huge refactoring

app/handlers/http/errors.go

@@ -0,0 +1,15 @@
+package http
+
+import "fmt"
+
+type notAuthorizedContentTypeError struct{}
+
+func (e *notAuthorizedContentTypeError) Error() string {
+	return fmt.Sprintf("Accepted values for 'Content-Type': %s, %s, %s, %s", PDFContentType, HTMLContentType, OctetStreamContentType, MultipartFormDataContentType)
+}
+
+type notAuthorizedFileContentTypeError struct{}
+
+func (e *notAuthorizedFileContentTypeError) Error() string {
+	return fmt.Sprintf("Unable to detect a file 'Content-Type'")
+}

app/handlers/http/http.go

@@ -0,0 +1,60 @@
+package http
+
+import (
+	"net/http"
+	"os"
+	"strings"
+)
+
+type ContentType string
+
+const (
+	PDFContentType               ContentType = "application/pdf"
+	HTMLContentType              ContentType = "text/html"
+	OctetStreamContentType       ContentType = "application/octet-stream"
+	ZipContentType               ContentType = "application/zip"
+	MultipartFormDataContentType ContentType = "multipart/form-data"
+)
+
+func FindAuthorizedContentType(h http.Header) (ContentType, error) {
+	ct := findContentType(h.Get("Content-Type"), HTMLContentType, OctetStreamContentType, MultipartFormDataContentType)
+	if ct == "" {
+		return "", &notAuthorizedContentTypeError{}
+	}
+
+	return ct, nil
+}
+
+func SniffContentType(f *os.File) (ContentType, error) {
+	// only the first 512 bytes are used to sniff the content type.
+	buffer := make([]byte, 512)
+	n, err := f.Read(buffer)
+	if err != nil {
+		return "", err
+	}
+
+	// resets the read pointer.
+	f.Seek(0, 0)
+
+	// using n if size of buffer < 512 bytes.
+	ct := findContentType(http.DetectContentType(buffer[:n]), PDFContentType, HTMLContentType, OctetStreamContentType, ZipContentType)
+	if ct == "" {
+		return "", &notAuthorizedFileContentTypeError{}
+	}
+
+	return ct, nil
+}
+
+func findContentType(contentType string, contentTypes ...ContentType) ContentType {
+	for _, ct := range contentTypes {
+		if i := strings.IndexRune(contentType, ';'); i != -1 {
+			contentType = contentType[0:i]
+		}
+
+		if contentType == string(ct) {
+			return ct
+		}
+	}
+
+	return ""
+}