mq/error-reporting: Support error reporting.

Some changes to nse/client will be necessary.

* Makefile.am
  (modules): Add new module.
  (SCM_TESTS): Add new test.
* doc/scheme-gnunet.tm
  (Error handler): Suggest reporting errors.
  (Error reporting): New section.
* gnu/gnunet/mq/error-reporting.scm: New module.
* tests/error-reporting.scm: New tests.

1 files changed, 108 insertions, 0 deletions

diff --git a/gnu/gnunet/mq/error-reporting.scm b/gnu/gnunet/mq/error-reporting.scm
new file mode 100644
index 0000000..41f4f73
--- /dev/null
+++ b/gnu/gnunet/mq/error-reporting.scm
@@ -0,0 +1,108 @@
+;; This file is part of scheme-GNUnet, a partial Scheme port of GNUnet.
+;; Copyright (C) 2021 Maxime Devos <maximedevos@telenet.be>
+;;
+;; scheme-GNUnet is free software: you can redistribute it and/or modify it
+;; under the terms of the GNU Affero General Public License as published
+;; by the Free Software Foundation, either version 3 of the License,
+;; or (at your option) any later version.
+;;
+;; scheme-GNUnet is distributed in the hope that it will be useful, but
+;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+;; Affero General Public License for more details.
+;;
+;; You should have received a copy of the GNU Affero General Public License
+;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
+;;
+;; SPDX-License-Identifier: AGPL3.0-or-later
+
+;; Summary: Reporting errors from message queues.
+;;
+;; By default, errors are reported to the @code{(current-error-port)},
+;; but this is customisable by parameterising
+;; @code{textual-error-reporting-port}.
+;;
+;; For non-textual error reporting, @code{error-reporter} can be parameterised.
+;; This library is only for _reporting_ errors.  What happens after reporting,
+;; is up to the caller.
+(define-library (gnu gnunet mq error-reporting)
+  (export format-error-textually
+          report-error-textually
+          textual-error-reporting-port
+          error-reporter
+          report-error)
+  (import (only (guile)
+                format gettext ngettext current-error-port)
+          (only (srfi srfi-39)
+                make-parameter)
+          (only (rnrs base)
+                begin define case else apply car if lambda cons))
+  (begin
+    ;; TODO: set up translations
+    (define (G_ message)
+      (gettext message "scheme-gnunet"))
+
+    (define (format-message-type type) ; XXX
+      type)
+
+    (define (format-error-textually key . arguments)
+      "Return a textual representation of the error @code{key . arguments},
+translated for the current locale when possible."
+      (case key
+        ((connection:connected)
+         (G_ "the connection to the server has been established"))
+        ((connection:interrupted)
+         (G_ "the connection has been closed before it could be established"))
+        ((input:regular-end-of-file)
+         (G_ "the connection has been broken"))
+        ((input:premature-end-of-file)
+         (G_ "the connection has been broken while there was still some data to read"))
+        ((input:overly-small)
+         (apply (lambda (type size)
+                  (if type
+                      (format
+                       #f
+                       (G_ "a message of type ~a and size ~a was smaller than the minimal message size")
+                       (format-message-type type)
+                       size)
+                      (format
+                       #f
+                       (G_ "a message of size ~a was smaller than the minimal message size")
+                       size)))
+                arguments))
+        ((logic:no-handler)
+         (format
+          #f
+          (G_ "no message handler for ~a was found, but a message of that type was received")
+          (format-message-type (car arguments))))
+        ((logic:ill-formed)
+         (format
+          #f
+          (G_ "an ill-formed message of type ~a was received")
+          (format-message-type (car arguments))))
+        (else
+         (format
+          #f
+          (G_ "an unknown error ‘~s’ was encountered")
+          (cons key arguments)))))
+
+    (define (report-error-textually port key . arguments)
+      "Write a textual representation of the error @code{key . arguments} to
+the output port @var{port}, translated for the current locale if possible."
+      (format port "Scheme-GNUnet: ~a~%"
+              (apply format-error-textually key arguments)))
+
+    (define textual-error-reporting-port
+      (make-parameter #f))
+      
+    (define error-reporter
+      (make-parameter
+       (lambda (key . arguments)
+         (define t (textual-error-reporting-port))
+         (if t
+             (apply report-error-textually t key arguments)
+             (apply report-error-textually (current-error-port) key arguments)))))
+
+    (define (report-error key . arguments)
+      "Report the error @code{key . arguments}."
+      (apply (error-reporter) key arguments))))