MetonaSqlark/src/query/builder.ts

/**
 * metona-sqlark Query Builder — 链式查询构建器
 * @module query/builder
 *
 * 链式调用 → 构建 AST → 执行引擎操作。
 * 支持 JOIN（需要 Executor）。
 */

import type { IStorageEngine } from '../engine/interface';
import type { WhereCondition, OrderBy, SortDirection } from '../constants';
import type { SelectStatement, UpdateStatement, DeleteStatement, JoinType, JoinClause } from './ast';
import { QueryExecutor } from './executor';

// ---------------------------------------------------------------------------
//  SelectQueryBuilder
// ---------------------------------------------------------------------------

export class SelectQueryBuilder {
  private _where: WhereCondition = {};
  private _orderBy: OrderBy[] = [];
  private _limit?: number;
  private _offset?: number;
  private _joins: JoinClause[] = [];
  private _alias?: string;
  private _executor?: QueryExecutor;

  constructor(
    private engine: IStorageEngine,
    private tableName: string,
    private _columns: string[] = ['*'],
    executor?: QueryExecutor,
  ) {
    this._executor = executor;
  }

  /** 主表别名 */
  as(alias: string): this {
    this._alias = alias;
    return this;
  }

  /** INNER JOIN */
  innerJoin(table: string, on: WhereCondition, alias?: string): this {
    return this._addJoin('INNER', table, on, alias);
  }

  /** LEFT JOIN */
  leftJoin(table: string, on: WhereCondition, alias?: string): this {
    return this._addJoin('LEFT', table, on, alias);
  }

  /** RIGHT JOIN */
  rightJoin(table: string, on: WhereCondition, alias?: string): this {
    return this._addJoin('RIGHT', table, on, alias);
  }

  /** CROSS JOIN */
  crossJoin(table: string, alias?: string): this {
    return this._addJoin('CROSS', table, {}, alias);
  }

  /** 通用 JOIN */
  join(table: string, on: WhereCondition, alias?: string): this {
    return this._addJoin('INNER', table, on, alias);
  }

  private _addJoin(type: JoinType, table: string, on: WhereCondition, alias?: string): this {
    this._joins.push({ type, table, on, alias });
    return this;
  }

  /** 添加过滤条件 */
  where(condition: WhereCondition): this {
    this._where = { ...this._where, ...condition };
    return this;
  }

  /** 排序 */
  orderBy(column: string, direction: SortDirection = 'asc'): this {
    this._orderBy.push({ column, direction });
    return this;
  }

  /** 限制返回条数 */
  limit(n: number): this {
    this._limit = n;
    return this;
  }

  /** 偏移量 */
  offset(n: number): this {
    this._offset = n;
    return this;
  }

  /** 执行查询 */
  async execute(): Promise<Record<string, unknown>[]> {
    // 有 JOIN → 通过 Executor 执行
    if (this._joins.length > 0 && this._executor) {
      const ast = this.toAST();
      return this._executor.execute(ast) as Promise<Record<string, unknown>[]>;
    }

    // 无 JOIN → 直接调用引擎
    return this.engine.find(this.tableName, {
      table: this.tableName,
      columns: this._columns,
      where: this._where,
      orderBy: this._orderBy.length > 0 ? this._orderBy : undefined,
      limit: this._limit,
      offset: this._offset,
    });
  }

  /** 获取 AST */
  toAST(): SelectStatement {
    return {
      type: 'SELECT',
      columns: this._columns,
      from: this.tableName,
      alias: this._alias,
      joins: this._joins.length > 0 ? [...this._joins] : undefined,
      where: this._where,
      orderBy: this._orderBy.length > 0 ? this._orderBy : undefined,
      limit: this._limit,
      offset: this._offset,
    };
  }
}

// ---------------------------------------------------------------------------
//  UpdateQueryBuilder
// ---------------------------------------------------------------------------

export class UpdateQueryBuilder {
  private _where: WhereCondition = {};

  constructor(
    private engine: IStorageEngine,
    private tableName: string,
    private _updates: Record<string, unknown>,
  ) {}

  where(condition: WhereCondition): this {
    this._where = { ...this._where, ...condition };
    return this;
  }

  async execute(): Promise<number> {
    return this.engine.update(this.tableName, { table: this.tableName, where: this._where }, this._updates);
  }

  toAST(): UpdateStatement {
    return { type: 'UPDATE', table: this.tableName, sets: this._updates, where: this._where };
  }
}

// ---------------------------------------------------------------------------
//  DeleteQueryBuilder
// ---------------------------------------------------------------------------

export class DeleteQueryBuilder {
  private _where: WhereCondition = {};

  constructor(
    private engine: IStorageEngine,
    private tableName: string,
  ) {}

  where(condition: WhereCondition): this {
    this._where = { ...this._where, ...condition };
    return this;
  }

  async execute(): Promise<number> {
    return this.engine.delete(this.tableName, { table: this.tableName, where: this._where });
  }

  toAST(): DeleteStatement {
    return { type: 'DELETE', from: this.tableName, where: this._where };
  }
}