'use strict';

var hasSymbols = require('has-symbols/shams')(); var forEach = require('for-each');

module.exports = function (assign, t) {

t.test('error cases', function (st) {
        st['throws'](function () { assign(null); }, TypeError, 'target must be an object');
        st['throws'](function () { assign(undefined); }, TypeError, 'target must be an object');
        st['throws'](function () { assign(null, {}); }, TypeError, 'target must be an object');
        st['throws'](function () { assign(undefined, {}); }, TypeError, 'target must be an object');
        st.end();
});

t.test('non-object target, no sources', function (st) {
        var bool = assign(true);
        st.equal(typeof bool, 'object', 'bool is object');
        st.equal(Boolean.prototype.valueOf.call(bool), true, 'bool coerces to `true`');

        var number = assign(1);
        st.equal(typeof number, 'object', 'number is object');
        st.equal(Number.prototype.valueOf.call(number), 1, 'number coerces to `1`');

        var string = assign('1');
        st.equal(typeof string, 'object', 'number is object');
        st.equal(String.prototype.valueOf.call(string), '1', 'number coerces to `"1"`');

        st.end();
});

t.test('non-object target, with sources', function (st) {
        var signal = {};

        st.test('boolean', function (st2) {
                var bool = assign(true, { a: signal });
                st2.equal(typeof bool, 'object', 'bool is object');
                st.equal(Boolean.prototype.valueOf.call(bool), true, 'bool coerces to `true`');
                st2.equal(bool.a, signal, 'source properties copied');
                st2.end();
        });

        st.test('number', function (st2) {
                var number = assign(1, { a: signal });
                st2.equal(typeof number, 'object', 'number is object');
                st2.equal(Number.prototype.valueOf.call(number), 1, 'number coerces to `1`');
                st2.equal(number.a, signal, 'source properties copied');
                st2.end();
        });

        st.test('string', function (st2) {
                var string = assign('1', { a: signal });
                st2.equal(typeof string, 'object', 'number is object');
                st2.equal(String.prototype.valueOf.call(string), '1', 'number coerces to `"1"`');
                st2.equal(string.a, signal, 'source properties copied');
                st2.end();
        });

        st.end();
});

t.test('non-object sources', function (st) {
        st.deepEqual(assign({ a: 1 }, null, { b: 2 }), { a: 1, b: 2 }, 'ignores null source');
        st.deepEqual(assign({ a: 1 }, { b: 2 }, undefined), { a: 1, b: 2 }, 'ignores undefined source');
        st.end();
});

t.test('returns the modified target object', function (st) {
        var target = {};
        var returned = assign(target, { a: 1 });
        st.equal(returned, target, 'returned object is the same reference as the target object');
        st.end();
});

t.test('has the right length', function (st) {
        st.equal(assign.length, 2, 'length is 2 => 2 required arguments');
        st.end();
});

t.test('merge two objects', function (st) {
        var target = { a: 1 };
        var returned = assign(target, { b: 2 });
        st.deepEqual(returned, { a: 1, b: 2 }, 'returned object has properties from both');
        st.end();
});

t.test('works with functions', function (st) {
        var target = function () {};
        target.a = 1;
        var returned = assign(target, { b: 2 });
        st.equal(target, returned, 'returned object is target');
        st.equal(returned.a, 1);
        st.equal(returned.b, 2);
        st.end();
});

t.test('works with primitives', function (st) {
        var target = 2;
        var source = { b: 42 };
        var returned = assign(target, source);
        st.equal(Object.prototype.toString.call(returned), '[object Number]', 'returned is object form of number primitive');
        st.equal(Number(returned), target, 'returned and target have same valueOf');
        st.equal(returned.b, source.b);
        st.end();
});

t.test('merge N objects', function (st) {
        var target = { a: 1 };
        var source1 = { b: 2 };
        var source2 = { c: 3 };
        var returned = assign(target, source1, source2);
        st.deepEqual(returned, { a: 1, b: 2, c: 3 }, 'returned object has properties from all sources');
        st.end();
});

