Workspace+Configuration.swift

//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift open source project
//
// Copyright (c) 2018-2023 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See http://swift.org/LICENSE.txt for license information
// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//

import Basics
import Foundation
import PackageFingerprint
import PackageGraph
import PackageLoading
import PackageModel
import PackageRegistry

import struct TSCBasic.ByteString

import protocol TSCUtility.SimplePersistanceProtocol
import class TSCUtility.SimplePersistence

// MARK: - Location

extension Workspace {
    /// Workspace location configuration
    public struct Location {
        /// Path to scratch space (working) directory for this workspace (aka .build).
        public var scratchDirectory: AbsolutePath

        /// Path to store the editable versions of dependencies.
        public var editsDirectory: AbsolutePath

        /// Path to the Package.resolved file.
        public var resolvedVersionsFile: AbsolutePath

        /// Path to the local configuration directory.
        public var localConfigurationDirectory: AbsolutePath

        /// Path to the shared configuration directory.
        public var sharedConfigurationDirectory: AbsolutePath?

        /// Path to the shared security directory.
        public var sharedSecurityDirectory: AbsolutePath?

        /// Path to the shared cache directory.
        public var sharedCacheDirectory: AbsolutePath?

        /// Path to the shared Swift SDKs directory.
        public var sharedSwiftSDKsDirectory: AbsolutePath?

        /// Whether or not to emit a warning about the existence of deprecated configuration files.
        public var emitDeprecatedConfigurationWarning: Bool

        // working directories

        /// Path to the repositories clones.
        public var repositoriesDirectory: AbsolutePath {
            self.scratchDirectory.appending("repositories")
        }

        /// Path to the repository checkouts.
        public var repositoriesCheckoutsDirectory: AbsolutePath {
            self.scratchDirectory.appending("checkouts")
        }

        /// Path to the registry downloads.
        public var registryDownloadDirectory: AbsolutePath {
            self.scratchDirectory.appending(components: "registry", "downloads")
        }

        /// Path to the downloaded binary artifacts.
        public var artifactsDirectory: AbsolutePath {
            self.scratchDirectory.appending("artifacts")
        }

        /// Path to the downloaded prebuilts directory
        public var prebuiltsDirectory: AbsolutePath {
            self.scratchDirectory.appending("prebuilts")
        }

        // Path to temporary files related to running plugins in the workspace
        public var pluginWorkingDirectory: AbsolutePath {
            self.scratchDirectory.appending("plugins")
        }

        // config locations

        /// Path to the local mirrors configuration.
        public var localMirrorsConfigurationFile: AbsolutePath {
            get throws {
                // backwards compatibility
                if let customPath = Environment.current["SWIFTPM_MIRROR_CONFIG"] {
                    return try AbsolutePath(validating: customPath)
                }
                return DefaultLocations.mirrorsConfigurationFile(at: self.localConfigurationDirectory)
            }
        }

        /// Path to the shared mirrors configuration.
        public var sharedMirrorsConfigurationFile: AbsolutePath? {
            self.sharedConfigurationDirectory.map { DefaultLocations.mirrorsConfigurationFile(at: $0) }
        }

        /// Path to the local registries configuration.
        public var localRegistriesConfigurationFile: AbsolutePath {
            DefaultLocations.registriesConfigurationFile(at: self.localConfigurationDirectory)
        }

        /// Path to the shared registries configuration.
        public var sharedRegistriesConfigurationFile: AbsolutePath? {
            self.sharedConfigurationDirectory.map { DefaultLocations.registriesConfigurationFile(at: $0) }
        }

        // security locations

        /// Path to the shared fingerprints directory.
        public var sharedFingerprintsDirectory: AbsolutePath? {
            self.sharedSecurityDirectory.map { $0.appending("fingerprints") }
        }

        /// Path to the shared directory where package signing records are kept.
        public var sharedSigningEntitiesDirectory: AbsolutePath? {
            self.sharedSecurityDirectory.map { $0.appending("signing-entities") }
        }

