import type { VendorSqlFunction } from '../types';

/** Logical/structural keywords used in the search segment of every vendor. */
export const SHARED_SEARCH_KEYWORDS = ['AND', 'OR', 'NOT', 'TO', 'IN'];


/**
 * Core SQL keywords that are valid in the analyze segment for all five vendors.
 * Vendor-specific extensions (e.g. APPROX_DISTINCT, MATCHES) are added per file.
 */
export const SHARED_SQL_KEYWORDS = [
  'SELECT',
  'FROM',
  'WHERE',
  'AND',
  'OR',
  'NOT',
  'IN',
  'IS',
  'NULL',
  'TRUE',
  'FALSE',
  'AS',
  'DISTINCT',
  'BETWEEN',
  'LIKE',
  'CASE',
  'WHEN',
  'THEN',
  'ELSE',
  'END',
  'CAST',
  'GROUP',
  'BY',
  'HAVING',
  'ORDER',
  'ASC',
  'DESC',
  'LIMIT',
  'OFFSET',
  'UNION',
  'ALL',
  'WITH',
  'JOIN',
  'LEFT',
  'RIGHT',
  'INNER',
  'OUTER',
  'ON',
];

/** Aggregations available in every vendor's SQL dialect. */
export const SHARED_SQL_AGGREGATES: VendorSqlFunction[] = [
  { name: 'COUNT', signature: 'COUNT(expression)', doc: '返回行数' },
  { name: 'SUM', signature: 'SUM(expression)', doc: '返回数值之和' },
  { name: 'AVG', signature: 'AVG(expression)', doc: '返回数值的平均值' },
  { name: 'MIN', signature: 'MIN(expression)', doc: '返回最小值' },
  { name: 'MAX', signature: 'MAX(expression)', doc: '返回最大值' },
];

/** Common scalar functions implemented by every vendor's SQL engine. */
export const SHARED_SQL_SCALARS: VendorSqlFunction[] = [
  { name: 'UPPER', signature: 'UPPER(string)', doc: '转大写' },
  { name: 'LOWER', signature: 'LOWER(string)', doc: '转小写' },
  { name: 'LENGTH', signature: 'LENGTH(string)', doc: '字符串长度' },
  { name: 'SUBSTRING', signature: 'SUBSTRING(string, start, length)', doc: '截取子串' },
  { name: 'TRIM', signature: 'TRIM(string)', doc: '去除首尾空白' },
  { name: 'CONCAT', signature: 'CONCAT(s1, s2, ...)', doc: '拼接字符串' },
  { name: 'ROUND', signature: 'ROUND(number[, decimals])', doc: '四舍五入' },
  { name: 'ABS', signature: 'ABS(number)', doc: '绝对值' },
  { name: 'COALESCE', signature: 'COALESCE(v1, v2, ...)', doc: '返回第一个非 NULL 值' },
  { name: 'NOW', signature: 'NOW()', doc: '当前时间' },
  { name: 'DATE_FORMAT', signature: "DATE_FORMAT(time, format)", doc: '时间格式化' },
];