/**
 * Audit Service — 审计日志服务（TOOL 层）
 *
 * 负责将工具调用、权限检查、错误等审计记录写入 SQLite audit_logs 表。
 * 设计原则：
 * 1. 所有重要操作必须记录
 * 2. 日志不可篡改（INSERT-ONLY）
 * 3. 支持按时间/类型/会话查询
 * 4. v0.2.0: 链式哈希防篡改 — 每条日志的 current_hash = SHA256(prev_hash + content)
 *
 * @see docs/MetonaAI-Desktop 架构与交互设计.html — 日志分层
 * @see docs/生产级通用 AI Agent 智能体桌面应用：完整设计与构建指南.html — 第十章
 */

import type Database from 'better-sqlite3';
import { createHash } from 'crypto';
import log from 'electron-log';

export type AuditEventType = 'tool_call' | 'permission_check' | 'error' | 'llm_request' | 'llm_response' | 'session_start' | 'session_end' | 'config_change';
export type AuditActor = 'agent' | 'user' | 'system';
export type AuditOutcome = 'success' | 'denied' | 'error';

export interface AuditEntry {
  sessionId: string;
  iteration?: number;
  eventType: AuditEventType;
  actor: AuditActor;
  target: string;
  details?: Record<string, unknown>;
  outcome?: AuditOutcome;
  durationMs?: number;
}

export class AuditService {
  constructor(private getDB: () => Database.Database) {}

  /**
   * 计算链式哈希
   * current_hash = SHA256(prev_hash + 所有内容字段)
   * v0.2.0: 纳入 iteration/outcome/durationMs 字段，使用 JSON.stringify 避免分隔符碰撞
   */
  private computeHash(
    prevHash: string,
    entry: {
      sessionId: string; iteration: number | null; eventType: string;
      actor: string; target: string; details: string | null;
      outcome: string | null; durationMs: number | null; createdAt: number;
    },
  ): string {
    // 使用 JSON.stringify 避免分隔符碰撞
    const content = JSON.stringify({
      prevHash,
      sessionId: entry.sessionId,
      iteration: entry.iteration,
      eventType: entry.eventType,
      actor: entry.actor,
      target: entry.target,
      details: entry.details,
      outcome: entry.outcome,
      durationMs: entry.durationMs,
      createdAt: entry.createdAt,
    });
    return createHash('sha256').update(content, 'utf-8').digest('hex');
  }

  /**
   * 获取最后一条日志的 hash（用于链式哈希计算）
   */
  private getLastHash(): string {
    const db = this.getDB();
    const row = db.prepare('SELECT current_hash FROM audit_logs ORDER BY id DESC LIMIT 1').get() as { current_hash: string | null } | undefined;
    return row?.current_hash ?? '0000000000000000000000000000000000000000000000000000000000000000';
  }

  /**
   * 记录审计条目（带链式哈希）
   */
  log(entry: AuditEntry): void {
    try {
      const db = this.getDB();
      const now = Date.now();
      const detailsStr = entry.details ? JSON.stringify(entry.details) : null;
      const prevHash = this.getLastHash();
      const currentHash = this.computeHash(prevHash, {
        sessionId: entry.sessionId,
        iteration: entry.iteration ?? null,
        eventType: entry.eventType,
        actor: entry.actor,
        target: entry.target,
        details: detailsStr,
        outcome: entry.outcome ?? null,
        durationMs: entry.durationMs ?? null,
        createdAt: now,
      });

      db.prepare(`
        INSERT INTO audit_logs (session_id, iteration, event_type, actor, target, details, outcome, duration_ms, created_at, prev_hash, current_hash)
        VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
      `).run(
        entry.sessionId,
        entry.iteration ?? null,
        entry.eventType,
        entry.actor,
        entry.target,
        detailsStr,
        entry.outcome ?? null,
        entry.durationMs ?? null,
        now,
        prevHash,
        currentHash,
      );
    } catch (error) {
      // 审计日志写入失败不应影响主流程
      log.error('Audit log write failed:', error);
    }
  }

  /**
   * 记录工具调用
   */
  logToolCall(params: {
    sessionId: string;
    iteration: number;
    toolName: string;
    args: Record<string, unknown>;
    outcome: AuditOutcome;
    result?: unknown;
    error?: string;
    durationMs: number;
  }): void {
    this.log({
      sessionId: params.sessionId,
      iteration: params.iteration,
      eventType: 'tool_call',
      actor: 'agent',
      target: params.toolName,
      details: {
        args: params.args,
        result: typeof params.result === 'string' ? params.result.slice(0, 1000) : params.result,
        error: params.error,
      },
      outcome: params.outcome,
      durationMs: params.durationMs,
    });
  }

