/**
 * API Fallbacks for ZCLAW Gateway
 *
 * Provides sensible default data when ZCLAW API endpoints return 404.
 * This allows the UI to function gracefully even when backend features
 * are not yet implemented.
 */

// === Types ===

export interface QuickConfigFallback {
  agentName: string;
  agentRole: string;
  userName: string;
  userRole: string;
  agentNickname?: string;
  scenarios?: string[];
  workspaceDir?: string;
  gatewayUrl?: string;
  gatewayToken?: string;
  skillsExtraDirs?: string[];
  mcpServices?: Array<{ id: string; name: string; enabled: boolean }>;
  theme: 'light' | 'dark';
  autoStart?: boolean;
  showToolCalls: boolean;
  restrictFiles?: boolean;
  autoSaveContext?: boolean;
  fileWatching?: boolean;
  privacyOptIn?: boolean;
}

export interface WorkspaceInfoFallback {
  path: string;
  resolvedPath: string;
  exists: boolean;
  fileCount: number;
  totalSize: number;
}

export interface UsageStatsFallback {
  totalSessions: number;
  totalMessages: number;
  totalTokens: number;
  byModel: Record<string, { messages: number; inputTokens: number; outputTokens: number }>;
}

export interface PluginStatusFallback {
  id: string;
  name?: string;
  status: 'active' | 'inactive' | 'error' | 'loading';
  version?: string;
  description?: string;
}

export interface ScheduledTaskFallback {
  id: string;
  name: string;
  schedule: string;
  status: 'active' | 'paused' | 'completed' | 'error';
  lastRun?: string;
  nextRun?: string;
  description?: string;
}

export interface SecurityLayerFallback {
  name: string;
  enabled: boolean;
  description?: string;
}

export interface SecurityStatusFallback {
  _isFallback?: true;
  layers: SecurityLayerFallback[];
  enabledCount: number;
  totalCount: number;
  securityLevel: 'critical' | 'high' | 'medium' | 'low';
}

// Session type for usage calculation
interface SessionForStats {
  id: string;
  messageCount?: number;
  metadata?: {
    tokens?: { input?: number; output?: number };
    model?: string;
  };
}

// Skill type for plugin fallback
interface SkillForPlugins {
  id: string;
  name: string;
  source: 'builtin' | 'extra';
  enabled?: boolean;
  description?: string;
}

// Trigger type for scheduled tasks
interface TriggerForTasks {
  id: string;
  type: string;
  enabled: boolean;
}

// === Fallback Implementations ===

/**
 * Default quick config when /api/config/quick returns 404.
 * Uses sensible defaults for a new user experience.
 */
export function getQuickConfigFallback(): QuickConfigFallback & { _isFallback: true } {
  console.warn('[fallback] 使用降级数据: getQuickConfigFallback');
  return {
    _isFallback: true as const,
    agentName: '默认助手',
    agentRole: 'AI 助手',
    userName: '用户',
    userRole: '用户',
    agentNickname: 'ZCLAW',
    scenarios: ['通用对话', '代码助手', '文档编写'],
    theme: 'dark',
    showToolCalls: true,
    autoSaveContext: true,
    fileWatching: true,
    privacyOptIn: false,
  };
}

/**
 * Default workspace info when /api/workspace returns 404.
 * Returns a placeholder indicating workspace is not configured.
 */
export function getWorkspaceInfoFallback(): WorkspaceInfoFallback & { _isFallback: true } {
  console.warn('[fallback] 使用降级数据: getWorkspaceInfoFallback');
  // Try to get a reasonable default path
  const defaultPath = typeof window !== 'undefined'
    ? `${navigator.userAgent.includes('Windows') ? 'C:\\Users' : '/home'}/workspace`
    : '/workspace';

  return {
    _isFallback: true as const,
    path: defaultPath,
    resolvedPath: defaultPath,
    exists: false,
    fileCount: 0,
    totalSize: 0,
  };
}

