reveal.swift

#!/usr/bin/swift

import AppKit
import Foundation

let progname = URL(fileURLWithPath: CommandLine.arguments[0]).lastPathComponent

func warn(_ message: String, when: Bool = true) {
    guard when else { return }
    fputs("\(message)\n", stderr)
}

func warnx(_ message: String, when: Bool = true) {
    warn("\(progname): \(message)", when: when)
}

func usage() {
    warn("usage: \(progname) [-0] [--] [files...]")
    warn("  -0: Expect NUL ('\\0')-terminated filename strings on stdin")
    warn("  --: End of options processing; all subsequent arguments are files")
    exit(1)
}

func isInputAvailable() -> Bool {
    var pollFD = pollfd(fd: STDIN_FILENO, events: Int16(POLLIN), revents: 0)
    return poll(&pollFD, 1, 0) > 0 && (pollFD.revents & Int16(POLLIN)) != 0
}

struct InputSplitter: IteratorProtocol {
    enum Separator: UInt8 { case NUL = 0, LF = 10 }
    let separator: Separator
    var buffer = Data(capacity: Int(PATH_MAX))

    mutating func result() -> String? {
        defer { buffer.removeAll(keepingCapacity: true) }
        return buffer.isEmpty ? nil : String(data: buffer, encoding: .utf8)
    }
    mutating func next() -> String? {
        var char: UInt8 = 0
        while read(STDIN_FILENO, &char, 1) == 1 {
            if char == separator.rawValue {
                return result()
            }
            buffer.append(char)
        }
        return result()
    }
}

var nullSeparated = false
var fileArguments = false

var args = CommandLine.arguments.dropFirst()
loop: while let arg = args.first, arg.starts(with: "-") {
    args = args.dropFirst()

    switch arg {
    case "-0":
        nullSeparated = true
    case "--":
        fileArguments = true
        break loop
    default:
        warnx("invalid option: \(arg)")
        usage()
    }
}

if !(fileArguments || args.isEmpty) {
    fileArguments = true
    warnx("ignoring input on stdin due to file arguments", when: isInputAvailable())
}
warnx("ignoring -0 option due to file arguments", when: fileArguments && nullSeparated)

let urls = (fileArguments
            ? AnySequence(args)
            : AnySequence { InputSplitter(separator: nullSeparated ? .NUL : .LF) })
              .compactMap { URL(fileURLWithPath: $0).absoluteURL }

if !urls.isEmpty {
    NSWorkspace.shared.activateFileViewerSelecting(urls)
}