//Copyright (c) 2009 The Chromium Authors. All rights reserved.
//Use of this source code is governed by a BSD-style license that can be
//found in the LICENSE file.

// Various functions for helping debug WebGL apps.

WebGLDebugUtils = function() {

/**
 * Wrapped logging function.
 * @param {string} msg Message to log.
 */
var log = function(msg) {
  if (window.console && window.console.log) {
    window.console.log(msg);
  }
};

/**
 * Which arguements are enums.
 * @type {!Object.<number, string>}
 */
var glValidEnumContexts = {

  // Generic setters and getters

  'enable': { 0:true },
  'disable': { 0:true },
  'getParameter': { 0:true },

  // Rendering

  'drawArrays': { 0:true },
  'drawElements': { 0:true, 2:true },

  // Shaders

  'createShader': { 0:true },
  'getShaderParameter': { 1:true },
  'getProgramParameter': { 1:true },

  // Vertex attributes

  'getVertexAttrib': { 1:true },
  'vertexAttribPointer': { 2:true },

  // Textures

  'bindTexture': { 0:true },
  'activeTexture': { 0:true },
  'getTexParameter': { 0:true, 1:true },
  'texParameterf': { 0:true, 1:true },
  'texParameteri': { 0:true, 1:true, 2:true },
  'texImage2D': { 0:true, 2:true, 6:true, 7:true },
  'texSubImage2D': { 0:true, 6:true, 7:true },
  'copyTexImage2D': { 0:true, 2:true },
  'copyTexSubImage2D': { 0:true },
  'generateMipmap': { 0:true },

  // Buffer objects

  'bindBuffer': { 0:true },
  'bufferData': { 0:true, 2:true },
  'bufferSubData': { 0:true },
  'getBufferParameter': { 0:true, 1:true },

  // Renderbuffers and framebuffers

  'pixelStorei': { 0:true, 1:true },
  'readPixels': { 4:true, 5:true },
  'bindRenderbuffer': { 0:true },
  'bindFramebuffer': { 0:true },
  'checkFramebufferStatus': { 0:true },
  'framebufferRenderbuffer': { 0:true, 1:true, 2:true },
  'framebufferTexture2D': { 0:true, 1:true, 2:true },
  'getFramebufferAttachmentParameter': { 0:true, 1:true, 2:true },
  'getRenderbufferParameter': { 0:true, 1:true },
  'renderbufferStorage': { 0:true, 1:true },

  // Frame buffer operations (clear, blend, depth test, stencil)

  'clear': { 0:true },
  'depthFunc': { 0:true },
  'blendFunc': { 0:true, 1:true },
  'blendFuncSeparate': { 0:true, 1:true, 2:true, 3:true },
  'blendEquation': { 0:true },
  'blendEquationSeparate': { 0:true, 1:true },
  'stencilFunc': { 0:true },
  'stencilFuncSeparate': { 0:true, 1:true },
  'stencilMaskSeparate': { 0:true },
  'stencilOp': { 0:true, 1:true, 2:true },
  'stencilOpSeparate': { 0:true, 1:true, 2:true, 3:true },

  // Culling

  'cullFace': { 0:true },
  'frontFace': { 0:true },
};

/**
 * Map of numbers to names.
 * @type {Object}
 */
var glEnums = null;

/**
 * Initializes this module. Safe to call more than once.
 * @param {!WebGLRenderingContext} ctx A WebGL context. If
 *    you have more than one context it doesn't matter which one
 *    you pass in, it is only used to pull out constants.
 */
function init(ctx) {
  if (glEnums == null) {
    glEnums = { };
    for (var propertyName in ctx) {
      if (typeof ctx[propertyName] == 'number') {
        glEnums[ctx[propertyName]] = propertyName;
      }
    }
  }
}

/**
 * Checks the utils have been initialized.
 */
function checkInit() {
  if (glEnums == null) {
    throw 'WebGLDebugUtils.init(ctx) not called';
  }
}

/**
 * Returns true or false if value matches any WebGL enum
 * @param {*} value Value to check if it might be an enum.
 * @return {boolean} True if value matches one of the WebGL defined enums
 */
function mightBeEnum(value) {
  checkInit();
  return (glEnums[value] !== undefined);
}

/**
 * Gets an string version of an WebGL enum.
 *
 * Example:
 *   var str = WebGLDebugUtil.glEnumToString(ctx.getError());
 *
 * @param {number} value Value to return an enum for
 * @return {string} The string version of the enum.
 */
function glEnumToString(value) {
  checkInit();
  var name = glEnums[value];
  return (name !== undefined) ? name :
      ("*UNKNOWN WebGL ENUM (0x" + value.toString(16) + ")");
}

