Mini Kabibi Habibi

/*
 * Copyright (c) 2013 Adobe Systems Incorporated. All rights reserved.
 *  
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"), 
 * to deal in the Software without restriction, including without limitation 
 * the rights to use, copy, modify, merge, publish, distribute, sublicense, 
 * and/or sell copies of the Software, and to permit persons to whom the 
 * Software is furnished to do so, subject to the following conditions:
 *  
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *  
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 
 * DEALINGS IN THE SOFTWARE.
 * 
 */

(function () {
    "use strict";

    var fs      = require("fs"),
        resolve = require("path").resolve;

    var LOG_SIZE_LIMIT = 50 * 1024 * 1024; // 50 MB

    var REGULAR_LOG_NAMES = [
        "generator_latest.txt",
        "generator_1.txt",
        "generator_2.txt",
        "generator_3.txt",
        "generator_4.txt"
    ];

    var EXCEPTION_LOG_NAME = "generator_exceptions.txt";

    var _logDir,
        _logBytesWritten = 0,
        _logFilePaths = [];


    function handleUncaughtException(err) {
        var logFile = resolve(_logDir, EXCEPTION_LOG_NAME);

        var lines = [];
        lines.push("Uncaught exception on " + new Date() + ":");
        if (!err) {
            lines.push("Error value was " + JSON.stringify(err));
        } else if (err.stack) {
            lines.push("Error trace: " + err.stack);
        } else {
            lines.push("Error object: " + JSON.stringify(err, null, "    "));
        }
        lines.push("", "");
        lines = lines.join("\n");

        console.error(lines);

        try {
            fs.appendFileSync(logFile, lines);
        } catch (e) {
            // do nothing
        }
    }

    // Use tail -F logs/generator_latest.txt to see the latest output

    function writeToLog(chunk, encoding, colorFunction) {
        // We stopped logging in a previous call to write: return now
        if (_logBytesWritten > LOG_SIZE_LIMIT) { return; }

        var chunkLength,
            logMsg;

        if (!Buffer.isBuffer(chunk)) {
            chunk = String(chunk);
            if (colorFunction) {
                chunk = colorFunction(chunk);
            }
            chunkLength = Buffer.byteLength(chunk, encoding);
        } else {
            chunkLength = chunk.length;
        }

        // Calculate the new log file size
        _logBytesWritten += chunkLength;

        // Limit not yet reached: write to log file
        if (_logBytesWritten > LOG_SIZE_LIMIT) {
            logMsg = "The log file size limit of " + LOG_SIZE_LIMIT + " bytes was reached." +
                " No further output will be written to this file.";
        } else {
            logMsg = chunk;
        }

        _logFilePaths.forEach(function (path) {
            try {
                fs.appendFileSync(path, logMsg, { encoding: encoding });
            } catch (e) {
                // do nothing
            }
        });
    }

    /**
     * Listen for data on a readable stream, write to the log file
     *
     * @param {stream.Readable} stream
     */
    function logReadableStream(stream) {
        var encoding = "utf8";

        stream.setEncoding(encoding);

        stream.on("data", function (chunk) {
            writeToLog(chunk, encoding);
        });
    }

    /**
     * Tap a writable stream and write the data to the log file
     *
     * @param {stream.Writable} stream
     * @param {function=} colorFunction optional function to apply color to the log message
     */
    function logWriteableStream(stream, colorFunction) {
        var write = stream.write;
        
        // The third parameter, callback, will be passed implicitely using arguments
        stream.write = function (chunk, encoding) {
            // Write to STDOUT right away
            try {
                write.apply(this, arguments);
            } catch (streamWriteError) { }
            
            writeToLog(chunk, encoding, colorFunction);
        };
    }

    // Define the log directory as an array so we can easily create the individual
    // subdirectories if necessary, without requiring an external library like mkdirp
    function getLogDirectoryElements(settings) {
        var elements,
            platform = process.platform;

        if (settings.logRoot) {
            elements = [settings.logRoot, settings.module];
        } else if (platform === "darwin") {
            elements = [process.env.HOME, "Library", "Logs", settings.vendor, settings.application, settings.module];
        } else if (platform === "win32") {
            elements = [process.env.APPDATA, settings.vendor, settings.application, settings.module, "logs"];
        } else {
            elements = [process.env.HOME, settings.vendor, settings.application, settings.module, "logs"];
        }
        
        return elements;
    }

    function createDirectoryWithElements(elements) {
        var path = elements.shift();

        // Assume the first element exists
        while (elements.length) {
            path = resolve(path, elements.shift());
            if (!fs.existsSync(path)) {
                fs.mkdirSync(path);
            }
        }

        return path;
    }

    function rotateLogs() {
        var i;
        for (i = REGULAR_LOG_NAMES.length - 1; i > 0; i--) {
            try {
                fs.renameSync(
                    resolve(_logDir, REGULAR_LOG_NAMES[i - 1]),
                    resolve(_logDir, REGULAR_LOG_NAMES[i])
                );
            } catch (e) { }
        }
    }

    function setup(settings, logStream) {
        try {
            // Create the log file directory
            _logDir = createDirectoryWithElements(getLogDirectoryElements(settings));
        } catch (e) {
            // Do nothing except report the error
            console.error(e);
        }

        // The directory now exists, so we can log exceptions there
        process.on("uncaughtException", handleUncaughtException);

        rotateLogs();
        
        _logFilePaths.push(resolve(_logDir, REGULAR_LOG_NAMES[0]));

        // Always write stdout to log file
        logWriteableStream(process.stdout);
        // write STDERR in red
        logWriteableStream(process.stderr, function (string) {
            return "\x1B[1;31m" + string + "\x1B[0m";
        });

        // In verbose mode, write the generator log stream to stdout (which then goes on to the log file)
        // Otherwise, use logReadableStream to write directly to the generator log file
        if (settings.verbose) {
            logStream.pipe(process.stdout);
        } else {
            console.log("Logging Generator in directory: %s", _logDir);
            console.log("Use '-v' option to print logs to stdout");
            logReadableStream(logStream);
        }

        writeToLog("Log file created on " + new Date() + "\n\n");
    }

    exports.setup = setup;
}());