import type { CountResult } from "../types.js";

export class Metrics {
  private readonly requestCounts = new Map<string, number>();
  private requestDurationMs = 0;
  private scanCount = 0;
  private scanDurationMs = 0;
  private cachedScanCount = 0;
  private countedFiles = 0;
  private countedLines = 0;

  recordRequest(route: string, status: number, durationMs: number): void {
    const key = `${route}\u0000${status}`;
    this.requestCounts.set(key, (this.requestCounts.get(key) ?? 0) + 1);
    this.requestDurationMs += durationMs;
  }

  recordScan(result: CountResult): void {
    this.scanCount += 1;
    this.scanDurationMs += result.durationMs;
    this.cachedScanCount += Number(result.cached);
    this.countedFiles += result.fileCount;
    this.countedLines += result.lineCount;
  }

  renderPrometheus(): string {
    const lines = [
      "# HELP loc_via_git_http_requests_total HTTP responses by route and status.",
      "# TYPE loc_via_git_http_requests_total counter"
    ];
    for (const [key, count] of this.requestCounts) {
      const [route, status] = key.split("\u0000");
      lines.push(`loc_via_git_http_requests_total{route="${route}",status="${status}"} ${count}`);
    }
    lines.push(
      "# HELP loc_via_git_http_request_duration_ms_total Total HTTP request duration in milliseconds.",
      "# TYPE loc_via_git_http_request_duration_ms_total counter",
      `loc_via_git_http_request_duration_ms_total ${this.requestDurationMs}`,
      "# HELP loc_via_git_scans_total Completed LOC scans.",
      "# TYPE loc_via_git_scans_total counter",
      `loc_via_git_scans_total ${this.scanCount}`,
      "# HELP loc_via_git_cached_scans_total Completed scans served from cache.",
      "# TYPE loc_via_git_cached_scans_total counter",
      `loc_via_git_cached_scans_total ${this.cachedScanCount}`,
      "# HELP loc_via_git_scan_duration_ms_total Total scan duration in milliseconds.",
      "# TYPE loc_via_git_scan_duration_ms_total counter",
      `loc_via_git_scan_duration_ms_total ${this.scanDurationMs}`,
      "# HELP loc_via_git_counted_files_total Files included in completed scan results.",
      "# TYPE loc_via_git_counted_files_total counter",
      `loc_via_git_counted_files_total ${this.countedFiles}`,
      "# HELP loc_via_git_counted_lines_total Non-empty lines included in completed scan results.",
      "# TYPE loc_via_git_counted_lines_total counter",
      `loc_via_git_counted_lines_total ${this.countedLines}`
    );
    return `${lines.join("\n")}\n`;
  }
}