        /// Path to the shared trusted root certificates directory.
        public var sharedTrustedRootCertificatesDirectory: AbsolutePath? {
            self.sharedSecurityDirectory.map { $0.appending("trusted-root-certs") }
        }

        // cache locations

        /// Path to the shared manifests cache.
        public var sharedManifestsCacheDirectory: AbsolutePath? {
            self.sharedCacheDirectory.map { DefaultLocations.manifestsDirectory(at: $0) }
        }

        /// Path to the shared repositories cache.
        public var sharedRepositoriesCacheDirectory: AbsolutePath? {
            self.sharedCacheDirectory.map { $0.appending("repositories") }
        }

        /// Path to the shared registry download cache.
        public var sharedRegistryDownloadsCacheDirectory: AbsolutePath? {
            self.sharedCacheDirectory.map { $0.appending(components: "registry", "downloads") }
        }

        /// Path to the shared repositories cache.
        public var sharedBinaryArtifactsCacheDirectory: AbsolutePath? {
            self.sharedCacheDirectory.map { $0.appending("artifacts") }
        }

        /// Path to the shared prebuilts cache
        public var sharedPrebuiltsCacheDirectory: AbsolutePath? {
            self.sharedCacheDirectory.map { $0.appending("prebuilts")}
        }

        /// Create a new workspace location.
        ///
        /// - Parameters:
        ///   - scratchDirectory: Path to scratch space (working) directory for this workspace.
        ///   - editsDirectory: Path to store the editable versions of dependencies.
        ///   - resolvedVersionsFile: Path to the Package.resolved file.
        ///   - sharedSecurityDirectory: Path to the shared security directory.
        ///   - sharedCacheDirectory: Path to the shared cache directory.
        ///   - sharedConfigurationDirectory: Path to the shared configuration directory.
        public init(
            scratchDirectory: AbsolutePath,
            editsDirectory: AbsolutePath,
            resolvedVersionsFile: AbsolutePath,
            localConfigurationDirectory: AbsolutePath,
            sharedConfigurationDirectory: AbsolutePath?,
            sharedSecurityDirectory: AbsolutePath?,
            sharedCacheDirectory: AbsolutePath?,
            emitDeprecatedConfigurationWarning: Bool = true
        ) {
            self.scratchDirectory = scratchDirectory
            self.editsDirectory = editsDirectory
            self.resolvedVersionsFile = resolvedVersionsFile
            self.localConfigurationDirectory = localConfigurationDirectory
            self.sharedConfigurationDirectory = sharedConfigurationDirectory
            self.sharedSecurityDirectory = sharedSecurityDirectory
            self.sharedCacheDirectory = sharedCacheDirectory
            self.emitDeprecatedConfigurationWarning = emitDeprecatedConfigurationWarning
        }

        /// Create a new workspace location.
        ///
        /// - Parameters:
        ///   - rootPath: Path to the root of the package, from which other locations can be derived.
        public init(forRootPackage rootPath: AbsolutePath, fileSystem: FileSystem) throws {
            try self.init(
                scratchDirectory: DefaultLocations.scratchDirectory(forRootPackage: rootPath),
                editsDirectory: DefaultLocations.editsDirectory(forRootPackage: rootPath),
                resolvedVersionsFile: DefaultLocations.resolvedVersionsFile(forRootPackage: rootPath),
                localConfigurationDirectory: DefaultLocations.configurationDirectory(forRootPackage: rootPath),
                sharedConfigurationDirectory: fileSystem.swiftPMConfigurationDirectory,
                sharedSecurityDirectory: fileSystem.swiftPMSecurityDirectory,
                sharedCacheDirectory: fileSystem.swiftPMCacheDirectory
            )
        }
    }
}

