/**
 * 데이터베이스별 쿼리 빌더
 * PostgreSQL, MySQL/MariaDB, MSSQL, Oracle 지원
 */

export type DbType = "postgresql" | "mysql" | "mariadb" | "mssql" | "oracle";

/**
 * DB별 파라미터 플레이스홀더 생성
 */
export function getPlaceholder(dbType: string, index: number): string {
  const normalizedType = dbType.toLowerCase();

  switch (normalizedType) {
    case "postgresql":
      return `$${index}`;

    case "mysql":
    case "mariadb":
      return "?";

    case "mssql":
      return `@p${index}`;

    case "oracle":
      return `:${index}`;

    default:
      // 기본값은 PostgreSQL
      return `$${index}`;
  }
}

/**
 * UPDATE 쿼리 생성
 */
export function buildUpdateQuery(
  dbType: string,
  tableName: string,
  updates: { column: string; value: any }[],
  whereColumn: string = "id"
): { query: string; values: any[] } {
  const normalizedType = dbType.toLowerCase();
  const values: any[] = [];

  // SET 절 생성
  const setClause = updates
    .map((update, index) => {
      values.push(update.value);
      const placeholder = getPlaceholder(normalizedType, values.length);
      return `${update.column} = ${placeholder}`;
    })
    .join(", ");

  // WHERE 절 생성
  values.push(undefined); // whereValue는 나중에 설정
  const wherePlaceholder = getPlaceholder(normalizedType, values.length);

  // updated_at 처리 (DB별 NOW() 함수)
  let updatedAtExpr = "NOW()";
  if (normalizedType === "mssql") {
    updatedAtExpr = "GETDATE()";
  } else if (normalizedType === "oracle") {
    updatedAtExpr = "SYSDATE";
  }

  const query = `
    UPDATE ${tableName}
    SET ${setClause}, updated_at = ${updatedAtExpr}
    WHERE ${whereColumn} = ${wherePlaceholder}
  `;

  return { query, values };
}

/**
 * INSERT 쿼리 생성
 */
export function buildInsertQuery(
  dbType: string,
  tableName: string,
  data: Record<string, any>
): { query: string; values: any[]; returningClause: string } {
  const normalizedType = dbType.toLowerCase();
  const columns = Object.keys(data);
  const values = Object.values(data);

  // 플레이스홀더 생성
  const placeholders = columns
    .map((_, index) => getPlaceholder(normalizedType, index + 1))
    .join(", ");

  let query = `
    INSERT INTO ${tableName} (${columns.join(", ")})
    VALUES (${placeholders})
  `;

  // RETURNING/OUTPUT 절 추가 (DB별로 다름)
  let returningClause = "";
  if (normalizedType === "postgresql") {
    query += " RETURNING id";
    returningClause = "RETURNING id";
  } else if (normalizedType === "mssql") {
    // MSSQL은 OUTPUT 절을 INSERT와 VALUES 사이에
    const insertIndex = query.indexOf("VALUES");
    query =
      query.substring(0, insertIndex) +
      "OUTPUT INSERTED.id " +
      query.substring(insertIndex);
    returningClause = "OUTPUT INSERTED.id";
  } else if (normalizedType === "oracle") {
    query += " RETURNING id INTO :out_id";
    returningClause = "RETURNING id INTO :out_id";
  }
  // MySQL/MariaDB는 RETURNING 없음, LAST_INSERT_ID() 사용

  return { query, values, returningClause };
}

/**
 * SELECT 쿼리 생성
 */
export function buildSelectQuery(
  dbType: string,
  tableName: string,
  whereColumn: string = "id"
): { query: string; placeholder: string } {
  const normalizedType = dbType.toLowerCase();
  const placeholder = getPlaceholder(normalizedType, 1);

  const query = `SELECT * FROM ${tableName} WHERE ${whereColumn} = ${placeholder}`;

  return { query, placeholder };
}

/**
 * LIMIT/OFFSET 쿼리 생성 (페이징)
 */
export function buildPaginationClause(
  dbType: string,
  limit?: number,
  offset?: number
): string {
  const normalizedType = dbType.toLowerCase();

  if (!limit) {
    return "";
  }

  if (
    normalizedType === "postgresql" ||
    normalizedType === "mysql" ||
    normalizedType === "mariadb"
  ) {
    // PostgreSQL, MySQL, MariaDB: LIMIT ... OFFSET ...
    let clause = ` LIMIT ${limit}`;
    if (offset) {
      clause += ` OFFSET ${offset}`;
    }
    return clause;
  } else if (normalizedType === "mssql") {
    // MSSQL: OFFSET ... ROWS FETCH NEXT ... ROWS ONLY
    if (offset) {
      return ` OFFSET ${offset} ROWS FETCH NEXT ${limit} ROWS ONLY`;
    } else {
      return ` OFFSET 0 ROWS FETCH NEXT ${limit} ROWS ONLY`;
    }
  } else if (normalizedType === "oracle") {
    // Oracle: ROWNUM 또는 FETCH FIRST (12c+)
    if (offset) {
      return ` OFFSET ${offset} ROWS FETCH NEXT ${limit} ROWS ONLY`;
    } else {
      return ` FETCH FIRST ${limit} ROWS ONLY`;
    }
  }

  return "";
}

/**
 * 트랜잭션 시작
 */
export function getBeginTransactionQuery(dbType: string): string {
  const normalizedType = dbType.toLowerCase();

  if (normalizedType === "mssql") {
    return "BEGIN TRANSACTION";
  }

  return "BEGIN";
}

/**
 * 트랜잭션 커밋
 */
export function getCommitQuery(dbType: string): string {
  return "COMMIT";
}

/**
 * 트랜잭션 롤백
 */
export function getRollbackQuery(dbType: string): string {
  return "ROLLBACK";
}

/**
 * DB 연결 테스트 쿼리
 */
export function getConnectionTestQuery(dbType: string): string {
  const normalizedType = dbType.toLowerCase();

  switch (normalizedType) {
    case "postgresql":
      return "SELECT 1";

    case "mysql":
    case "mariadb":
      return "SELECT 1";

    case "mssql":
      return "SELECT 1";

    case "oracle":
      return "SELECT 1 FROM DUAL";

    default:
      return "SELECT 1";
  }
}