api-cds-search/cmd/search/search.go

package search

import (
	"errors"
	"fmt"
	"net/http"
	"sap-cds-search/cmd/model"
	"sap-cds-search/cmd/ui"
	"slices"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/lithammer/fuzzysearch/fuzzy"
)

type fuzzyResult struct {
	CDSViewTechnicalName string
	hits                 int
	averageDistance      float32
	score                float32
}

type resultBuffer struct {
	createdAt time.Time
	hits      int
	mu        sync.Mutex
	results   []fuzzyResult
}

const pageStep = 12

var (
	ErrNoBuffer  = errors.New("no buffer")
	ErrNoResults = errors.New("no results")
)

var searchTargets map[string][]string = make(map[string][]string)
var resultsBuffer map[string]*resultBuffer = make(map[string]*resultBuffer)

func Load() error {
	keywords, err := model.GetKeywordsModel()
	if err != nil {
		return err
	}
	for _, keyword := range *keywords {
		table := searchTargets[keyword.CDSViewTechnicalName]
		table = append(table, keyword.Keyword)
		searchTargets[keyword.CDSViewTechnicalName] = table
	}

	ticker := time.NewTicker(5 * time.Minute)

	go func() {
		for {
			select {
			case <-ticker.C:
				ClearOldBuffers()
			}
		}
	}()

	return nil
}

func GetSearchTerm(r *http.Request) string {
	return strings.ToLower(r.URL.Query().Get("q"))
}

func GetPage(r *http.Request) int {
	page, _ := strconv.Atoi(r.URL.Query().Get("p"))
	if page < 0 {
		page = 0
	}
	return page
}

func GetBuffer(searchTerm string) (*resultBuffer, error) {
	buffer, exists := resultsBuffer[searchTerm]

	if !exists {
		return nil, ErrNoBuffer
	}

	return buffer, nil
}

func BuildBuffer(searchTerm string) error {
	if searchTerm == "" {
		return ErrNoResults
	}

	splitSearchTerms := strings.Split(searchTerm, " ")

	splitSearchTerms = append(splitSearchTerms, searchTerm)
	splitSearchTerms = append(splitSearchTerms, strings.ReplaceAll(searchTerm, " ", searchTerm))

	var fuzzyResults []fuzzyResult

	for viewName, targets := range searchTargets {
		totalHits := 0
		var totalDistance float32
		for i, splitSearchTerm := range splitSearchTerms {
			ranks := fuzzy.RankFindFold(splitSearchTerm, targets)

			hits := len(ranks)
			if hits == 0 {
				if i < len(splitSearchTerm)-3 {
					totalDistance += 500
				}
				continue
			}

			totalHits += hits

			var averageDistance float32 = 0
			for _, rank := range ranks {
				averageDistance += float32(rank.Distance)
			}

			totalDistance += averageDistance / float32(hits)
		}

		if totalHits > 0 {
			fuzzyResults = append(fuzzyResults, fuzzyResult{
				CDSViewTechnicalName: viewName,
				hits:                 totalHits,
				averageDistance:      totalDistance,
				score:                totalDistance / float32(totalHits),
			})
		}
	}

	hits := len(fuzzyResults)
	if hits == 0 {
		return ErrNoResults
	}

	slices.SortFunc(fuzzyResults, func(a, b fuzzyResult) int {
		if a.score > b.score {
			return 1
		} else if a.score < b.score {
			return -1
		}
		return 0
	})

	resultsBuffer[searchTerm] = &resultBuffer{
		createdAt: time.Now(),
		hits:      hits,
		results:   fuzzyResults,
	}

	return nil
}

func HandleSearch(w http.ResponseWriter, r *http.Request) {
	searchTerm := GetSearchTerm(r)

	buffer, err := GetBuffer(searchTerm)
	if err != nil {
		err := BuildBuffer(searchTerm)
		if err != nil {
			err := ui.Template.ExecuteTemplate(w, "search-placeholder-no-result", nil)
			if err != nil {
				fmt.Println(err)
			}
			return
		}
		buffer, _ = GetBuffer(searchTerm)
	}

	buffer.mu.Lock()
	defer buffer.mu.Unlock()

	page := GetPage(r)

	maxPage := (buffer.hits / pageStep) - 1
	if page+1 > maxPage {
		page = maxPage
	}

	resultsModel := model.NewResultsModel()
	for i := page * pageStep; i < page*pageStep+pageStep; i++ {
		result := buffer.results[i]
		cdsView, err := model.GetCDSViewModel(result.CDSViewTechnicalName)
		if err != nil {
			fmt.Println(err)
			continue
		}

		resultsModel.AppendResultsModelViews(cdsView)
	}

	resultsModel.SearchTerm = searchTerm
	resultsModel.CurrentPage = page
	resultsModel.MaxPage = maxPage

	err = ui.Template.ExecuteTemplate(w, "results", resultsModel)
	if err != nil {
		fmt.Println(err)
		return
	}
}

func ClearOldBuffers() {
	for key, buffer := range resultsBuffer {
		if time.Since(buffer.createdAt) >= time.Minute*10 {
			buffer.mu.Lock()
			delete(resultsBuffer, key)
			buffer.mu.Unlock()
		}
	}
}