// MARK: - Default locations

extension Workspace {
    /// Workspace default locations utilities
    public struct DefaultLocations {
        public static var resolvedFileName = "Package.resolved"

        public static func scratchDirectory(forRootPackage rootPath: AbsolutePath) -> AbsolutePath {
            rootPath.appending(".build")
        }

        public static func editsDirectory(forRootPackage rootPath: AbsolutePath) -> AbsolutePath {
            rootPath.appending("Packages")
        }

        public static func resolvedVersionsFile(forRootPackage rootPath: AbsolutePath) -> AbsolutePath {
            rootPath.appending(self.resolvedFileName)
        }

        public static func configurationDirectory(forRootPackage rootPath: AbsolutePath) -> AbsolutePath {
            rootPath.appending(components: ".swiftpm", "configuration")
        }

        public static func mirrorsConfigurationFile(forRootPackage rootPath: AbsolutePath) -> AbsolutePath {
            self.mirrorsConfigurationFile(at: self.configurationDirectory(forRootPackage: rootPath))
        }

        public static func mirrorsConfigurationFile(at path: AbsolutePath) -> AbsolutePath {
            path.appending("mirrors.json")
        }

        public static func registriesConfigurationFile(forRootPackage rootPath: AbsolutePath) -> AbsolutePath {
            self.registriesConfigurationFile(at: self.configurationDirectory(forRootPackage: rootPath))
        }

        public static func registriesConfigurationFile(at path: AbsolutePath) -> AbsolutePath {
            path.appending("registries.json")
        }

        public static func manifestsDirectory(at path: AbsolutePath) -> AbsolutePath {
            path.appending("manifests")
        }
    }

    public static func migrateMirrorsConfiguration(
        from legacyPath: AbsolutePath,
        to newPath: AbsolutePath,
        observabilityScope: ObservabilityScope
    ) throws -> AbsolutePath {
        if localFileSystem.isFile(legacyPath) {
            if localFileSystem.isSymlink(legacyPath) {
                let resolvedLegacyPath = try resolveSymlinks(legacyPath)
                return try self.migrateMirrorsConfiguration(
                    from: resolvedLegacyPath,
                    to: newPath,
                    observabilityScope: observabilityScope
                )
            } else if localFileSystem.isFile(newPath.parentDirectory) {
                observabilityScope
                    .emit(
                        warning: "Unable to migrate legacy mirrors configuration, because \(newPath.parentDirectory) already exists."
                    )
            } else if let content = try? localFileSystem.readFileContents(legacyPath), content.count > 0 {
                observabilityScope
                    .emit(
                        warning: "Usage of \(legacyPath) has been deprecated. Please delete it and use the new \(newPath) instead."
                    )
                if !localFileSystem.exists(newPath, followSymlink: false) {
                    try localFileSystem.createDirectory(newPath.parentDirectory, recursive: true)
                    try localFileSystem.copy(from: legacyPath, to: newPath)
                }
            }
        }
        return newPath.parentDirectory
    }
}

// MARK: - Authorization

extension Workspace.Configuration {
    public struct Authorization {
        public var netrc: Netrc
        public var keychain: Keychain

        public static var `default`: Self {
            #if canImport(Security)
            Self(netrc: .user, keychain: .enabled)
            #else
            Self(netrc: .user, keychain: .disabled)
            #endif
        }

        public init(netrc: Netrc, keychain: Keychain) {
            self.netrc = netrc
            self.keychain = keychain
        }

        public func makeAuthorizationProvider(
            fileSystem: FileSystem,
            observabilityScope: ObservabilityScope
        ) throws -> AuthorizationProvider? {
            var providers = [AuthorizationProvider]()

            let env = Environment.current
            if let token = env[.swiftpmSourceControlToken], !token.isEmpty {
                providers.append(EnvironmentAuthorizationProvider(kind: .sourceControl))
            }

            if let netrcData = env[.swiftpmNetrcData], !netrcData.isEmpty {
                do {
                    providers.append(try InMemoryNetrcAuthorizationProvider(content: netrcData))
                } catch {
                    observabilityScope.emit(
                        warning: "Failed to parse SWIFTPM_NETRC_DATA environment variable",
                        underlyingError: error
                    )
                }
            }

            switch self.netrc {
            case .custom(let path):
                guard fileSystem.exists(path) else {
                    throw StringError("Did not find netrc file at \(path).")
                }
                try providers.append(NetrcAuthorizationProvider(path: path, fileSystem: fileSystem))
            case .user:
                // user .netrc file (most typical)
                let userHomePath = try fileSystem.homeDirectory.appending(".netrc")

