preserves/implementations/javascript/src/values.js

"use strict";
// Preserves Values.
// Uses Immutable.js for many things; adds immutable values of its own for the rest.

if (require('./singletonmodule.js')('leastfixedpoint.com/preserves',
                                    require('../package.json').version,
                                    'values.js',
                                    module)) return;

const util = require('util');

const Immutable = require('immutable');
const { List, Map, Set, is, hash } = Immutable;

const { PreserveOn, AsPreserve } = require('./symbols.js');

function _decode(bs) {
  return Buffer.from(bs.buffer, bs.byteOffset, bs.byteLength).toString();
}

const encoder = (typeof TextEncoder === 'undefined') ? { encode: Buffer.from } : new TextEncoder();
const decoder = (typeof TextDecoder === 'undefined') ? { decode: _decode } : new TextDecoder();

function fromJS(x) {
  switch (typeof x) {
    case 'number':
      if (!Number.isInteger(x)) {
        // We require that clients be explicit about integer vs. non-integer types.
        throw new TypeError("Refusing to autoconvert non-integer number to Single or Double");
      }
      // FALL THROUGH
    case 'string':
    case 'symbol':
    case 'boolean':
      return x;
    case 'undefined':
      throw new TypeError("Cannot represent JavaScript undefined value as Preserves");
    case 'function':
      // We are relaxed about these, for now, even though Preserves can't serialize them.
      return x;
    case 'object':
      if (x === null) {
        // We are relaxed about these, for now, even though null is
        // strictly speaking not a Preserves Value.
        return x;
      }
      if (typeof x[AsPreserve] === 'function') {
        return x[AsPreserve]();
      }
      if (Array.isArray(x)) {
        return List().withMutations((l) => {
          for (let i = 0; i < x.length; i++) {
            l.push(fromJS(x[i]));
          }
        });
      }
      if (ArrayBuffer.isView(x) || x instanceof ArrayBuffer) {
        return Bytes(x);
      }
      return Immutable.fromJS(x);
  }
}

function _Float(value) {
  Object.defineProperty(this, 'value', {
    value: value,
    writable: false,
    enumerable: true
  });
}

function Float(value) {
  if (!(this instanceof Float)) return new Float(value);
  _Float.call(this, value);
}

Float.prototype.toString = function () {
  return '' + this.value;
};

Float.prototype.hashCode = function () {
  return this.value | 0; // TODO: something better?
};

Float.unwrap = function (v) {
  if (typeof v === 'number') return v;
  if (v instanceof Float) return v.value;
  {
    const e = new TypeError("Float.unwrap failed");
    e.irritant = v;
    throw e;
  }
};

function Single(value) {
  if (!(this instanceof Single)) return new Single(value);
  _Float.call(this, value);
}
Single.prototype = Float(NaN);

Single.prototype.equals = function (other) {
  return (other instanceof Single) && (other.value === this.value);
};

Single.prototype[PreserveOn] = function (encoder) {
  encoder.leadbyte(0, 0, 2);
  encoder.makeroom(4);
  encoder.view.setFloat32(encoder.index, this.value, false);
  encoder.index += 4;
};

function Double(value) {
  if (!(this instanceof Double)) return new Double(value);
  _Float.call(this, value);
}
Double.prototype = Float(NaN);

Double.prototype.equals = function (other) {
  return (other instanceof Double) && (other.value === this.value);
};

Double.prototype[PreserveOn] = function (encoder) {
  encoder.leadbyte(0, 0, 3);
  encoder.makeroom(8);
  encoder.view.setFloat64(encoder.index, this.value, false);
  encoder.index += 8;
};

function Bytes(maybeByteIterable) {
  if (!(this instanceof Bytes)) return new Bytes(maybeByteIterable);
  if (maybeByteIterable === void 0) {
    _installView.call(this, new Uint8Array());
  } else if (ArrayBuffer.isView(maybeByteIterable)) {
    _installView.call(this, new Uint8Array(maybeByteIterable.buffer,
                                           maybeByteIterable.byteOffset,
                                           maybeByteIterable.byteLength));
  } else if (maybeByteIterable instanceof ArrayBuffer) {
    _installView.call(this, new Uint8Array(maybeByteIterable.slice()));
  } else if (typeof maybeByteIterable === 'string') {
    _installView.call(this, encoder.encode(maybeByteIterable));
  } else if (typeof maybeByteIterable === 'number') {
    _installView.call(this, new Uint8Array(maybeByteIterable));
  } else if (typeof maybeByteIterable.length === 'number') {
    _installView.call(this, Uint8Array.from(maybeByteIterable));
  } else if (maybeByteIterable instanceof Bytes) {
    _installView.call(this, maybeByteIterable._view);
  } else if (typeof maybeByteIterable.size === 'number') {
    _installView.call(this, new Uint8Array(maybeByteIterable.size));
    for (let i = 0; i < this.size; i++) { this._view[i] = maybeByteIterable.get(i); }
  } else {
    const e = new TypeError("Attempt to initialize Bytes from unsupported value");
    e.irritant = maybeByteIterable;
    throw e;
  }
}

