refactor: Improve 4chan downloader with better error handling and resource management

- Replace log.Fatal() with proper error returns for better control flow - Add type safety with dedicated structs instead of interface{} maps - Implement proper HTTP client with timeout configuration - Fix goroutine closure variable capture issues - Add input validation for URL format and board extraction - Ensure destination directory exists before writing files - Improve error messages with context and proper error wrapping - Add resource cleanup with defer statements for HTTP responses - Separate concerns into dedicated functions for better organization - Use filepath.Join for cross-platform path handling - Add comprehensive logging throughout the application This refactoring makes the downloader more robust, maintainable, and production-ready while preserving all original functionality.
2025-10-03 19:33:16 +02:00
parent 07224f9258
commit acaccb8cdd
1 changed files with 163 additions and 90 deletions
--- a/main.go
+++ b/main.go
@@ -8,130 +8,203 @@ import (
 	"log"
 	"net/http"
 	"os"
-	"strconv"
+	"path/filepath"
 	"strings"
 	"sync"
+	"time"
 )
-func writeDataToDisk(dest *string, board string, verlog *bool, post map[string]interface{}, cdnresbody []byte) {
-	// Save the mediadata to file
-	err := os.WriteFile(*dest + "/" + board + "-" + strconv.Itoa(int(post["tim"].(float64))) + post["ext"].(string), cdnresbody, 0664 )
-	if err != nil {
-		log.Fatal(err)
-	} else if (*verlog) {
-		log.Println("Successfully wrote image/video data to disk")
-	}
+
+// Global HTTP client with timeout
+var httpClient = &http.Client{
+	Timeout: 30 * time.Second,
 }

-func getPostData(post map[string]interface{}, board string, verlog *bool) []byte {
-	// Check if post contains media (Video or Image)
-	if post["ext"] != nil {
-		cdnurlstr := "https://i.4cdn.org/" + board + "/" + strconv.Itoa(int(post["tim"].(float64))) + post["ext"].(string)
-			
-		// Requesting the media from CDN
-		cdnres, err := http.Get(cdnurlstr)
-		if err != nil {
-			log.Fatal(err)
-		}
-		
-		// Check if respons was valid
-		if cdnres.StatusCode > 299 {
-			log.Fatalf("Response failed with status code: %d and\n", cdnres.StatusCode)
-		} else if (*verlog) {
-			log.Println("Got image/video " + strconv.Itoa(int(post["tim"].(float64))) + post["ext"].(string) + " data")
-		}
-		
-		// Read data form respons
-		cdnresbody, err := io.ReadAll(cdnres.Body)
-		cdnres.Body.Close()
-		if err != nil {
-			log.Fatal(err)
-		} else if (*verlog) {
-			log.Println("Successfully got data from responds body")
-		}
-		return cdnresbody
+// PostData represents a 4chan post
+type PostData struct {
+	No  float64 `json:"no"`
+	Tim float64 `json:"tim"`
+	Ext string  `json:"ext"`
+}

-	} else if (*verlog) {
-		log.Println("Post " + strconv.Itoa(int(post["no"].(float64))) + " didn't include a image or video")
+// ThreadData represents the JSON structure from 4chan API
+type ThreadData struct {
+	Posts []PostData `json:"posts"`
+}
+
+func writeDataToDisk(dest string, board string, verlog bool, post PostData, cdnresbody []byte) error {
+	if cdnresbody == nil {
+		return fmt.Errorf("no data to write")
+	}
+
+	filename := fmt.Sprintf("%s-%d%s", board, int64(post.Tim), post.Ext)
+	filepath := filepath.Join(dest, filename)
+
+	err := os.WriteFile(filepath, cdnresbody, 0664)
+	if err != nil {
+		return fmt.Errorf("failed to write file %s: %w", filepath, err)
+	}
+
+	if verlog {
+		log.Printf("Successfully wrote image/video data to disk: %s", filename)
 	}
 	return nil
 }

-
-func main ()  {
-	// Setting up command flags
-	wdpath, _ := os.Getwd();
-
-	url := flag.String("u", "", "The url of the 4chan thread")
-	
-	dest := flag.String("o", wdpath, "Target dir of the conntent")
-
-	verlog := flag.Bool("v", false, "Set logging to verbose")
-	
-	flag.Parse()
-	
-	// Check if flags are valid
-	if *url == "" {
-		fmt.Println("no thread URL provided")
-		fmt.Println("use the -u=<Thread URL> flag to provid URL")
-		os.Exit(1)
+func getPostData(post PostData, board string, verlog bool) ([]byte, error) {
+	if post.Ext == "" {
+		if verlog {
+			log.Printf("Post %d didn't include an image or video", int64(post.No))
+		}
+		return nil, nil
 	}

-	// Getting the boardname
-	board := strings.Split(*url, "/")[3]
+	cdnurlstr := fmt.Sprintf("https://i.4cdn.org/%s/%d%s", board, int64(post.Tim), post.Ext)

