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diff --git a/src/backend/taler-merchant-httpd_templating.c b/src/backend/taler-merchant-httpd_templating.c
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+/*
+ This file is part of TALER
+ Copyright (C) 2020 Taler Systems SA
+
+ TALER is free software; you can redistribute it and/or modify it under the
+ terms of the GNU General Public License as published by the Free Software
+ Foundation; either version 3, or (at your option) any later version.
+
+ TALER 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 General Public License for more details.
+
+ You should have received a copy of the GNU General Public License along with
+ TALER; see the file COPYING. If not, see <http://www.gnu.org/licenses/>
+*/
+/**
+ * @file merchant/backend/taler-merchant-httpd_templating.c
+ * @brief logic to load and complete HTML templates
+ * @author Christian Grothoff
+ */
+#include "platform.h"
+#include <gnunet/gnunet_util_lib.h>
+#include <taler/taler_mhd_lib.h>
+#include "taler-merchant-httpd_templating.h"
+#include "../mustach/mustach.h"
+#include <gnunet/gnunet_mhd_compat.h>
+
+
+/**
+ * Entry in a key-value array we use to cache templates.
+ */
+struct TVE
+{
+ /**
+ * A name, used as the key. NULL for the last entry.
+ */
+ char *name;
+
+ /**
+ * Language the template is in.
+ */
+ char *lang;
+
+ /**
+ * 0-terminated (!) file data to return for @e name and @e lang.
+ */
+ char *value;
+
+};
+
+
+/**
+ * Array of templates loaded into RAM.
+ */
+static struct TVE *loaded;
+
+/**
+ * Length of the #loaded array.
+ */
+static unsigned int loaded_length;
+
+
+/**
+ * Function called by Mustach to enter the section @a name.
+ * As we do not support sections, we always return 0.
+ *
+ * @param cls a `struct KVC[]` array
+ * @param name section to enter
+ * @return 0 (do not enter)
+ */
+static int
+m_enter (void *cls, const char *name)
+{
+ (void) cls;
+ (void) name;
+ return 0;
+}
+
+
+/**
+ * Function called by mustach to activate the next item in the
+ * section. Does nothing, as we do not support sections.
+ *
+ * @param cls a `struct KVC[]` array
+ * @return 0 (no next item to activate)
+ */
+static int
+m_next (void *cls)
+{
+ (void) cls;
+ return 0;
+}
+
+
+/**
+ * Function called by Mustach to leave the current section.
+ * As we do not support sections, we should never be called.
+ *
+ * @param cls a `struct KVC[]` array
+ * @return 0 (not documented by mustach)
+ */
+static int
+m_leave (void *cls)
+{
+ GNUNET_assert (0);
+ return 0;
+}
+
+
+/**
+ * Return the value of @a name in @a sbuf.
+ *
+ * @param cls a `struct KVC[]` array
+ * @param name the value to lookup
+ * @param[out] sbuf where to return the data
+ * @return mustach-defined status code
+ */
+static int
+m_get (void *cls,
+ const char *name,
+ struct mustach_sbuf *sbuf)
+{
+ const struct KVC *kvc = cls;
+
+ for (unsigned int i = 0; NULL != kvc[i].name; i++)
+ {
+ if (0 == strcmp (name,
+ kvc[i].name))
+ {
+ sbuf->value = kvc[i].value;
+ sbuf->releasecb = NULL;
+ sbuf->closure = NULL;
+ return MUSTACH_OK;
+ }
+ }
+ GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+ "Template requires value for unexpected name `%s'\n",
+ name);
+ return MUSTACH_ERROR_ITEM_NOT_FOUND;
+}
+
+
+/**
+ * Mustach callback at the end. Cleans up the @a cls.
+ *
+ * @param cls a `struct KVC[]` array
+ * @param status status of mustach (ignored)
+ */
+static void
+m_stop (void *cls,
+ int status)
+{
+ (void) cls;
+ (void) status;
+}
+
+
+/**
+ * Our 'universal' callbacks for mustach.
+ */
+static struct mustach_itf itf = {
+ .enter = &m_enter,
+ .next = &m_next,
+ .leave = &m_leave,
+ .get = &m_get,
+ .stop = &m_stop
+};
+
+
+/**
+ * Load Mustach template into memory. Note that we intentionally cache
+ * failures, that is if we ever failed to load a template, we will never try
+ * again.
+ *
+ * @param connection the connection we act upon
+ * @param name name of the template file to load
+ * (MUST be a 'static' string in memory!)
+ * @return NULL on error, otherwise the template
+ */
+static const char *
+lookup_template (struct MHD_Connection *connection,
+ const char *name)
+{
+ struct TVE *best = NULL;
+ const char *lang;
+
+ lang = MHD_lookup_connection_value (connection,
+ MHD_HEADER_KIND,
+ MHD_HTTP_HEADER_ACCEPT_LANGUAGE);
+ if (NULL == lang)
+ lang = "en";
+ /* find best match by language */
+ for (unsigned int i = 0; i<loaded_length; i++)
+ {
+ if (0 != strcmp (loaded[i].name,
+ name))
+ continue; /* does not match by name */
+ if ( (NULL == best) ||
+ (TALER_MHD_language_matches (lang,
+ loaded[i].lang) >
+ TALER_MHD_language_matches (lang,
+ best->lang) ) )
+ best = &loaded[i];
+ }
+ if (NULL == best)
+ {
+ GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+ "No templates found in `%s'\n",
+ name);
+ return NULL;
+ }
+ return best->value;
+}
+
+
+/**
+ * Load a @a template and substitute using @a kvc, returning
+ * the result to the @a connection with the given
+ * @a http_status code.
