/**
 * 路线变更记录内容解析
 *
 * 存储格式（单行）：
 *   YD-20260904-0022：发货地 A → B；到货地 C → D；YD-20260904-0025：发货地 E → F；到货地 G → H
 *   路线顺序：A → B → C 调整为 B → A → C
 *
 * 解析结果（分组，供变更记录列表按「分组标题 - 字段 - 变更前/后」渲染）：
 *   [
 *     {
 *       title: 'YD-20260904-0022',
 *       text: '',
 *       fields: [{ label: '发货地', before: 'A', after: 'B', single: 'B', changed: true, unchanged: false }],
 *     },
 *     { title: '', text: '无法识别的原文', fields: [] },
 *   ]
 *
 * 说明：仅用于展示层，不改变已存储的 content 文本（历史数据同样适用）。
 */
// 长标签必须排在短标签前（「发货地址」优先于「发货地」），否则会被前缀吃掉
const FIELD_LABELS = ['发货地址', '到货地址', '发货地', '到货地', '装货地', '卸货地', '收货地'];
const FIELD_LABEL_PATTERN = new RegExp(`^(${FIELD_LABELS.join('|')})\\s*([\\s\\S]*)$`);
// 变更前 / 变更后分隔符：→、➔、➜、->、-->、–>、—>
const ARROW_PATTERN = /\s*(?:→|➔|➜|[\-–—]{1,2}\s*>)\s*/;
// 运单地址之外的变更描述，例如「A → B → C 调整为 B → A → C」
const ADJUST_PATTERN = /^([\s\S]*?)\s调整为\s*([\s\S]*)$/;
const EMPTY_TEXT = ['', '-', '--', '—', 'null', 'undefined'];
// 冒号前内容超过该长度时不视为分组标题（运单号通常长于该值）
const TITLE_MAX_LENGTH = 12;

const normalizeValue = value => {
  const text = String(value === undefined || value === null ? '' : value).trim();
  return EMPTY_TEXT.includes(text.toLowerCase()) ? '-' : text;
};

const buildField = (label, rawValue) => {
  const value = String(rawValue === undefined || rawValue === null ? '' : rawValue).trim();
  const adjustMatched = value.match(ADJUST_PATTERN);
  let before = value;
  let after = '';
  let hasPair = false;

  if (adjustMatched) {
    before = adjustMatched[1];
    after = adjustMatched[2];
    hasPair = true;
  } else {
    const parts = value.split(ARROW_PATTERN);
    if (parts.length > 1) {
      before = parts[0];
      after = parts[1];
      hasPair = true;
    }
  }

  const beforeText = normalizeValue(before);
  const afterText = normalizeValue(after);

  return {
    label,
    before: beforeText,
    after: afterText,
    // 单值展示（未拆分出前后值时使用）
    single: hasPair ? afterText : beforeText,
    changed: hasPair && beforeText !== afterText,
    unchanged: hasPair && beforeText === afterText,
  };
};

const parseSegment = segment => {
  // 形如「发货地 A → B」（前面只有「；」分隔，无分组标题）→ 归入上一条运单
  const leadingMatched = segment.match(FIELD_LABEL_PATTERN);
  if (leadingMatched && leadingMatched[2].trim()) {
    return {
      type: 'field',
      title: '',
      text: '',
      fields: [buildField(leadingMatched[1], leadingMatched[2])],
    };
  }

  const colonIndex = segment.search(/[：:]/);
  if (colonIndex === -1) {
    return { type: 'text', title: '', text: segment, fields: [] };
  }

  const head = segment.slice(0, colonIndex).trim();
  const tail = segment.slice(colonIndex + 1).trim();
  const fieldMatched = tail.match(FIELD_LABEL_PATTERN);

  // 形如「YD-20260904-0022：发货地 A → B」
  if (fieldMatched && fieldMatched[2].trim()) {
    return {
      type: 'waybill',
      title: head,
      text: '',
      fields: [buildField(fieldMatched[1], fieldMatched[2])],
    };
  }

  // 形如「路线顺序：A → B → C 调整为 B → A → C」
  if (head && head.length <= TITLE_MAX_LENGTH) {
    return { type: 'group', title: head, text: '', fields: [buildField('', tail)] };
  }

  return { type: 'text', title: '', text: segment, fields: [] };
};

export const parseRouteChangeContent = content => {
  if (content === undefined || content === null) return [];
  const text = String(content).replace(/\r\n?/g, '\n').trim();
  if (!text) return [];

  const segments = text
    .split(/[;；\n]+/)
    .map(item => item.trim())
    .filter(Boolean);

  const groups = [];

  segments.forEach(segment => {
    const group = parseSegment(segment);
    const last = groups[groups.length - 1];
    // 同一运单下的「到货地…」等无标题字段，合并进上一个运单分组
    if (group.type === 'field' && last && (last.type === 'waybill' || last.type === 'field')) {
      last.fields.push(...group.fields);
      return;
    }
    groups.push(group);
  });

  return groups;
};