                // user didn't tell us to explicitly use these .netrc files so be more lenient with errors
                if let userHomeProvider = self.loadOptionalNetrc(
                    fileSystem: fileSystem,
                    path: userHomePath,
                    observabilityScope: observabilityScope
                ) {
                    providers.append(userHomeProvider)
                }
            case .disabled:
                // noop
                break
            }

            switch self.keychain {
            case .enabled:
                #if canImport(Security)
                providers.append(KeychainAuthorizationProvider(observabilityScope: observabilityScope))
                #else
                throw InternalError("Keychain not supported on this platform")
                #endif
            case .disabled:
                // noop
                break
            }

            return providers.isEmpty ? .none : CompositeAuthorizationProvider(
                providers,
                observabilityScope: observabilityScope
            )
        }

        public func makeRegistryAuthorizationProvider(
            fileSystem: FileSystem,
            observabilityScope: ObservabilityScope
        ) throws -> AuthorizationProvider? {
            let env = Environment.current
            if let token = env[.swiftpmRegistryToken], !token.isEmpty {
                return EnvironmentAuthorizationProvider(kind: .registry)
            }
            if let login = env[.swiftpmRegistryLogin], !login.isEmpty,
               let password = env[.swiftpmRegistryPassword], !password.isEmpty {
                return EnvironmentAuthorizationProvider(kind: .registry)
            } else if let login = env[.swiftpmRegistryLogin], !login.isEmpty {
                observabilityScope.emit(
                    warning: "SWIFTPM_REGISTRY_LOGIN is set but SWIFTPM_REGISTRY_PASSWORD is not; both are required for login/password authentication"
                )
            } else if let password = env[.swiftpmRegistryPassword], !password.isEmpty {
                observabilityScope.emit(
                    warning: "SWIFTPM_REGISTRY_PASSWORD is set but SWIFTPM_REGISTRY_LOGIN is not; both are required for login/password authentication"
                )
            }
            if let netrcData = env[.swiftpmNetrcData], !netrcData.isEmpty {
                do {
                    return try InMemoryNetrcAuthorizationProvider(content: netrcData)
                } catch {
                    observabilityScope.emit(
                        warning: "Failed to parse SWIFTPM_NETRC_DATA environment variable",
                        underlyingError: error
                    )
                }
            }

            var providers = [AuthorizationProvider]()

            // OS-specific AuthorizationProvider has higher precedence
            switch self.keychain {
            case .enabled:
                #if canImport(Security)
                providers.append(KeychainAuthorizationProvider(observabilityScope: observabilityScope))
                #else
                throw InternalError("Keychain not supported on this platform")
                #endif
            case .disabled:
                // noop
                break
            }

            switch self.netrc {
            case .custom(let path):
                guard fileSystem.exists(path) else {
                    throw StringError("did not find netrc file at \(path)")
                }
                try providers.append(NetrcAuthorizationProvider(path: path, fileSystem: fileSystem))
            case .user:
                let userHomePath = try fileSystem.homeDirectory.appending(".netrc")
                // Add user .netrc file unless we don't have access
                if let userHomeProvider = try? NetrcAuthorizationProvider(path: userHomePath, fileSystem: fileSystem) {
                    providers.append(userHomeProvider)
                }
            case .disabled:
                throw InternalError("netrc file should not have been disabled")
            }

            // Use at-most one AuthorizationProvider (i.e., no CompositeAuthorizationProvider)
            return providers.first
        }

        private func loadOptionalNetrc(
            fileSystem: FileSystem,
            path: AbsolutePath,
            observabilityScope: ObservabilityScope
        ) -> NetrcAuthorizationProvider? {
            guard fileSystem.exists(path) && fileSystem.isReadable(path) else {
                return .none
            }

            do {
                return try NetrcAuthorizationProvider(path: path, fileSystem: fileSystem)
            } catch {
                observabilityScope.emit(
                    warning: "Failed to load netrc file at \(path)",
                    underlyingError: error
                )
                return .none
            }
        }

        public enum Netrc {
            case disabled
            case custom(AbsolutePath)
            case user
        }

        public enum Keychain {
            case disabled
            case enabled
        }
    }
}

