import { CommandParser } from '../client/parser';
import { Command } from '../RESP/types';
import { transformTuplesToMap } from './generic-transformers';

type RawHistogram = [string, number, string, number[]];

type Histogram = Record<string, {
  calls: number;
  histogram_usec: Record<string, number>;
}>;

const id = (n: number) => n;

export default {
  CACHEABLE: false,
  IS_READ_ONLY: true,
  /**
   * Constructs the LATENCY HISTOGRAM command
   *
   * @param parser - The command parser
   * @param commands - The list of redis commands to get histogram for
   * @see https://redis.io/docs/latest/commands/latency-histogram/
   */
  parseCommand(parser: CommandParser, ...commands: string[]) {
    const args = ['LATENCY', 'HISTOGRAM'];
    if (commands.length !== 0) {
      args.push(...commands);
    }
    parser.push(...args);
  },
  transformReply: {
    2: (reply: (string | RawHistogram)[]): Histogram => {
      const result: Histogram = {};
      if (reply.length === 0) return result;
      for (let i = 1; i < reply.length; i += 2) {
        const histogram = reply[i] as RawHistogram;
        result[reply[i - 1] as string] = {
          calls: histogram[1],
          histogram_usec: transformTuplesToMap(histogram[3], id),
        };
      }
      return result;
    },
    3: undefined as unknown as () => Histogram,
  }
} as const satisfies Command;