import Foundation
import AppKit

/// Update Local: downloads DMG from remote and swaps app. No version or integrity checks.
enum AutoUpdater {

    private static let remoteDMGURL = URL(
        string: "https://git.nixc.us/colin/pommedoro/raw/branch/main/releases/Pommedoro.dmg"
    )!

    private static var supportDir: URL {
        let support = FileManager.default.urls(for: .applicationSupportDirectory, in: .userDomainMask).first!
        let dir = support.appendingPathComponent("Pommedoro", isDirectory: true)
        try? FileManager.default.createDirectory(at: dir, withIntermediateDirectories: true)
        return dir
    }

    private static var statePath: URL { supportDir.appendingPathComponent("current.sha256") }
    private static var downloadedDMGPath: URL {
        FileManager.default.temporaryDirectory.appendingPathComponent("Pommedoro-update.dmg")
    }
    private static var stagedAppPath: String { NSTemporaryDirectory() + "Pommedoro-staged.app" }
    private static var pendingStatePath: String { NSTemporaryDirectory() + "pommedoro-pending-state.txt" }

    static func updateLocal(silent: Bool = false) {
        DispatchQueue.global(qos: .utility).async { performUpdateLocal(silent: silent) }
    }

    private static func performUpdateLocal(silent: Bool) {
        if !silent { showAlert(title: "Update Local", message: "Getting latest version...") }
        let sem = DispatchSemaphore(value: 0)
        var downloadOk = false
        let task = URLSession.shared.downloadTask(with: remoteDMGURL) { url, response, _ in
            defer { sem.signal() }
            guard let url = url, (response as? HTTPURLResponse)?.statusCode == 200 else { return }
            do {
                try? FileManager.default.removeItem(at: downloadedDMGPath)
                try FileManager.default.moveItem(at: url, to: downloadedDMGPath)
                downloadOk = true
            } catch {}
        }
        task.resume()
        sem.wait()
        guard downloadOk else {
            if !silent { showAlert(title: "Update Failed", message: "Download error.") }
            return
        }
        guard stageFromDMG() else {
            if !silent { showAlert(title: "Update Failed", message: "Install error.") }
            return
        }
        try? "local\n0".write(toFile: pendingStatePath, atomically: true, encoding: .utf8)
        spawnSwapAndRelaunch()
        DispatchQueue.main.async {
            showAlert(title: "Update complete", message: "Reinstalled from remote. Restarting now.")
            NSApp.terminate(nil)
        }
    }

    private static func stageFromDMG() -> Bool {
        let dmg = downloadedDMGPath.path
        let mountPoint = "/tmp/pommedoro-update-mount"
        guard runShell("hdiutil attach \"\(dmg)\" -mountpoint \"\(mountPoint)\" -nobrowse -quiet") else { return false }
        defer {
            _ = runShell("hdiutil detach \"\(mountPoint)\" -quiet")
            try? FileManager.default.removeItem(at: downloadedDMGPath)
        }
        let srcApp = "\(mountPoint)/Pommedoro.app"
        guard FileManager.default.fileExists(atPath: srcApp) else { return false }
        try? FileManager.default.removeItem(atPath: stagedAppPath)
        do { try FileManager.default.copyItem(atPath: srcApp, toPath: stagedAppPath) }
        catch { return false }
        return true
    }

    private static func spawnSwapAndRelaunch() {
        let pid = ProcessInfo.processInfo.processIdentifier
        let staged = stagedAppPath
        let dest = "/Applications/Pommedoro.app"
        let stateFile = statePath.path
        let pending = pendingStatePath

        let script = """
        #!/bin/bash
        for i in $(seq 1 20); do kill -0 \(pid) 2>/dev/null || break; sleep 0.5; done
        rm -rf "\(dest)"
        mv "\(staged)" "\(dest)"
        xattr -cr "\(dest)"
        if [ -f "\(pending)" ]; then
          mkdir -p "$(dirname "\(stateFile)")"
          cp "\(pending)" "\(stateFile)"
          rm -f "\(pending)"
        fi
        open "\(dest)"
        """
        let scriptPath = NSTemporaryDirectory() + "pommedoro-swap.sh"
        try? script.write(toFile: scriptPath, atomically: true, encoding: .utf8)
        let proc = Process()
        proc.executableURL = URL(fileURLWithPath: "/bin/bash")
        proc.arguments = [scriptPath]
        proc.standardOutput = FileHandle.nullDevice
        proc.standardError = FileHandle.nullDevice
        proc.qualityOfService = .utility
        try? proc.run()
    }

    private static func runShell(_ command: String) -> Bool {
        let proc = Process()
        proc.executableURL = URL(fileURLWithPath: "/bin/bash")
        proc.arguments = ["-c", command]
        proc.standardOutput = FileHandle.nullDevice
        proc.standardError = FileHandle.nullDevice
        guard (try? proc.run()) != nil else { return false }
        proc.waitUntilExit()
        return proc.terminationStatus == 0
    }

    private static func showAlert(title: String, message: String) {
        DispatchQueue.main.async {
            let a = NSAlert()
            a.messageText = title
            a.informativeText = message
            a.alertStyle = .informational
            a.addButton(withTitle: "OK")
            a.runModal()
        }
    }
}