import Foundation
import SwiftFormat
import GObjectGeneratorCore

/// Command-line interface for the GIR-to-Swift binding generator.
///
/// Reads a monorepo TOML config, parses every listed GIR file, plans and
/// renders Swift wrappers, and writes the result plus C bridge scaffolding
/// to the output directory. This is the subprocess entry point invoked by
/// both the build tool plugin and the command plugin.
@main
struct GeneratorCLI {
    /// Program entry point. Parses arguments, generates code, and writes output.
    static func main() {
        let args = parseArguments()
        if args.showHelp {
            printHelp()
            return
        }

        guard !args.monorepoConfigTOML.isEmpty else {
            print("Error: --monorepo-config is required")
            print("       generator --monorepo-config regression/tier1/config.toml --output /tmp/out")
            exit(1)
        }

        guard FileManager.default.fileExists(atPath: args.monorepoConfigTOML) else {
            print("Error: monorepo config file not found: \(args.monorepoConfigTOML)")
            exit(1)
        }

        do {
            let tomlContent = try String(contentsOfFile: args.monorepoConfigTOML, encoding: .utf8)
            let toml = try TOMLReader.parse(tomlContent)
            let monorepoConfig = try MonorepoConfig.from(toml: toml, defaultOutputDir: args.output)
            let monorepoAnalyzer = MultiPackageAnalyzer(config: monorepoConfig)
            let analysis = try monorepoAnalyzer.analyze()

            let outputRoot = URL(fileURLWithPath: monorepoConfig.outputDir)

            // Plan engine (the only engine): build registry, plan, render.
            let registry = TypeRegistry(repositories: analysis.repositories, directDependencies: analysis.directDependencies)
            let modulePlans = planModules(analysis: analysis, registry: registry)

            var outputs: [String: [String: String]] = [:]
            let formatConfiguration: Configuration
            if !args.formatConfigPath.isEmpty {
                formatConfiguration = try Configuration(contentsOf: URL(fileURLWithPath: args.formatConfigPath))
            } else {
                formatConfiguration = Configuration()
            }
            let formatter = SwiftFormatter(configuration: formatConfiguration)
            func formatSwift(_ content: String, fileName: String) -> String {
                guard fileName.hasSuffix(".swift") else { return content }
                var formatted = ""
                do {
                    try formatter.format(
                        source: content, assumingFileURL: URL(fileURLWithPath: fileName),
                        selection: .infinite, to: &formatted)
                } catch {
                    return content
                }
                return formatted
            }
            for (moduleName, plan) in modulePlans {
                outputs[moduleName] = renderModule(plan)
            }

            // Write generated source files
            for (moduleName, sourceFiles) in outputs {
                let sourcesDir = outputRoot
                    .appendingPathComponent("Sources/\(moduleName)/Generated")
                try FileManager.default.createDirectory(at: sourcesDir, withIntermediateDirectories: true)
                for (fileName, content) in sourceFiles.sorted(by: { $0.key < $1.key }) {
                    let fileURL = sourcesDir.appendingPathComponent(fileName)
                    try writeIfChanged(formatSwift(content, fileName: fileName), to: fileURL)
                }
            }

            // Write scaffolding (Package.swift, C module maps, umbrella headers)
            var scaffolding = CodeGenerator.generateMonorepoScaffolding(
                analysis: analysis, includeSmokeTarget: args.includeSmokeTarget)

            // Preserve user-defined targets in Package.swift across generations
            let existingPkgPath = outputRoot.appendingPathComponent("Package.swift")
            let existingPkg = (try? String(contentsOf: existingPkgPath, encoding: .utf8)) ?? ""
            if let pkgContent = scaffolding["Package.swift"] {
                scaffolding["Package.swift"] = CodeGenerator.preserveUserTargets(
                    generated: pkgContent, existing: existingPkg)
            }
            for (relativePath, content) in scaffolding.sorted(by: { $0.key < $1.key }) {
                let fileURL = outputRoot.appendingPathComponent(relativePath)
                try FileManager.default.createDirectory(at: fileURL.deletingLastPathComponent(), withIntermediateDirectories: true)
                try writeIfChanged(formatSwift(content, fileName: relativePath), to: fileURL)
            }

            // Write skip reports
            if args.emitSkipReport {
                let reportsDir = outputRoot.appendingPathComponent("skip-reports")
                try FileManager.default.createDirectory(at: reportsDir, withIntermediateDirectories: true)
                var summary: [String: CoverageStats] = [:]
                for (moduleName, plan) in modulePlans {
                    let report = plan.skipReport
                    let fileURL = reportsDir.appendingPathComponent("\(moduleName).json")
                    try writeIfChanged(String(decoding: report.jsonData(), as: UTF8.self) + "\n", to: fileURL)
                    summary[moduleName] = report.stats
                }
                let encoder = JSONEncoder()
                encoder.outputFormatting = [.prettyPrinted, .sortedKeys, .withoutEscapingSlashes]
                let summaryData = try encoder.encode(summary)
                let summaryURL = outputRoot.appendingPathComponent("coverage-summary.json")
                try writeIfChanged(String(decoding: summaryData, as: UTF8.self) + "\n", to: summaryURL)
            }
        } catch {
            print("Error: \(error)")
            exit(1)
        }
    }
    /// Writes `content` to `fileURL` only when the on-disk content differs.
    ///
    /// Preserves file modification timestamps for unchanged outputs so that
    /// incremental `swift build` runs over generated packages stay fast.
    static func writeIfChanged(_ content: String, to fileURL: URL) throws {
        if let existing = try? String(contentsOf: fileURL, encoding: .utf8), existing == content {
            return
        }
        try content.write(to: fileURL, atomically: true, encoding: .utf8)
        print("Generated \(fileURL.path)")
    }

    /// Parsed command-line arguments for the GIR generator CLI.
    struct CLIArgs {
        var showHelp: Bool = false
        var monorepoConfigTOML: String = ""
        var output: String = "."
        var emitSkipReport: Bool = false
        var includeSmokeTarget: Bool = false
        var formatConfigPath: String = ""
    }

    /// Parses command-line arguments.
    static func parseArguments() -> CLIArgs {
        var args = Array(CommandLine.arguments.dropFirst())
        var cli = CLIArgs()

        while let flag = args.first {
            args.removeFirst()
            switch flag {
            case "--help", "-h":
                cli.showHelp = true
            case "--monorepo-config":
                cli.monorepoConfigTOML = args.isEmpty ? "" : args.removeFirst()
            case "--output":
                cli.output = args.isEmpty ? "." : args.removeFirst()
            case "--skip-report":
                cli.emitSkipReport = true
            case "--smoke-target":
                cli.includeSmokeTarget = true
            case "--format-config":
                cli.formatConfigPath = args.isEmpty ? "" : args.removeFirst()
            default:
                break
            }
        }

        return cli
    }

    /// Prints usage information to stdout.
    static func printHelp() {
        print("Usage: generator --monorepo-config PATH [options]")
        print("  --monorepo-config PATH  Monorepo TOML config (required)")
        print("  --output DIR            Output directory (default: .)")
        print("  --skip-report           Write skip-reports/<Module>.json and coverage-summary.json")
        print("  --smoke-target          Add a SmokeTests test target to the generated Package.swift")
        print("  --format-config PATH    .swift-format config to format generated output with")
        print("  --help, -h              Show this help")
    }
}