// Shader compile + link + uniform helpers. One instance per (vert, frag) pair.
// Constructed on the GL thread; not reusable across EGL contexts.

package com.simiancraft.kaleidoscope.gpu

import android.opengl.GLES30
import android.util.Log

internal class GlProgram(
    vertexSource: String,
    fragmentSource: String,
) {
    val id: Int

    init {
        val vs = compileShader(GLES30.GL_VERTEX_SHADER, vertexSource)
        val fs = compileShader(GLES30.GL_FRAGMENT_SHADER, fragmentSource)
        id = GLES30.glCreateProgram()
        GLES30.glAttachShader(id, vs)
        GLES30.glAttachShader(id, fs)
        GLES30.glLinkProgram(id)
        GLES30.glDetachShader(id, vs)
        GLES30.glDetachShader(id, fs)
        GLES30.glDeleteShader(vs)
        GLES30.glDeleteShader(fs)

        val status = IntArray(1)
        GLES30.glGetProgramiv(id, GLES30.GL_LINK_STATUS, status, 0)
        if (status[0] != GLES30.GL_TRUE) {
            val log = GLES30.glGetProgramInfoLog(id)
            GLES30.glDeleteProgram(id)
            error("Kaleidoscope: shader link failed: $log")
        }
    }

    fun use() {
        GLES30.glUseProgram(id)
    }

    fun uniformLocation(name: String): Int = GLES30.glGetUniformLocation(id, name)

    fun setInt(
        name: String,
        value: Int,
    ) {
        GLES30.glUniform1i(uniformLocation(name), value)
    }

    fun setFloat(
        name: String,
        value: Float,
    ) {
        GLES30.glUniform1f(uniformLocation(name), value)
    }

    fun setVec2(
        name: String,
        x: Float,
        y: Float,
    ) {
        GLES30.glUniform2f(uniformLocation(name), x, y)
    }

    /** Upload a column-major 2x2 (4 floats) to a mat2 uniform. */
    fun setMat2(
        name: String,
        columnMajor: FloatArray,
    ) {
        GLES30.glUniformMatrix2fv(uniformLocation(name), 1, false, columnMajor, 0)
    }

    fun delete() {
        GLES30.glDeleteProgram(id)
    }

    companion object {
        private const val TAG = "Kaleidoscope.GlProgram"

        private fun compileShader(
            type: Int,
            source: String,
        ): Int {
            val handle = GLES30.glCreateShader(type)
            GLES30.glShaderSource(handle, source)
            GLES30.glCompileShader(handle)
            val status = IntArray(1)
            GLES30.glGetShaderiv(handle, GLES30.GL_COMPILE_STATUS, status, 0)
            if (status[0] != GLES30.GL_TRUE) {
                val log = GLES30.glGetShaderInfoLog(handle)
                GLES30.glDeleteShader(handle)
                // Surface the source so adb logcat shows which shader failed.
                Log.e(TAG, "shader source:\n$source")
                error("Kaleidoscope: shader compile failed: $log")
            }
            return handle
        }
    }
}