// Copyright 2016 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 opengl

import (
	"fmt"
	"sync"

	"github.com/hajimehoshi/ebiten/v2/internal/graphicsdriver"
)

type blendFactor int

const (
	glDstAlpha         blendFactor = 0x0304
	glDstColor         blendFactor = 0x0306
	glOne              blendFactor = 1
	glOneMinusDstAlpha blendFactor = 0x0305
	glOneMinusSrcAlpha blendFactor = 0x0303
	glSrcAlpha         blendFactor = 0x0302
	glZero             blendFactor = 0
)

func convertBlendFactor(op graphicsdriver.BlendFactor) blendFactor {
	switch op {
	case graphicsdriver.BlendFactorZero:
		return glZero
	case graphicsdriver.BlendFactorOne:
		return glOne
	case graphicsdriver.BlendFactorSourceAlpha:
		return glSrcAlpha
	case graphicsdriver.BlendFactorDestinationAlpha:
		return glDstAlpha
	case graphicsdriver.BlendFactorOneMinusSourceAlpha:
		return glOneMinusSrcAlpha
	case graphicsdriver.BlendFactorOneMinusDestinationAlpha:
		return glOneMinusDstAlpha
	case graphicsdriver.BlendFactorDestinationColor:
		return glDstColor
	default:
		panic(fmt.Sprintf("opengl: invalid blend factor %d at convertBlendFactor", op))
	}
}

type context struct {
	locationCache      *locationCache
	screenFramebuffer  framebufferNative // This might not be the default frame buffer '0' (e.g. iOS).
	lastFramebuffer    framebufferNative
	lastTexture        textureNative
	lastRenderbuffer   renderbufferNative
	lastViewportWidth  int
	lastViewportHeight int
	lastCompositeMode  graphicsdriver.CompositeMode
	maxTextureSize     int
	maxTextureSizeOnce sync.Once
	highp              bool
	highpOnce          sync.Once

	contextImpl
}

func (c *context) bindTexture(t textureNative) {
	if c.lastTexture.equal(t) {
		return
	}
	c.bindTextureImpl(t)
	c.lastTexture = t
}

func (c *context) bindRenderbuffer(r renderbufferNative) {
	if c.lastRenderbuffer.equal(r) {
		return
	}
	c.bindRenderbufferImpl(r)
	c.lastRenderbuffer = r
}

func (c *context) bindFramebuffer(f framebufferNative) {
	if c.lastFramebuffer.equal(f) {
		return
	}
	c.bindFramebufferImpl(f)
	c.lastFramebuffer = f
}

func (c *context) setViewport(f *framebuffer) {
	c.bindFramebuffer(f.native)
	if c.lastViewportWidth != f.width || c.lastViewportHeight != f.height {
		// On some environments, viewport size must be within the framebuffer size.
		// e.g. Edge (#71), Chrome on GPD Pocket (#420), macOS Mojave (#691).
		// Use the same size of the framebuffer here.
		c.setViewportImpl(f.width, f.height)

		// glViewport must be called at least at every frame on iOS.
		// As the screen framebuffer is the last render target, next SetViewport should be
		// the first call at a frame.
		if f.native.equal(c.screenFramebuffer) {
			c.lastViewportWidth = 0
			c.lastViewportHeight = 0
		} else {
			c.lastViewportWidth = f.width
			c.lastViewportHeight = f.height
		}
	}
}

func (c *context) getScreenFramebuffer() framebufferNative {
	return c.screenFramebuffer
}

func (c *context) getMaxTextureSize() int {
	c.maxTextureSizeOnce.Do(func() {
		c.maxTextureSize = c.maxTextureSizeImpl()
	})
	return c.maxTextureSize
}