import Foundation

/**
 A file entry from a directory listing.
 - SeeAlso: `ls()`
*/
public struct Entry {
    /// The kind of this directory entry.
    public enum Kind {
        /// The path is a file.
        case file
        /// The path is a directory.
        case directory
    }
    /// The kind of this entry.
    public let kind: Kind
    /// The path of this entry.
    public let path: Path
}

public extension Path {    
    //MARK: Directory Listings

    /**
     Same as the `ls -a` command ∴ output is ”shallow” and unsorted.
     - Parameter includeHiddenFiles: If `true`, hidden files are included in the results. Defaults to `true`.
     - Important: `includeHiddenFiles` does not work on Linux
     */
    func ls(includeHiddenFiles: Bool = true) throws -> [Entry] {
        var opts = FileManager.DirectoryEnumerationOptions()
    #if !os(Linux)
        if !includeHiddenFiles {
            opts.insert(.skipsHiddenFiles)
        }
    #endif
        let paths = try FileManager.default.contentsOfDirectory(at: url, includingPropertiesForKeys: nil, options: opts)
        func convert(url: URL) -> Entry? {
            guard let path = Path(url.path) else { return nil }
            return Entry(kind: path.isDirectory ? .directory : .file, path: path)
        }
        return paths.compactMap(convert)
    }
}

/// Convenience functions for the array return value of `Path.ls()`
public extension Array where Element == Entry {
    /// Filters the list of entries to be a list of Paths that are directories.
    var directories: [Path] {
        return compactMap {
            $0.kind == .directory ? $0.path : nil
        }
    }

    /// Filters the list of entries to be a list of Paths that are files with the specified extension
    func files(withExtension ext: String) -> [Path] {
        return compactMap {
            $0.kind == .file && $0.path.extension == ext ? $0.path : nil
        }
    }
}