function _installView(view) {
  Object.defineProperty(this, '_view', { value: view, writable: false });
  Object.defineProperty(this, 'size', { value: view.length, writable: false, enumerable: true });
}

Bytes.from = Bytes;
Bytes.of = function (...args) { return Bytes(Uint8Array.of(...args)); };

function unhexDigit(asciiCode) {
  if (asciiCode >= 48 && asciiCode <= 57) return asciiCode - 48;
  if (asciiCode >= 97 && asciiCode <= 102) return asciiCode - 97 + 10;
  if (asciiCode >= 65 && asciiCode <= 70) return asciiCode - 65 + 10;
  throw new Error("Invalid hex digit: " + String.fromCharCode(asciiCode));
}

Bytes.fromHex = function (s) {
  if (s.length & 1) throw new Error("Cannot decode odd-length hexadecimal string");
  const len = s.length >> 1;
  const result = Bytes(len);
  for (let i = 0; i < len; i++) {
    result._view[i] =
      (unhexDigit(s.charCodeAt(i << 1)) << 4) | unhexDigit(s.charCodeAt((i << 1) + 1));
  }
  return result;
};

Bytes.fromIO = function (io) {
  if (typeof io === 'string') return io;
  if (io instanceof Bytes) return io;
  if (io instanceof Uint8Array) return Bytes.from(io);
  {
    const e = new TypeError("Bytes.fromIO: unsupported value");
    e.irritant = io;
    throw e;
  }
};

Bytes.toIO = function (b) {
  if (typeof b === 'string') return b;
  if (b instanceof Bytes) return b._view;
  if (b instanceof Uint8Array) return b;
  {
    const e = new TypeError("Bytes.toIO: unsupported value");
    e.irritant = b;
    throw e;
  }
};

function underlying(b) {
  return b._view || b;
}

Bytes.concat = function (bss) {
  let len = 0;
  for (let i = 0; i < bss.length; i++) { len += underlying(bss[i]).length; }

  const result = Bytes(len);
  let index = 0;
  for (let i = 0; i < bss.length; i++) {
    const bs = underlying(bss[i]);
    result._view.set(bs, index);
    index += bs.length;
  }
  return result;
};

Bytes.prototype.get = function (index) {
  return this._view[index];
};

Bytes.prototype.equals = function (other) {
  if (!(other instanceof Bytes)) return false;
  if (other.size !== this.size) return false;
  const va = this._view;
  const vb = other._view;
  for (let i = 0; i < va.length; i++) {
    if (va[i] !== vb[i]) return false;
  }
  return true;
};

Bytes.prototype.hashCode = function () {
  // Immutable.js uses this function for strings.
  const v = this._view;
  let hash = 0;
  for (let i = 0; i < v.length; i++) {
    hash = ((31 * hash) + v[i]) | 0;
  }
  return hash;
};

Bytes.decodeUtf8 = function (bs) {
  return decoder.decode(underlying(bs));
};

Bytes.prototype.fromUtf8 = function () {
  return decoder.decode(this._view);
};

Bytes.prototype.toString = function () {
  return '#"' + this.__asciify() + '"';
};

if (util.inspect) {
  Bytes.prototype[util.inspect.custom] = function (depth, options) {
    return this.toString();
  };
}

Bytes.prototype.__asciify = function () {
  const pieces = [];
  const v = this._view;
  for (let i = 0; i < v.length; i++) {
    const b = v[i];
    if (b === 92 || b === 34) {
      pieces.push('\\' + String.fromCharCode(b));
    } else if (b >= 32 && b <= 126) {
      pieces.push(String.fromCharCode(b));
    } else {
      pieces.push('\\x' + hexDigit(b >> 4) + hexDigit(b & 15));
    }
  }
  return pieces.join('');
};

function hexDigit(n) { return '0123456789abcdef'[n]; }

Bytes.prototype.toHex = function () {
  var nibbles = [];
  for (let i = 0; i < this.size; i++) {
    nibbles.push(hexDigit(this._view[i] >> 4));
    nibbles.push(hexDigit(this._view[i] & 15));
  }
  return nibbles.join('');
};

