gobject-generator/Sources/SwiftGtkGenCommandPlugin/CommandPlugin.swift

import PackagePlugin
import Foundation

/// SwiftPM command plugin for manual GIR binding regeneration.
///
/// Invoked via `swift package generate-gir`. Iterates over all package
/// targets, checks for a `Config.swift` and `.gir` files, and runs the
/// `swift-gtk-gen` executable to produce or update generated Swift sources in
/// each target's `Generated/` directory.
@main
struct SwiftGtkGenCommandPlugin: CommandPlugin {
    /// Performs GIR code generation for all eligible targets in the package.
    ///
    /// For each target that has a `Config.swift` and at least one `.gir` file,
    /// launches `swift-gtk-gen` as a subprocess with arguments derived from the
    /// target's directory and metadata. Generated files are written to
    /// `<target>/Generated/`. Throws if any subprocess fails.
    ///
    /// - Parameters:
    ///   - context: The plugin context providing access to tools and package targets.
    ///   - arguments: Unused command-line arguments passed to the plugin.
    func performCommand(context: PluginContext, arguments: [String]) async throws {
        let executable = try context.tool(named: "swift-gtk-gen")

        for target in context.package.targets {
            let targetDir = target.directoryURL
            let configURL = targetDir.appending(path: "Config.swift")

            guard FileManager.default.fileExists(atPath: configURL.path()) else {
                continue
            }

            let girFiles = findGIRFiles(in: targetDir)
            guard !girFiles.isEmpty else { continue }

            let outputDir = targetDir.appending(path: "Generated")

            let process = Process()
            process.executableURL = executable.url
            process.arguments = [
                "--config", configURL.path(),
                "--library", target.name,
                "--version", "4.0",
                "--output", outputDir.path(),
            ]
            try process.run()
            process.waitUntilExit()

            guard process.terminationStatus == 0 else {
                throw SwiftGtkGenPluginError.generationFailed(target.name)
            }
        }
    }

    /// Recursively finds all `.gir` files in the given directory.
    ///
    /// Uses a directory enumerator to walk the file tree and collect URLs
    /// whose path extension is `"gir"`.
    ///
    /// - Parameter directory: The root directory to search.
    /// - Returns: An array of URLs pointing to discovered `.gir` files.
    private func findGIRFiles(in directory: URL) -> [URL] {
        guard let enumerator = FileManager.default.enumerator(
            at: directory, includingPropertiesForKeys: [.isRegularFileKey]
        ) else {
            return []
        }
        var girFiles: [URL] = []
        for case let fileURL as URL in enumerator {
            if fileURL.pathExtension == "gir" {
                girFiles.append(fileURL)
            }
        }
        return girFiles
    }
}

/// Errors that can occur during command-plugin GIR generation.
enum SwiftGtkGenPluginError: Error {
    /// Generation failed for the specified target name.
    case generationFailed(String)
}

extension SwiftGtkGenPluginError: CustomStringConvertible {
    /// A human-readable description of the error.
    var description: String {
        switch self {
        case .generationFailed(let target):
            return "GIR generation failed for target: \(target)"
        }
    }
}