The analyzeCache function analyzes the cache file for a given URL, extracting statistics such as the number of cache objects, distinct domains, and repeated URLs. It returns an object with various statistics, including the count of pages, caches, and domains, as well as the URLs for the 10 largest objects and repeated URLs.

Run example

npm run import -- "analyze cache file"

analyze cache file

var {URL} = require('url')
var fs = require('fs')
var {findCache} = importer.import("domain crawler tools")

function analyzeCache(url) {
    var cache = findCache(url)
    if(cache.length === 0) {
        return {
            error: `No cache file found ${url}`
        }
    }
    
    var json = JSON.parse(fs.readFileSync(cache[0]))
    var domains = json.map(s => new URL(s.url).hostname)
        .filter((h, i, arr) => arr.indexOf(h) === i)
    var largeness = json.sort((a, b) => b.content.length - a.content.length)
        .slice(0, 10)
    var urls = json.map(s => s.url)
    var repeats = json.filter((s, i, arr) => i > 0 && urls.indexOf(s.url) === i)
    fs.writeFileSync(cache[0], JSON.stringify(repeats, null, 2))
    return {
        countPages: json.length,
        countCaches: cache.length,
        target: json[0].url,
        countDomains: domains.length,
        domains: domains,
        countLargest: largeness.reduce((cur, l) => cur + l.content.length, 0),
        largest10: largeness.map(l => l.url),
        repeats: json.length - repeats.length,
    }
}

module.exports = analyzeCache

```javascript
const { URL } = require('url');
const fs = require('fs');
const { findCache } = require('./domain-crawler-tools'); // import using a module resolver

/**
 * Analyze a cache file for a given URL.
 * 
 * @param {string} url - The URL to analyze.
 * @returns {object} An object containing analysis results.
 */
function analyzeCache(url) {
    const cache = findCache(url);

    if (cache.length === 0) {
        // TODO: Consider using a more specific error message or a custom error object.
        return { error: `No cache file found for ${url}` };
    }

    try {
        const json = JSON.parse(fs.readFileSync(cache[0]));
        const domains = Array.from(new Set(json.map(item => new URL(item.url).hostname)));
        const largeness = json.slice().sort((a, b) => b.content.length - a.content.length).slice(0, 10);
        const urls = json.map(item => item.url);
        const repeats = json.filter((item, index) => index > 0 && urls.indexOf(item.url) === index);

        // TODO: Consider adding error handling for write operations.
        fs.writeFileSync(cache[0], JSON.stringify(repeats, null, 2));

        return {
            countPages: json.length,
            countCaches: cache.length,
            target: json[0].url,
            countDomains: domains.length,
            domains,
            countLargest: largeness.reduce((sum, item) => sum + item.content.length, 0),
            largest10: largeness.map(item => item.url),
            repeats: json.length - repeats.length,
        };
    } catch (error) {
        // TODO: Consider adding error handling for JSON parsing or file reading errors.
        return { error: `Failed to analyze cache: ${error.message}` };
    }
}

module.exports = analyzeCache;
```

Code Breakdown

Dependencies

• var {URL} = require('url'): Imports the URL class from the built-in Node.js url module.
• var fs = require('fs'): Imports the file system module.
• var {findCache} = importer.import('domain crawler tools'): Imports the findCache function from an external module using the importer object.

Function analyzeCache(url)

Purpose

Analyzes the cache file for the given url and returns an object with various statistics.

Steps

1. Finds the cache file for the given url using findCache(url).
2. If no cache file is found, returns an object with an error message.
3. Reads the cache file as JSON and maps each object to its hostname using new URL(s.url).hostname.
4. Filters the unique hostnames to get the distinct domains.
5. Sorts the cache objects in descending order by content length and takes the first 10 largest objects.
6. Maps the JSON objects to their URLs.
7. Filters the cache objects to find repeated URLs and writes the result back to the cache file.
8. Returns an object with various statistics:
   • countPages: The number of cache objects.
   • countCaches: The number of cache files.
   • target: The URL of the first cache object.
   • countDomains: The number of distinct domains.
   • domains: An array of distinct domains.
   • countLargest: The total content length of the 10 largest objects.
   • largest10: An array of URLs for the 10 largest objects.
   • repeats: The number of unique URLs in the cache.

Export

The analyzeCache function is exported as a module.