import CNDI
import Foundation
import MusubiCore

/// Discovers NDI sources on a dedicated thread and publishes the current list.
public final class NDIFinder: @unchecked Sendable {
    // Only touched on `thread`, except for creation and `stop()`.
    private let instance: NDIlib_find_instance_t
    private let lock = NSLock()
    private var running = true
    private var thread: Thread?

    public let sources: AsyncStream<[Source]>
    private let continuation: AsyncStream<[Source]>.Continuation

    public init?(showLocalSources: Bool = true) {
        var settings = NDIlib_find_create_t(show_local_sources: showLocalSources, p_groups: nil, p_extra_ips: nil)
        guard let instance = NDIlib_find_create_v2(&settings) else { return nil }
        self.instance = instance
        (sources, continuation) = AsyncStream.makeStream(bufferingPolicy: .bufferingNewest(1))

        let thread = Thread { [weak self] in self?.run() }
        thread.name = "studio.zielke.musubi.ndi-finder"
        thread.qualityOfService = .utility
        self.thread = thread
        thread.start()
    }

    deinit {
        stop()
        NDIlib_find_destroy(instance)
    }

    public func stop() {
        lock.withLock { running = false }
        continuation.finish()
    }

    private var isRunning: Bool { lock.withLock { running } }

    private func run() {
        continuation.yield(currentSources())
        while isRunning {
            // Returns early when the list changed, otherwise after the timeout.
            if NDIlib_find_wait_for_sources(instance, 1000) {
                continuation.yield(currentSources())
            }
        }
    }

    private func currentSources() -> [Source] {
        var count: UInt32 = 0
        guard let list = NDIlib_find_get_current_sources(instance, &count) else { return [] }
        return (0..<Int(count)).compactMap { index in
            guard let name = list[index].p_ndi_name else { return nil }
            return Source(ndiName: String(cString: name))
        }
    }
}