/**
 * SYNC 副本（demo 不抽共享包；改站内源请同步本文件）：
 * client/src/shared/cross/semanticUtils.ts → splitTextToChunks 及相关纯函数
 */
globalThis.IL_splitTextToChunks = (function () {
  const encoder = new TextEncoder();

  function getUtf8ByteLength(text, buf) {
    const { read, written } = encoder.encodeInto(text, buf);
    return read < text.length ? buf.length : written;
  }

  function nextParagraphEnd(text, start) {
    const nl = text.indexOf('\n\n', start);
    if (nl === -1) return text.length;
    let end = nl + 2;
    while (end < text.length && text[end] === '\n') end++;
    return end;
  }

  function nextLineEnd(text, start) {
    const nl = text.indexOf('\n', start);
    if (nl === -1) return text.length;
    let end = nl + 1;
    while (end < text.length && text[end] === '\n') end++;
    return end;
  }

  function charIndexForByteLimit(text, start, byteLimit) {
    const buf = new Uint8Array(4);
    let bytes = 0;
    let i = start;
    while (i < text.length) {
      const cp = text.codePointAt(i);
      const charLen = cp > 0xffff ? 2 : 1;
      const byteLen = encoder.encodeInto(text.slice(i, i + charLen), buf).written;
      if (bytes + byteLen > byteLimit) break;
      bytes += byteLen;
      i += charLen;
    }
    return i;
  }

  const SEPARATOR_GROUPS = [
    ['。', '！', '？', '…'],
    ['；', '，'],
    ['.', '!', '?'],
    [';', ','],
    [' ', '\t'],
  ];

  function findSplitPoint(text, start, maxEnd) {
    const window = text.slice(start, maxEnd);
    for (const group of SEPARATOR_GROUPS) {
      let bestEnd = -1;
      for (const sep of group) {
        const i = window.lastIndexOf(sep);
        if (i !== -1 && i + sep.length > bestEnd) bestEnd = i + sep.length;
      }
      if (bestEnd !== -1) return start + bestEnd;
    }
    return maxEnd;
  }

  /** @returns {{ text: string, startOffset: number }[]} */
  function splitTextToChunks(text, bytesPerChunk) {
    if (bytesPerChunk <= 0) {
      throw new Error('bytesPerChunk must be > 0, got: ' + bytesPerChunk);
    }
    if (text.includes('\r')) {
      throw new Error('Text contains \\r (CR); only \\n (LF) is supported.');
    }
    const chunks = [];
    let pos = 0;
    const encodeBuf = new Uint8Array(bytesPerChunk + 1);
    while (pos < text.length) {
      let chunkEnd = pos;
      let chunkBytes = 0;
      outer: while (chunkEnd < text.length) {
        const paragEnd = nextParagraphEnd(text, chunkEnd);
        const paragBytes = getUtf8ByteLength(text.slice(chunkEnd, paragEnd), encodeBuf);
        if (chunkBytes > 0 && chunkBytes + paragBytes > bytesPerChunk) break;
        if (chunkBytes === 0 && paragBytes > bytesPerChunk) {
          while (chunkEnd < paragEnd) {
            const lineEnd = nextLineEnd(text, chunkEnd);
            const lineBytes = getUtf8ByteLength(text.slice(chunkEnd, lineEnd), encodeBuf);
            if (lineBytes > bytesPerChunk) {
              const maxEnd = charIndexForByteLimit(text, chunkEnd, bytesPerChunk);
              chunkEnd = findSplitPoint(text, chunkEnd, maxEnd);
              break outer;
            }
            if (chunkBytes > 0 && chunkBytes + lineBytes > bytesPerChunk) break outer;
            chunkBytes += lineBytes;
            chunkEnd = lineEnd;
          }
          continue outer;
        }
        chunkBytes += paragBytes;
        chunkEnd = paragEnd;
      }
      chunks.push({ text: text.slice(pos, chunkEnd), startOffset: pos });
      pos = chunkEnd;
    }
    return chunks;
  }

  return splitTextToChunks;
})();