// Framebuffer + color-attached texture pair, sized for a render pass. Created
// once per resolution; later commits cache and reuse instances across frames
// to avoid per-frame GL allocation.

package com.simiancraft.kaleidoscope.gpu

import android.opengl.GLES30

internal class Fbo(
    val width: Int,
    val height: Int,
) {
    val texture: Int
    val framebuffer: Int

    init {
        val texIds = IntArray(1)
        GLES30.glGenTextures(1, texIds, 0)
        texture = texIds[0]
        GLES30.glBindTexture(GLES30.GL_TEXTURE_2D, texture)
        GLES30.glTexImage2D(
            GLES30.GL_TEXTURE_2D,
            0,
            GLES30.GL_RGBA,
            width,
            height,
            0,
            GLES30.GL_RGBA,
            GLES30.GL_UNSIGNED_BYTE,
            null,
        )
        GLES30.glTexParameteri(GLES30.GL_TEXTURE_2D, GLES30.GL_TEXTURE_MIN_FILTER, GLES30.GL_LINEAR)
        GLES30.glTexParameteri(GLES30.GL_TEXTURE_2D, GLES30.GL_TEXTURE_MAG_FILTER, GLES30.GL_LINEAR)
        GLES30.glTexParameteri(GLES30.GL_TEXTURE_2D, GLES30.GL_TEXTURE_WRAP_S, GLES30.GL_CLAMP_TO_EDGE)
        GLES30.glTexParameteri(GLES30.GL_TEXTURE_2D, GLES30.GL_TEXTURE_WRAP_T, GLES30.GL_CLAMP_TO_EDGE)

        val fboIds = IntArray(1)
        GLES30.glGenFramebuffers(1, fboIds, 0)
        framebuffer = fboIds[0]
        GLES30.glBindFramebuffer(GLES30.GL_FRAMEBUFFER, framebuffer)
        GLES30.glFramebufferTexture2D(
            GLES30.GL_FRAMEBUFFER,
            GLES30.GL_COLOR_ATTACHMENT0,
            GLES30.GL_TEXTURE_2D,
            texture,
            0,
        )
        val status = GLES30.glCheckFramebufferStatus(GLES30.GL_FRAMEBUFFER)
        if (status != GLES30.GL_FRAMEBUFFER_COMPLETE) {
            error("Kaleidoscope: FBO incomplete: $status")
        }
        GLES30.glBindFramebuffer(GLES30.GL_FRAMEBUFFER, 0)
    }

    fun bind() {
        GLES30.glBindFramebuffer(GLES30.GL_FRAMEBUFFER, framebuffer)
        GLES30.glViewport(0, 0, width, height)
    }

    fun delete() {
        GLES30.glDeleteFramebuffers(1, intArrayOf(framebuffer), 0)
        GLES30.glDeleteTextures(1, intArrayOf(texture), 0)
    }
}