/**
 * @file ttf转换为woff
 * @author mengke01(kekee000@gmail.com)
 *
 * woff format:
 * http://www.w3.org/TR/2012/REC-WOFF-20121213/
 *
 * references:
 * https://github.com/fontello/ttf2woff
 * https://github.com/nodeca/pako
 */



var Reader = require('./reader');
var Writer = require('./writer');
var string = require('../common/string');
var error = require('./error');
var config = require('./data/default');

/**
 * metadata 转换成XML
 *
 * @param {Object} metadata metadata
 *
 * @example
 * metadata json:
 *
 *    {
 *        "uniqueid": "",
 *        "vendor": {
 *            "name": "",
 *            "url": ""
 *        },
 *        "credit": [
 *            {
 *                "name": "",
 *                "url": "",
 *                "role": ""
 *            }
 *        ],
 *        "description": "",
 *        "license": {
 *            "id": "",
 *            "url": "",
 *            "text": ""
 *        },
 *        "copyright": "",
 *        "trademark": "",
 *        "licensee": ""
 *    }
 *
 * @return {string} xml字符串
 */
function metadata2xml(metadata) {
    var xml = ''
        + '<?xml version="1.0" encoding="UTF-8"?>'
        +   '<metadata version="1.0">';

    metadata.uniqueid = metadata.uniqueid || (config.fontId + '.' + Date.now());
    xml += '<uniqueid id="' + string.encodeHTML(metadata.uniqueid) + '" />';

    if (metadata.vendor) {
        xml += '<vendor name="' + string.encodeHTML(metadata.vendor.name) + '"'
            +     ' url="' + string.encodeHTML(metadata.vendor.url) + '" />';
    }

    if (metadata.credit) {
        xml += '<credits>';
        var credits = metadata.credit instanceof Array ? metadata.credit : [metadata.credit];

        credits.forEach(function (credit) {
            xml += '<credit name="' + string.encodeHTML(credit.name) + '"'
                +     ' url="' + string.encodeHTML(credit.url) + '"'
                +     ' role="' + string.encodeHTML(credit.role || 'Contributor') + '" />';
        });

        xml += '</credits>';
    }

    if (metadata.description) {
        xml += '<description><text xml:lang="en">'
            +     string.encodeHTML(metadata.description)
            +  '</text></description>';
    }

    if (metadata.license) {
        xml += '<license url="' + string.encodeHTML(metadata.license.url) + '"'
            +      ' id="' + string.encodeHTML(metadata.license.id) + '"><text xml:lang="en">';
        xml +=     string.encodeHTML(metadata.license.text);
        xml += '</text></license>';
    }

    if (metadata.copyright) {
        xml += '<copyright><text xml:lang="en">';
        xml +=     string.encodeHTML(metadata.copyright);
        xml += '</text></copyright>';
    }

    if (metadata.trademark) {
        xml += '<trademark><text xml:lang="en">'
            +    string.encodeHTML(metadata.trademark)
            +  '</text></trademark>';
    }

    if (metadata.licensee) {
        xml += '<licensee name="' + string.encodeHTML(metadata.licensee) + '"/>';
    }

    xml += '</metadata>';

    return xml;
}


/**
 * ttf格式转换成woff字体格式
 *
 * @param {ArrayBuffer} ttfBuffer ttf缓冲数组
 * @param {Object} options 选项
 * @param {Object} options.metadata 字体相关的信息
 * @param {Object} options.deflate 压缩相关函数
 *
 * @return {ArrayBuffer} woff格式byte流
 */
function ttf2woff(ttfBuffer, options) {

    options = options || {};

    // woff 头部结构
    var woffHeader = {
        signature: 0x774F4646, // for woff
        flavor: 0x10000, // for ttf
        length: 0,
        numTables: 0,
        reserved: 0,
        totalSfntSize: 0,
        majorVersion: 0,
        minorVersion: 0,
        metaOffset: 0,
        metaLength: 0,
        metaOrigLength: 0,
        privOffset: 0,
        privLength: 0
    };

    var ttfReader = new Reader(ttfBuffer);
    var tableEntries = [];
    var numTables = ttfReader.readUint16(4); // 读取ttf表个数
    var tableEntry;
    var deflatedData;
    var i;
    var l;

    if (numTables <= 0 || numTables > 100) {
        error.raise(10101);
    }

    // 读取ttf表索引信息
    ttfReader.seek(12);

    for (i = 0; i < numTables; ++i) {

        tableEntry = {
            tag: ttfReader.readString(ttfReader.offset, 4),
            checkSum: ttfReader.readUint32(),
            offset: ttfReader.readUint32(),
            length: ttfReader.readUint32()
        };

        var entryOffset = ttfReader.offset;

        if (tableEntry.tag === 'head') {
            // 读取font revision
            woffHeader.majorVersion = ttfReader.readUint16(tableEntry.offset + 4);
            woffHeader.minorVersion = ttfReader.readUint16(tableEntry.offset + 6);
        }

