var fs = require('fs'),
    util = require('util');

function trim(string) {
    return string.replace(/^\s+|\s+$/g, '');
}

var PO = function () {
    this.comments = [];
    this.headers = {};
    this.items = [];
};

PO.prototype.save = function (filename, callback) {
    fs.writeFile(filename, this.toString(), callback);
};

PO.prototype.toString = function () {
    var lines = [],
        that = this;

    if (this.comments) {
        this.comments.forEach(function (comment) {
            lines.push('# ' + comment);
        });
    }

    lines.push('msgid ""');
    lines.push('msgstr ""');

    var keys = Object.keys(this.headers);
    keys.forEach(function (key) {
        lines.push(util.format('"%s: %s\\n"', key, that.headers[key]));
    });

    lines.push('');

    this.items.forEach(function (item) {
        lines.push(item.toString());
        lines.push('');
    });

    return lines.join("\n");
};

PO.load = function (filename, callback) {
    fs.readFile(filename, 'utf-8', function (err, data) {
        if (err) {
            return callback(err);
        }
        var po = PO.parse(data);
        callback(null, po);
    });
};

PO.parse = function (data) {
    //support both unix and windows newline formats.
    data = data.replace(/\r\n/g, '\n');
    var po = new PO(),
        sections = data.split(/\n\n/),
        headers = sections.shift(),
        lines = sections.join("\n").split(/\n/);

    po.headers = {
        'Project-Id-Version': '',
        'Report-Msgid-Bugs-To': '',
        'POT-Creation-Date': '',
        'PO-Revision-Date': '',
        'Last-Translator': '',
        'Language': '',
        'Language-Team': '',
        'Content-Type': '',
        'Content-Transfer-Encoding': '',
        'Plural-Forms': '',
    };

    headers.split(/\n/).forEach(function (header) {
        if (header.match(/^#/)) {
            po.comments.push(header.replace(/^#\s*/, ''));
        }
        if (header.match(/^"/)) {
            header = header.trim().replace(/^"/, '').replace(/\\n"$/, '');
            var p = header.split(/:/),
                name = p.shift().trim(),
                value = p.join(':').trim();
            po.headers[name] = value;
        }
    });

    var item = new PO.Item(),
        context = null,
        plural = 0;

    function finish() {
        if (item.msgid.length > 0) {
            po.items.push(item);
            item = new PO.Item();
        }
    }

    function extract(string) {
        string = trim(string);
        string = string.replace(/^[^"]*"|"$/g, '');
        string = string.replace(/\\"/g, '"');
        string = string.replace(/\\\\/g, '\\');
        return string;
    }

    while (lines.length > 0) {
        var line = trim(lines.shift()),
            add = false;
        if (line.match(/^#:/)) { // Reference
            finish();
            item.references.push(trim(line.replace(/^#:/, '')));
        }
        else if (line.match(/^#/)) { // Comment
            finish();
            item.comments.push(trim(line.replace(/^#/, '')));
        }
        else if (line.match(/^msgid_plural/)) { // Plural form
            item.msgid_plural = extract(line);
            context = 'msgid_plural';
        }
        else if (line.match(/^msgid/)) { // Original
            finish();
            item.msgid = extract(line);
            context = 'msgid';
        }
        else if (line.match(/^msgstr/)) { // Translation
            var m = line.match(/^msgstr\[(\d+)\]/);
            plural = m && m[1] ? parseInt(m[1]) : 0;
            item.msgstr[plural] = extract(line);
            context = 'msgstr';
        }
        else { // Probably multiline string or blank
            if (line.length > 0) {
                if (context === 'msgstr') {
                    item.msgstr[plural] += extract(line);
                }
                else if (context === 'msgid') {
                    item.msgid += extract(line);
                }
                else if (context === 'msgid_plural') {
                    item.msgid_plural += extract(line);
                }
            }
        }
    }
    finish();

    return po;
};

PO.Item = function () {
    this.msgid = '';
    this.references = [];
    this.msgid_plural = null;
    this.msgstr = [];
    this.comments = [];
};

PO.Item.prototype.toString = function () {
    var lines = [],
        that = this;

    var _process = function (keyword, text, i) {
        var lines = [],
            parts = text.split(/\n/),
            index = typeof i !== 'undefined' ? util.format('[%d]', i) : '';
        if (parts.length > 1) {
            lines.push(util.format('%s%s ""', keyword, index));
            parts.forEach(function (part) {
                lines.push(util.format('"%s"', part));
            });
        }
        else {
            lines.push(util.format('%s%s "%s"', keyword, index, text));
        }
        return lines;
    };

    if (this.references.length > 0) {
        this.references.forEach(function (ref) {
            lines.push(util.format('#: %s', ref));
        });
    }

    ['msgid', 'msgid_plural', 'msgstr'].forEach(function (keyword) {
        var text = that[keyword];
        if (text != null) {
            if (util.isArray(text) && text.length > 1) {
                text.forEach(function (t, i) {
                    lines = lines.concat(_process(keyword, t, i));
                });
            }
            else {
                text = util.isArray(text) ? text.join() : text;
                lines = lines.concat(_process(keyword, text));
            }
        }
    });

    return lines.join("\n");
};

module.exports = PO;