feat(index): add save and load functionality for Index using gob encoding/decoding

main.go

@@ -7,7 +7,7 @@ import (
 
 func main() {
 	// Initialize Index
-	index.CreateIndex()
+	index.InitIndex("default")
 
 	// Start HTTP Server
 	http.StartService()

pkg/index/index.go

@@ -2,6 +2,12 @@ package index
 
 import (
 	"bufio"
+	"bytes"
+	"encoding/gob"
+	"errors"
+	"fmt"
+	"log"
+	"os"
 	"strings"
 )
 
@@ -13,7 +19,40 @@ var Index InvertedIndex
 var DocFreq DocumentFrequency
 var Documents []string
 
-func CreateIndex() {
+type SavedIndex struct {
+	Index     InvertedIndex
+	DocFreq   DocumentFrequency
+	Documents []string
+}
+
+func InitIndex(name string) {
+	createIndex()
+
+	// check if index as file exists
+	// if not, create one and save it
+	indexFilePath := "/tmp/" + name + ".db"
+	if _, err := os.Stat(indexFilePath); errors.Is(err, os.ErrNotExist) {
+		f, err := os.Create(indexFilePath)
+		if err != nil {
+			log.Fatal(err)
+		}
+		defer f.Close()
+	} else {
+		var savedIndex SavedIndex
+
+		err = readStructFromFile(indexFilePath, &savedIndex)
+		if err != nil {
+			fmt.Println("Fehler beim Lesen:", err)
+			return
+		}
+
+		Index = savedIndex.Index
+		DocFreq = savedIndex.DocFreq
+		Documents = savedIndex.Documents
+	}
+}
+
+func createIndex() {
 	index := make(InvertedIndex)
 	docFreq := make(DocumentFrequency)
 	var docs []string
@@ -23,6 +62,21 @@ func CreateIndex() {
 	DocFreq = docFreq
 }
 
+func updateIndex(name string) {
+	savedIndex := SavedIndex{
+		Index:     Index,
+		DocFreq:   DocFreq,
+		Documents: Documents,
+	}
+
+	indexFilePath := "/tmp/" + name + ".db"
+	err := writeStructToFile(indexFilePath, savedIndex)
+	if err != nil {
+		fmt.Println("Fehler beim Schreiben:", err)
+		return
+	}
+}
+
 func AddDocToIndex(url string, content string) {
 	Documents = append(Documents, url)
 
@@ -46,4 +100,35 @@ func AddDocToIndex(url string, content string) {
 		}
 	}
 
+	updateIndex("default")
+}
+
+func writeStructToFile(filename string, data interface{}) error {
+	var buf bytes.Buffer
+	enc := gob.NewEncoder(&buf)
+	err := enc.Encode(data)
+	if err != nil {
+		return fmt.Errorf("error when encoding the structs: %w", err)
+	}
+
+	err = os.WriteFile(filename, buf.Bytes(), 0644)
+	if err != nil {
+		return fmt.Errorf("error when writing to the file: %w", err)
+	}
+	return nil
+}
+
+func readStructFromFile(filename string, data interface{}) error {
+	content, err := os.ReadFile(filename)
+	if err != nil {
+		return fmt.Errorf("error reading the file: %w", err)
+	}
+
+	buf := bytes.NewBuffer(content)
+	dec := gob.NewDecoder(buf)
+	err = dec.Decode(data)
+	if err != nil {
+		return fmt.Errorf("error when decoding the structs: %w", err)
+	}
+	return nil
 }