module.exports = Hash;
var Traverse = require('traverse');

function Hash (hash, xs) {
    if (Array.isArray(hash) && Array.isArray(xs)) {
        var to = Math.min(hash.length, xs.length);
        var acc = {};
        for (var i = 0; i < to; i++) {
            acc[hash[i]] = xs[i];
        }
        return Hash(acc);
    }
    
    if (hash === undefined) return Hash({});
    
    var self = {
        map : function (f) {
            var acc = { __proto__ : hash.__proto__ };
            Object.keys(hash).forEach(function (key) {
                acc[key] = f.call(self, hash[key], key);
            });
            return Hash(acc);
        },
        forEach : function (f) {
            Object.keys(hash).forEach(function (key) {
                f.call(self, hash[key], key);
            });
            return self;
        },
        filter : function (f) {
            var acc = { __proto__ : hash.__proto__ };
            Object.keys(hash).forEach(function (key) {
                if (f.call(self, hash[key], key)) {
                    acc[key] = hash[key];
                }
            });
            return Hash(acc);
        },
        detect : function (f) {
            for (var key in hash) {
                if (f.call(self, hash[key], key)) {
                    return hash[key];
                }
            }
            return undefined;
        },
        reduce : function (f, acc) {
            var keys = Object.keys(hash);
            if (acc === undefined) acc = keys.shift();
            keys.forEach(function (key) {
                acc = f.call(self, acc, hash[key], key);
            });
            return acc;
        },
        some : function (f) {
            for (var key in hash) {
                if (f.call(self, hash[key], key)) return true;
            }
            return false;
        },
        update : function (obj) {
            if (arguments.length > 1) {
                self.updateAll([].slice.call(arguments));
            }
            else {
                Object.keys(obj).forEach(function (key) {
                    hash[key] = obj[key];
                });
            }
            return self;
        },
        updateAll : function (xs) {
            xs.filter(Boolean).forEach(function (x) {
                self.update(x);
            });
            return self;
        },
        merge : function (obj) {
            if (arguments.length > 1) {
                return self.copy.updateAll([].slice.call(arguments));
            }
            else {
                return self.copy.update(obj);
            }
        },
        mergeAll : function (xs) {
            return self.copy.updateAll(xs);
        },
        has : function (key) { // only operates on enumerables
            return Array.isArray(key)
                ? key.every(function (k) { return self.has(k) })
                : self.keys.indexOf(key.toString()) >= 0;
        },
        valuesAt : function (keys) {
            return Array.isArray(keys)
                ? keys.map(function (key) { return hash[key] })
                : hash[keys]
            ;
        },
        tap : function (f) {
            f.call(self, hash);
            return self;
        },
        extract : function (keys) {
            var acc = {};
            keys.forEach(function (key) {
                acc[key] = hash[key];
            });
            return Hash(acc);
        },
        exclude : function (keys) {
            return self.filter(function (_, key) {
                return keys.indexOf(key) < 0
            });
        },
        end : hash,
        items : hash
    };
    
    var props = {
        keys : function () { return Object.keys(hash) },
        values : function () {
            return Object.keys(hash).map(function (key) { return hash[key] });
        },
        compact : function () {
            return self.filter(function (x) { return x !== undefined });
        },
        clone : function () { return Hash(Hash.clone(hash)) },
        copy : function () { return Hash(Hash.copy(hash)) },
        length : function () { return Object.keys(hash).length },
        size : function () { return self.length }
    };
    
    if (Object.defineProperty) {
        // es5-shim has an Object.defineProperty but it throws for getters
        try {
            for (var key in props) {
                Object.defineProperty(self, key, { get : props[key] });
            }
        }
        catch (err) {
            for (var key in props) {
                if (key !== 'clone' && key !== 'copy' && key !== 'compact') {
                    // ^ those keys use Hash() so can't call them without
                    // a stack overflow
                    self[key] = props[key]();
                }
            }
        }
    }
    else if (self.__defineGetter__) {
        for (var key in props) {
            self.__defineGetter__(key, props[key]);
        }
    }
    else {
        // non-lazy version for browsers that suck >_<
        for (var key in props) {
            self[key] = props[key]();
        }
    }
    
    return self;
};

// deep copy
Hash.clone = function (ref) {
    return Traverse.clone(ref);
};

// shallow copy
Hash.copy = function (ref) {
    var hash = { __proto__ : ref.__proto__ };
    Object.keys(ref).forEach(function (key) {
        hash[key] = ref[key];
    });
    return hash;
};

Hash.map = function (ref, f) {
    return Hash(ref).map(f).items;
};

Hash.forEach = function (ref, f) {
    Hash(ref).forEach(f);
};

Hash.filter = function (ref, f) {
    return Hash(ref).filter(f).items;
};

Hash.detect = function (ref, f) {
    return Hash(ref).detect(f);
};

Hash.reduce = function (ref, f, acc) {
    return Hash(ref).reduce(f, acc);
};

Hash.some = function (ref, f) {
    return Hash(ref).some(f);
};

Hash.update = function (a /*, b, c, ... */) {
    var args = Array.prototype.slice.call(arguments, 1);
    var hash = Hash(a);
    return hash.update.apply(hash, args).items;
};

Hash.merge = function (a /*, b, c, ... */) {
    var args = Array.prototype.slice.call(arguments, 1);
    var hash = Hash(a);
    return hash.merge.apply(hash, args).items;
};

Hash.has = function (ref, key) {
    return Hash(ref).has(key);
};

Hash.valuesAt = function (ref, keys) {
    return Hash(ref).valuesAt(keys);
};

Hash.tap = function (ref, f) {
    return Hash(ref).tap(f).items;
};

Hash.extract = function (ref, keys) {
    return Hash(ref).extract(keys).items;
};

Hash.exclude = function (ref, keys) {
    return Hash(ref).exclude(keys).items;
};

Hash.concat = function (xs) {
    var hash = Hash({});
    xs.forEach(function (x) { hash.update(x) });
    return hash.items;
};

Hash.zip = function (xs, ys) {
    return Hash(xs, ys).items;
};

// .length is already defined for function prototypes
Hash.size = function (ref) {
    return Hash(ref).size;
};

Hash.compact = function (ref) {
    return Hash(ref).compact.items;
};