  /**
   * 记录 LLM 请求
   */
  logLLMRequest(params: {
    sessionId: string;
    iteration: number;
    provider: string;
    model: string;
    tokenCount: number;
  }): void {
    this.log({
      sessionId: params.sessionId,
      iteration: params.iteration,
      eventType: 'llm_request',
      actor: 'agent',
      target: `${params.provider}/${params.model}`,
      details: { tokenCount: params.tokenCount },
    });
  }

  /**
   * 记录 LLM 响应
   */
  logLLMResponse(params: {
    sessionId: string;
    iteration: number;
    provider: string;
    model: string;
    tokenUsage: { input: number; output: number; total: number };
    durationMs: number;
  }): void {
    this.log({
      sessionId: params.sessionId,
      iteration: params.iteration,
      eventType: 'llm_response',
      actor: 'agent',
      target: `${params.provider}/${params.model}`,
      details: { tokenUsage: params.tokenUsage },
      outcome: 'success',
      durationMs: params.durationMs,
    });
  }

  /**
   * 记录会话开始
   */
  logSessionStart(sessionId: string): void {
    this.log({
      sessionId,
      eventType: 'session_start',
      actor: 'user',
      target: 'session',
    });
  }

  /**
   * 记录会话结束
   */
  logSessionEnd(params: {
    sessionId: string;
    totalIterations: number;
    totalTokens: number;
    durationMs: number;
    terminationReason: string;
  }): void {
    this.log({
      sessionId: params.sessionId,
      eventType: 'session_end',
      actor: 'agent',
      target: 'session',
      details: {
        totalIterations: params.totalIterations,
        totalTokens: params.totalTokens,
        terminationReason: params.terminationReason,
      },
      outcome: 'success',
      durationMs: params.durationMs,
    });
  }

  /**
   * 查询审计日志
   */
  query(filters?: {
    sessionId?: string;
    eventType?: AuditEventType;
    limit?: number;
  }): Array<{
    id: number;
    session_id: string;
    iteration: number | null;
    event_type: string;
    actor: string;
    target: string;
    details: string | null;
    outcome: string | null;
    duration_ms: number | null;
    created_at: number;
    prev_hash: string | null;
    current_hash: string | null;
  }> {
    const db = this.getDB();
    let sql = 'SELECT * FROM audit_logs WHERE 1=1';
    const params: unknown[] = [];

    if (filters?.sessionId) {
      sql += ' AND session_id = ?';
      params.push(filters.sessionId);
    }
    if (filters?.eventType) {
      sql += ' AND event_type = ?';
      params.push(filters.eventType);
    }

    sql += ' ORDER BY created_at DESC';

    if (filters?.limit) {
      sql += ' LIMIT ?';
      params.push(filters.limit);
    }

    return db.prepare(sql).all(...params) as Array<{
      id: number;
      session_id: string;
      iteration: number | null;
      event_type: string;
      actor: string;
      target: string;
      details: string | null;
      outcome: string | null;
      duration_ms: number | null;
      created_at: number;
      prev_hash: string | null;
      current_hash: string | null;
    }>;
  }

  /**
   * v0.2.0: 验证链式哈希完整性
   *
   * 遍历所有审计日志，重新计算每条记录的 hash，与存储的 current_hash 对比。
   * 如果任何一条记录的 hash 不匹配，说明日志已被篡改。
   *
   * @returns 验证结果，包括是否通过、首个篡改位置的 ID
   */
  verifyChain(): { valid: boolean; totalRecords: number; verifiedRecords: number; tamperedId: number | null } {
    const db = this.getDB();
    const rows = db.prepare('SELECT id, session_id, iteration, event_type, actor, target, details, outcome, duration_ms, created_at, prev_hash, current_hash FROM audit_logs ORDER BY id ASC').all() as Array<{
      id: number; session_id: string; iteration: number | null; event_type: string; actor: string;
      target: string; details: string | null; outcome: string | null; duration_ms: number | null;
      created_at: number; prev_hash: string | null; current_hash: string | null;
    }>;

    let prevHash = '0000000000000000000000000000000000000000000000000000000000000000';
    let verified = 0;

    for (const row of rows) {
      // 跳过旧数据（current_hash 为 NULL，未回填哈希）
      if (row.current_hash === null) {
        prevHash = '0'.repeat(64);
        continue;
      }

      const expectedHash = this.computeHash(prevHash, {
        sessionId: row.session_id,
        iteration: row.iteration,
        eventType: row.event_type,
        actor: row.actor,
        target: row.target,
        details: row.details,
        outcome: row.outcome,
        durationMs: row.duration_ms,
        createdAt: row.created_at,
      });

      if (row.current_hash !== expectedHash) {
        return { valid: false, totalRecords: rows.length, verifiedRecords: verified, tamperedId: row.id };
      }

      prevHash = row.current_hash;
      verified++;
    }

    return { valid: true, totalRecords: rows.length, verifiedRecords: verified, tamperedId: null };
  }
}