// MARK: - Mirrors

extension Workspace.Configuration {
    public struct Mirrors {
        private let localMirrors: MirrorsStorage
        private let sharedMirrors: MirrorsStorage?
        private let fileSystem: FileSystem

        private var _mirrors: DependencyMirrors
        private let lock = NSLock()

        /// The mirrors in this configuration
        public var mirrors: DependencyMirrors {
            self.lock.withLock {
                self._mirrors
            }
        }

        /// A convenience initializer for creating a workspace mirrors configuration for the given root
        /// package path.
        ///
        /// - Parameters:
        ///   - forRootPackage: The path for the root package.
        ///   - sharedMirrorFile: Path to the shared mirrors configuration file, defaults to the standard location.
        ///   - fileSystem: The file system to use.
        public init(
            forRootPackage rootPath: AbsolutePath,
            sharedMirrorFile: AbsolutePath?,
            fileSystem: FileSystem
        ) throws {
            let localMirrorConfigFile = Workspace.DefaultLocations.mirrorsConfigurationFile(forRootPackage: rootPath)
            try self.init(
                fileSystem: fileSystem,
                localMirrorsFile: localMirrorConfigFile,
                sharedMirrorsFile: sharedMirrorFile
            )
        }

        /// Initialize the workspace mirrors configuration
        ///
        /// - Parameters:
        ///   - fileSystem: The file system to use.
        ///   - localMirrorsFile: Path to the workspace mirrors configuration file
        ///   - sharedMirrorsFile: Path to the shared mirrors configuration file, defaults to the standard location.
        public init(
            fileSystem: FileSystem,
            localMirrorsFile: AbsolutePath,
            sharedMirrorsFile: AbsolutePath?
        ) throws {
            self.localMirrors = .init(path: localMirrorsFile, fileSystem: fileSystem, deleteWhenEmpty: true)
            self.sharedMirrors = sharedMirrorsFile
                .map { .init(path: $0, fileSystem: fileSystem, deleteWhenEmpty: false) }
            self.fileSystem = fileSystem
            // computes the initial mirrors
            self._mirrors = try DependencyMirrors()
            try self.computeMirrors()
        }

        @discardableResult
        public func applyLocal(handler: (inout DependencyMirrors) throws -> Void) throws -> DependencyMirrors {
            try self.localMirrors.apply(handler: handler)
            try self.computeMirrors()
            return self.mirrors
        }

        @discardableResult
        public func applyShared(handler: (inout DependencyMirrors) throws -> Void) throws -> DependencyMirrors {
            guard let sharedMirrors else {
                throw InternalError("shared mirrors not configured")
            }
            try sharedMirrors.apply(handler: handler)
            try self.computeMirrors()
            return self.mirrors
        }

        // mutating the state we hold since we are passing it by reference to the workspace
        // access should be done using a lock
        private func computeMirrors() throws {
            try self.lock.withLock {
                self._mirrors.removeAll()

                // prefer local mirrors to shared ones
                let local = try self.localMirrors.get()
                if !local.isEmpty {
                    try self._mirrors.append(contentsOf: local)
                    return
                }

                // use shared if local was not found or empty
                if let shared = try self.sharedMirrors?.get(), !shared.isEmpty {
                    try self._mirrors.append(contentsOf: shared)
                }
            }
        }
    }
}

extension Workspace.Configuration {
    public struct MirrorsStorage {
        private let path: AbsolutePath
        private let fileSystem: FileSystem
        private let deleteWhenEmpty: Bool

        public init(path: AbsolutePath, fileSystem: FileSystem, deleteWhenEmpty: Bool) {
            self.path = path
            self.fileSystem = fileSystem
            self.deleteWhenEmpty = deleteWhenEmpty
        }

        /// The mirrors in this configuration
        public func get() throws -> DependencyMirrors {
            guard self.fileSystem.exists(self.path) else {
                return try DependencyMirrors()
            }
            return try self.fileSystem.withLock(on: self.path.parentDirectory, type: .shared) {
                try DependencyMirrors(Self.load(self.path, fileSystem: self.fileSystem))
            }
        }

