import { UptimeRunnerApiClient } from './api-client.ts';
import { CheckExecutor } from './check-executor.ts';
import type {
  IRunOnceResult,
  IUptimeCheckResult,
  IUptimeRunnerConfig,
  TCheckJob,
} from './interfaces.ts';
import denoConfig from '../deno.json' with { type: 'json' };

export class UptimeRunner {
  private readonly apiClient: UptimeRunnerApiClient;
  private readonly checkExecutor: CheckExecutor;
  private running = false;

  constructor(private readonly config: IUptimeRunnerConfig, apiClientArg?: UptimeRunnerApiClient) {
    this.apiClient = apiClientArg ?? new UptimeRunnerApiClient(config);
    this.checkExecutor = new CheckExecutor(config.runnerId);
  }

  public async run(): Promise<void> {
    this.running = true;
    console.log(`uptimerunner ${this.config.runnerId} connected to ${this.config.instanceUrl}`);

    while (this.running) {
      const started = Date.now();
      try {
        await this.heartbeat().catch((error) => {
          console.warn(
            `heartbeat failed: ${error instanceof Error ? error.message : String(error)}`,
          );
        });
        const result = await this.runOnce();
        if (result.results.length > 0) {
          console.log(`reported ${result.results.length} check result(s)`);
        }
      } catch (error) {
        console.error(
          `runner iteration failed: ${error instanceof Error ? error.message : String(error)}`,
        );
      }

      const elapsed = Date.now() - started;
      const delayMs = Math.max((this.config.pollIntervalMs ?? 30000) - elapsed, 1000);
      await delayFor(delayMs);
    }
  }

  public stop(): void {
    this.running = false;
  }

  public async runOnce(): Promise<IRunOnceResult> {
    const checks = await this.apiClient.fetchAssignedChecks(
      this.config.runnerId,
      this.config.labels ?? [],
    );
    const results = await this.executeChecks(checks);
    await this.apiClient.submitResults(this.config.runnerId, results);
    return { checks, results };
  }

  private async heartbeat(): Promise<void> {
    await this.apiClient.heartbeat({
      runnerId: this.config.runnerId,
      labels: this.config.labels,
      version: denoConfig.version,
    });
  }

  private async executeChecks(checksArg: TCheckJob[]): Promise<IUptimeCheckResult[]> {
    const maxConcurrentChecks = this.config.maxConcurrentChecks ?? 8;
    const results: IUptimeCheckResult[] = [];
    let nextIndex = 0;

    const worker = async () => {
      while (nextIndex < checksArg.length) {
        const currentIndex = nextIndex++;
        results[currentIndex] = await this.checkExecutor.execute(checksArg[currentIndex]);
      }
    };

    await Promise.all(
      Array.from({ length: Math.min(maxConcurrentChecks, checksArg.length) }, () => worker()),
    );
    return results;
  }
}

async function delayFor(millisecondsArg: number): Promise<void> {
  await new Promise((resolve) => setTimeout(resolve, millisecondsArg));
}