/**
 * 会话存储（A3.7：内存态 + SQLite 持久化）。
 *
 * - 持久部分（会话、消息、幂等键）写进 SQLite：重启后仍可查（ADR-0007）
 * - 运行态部分（事件总线、进行中的运行）留在内存：进程重启后由平台历史恢复（架构设计 5.1）
 * ADR-0003：个人会话只读，写操作必须在项目会话内——创建时就把住。
 */
import { randomUUID } from 'node:crypto';

import type { ChatMessage, SessionSummary } from '@aps/contracts';

import type { SessionRepository } from '../core/storage/sessions.js';
import { badRequest, notFound } from './errors.js';
import type { Subject } from './subject.js';
import { EventBus } from './events.js';

export type RunState = 'idle' | 'running' | 'cancelling' | 'cancelled';

export interface RunHandle {
  runId: string;
  abort: AbortController;
}

export interface SessionRecord {
  summary: SessionSummary;
  /** 会话归属者：引擎回调时的身份来源（ADR-0003：写操作必须在项目会话内） */
  owner: Subject;
  messages: ChatMessage[];
  bus: EventBus;
  state: RunState;
  runs: Map<string, RunHandle>;
  /** 幂等键 → 已受理的消息与运行（同一 key 重试不产生第二个 run） */
  accepted: Map<string, { messageId: string; runId: string }>;
}

export interface CreateSessionInput {
  scope: 'personal' | 'project';
  projectId?: string | undefined;
  title?: string | undefined;
}

export function newId(prefix: string): string {
  return `${prefix}-${randomUUID()}`;
}

export class SessionStore {
  private readonly sessions = new Map<string, SessionRecord>();

  constructor(private readonly repository?: SessionRepository) {}

  create(input: CreateSessionInput, owner: Subject): SessionRecord {
    if (input.scope === 'project' && !input.projectId) throw badRequest('项目会话必须带 projectId（ADR-0003）');
    if (input.scope === 'personal' && input.projectId) throw badRequest('个人会话不能带 projectId');

    const summary: SessionSummary = {
      sessionId: newId('s'),
      projectId: input.scope === 'project' ? (input.projectId ?? null) : null,
      scope: input.scope,
      status: 'active',
      title: input.title ?? (input.scope === 'project' ? '新会话' : '个人会话'),
      createdAt: Date.now(),
    };
    const record: SessionRecord = {
      summary,
      owner,
      messages: [],
      bus: new EventBus(),
      state: 'idle',
      runs: new Map(),
      accepted: new Map(),
    };
    this.sessions.set(summary.sessionId, record);
    this.repository?.insertSession({ ...summary, owner });
    return record;
  }

  get(sessionId: string): SessionRecord | undefined {
    const cached = this.sessions.get(sessionId);
    if (cached) return cached;
    // 进程重启后按库里的记录“补建”运行态：历史与归属都从存储恢复
    const stored = this.repository?.getSession(sessionId);
    if (!stored) return undefined;
    const { owner, ...summary } = stored;
    const record: SessionRecord = {
      summary,
      owner,
      messages: this.repository?.listMessages(sessionId) ?? [],
      bus: new EventBus(),
      state: 'idle',
      runs: new Map(),
      accepted: new Map(),
    };
    this.sessions.set(sessionId, record);
    return record;
  }

  /** 追加消息：内存与库一起写 */
  appendMessage(sessionId: string, message: ChatMessage): void {
    const record = this.require(sessionId);
    record.messages.push(message);
    this.repository?.appendMessage(sessionId, message);
  }

  /** 幂等键：受理时记录，重试与重启后都能命中 */
  rememberIdempotencyKey(sessionId: string, key: string, messageId: string, runId: string): void {
    this.require(sessionId).accepted.set(key, { messageId, runId });
    this.repository?.rememberIdempotencyKey(key, sessionId, messageId, runId);
  }

  findIdempotencyKey(sessionId: string, key: string): { messageId: string; runId: string } | undefined {
    const cached = this.require(sessionId).accepted.get(key);
    if (cached) return cached;
    const stored = this.repository?.findByIdempotencyKey(key);
    if (stored && stored.sessionId === sessionId) {
      const value = { messageId: stored.messageId, runId: stored.runId };
      this.require(sessionId).accepted.set(key, value);
      return value;
    }
    return undefined;
  }

  require(sessionId: string): SessionRecord {
    const record = this.get(sessionId);
    if (!record) throw notFound(`会话 ${sessionId}`);
    return record;
  }

  list(projectId?: string): SessionSummary[] {
    if (this.repository) {
      return this.repository.listSessions(projectId).map(({ owner: _owner, ...summary }) => summary);
    }
    return [...this.sessions.values()]
      .filter((record) => (projectId ? record.summary.projectId === projectId : true))
      .map((record) => record.summary)
      .sort((a, b) => b.createdAt - a.createdAt);
  }
}