import Foundation

enum RDEPUBBackgroundTrace {
    static func log(_ scope: String, _ message: String) {
        let threadRole = Thread.isMainThread ? "main" : "bg"
        let threadName = resolvedThreadName()
        let queueLabel = resolvedQueueLabel()
        print("[EPUB][\(scope)][\(threadRole)][queue=\(queueLabel)][thread=\(threadName)] \(message)")
    }

    static func measure<T>(_ scope: String, _ message: String, work: () throws -> T) rethrows -> T {
        let startedAt = CFAbsoluteTimeGetCurrent()
        log(scope, "START \(message)")
        do {
            let result = try work()
            let elapsedMs = Int((CFAbsoluteTimeGetCurrent() - startedAt) * 1000)
            log(scope, "END \(message) elapsedMs=\(elapsedMs)")
            return result
        } catch {
            let elapsedMs = Int((CFAbsoluteTimeGetCurrent() - startedAt) * 1000)
            log(scope, "FAIL \(message) elapsedMs=\(elapsedMs) error=\(error)")
            throw error
        }
    }

    private static func resolvedThreadName() -> String {
        if let name = Thread.current.name, !name.isEmpty {
            return name
        }
        if Thread.isMainThread {
            return "main"
        }
        return String(describing: Unmanaged.passUnretained(Thread.current).toOpaque())
    }

    private static func resolvedQueueLabel() -> String {
        String(validatingUTF8: __dispatch_queue_get_label(nil)) ?? "unknown"
    }
}