import { ProjectSession, ChatMessage, StageKey } from '../types/workbench';

/**
 * 私聊会话 ID 约定：sess-{projectKey}-u{userId}
 * 同一项目下，不同用户拥有完全独立的 session，互不可见。
 */
export function buildPrivateSessionId(projectKey: string, userId: number): string {
  return `sess-${projectKey}-u${userId}`;
}

export function filterSessionsForUser(
  sessions: ProjectSession[],
  userId: number
): ProjectSession[] {
  return sessions.filter((s) => s.userId === userId);
}

/**
 * 登录 / 切换用户后，解析应激活的私聊会话：
 * 1) 若当前 active 已属于该用户且该会话确有消息（或无更好候选）则保留
 * 2) 同 projectId 下优先选择「有消息」的私聊会话，避免落到 ensure 出来的空壳 sess-p{N}-u{id}
 * 3) 否则取该用户消息最多的会话 / 第一条会话
 */
export function resolveActiveSessionForUser(
  sessions: ProjectSession[],
  userId: number,
  preferredProjectId?: number,
  currentActiveId?: string,
  messageCounts?: Record<string, number>
): string {
  const mine = filterSessionsForUser(sessions, userId);
  if (mine.length === 0) return '';

  const countOf = (sessionId: string) =>
    messageCounts?.[sessionId] ??
    mine.find((s) => s.sessionId === sessionId)?.messageCount ??
    0;

  const rank = (a: ProjectSession, b: ProjectSession) => {
    const diff = countOf(b.sessionId) - countOf(a.sessionId);
    if (diff !== 0) return diff;
    // 同消息量时，优先非 ensure 生成的空壳 ID（sess-p数字-u）
    const aShell = /^sess-p\d+-u\d+$/.test(a.sessionId) ? 1 : 0;
    const bShell = /^sess-p\d+-u\d+$/.test(b.sessionId) ? 1 : 0;
    return aShell - bShell;
  };

  const pickBest = (candidates: ProjectSession[]) => {
    if (candidates.length === 0) return '';
    return [...candidates].sort(rank)[0].sessionId;
  };

  if (currentActiveId) {
    const current = mine.find((s) => s.sessionId === currentActiveId);
    if (current && countOf(currentActiveId) > 0) {
      return currentActiveId;
    }
  }

  if (preferredProjectId != null) {
    const sameProject = mine.filter((s) => s.projectId === preferredProjectId);
    const best = pickBest(sameProject);
    if (best) return best;
  }

  // 当前 active 若为空壳，改选同用户最佳会话
  return pickBest(mine);
}

/** 同一 (projectId, userId) 只保留一条：优先有消息 / 非空壳 ID 的会话 */
export function dedupePrivateSessions(
  sessions: ProjectSession[],
  messageCounts?: Record<string, number>
): ProjectSession[] {
  const groups = new Map<string, ProjectSession[]>();
  for (const s of sessions) {
    const key = `${s.projectId}:${s.userId}`;
    const list = groups.get(key) || [];
    list.push(s);
    groups.set(key, list);
  }
  const result: ProjectSession[] = [];
  for (const list of groups.values()) {
    if (list.length === 1) {
      result.push(list[0]);
      continue;
    }
    const countOf = (id: string) =>
      messageCounts?.[id] ?? list.find((s) => s.sessionId === id)?.messageCount ?? 0;
    list.sort((a, b) => {
      const diff = countOf(b.sessionId) - countOf(a.sessionId);
      if (diff !== 0) return diff;
      const aShell = /^sess-p\d+-u\d+$/.test(a.sessionId) ? 1 : 0;
      const bShell = /^sess-p\d+-u\d+$/.test(b.sessionId) ? 1 : 0;
      return aShell - bShell;
    });
    result.push(list[0]);
  }
  return result;
}

/** 确保用户对每个已知项目都有独立私聊会话（无则克隆项目元数据新建空会话） */
export function ensurePrivateSessionsForUser(
  sessions: ProjectSession[],
  userId: number
): ProjectSession[] {
  const byProject = new Map<number, ProjectSession>();
  for (const s of sessions) {
    if (!byProject.has(s.projectId)) {
      byProject.set(s.projectId, s);
    }
  }
  const result = [...sessions];
  for (const [projectId, template] of byProject) {
    const exists = result.some((s) => s.projectId === projectId && s.userId === userId);
    if (!exists) {
      // 优先复用已知项目短名，避免与默认 sess-cusa-u* 并存两套空壳
      const projectKey =
        projectId === 3
          ? 'cusa'
          : projectId === 1
            ? 'endo'
            : projectId === 2
              ? 'ultrasound'
              : projectId === 5201
                ? 'neuropulse'
                : projectId === 6001
                  ? 'wangjing'
                  : projectId === 6002
                    ? 'tianzhihang'
                    : projectId === 6003
                      ? 'xunzun'
                      : projectId === 6004
                        ? 'xianghejie'
                        : projectId === 6005
                          ? 'yamui'
                          : projectId === 6006
                            ? 'ziyanar'
                            : projectId === 6007
                              ? 'lanting'
                              : projectId === 6008
                                ? 'dengyizi'
                                : projectId === 6009
                                  ? 'chongjibo'
                                  : projectId === 6010
                                    ? 'jigu'
                                    : `p${projectId}`;
      result.push({
        sessionId: buildPrivateSessionId(projectKey, userId),
        userId,
        projectId,
        title: template.title,
        deviceType: template.deviceType,
        stage: template.stage as StageKey,
        stageLabel: template.stageLabel,
        messageCount: 0,
        updatedAt: '刚刚',
      });
    }
  }
  return dedupePrivateSessions(result);
}

/** 断言：任意消息不得跨用户 session 泄漏 */
export function assertNoCrossUserChatLeak(
  sessions: ProjectSession[],
  messages: ChatMessage[]
): { ok: boolean; leaks: string[] } {
  const sessionOwner = new Map(sessions.map((s) => [s.sessionId, s.userId]));
  const leaks: string[] = [];
  for (const m of messages) {
    const owner = sessionOwner.get(m.sessionId);
    if (owner == null) continue;
    if (m.role === 'user' && m.authorName) {
      const otherOwners = sessions.filter((s) => s.userId !== owner);
      for (const o of otherOwners) {
        const otherName = guessUserNameById(o.userId);
        if (otherName && m.authorName === otherName) {
          leaks.push(
            `session=${m.sessionId} ownerUserId=${owner} 含异主用户发言 author=${m.authorName}`
          );
        }
      }
    }
  }
  return { ok: leaks.length === 0, leaks };
}

function guessUserNameById(userId?: number): string | null {
  if (userId === 2) return '张工';
  if (userId === 3) return '李主管';
  if (userId === 4) return '王总监';
  return null;
}