package search

import (
	"searchEngine/analyzer"
	"searchEngine/index"
)

func Search(idx *index.InvertedIndex, query string) []string {
	tokenizedQuery := analyzer.ProcessText(query)

	if len(tokenizedQuery) == 0 {
		return nil
	}

	idx.Mu.RLock()
	defer idx.Mu.RUnlock()

	firstToken := tokenizedQuery[0]
	baseIDs, exists := idx.Data[firstToken]
	if !exists {
		return nil
	}

	intersection := make([]index.Posting, len(baseIDs))
	copy(intersection, baseIDs)

	for i := 1; i < len(tokenizedQuery); i++ {
		token := tokenizedQuery[i]

		nextIDs, exists := idx.Data[token]
		if !exists {
			return nil
		}

		lookup := make(map[int]struct{})
		for _, id := range nextIDs {
			lookup[id.DocId] = struct{}{}
		}

		var filtered []index.Posting
		for _, id := range intersection {
			if _, found := lookup[id.DocId]; found {
				filtered = append(filtered, id)
			}
		}

		intersection = filtered

	}
	var results []string
	for _, id := range intersection {
		if title, exists := idx.DocNames[id.DocId]; exists {
			results = append(results, title)
		}
	}

	return results
}