.
	DstX float32
	DstY float32

	// SrcX and SrcY represents a point on a source image.
	// Be careful that SrcX/SrcY coordinates are on the image's bounds.
	// This means that a left-upper point of a sub-image might not be (0, 0).
	SrcX float32
	SrcY float32

	// ColorR/ColorG/ColorB/ColorA represents color scaling values.
	// 1 means the original source image color is used.
	// 0 means a transparent color is used.
	ColorR float32
	ColorG float32
	ColorB float32
	ColorA float32
}

// Address represents a sampler address mode.
type Address int

const (
	// AddressClampToZero means that out-of-range texture coordinates return 0 (transparent).
	AddressClampToZero Address = Address(driver.AddressClampToZero)

	// AddressRepeat means that texture coordinates wrap to the other side of the texture.
	AddressRepeat Address = Address(driver.AddressRepeat)
)

// DrawTrianglesOptions represents options to render triangles on an image.
//
// Note that this API is experimental.
type DrawTrianglesOptions struct {
	// ColorM is a color matrix to draw.
	// The default (zero) value is identity, which doesn't change any color.
	// ColorM is applied before vertex color scale is applied.
	ColorM ColorM

	// CompositeMode is a composite mode to draw.
	// The default (zero) value is regular alpha blending.
	CompositeMode CompositeMode

	// Filter is a type of texture filter.
	// The default (zero) value is FilterDefault.
	Filter Filter

	// Address is a sampler address mode.
	// The default (zero) value is AddressClampToZero.
	Address Address
}

// MaxIndicesNum is the maximum number of indices for DrawTriangles.
const MaxIndicesNum = graphics.IndicesNum

// DrawTriangles draws a triangle with the specified vertices and their indices.
//
// If len(indices) is not multiple of 3, DrawTriangles panics.
//
// If len(indices) is more than MaxIndicesNum, DrawTriangles panics.
//
// The rule in which DrawTriangles works effectively is same as DrawImage's.
//
// When the image i is disposed, DrawTriangles does nothing.
//
// Internal mipmap is not used on DrawTriangles.
//
// Note that this API is experimental.
func (i *Image) DrawTriangles(vertices []Vertex, indices []uint16, img *Image, options *DrawTrianglesOptions) {
	i.copyCheck()

	if i.isDisposed() {
		return
	}

	if i.isSubImage() {
		panic("ebiten: render to a subimage is not implemented (DrawTriangles)")
	}

	if len(indices)%3 != 0 {
		panic("ebiten: len(indices) % 3 must be 0")
	}
	if len(indices) > MaxIndicesNum {
		panic("ebiten: len(indices) must be <= MaxIndicesNum")
	}
	// TODO: Check the maximum value of indices and len(vertices)?

	if options == nil {
		options = &DrawTrianglesOptions{}
	}

	mode := driver.CompositeMode(options.CompositeMode)

	filter := driver.FilterNearest
	if options.Filter != FilterDefault {
		filter = driver.Filter(options.Filter)
	} else if img.filter != FilterDefault {
		filter = driver.Filter(img.filter)
	}

	b := img.Bounds()
	bx0 := float32(b.Min.X)
	by0 := float32(b.Min.Y)
	bx1 := float32(b.Max.X)
	by1 := float32(b.Max.Y)

	// TODO: Should we use mipmap.verticesBackend?
	vs := make([]float32, len(vertices)*graphics.VertexFloatNum)
	for i, v := range vertices {
		vs[i*graphics.VertexFloatNum] = v.DstX
		vs[i*graphics.VertexFloatNum+1] = v.DstY
		vs[i*graphics.VertexFloatNum+2] = v.SrcX
		vs[i*graphics.VertexFloatNum+3] = v.SrcY
		vs[i*graphics.VertexFloatNum+4] = bx0
		vs[i*graphics.VertexFloatNum+5] = by0
		vs[i*graphics.VertexFloatNum+6] = bx1
		vs[i*graphics.VertexFloatNum+7] = by1
		vs[i*graphics.VertexFloatNum+8] = v.ColorR
		vs[i*graphics.VertexFloatNum+9] = v.ColorG
		vs[i*graphics.VertexFloatNum+10] = v.ColorB
		vs[i*graphics.VertexFloatNum+11] = v.ColorA
	}
	is := make([]uint16, len(indices))
	copy(is, indices)

	i.buffered.DrawTriangles(img.buffered, vs, is, options.ColorM.impl, mode, filter, driver.Address(options.Address))
}

