/*
====================================================================================================
backport.js v0.1

Makes older versions of the JS API a bit newer:

* Implement/upgrade functions
* Implement missing constants
* Remove deprecated functions/constants

Developed by: aubergine http://forums.wz2100.net/memberlist.php?mode=viewprofile&u=4994

Home page: https://warzone.atlassian.net/wiki/display/backportjs

Released under the MIT, BSD, and GPL Licenses.

v0.1 - Initial release
====================================================================================================
*/


if (!backport) {

  // requires Util.js from https://warzone.atlassian.net/wiki/display/UtilJS
  if (!Object.prototype.uGetType) throw new Error("Unable to initialise Backport: backport.js requires util.js");

  function backport(name,value) {
    var code;
    switch (arguments.length) {
      case 2: { // backport something
        // make sure it's not already backported
        if (backport[name] || name == "backport" || name == "native" || name == "global") {
          throw new Error("Unable backport '"+name+"': Already backported '"+name+"' (or it's a reserved keyword)");
        }
        // work out what sort of backport it is
        switch (Object.uGetType(value)) {
          // add/extend function
          // https://warzone.atlassian.net/wiki/display/backportjs/Adding+missing+functions
          // https://warzone.atlassian.net/wiki/display/backportjs/Overriding+existing+functions
          case "function" : {
            // store funcs where eval can get at them
            eval("if ("+name+") backport.native = "+name+";");
            backport.backport = value;
            // backport code
            //code =  "function "+name+"(){return "+name+".backport.apply(this,arguments);}";
            code  = "var "+name+" = backport.backport;";
            code += "if (backport.native) {backport['"+name+"']=1;"+name+".native=backport.native;} else {backport['"+name+"']=-1;};"
            code += name+".backport = backport.backport;";
            // execute code in global scope with no scope or prototype chain
            eval.call(null,code);
            // clear up any function backport mess
            delete backport.native;
            delete backport.backport;
            break;
          }
          // remove deprecated function / constant
          // https://warzone.atlassian.net/wiki/display/backportjs/Removing+deprecated+API+features
          case "null"     :
          case "undefined": {
            // backport code
            code = "if ("+name+" != undefined) { const "+name+" = undefined; backport['"+name+"']=null;}";
            // execute code in global scope with no scope or prototype chain
            eval.call(null,code);
            break;
          }
          // alter a global - not currently implemented
          case "array"    :
          case "object"   : {
            throw new Error("Backport: Altering arrays/objects (for '"+name+"') not currently supported.");
          }
          // add missing constant
          // https://warzone.atlassian.net/wiki/display/backportjs/Adding+missing+constants
          case "boolean"  :
          case "string"   :
          case "number"   : {
            // backport code
            code = "if ("+name+" == undefined) { const "+name+" = "+value+"; backport['"+name+"']=-1;}";
            // execute code in global scope with no scope or prototype chain
            eval.call(null,code);
            break;
          }
          // something unexpected - throw error
          default         : {
            throw new Error("Backport: Unrecognised data type for '"+name+"': "+Object.uGetType(value));
          }
        }          
        // return backport status for name
        return backport(name);
      }
      case 1: { // is 'name' backported?
        // https://warzone.atlassian.net/wiki/display/backportjs/Check+status+of+an+API+feature
        // -1 = added, null = deprecated, false = native, undefined = not implemented, +1 = extended
        return (backport.hasOwnProperty(name)) ? backport[name] : undefined;
      }
      default: { // return a list of all JS API features
        // https://warzone.atlassian.net/wiki/display/backportjs/Listing+API+features
        return Object.keys(backport);
      }
    }
  }
  
  // let's keep a reference to the global object for easy access
  // https://warzone.atlassian.net/wiki/display/backportjs/Accessing+native+API+features
  backport.global = this;
  
  // now grab all the native JS API stuff and mark it as native (false) on backport
  Object.keys(this).forEach(function(native) {
    backport[native] = true; // false indicates that native has not yet been touched by backport
  });
  
}