import CoreAudio
import Foundation

/// Lists the PIDs of processes currently using an audio **input** (the mic), via
/// the CoreAudio process-object API (macOS 14+).
///
/// This is how we attribute mic usage to a *specific* app — e.g. "is Signal in a
/// call?" — which is far more robust than matching window titles, and it works
/// uniformly for Zoom/Teams/Signal and browser calls (Meet). It also lets us
/// ignore our own recording: we look at the *call app's* PID, not the global mic,
/// so a call's end is detected even while we keep the mic open.
///
/// Approach mirrors fastrepl/anarlog's `list_mic_using_apps`.
@available(macOS 14.0, *)
enum AudioInputProcesses {
    static func micUsingPIDs() -> Set<pid_t> {
        var listAddr = AudioObjectPropertyAddress(
            mSelector: kAudioHardwarePropertyProcessObjectList,
            mScope: kAudioObjectPropertyScopeGlobal,
            mElement: kAudioObjectPropertyElementMain)

        var dataSize: UInt32 = 0
        guard AudioObjectGetPropertyDataSize(
            AudioObjectID(kAudioObjectSystemObject), &listAddr, 0, nil, &dataSize) == noErr,
            dataSize > 0 else { return [] }

        let count = Int(dataSize) / MemoryLayout<AudioObjectID>.size
        var processes = [AudioObjectID](repeating: 0, count: count)
        guard AudioObjectGetPropertyData(
            AudioObjectID(kAudioObjectSystemObject), &listAddr, 0, nil, &dataSize, &processes) == noErr
        else { return [] }

        var pids = Set<pid_t>()
        for process in processes where isRunningInput(process) {
            if let pid = pid(of: process) { pids.insert(pid) }
        }
        return pids
    }

    private static func isRunningInput(_ process: AudioObjectID) -> Bool {
        var addr = AudioObjectPropertyAddress(
            mSelector: kAudioProcessPropertyIsRunningInput,
            mScope: kAudioObjectPropertyScopeGlobal,
            mElement: kAudioObjectPropertyElementMain)
        var value: UInt32 = 0
        var size = UInt32(MemoryLayout<UInt32>.size)
        guard AudioObjectGetPropertyData(process, &addr, 0, nil, &size, &value) == noErr else { return false }
        return value != 0
    }

    private static func pid(of process: AudioObjectID) -> pid_t? {
        var addr = AudioObjectPropertyAddress(
            mSelector: kAudioProcessPropertyPID,
            mScope: kAudioObjectPropertyScopeGlobal,
            mElement: kAudioObjectPropertyElementMain)
        var value: pid_t = 0
        var size = UInt32(MemoryLayout<pid_t>.size)
        guard AudioObjectGetPropertyData(process, &addr, 0, nil, &size, &value) == noErr else { return nil }
        return value
    }
}