// SubImage returns an image representing the portion of the image p visible through r. The returned value shares pixels with the original image.
//
// The returned value is always *ebiten.Image.
//
// If the image is disposed, SubImage returns nil.
//
// In the current Ebiten implementation, SubImage is available only as a rendering source.
func (i *Image) SubImage(r image.Rectangle) image.Image {
	i.copyCheck()
	if i.isDisposed() {
		return nil
	}

	img := &Image{
		buffered: i.buffered,
		filter:   i.filter,
	}

	// Keep the original image's reference not to dispose that by GC.
	if i.isSubImage() {
		img.original = i.original
	} else {
		img.original = i
	}
	img.addr = img

	r = r.Intersect(i.Bounds())
	// Need to check Empty explicitly. See the standard image package implementations.
	if r.Empty() {
		img.bounds = image.ZR
	} else {
		img.bounds = r
	}
	return img
}

// Bounds returns the bounds of the image.
func (i *Image) Bounds() image.Rectangle {
	if i.isDisposed() {
		panic("ebiten: the image is already disposed")
	}
	return i.bounds
}

// ColorModel returns the color model of the image.
func (i *Image) ColorModel() color.Model {
	return color.RGBAModel
}

// At returns the color of the image at (x, y).
//
// At loads pixels from GPU to system memory if necessary, which means that At can be slow.
//
// At always returns a transparent color if the image is disposed.
//
// Note that important logic should not rely on values returned by At, since
// the returned values can include very slight differences between some machines.
//
// At can't be called outside the main loop (ebiten.Run's updating function) starts (as of version 1.4.0-alpha).
func (i *Image) At(x, y int) color.Color {
	if i.isDisposed() {
		return color.RGBA{}
	}
	if i.isSubImage() && !image.Pt(x, y).In(i.bounds) {
		return color.RGBA{}
	}
	r, g, b, a, err := i.buffered.At(x, y)
	if err != nil {
		theUIContext.setError(err)
	}
	return color.RGBA{r, g, b, a}
}

// Set sets the color at (x, y).
//
// Set loads pixels from GPU to system memory if necessary, which means that Set can be slow.
//
// In the current implementation, successive calls of Set invokes loading pixels at most once, so this is efficient.
//
// If the image is disposed, Set does nothing.
func (i *Image) Set(x, y int, clr color.Color) {
	i.copyCheck()
	if i.isDisposed() {
		return
	}
	if !image.Pt(x, y).In(i.Bounds()) {
		return
	}
	if i.isSubImage() {
		i = i.original
	}

	r, g, b, a := clr.RGBA()
	if err := i.buffered.Set(x, y, byte(r>>8), byte(g>>8), byte(b>>8), byte(a>>8)); err != nil {
		theUIContext.setError(err)
	}
}

// Dispose disposes the image data. After disposing, most of image functions do nothing and returns meaningless values.
//
// Calling Dispose is not mandatory. GC automatically collects internal resources that no objects refer to.
// However, calling Dispose explicitly is helpful if memory usage matters.
//
// When the image is disposed, Dipose does nothing.
//
// Dipose always return nil as of 1.5.0-alpha.
func (i *Image) Dispose() error {
	i.copyCheck()

	if i.isDisposed() {
		return nil
	}
	if i.isSubImage() {
		return nil
	}
	i.buffered.MarkDisposed()
	i.buffered = nil
	return nil
}