t.test('only iterates over own keys', function (st) {
        var Foo = function () {};
        Foo.prototype.bar = true;
        var foo = new Foo();
        foo.baz = true;
        var target = { a: 1 };
        var returned = assign(target, foo);
        st.equal(returned, target, 'returned object is the same reference as the target object');
        st.deepEqual(target, { a: 1, baz: true }, 'returned object has only own properties from both');
        st.end();
});

t.test('includes enumerable symbols, after keys', { skip: !hasSymbols }, function (st) {
        var visited = [];
        var obj = {};
        Object.defineProperty(obj, 'a', { enumerable: true, get: function () { visited.push('a'); return 42; } });
        var symbol = Symbol('enumerable');
        Object.defineProperty(obj, symbol, {
                enumerable: true,
                get: function () { visited.push(symbol); return Infinity; }
        });
        var nonEnumSymbol = Symbol('non-enumerable');
        Object.defineProperty(obj, nonEnumSymbol, {
                enumerable: false,
                get: function () { visited.push(nonEnumSymbol); return -Infinity; }
        });
        var target = assign({}, obj);
        st.deepEqual(visited, ['a', symbol], 'key is visited first, then symbol');
        st.equal(target.a, 42, 'target.a is 42');
        st.equal(target[symbol], Infinity, 'target[symbol] is Infinity');
        st.notEqual(target[nonEnumSymbol], -Infinity, 'target[nonEnumSymbol] is not -Infinity');
        st.end();
});

t.test('does not fail when symbols are not present', function (st) {
        var getSyms;
        if (hasSymbols) {
                getSyms = Object.getOwnPropertySymbols;
                delete Object.getOwnPropertySymbols;
        }

        var visited = [];
        var obj = {};
        Object.defineProperty(obj, 'a', { enumerable: true, get: function () { visited.push('a'); return 42; } });
        var keys = ['a'];
        if (hasSymbols) {
                var symbol = Symbol('sym');
                Object.defineProperty(obj, symbol, {
                        enumerable: true,
                        get: function () { visited.push(symbol); return Infinity; }
                });
                keys.push(symbol);
        }
        var target = assign({}, obj);
        st.deepEqual(visited, keys, 'assign visits expected keys');
        st.equal(target.a, 42, 'target.a is 42');

        if (hasSymbols) {
                st.equal(target[symbol], Infinity);

                Object.getOwnPropertySymbols = getSyms;
        }
        st.end();
});

t.test('preserves correct property enumeration order', function (st) {
        var str = 'abcdefghijklmnopqrst';
        var letters = {};
        forEach(str.split(''), function (letter) {
                letters[letter] = letter;
        });

        var n = 5;
        st.comment('run the next test ' + n + ' times');
        var object = assign({}, letters);
        var actual = '';
        for (var k in object) {
                actual += k;
        }
        for (var i = 0; i < n; ++i) {
                st.equal(actual, str, 'property enumeration order should be followed');
        }
        st.end();
});

t.test('checks enumerability and existence, in case of modification during [[Get]]', { skip: !Object.defineProperty }, function (st) {
        var targetBvalue = {};
        var targetCvalue = {};
        var target = { b: targetBvalue, c: targetCvalue };
        var source = {};
        Object.defineProperty(source, 'a', {
                enumerable: true,
                get: function () {
                        delete this.b;
                        Object.defineProperty(this, 'c', { enumerable: false });
                        return 'a';
                }
        });
        var sourceBvalue = {};
        var sourceCvalue = {};
        source.b = sourceBvalue;
        source.c = sourceCvalue;
        var result = assign(target, source);
        st.equal(result, target, 'sanity check: result is === target');
        st.equal(result.b, targetBvalue, 'target key not overwritten by deleted source key');
        st.equal(result.c, targetCvalue, 'target key not overwritten by non-enumerable source key');

        st.end();
});

};