ShadowsocksX-NG/ShadowsocksX-NG2/Domain/CatalogFileStore.swift

import Foundation

/// 配置树磁盘持久化（spec #21 D5）：落盘 `~/Library/Application Support/
/// ShadowsocksX-NG2/catalog.json`，目录权限 0700、文件 0600；写临时文件
/// （创建即 0600）后原子替换。文件只含结构化目录、凭据引用与订阅元数据
/// （URL 仍是凭据引用），永不落秘密明文。
struct CatalogFileStore {
  enum PersistenceError: Error, Equatable {
    /// 文件存在但不是本模型可接受的目录文档：JSON 损坏、版本未知、结构不一致。
    case corrupt(detail: String)
    /// 读取或写入时的文件系统错误。
    case ioFailure(detail: String)
  }

  /// v2 起携带订阅记录；v1（无订阅字段）仍可读取。v3 移除节点级 enabled
  /// 语义；v4 把订阅失败字符串替换为 typed facts。读取兼容 v1–v4，写入
  /// 始终使用 v4。
  private static let supportedVersions: Set<Int> = [1, 2, 3, 4]
  private static let currentVersion = 4
  private static let jsonEncoder: JSONEncoder = {
    let encoder = JSONEncoder()
    encoder.outputFormatting = [.prettyPrinted, .sortedKeys]
    return encoder
  }()

  let fileURL: URL

  /// 默认位置：`~/Library/Application Support/ShadowsocksX-NG2/catalog.json`。
  static func defaultFileURL() -> URL {
    let support = FileManager.default.urls(for: .applicationSupportDirectory, in: .userDomainMask)[
      0]
    return support.appendingPathComponent("ShadowsocksX-NG2/catalog.json")
  }

  /// 文件缺失 → 全新空文档；存在但损坏/版本未知/结构不一致 → `.corrupt`。
  func load() throws -> CatalogDocument {
    guard FileManager.default.fileExists(atPath: fileURL.path) else {
      return CatalogDocument()
    }
    let data: Data
    do {
      data = try Data(contentsOf: fileURL)
    } catch {
      throw PersistenceError.ioFailure(detail: String(describing: error))
    }
    return try decode(data)
  }

  /// 整体重写并原子替换；失败时保留原文件。目录按 D5 基线强制 0700（含自愈）。
  func save(_ document: CatalogDocument) throws {
    let payload = CatalogFilePayload(
      version: Self.currentVersion,
      rootChildren: document.catalog.rootChildren,
      entries: document.catalog.entries.values.sorted { $0.id.rawValue < $1.id.rawValue },
      subscriptions: document.subscriptions)
    let data: Data
    do {
      data = try Self.jsonEncoder.encode(payload)
    } catch {
      throw PersistenceError.ioFailure(detail: String(describing: error))
    }
    do {
      try AtomicFileWriter.write(data, to: fileURL)
    } catch {
      throw PersistenceError.ioFailure(detail: String(describing: error))
    }
  }

  private func decode(_ data: Data) throws -> CatalogDocument {
    let payload: CatalogFilePayload
    do {
      payload = try JSONDecoder().decode(CatalogFilePayload.self, from: data)
    } catch {
      throw PersistenceError.corrupt(detail: String(describing: error))
    }
    guard Self.supportedVersions.contains(payload.version) else {
      throw PersistenceError.corrupt(detail: "unsupported version \(payload.version)")
    }
    var entries: [NodeID: CatalogEntry] = [:]
    for entry in payload.entries {
      guard entries[entry.id] == nil else {
        throw PersistenceError.corrupt(detail: "duplicate node id \(entry.id.rawValue)")
      }
      entries[entry.id] = entry
    }
    let catalog: ConfigurationCatalog
    do {
      catalog = try ConfigurationCatalog.validated(
        rootChildren: payload.rootChildren, entries: entries)
    } catch let error as CatalogError {
      throw PersistenceError.corrupt(detail: String(describing: error))
    }
    let subscriptions = payload.subscriptions ?? []
    var seen = Set<NodeID>()
    for record in subscriptions {
      guard seen.insert(record.id).inserted else {
        throw PersistenceError.corrupt(detail: "duplicate subscription \(record.id.rawValue)")
      }
    }
    // 订阅固定分组必须存在于目录且来源正确；缺失即文档不一致。
    for record in subscriptions {
      guard
        let entry = catalog.entry(for: record.groupID), case .group = entry.kind,
        entry.source == .subscription
      else {
        throw PersistenceError.corrupt(
          detail: "subscription group missing \(record.groupID.rawValue)")
      }
    }
    return CatalogDocument(catalog: catalog, subscriptions: subscriptions)
  }
}

/// 落盘文档形态：版本号 + 根子序 + 全量节点表（顺序语义在根序与分组显子序中）
/// + 订阅记录（v2 起携带；v1 缺省为空）。v3 节点条目不再写出 `enabled`；
/// v4 的失败状态只写 typed facts，不再写旧 `reason` 字段。
private struct CatalogFilePayload: Codable {
  var version: Int
  var rootChildren: [NodeID]
  var entries: [CatalogEntry]
  var subscriptions: [SubscriptionRecord]?
}