bitcoincashjs/util/EncodedData.js

require('classtool');

function ClassSpec(b) {
  var base58 = b.base58 || require('base58-native').base58Check;

  // Constructor.  Takes the following forms:
  //   new EncodedData(<base58_address_string>)
  //   new EncodedData(<binary_buffer>)
  //   new EncodedData(<data>, <encoding>)
  //   new EncodedData(<version>, <20-byte-hash>)
  function EncodedData(data, encoding) {
    this.data = data;
    if(!encoding && (typeof data == 'string')) {
      this.__proto__ = this.encodings['base58'];
    } else {
      this.__proto__ = this.encodings[encoding || 'binary'];
    }
  };

  // get or set the encoding used (transforms data)
  EncodedData.prototype.encoding = function(encoding) {
    if(encoding && (encoding != this._encoding)) {
      this.data = this.as(encoding);
      this.__proto__ = this.encodings[encoding];
    }
    return this._encoding;
  };

  // answer a new instance having the given encoding
  EncodedData.prototype.withEncoding = function(encoding) {
    return new EncodedData(this.as(encoding), encoding);
  };

  // answer the data in the given encoding
  EncodedData.prototype.as = function(encoding) {
    if(!encodings[encoding]) throw new Error('invalid encoding');
    return this.converters[encoding].call(this);
  };

  // validate that we can convert to binary
  EncodedData.prototype._validate = function() {
    this.withEncoding('binary');
  };

  // Boolean protocol for testing if valid
  EncodedData.prototype.isValid = function() {
    try {
      this.validate();
      return true;
    } catch(e) {
      return false;
    }
  };

  // subclasses can override to do more stuff
  EncodedData.prototype.validate = function() {
    this._validate();
  };

  // Boolean protocol for testing if valid
  EncodedData.prototype.isValid = function() {
    try {
      this.validate();
      return true;
    } catch(e) {
      return false;
    }
  };

  // convert to a string (in base58 form)
  EncodedData.prototype.toString = function() {
    return this.as('base58');
  };

  // utility
  EncodedData.prototype.doAsBinary = function(callback) {
    var oldEncoding = this.encoding();
    this.encoding('binary');
    callback.apply(this);
    this.encoding(oldEncoding);
  };

  // Setup support for various address encodings.  The object for
  // each encoding inherits from the EncodedData prototype.  This
  // allows any encoding to override any method...changing the encoding
  // for an instance will change the encoding it inherits from.  Note,
  // this will present some problems for anyone wanting to inherit from
  // EncodedData (we'll deal with that when needed).
  var encodings = {
    'binary': {
      converters: {
        'binary': function() {
          var answer = new Buffer(this.data.length);
          this.data.copy(answer);
          return answer;
        },
        'base58': function() {
          return base58.encode(this.data);
        },
        'hex': function() {
          return this.data.toString('hex');
        },
      },

      _validate: function() {
        //nothing to do here...we make no assumptions about the data
      },
    },

    'base58': {
      converters: {
        'binary': function() {
          return base58.decode(this.data);
        },
        'hex': function() {
          return this.withEncoding('binary').as('hex');
        },
      },
    },

    'hex': {
      converters: {
        'binary': function() {
          return new Buffer(this.data, 'hex');
        },
        'base58': function() {
          return this.withEncoding('binary').as('base58');
        },
      },
    },
  };

  for(var k in encodings) {
    if(!encodings[k].converters[k])
      encodings[k].converters[k] = function() {return this.data;};
    encodings[k]._encoding = k;
  }

  EncodedData.applyEncodingsTo = function(aClass) {
    var tmp = {};
    for(var k in encodings) {
      var enc = encodings[k];
      var obj = {}; 
      for(var j in enc) {
        obj[j] = enc[j];
      }
      obj.__proto__ = aClass.prototype;
      tmp[k] = obj;
    }
    aClass.prototype.encodings = tmp;
  };

  EncodedData.applyEncodingsTo(EncodedData);
  return EncodedData;
};
module.defineClass(ClassSpec);