FU: Add JSON reading & writing methods

FU.pm

@@ -637,7 +637,10 @@ sub headers { $FU::REQ->{hdr} }
 sub ip { $FU::REQ->{ip} }
 
 sub _getfield($data, @a) {
-    return $data->{$a[0]} if @a == 1 && !ref $a[0];
+    if (@a == 1 && !ref $a[0]) {
+        fu->error(400, "Expected top-level to be a hash") if ref $data ne 'HASH';
+        return $data->{$a[0]};
+    }
     require FU::Validate;
     my $schema = FU::Validate->compile(@a > 1 ? { keys => {@a} } : $a[0]);
     my $res = eval { $schema->validate($data) };
@@ -652,6 +655,15 @@ sub query {
     _getfield $FU::REQ->{qs_parsed}, @_;
 }
 
+sub json {
+    shift;
+    $FU::REQ->{json} ||= eval {
+        FU::Util::json_parse($FU::REQ->{data}, utf8 => 1)
+    } || fu->error(400, "JSON parse error: $@");
+    return $FU::REQ->{json} if !@_;
+    _getfield $FU::REQ->{json}, @_;
+}
+
 sub formdata {
     shift;
     $FU::REQ->{formdata} ||= eval {
@@ -715,6 +727,12 @@ sub set_header($, $hdr, $val=undef) {
     $FU::REQ->{reshdr}{ lc $hdr } = $val;
 }
 
+sub send_json($, $data) {
+    fu->set_header('content-type', 'application/json');
+    fu->set_body(FU::Util::json_format($data, canonical => 1, utf8 => 1));
+    fu->done;
+}
+
 sub send_file($, $root, $path) {
     # This also catches files with '..' somewhere in the middle of the name.
     # Let's just disallow that to simplify this check, I'd err on the side of
@@ -1242,9 +1260,12 @@ Parse, validate and return multiple query parameters.
   # Or, more concisely:
   my $data = fu->query(a => {anybool => 1}, b => {});
 
-=item fu->formdata($name)
+=item fu->json(@args)
 
-=item fu->formdata($schema)
+Like C<< fu->query() >> but parses the request body as JSON. Returns the
+decoded JSON value if C<@args> is empty.
+
+=item fu->formdata(@args)
 
 Like C<< fu->query() >> but returns data from the POST request body. This
 method only supports form data encoded as C<application/x-www-form-urlencoded>,
@@ -1253,13 +1274,11 @@ use C<< fu->multipart >> instead.
 
 =item fu->multipart
 
-Parse the request body as C<multipart/form-data> and return an array of fields.
-Refer to L<FU::MultipartFormData> for more information.
+Parse the request body as C<multipart/form-data> and return an array of field
+objects.  Refer to L<FU::MultipartFormData> for more information.
 
 =back
 
-I<TODO:> Support JSON bodies.
-
 I<TODO:> Cookie parsing.
 
 
@@ -1321,6 +1340,14 @@ templating system or L<FU::XMLWriter>:
       };
   });
 
+=item fu->send_json($data)
+
+Encode C<$data> as JSON (using C<json_format> in L<FU::Util>), set an
+appropriate C<Content-Type> header and send it to the client. Calls C<<
+fu->done >>.
+
+I<TODO:> Support schema-based normalization.
+
 =item fu->send_file($root, $path)
 
 If a file identified by C<"$root/$path"> exists, set that as response and call
@@ -1374,8 +1401,6 @@ one of the following status codes or an alias:
 
 I<TODO:> Setting cookies.
 
-I<TODO:> JSON output.
-
 
 =head2 Running the Site