Search/text.go

package main

import (
	"fmt"
	"net/http"
	"time"
)

var textSearchEngines []SearchEngine

func init() {
	textSearchEngines = []SearchEngine{
		{Name: "Google", Func: wrapTextSearchFunc(PerformGoogleTextSearch)},
		{Name: "LibreX", Func: wrapTextSearchFunc(PerformLibreXTextSearch)},
		{Name: "Brave", Func: wrapTextSearchFunc(PerformBraveTextSearch)},
		{Name: "DuckDuckGo", Func: wrapTextSearchFunc(PerformDuckDuckGoTextSearch)},
		// {Name: "SearXNG", Func: wrapTextSearchFunc(PerformSearXNGTextSearch), Weight: 2}, // Uncomment when implemented
	}
}

func HandleTextSearch(w http.ResponseWriter, settings UserSettings, query string, page int) {
	startTime := time.Now()

	cacheKey := CacheKey{Query: query, Page: page, Safe: settings.SafeSearch == "active", Lang: settings.SearchLanguage, Type: "text"}
	combinedResults := getTextResultsFromCacheOrFetch(cacheKey, query, settings.SafeSearch, settings.SearchLanguage, page)

	hasPrevPage := page > 1

	// Prefetch next and previous pages asynchronously
	go prefetchPage(query, settings.SafeSearch, settings.SearchLanguage, page+1)
	if hasPrevPage {
		go prefetchPage(query, settings.SafeSearch, settings.SearchLanguage, page-1)
	}

	elapsedTime := time.Since(startTime)

	// Prepare the data to pass to the template
	data := map[string]interface{}{
		"Results":         combinedResults,
		"Query":           query,
		"Fetched":         fmt.Sprintf("%.2f %s", elapsedTime.Seconds(), Translate("seconds")), // Time for fetching results
		"Page":            page,
		"HasPrevPage":     page > 1,
		"HasNextPage":     len(combinedResults) >= 50,
		"NoResults":       len(combinedResults) == 0,
		"LanguageOptions": languageOptions,
		"CurrentLang":     settings.SearchLanguage,
		"Theme":           settings.Theme,
		"Safe":            settings.SafeSearch,
		"IsThemeDark":     settings.IsThemeDark,
		"Trans":           Translate,
	}

	// Render the template without measuring time
	renderTemplate(w, "text.html", data)
}

func getTextResultsFromCacheOrFetch(cacheKey CacheKey, query, safe, lang string, page int) []TextSearchResult {
	cacheChan := make(chan []SearchResult)
	var combinedResults []TextSearchResult

	go func() {
		results, exists := resultsCache.Get(cacheKey)
		if exists {
			printDebug("Cache hit")
			cacheChan <- results
		} else {
			printDebug("Cache miss")
			cacheChan <- nil
		}
	}()

	select {
	case results := <-cacheChan:
		if results == nil {
			// Always attempt to fetch results on a cache miss
			combinedResults = fetchTextResults(query, safe, lang, page)
			if len(combinedResults) > 0 {
				resultsCache.Set(cacheKey, convertToSearchResults(combinedResults))
			}
		} else {
			textResults, _, _, _ := convertToSpecificResults(results)
			combinedResults = textResults
		}
	case <-time.After(2 * time.Second):
		printInfo("Cache check timeout")
		// Even on timeout, attempt to fetch results
		combinedResults = fetchTextResults(query, safe, lang, page)
		if len(combinedResults) > 0 {
			resultsCache.Set(cacheKey, convertToSearchResults(combinedResults))
		}
	}

	return combinedResults
}

func prefetchPage(query, safe, lang string, page int) {
	cacheKey := CacheKey{Query: query, Page: page, Safe: safe == "active", Lang: lang, Type: "text"}
	if _, exists := resultsCache.Get(cacheKey); !exists {
		printInfo("Page %d not cached, caching now...", page)
		if config.CrawlerEnabled {
			pageResults := fetchTextResults(query, safe, lang, page)
			if len(pageResults) > 0 {
				resultsCache.Set(cacheKey, convertToSearchResults(pageResults))
			}
		} else {
			printInfo("Crawler disabled; skipping prefetch for page %d", page)
		}
	} else {
		printInfo("Page %d already cached", page)
	}
}

func fetchTextResults(query, safe, lang string, page int) []TextSearchResult {
	var results []TextSearchResult

	if !config.CrawlerEnabled {
		printDebug("Crawler is disabled; fetching from local index.")

		// Calculate the starting position based on the page number
		indexedResults, err := SearchIndex(query, page, 10)
		if err != nil {
			printErr("Error searching the index: %v", err)
			return results // Return empty results on error
		}

		// Convert indexed results to TextSearchResult format
		for _, doc := range indexedResults {
			results = append(results, TextSearchResult{
				URL:         doc.Link,
				Header:      doc.Title,
				Description: doc.Description,
				Source:      doc.Tags,
			})
		}

		return results
	} else {
		// Crawler is enabled, so use the search engines
		engineCount := len(textSearchEngines)

		// Determine which engine to use for the current page
		engineIndex := (page - 1) % engineCount
		engine := textSearchEngines[engineIndex]

		// Calculate the page number for this engine
		enginePage := (page-1)/engineCount + 1

		printDebug("Fetching results for overall page %d using engine: %s (engine page %d)", page, engine.Name, enginePage)

		// Fetch results from the selected engine
		searchResults, _, err := engine.Func(query, safe, lang, enginePage)
		if err != nil {
			printWarn("Error performing search with %s: %v", engine.Name, err)
		} else {
			results = append(results, validateResults(searchResults)...)
		}

		// If no results are found with the selected engine, try the next in line
		if len(results) == 0 {
			for i := 1; i < engineCount; i++ {
				nextEngine := textSearchEngines[(engineIndex+i)%engineCount]
				enginePage = (page-1)/engineCount + 1
				printInfo("No results found, trying next engine: %s (engine page %d)", nextEngine.Name, enginePage)

				searchResults, _, err := nextEngine.Func(query, safe, lang, enginePage)
				if err != nil {
					printWarn("Error performing search with %s: %v", nextEngine.Name, err)
					continue
				}
				results = append(results, validateResults(searchResults)...)
				if len(results) > 0 {
					break
				}
			}
		}

		printInfo("Fetched %d results for overall page %d", len(results), page)
		return results
	}
}

func validateResults(searchResults []SearchResult) []TextSearchResult {
	var validResults []TextSearchResult

	// Remove anything that is missing a URL or Header
	for _, result := range searchResults {
		textResult := result.(TextSearchResult)
		if textResult.URL != "" || textResult.Header != "" {
			validResults = append(validResults, textResult)
		}
	}

	return validResults
}

func wrapTextSearchFunc(f func(string, string, string, int) ([]TextSearchResult, time.Duration, error)) func(string, string, string, int) ([]SearchResult, time.Duration, error) {
	return func(query, safe, lang string, page int) ([]SearchResult, time.Duration, error) {
		textResults, duration, err := f(query, safe, lang, page)
		if err != nil {
			return nil, duration, err
		}
		searchResults := make([]SearchResult, len(textResults))
		for i, result := range textResults {
			searchResults[i] = result
		}
		return searchResults, duration, nil
	}
}