import { readFile } from "fs/promises";

import { CSVParser } from "../utils/csv_parser/csv_parser.js";
import { GamesLogError } from "./errors/games_log_error.js";

export type LogData = {
  eventType: string;
  eventPayload: { [key: string]: any };
}[];

export class GamesLogParser {
  async parseFile(filename: string, encoding: BufferEncoding = "utf-8") {
    let data;
    try {
      data = await readFile(filename, { encoding });
    } catch (err) {
      throw new GamesLogError(`Unable to read log file: ${filename}`, {
        cause: err instanceof Error ? err : undefined,
      });
    }
    return this.parse(data);
  }

  parse(data: string): LogData {
    const parser = new CSVParser({ headers: true });
    const csvData = parser.parse(data);

    return csvData.map((row, rowNumber) => {
      if (!("event_type" in row)) {
        throw new GamesLogError(`Missing event type on row: ${rowNumber}`);
      }
      if (!("event_payload" in row)) {
        throw new GamesLogError(`Missing event payload on row: ${rowNumber}`);
      }

      let eventPayload;
      try {
        eventPayload = JSON.parse(row.event_payload);
      } catch (err) {
        throw new GamesLogError(
          "Unable to parse event payload on row: ${rowNumber}",
          {
            cause: err instanceof Error ? err : undefined,
          }
        );
      }

      if (typeof eventPayload !== "object") {
        throw new GamesLogError("Invalid event payload on row: ${rowNumber}");
      }

      return {
        eventType: row.event_type,
        eventPayload,
      };
    });
  }
}