        // ttf 表数据
        var sfntData = ttfReader.readBytes(tableEntry.offset, tableEntry.length);

        // 对数据进行压缩
        if (options.deflate) {
            deflatedData = options.deflate(sfntData);

            // 这里需要判断是否压缩后数据小于原始数据
            if (deflatedData.length < sfntData.length) {
                tableEntry.data = deflatedData;
                tableEntry.deflated = true;
            }
            else {
                tableEntry.data = sfntData;
            }
        }
        else {
            tableEntry.data = sfntData;
        }

        tableEntry.compLength = tableEntry.data.length;
        tableEntries.push(tableEntry);
        ttfReader.seek(entryOffset);
    }

    if (!tableEntries.length) {
        error.raise(10204);
    }

    // 对table进行排序
    tableEntries = tableEntries.sort(function (a, b) {
        return a.tag === b.tag ? 0 : a.tag < b.tag ? -1 : 1;
    });

    // 计算offset和 woff size
    var woffSize = 44 + 20 * numTables; // header size + table entries
    var ttfSize = 12 + 16 * numTables;

    for (i = 0, l = tableEntries.length; i < l; ++i) {
        tableEntry = tableEntries[i];
        tableEntry.offset = woffSize;
         // 4字节对齐
        woffSize += tableEntry.compLength + (tableEntry.compLength % 4 ? 4 - tableEntry.compLength % 4 : 0);
        ttfSize += tableEntry.length + (tableEntry.length % 4 ? 4 - tableEntry.length % 4 : 0);
    }

    // 计算metaData
    var metadata = null;
    if (options.metadata) {
        var xml = require('./util/string').toUTF8Bytes(metadata2xml(options.metadata));

        if (options.deflate) {
            deflatedData = options.deflate(xml);
            if (deflatedData.length < xml.length) {
                metadata = deflatedData;
            }
            else {
                metadata = xml;
            }
        }
        else {
            metadata = xml;
        }

        woffHeader.metaLength = metadata.length;
        woffHeader.metaOrigLength = xml.length;
        woffHeader.metaOffset = woffSize;
        // metadata header + length
        woffSize += woffHeader.metaLength + (woffHeader.metaLength % 4 ? 4 - woffHeader.metaLength % 4 : 0);
    }

    woffHeader.numTables = tableEntries.length;
    woffHeader.length = woffSize;
    woffHeader.totalSfntSize = ttfSize;

    // 写woff数据
    var woffWriter = new Writer(new ArrayBuffer(woffSize));

    // 写woff头部
    woffWriter.writeUint32(woffHeader.signature);
    woffWriter.writeUint32(woffHeader.flavor);
    woffWriter.writeUint32(woffHeader.length);
    woffWriter.writeUint16(woffHeader.numTables);
    woffWriter.writeUint16(woffHeader.reserved);
    woffWriter.writeUint32(woffHeader.totalSfntSize);
    woffWriter.writeUint16(woffHeader.majorVersion);
    woffWriter.writeUint16(woffHeader.minorVersion);
    woffWriter.writeUint32(woffHeader.metaOffset);
    woffWriter.writeUint32(woffHeader.metaLength);
    woffWriter.writeUint32(woffHeader.metaOrigLength);
    woffWriter.writeUint32(woffHeader.privOffset);
    woffWriter.writeUint32(woffHeader.privLength);


    // 写woff表索引
    for (i = 0, l = tableEntries.length; i < l; ++i) {
        tableEntry = tableEntries[i];
        woffWriter.writeString(tableEntry.tag);
        woffWriter.writeUint32(tableEntry.offset);
        woffWriter.writeUint32(tableEntry.compLength);
        woffWriter.writeUint32(tableEntry.length);
        woffWriter.writeUint32(tableEntry.checkSum);
    }

    // 写表数据
    for (i = 0, l = tableEntries.length; i < l; ++i) {
        tableEntry = tableEntries[i];
        woffWriter.writeBytes(tableEntry.data);

        if (tableEntry.compLength % 4) {
            woffWriter.writeEmpty(4 - tableEntry.compLength % 4);
        }
    }

    // 写metadata
    if (metadata) {
        woffWriter.writeBytes(metadata);
        if (woffHeader.metaLength % 4) {
            woffWriter.writeEmpty(4 - woffHeader.metaLength % 4);
        }
    }

    return woffWriter.getBuffer();
}

module.exports = ttf2woff;
    
