## URLCrawler Report JSON Schema

This document describes the structure of the JSON reports produced by `urlcrawler` when run with `-output json`.

### Top-level object

```json
{
  "target": "https://example.com",
  "crawledUrls": ["https://example.com", "https://example.com/about"],
  "sitemapUrls": ["https://example.com", "https://example.com/about"],
  "crawlErrors": {"https://bad.example": "error string"},
  "linkStatuses": [
    {"url": "https://example.com", "statusCode": 200, "ok": true},
    {"url": "https://other.example/broken", "statusCode": 404, "ok": false, "error": "..."}
  ],
  "pageOutlinks": {
    "https://example.com": ["https://example.com/about", "https://other.example/"]
  },
  "linkSources": {
    "https://example.com/about": ["https://example.com"]
  },
  "missingInSitemap": ["https://example.com/page-not-in-sitemap"],
  "inSitemapNotCrawled": ["https://example.com/deferred"],
  "metadata": {
    "startedAt": "2025-08-31T12:34:56Z",
    "finishedAt": "2025-08-31T12:35:57Z",
    "durationMs": 61000
  },
  "params": {
    "maxDepth": 1,
    "concurrency": 5,
    "timeoutMs": 5000,
    "userAgent": "urlcrawler/1.0",
    "sameHostOnly": true
  },
  "stats": {
    "ok": 12,
    "broken": 1,
    "status2xx": 12,
    "status3xx": 0,
    "status4xx": 1,
    "status5xx": 0,
    "statusOther": 0
  },
  "reportSummary": "crawled=2 sitemap=2 links=5 ok=4 broken=1",
  "topExternalDomains": [{"domain": "example-cdn.com", "count": 2}],
  "brokenSample": [{"url": "https://other.example/broken", "statusCode": 404, "ok": false}],
  "brokenByDomain": [{"domain": "other.example", "count": 1}],
  "pages": {
    "https://example.com": {"title": "Home — Example", "responseTimeMs": 42, "contentLength": 5123, "depth": 0}
  },
  "depthDistribution": {"0": 1, "1": 3},
  "robots": {"present": true, "fetchedAt": "2025-08-31T12:34:59Z"}
}
```

### Fields

- **target** (string): Normalized start URL used for the crawl.

- **crawledUrls** (string[]): Unique URLs that were visited during crawling. Sorted for stability.

- **sitemapUrls** (string[]; optional): All URLs discovered via `sitemap.xml` (and nested sitemaps). Present unless the sitemap is not found.

- **crawlErrors** (object map<string,string>; optional): Maps URL → error message for requests that failed (e.g., network/TLS/timeouts). Only set when errors occurred.

- **linkStatuses** (LinkStatus[]): Result of HTTP status checks for all unique links discovered (including the pages themselves).
  - **url** (string): The checked URL.
  - **statusCode** (number): HTTP status code (0 if request failed before a response was received).
  - **ok** (boolean): Convenience flag, true when `200 ≤ statusCode < 400` and no error occurred.
  - **error** (string; optional): Error string when a request failed or there was another client error.

- **pageOutlinks** (object map<string,string[]>): For each crawled page URL, the list of normalized outgoing links (internal and external).

- **linkSources** (object map<string,string[]>): Inverse index: for each discovered link URL, the list of page URLs where it appeared.

- **missingInSitemap** (string[]; optional): URLs that were crawled but not present in the sitemap.

- **inSitemapNotCrawled** (string[]; optional): URLs present in the sitemap that were not crawled (e.g., due to depth limits or off-host rules).

- **metadata** (object): Crawl timing information.
  - **startedAt** (string, RFC3339)
  - **finishedAt** (string, RFC3339)
  - **durationMs** (number)

- **params** (object): Parameters used for the run.
  - **maxDepth** (number)
  - **concurrency** (number)
  - **timeoutMs** (number)
  - **userAgent** (string)
  - **sameHostOnly** (boolean)

- **stats** (object): Summary of link status results.
  - **ok** (number)
  - **broken** (number)
  - **status2xx** (number)
  - **status3xx** (number)
  - **status4xx** (number)
  - **status5xx** (number)
  - **statusOther** (number)

- **reportSummary** (string): Compact summary string like `crawled=7 sitemap=7 links=26 ok=26 broken=0`.
- **topExternalDomains** (DomainCount[]): Top external domains referenced by links.
- **brokenSample** (LinkStatus[]): Up to 10 example broken links.
- **brokenByDomain** (DomainCount[]): Broken link counts grouped by domain.
- **pages** (object map<string,PageMeta>): Per-page metrics.
  - **title** (string): The page `<title>` text.
  - **responseTimeMs** (number): Time to fetch the document.
  - **contentLength** (number): Size of the fetched body in bytes (best effort).
  - **depth** (number): Crawl depth from the start URL.
- **depthDistribution** (object map<number,number>): Count of pages by depth.
- **robots** (object): robots.txt summary.
  - **present** (boolean): True if `robots.txt` exists and returned 200.
  - **fetchedAt** (string, RFC3339; optional): Fetch time when present.

### Notes

- URLs are normalized and deduplicated during crawl. Minor variants like trailing `/.` are normalized in output.
- All metrics described here are included by default; no extra flags are required.
- Content-type filtering: only `text/html` pages are parsed for outlinks.
- Sitemap fetching is best-effort; absence is not treated as an error.
- The JSON lists are sorted to produce stable outputs across runs.