remainingfilenamelength/remainingFilenameLength.js

`remainingFilenameLength` is a program that calculates the maximum allowable filename length based on the maximum path length of the current operating system. You can provide a path to the program, and it will calculate the maximum filename length that yo

const os = require('os');
const path = require('path');

function remainingFilenameLength(inputPath) {
    let maxPathLength;

    // both windows and macosx have 255 filename length limit
    let maxFilenameLength = 255;

    const dirPath = path.dirname(inputPath);

    // base on os platform to set max path length limit
    if (os.platform() === 'win32') {
        // windows full path length limit is 260
        // null character is 1
        // 8.3 filename is 12
        // http://demon.tw/programming/max_path-or-max_path-1.html
        // https://docs.microsoft.com/en-us/windows/win32/fileio/naming-a-file#maximum-path-length-limitation
        maxPathLength = 260 - 1 - 12;
    }

    if (os.platform() === 'darwin') {
        // mac actual file length limit is 1023
        maxPathLength = 1023;
    }

    // calc remaining filename length
    const remainingLength = maxPathLength - dirPath.length;

    if (remainingLength < 0) {
        return 0;
    }
    
    return Math.min(remainingLength, maxFilenameLength);
}

module.exports = remainingFilenameLength;