index.js

import t from "should-type";
import format from "./format";

var hasOwnProperty = Object.prototype.hasOwnProperty;

function EqualityFail(a, b, reason, path) {
  this.a = a;
  this.b = b;
  this.reason = reason;
  this.path = path;
}

function typeToString(tp) {
  return tp.type + (tp.cls ? "(" + tp.cls + (tp.sub ? " " + tp.sub : "") + ")" : "");
}

var PLUS_0_AND_MINUS_0 = "+0 is not equal to -0";
var DIFFERENT_TYPES = "A has type %s and B has type %s";
var EQUALITY = "A is not equal to B";
var EQUALITY_PROTOTYPE = "A and B have different prototypes";
var WRAPPED_VALUE = "A wrapped value is not equal to B wrapped value";
var FUNCTION_SOURCES = "function A is not equal to B by source code value (via .toString call)";
var MISSING_KEY = "%s has no key %s";
var SET_MAP_MISSING_KEY = "Set/Map missing key %s";

var DEFAULT_OPTIONS = {
  checkProtoEql: true,
  checkSubType: true,
  plusZeroAndMinusZeroEqual: true,
  collectAllFails: false
};

function setBooleanDefault(property, obj, opts, defaults) {
  obj[property] = typeof opts[property] !== "boolean" ? defaults[property] : opts[property];
}

var METHOD_PREFIX = "_check_";

function EQ(opts, a, b, path) {
  opts = opts || {};

  setBooleanDefault("checkProtoEql", this, opts, DEFAULT_OPTIONS);
  setBooleanDefault("plusZeroAndMinusZeroEqual", this, opts, DEFAULT_OPTIONS);
  setBooleanDefault("checkSubType", this, opts, DEFAULT_OPTIONS);
  setBooleanDefault("collectAllFails", this, opts, DEFAULT_OPTIONS);

  this.a = a;
  this.b = b;

  this._meet = opts._meet || [];

  this.fails = opts.fails || [];

  this.path = path || [];
}

function ShortcutError(fail) {
  this.name = "ShortcutError";
  this.message = "fail fast";
  this.fail = fail;
}

ShortcutError.prototype = Object.create(Error.prototype);

EQ.checkStrictEquality = function(a, b) {
  this.collectFail(a !== b, EQUALITY);
};

EQ.add = function add(type, cls, sub, f) {
  var args = Array.prototype.slice.call(arguments);
  f = args.pop();
  EQ.prototype[METHOD_PREFIX + args.join("_")] = f;
};

EQ.prototype = {
  check: function() {
    try {
      this.check0();
    } catch (e) {
      if (e instanceof ShortcutError) {
        return [e.fail];
      }
      throw e;
    }
    return this.fails;
  },

  check0: function() {
    var a = this.a;
    var b = this.b;

    // equal a and b exit early
    if (a === b) {
      // check for +0 !== -0;
      return this.collectFail(a === 0 && 1 / a !== 1 / b && !this.plusZeroAndMinusZeroEqual, PLUS_0_AND_MINUS_0);
    }

    var typeA = t(a);
    var typeB = t(b);

    // if objects has different types they are not equal
    if (typeA.type !== typeB.type || typeA.cls !== typeB.cls || typeA.sub !== typeB.sub) {
      return this.collectFail(true, format(DIFFERENT_TYPES, typeToString(typeA), typeToString(typeB)));
    }

    // as types the same checks type specific things
    var name1 = typeA.type,
      name2 = typeA.type;
    if (typeA.cls) {
      name1 += "_" + typeA.cls;
      name2 += "_" + typeA.cls;
    }
    if (typeA.sub) {
      name2 += "_" + typeA.sub;
    }

    var f =
      this[METHOD_PREFIX + name2] ||
      this[METHOD_PREFIX + name1] ||
      this[METHOD_PREFIX + typeA.type] ||
      this.defaultCheck;

    f.call(this, this.a, this.b);
  },

  collectFail: function(comparison, reason, showReason) {
    if (comparison) {
      var res = new EqualityFail(this.a, this.b, reason, this.path);
      res.showReason = !!showReason;

      this.fails.push(res);

      if (!this.collectAllFails) {
        throw new ShortcutError(res);
      }
    }
  },

  checkPlainObjectsEquality: function(a, b) {
    // compare deep objects and arrays
    // stacks contain references only
    //
    var meet = this._meet;
    var m = this._meet.length;
    while (m--) {
      var st = meet[m];
      if (st[0] === a && st[1] === b) {
        return;
      }
    }

    // add `a` and `b` to the stack of traversed objects
    meet.push([a, b]);

    // TODO maybe something else like getOwnPropertyNames
    var key;
    for (key in b) {
      if (hasOwnProperty.call(b, key)) {
        if (hasOwnProperty.call(a, key)) {
          this.checkPropertyEquality(key);
        } else {
          this.collectFail(true, format(MISSING_KEY, "A", key));
        }
      }
    }

