/**
 * Pass 2 public thinking is a complete product sentence, never a CoT fragment.
 * This gate only accepts or rejects. It must not rewrite, strip, or splice.
 */
const CJK_RE = /[\u4e00-\u9fff]/;
const SENTENCE_RE = /[。！？]/;

export const THINK_STEP_TEXT_MIN = 8;
export const THINK_STEP_TEXT_MAX = 400;

export function acceptThinkStepText(text: string): string | null {
  const trimmed = text.replace(/\s+/g, " ").trim();
  if (trimmed.length < THINK_STEP_TEXT_MIN || trimmed.length > THINK_STEP_TEXT_MAX) return null;
  if (!CJK_RE.test(trimmed)) return null;
  if (!SENTENCE_RE.test(trimmed)) return null;
  return trimmed;
}

const TOOLISH_FRAGMENT_RE = /(?:rectification|run-jyotish)-[a-z0-9-]+|skill_read|proposedKind|validationErrors/i;

/**
 * Rectification still publishes reasoning as fragments. This gate only accepts
 * or rejects a chunk. It does not rewrite, strip English, or require 8 chars.
 */
export function acceptThinkingFragment(text: string): string | null {
  const trimmed = text.replace(/\s+/g, " ").trim();
  if (!trimmed) return null;
  if (!CJK_RE.test(trimmed)) return null;
  if (TOOLISH_FRAGMENT_RE.test(trimmed)) return null;
  return trimmed;
}

export function createThinkingFragmentAssembler() {
  let buffer = "";
  return {
    push(chunk: string): string | null {
      const accepted = acceptThinkingFragment(chunk);
      if (!accepted) return null;
      buffer += accepted;
      if (!SENTENCE_RE.test(buffer)) return null;
      const released = buffer;
      buffer = "";
      return released;
    },
    flush(): string | null {
      const leftover = buffer;
      buffer = "";
      return leftover ? acceptThinkingFragment(leftover) : null;
    },
  };
}