feat: add method to turn into header

src/form.rs

@@ -203,4 +203,90 @@ impl FormData {
 
         Ok(nodes)
     }
+    /// Into an object with `std::io::Read`
+    pub fn into_reader(self) -> Result<impl ConcatRead + Send + Sync, crate::Error> {
+        let nodes = self.to_multipart()?;
+        let boundary = generate_boundary();
+        let mut readers: Vec<Box<dyn Read + Send + Sync>> = vec![];
+
+        for node in nodes {
+            // write a boundary
+            readers.push(Box::new(Cursor::new(b"--".to_vec())));
+            readers.push(Box::new(Cursor::new(boundary.clone())));
+            readers.push(Box::new(Cursor::new(b"\r\n".to_vec())));
+
+            match node {
+                Node::Part(part) => {
+                    // write the part's headers
+                    for header in part.headers.iter() {
+                        readers.push(Box::new(Cursor::new(
+                            header.name().as_bytes().to_vec().into_iter(),
+                        )));
+                        readers.push(Box::new(Cursor::new(b": ".to_vec())));
+                        readers.push(Box::new(Cursor::new(
+                            header.value_string().as_bytes().to_vec(),
+                        )));
+                        readers.push(Box::new(Cursor::new(b"\r\n".to_vec())));
+                    }
+
+                    // write the blank line
+                    readers.push(Box::new(Cursor::new(b"\r\n".to_vec())));
+
+                    // write the part's content
+                    readers.push(Box::new(Cursor::new(part.body)));
+                }
+                Node::File(filepart) => {
+                    // write the part's headers
+                    for header in filepart.headers.iter() {
+                        readers.push(Box::new(Cursor::new(header.name().as_bytes().to_vec())));
+                        readers.push(Box::new(Cursor::new(b": ".to_vec())));
+                        readers.push(Box::new(Cursor::new(
+                            header.value_string().as_bytes().to_vec(),
+                        )));
+                        readers.push(Box::new(Cursor::new(b"\r\n".to_vec())));
+                    }
+
+                    // write the blank line
+                    readers.push(Box::new(Cursor::new(b"\r\n".to_vec())));
+
+                    // write out the files's content
+                    let file = BufReader::new(
+                        File::open(&filepart.path).map_err(|_| crate::Error::InvalidFile)?,
+                    );
+                    readers.push(Box::new(file));
+                }
+                Node::Multipart((headers, subnodes)) => {
+                    // get boundary
+                    let boundary = get_multipart_boundary(&headers)?;
+
+                    // write the multipart headers
+                    for header in headers.iter() {
+                        readers.push(Box::new(Cursor::new(header.name().as_bytes().to_vec())));
+                        readers.push(Box::new(Cursor::new(b": ".to_vec())));
+                        readers.push(Box::new(Cursor::new(
+                            header.value_string().as_bytes().to_vec(),
+                        )));
+                        readers.push(Box::new(Cursor::new(b"\r\n".to_vec())));
+                    }
+
+                    // write the blank line
+                    readers.push(Box::new(Cursor::new(b"\r\n".to_vec())));
+
+                    // recurse
+                    multipart_to_read(boundary.clone(), subnodes)?;
+                }
+            }
+
+            // write a line terminator
+            readers.push(Box::new(Cursor::new(b"\r\n".to_vec())));
+        }
+
+        // write a final boundary
+        readers.push(Box::new(Cursor::new(b"--".to_vec())));
+        readers.push(Box::new(Cursor::new(boundary.clone())));
+        readers.push(Box::new(Cursor::new(b"--".to_vec())));
+
+        let reader = concat_reader::concat(readers);
+        Ok(reader)
+    }
 }