package games.perses.shader

import org.khronos.webgl.Float32Array
import org.khronos.webgl.WebGLBuffer
import org.khronos.webgl.WebGLRenderingContext
import org.khronos.webgl.set

/**
 * User: rnentjes
 * Date: 14-5-16
 * Time: 11:57
 */

class VertextAttributeInfo(
    val locationName: String,
    val numElements: Int
) {
  var location = 0
  var offset = 0
}

class ShaderProgramMesh<T>(
    val shaderProgram: ShaderProgram<T>
) {
  val webgl = shaderProgram.webgl
  val data: Float32Array = Float32Array(20000 - (20000 % shaderProgram.drawLength))
  var currentIndex: Int = 0
  val attribBuffer: WebGLBuffer
  var counter = 0

  init {
    attribBuffer = webgl.createBuffer() ?: throw IllegalStateException("Unable to create webgl buffer!")
    webgl.bindBuffer(WebGLRenderingContext.ARRAY_BUFFER, attribBuffer)
  }

  fun queue(vararg vertices: Float) {
    for (vertice in vertices) {
      data[currentIndex++] = vertice
    }

    if (bufferFull()) {
      println("Skipped draw call, to many values!")
      currentIndex = 0
    }
  }

  fun queueArray(vertices: Array<Float>) {
    data.set(vertices, currentIndex)
    currentIndex += vertices.size

    if (bufferFull()) {
      println("Skipped draw call, to many values!")
      currentIndex = 0
    }
  }

  fun remaining() = data.length - currentIndex

  fun bufferFull() = currentIndex == data.length

  fun render(userdata: T) {
    counter++
    if (currentIndex > 0) {
      if (currentIndex % shaderProgram.verticesBlockSize != 0) {
        throw IllegalStateException("Number of vertices not a multiple of the attribute block size!")
      }

      shaderProgram.begin(attribBuffer, userdata)

      webgl.bufferData(WebGLRenderingContext.ARRAY_BUFFER, data, WebGLRenderingContext.DYNAMIC_DRAW)
      webgl.drawArrays(shaderProgram.drawType, 0, (currentIndex / shaderProgram.verticesBlockSize))
      currentIndex = 0

      shaderProgram.end()
    }
  }
}