Search/text.go

package main

import (
	"fmt"
	"html/template"
	"log"
	"math/rand"
	"net/http"
	"sync"
	"time"
)

var (
	searchEngines    []searchEngine
	searchEngineLock sync.Mutex
)

type searchEngine struct {
	Name   string
	Func   func(string, string, string, int) ([]TextSearchResult, error)
	Weight int
}

func init() {
	searchEngines = []searchEngine{
		{Name: "Google", Func: PerformGoogleTextSearch, Weight: 1},
		{Name: "LibreX", Func: PerformLibreXTextSearch, Weight: 2},
		// {Name: "DuckDuckGo", Func: PerformDuckDuckGoTextSearch, Weight: 3}, // DuckDuckGo timeouts too fast and search results are trash
		// {Name: "SearXNG", Func: PerformSearXNGTextSearch, Weight: 2}, // Uncomment when implemented
	}

	rand.Seed(time.Now().UnixNano())
}

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

	cacheKey := CacheKey{Query: query, Page: page, Safe: safe == "true", Lang: lang, Type: "text"}
	combinedResults := getTextResultsFromCacheOrFetch(cacheKey, query, safe, lang, page)

	hasPrevPage := page > 1
	hasNextPage := len(combinedResults) > 0

	displayResults(w, combinedResults, query, lang, time.Since(startTime).Seconds(), page, hasPrevPage, hasNextPage)

	// Prefetch next and previous pages
	go prefetchPage(query, safe, lang, page+1)
	if hasPrevPage {
		go prefetchPage(query, safe, lang, page-1)
	}
}

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 {
			log.Println("Cache hit")
			cacheChan <- results
		} else {
			log.Println("Cache miss")
			cacheChan <- nil
		}
	}()

	select {
	case results := <-cacheChan:
		if results == nil {
			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):
		log.Println("Cache check timeout")
		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 == "true", Lang: lang, Type: "text"}
	if _, exists := resultsCache.Get(cacheKey); !exists {
		log.Printf("Page %d not cached, caching now...", page)
		pageResults := fetchTextResults(query, safe, lang, page)
		if len(pageResults) > 0 {
			resultsCache.Set(cacheKey, convertToSearchResults(pageResults))
		}
	} else {
		log.Printf("Page %d already cached", page)
	}
}

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

	for attempts := 0; attempts < len(searchEngines); attempts++ {
		engine := selectSearchEngine()
		log.Printf("Using search engine: %s", engine.Name)

		results, err = engine.Func(query, safe, lang, page)
		if err != nil {
			log.Printf("Error performing search with %s: %v", engine.Name, err)
			continue
		}

		if len(results) > 0 {
			break
		}
	}

	return results
}

func selectSearchEngine() searchEngine {
	searchEngineLock.Lock()
	defer searchEngineLock.Unlock()

	totalWeight := 0
	for _, engine := range searchEngines {
		totalWeight += engine.Weight
	}

	randValue := rand.Intn(totalWeight)
	for _, engine := range searchEngines {
		if randValue < engine.Weight {
			// Adjust weights for load balancing
			for i := range searchEngines {
				if searchEngines[i].Name == engine.Name {
					searchEngines[i].Weight = max(1, searchEngines[i].Weight-1)
				} else {
					searchEngines[i].Weight++
				}
			}
			return engine
		}
		randValue -= engine.Weight
	}

	return searchEngines[0] // fallback to the first engine
}

func displayResults(w http.ResponseWriter, results []TextSearchResult, query, lang string, elapsed float64, page int, hasPrevPage, hasNextPage bool) {
	log.Printf("Displaying results for page %d", page)
	log.Printf("Total results: %d", len(results))
	log.Printf("Has previous page: %t, Has next page: %t", hasPrevPage, hasNextPage)

	tmpl, err := template.New("text.html").Funcs(template.FuncMap{
		"sub": func(a, b int) int {
			return a - b
		},
		"add": func(a, b int) int {
			return a + b
		},
	}).ParseFiles("templates/text.html")
	if err != nil {
		http.Error(w, "Internal Server Error", http.StatusInternalServerError)
		return
	}

	data := struct {
		Results         []TextSearchResult
		Query           string
		Fetched         string
		Page            int
		HasPrevPage     bool
		HasNextPage     bool
		LanguageOptions []LanguageOption
		CurrentLang     string
	}{
		Results:         results,
		Query:           query,
		Fetched:         fmt.Sprintf("%.2f seconds", elapsed),
		Page:            page,
		HasPrevPage:     hasPrevPage,
		HasNextPage:     hasNextPage,
		LanguageOptions: languageOptions,
		CurrentLang:     lang,
	}

	err = tmpl.Execute(w, data)
	if err != nil {
		http.Error(w, "Internal Server Error", http.StatusInternalServerError)
	}
}