import AppKit

struct InstallError: LocalizedError {
    let errorDescription: String?
}

do {
    guard CommandLine.arguments.count == 3, !CommandLine.arguments[2].isEmpty else {
        throw InstallError(errorDescription: "Usage: swift Scripts/install.swift <Conjure.app> <installation directory>")
    }
    let manager = FileManager.default
    let identifier = "dev.conjure.launcher"
    let source = URL(fileURLWithPath: CommandLine.arguments[1], isDirectory: true)
        .standardizedFileURL.resolvingSymlinksInPath()
    let directory = URL(fileURLWithPath: (CommandLine.arguments[2] as NSString).expandingTildeInPath, isDirectory: true)
        .standardizedFileURL.resolvingSymlinksInPath()
    let destination = directory.appendingPathComponent("Conjure.app", isDirectory: true)
    guard source.path != destination.path else {
        throw InstallError(errorDescription: "The build and installation paths must be different.")
    }
    guard Bundle(url: source)?.bundleIdentifier == identifier else {
        throw InstallError(errorDescription: "The source is not a Conjure application bundle.")
    }

    func validateDestination() throws -> Bool {
        let exists = manager.fileExists(atPath: destination.path)
        if exists {
            guard try destination.resourceValues(forKeys: [.isSymbolicLinkKey]).isSymbolicLink != true,
                  Bundle(url: destination)?.bundleIdentifier == identifier else {
                throw InstallError(errorDescription: "Refusing to replace an unrelated app or symbolic link at \(destination.path).")
            }
        }
        let running = NSRunningApplication.runningApplications(withBundleIdentifier: identifier)
            .contains { $0.bundleURL?.resolvingSymlinksInPath().path == destination.path }
        guard !running else {
            throw InstallError(errorDescription: "Quit the installed Conjure at \(destination.path) before reinstalling.")
        }
        return exists
    }

    _ = try validateDestination()
    try manager.createDirectory(at: directory, withIntermediateDirectories: true)
    let staging = directory.appendingPathComponent(".Conjure-install-\(UUID().uuidString).app", isDirectory: true)
    defer { try? manager.removeItem(at: staging) }
    try manager.copyItem(at: source, to: staging)
    let verification = Process()
    verification.executableURL = URL(fileURLWithPath: "/usr/bin/codesign")
    verification.arguments = ["--verify", "--strict", staging.path]
    try verification.run()
    verification.waitUntilExit()
    guard verification.terminationStatus == 0 else {
        throw InstallError(errorDescription: "Bundle signature verification failed; the installed app was not changed.")
    }
    if try validateDestination() {
        _ = try manager.replaceItemAt(destination, withItemAt: staging, options: .usingNewMetadataOnly)
    } else {
        try manager.moveItem(at: staging, to: destination)
    }
    print("Installed Conjure at \(destination.path).")
} catch {
    FileHandle.standardError.write(Data("Installation failed: \(error.localizedDescription)\n".utf8))
    exit(1)
}