var fs = require('fs');

var utf8    = require('./encoding/utf8'),
    unicode = require('./encoding/unicode'),
    mbcs    = require('./encoding/mbcs'),
    sbcs    = require('./encoding/sbcs'),
    iso2022 = require('./encoding/iso2022');

var self = this;

var recognisers = [
    new utf8,
    new unicode.UTF_16BE,
    new unicode.UTF_16LE,
    new unicode.UTF_32BE,
    new unicode.UTF_32LE,
    new mbcs.sjis,
    new mbcs.big5,
    new mbcs.euc_jp,
    new mbcs.euc_kr,
    new mbcs.gb_18030,
    new iso2022.ISO_2022_JP,
    new iso2022.ISO_2022_KR,
    new iso2022.ISO_2022_CN,
    new sbcs.ISO_8859_1,
    new sbcs.ISO_8859_2,
    new sbcs.ISO_8859_5,
    new sbcs.ISO_8859_6,
    new sbcs.ISO_8859_7,
    new sbcs.ISO_8859_8,
    new sbcs.ISO_8859_9,
    new sbcs.windows_1251,
    new sbcs.windows_1256,
    new sbcs.KOI8_R
];

module.exports.detect = function(buffer) {

    // Tally up the byte occurence statistics.
    var fByteStats = [];
    for (var i = 0; i < 256; i++)
        fByteStats[i] = 0;

    for (var i = buffer.length - 1; i >= 0; i--)
        fByteStats[buffer[i] & 0x00ff]++;

    var fC1Bytes = false;
    for (var i = 0x80; i <= 0x9F; i += 1) {
        if (fByteStats[i] != 0) {
            fC1Bytes = true;
            break;
        }
    }

    var context = {
        fByteStats:  fByteStats,
        fC1Bytes:    fC1Bytes,
        fRawInput:   buffer,
        fRawLength:  buffer.length,
        fInputBytes: buffer,
        fInputLen:   buffer.length
    };

    var matches = recognisers.map(function(rec) {
        return rec.match(context);
    }).filter(function(match) {
        return !!match;
    });

    matches.sort(function(a, b) {
        return a.confidence - b.confidence;
    });

    return matches.length ? matches.pop().name : null;
};

module.exports.detectFile = function(filepath, fn) {
    fs.readFile(filepath, function(err, res) {
        if (err)
            return fn(err, null);
        fn(null, self.detect(res));
    });
};

module.exports.detectFileSync = function(filepath) {
    return self.detect(fs.readFileSync(filepath));
};