commit 4f8fe007ad7dea84da1375a5d89962cadcb5d466
Author: Kaustubh Maske Patil <kaustubh299792458@gmail.com>
Date:   Tue Jul 2 14:55:33 2024 +0530

    Initial commit

diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..110d2d9
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,3 @@
+module git.kaustubh.page/fun-with-files
+
+go 1.22.4
diff --git a/main.go b/main.go
new file mode 100644
index 0000000..d3dd8fa
--- /dev/null
+++ b/main.go
@@ -0,0 +1,133 @@
+package main
+
+import (
+	"crypto/rand"
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"path/filepath"
+	"regexp"
+	"strings"
+)
+
+var uploadDir string
+
+func initConfig() {
+	if envUploadDir := os.Getenv("UPLOAD_DIR"); envUploadDir != "" {
+		uploadDir = envUploadDir
+	} else {
+		uploadDir = "./uploads/"
+	}
+}
+
+func main() {
+	initConfig()
+
+	if len(os.Args) < 2 {
+		fmt.Println("Usage: go run main.go <port>")
+		return
+	}
+
+	port := os.Args[1]
+
+	uploadEndpoint := "upload"
+	if len(os.Args) >= 3 {
+		uploadEndpoint = os.Args[2]
+	}
+
+	http.HandleFunc(fmt.Sprintf("/%s/", uploadEndpoint), uploadHandler)
+	fmt.Printf("Server started at :%s\n", port)
+	fmt.Printf("Endpoint: /%s/\n", uploadEndpoint)
+	fmt.Printf("Upload Directory: %s\n", uploadDir)
+	http.ListenAndServe(":"+port, nil)
+}
+
+func uploadHandler(w http.ResponseWriter, r *http.Request) {
+	if r.Method != http.MethodPost {
+		http.Error(w, "Only POST method is allowed", http.StatusMethodNotAllowed)
+		return
+	}
+
+	// Parse the multipart form
+	err := r.ParseMultipartForm(10 << 20) // 10 MB
+	if err != nil {
+		http.Error(w, "Error parsing form data", http.StatusBadRequest)
+		return
+	}
+
+	file, handler, err := r.FormFile("file")
+	if err != nil {
+		http.Error(w, "Error retrieving the file", http.StatusBadRequest)
+		return
+	}
+	defer file.Close()
+
+	// Sanitize the filename
+	sanitizedFilename := sanitizeFilename(handler.Filename)
+	if sanitizedFilename == "" {
+		sanitizedFilename = generateRandomFilename()
+	}
+
+	filePath := filepath.Join(uploadDir, sanitizedFilename)
+
+	// Ensure unique filename
+	for fileExists(filePath) {
+		sanitizedFilename = generateRandomFilename()
+		filePath = filepath.Join(uploadDir, sanitizedFilename)
+	}
+
+	// Create the uploads directory if it doesn't exist
+	if _, err := os.Stat(uploadDir); os.IsNotExist(err) {
+		os.MkdirAll(uploadDir, os.ModePerm)
+	}
+
+	// Save the file
+	out, err := os.Create(filePath)
+	if err != nil {
+		http.Error(w, "Unable to save the file", http.StatusInternalServerError)
+		return
+	}
+	defer out.Close()
+
+	_, err = io.Copy(out, file)
+	if err != nil {
+		http.Error(w, "Error saving the file", http.StatusInternalServerError)
+		return
+	}
+
+	w.Write([]byte("File uploaded successfully"))
+}
+
+func sanitizeFilename(filename string) string {
+	// Allow only alphanumeric, dashes, underscores, and dots
+	re := regexp.MustCompile(`[^a-zA-Z0-9._-]`)
+	sanitized := re.ReplaceAllString(filename, "")
+	sanitized = strings.TrimLeft(sanitized, ".")
+
+	return sanitized
+}
+
+func generateRandomFilename() string {
+	const letters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
+	b := make([]byte, 16)
+	for i := range b {
+		b[i] = letters[randInt(len(letters))]
+	}
+	return string(b) + ".file"
+}
+
+func randInt(n int) int {
+	b := make([]byte, 1)
+	rand.Read(b)
+	return int(b[0]) % n
+}
+
+func fileExists(filename string) bool {
+	info, err := os.Stat(filename)
+	if os.IsNotExist(err) {
+		return false
+	}
+	return !info.IsDir()
+}
+