/** Session actions are broader than one fixed reset phrase. */
export const WECHAT_SESSION_ACTION = Object.freeze({
  CONTINUE: 'continue',
  RESET: 'reset',
  IGNORE_PREVIOUS: 'ignore_previous',
  UNCLEAR: 'unclear',
});

const RESET_VERBS = /(?:换|开|新建|开启|开始|另起|重新|从头|清空|作废)/u;
const RESET_TARGETS = /(?:新?会话|对话|聊天|上下文|话题|主题)/u;
const CONTEXT_REFERENCES = /(?:之前|刚才|前面|上面|当前|这个|刚刚)/u;
const IGNORE_VERBS = /(?:忽略|不要管|别管|不参考|不要参考|不用参考|忘掉|忘记)/u;
const CONTINUE_VERBS = /(?:继续|接着|还是|回到|沿着)/u;
const SESSION_SEMANTIC_HINT = /(?:换个思路|另一个话题|不同话题|重置|清除|忘记刚才|刚才.*不要|从现在开始)/u;

function normalizeText(text) {
  return String(text ?? '')
    .trim()
    .replace(/[\u200b-\u200d\ufeff]/g, '')
    .replace(/[\s，。！？、；：“”‘’（）()【】\[\]{}]+/gu, '');
}

function classifyByMeaning(text) {
  const normalized = normalizeText(text);
  if (!normalized) return { action: WECHAT_SESSION_ACTION.UNCLEAR, confidence: 0 };

  const hasTarget = RESET_TARGETS.test(normalized);
  const hasContext = CONTEXT_REFERENCES.test(normalized);
  const hasResetVerb = RESET_VERBS.test(normalized);
  const hasIgnoreVerb = IGNORE_VERBS.test(normalized);
  const hasContinueVerb = CONTINUE_VERBS.test(normalized);

  if (hasContinueVerb && hasTarget && !hasResetVerb) {
    return { action: WECHAT_SESSION_ACTION.CONTINUE, confidence: 0.94, source: 'semantic_rules' };
  }
  if (hasIgnoreVerb && (hasContext || hasTarget) && !/(?:新|重新|另起|开启|开始)/u.test(normalized)) {
    return { action: WECHAT_SESSION_ACTION.IGNORE_PREVIOUS, confidence: 0.9, source: 'semantic_rules' };
  }
  if ((hasResetVerb && hasTarget) || /(?:重新开始|从头来|重来一次|另开一个)/u.test(normalized)) {
    return { action: WECHAT_SESSION_ACTION.RESET, confidence: 0.98, source: 'semantic_rules' };
  }
  return { action: WECHAT_SESSION_ACTION.UNCLEAR, confidence: 0.35, source: 'fallback' };
}

function normalizeSemanticResult(result) {
  if (!result) return null;
  const raw = String(result.action ?? result.intent ?? result.label ?? '').trim().toLowerCase();
  const aliases = {
    'session.reset': WECHAT_SESSION_ACTION.RESET,
    reset: WECHAT_SESSION_ACTION.RESET,
    new_session: WECHAT_SESSION_ACTION.RESET,
    continue: WECHAT_SESSION_ACTION.CONTINUE,
    reuse: WECHAT_SESSION_ACTION.CONTINUE,
    ignore_previous: WECHAT_SESSION_ACTION.IGNORE_PREVIOUS,
    ignore: WECHAT_SESSION_ACTION.IGNORE_PREVIOUS,
    unclear: WECHAT_SESSION_ACTION.UNCLEAR,
  };
  const action = aliases[raw];
  if (!action) return null;
  return {
    action,
    confidence: Number.isFinite(Number(result.confidence)) ? Number(result.confidence) : 0.7,
    source: 'semantic_model',
    reason: String(result.reason ?? '').trim() || null,
  };
}

/**
 * Resolve a session action. A channel may inject a small semantic model for
 * ambiguous phrases; the meaning-based fallback keeps this path safe when the
 * model is unavailable or times out.
 */
export async function resolveWechatSessionAction(text, { semanticClassifier = null, logger = console } = {}) {
  const deterministic = classifyByMeaning(text);
  if (deterministic.action !== WECHAT_SESSION_ACTION.UNCLEAR) return deterministic;
  if (typeof semanticClassifier !== 'function') return deterministic;
  const normalized = normalizeText(text);
  if (!RESET_TARGETS.test(normalized) && !CONTEXT_REFERENCES.test(normalized) && !SESSION_SEMANTIC_HINT.test(normalized)) {
    return deterministic;
  }
  try {
    const semantic = normalizeSemanticResult(await semanticClassifier({
      text: String(text ?? '').trim(),
      actions: Object.values(WECHAT_SESSION_ACTION),
    }));
    if (semantic) return semantic;
  } catch (err) {
    logger?.warn?.('[wechat-session-intent] semantic classifier failed:', err);
  }
  return deterministic;
}

export function isWechatSessionResetAction(result) {
  return result?.action === WECHAT_SESSION_ACTION.RESET;
}