// 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/driver"
)

func convertOperation(op driver.Operation) operation {
	switch op {
	case driver.Zero:
		return zero
	case driver.One:
		return one
	case driver.SrcAlpha:
		return srcAlpha
	case driver.DstAlpha:
		return dstAlpha
	case driver.OneMinusSrcAlpha:
		return oneMinusSrcAlpha
	case driver.OneMinusDstAlpha:
		return oneMinusDstAlpha
	case driver.DstColor:
		return dstColor
	default:
		panic(fmt.Sprintf("opengl: invalid operation %d at convertOperation", op))
	}
}

type context struct {
	locationCache      *locationCache
	screenFramebuffer  framebufferNative // This might not be the default frame buffer '0' (e.g. iOS).
	lastFramebuffer    framebufferNative
	lastTexture        textureNative
	lastViewportWidth  int
	lastViewportHeight int
	lastCompositeMode  driver.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) 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
}

// highpPrecision represents an enough mantissa of float values in a shader.
const highpPrecision = 23

func (c *context) hasHighPrecisionFloat() bool {
	c.highpOnce.Do(func() {
		c.highp = c.getShaderPrecisionFormatPrecision() >= highpPrecision
	})
	return c.highp
}