'use strict';

var has = Object.prototype.hasOwnProperty;

var hexTable = (function () {

var array = [];
for (var i = 0; i < 256; ++i) {
    array.push('%' + ((i < 16 ? '0' : '') + i.toString(16)).toUpperCase());
}

return array;

}());

var compactQueue = function compactQueue(queue) {

var obj;

while (queue.length) {
    var item = queue.pop();
    obj = item.obj[item.prop];

    if (Array.isArray(obj)) {
        var compacted = [];

        for (var j = 0; j < obj.length; ++j) {
            if (typeof obj[j] !== 'undefined') {
                compacted.push(obj[j]);
            }
        }

        item.obj[item.prop] = compacted;
    }
}

return obj;

};

var arrayToObject = function arrayToObject(source, options) {

var obj = options && options.plainObjects ? Object.create(null) : {};
for (var i = 0; i < source.length; ++i) {
    if (typeof source[i] !== 'undefined') {
        obj[i] = source[i];
    }
}

return obj;

};

var merge = function merge(target, source, options) {

if (!source) {
    return target;
}

if (typeof source !== 'object') {
    if (Array.isArray(target)) {
        target.push(source);
    } else if (typeof target === 'object') {
        if (options.plainObjects || options.allowPrototypes || !has.call(Object.prototype, source)) {
            target[source] = true;
        }
    } else {
        return [target, source];
    }

    return target;
}

if (typeof target !== 'object') {
    return [target].concat(source);
}

var mergeTarget = target;
if (Array.isArray(target) && !Array.isArray(source)) {
    mergeTarget = arrayToObject(target, options);
}

if (Array.isArray(target) && Array.isArray(source)) {
    source.forEach(function (item, i) {
        if (has.call(target, i)) {
            if (target[i] && typeof target[i] === 'object') {
                target[i] = merge(target[i], item, options);
            } else {
                target.push(item);
            }
        } else {
            target[i] = item;
        }
    });
    return target;
}

return Object.keys(source).reduce(function (acc, key) {
    var value = source[key];

    if (has.call(acc, key)) {
        acc[key] = merge(acc[key], value, options);
    } else {
        acc[key] = value;
    }
    return acc;
}, mergeTarget);

};

var assign = function assignSingleSource(target, source) {

return Object.keys(source).reduce(function (acc, key) {
    acc[key] = source[key];
    return acc;
}, target);

};

var decode = function (str) {

try {
    return decodeURIComponent(str.replace(/\+/g, ' '));
} catch (e) {
    return str;
}

};

var encode = function encode(str) {

// This code was originally written by Brian White (mscdex) for the io.js core querystring library.
// It has been adapted here for stricter adherence to RFC 3986
if (str.length === 0) {
    return str;
}

var string = typeof str === 'string' ? str : String(str);

var out = '';
for (var i = 0; i < string.length; ++i) {
    var c = string.charCodeAt(i);

    if (
        c === 0x2D // -
        || c === 0x2E // .
        || c === 0x5F // _
        || c === 0x7E // ~
        || (c >= 0x30 && c <= 0x39) // 0-9
        || (c >= 0x41 && c <= 0x5A) // a-z
        || (c >= 0x61 && c <= 0x7A) // A-Z
    ) {
        out += string.charAt(i);
        continue;
    }

    if (c < 0x80) {
        out = out + hexTable[c];
        continue;
    }

    if (c < 0x800) {
        out = out + (hexTable[0xC0 | (c >> 6)] + hexTable[0x80 | (c & 0x3F)]);
        continue;
    }

    if (c < 0xD800 || c >= 0xE000) {
        out = out + (hexTable[0xE0 | (c >> 12)] + hexTable[0x80 | ((c >> 6) & 0x3F)] + hexTable[0x80 | (c & 0x3F)]);
        continue;
    }

    i += 1;
    c = 0x10000 + (((c & 0x3FF) << 10) | (string.charCodeAt(i) & 0x3FF));
    out += hexTable[0xF0 | (c >> 18)]
        + hexTable[0x80 | ((c >> 12) & 0x3F)]
        + hexTable[0x80 | ((c >> 6) & 0x3F)]
        + hexTable[0x80 | (c & 0x3F)];
}

return out;

};

var compact = function compact(value) {

var queue = [{ obj: { o: value }, prop: 'o' }];
var refs = [];

for (var i = 0; i < queue.length; ++i) {
    var item = queue[i];
    var obj = item.obj[item.prop];

    var keys = Object.keys(obj);
    for (var j = 0; j < keys.length; ++j) {
        var key = keys[j];
        var val = obj[key];
        if (typeof val === 'object' && val !== null && refs.indexOf(val) === -1) {
            queue.push({ obj: obj, prop: key });
            refs.push(val);
        }
    }
}

return compactQueue(queue);

};

var isRegExp = function isRegExp(obj) {

return Object.prototype.toString.call(obj) === '[object RegExp]';

};

var isBuffer = function isBuffer(obj) {

if (obj === null || typeof obj === 'undefined') {
    return false;
}

return !!(obj.constructor && obj.constructor.isBuffer && obj.constructor.isBuffer(obj));

};

module.exports = {

arrayToObject: arrayToObject,
assign: assign,
compact: compact,
decode: decode,
encode: encode,
isBuffer: isBuffer,
isRegExp: isRegExp,
merge: merge

};