var pool = require('./util/pool')

var GL_SUBPIXEL_BITS = 0x0D50
var GL_RED_BITS = 0x0D52
var GL_GREEN_BITS = 0x0D53
var GL_BLUE_BITS = 0x0D54
var GL_ALPHA_BITS = 0x0D55
var GL_DEPTH_BITS = 0x0D56
var GL_STENCIL_BITS = 0x0D57

var GL_ALIASED_POINT_SIZE_RANGE = 0x846D
var GL_ALIASED_LINE_WIDTH_RANGE = 0x846E

var GL_MAX_TEXTURE_SIZE = 0x0D33
var GL_MAX_VIEWPORT_DIMS = 0x0D3A
var GL_MAX_VERTEX_ATTRIBS = 0x8869
var GL_MAX_VERTEX_UNIFORM_VECTORS = 0x8DFB
var GL_MAX_VARYING_VECTORS = 0x8DFC
var GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS = 0x8B4D
var GL_MAX_VERTEX_TEXTURE_IMAGE_UNITS = 0x8B4C
var GL_MAX_TEXTURE_IMAGE_UNITS = 0x8872
var GL_MAX_FRAGMENT_UNIFORM_VECTORS = 0x8DFD
var GL_MAX_CUBE_MAP_TEXTURE_SIZE = 0x851C
var GL_MAX_RENDERBUFFER_SIZE = 0x84E8

var GL_VENDOR = 0x1F00
var GL_RENDERER = 0x1F01
var GL_VERSION = 0x1F02
var GL_SHADING_LANGUAGE_VERSION = 0x8B8C

var GL_MAX_TEXTURE_MAX_ANISOTROPY_EXT = 0x84FF

var GL_MAX_COLOR_ATTACHMENTS_WEBGL = 0x8CDF
var GL_MAX_DRAW_BUFFERS_WEBGL = 0x8824

var GL_TEXTURE_2D = 0x0DE1
var GL_TEXTURE_CUBE_MAP = 0x8513
var GL_TEXTURE_CUBE_MAP_POSITIVE_X = 0x8515
var GL_TEXTURE0 = 0x84C0
var GL_RGBA = 0x1908
var GL_FLOAT = 0x1406
var GL_UNSIGNED_BYTE = 0x1401
var GL_FRAMEBUFFER = 0x8D40
var GL_FRAMEBUFFER_COMPLETE = 0x8CD5
var GL_COLOR_ATTACHMENT0 = 0x8CE0
var GL_COLOR_BUFFER_BIT = 0x4000

module.exports = function (gl, extensions) {
  var maxAnisotropic = 1
  if (extensions.ext_texture_filter_anisotropic) {
    maxAnisotropic = gl.getParameter(GL_MAX_TEXTURE_MAX_ANISOTROPY_EXT)
  }

  var maxDrawbuffers = 1
  var maxColorAttachments = 1
  if (extensions.webgl_draw_buffers) {
    maxDrawbuffers = gl.getParameter(GL_MAX_DRAW_BUFFERS_WEBGL)
    maxColorAttachments = gl.getParameter(GL_MAX_COLOR_ATTACHMENTS_WEBGL)
  }

  // detect if reading float textures is available (Safari doesn't support)
  var readFloat = !!extensions.oes_texture_float
  if (readFloat) {
    var readFloatTexture = gl.createTexture()
    gl.bindTexture(GL_TEXTURE_2D, readFloatTexture)
    gl.texImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 1, 1, 0, GL_RGBA, GL_FLOAT, null)

    var fbo = gl.createFramebuffer()
    gl.bindFramebuffer(GL_FRAMEBUFFER, fbo)
    gl.framebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, readFloatTexture, 0)
    gl.bindTexture(GL_TEXTURE_2D, null)

    if (gl.checkFramebufferStatus(GL_FRAMEBUFFER) !== GL_FRAMEBUFFER_COMPLETE) readFloat = false

