import Vapor
import Foundation

actor BuildSessionStore {
    static let shared = BuildSessionStore()
    private var sessions: [String: BuildSession] = [:]
    func create(session: BuildSession) { sessions[session.id] = session }
    func session(for id: String) -> BuildSession? { sessions[id] }
    func remove(id: String) { sessions.removeValue(forKey: id) }
}

final class BuildSession: @unchecked Sendable {
    let id: String
    private let logger: Logger
    private var clients: [WebSocket] = []
    private let lock = NSLock()
    private var activeProcess: Process?

    init(id: String, logger: Logger) { self.id = id; self.logger = logger }

    func addClient(_ ws: WebSocket) { lock.lock(); defer { lock.unlock() }; clients.append(ws) }

    /// Terminate the active xcodebuild process. Called when iPad disconnects mid-build.
    func cancelBuild() {
        lock.lock(); let p = activeProcess; lock.unlock()
        p?.terminate()
        broadcast(BuildLogMessage(type: .status,
            text: "⚠️ Build cancelled by client disconnect.", exitCode: -2))
    }

    func broadcast(_ message: BuildLogMessage) {
        guard let data = try? JSONEncoder().encode(message),
              let text = String(data: data, encoding: .utf8) else { return }
        lock.lock(); let snap = clients; lock.unlock()
        for ws in snap where !ws.isClosed { let w = ws; Task { try? await w.send(text) } }
    }

    @discardableResult
    func runXcodebuild(arguments: [String]) async -> Int32 {
        await withCheckedContinuation { continuation in
            let process = Process()
            process.executableURL = URL(fileURLWithPath: "/usr/bin/xcodebuild")
            process.arguments = arguments
            let outPipe = Pipe(); let errPipe = Pipe()
            process.standardOutput = outPipe; process.standardError = errPipe

            // Guard against double-resume: if process.run() throws, the pipe handlers
            // still fire with empty data → group.notify would call resume a second time.
            final class ResumeOnce {
                private let lock = NSLock()
                private var done = false
                func resume(continuation: CheckedContinuation<Int32, Never>, returning value: Int32) {
                    lock.lock(); defer { lock.unlock() }
                    guard !done else { return }
                    done = true
                    continuation.resume(returning: value)
                }
            }
            let guard_ = ResumeOnce()

            let group = DispatchGroup()
            group.enter()
            outPipe.fileHandleForReading.readabilityHandler = { [weak self] h in
                let d = h.availableData
                if d.isEmpty { outPipe.fileHandleForReading.readabilityHandler = nil; group.leave(); return }
                if let t = String(data: d, encoding: .utf8) { self?.broadcast(BuildLogMessage(type: .stdout, text: t, exitCode: nil)) }
            }
            group.enter()
            errPipe.fileHandleForReading.readabilityHandler = { [weak self] h in
                let d = h.availableData
                if d.isEmpty { errPipe.fileHandleForReading.readabilityHandler = nil; group.leave(); return }
                if let t = String(data: d, encoding: .utf8) { self?.broadcast(BuildLogMessage(type: .stderr, text: t, exitCode: nil)) }
            }
            process.terminationHandler = { [weak self] proc in
                let code = proc.terminationStatus
                group.notify(queue: .global()) {
                    self?.lock.lock(); self?.activeProcess = nil; self?.lock.unlock()
                    let msg = code == 0 ? "✅ Build succeeded." : "❌ Build failed (exit \(code))."
                    self?.broadcast(BuildLogMessage(type: .status, text: msg, exitCode: Int(code)))
                    guard_.resume(continuation: continuation, returning: code)
                }
            }
            do {
                try process.run()
                lock.lock(); activeProcess = process; lock.unlock()
                logger.info("xcodebuild started. PID: \(process.processIdentifier)")
            } catch {
                broadcast(BuildLogMessage(type: .stderr, text: "Failed to launch xcodebuild: \(error)", exitCode: nil))
                guard_.resume(continuation: continuation, returning: -1)
            }
        }
    }
}