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)

        let frameworks = app.appendingPathComponent("Contents/Frameworks", isDirectory: true)
        try FileManager.default.createDirectory(at: frameworks, withIntermediateDirectories: true)
        require(FFmpegRuntime.error(for: app) != nil, "missing dependency metadata blocks startup")
        for invalid in [
            "/" + required[0], "../" + required[0], "subdirectory/" + required[0],
            "libavformat.dylib", "libavformat..dylib", "libavformat.one.dylib",
            "libavformat.1.dylib\r", "libavformat.1.dylib\0"
        ] {
            var entries = required
            entries[0] = invalid
            try (entries.joined(separator: "\n") + "\n").write(to: manifest, atomically: true, encoding: .utf8)
            require(FFmpegRuntime.error(for: app) != nil, "unsafe or unversioned metadata 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, "missing bundled libraries block startup")
        let brokenLibrary = frameworks.appendingPathComponent(required[0])
        try Data("not a dynamic library".utf8).write(to: brokenLibrary)
        require(FFmpegRuntime.error(for: app) != nil, "an existing but unloadable bundled library blocks startup")
        try FileManager.default.removeItem(at: frameworks)
        try FileManager.default.copyItem(at: realApp.appendingPathComponent("Contents/Frameworks"), to: frameworks)
        require(FFmpegRuntime.error(for: app) == nil, "isolated relocated copies of bundled native libraries load successfully")
        print("FFmpeg runtime checks passed")
    }
}