import DiffReporterAggregate from "./DiffReporterAggregate";
import { readdirSync } from "fs";
import { Reporter } from "../Core/Reporter";

export type ReporterLoader = () => Reporter[];

export class ReporterFactory {
  static loadReporter(name: string | (string | Reporter)[]): Reporter {
    if (Array.isArray(name)) {
      const reporters = ReporterFactory.loadAllReporters(name);
      return new DiffReporterAggregate(reporters);
    }

    name = name.toLowerCase();

    try {
      const ReporterCtor = require(`./Reporters/${name}Reporter`);
      if (!ReporterCtor.default) {
        return new ReporterCtor();
      }
      return new ReporterCtor.default();
    } catch (e) {
      const allFiles = readdirSync(__dirname);
      const availableReporters = allFiles
        .map((item) => item.replace("Reporter.js", ""))
        .join(", ");
      throw new Error(
        `Error loading reporter or reporter not found [${name}]. Try one of the following [${availableReporters}]. Original Error: ${e}`,
      );
    }
  }

  static throwUnknownReporterError(reporter: unknown): never {
    throw new Error(
      `Unknown reporter: typeof= [${typeof reporter}]. Reporters are either a string like "gitdiff" or an object that conforms to the custom reporter interface.`,
    );
  }

  static assertValidReporter(
    reporter: Partial<Reporter>,
  ): reporter is Reporter {
    if (typeof reporter.name !== "string") {
      console.error("invalid reporter", reporter);
      throw new Error(
        "A valid reporter should have a 'name' property. EX: { name: \"my-custom-reporter\" }",
      );
    }

    if (typeof reporter.canReportOn !== "function") {
      console.error("invalid reporter", reporter);
      throw new Error(
        "A valid reporter should have a '{ canReportOn: function(fileName) { return true; // Example } ' function",
      );
    }

    if (typeof reporter.report !== "function") {
      console.error("invalid reporter", reporter);
      throw new Error(
        "A valid reporter should have a ' { report: function (approvedFilePath, receivedFilePath) {...} }' function",
      );
    }

    return true;
  }

  static loadAllReporters(reporters: (string | Reporter)[]): Reporter[] {
    const reporterInstances: Reporter[] = [];

    reporters.forEach((reporter) => {
      if (typeof reporter === "object") {
        ReporterFactory.assertValidReporter(reporter);
        reporterInstances.push(reporter as Reporter);
      } else if (typeof reporter === "string") {
        const reporterInstance = ReporterFactory.loadReporter(
          reporter,
        ) as Reporter;
        reporterInstances.push(reporterInstance);
      } else {
        ReporterFactory.throwUnknownReporterError(reporter);
      }
    });

    return reporterInstances;
  }
}