// eventtap.swift - CGEventTap monitor: what the macOS event system MADE of the HID reports.
// Logs keyDown/keyUp/flagsChanged with keycode and modifier flags (Shift explicitly called out).
// Requires Accessibility (and on newer macOS also Input Monitoring) for the hosting terminal app.

import AppKit
import CoreGraphics
import Foundation

let mask: CGEventMask = (1 << CGEventType.keyDown.rawValue)
    | (1 << CGEventType.keyUp.rawValue)
    | (1 << CGEventType.flagsChanged.rawValue)

let callback: CGEventTapCallBack = { _, type, event, _ in
    let keycode = event.getIntegerValueField(.keyboardEventKeycode)
    let flags = event.flags
    let shift = flags.contains(.maskShift) ? "SHIFT=1" : "SHIFT=0"
    let fmt = ISO8601DateFormatter()
    fmt.formatOptions = [.withInternetDateTime, .withFractionalSeconds]
    // kCGKeyboardEventKeyboardType + source pid help attribute events to a specific keyboard
    let kbType = event.getIntegerValueField(.keyboardEventKeyboardType)
    print("\(fmt.string(from: Date())) | \(type == .keyDown ? "keyDown" : type == .keyUp ? "keyUp" : "flagsChanged") | keycode=\(keycode) | \(shift) | flags=0x\(String(flags.rawValue, radix: 16)) | kbType=\(kbType)")
    fflush(stdout)
    return Unmanaged.passUnretained(event) // listen-only; pass event through unchanged
}

guard let tap = CGEvent.tapCreate(tap: .cgSessionEventTap,
                                  place: .headInsertEventTap,
                                  options: .listenOnly,
                                  eventsOfInterest: mask,
                                  callback: callback,
                                  userInfo: nil)
else {
    FileHandle.standardError.write("""
    CGEvent.tapCreate returned nil - Accessibility permission missing.
    Grant it: System Settings > Privacy & Security > Accessibility > enable your terminal app,
    then fully quit and relaunch the terminal. (AXIsProcessTrusted()=\(AXIsProcessTrusted()))

    """.data(using: .utf8)!)
    exit(1)
}

let src = CFMachPortCreateRunLoopSource(kCFAllocatorDefault, tap, 0)
CFRunLoopAddSource(CFRunLoopGetCurrent(), src, .commonModes)
CGEvent.tapEnable(tap: tap, enable: true)
FileHandle.standardError.write("eventtap: tap active, type on any keyboard (Ctrl-C to stop)...\n".data(using: .utf8)!)
CFRunLoopRun()