        /// Apply a mutating handler on the mirrors in this configuration
        @discardableResult
        public func apply(handler: (inout DependencyMirrors) throws -> Void) throws -> DependencyMirrors {
            if !self.fileSystem.exists(self.path.parentDirectory) {
                try self.fileSystem.createDirectory(self.path.parentDirectory, recursive: true)
            }
            return try self.fileSystem.withLock(on: self.path.parentDirectory, type: .exclusive) {
                let mirrors = try DependencyMirrors(Self.load(self.path, fileSystem: self.fileSystem))
                var updatedMirrors = try DependencyMirrors(mirrors.mapping)
                try handler(&updatedMirrors)
                if updatedMirrors != mirrors {
                    try Self.save(
                        updatedMirrors.mapping,
                        to: self.path,
                        fileSystem: self.fileSystem,
                        deleteWhenEmpty: self.deleteWhenEmpty
                    )
                }
                return updatedMirrors
            }
        }

        private static func load(_ path: AbsolutePath, fileSystem: FileSystem) throws -> [String: String] {
            guard fileSystem.exists(path) else {
                return [:]
            }
            let data: Data = try fileSystem.readFileContents(path)
            let decoder = JSONDecoder.makeWithDefaults()
            let mirrors = try decoder.decode(MirrorsStorage.self, from: data)
            let mirrorsMap = Dictionary(
                mirrors.object.map { ($0.original, $0.mirror) },
                uniquingKeysWith: { first, _ in first }
            )
            return mirrorsMap
        }

        private static func save(
            _ mirrors: [String: String],
            to path: AbsolutePath,
            fileSystem: FileSystem,
            deleteWhenEmpty: Bool
        ) throws {
            if mirrors.isEmpty {
                if deleteWhenEmpty && fileSystem.exists(path) {
                    // deleteWhenEmpty is a backward compatibility mode
                    return try fileSystem.removeFileTree(path)
                } else if !fileSystem.exists(path) {
                    // nothing to do
                    return
                }
            }

            let encoder = JSONEncoder.makeWithDefaults()
            let mirrors = MirrorsStorage(version: 1, object: mirrors.map { .init(original: $0, mirror: $1) })
            let data = try encoder.encode(mirrors)
            if !fileSystem.exists(path.parentDirectory) {
                try fileSystem.createDirectory(path.parentDirectory, recursive: true)
            }
            try fileSystem.writeFileContents(path, data: data)
        }

        // structure is for backwards compatibility
        private struct MirrorsStorage: Codable {
            var version: Int
            var object: [Mirror]

            struct Mirror: Codable {
                var original: String
                var mirror: String
            }
        }
    }
}

// MARK: - Registries

extension Workspace.Configuration {
    public class Registries {
        private let localRegistries: RegistriesStorage?
        private let sharedRegistries: RegistriesStorage?
        private let fileSystem: FileSystem

        private var _configuration = RegistryConfiguration()
        private let lock = NSLock()

        /// The registry configuration
        public var configuration: RegistryConfiguration {
            self.lock.withLock {
                self._configuration
            }
        }

        /// Initialize the workspace registries configuration
        ///
        /// - Parameters:
        ///   - fileSystem: The file system to use.
        ///   - localRegistriesFile: Path to the workspace registries configuration file
        ///   - sharedRegistriesFile: Path to the shared registries configuration file,
        ///                           defaults to the standard location.
        public init(
            fileSystem: FileSystem,
            localRegistriesFile: AbsolutePath?,
            sharedRegistriesFile: AbsolutePath?
        ) throws {
            // At least one of local or shared is required
            if localRegistriesFile == nil, sharedRegistriesFile == nil {
                throw StringError("No registries configuration provided")
            }

            self.fileSystem = fileSystem
            self.localRegistries = localRegistriesFile.map { .init(path: $0, fileSystem: fileSystem) }
            self.sharedRegistries = sharedRegistriesFile.map { .init(path: $0, fileSystem: fileSystem) }
            try self.computeRegistries()
        }