// ReplacePixels replaces the pixels of the image with p.
//
// The given p must represent RGBA pre-multiplied alpha values. len(p) must equal to 4 * (image width) * (image height).
//
// ReplacePixels may be slow (as for implementation, this calls glTexSubImage2D).
//
// When len(p) is not appropriate, ReplacePixels panics.
//
// When the image is disposed, ReplacePixels does nothing.
//
// ReplacePixels always returns nil as of 1.5.0-alpha.
func (i *Image) ReplacePixels(p []byte) error {
	i.copyCheck()

	if i.isDisposed() {
		return nil
	}
	// TODO: Implement this.
	if i.isSubImage() {
		panic("ebiten: render to a subimage is not implemented (ReplacePixels)")
	}
	s := i.Bounds().Size()
	if l := 4 * s.X * s.Y; len(p) != l {
		panic(fmt.Sprintf("ebiten: len(p) was %d but must be %d", len(p), l))
	}

	i.buffered.ReplacePixels(p)
	return nil
}

// A DrawImageOptions represents options to render an image on an image.
type DrawImageOptions struct {
	// GeoM is a geometry matrix to draw.
	// The default (zero) value is identify, which draws the image at (0, 0).
	GeoM GeoM

	// ColorM is a color matrix to draw.
	// The default (zero) value is identity, which doesn't change any color.
	ColorM ColorM

	// CompositeMode is a composite mode to draw.
	// The default (zero) value is regular alpha blending.
	CompositeMode CompositeMode

	// Filter is a type of texture filter.
	// The default (zero) value is FilterDefault.
	//
	// Filter can also be specified at NewImage* functions, but
	// specifying filter at DrawImageOptions is recommended (as of 1.7.0-alpha).
	//
	// If both Filter specified at NewImage* and DrawImageOptions are FilterDefault,
	// FilterNearest is used.
	// If either is FilterDefault and the other is not, the latter is used.
	// Otherwise, Filter specified at DrawImageOptions is used.
	Filter Filter

	// Deprecated (as of 1.5.0-alpha): Use SubImage instead.
	ImageParts ImageParts

	// Deprecated (as of 1.1.0-alpha): Use SubImage instead.
	Parts []ImagePart

	// Deprecated (as of 1.9.0-alpha): Use SubImage instead.
	SourceRect *image.Rectangle
}

// NewImage returns an empty image.
//
// If width or height is less than 1 or more than device-dependent maximum size, NewImage panics.
//
// filter argument is just for backward compatibility.
// If you are not sure, specify FilterDefault.
//
// Error returned by NewImage is always nil as of 1.5.0-alpha.
func NewImage(width, height int, filter Filter) (*Image, error) {
	return newImage(width, height, filter, false), nil
}

func newImage(width, height int, filter Filter, volatile bool) *Image {
	i := &Image{
		buffered: buffered.NewImage(width, height, volatile),
		filter:   filter,
		bounds:   image.Rect(0, 0, width, height),
	}
	i.addr = i
	return i
}

// NewImageFromImage creates a new image with the given image (source).
//
// If source's width or height is less than 1 or more than device-dependent maximum size, NewImageFromImage panics.
//
// filter argument is just for backward compatibility.
// If you are not sure, specify FilterDefault.
//
// Error returned by NewImageFromImage is always nil as of 1.5.0-alpha.
func NewImageFromImage(source image.Image, filter Filter) (*Image, error) {
	size := source.Bounds().Size()

	width, height := size.X, size.Y

	i := &Image{
		buffered: buffered.NewImage(width, height, false),
		filter:   filter,
		bounds:   image.Rect(0, 0, width, height),
	}
	i.addr = i

	_ = i.ReplacePixels(copyImage(source))
	return i, nil
}

func newScreenFramebufferImage(width, height int) *Image {
	i := &Image{
		buffered: buffered.NewScreenFramebufferImage(width, height),
		filter:   FilterDefault,
		bounds:   image.Rect(0, 0, width, height),
	}
	i.addr = i
	return i
}

// MaxImageSize is deprecated as of 1.7.0-alpha. No replacement so far.
//
// TODO: Make this replacement (#541)
var MaxImageSize = 4096