//
//  Created by Nico Verbruggen on 26/05/2024.
//  Copyright © 2024 Nico Verbruggen. All rights reserved.
//

import Cocoa

open class AppSelfUpdater: NSObject, NSApplicationDelegate {

    // MARK: - Requires Configuration

    public init(appName: String, bundleIdentifiers: [String], baseUpdaterPath: String) {
        self.appName = appName
        self.bundleIdentifiers = bundleIdentifiers
        self.baseUpdaterPath = baseUpdaterPath
    }

    // MARK: - Regular Updater Flow

    // Set by the user
    private var appName: String
    private var bundleIdentifiers: [String]
    private var baseUpdaterPath: String

    // Determined during the flow of the updater
    private var updaterPath: String = ""
    private var manifestPath: String = ""
    private var manifest: ReleaseManifest! = nil

    public func applicationDidFinishLaunching(_ aNotification: Notification) {
        Alert.appName = self.appName
        Task { await self.installUpdate() }
    }

    public func applicationWillTerminate(_ aNotification: Notification) {
        exit(1)
    }

    public func applicationSupportsSecureRestorableState(_ app: NSApplication) -> Bool {
        return false
    }

    func installUpdate() async {
        print("APP SELF-UPDATER by Nico Verbruggen")
        print("Configured for \(self.appName)\n\(self.bundleIdentifiers)")
        print("===========================================")

        self.updaterPath = self.baseUpdaterPath
            .replacingOccurrences(of: "~", with: NSHomeDirectory())

        print("Updater directory set to: \(self.updaterPath)")

        self.manifestPath = "\(updaterPath)/update.json"

        // Fetch the manifest on the local filesystem
        let manifest = await parseManifest()!

        // Download the latest file
        let zipPath = await download(manifest)

        // Terminate all instances of app first
        await LaunchControl.terminateApplications(bundleIds: self.bundleIdentifiers)

        // Install the app based on the zip
        let appPath = await extractAndInstall(zipPath: zipPath)

        // Restart app, this will also close the updater
        _ = await LaunchControl.startApplication(at: appPath)

        exit(1)
    }

    private func parseManifest() async -> ReleaseManifest? {
        // Read out the correct information from the manifest JSON
        print("Checking manifest file at \(manifestPath)...")

        do {
            let manifestText = try String(contentsOfFile: manifestPath)
            manifest = try JSONDecoder().decode(ReleaseManifest.self, from: manifestText.data(using: .utf8)!)
            return manifest
        } catch {
            print("Parsing the manifest failed (or the manifest file doesn't exist)!")
            await Alert.show(description: "The manifest file for a potential update was not found. Please try searching for updates again in \(appName).")
        }

        return nil
    }

    private func download(_ manifest: ReleaseManifest) async -> String {
        // Remove all zips
        system_quiet("rm -rf \(updaterPath)/*.zip")

        // Download the file (and follow redirects + no output on failure)
        system_quiet("cd \"\(updaterPath)\" && curl \(manifest.url) -fLO --max-time 20")

        // Identify the downloaded file
        let filename = system("cd \"\(updaterPath)\" && ls | grep .zip")
            .trimmingCharacters(in: .whitespacesAndNewlines)

        // Ensure the zip exists
        if filename.isEmpty {
            print("The update has not been downloaded. Sadly, that means that \(appName) cannot not updated!")
            await Alert.show(description: "The update could not be downloaded, or the file was not correctly written to disk. \n\nPlease try again. \n\n(Note that the download will time-out after 20 seconds, so for slow connections it is recommended to manually download the update.)")
        }

        // Calculate the checksum for the downloaded file
        let checksum = system("openssl dgst -sha256 \"\(updaterPath)/\(filename)\" | awk '{print $NF}'")
            .trimmingCharacters(in: .whitespacesAndNewlines)

        // Compare the checksums
        print("""
        Comparing checksums...
        Expected SHA256: \(manifest.sha256)
        Actual SHA256: \(checksum)
        """)

        // Make sure the checksum matches before we do anything with the file
        if checksum != manifest.sha256 {
            print("The checksums failed to match. Cancelling!")
            await Alert.show(description: "The downloaded update failed checksum validation. Please try again. If this issue persists, there may be an issue with the server and I do not recommend upgrading.")
        }

        // Return the path to the zip
        return "\(updaterPath)/\(filename)"
    }

    private func extractAndInstall(zipPath: String) async -> String {
        // Remove the directory that will contain the extracted update
        system_quiet("rm -rf \"\(updaterPath)/extracted\"")

        // Recreate the directory where we will unzip the .app file
        system_quiet("mkdir -p \"\(updaterPath)/extracted\"")

        // Make sure the updater directory exists
        var isDirectory: ObjCBool = true
        if !FileManager.default.fileExists(atPath: "\(updaterPath)/extracted", isDirectory: &isDirectory) {
            await Alert.show(description: "The updater directory is missing. The automatic updater will quit. Make sure that `\(baseUpdaterPath)` is writeable.")
        }

        // Unzip the file
        system_quiet("unzip \"\(zipPath)\" -d \"\(updaterPath)/extracted\"")

        // Find the .app file
        let app = system("ls \"\(updaterPath)/extracted\" | grep .app")
            .trimmingCharacters(in: .whitespacesAndNewlines)

        print("Finished extracting: \(updaterPath)/extracted/\(app)")

        // Make sure the file was extracted
        if app.isEmpty {
            await Alert.show(description: "The downloaded file could not be extracted. The automatic updater will quit. Make sure that `\(baseUpdaterPath)` is writeable.")
        }

        // Remove the original app
        print("Removing \(app) before replacing...")
        system_quiet("rm -rf \"/Applications/\(app)\"")

        // Move the new app in place
        system_quiet("mv \"\(updaterPath)/extracted/\(app)\" \"/Applications/\(app)\"")

        // Remove the zip
        system_quiet("rm \"\(zipPath)\"")

        // Remove the manifest
        system_quiet("rm \"\(manifestPath)\"")

        // Write a file that is only written when we upgraded successfully
        system_quiet("touch \"\(updaterPath)/upgrade.success\"")

        // Return the new location of the app
        return "/Applications/\(app)"
    }
}