    // ensure both objects have the same number of properties
    for (key in a) {
      if (hasOwnProperty.call(a, key)) {
        this.collectFail(!hasOwnProperty.call(b, key), format(MISSING_KEY, "B", key));
      }
    }

    meet.pop();

    if (this.checkProtoEql) {
      //TODO should i check prototypes for === or use eq?
      this.collectFail(Object.getPrototypeOf(a) !== Object.getPrototypeOf(b), EQUALITY_PROTOTYPE, true);
    }
  },

  checkPropertyEquality: function(propertyName) {
    var _eq = new EQ(this, this.a[propertyName], this.b[propertyName], this.path.concat([propertyName]));
    _eq.check0();
  },

  defaultCheck: EQ.checkStrictEquality
};

EQ.add(t.NUMBER, function(a, b) {
  this.collectFail((a !== a && b === b) || (b !== b && a === a) || (a !== b && a === a && b === b), EQUALITY);
});

[t.SYMBOL, t.BOOLEAN, t.STRING].forEach(function(tp) {
  EQ.add(tp, EQ.checkStrictEquality);
});

EQ.add(t.FUNCTION, function(a, b) {
  // functions are compared by their source code
  this.collectFail(a.toString() !== b.toString(), FUNCTION_SOURCES);
  // check user properties
  this.checkPlainObjectsEquality(a, b);
});

EQ.add(t.OBJECT, t.REGEXP, function(a, b) {
  // check regexp flags
  var flags = ["source", "global", "multiline", "lastIndex", "ignoreCase", "sticky", "unicode"];
  while (flags.length) {
    this.checkPropertyEquality(flags.shift());
  }
  // check user properties
  this.checkPlainObjectsEquality(a, b);
});

EQ.add(t.OBJECT, t.DATE, function(a, b) {
  //check by timestamp only (using .valueOf)
  this.collectFail(+a !== +b, EQUALITY);
  // check user properties
  this.checkPlainObjectsEquality(a, b);
});

[t.NUMBER, t.BOOLEAN, t.STRING].forEach(function(tp) {
  EQ.add(t.OBJECT, tp, function(a, b) {
    //primitive type wrappers
    this.collectFail(a.valueOf() !== b.valueOf(), WRAPPED_VALUE);
    // check user properties
    this.checkPlainObjectsEquality(a, b);
  });
});

EQ.add(t.OBJECT, function(a, b) {
  this.checkPlainObjectsEquality(a, b);
});

[t.ARRAY, t.ARGUMENTS, t.TYPED_ARRAY].forEach(function(tp) {
  EQ.add(t.OBJECT, tp, function(a, b) {
    this.checkPropertyEquality("length");

    this.checkPlainObjectsEquality(a, b);
  });
});

EQ.add(t.OBJECT, t.ARRAY_BUFFER, function(a, b) {
  this.checkPropertyEquality("byteLength");

  this.checkPlainObjectsEquality(a, b);
});

EQ.add(t.OBJECT, t.ERROR, function(a, b) {
  this.checkPropertyEquality("name");
  this.checkPropertyEquality("message");

  this.checkPlainObjectsEquality(a, b);
});

EQ.add(t.OBJECT, t.BUFFER, function(a) {
  this.checkPropertyEquality("length");

  var l = a.length;
  while (l--) {
    this.checkPropertyEquality(l);
  }

  //we do not check for user properties because
  //node Buffer have some strange hidden properties
});

function checkMapByKeys(a, b) {
  var iteratorA = a.keys();

  for (var nextA = iteratorA.next(); !nextA.done; nextA = iteratorA.next()) {
    var key = nextA.value;
    var hasKey = b.has(key);
    this.collectFail(!hasKey, format(SET_MAP_MISSING_KEY, key));

    if (hasKey) {
      var valueB = b.get(key);
      var valueA = a.get(key);

      eq(valueA, valueB, this);
    }
  }
}

function checkSetByKeys(a, b) {
  var iteratorA = a.keys();

  for (var nextA = iteratorA.next(); !nextA.done; nextA = iteratorA.next()) {
    var key = nextA.value;
    var hasKey = b.has(key);
    this.collectFail(!hasKey, format(SET_MAP_MISSING_KEY, key));
  }
}

EQ.add(t.OBJECT, t.MAP, function(a, b) {
  this._meet.push([a, b]);

  checkMapByKeys.call(this, a, b);
  checkMapByKeys.call(this, b, a);

  this._meet.pop();

  this.checkPlainObjectsEquality(a, b);
});
EQ.add(t.OBJECT, t.SET, function(a, b) {
  this._meet.push([a, b]);

  checkSetByKeys.call(this, a, b);
  checkSetByKeys.call(this, b, a);

  this._meet.pop();

  this.checkPlainObjectsEquality(a, b);
});

export default function eq(a, b, opts) {
  return new EQ(opts, a, b).check();
}

eq.EQ = EQ;