net.http: add post_multipart_form function (#11511)

vlib/net/http/http.v

@@ -80,6 +80,22 @@ pub fn post_form(url string, data map[string]string) ?Response {
 	)
 }
 
+pub struct PostMultipartFormConfig {
+	form  map[string]string
+	files map[string][]FileData
+}
+
+// post_multipart_form sends a POST HTTP request to the URL with multipart form data
+pub fn post_multipart_form(url string, conf PostMultipartFormConfig) ?Response {
+	body, boundary := multipart_form_body(conf.form, conf.files)
+	return fetch(
+		method: .post
+		url: url
+		header: new_header(key: .content_type, value: 'multipart/form-data; boundary="$boundary"')
+		data: body
+	)
+}
+
 // put sends a PUT HTTP request to the URL with a string data
 pub fn put(url string, data string) ?Response {
 	return fetch(

vlib/net/http/request.v

@@ -6,6 +6,7 @@ module http
 import io
 import net
 import net.urllib
+import rand
 import strings
 import time
 
@@ -261,6 +262,43 @@ struct MultiplePathAttributesError {
 	code int
 }
 
+// multipart_form_body converts form and file data into a multipart/form
+// HTTP request body. It is the inverse of parse_multipart_form. Returns
+// (body, boundary).
+// NB: Form keys should not contain quotes
+fn multipart_form_body(form map[string]string, files map[string][]FileData) (string, string) {
+	alpha_numeric := 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789'
+	boundary := rand.string_from_set(alpha_numeric, 64)
+
+	mut sb := strings.new_builder(1024)
+	for name, value in form {
+		sb.write_string('\r\n--')
+		sb.write_string(boundary)
+		sb.write_string('\r\nContent-Disposition: form-data; name="')
+		sb.write_string(name)
+		sb.write_string('"\r\n\r\n')
+		sb.write_string(value)
+	}
+	for name, fs in files {
+		for f in fs {
+			sb.write_string('\r\n--')
+			sb.write_string(boundary)
+			sb.write_string('\r\nContent-Disposition: form-data; name="')
+			sb.write_string(name)
+			sb.write_string('"; filename="')
+			sb.write_string(f.filename)
+			sb.write_string('"\r\nContent-Type: ')
+			sb.write_string(f.content_type)
+			sb.write_string('\r\n\r\n')
+			sb.write_string(f.data)
+		}
+	}
+	sb.write_string('\r\n--')
+	sb.write_string(boundary)
+	sb.write_string('--')
+	return sb.str(), boundary
+}
+
 pub fn parse_multipart_form(body string, boundary string) (map[string]string, map[string][]FileData) {
 	sections := body.split(boundary)
 	fields := sections[1..sections.len - 1]
@@ -275,8 +313,7 @@ pub fn parse_multipart_form(body string, boundary string) (map[string]string, ma
 		name := disposition['name'] or { continue }
 		// Parse files
 		// TODO: filename*
-		if 'filename' in disposition {
-			filename := disposition['filename']
+		if filename := disposition['filename'] {
 			// Parse Content-Type header
 			if lines.len == 1 || !lines[1].to_lower().starts_with('content-type:') {
 				continue

vlib/net/http/request_test.v

@@ -128,6 +128,24 @@ ${contents[1]}
 	}
 }
 
+fn test_multipart_form_body() {
+	files := {
+		'foo': [FileData{
+			filename: 'bar.v'
+			content_type: 'application/octet-stream'
+			data: 'baz'
+		}]
+	}
+	form := {
+		'fooz': 'buzz'
+	}
+
+	body, boundary := multipart_form_body(form, files)
+	parsed_form, parsed_files := parse_multipart_form(body, boundary)
+	assert parsed_files == files
+	assert parsed_form == form
+}
+
 fn test_parse_large_body() ? {
 	body := 'A'.repeat(101) // greater than max_bytes
 	req := 'GET / HTTP/1.1\r\nContent-Length: $body.len\r\n\r\n$body'