        @discardableResult
        public func updateLocal(with handler: (inout RegistryConfiguration) throws -> Void) throws
            -> RegistryConfiguration
        {
            guard let localRegistries else {
                throw InternalError("local registries not configured")
            }
            try localRegistries.update(with: handler)
            try self.computeRegistries()
            return self.configuration
        }

        @discardableResult
        public func updateShared(with handler: (inout RegistryConfiguration) throws -> Void) throws
            -> RegistryConfiguration
        {
            guard let sharedRegistries else {
                throw InternalError("shared registries not configured")
            }
            try sharedRegistries.update(with: handler)
            try self.computeRegistries()
            return self.configuration
        }

        // mutating the state we hold since we are passing it by reference to the workspace
        // access should be done using a lock
        private func computeRegistries() throws {
            try self.lock.withLock {
                var configuration = RegistryConfiguration()

                if let sharedConfiguration = try sharedRegistries?.load() {
                    configuration.merge(sharedConfiguration)
                }

                if let localConfiguration = try localRegistries?.load() {
                    configuration.merge(localConfiguration)
                }

                self._configuration = configuration
            }
        }
    }
}

extension Workspace.Configuration {
    private struct RegistriesStorage {
        private let path: AbsolutePath
        private let fileSystem: FileSystem

        public init(path: AbsolutePath, fileSystem: FileSystem) {
            self.path = path
            self.fileSystem = fileSystem
        }

        public func load() throws -> RegistryConfiguration {
            guard self.fileSystem.exists(self.path) else {
                return RegistryConfiguration()
            }

            do {
                let decoder = JSONDecoder.makeWithDefaults()
                return try decoder.decode(path: self.path, fileSystem: self.fileSystem, as: RegistryConfiguration.self)
            } catch {
                throw StringError(
                    "Failed loading registries configuration from '\(self.path)': \(error.interpolationDescription)"
                )
            }
        }

        public func save(_ configuration: RegistryConfiguration) throws {
            let encoder = JSONEncoder.makeWithDefaults()
            let data = try encoder.encode(configuration)

            if !self.fileSystem.exists(self.path.parentDirectory) {
                try self.fileSystem.createDirectory(self.path.parentDirectory, recursive: true)
            }
            try self.fileSystem.writeFileContents(self.path, data: data)
        }

        @discardableResult
        public func update(with handler: (inout RegistryConfiguration) throws -> Void) throws -> RegistryConfiguration {
            let configuration = try load()
            var updatedConfiguration = configuration
            try handler(&updatedConfiguration)
            if updatedConfiguration != configuration {
                try self.save(updatedConfiguration)
            }

            return updatedConfiguration
        }
    }
}

// FIXME: better name
public struct WorkspaceConfiguration {
    /// Enables the dependencies resolver automatic version updates.  Disabled by default.
    /// When disabled the resolver does not attempt to update the dependencies as part of resolution.
    public var skipDependenciesUpdates: Bool

    /// Enables the dependencies resolver prefetching based on the resolved versions file.  Enabled by default.
    /// When disabled the resolver does not attempt to pre-fetch the dependencies based on the  resolved versions file.
    public var prefetchBasedOnResolvedFile: Bool

    /// File rules to determine resource handling behavior.
    public var additionalFileRules: [FileRuleDescription]

    /// Enables the shared dependencies cache. Enabled by default.
    public var sharedDependenciesCacheEnabled: Bool

    ///  Fingerprint checking mode. Defaults to strict.
    public var fingerprintCheckingMode: CheckingMode

    ///  Signing entity checking mode. Defaults to warn.
    public var signingEntityCheckingMode: CheckingMode

    /// Whether to skip validating signature of signed packages downloaded from registry
    public var skipSignatureValidation: Bool

    ///  Attempt to transform source control based dependencies to registry ones
    public var sourceControlToRegistryDependencyTransformation: SourceControlToRegistryDependencyTransformation?

    /// URL of the implicitly configured, default registry
    public var defaultRegistry: Registry?

