import ArgumentParser
import Foundation
import RunnerCore
import RunnerHost

/// `gitea-macos-runner vm …` — debugging helpers that operate on VMs directly,
/// without any Gitea involvement.
struct VMCommand: AsyncParsableCommand {
    static let configuration = CommandConfiguration(
        commandName: "vm",
        abstract: "Boot and inspect VMs directly (debugging).",
        subcommands: [Boot.self, List.self]
    )

    /// `vm boot --image NAME` — clone an image, boot it, print its IP, wait.
    ///
    /// The fastest way to answer "is the image itself broken, or is it the
    /// Gitea integration?". Clones the image onto slot 0's MAC, boots it, waits
    /// for a DHCP lease, prints the address and an `ssh` line, then blocks until
    /// Ctrl-C — at which point the VM is stopped and the clone deleted, exactly
    /// as the daemon would.
    struct Boot: AsyncParsableCommand {
        static let configuration = CommandConfiguration(
            commandName: "boot",
            abstract: "Clone an image, boot it, print its IP, and wait for Ctrl-C."
        )

        @OptionGroup var options: GlobalOptions

        /// Base image to clone.
        @Option(name: .long, help: "Base image to clone.")
        var image: String = "default"

        /// Which slot's persistent MAC to use.
        @Option(name: .long, help: "Slot index whose persistent MAC the clone should use.")
        var slot: Int = 0

        /// Leave the clone on disk after exit, for post-mortem inspection.
        @Flag(name: .long, help: "Do not delete the clone on exit.")
        var keep: Bool = false

        func run() async throws {
            CLI.bootstrapLogging(verbose: options.verbose)
            let config = try options.loadConfig()
            let store = VMStore(config: config)
            try store.ensureLayout()

            guard try store.image(named: image) != nil else {
                throw ValidationError("no image named '\(image)'")
            }
            try store.ensureFreeSpace(minGB: config.storage.minFreeDiskGB)

            let session = BootSession(store: store, keepClone: keep)
            let slotIndex = slot
            let imageName = image
            let bootTimeout = Duration.seconds(max(30, config.scheduler.bootTimeoutSeconds))
            let username = config.guest.username

            await VZAppRuntime.run(
                onSignal: { await session.teardown() },
                body: {
                    do {
                        let mac = try store.macAddress(
                            forSlot: slotIndex,
                            slotCount: RunnerConfig.SchedulerSection.hardMaxConcurrentVMs
                        )
                        let bundle = try store.cloneImage(named: imageName, slotMAC: mac)
                        let instance = try VMInstance(bundle: bundle, label: "vm-boot")
                        await session.adopt(bundle: bundle, instance: instance)

                        CLI.note("booting clone \(bundle.name) (mac \(mac))…")
                        try await instance.start()

                        let ip = try await VMCommand.waitForLease(mac: mac, timeout: bootTimeout)
                        print("ip:  \(ip)")
                        print("ssh: ssh \(username)@\(ip)")
                        print("")
                        CLI.note("press Ctrl-C to stop the VM and delete the clone")

                        // Whichever happens first: the guest shuts itself down,
                        // or the operator interrupts (handled by onSignal).
                        let reason = await instance.waitUntilStopped()
                        CLI.note("guest stopped: \(reason)")
                        await session.teardown()
                    } catch {
                        CLI.error("\(error)")
                        await session.teardown()
                        // Fully qualified: inside a ParsableCommand a bare `exit`
                        // resolves to ParsableCommand.exit(withError:).
                        await MainActor.run { Foundation.exit(1) }
                    }
                }
            )
        }
    }

    /// `vm list` — show ephemeral clones currently on disk.
    ///
    /// Under normal operation this is empty between jobs; anything listed after
    /// the daemon has settled is an orphan from an unclean shutdown.
    struct List: AsyncParsableCommand {
        static let configuration = CommandConfiguration(
            commandName: "list",
            abstract: "List ephemeral VM clones on disk."
        )

        @OptionGroup var options: GlobalOptions

        func run() async throws {
            let config = try options.loadConfig()
            let store = VMStore(config: config)
            try store.ensureLayout()

            let clones = try store.listClones()
            guard !clones.isEmpty else {
                print("no ephemeral clones on disk")
                return
            }

            let leases = DHCPLeaseParser.parseFile()
            print("CLONE                          MAC                IP               SIZE")
            for clone in clones {
                let bundleConfig = try? clone.loadConfig()
                let mac = bundleConfig?.macAddress ?? "-"
                let ip = bundleConfig.flatMap { DHCPLeaseParser.ipAddress(forMAC: $0.macAddress, in: leases) } ?? "-"
                let size = (try? clone.diskUsageBytes()).map(CLI.formatBytes) ?? "-"
                print(pad(clone.name, 31) + pad(mac, 19) + pad(ip, 17) + size)
            }
            print("")
            CLI.note("clones left behind after the daemon has settled are orphans; `purge` happens at daemon start")
        }

        private func pad(_ value: String, _ width: Int) -> String {
            value.count >= width
                ? value + " "
                : value + String(repeating: " ", count: width - value.count)
        }
    }

    /// Polls `/var/db/dhcpd_leases` for a MAC, as the orchestrator does.
    static func waitForLease(mac: String, timeout: Duration) async throws -> String {
        let deadline = Date().addingTimeInterval(
            TimeInterval(timeout.components.seconds)
        )
        while Date() < deadline {
            if let ip = DHCPLeaseParser.ipAddress(forMAC: mac, in: DHCPLeaseParser.parseFile()) {
                return ip
            }
            try await Task.sleep(for: .seconds(2))
        }
        throw CoreError.timeout("dhcp lease for \(mac)")
    }
}

/// Holds the VM and clone `vm boot` created, so the signal handler can tear them
/// down from outside the task that made them.
actor BootSession {
    private let store: VMStore
    private let keepClone: Bool
    private var bundle: VMBundle?
    private var instance: VMInstance?
    private var finished = false

    init(store: VMStore, keepClone: Bool) {
        self.store = store
        self.keepClone = keepClone
    }

    func adopt(bundle: VMBundle, instance: VMInstance) {
        self.bundle = bundle
        self.instance = instance
    }

    /// Stops the VM and removes the clone. Idempotent.
    func teardown() async {
        guard !finished else { return }
        finished = true

        if let instance {
            _ = await instance.requestStopThenForce(gracePeriod: .seconds(30))
        }
        guard let bundle else { return }

        if keepClone {
            CLI.note("keeping clone at \(bundle.rootURL.path)")
        } else {
            do {
                try store.deleteClone(bundle)
                CLI.note("deleted clone \(bundle.name)")
            } catch {
                CLI.error("could not delete clone: \(error)")
            }
        }
    }
}