/**
 * Returns the string version of a WebGL argument.
 * Attempts to convert enum arguments to strings.
 * @param {string} functionName the name of the WebGL function.
 * @param {number} argumentIndx the index of the argument.
 * @param {*} value The value of the argument.
 * @return {string} The value as a string.
 */ 
function glFunctionArgToString(functionName, argumentIndex, value) {
  var funcInfo = glValidEnumContexts[functionName];
  if (funcInfo !== undefined) {
    if (funcInfo[argumentIndex]) {
      return glEnumToString(value);
    }
  }
  return value.toString();
}

/**
 * Given a WebGL context returns a wrapped context that calls
 * gl.getError after every command and calls a function if the
 * result is not gl.NO_ERROR.
 *
 * @param {!WebGLRenderingContext} ctx The webgl context to
 *        wrap.
 * @param {!function(err, funcName, args): void} opt_onErrorFunc
 *        The function to call when gl.getError returns an
 *        error. If not specified the default function calls
 *        console.log with a message.
 */
function makeDebugContext(ctx, opt_onErrorFunc) {
  init(ctx);
  opt_onErrorFunc = opt_onErrorFunc || function(err, functionName, args) {
        // apparently we can't do args.join(",");
        var argStr = "";
        for (var ii = 0; ii < args.length; ++ii) {
          argStr += ((ii == 0) ? '' : ', ') + 
              glFunctionArgToString(functionName, ii, args[ii]);
        }
        log("WebGL error "+ glEnumToString(err) + " in "+ functionName +
            "(" + argStr + ")");
      };

  // Holds booleans for each GL error so after we get the error ourselves
  // we can still return it to the client app.
  var glErrorShadow = { };

  // Makes a function that calls a WebGL function and then calls getError.
  function makeErrorWrapper(ctx, functionName) {
    return function() {
      var result = ctx[functionName].apply(ctx, arguments);
      var err = ctx.getError();
      if (err != 0) {
        glErrorShadow[err] = true;
        opt_onErrorFunc(err, functionName, arguments);
      }
      return result;
    };
  }

  // Make a an object that has a copy of every property of the WebGL context
  // but wraps all functions.
  var wrapper = {};
  for (var propertyName in ctx) {
    if (typeof ctx[propertyName] == 'function') {
      wrapper[propertyName] = makeErrorWrapper(ctx, propertyName);
     } else {
       wrapper[propertyName] = ctx[propertyName];
     }
  }

  // Override the getError function with one that returns our saved results.
  wrapper.getError = function() {
    for (var err in glErrorShadow) {
      if (glErrorShadow[err]) {
        glErrorShadow[err] = false;
        return err;
      }
    }
    return ctx.NO_ERROR;
  };

  return wrapper;
}

return {
  /**
   * Initializes this module. Safe to call more than once.
   * @param {!WebGLRenderingContext} ctx A WebGL context. If
   *    you have more than one context it doesn't matter which one
   *    you pass in, it is only used to pull out constants.
   */
  'init': init,

  /**
   * Returns true or false if value matches any WebGL enum
   * @param {*} value Value to check if it might be an enum.
   * @return {boolean} True if value matches one of the WebGL defined enums
   */
  'mightBeEnum': mightBeEnum,

  /**
   * Gets an string version of an WebGL enum.
   *
   * Example:
   *   WebGLDebugUtil.init(ctx);
   *   var str = WebGLDebugUtil.glEnumToString(ctx.getError());
   *
   * @param {number} value Value to return an enum for
   * @return {string} The string version of the enum.
   */
  'glEnumToString': glEnumToString,

  /**
   * Converts the argument of a WebGL function to a string.
   * Attempts to convert enum arguments to strings.
   *
   * Example:
   *   WebGLDebugUtil.init(ctx);
   *   var str = WebGLDebugUtil.glFunctionArgToString('bindTexture', 0, gl.TEXTURE_2D);
   *   
   * would return 'TEXTURE_2D'
   *
   * @param {string} functionName the name of the WebGL function.
   * @param {number} argumentIndx the index of the argument.
   * @param {*} value The value of the argument.
   * @return {string} The value as a string.
   */
  'glFunctionArgToString': glFunctionArgToString,

  /**
   * Given a WebGL context returns a wrapped context that calls
   * gl.getError after every command and calls a function if the
   * result is not NO_ERROR.
   *
   * You can supply your own function if you want. For example, if you'd like
   * an exception thrown on any GL error you could do this
   *
   *    function throwOnGLError(err, funcName, args) {
   *      throw WebGLDebugUtils.glEnumToString(err) + " was caused by call to" +
   *            funcName;
   *    };
   *
   *    ctx = WebGLDebugUtils.makeDebugContext(
   *        canvas.getContext("webgl"), throwOnGLError);
   *
   * @param {!WebGLRenderingContext} ctx The webgl context to wrap.
   * @param {!function(err, funcName, args): void} opt_onErrorFunc The function
   *     to call when gl.getError returns an error. If not specified the default
   *     function calls console.log with a message.
   */
  'makeDebugContext': makeDebugContext
};

}();