Bytes.prototype[PreserveOn] = function (encoder) {
  encoder.header(1, 2, this.size);
  encoder.emitbytes(this._view);
};

// Uint8Array / TypedArray methods
(function () {
  for (const k of `entries every find findIndex forEach includes indexOf join
                   keys lastIndexOf reduce reduceRight some toLocaleString values`.split(/\s+/))
  {
    Bytes.prototype[k] = function (...args) { return this._view[k](...args); };
  }

  for (const k of `filter map slice subarray`.split(/\s+/))
  {
    Bytes.prototype[k] = function (...args) { return Bytes(this._view[k](...args)); };
  }

  for (const k of `reverse sort`.split(/\s+/))
  {
    Bytes.prototype[k] = function (...args) { return Bytes(this._view.slice()[k](...args)); };
  }

  Bytes.prototype[Symbol.iterator] = function () { return this._view[Symbol.iterator](); };
})();

function Record(label, fields) {
  if (!(this instanceof Record)) {
    throw new TypeError("Class constructor Record cannot be invoked without 'new'");
  }
  Object.defineProperty(this, 'label', { value: fromJS(label), writable: false, enumerable: true });
  Object.defineProperty(this, 'fields', { value: fromJS(fields), writable: false, enumerable: true });
}

Record.prototype.equals = function (other) {
  return (other instanceof Record) &&
    is(this.label, other.label) &&
    is(this.fields, other.fields);
};

Record.prototype.hashCode = function () {
  return Immutable.List([this.label, this.fields]).hashCode();
};

Record.prototype.get = function (index, defaultValue) {
  return this.fields.get(index, defaultValue);
};

Record.prototype.set = function (index, newValue) {
  return new Record(this.label, this.fields.set(index, newValue));
};

Record.prototype[PreserveOn] = function (encoder) {
  encoder.header(2, 0, this.fields.size + 1);
  encoder.push(this.label);
  for (const field of this.fields) { encoder.push(field); }
};

Record.prototype.getConstructorInfo = function () {
  return new RecordConstructorInfo(this.label, this.fields.size);
};

Record.prototype.toString = function () {
  return this.label.toString().replace(/^Symbol\((.*)\)$/, '$1') +
    '(' + this.fields.map((f) => {
      try {
        return "" + f;
      } catch (e) {
        return (util.inspect || ((f) => '<unprintable_preserves_field_value>'))(f);
      }
    }).join(', ') + ')';
};

Record.makeConstructor = function (labelSymbolText, fieldNames) {
  return Record.makeBasicConstructor(Symbol.for(labelSymbolText), fieldNames);
};

Record.makeBasicConstructor = function (label, fieldNames) {
  const arity = fieldNames.length;
  const ctor = (...fields) => {
    if (fields.length !== arity) {
      throw new Error("Record: cannot instantiate " + (label && label.toString()) +
                      " expecting " + arity + " fields with " + fields.length + " fields");
    }
    return new Record(label, fields);
  };
  ctor.constructorInfo = new RecordConstructorInfo(label, arity);
  ctor.isClassOf = (v) => ((v instanceof Record) &&
                           is(label, v.label) &&
                           v.fields.size === arity);
  fieldNames.forEach((name, i) => {
    ctor['_'+name] = function (r) {
      if (!ctor.isClassOf(r)) {
        throw new Error("Record: attempt to retrieve field "+label.toString()+"."+name+
                        " from non-"+label.toString()+": "+(r && r.toString()));
      }
      return r.get(i);
    };
  });
  return ctor;
};

function RecordConstructorInfo(label, arity) {
  this.label = label;
  this.arity = arity;
}

RecordConstructorInfo.prototype.equals = function (other) {
  return (other instanceof RecordConstructorInfo) &&
    is(this.label, other.label) &&
    (this.arity === other.arity);
};

RecordConstructorInfo.prototype.hashCode = function () {
  return Immutable.List([this.label, this.arity]).hashCode();
};

RecordConstructorInfo.prototype.isClassOf = function (v) {
  return (v instanceof Record) &&
    is(this.label, v.label) &&
    (this.arity === v.fields.size);
};

Object.assign(module.exports, {
  fromJS,
  List, Map, Set, is, hash,
  Float, Single, Double,
  Bytes,
  Record, RecordConstructorInfo,
});