    /// Whether to create multiple test products or one per package
    public var shouldCreateMultipleTestProducts: Bool

    /// Whether to create a product for use in the Swift REPL
    public var createREPLProduct: Bool

    /// Whether or not there should be import restrictions applied when loading manifests
    public var manifestImportRestrictions: (startingToolsVersion: ToolsVersion, allowedImports: [String])?

    /// Whether or not to use prebuilt swift-syntax for macros
    public var usePrebuilts: Bool

    /// String URL to allow override of the prebuilts download location
    public var prebuiltsDownloadURL: String?

    /// Path to root certificate used when validating the manifest signing during testing
    public var prebuiltsRootCertPath: String?

    /// Whether to omit unused dependencies.
    public var pruneDependencies: Bool

    /// The trait configuration for the root.
    public var traitConfiguration: TraitConfiguration

    public init(
        skipDependenciesUpdates: Bool,
        prefetchBasedOnResolvedFile: Bool,
        shouldCreateMultipleTestProducts: Bool,
        createREPLProduct: Bool,
        additionalFileRules: [FileRuleDescription],
        sharedDependenciesCacheEnabled: Bool,
        fingerprintCheckingMode: CheckingMode,
        signingEntityCheckingMode: CheckingMode,
        skipSignatureValidation: Bool,
        sourceControlToRegistryDependencyTransformation: SourceControlToRegistryDependencyTransformation?,
        defaultRegistry: Registry?,
        manifestImportRestrictions: (startingToolsVersion: ToolsVersion, allowedImports: [String])?,
        usePrebuilts: Bool,
        prebuiltsDownloadURL: String?,
        prebuiltsRootCertPath: String?,
        pruneDependencies: Bool,
        traitConfiguration: TraitConfiguration
    ) {
        self.skipDependenciesUpdates = skipDependenciesUpdates
        self.prefetchBasedOnResolvedFile = prefetchBasedOnResolvedFile
        self.shouldCreateMultipleTestProducts = shouldCreateMultipleTestProducts
        self.createREPLProduct = createREPLProduct
        self.additionalFileRules = additionalFileRules
        self.sharedDependenciesCacheEnabled = sharedDependenciesCacheEnabled
        self.fingerprintCheckingMode = fingerprintCheckingMode
        self.signingEntityCheckingMode = signingEntityCheckingMode
        self.skipSignatureValidation = skipSignatureValidation
        self.sourceControlToRegistryDependencyTransformation = sourceControlToRegistryDependencyTransformation
        self.defaultRegistry = defaultRegistry
        self.manifestImportRestrictions = manifestImportRestrictions
        self.usePrebuilts = usePrebuilts
        self.prebuiltsDownloadURL = prebuiltsDownloadURL
        self.prebuiltsRootCertPath = prebuiltsRootCertPath
        self.pruneDependencies = pruneDependencies
        self.traitConfiguration = traitConfiguration
    }

    /// Default instance of WorkspaceConfiguration
    public static var `default`: Self {
        .init(
            skipDependenciesUpdates: false,
            prefetchBasedOnResolvedFile: true,
            shouldCreateMultipleTestProducts: false,
            createREPLProduct: false,
            additionalFileRules: [],
            sharedDependenciesCacheEnabled: true,
            fingerprintCheckingMode: .strict,
            signingEntityCheckingMode: .warn,
            skipSignatureValidation: false,
            sourceControlToRegistryDependencyTransformation: nil,
            defaultRegistry: .none,
            manifestImportRestrictions: .none,
            usePrebuilts: false,
            prebuiltsDownloadURL: nil,
            prebuiltsRootCertPath: nil,
            pruneDependencies: false,
            traitConfiguration: .default
        )
    }

    public enum SourceControlToRegistryDependencyTransformation {
        case disabled
        case identity
        case swizzle
    }

    public enum CheckingMode: String {
        case strict
        case warn
    }
}

// MARK: - Deprecated 8/20201

extension Workspace {
    /// Manages a package workspace's configuration.
    // FIXME: change into enum after deprecation grace period
    public final class Configuration {}
}