/**
 * Calculate usage stats from session data when /api/stats/usage returns 404.
 */
export function getUsageStatsFallback(sessions: SessionForStats[] = []): UsageStatsFallback & { _isFallback: true } {
  console.warn('[fallback] 使用降级数据: getUsageStatsFallback — 基于本地 session 数据计算');
  const stats: UsageStatsFallback = {
    totalSessions: sessions.length,
    totalMessages: 0,
    totalTokens: 0,
    byModel: {},
  };

  for (const session of sessions) {
    stats.totalMessages += session.messageCount || 0;

    if (session.metadata?.tokens) {
      const input = session.metadata.tokens.input || 0;
      const output = session.metadata.tokens.output || 0;
      stats.totalTokens += input + output;

      if (session.metadata.model) {
        const model = session.metadata.model;
        if (!stats.byModel[model]) {
          stats.byModel[model] = { messages: 0, inputTokens: 0, outputTokens: 0 };
        }
        stats.byModel[model].messages += session.messageCount || 0;
        stats.byModel[model].inputTokens += input;
        stats.byModel[model].outputTokens += output;
      }
    }
  }

  return { ...stats, _isFallback: true as const };
}

/**
 * Convert skills to plugin status when /api/plugins/status returns 404.
 * ZCLAW uses Skills instead of traditional plugins.
 */
export function getPluginStatusFallback(skills: SkillForPlugins[] = []): Array<PluginStatusFallback & { _isFallback?: true }> {
  console.warn('[fallback] 使用降级数据: getPluginStatusFallback — 从 Skills 列表推断');
  if (skills.length === 0) {
    // No skills loaded — return empty rather than fabricating fake builtins
    return [];
  }

  return skills.map((skill) => ({
    id: skill.id,
    name: skill.name,
    status: skill.enabled !== false ? 'active' : 'inactive',
    description: skill.description,
  }));
}

/**
 * Convert triggers to scheduled tasks when /api/scheduler/tasks returns 404.
 */
export function getScheduledTasksFallback(triggers: TriggerForTasks[] = []): Array<ScheduledTaskFallback & { _isFallback?: true }> {
  console.warn('[fallback] 使用降级数据: getScheduledTasksFallback — 从 Triggers 列表推断');
  return triggers
    .filter((t) => t.enabled)
    .map((trigger) => ({
      id: trigger.id,
      name: `Trigger: ${trigger.type}`,
      schedule: 'event-based',
      status: 'active' as const,
      description: `Event trigger of type: ${trigger.type}`,
    }));
}

/**
 * Default security status when /api/security/status returns 404.
 * Returns honest minimal response — only includes layers that correspond
 * to real ZCLAW capabilities, no fabricated layers.
 */
export function getSecurityStatusFallback(): SecurityStatusFallback & { _isFallback: true } {
  console.warn('[fallback] 使用降级数据: getSecurityStatusFallback — 返回静态安全层状态');
  const layers: SecurityLayerFallback[] = [
    { name: 'device_auth', enabled: true, description: '设备认证' },
    { name: 'rbac', enabled: true, description: '角色权限控制' },
    { name: 'audit_log', enabled: true, description: '审计日志' },
    { name: 'approval_gate', enabled: true, description: '操作审批门' },
    { name: 'input_validation', enabled: true, description: '输入验证' },
    { name: 'secret_storage', enabled: true, description: '密钥安全存储 (OS keyring)' },
  ];

  const enabledCount = layers.filter((l) => l.enabled).length;
  const securityLevel = calculateSecurityLevel(enabledCount, layers.length);

  return {
    _isFallback: true as const,
    layers,
    enabledCount,
    totalCount: layers.length,
    securityLevel,
  };
}

/**
 * Calculate security level based on enabled layers ratio.
 */
function calculateSecurityLevel(enabledCount: number, totalCount: number): 'critical' | 'high' | 'medium' | 'low' {
  if (totalCount === 0) return 'low';
  const ratio = enabledCount / totalCount;
  if (ratio >= 0.875) return 'critical'; // 14-16 layers
  if (ratio >= 0.625) return 'high';     // 10-13 layers
  if (ratio >= 0.375) return 'medium';   // 6-9 layers
  return 'low';                          // 0-5 layers
}

// === Error Detection Helpers ===

/**
 * Check if an error is a 404 Not Found response.
 */
export function isNotFoundError(error: unknown): boolean {
  if (error instanceof Error) {
    const message = error.message.toLowerCase();
    return message.includes('404') || message.includes('not found');
  }
  if (typeof error === 'object' && error !== null) {
    const status = (error as { status?: number }).status;
    return status === 404;
  }
  return false;
}

/**
 * Check if an error is a network/connection error.
 */
export function isNetworkError(error: unknown): boolean {
  if (error instanceof Error) {
    const message = error.message.toLowerCase();
    return (
      message.includes('network') ||
      message.includes('connection') ||
      message.includes('timeout') ||
      message.includes('abort')
    );
  }
  return false;
}