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import {  objectToKeyValueArrays,  toSQLKeyValuePair,  toSQLValueType,  valuePlaceholders,} from "./helpers.ts";
type WhereCondition = "=" | ">" | "<" | ">=" | "<=" | "!=" | "LIKE" | "IN";
export class Query<T extends Record<string, unknown>> {  private _table = "";  private _query = "";  private _placeholderCount = 1;
  public select(...fields: string[]) {    const keys = fields.length > 0 ? fields.join(", ") : "*";
    this._query = `SELECT ${keys} FROM ${this._table}`;    return this;  }
  public insert(data: T) {    const [keys, values] = objectToKeyValueArrays(data);
    const keysSQL = `(${keys.join(", ")})`;
    this._query = `INSERT INTO ${this._table} ${keysSQL} VALUES ${      valuePlaceholders(values, this._placeholderCount++)    }`;    return this;  }
  public update(data: T) {    const [keys, values] = objectToKeyValueArrays(data);
    let result = "";    for (let i = 0; i < keys.length; i++) {      result += ` ${toSQLKeyValuePair(keys[i], values[i])}`;      if (i != keys.length - 1) {        result += ",";      }    }
    this._query += ` UPDATE ${this._table} SET ${result.trim()}`;    return this;  }
  public delete() {    this._query = `DELETE FROM ${this._table}`;    return this;  }
  // TODO: This is the most basic form of where, need to improve.  // Should I use value or placeholder?  public where(    key: string,    condition: WhereCondition,    value: string | number | boolean,  ) {    const valueSQL = toSQLValueType(value);    this._query += ` WHERE ${key} ${condition} ${valueSQL}`;    return this;  }
  public returning(...fields: string[]) {    const keys = fields.length > 0 ? fields.join(", ") : "*";
    this._query += ` RETURNING ${keys}`;    return this;  }
  public table(name: string) {    this._table = name;    return this;  }
  public build() {    const res = this._query.trim() + ";";    this._query = "";    return res;  }}