-	// Get thread info from API
-	res, err := http.Get(*url + ".json")
+	cdnres, err := httpClient.Get(cdnurlstr)
 	if err != nil {
-		log.Fatal(err)
-	} else {
+		return nil, fmt.Errorf("failed to fetch media from %s: %w", cdnurlstr, err)
+	}
+	defer cdnres.Body.Close()
+
+	if cdnres.StatusCode > 299 {
+		return nil, fmt.Errorf("response failed with status code: %d for %s", cdnres.StatusCode, cdnurlstr)
+	}
+
+	if verlog {
+		log.Printf("Got image/video %d%s data", int64(post.Tim), post.Ext)
+	}
+
+	cdnresbody, err := io.ReadAll(cdnres.Body)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read response body: %w", err)
+	}
+
+	if verlog {
+		log.Println("Successfully got data from response body")
+	}
+
+	return cdnresbody, nil
+}
+
+func validateURL(url string) error {
+	if url == "" {
+		return fmt.Errorf("no thread URL provided")
+	}
+
+	if !strings.HasPrefix(url, "https://") && !strings.HasPrefix(url, "http://") {
+		return fmt.Errorf("invalid URL format")
+	}
+
+	parts := strings.Split(url, "/")
+	if len(parts) < 4 {
+		return fmt.Errorf("invalid thread URL format")
+	}
+
+	return nil
+}
+
+func extractBoard(url string) string {
+	parts := strings.Split(url, "/")
+	if len(parts) >= 4 {
+		return parts[3]
+	}
+	return ""
+}
+
+func fetchThreadData(url string, verlog bool) (*ThreadData, error) {
+	apiURL := url + ".json"
+
+	res, err := httpClient.Get(apiURL)
+	if err != nil {
+		return nil, fmt.Errorf("failed to fetch thread data from %s: %w", apiURL, err)
+	}
+	defer res.Body.Close()
+
+	if res.StatusCode > 299 {
+		return nil, fmt.Errorf("API response failed with status code: %d", res.StatusCode)
+	}
+
+	if verlog {
 		log.Println("Got thread data")
 	}

-	// Check if API response is valid
-	if res.StatusCode > 299 {
-		log.Fatalf("Response failed with status code: %d and\n", res.StatusCode)
-	} else if (*verlog) {
-		log.Println("API response was ok")
-	}
-	
-	//Geting the data from the response
 	resbody, err := io.ReadAll(res.Body)
-	res.Body.Close()
 	if err != nil {
-		log.Fatal(err)
-	} else if (*verlog) {
+		return nil, fmt.Errorf("failed to read API response body: %w", err)
+	}
+
+	if verlog {
 		log.Println("Got body of API response")
 	}
-	
-	// Var to save the JSON data 
-	var jdata map[string]interface{}

-	//Unmarshaling the API JSON respons
+	var jdata ThreadData
 	if err := json.Unmarshal(resbody, &jdata); err != nil {
-		log.Fatalln(err)
-	} else if (*verlog) {
-		log.Println("Unmarsheled API responsebody")	
+		return nil, fmt.Errorf("failed to unmarshal API response: %w", err)
+	}
+
+	if verlog {
+		log.Println("Unmarshaled API response body")
+	}
+
+	return &jdata, nil
+}
+
+func main() {
+	// Setting up command flags
+	wdpath, err := os.Getwd()
+	if err != nil {
+		log.Fatalf("Failed to get working directory: %v", err)
+	}
+
+	url := flag.String("u", "", "The url of the 4chan thread")
+	dest := flag.String("o", wdpath, "Target dir of the content")
+	verlog := flag.Bool("v", false, "Set logging to verbose")
+
+	flag.Parse()
+
+	// Validate flags
+	if err := validateURL(*url); err != nil {
+		log.Fatalf("Invalid URL: %v", err)
+	}
+
+	// Getting the boardname
+	board := extractBoard(*url)
+	if board == "" {
+		log.Fatal("Failed to extract board name from URL")
+	}
+
+	// Fetch thread data
+	jdata, err := fetchThreadData(*url, *verlog)
+	if err != nil {
+		log.Fatalf("Failed to fetch thread data: %v", err)
+	}
+
+	// Ensure destination directory exists
+	if err := os.MkdirAll(*dest, 0755); err != nil {
+		log.Fatalf("Failed to create destination directory: %v", err)
 	}
-	

 	var wg sync.WaitGroup

 	// Iterating the posts from JSON data
-	for _, v := range jdata["posts"].([]interface{}) {
-		post := v.(map[string]interface{})
-	
+	for _, post := range jdata.Posts {
 		wg.Add(1)
-		
-		go func() {
+
+		go func(post PostData) {
 			defer wg.Done()
-			if postdata := getPostData(post, board, verlog); postdata != nil {
-				writeDataToDisk(dest, board, verlog, post, postdata)
+
+			if postdata, err := getPostData(post, board, *verlog); err != nil {
+				log.Printf("Error processing post %d: %v", int64(post.No), err)
+				return
+			} else if postdata != nil {
+				if err := writeDataToDisk(*dest, board, *verlog, post, postdata); err != nil {
+					log.Printf("Error writing post %d to disk: %v", int64(post.No), err)
+				}
 			}
-		}()	
+		}(post)
 	}

 	wg.Wait()

 	log.Println("DONE!!!")
-
 }