interface SelectQuery {
  table: string;
  columns: string[];
  conditions: Array<{ column: string; operator: string; value: unknown }>;
  orderByColumn?: string;
  orderDirection: 'ASC' | 'DESC';
  limitValue?: number;
  offsetValue?: number;
}

class SelectQueryBuilder {
  private query: SelectQuery = {
    table: '',
    columns: ['*'],
    conditions: [],
    orderDirection: 'ASC',
  };

  from(table: string): this {
    this.query.table = table;
    return this;
  }

  select(...columns: string[]): this {
    this.query.columns = columns;
    return this;
  }

  where(column: string, operator: '=' | '>' | '<' | '>=' | '<=' | '!=', value: unknown): this {
    this.query.conditions.push({ column, operator, value });
    return this;
  }

  orderBy(column: string, direction: 'ASC' | 'DESC' = 'ASC'): this {
    this.query.orderByColumn = column;
    this.query.orderDirection = direction;
    return this;
  }

  limit(n: number): this {
    if (n < 1) throw new Error('Limit must be at least 1');
    this.query.limitValue = n;
    return this;
  }

  offset(n: number): this {
    this.query.offsetValue = n;
    return this;
  }

  build(): { sql: string; params: unknown[] } {
    if (!this.query.table) throw new Error('Table is required — call .from()');

    const params: unknown[] = [];
    let sql = `SELECT ${this.query.columns.join(', ')} FROM ${this.query.table}`;

    if (this.query.conditions.length > 0) {
      const whereClauses = this.query.conditions.map((c) => {
        params.push(c.value);
        return `${c.column} ${c.operator} $${params.length}`;
      });
      sql += ` WHERE ${whereClauses.join(' AND ')}`;
    }

    if (this.query.orderByColumn) {
      sql += ` ORDER BY ${this.query.orderByColumn} ${this.query.orderDirection}`;
    }

    if (this.query.limitValue !== undefined) {
      sql += ` LIMIT ${this.query.limitValue}`;
    }

    if (this.query.offsetValue !== undefined) {
      sql += ` OFFSET ${this.query.offsetValue}`;
    }

    return { sql, params };
  }
}

// שימוש
const { sql, params } = new SelectQueryBuilder()
  .from('orders')
  .select('id', 'user_id', 'total', 'created_at')
  .where('status', '=', 'pending')
  .where('total', '>', 100)
  .orderBy('created_at', 'DESC')
  .limit(20)
  .offset(40)
  .build();

// SELECT id, user_id, total, created_at FROM orders
// WHERE status = $1 AND total > $2
// ORDER BY created_at DESC LIMIT 20 OFFSET 40
console.log(sql);
console.log(params); // ['pending', 100]
Builder Pattern — בנייה מדורגת

Builder Pattern — בנייה מדורגת

Builder Pattern — בנייה מדורגת
