/**
 * 会话存储（A1 阶段内存实现）。
 *
 * ADR-0003：个人会话只读，写操作必须在项目会话内——这里在创建时就把住：
 * scope=project 必须带 projectId，scope=personal 不允许带。
 * A3.7 落库后换成持久层；主键按 ADR-0007 用应用侧生成。
 */
import { randomUUID } from 'node:crypto';

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

import { badRequest, notFound } from './errors.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;
  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>();

  create(input: CreateSessionInput): 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,
      messages: [],
      bus: new EventBus(),
      state: 'idle',
      runs: new Map(),
      accepted: new Map(),
    };
    this.sessions.set(summary.sessionId, record);
    return record;
  }

  get(sessionId: string): SessionRecord | undefined {
    return this.sessions.get(sessionId);
  }

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

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