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 {
			// Fetch only if the cache miss occurs and Crawler is enabled
			if config.CrawlerEnabled {
				combinedResults = fetchTextResults(query, safe, lang, page)
				if len(combinedResults) > 0 {
					resultsCache.Set(cacheKey, convertToSearchResults(combinedResults))
				}
			} else {
				printInfo("Crawler disabled; skipping fetching.")
			}
		} else {
			textResults, _, _ := convertToSpecificResults(results)
			combinedResults = textResults
		}
	case <-time.After(2 * time.Second):
		printInfo("Cache check timeout")
		if config.CrawlerEnabled {
			combinedResults = fetchTextResults(query, safe, lang, page)
			if len(combinedResults) > 0 {
				resultsCache.Set(cacheKey, convertToSearchResults(combinedResults))
			}
		} else {
			printInfo("Crawler disabled; skipping fetching.")
		}
	}

	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 Crawler is disabled, do not fetch from search engines
	if !config.CrawlerEnabled {
		printDebug("Crawler is disabled; skipping search engine fetching.")
		return results // Return an empty list
	}

	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

	// Debug print to verify engine and page number being fetched
	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 // Recalculate for the new engine
			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
	}
}