import Foundation

/// Minimal shim keeping the scaffolding extensions (`CodeGen+Scaffolding.swift`)
/// compilable. The old code-generation engine was deleted in B7; only the
/// Package.swift / module-map / umbrella-header generation survives here.
public struct CodeGenerator {
    public init() {}

    // MARK: - Re-export umbrella files

    /// Generates `@_exported import` umbrella files so every dependency is
    /// available through a single import of this module.
    static func generateReexportUmbrellas(analysis: MultiPackageAnalysis) -> [String: String] {
        var files: [String: String] = [:]
        let header = "// Generated by gobject-generator. DO NOT EDIT.\n\n"
        for (moduleName, transitive) in analysis.transitiveDependencies {
            guard !transitive.isEmpty else { continue }
            var content = header
            for dep in transitive.sorted() {
                content += "@_spi(SGTKInternal) @_exported import \(dep)\n"
            }
            content += "\n"
            files["Sources/\(moduleName)/\(moduleName).swift"] = content
        }
        return files
    }

    // MARK: - User target preservation

    /// Preserves user-defined targets between `// BEGIN_USER_TARGETS` and
    /// `// END_USER_TARGETS` markers when regenerating Package.swift.
    ///
    /// If the existing file has content between the markers, it is spliced
    /// into the freshly generated output. If either file lacks the markers,
    /// the generated output is returned unchanged.
    ///
    /// - Parameters:
    ///   - generated: The freshly generated Package.swift content.
    ///   - existing: The existing Package.swift on disk (if any).
    /// - Returns: The generated content with user targets spliced in.
    public static func preserveUserTargets(generated: String, existing: String) -> String {
        let beginMarker = "// BEGIN_USER_TARGETS"
        let endMarker = "// END_USER_TARGETS"

        guard let genStart = generated.range(of: beginMarker),
              let genEnd = generated.range(of: endMarker, range: genStart.upperBound..<generated.endIndex) else {
            return generated
        }

        // Default to keeping the generated gap (blank line and indent)
        var userContent = String(generated[genStart.upperBound..<genEnd.lowerBound])

        if let exStart = existing.range(of: beginMarker),
           let exEnd = existing.range(of: endMarker, range: exStart.upperBound..<existing.endIndex) {
            userContent = String(existing[exStart.upperBound..<exEnd.lowerBound])
        }

        var result = generated
        result.replaceSubrange(genStart.upperBound..<genEnd.lowerBound, with: userContent)
        return result
    }
}