/**
 * metona-sqlark Query AST — 查询抽象语法树类型定义
 * @module query/ast
 *
 * QueryBuilder 和 SQL Parser 统一输出此 AST，
 * Executor 只认 AST，保证两种查询接口行为一致。
 */

import type { WhereCondition, OrderBy } from '../constants';

// ---------------------------------------------------------------------------
//  AST 语句类型枚举
// ---------------------------------------------------------------------------

export type StatementType =
  | 'SELECT'
  | 'INSERT'
  | 'UPDATE'
  | 'DELETE'
  | 'CREATE_TABLE'
  | 'DROP_TABLE';

// ---------------------------------------------------------------------------
//  列引用
// ---------------------------------------------------------------------------

/** 列引用，'*' 表示所有列；支持 'table.column' 格式 */
export type ColumnRef = string;

// ---------------------------------------------------------------------------
//  JOIN
// ---------------------------------------------------------------------------

/** JOIN 类型 */
export type JoinType = 'INNER' | 'LEFT' | 'RIGHT' | 'CROSS';

/** JOIN 子句 */
export interface JoinClause {
  type: JoinType;
  table: string;
  alias?: string;
  on: WhereCondition;
}

// ---------------------------------------------------------------------------
//  聚合函数
// ---------------------------------------------------------------------------

/** 聚合函数类型 */
export type AggregateFunc = 'COUNT' | 'SUM' | 'AVG' | 'MIN' | 'MAX';

/** 聚合表达式 */
export interface AggregateExpression {
  type: 'AGGREGATE';
  func: AggregateFunc;
  column: string; // '*' for COUNT(*)
  alias?: string;
}

// ---------------------------------------------------------------------------
//  DDL: CREATE TABLE
// ---------------------------------------------------------------------------

export interface ASTColumnDef {
  name: string;
  type: string;
  primaryKey?: boolean;
  unique?: boolean;
  required?: boolean;
  default?: unknown;
  index?: boolean;
  maxLength?: number;
  min?: number;
  max?: number;
}

export interface CreateTableStatement {
  type: 'CREATE_TABLE';
  name: string;
  columns: ASTColumnDef[];
}

// ---------------------------------------------------------------------------
//  DDL: DROP TABLE
// ---------------------------------------------------------------------------

export interface DropTableStatement {
  type: 'DROP_TABLE';
  name: string;
}

// ---------------------------------------------------------------------------
//  DML: INSERT
// ---------------------------------------------------------------------------

export interface InsertStatement {
  type: 'INSERT';
  into: string;
  columns?: string[];
  values: unknown[][];
}

// ---------------------------------------------------------------------------
//  DML: UPDATE
// ---------------------------------------------------------------------------

export interface UpdateStatement {
  type: 'UPDATE';
  table: string;
  sets: Record<string, unknown>;
  where: WhereCondition;
}

// ---------------------------------------------------------------------------
//  DML: DELETE
// ---------------------------------------------------------------------------

export interface DeleteStatement {
  type: 'DELETE';
  from: string;
  where: WhereCondition;
}

// ---------------------------------------------------------------------------
//  DQL: SELECT
// ---------------------------------------------------------------------------

export interface SelectStatement {
  type: 'SELECT';
  columns: ColumnRef[];
  distinct?: boolean;
  from: string;
  /** 主表别名 */
  alias?: string;
  /** JOIN 子句列表 */
  joins?: JoinClause[];
  where: WhereCondition;
  /** GROUP BY */
  groupBy?: string[];
  /** HAVING */
  having?: WhereCondition;
  orderBy?: OrderBy[];
  limit?: number;
  offset?: number;
}

// ---------------------------------------------------------------------------
//  AST 联合类型
// ---------------------------------------------------------------------------

export type Statement =
  | SelectStatement
  | InsertStatement
  | UpdateStatement
  | DeleteStatement
  | CreateTableStatement
  | DropTableStatement;