import Foundation

@main
struct FFmpegRuntimeChecks {
    static func require(_ condition: Bool, _ message: String) {
        if !condition { fatalError("FAIL: " + message) }
    }

    static func main() throws {
        let realApp = URL(fileURLWithPath: CommandLine.arguments[1], isDirectory: true)
        let directory = FileManager.default.temporaryDirectory.appendingPathComponent("terebi.ffmpeg-check.\(UUID().uuidString)", isDirectory: true)
        let app = directory.appendingPathComponent("terebi.app", isDirectory: true)
        let resources = app.appendingPathComponent("Contents/Resources", isDirectory: true)
        try FileManager.default.createDirectory(at: resources, withIntermediateDirectories: true)
        defer { try? FileManager.default.removeItem(at: directory) }
        let manifest = resources.appendingPathComponent("ffmpeg-libraries.txt")
        let required = try String(contentsOf: realApp.appendingPathComponent("Contents/Resources/ffmpeg-libraries.txt"), encoding: .utf8)
            .split(separator: "\n").map(String.init)

        require(FFmpegRuntime.error(for: app) != nil, "missing dependency metadata blocks startup")
        var unavailable = required
        let family = URL(fileURLWithPath: required[0]).lastPathComponent.split(separator: ".")[0]
        unavailable[0] = directory.appendingPathComponent("\(family).999999.dylib").path
        try (unavailable.joined(separator: "\n") + "\n").write(to: manifest, atomically: true, encoding: .utf8)
        require(FFmpegRuntime.error(for: app) != nil, "an unavailable ABI library blocks startup")
        try Data("not a dynamic library".utf8).write(to: URL(fileURLWithPath: unavailable[0]))
        require(FFmpegRuntime.error(for: app) != nil, "an existing but unloadable library also blocks startup")
        try Array(repeating: required[0], count: 5).joined(separator: "\n").write(to: manifest, atomically: true, encoding: .utf8)
        require(FFmpegRuntime.error(for: app) != nil, "duplicated entries cannot omit required library families")
        try (required.joined(separator: "\n") + "\n").write(to: manifest, atomically: true, encoding: .utf8)
        require(FFmpegRuntime.error(for: app) == nil, "all recorded native libraries load successfully")
        print("FFmpeg runtime checks passed")
    }
}