init

main.go

@@ -0,0 +1,104 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"strings"
+)
+
+// maxRedirects defines the maximum number of redirects to follow.
+const maxRedirects = 10
+
+// isValidURLAndFetchContent checks if the URL is valid and fetches its content.
+// It handles redirects and checks for the .sh extension.
+// It returns the content, a boolean indicating validity, and an error if any.
+func isValidURLAndFetchContent(url string, redirectCount int) ([]byte, bool, error) {
+	if redirectCount > maxRedirects {
+		return nil, false, fmt.Errorf("too many redirects")
+	}
+
+	// Check if the URL ends with .sh
+	if strings.HasSuffix(strings.ToLower(url), ".sh") {
+		// If it ends with .sh, try to download it directly
+		fmt.Printf("Attempting to download: %s\n", url)
+		resp, err := http.Get(url)
+		if err != nil {
+			return nil, false, fmt.Errorf("failed to download from %s: %w", url, err)
+		}
+		defer resp.Body.Close()
+
+		if resp.StatusCode >= 200 && resp.StatusCode < 300 {
+			content, err := io.ReadAll(resp.Body)
+			if err != nil {
+				return nil, false, fmt.Errorf("failed to read content from %s: %w", url, err)
+			}
+			return content, true, nil
+		}
+		// If status is not OK, but it ended with .sh, we treat it as a failed download for a .sh file.
+		return nil, false, fmt.Errorf("failed to download %s: status code %d", url, resp.StatusCode)
+	}
+
+	// If it doesn't end with .sh, check for redirect
+	fmt.Printf("URL %s does not end with .sh, checking for redirect...\n", url)
+	client := &http.Client{
+		CheckRedirect: func(req *http.Request, via []*http.Request) error {
+			return http.ErrUseLastResponse // Do not follow redirects automatically
+		},
+	}
+
+	resp, err := client.Get(url) // Using Get to be able to read body if needed, though Head is often used for just status/headers
+	if err != nil {
+		return nil, false, fmt.Errorf("failed to request %s: %w", url, err)
+	}
+	defer resp.Body.Close()
+
+	switch resp.StatusCode {
+	case http.StatusMovedPermanently, http.StatusFound, http.StatusSeeOther, http.StatusTemporaryRedirect, http.StatusPermanentRedirect:
+		location, err := resp.Location()
+		if err != nil {
+			return nil, false, fmt.Errorf("failed to get redirect location from %s: %w", url, err)
+		}
+		fmt.Printf("Redirected to: %s\n", location.String())
+		return isValidURLAndFetchContent(location.String(), redirectCount+1)
+	default:
+		// Not a .sh and not a redirect status code
+		return nil, false, fmt.Errorf("URL %s does not end in .sh and did not redirect (status: %d)", url, resp.StatusCode)
+	}
+}
+
+// hasShebang checks if the content starts with "#!".
+func hasShebang(content []byte) bool {
+	return len(content) >= 2 && content[0] == '#' && content[1] == '!'
+}
+
+func main() {
+	if len(os.Args) < 2 {
+		fmt.Println("Usage: go run script_downloader.go <URL>")
+		os.Exit(1)
+	}
+	initialURL := os.Args[1]
+
+	content, isValid, err := isValidURLAndFetchContent(initialURL, 0)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Error: %v\n", err)
+		os.Exit(1)
+	}
+
+	if !isValid {
+		// This case should ideally be covered by errors from isValidURLAndFetchContent
+		fmt.Fprintf(os.Stderr, "The provided URL is invalid or does not point to a valid .sh file after redirects.\n")
+		os.Exit(1)
+	}
+
+	if hasShebang(content) {
+		fmt.Println("Valid script found. Content:")
+		fmt.Println("--- SCRIPT START ---")
+		fmt.Print(string(content))
+		fmt.Println("--- SCRIPT END ---")
+	} else {
+		fmt.Fprintf(os.Stderr, "Error: The file from URL %s does not start with a shebang '#!'.\n", initialURL)
+		os.Exit(1)
+	}
+}