    else {
      gl.viewport(0, 0, 1, 1)
      gl.clearColor(1.0, 0.0, 0.0, 1.0)
      gl.clear(GL_COLOR_BUFFER_BIT)
      var pixels = pool.allocType(GL_FLOAT, 4)
      gl.readPixels(0, 0, 1, 1, GL_RGBA, GL_FLOAT, pixels)

      if (gl.getError()) readFloat = false
      else {
        gl.deleteFramebuffer(fbo)
        gl.deleteTexture(readFloatTexture)

        readFloat = pixels[0] === 1.0
      }

      pool.freeType(pixels)
    }
  }

  // detect non power of two cube textures support (IE doesn't support)
  var isIE = typeof navigator !== 'undefined' && (/MSIE/.test(navigator.userAgent) || /Trident\//.test(navigator.appVersion) || /Edge/.test(navigator.userAgent))

  var npotTextureCube = true

  if (!isIE) {
    var cubeTexture = gl.createTexture()
    var data = pool.allocType(GL_UNSIGNED_BYTE, 36)
    gl.activeTexture(GL_TEXTURE0)
    gl.bindTexture(GL_TEXTURE_CUBE_MAP, cubeTexture)
    gl.texImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X, 0, GL_RGBA, 3, 3, 0, GL_RGBA, GL_UNSIGNED_BYTE, data)
    pool.freeType(data)
    gl.bindTexture(GL_TEXTURE_CUBE_MAP, null)
    gl.deleteTexture(cubeTexture)
    npotTextureCube = !gl.getError()
  }

  return {
    // drawing buffer bit depth
    colorBits: [
      gl.getParameter(GL_RED_BITS),
      gl.getParameter(GL_GREEN_BITS),
      gl.getParameter(GL_BLUE_BITS),
      gl.getParameter(GL_ALPHA_BITS)
    ],
    depthBits: gl.getParameter(GL_DEPTH_BITS),
    stencilBits: gl.getParameter(GL_STENCIL_BITS),
    subpixelBits: gl.getParameter(GL_SUBPIXEL_BITS),

    // supported extensions
    extensions: Object.keys(extensions).filter(function (ext) {
      return !!extensions[ext]
    }),

    // max aniso samples
    maxAnisotropic: maxAnisotropic,

    // max draw buffers
    maxDrawbuffers: maxDrawbuffers,
    maxColorAttachments: maxColorAttachments,

    // point and line size ranges
    pointSizeDims: gl.getParameter(GL_ALIASED_POINT_SIZE_RANGE),
    lineWidthDims: gl.getParameter(GL_ALIASED_LINE_WIDTH_RANGE),
    maxViewportDims: gl.getParameter(GL_MAX_VIEWPORT_DIMS),
    maxCombinedTextureUnits: gl.getParameter(GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS),
    maxCubeMapSize: gl.getParameter(GL_MAX_CUBE_MAP_TEXTURE_SIZE),
    maxRenderbufferSize: gl.getParameter(GL_MAX_RENDERBUFFER_SIZE),
    maxTextureUnits: gl.getParameter(GL_MAX_TEXTURE_IMAGE_UNITS),
    maxTextureSize: gl.getParameter(GL_MAX_TEXTURE_SIZE),
    maxAttributes: gl.getParameter(GL_MAX_VERTEX_ATTRIBS),
    maxVertexUniforms: gl.getParameter(GL_MAX_VERTEX_UNIFORM_VECTORS),
    maxVertexTextureUnits: gl.getParameter(GL_MAX_VERTEX_TEXTURE_IMAGE_UNITS),
    maxVaryingVectors: gl.getParameter(GL_MAX_VARYING_VECTORS),
    maxFragmentUniforms: gl.getParameter(GL_MAX_FRAGMENT_UNIFORM_VECTORS),

    // vendor info
    glsl: gl.getParameter(GL_SHADING_LANGUAGE_VERSION),
    renderer: gl.getParameter(GL_RENDERER),
    vendor: gl.getParameter(GL_VENDOR),
    version: gl.getParameter(GL_VERSION),

    // quirks
    readFloat: readFloat,
    npotTextureCube: npotTextureCube
  }
}