+ *
+ * @param connection the connection we act upon
+ * @param http_status desired HTTP status code
+ * @param template basename of the template to load
+ * @param taler_uri value for "Taler:" header to set, or NULL
+ * @param kvc key value pairs to fill in
+ * @return #GNUNET_OK on success (reply queued), #GNUNET_NO if an error was queued,
+ * #GNUNET_SYSERR on failure (to queue an error)
+ */
+enum GNUNET_GenericReturnValue
+TMH_return_from_template (struct MHD_Connection *connection,
+ unsigned int http_status,
+ const char *template,
+ const char *taler_uri,
+ const struct KVC *kvc)
+{
+ struct MHD_Response *reply;
+ char *body;
+ size_t body_size;
+
+ {
+ const char *tmpl;
+ int eno;
+
+ tmpl = lookup_template (connection,
+ template);
+ if (NULL == tmpl)
+ {
+ GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+ "Failed to load template `%s'\n",
+ template);
+ if (MHD_YES !=
+ TALER_MHD_reply_with_error (connection,
+ MHD_HTTP_NOT_ACCEPTABLE,
+ TALER_EC_MERCHANT_FAILED_TO_LOAD_TEMPLATE,
+ template))
+ return GNUNET_SYSERR;
+ return GNUNET_NO;
+ }
+ if (0 !=
+ (eno = mustach (tmpl,
+ &itf,
+ (void *) kvc,
+ &body,
+ &body_size)))
+ {
+ GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+ "mustach failed on template `%s' with error %d\n",
+ template,
+ eno);
+ if (MHD_YES !=
+ TALER_MHD_reply_with_error (connection,
+ MHD_HTTP_INTERNAL_SERVER_ERROR,
+ TALER_EC_MERCHANT_FAILED_TO_EXPAND_TEMPLATE,
+ template))
+ return GNUNET_SYSERR;
+ return GNUNET_NO;
+ }
+ }
+
+ /* try to compress reply if client allows it */
+ {
+ bool compressed = false;
+
+ if (MHD_YES ==
+ TALER_MHD_can_compress (connection))
+ {
+ compressed = TALER_MHD_body_compress ((void **) &body,
+ &body_size);
+ }
+ reply = MHD_create_response_from_buffer (body_size,
+ body,
+ MHD_RESPMEM_MUST_FREE);
+ if (NULL == reply)
+ {
+ GNUNET_break (0);
+ return GNUNET_SYSERR;
+ }
+ if (compressed)
+ {
+ if (MHD_NO ==
+ MHD_add_response_header (reply,
+ MHD_HTTP_HEADER_CONTENT_ENCODING,
+ "deflate"))
+ {
+ GNUNET_break (0);
+ MHD_destroy_response (reply);
+ return GNUNET_SYSERR;
+ }
+ }
+ }
+
+ /* Add standard headers */
+ if (NULL != taler_uri)
+ GNUNET_break (MHD_NO !=
+ MHD_add_response_header (reply,
+ "Taler",
+ taler_uri));
+ GNUNET_break (MHD_NO !=
+ MHD_add_response_header (reply,
+ MHD_HTTP_HEADER_CONTENT_TYPE,
+ "text/html"));
+
+ /* Actually return reply */
+ {
+ MHD_RESULT ret;
+
+ ret = MHD_queue_response (connection,
+ http_status,
+ reply);
+ MHD_destroy_response (reply);
+ if (MHD_NO == ret)
+ return GNUNET_SYSERR;
+ }
+ return GNUNET_OK;
+}
+
+
+/**
+ * Function called with a template's filename.
+ *
+ * @param cls closure
+ * @param filename complete filename (absolute path)
+ * @return #GNUNET_OK to continue to iterate,
+ * #GNUNET_NO to stop iteration with no error,
+ * #GNUNET_SYSERR to abort iteration with error!
+ */
+static int
+load_template (void *cls,
+ const char *filename)
+{
+ char *lang;
+ char *end;
+ int fd;
+ struct stat sb;
+ char *map;
+ const char *name;
+
+ if ('.' == filename[0])
+ return GNUNET_OK;
+
+ name = strrchr (filename,
+ '/');
+ if (NULL == name)
+ name = filename;
+ else
+ name++;
+ lang = strchr (name,
+ '.');
+ if (NULL == lang)
+ return GNUNET_OK; /* name must include .$LANG */
+ lang++;
+ end = strchr (lang,
+ '.');
+ if ( (NULL == end) ||
+ (0 != strcmp (end,
+ ".must")) )
+ return GNUNET_OK; /* name must end with '.must' */
+
+ /* finally open template */
+ fd = open (filename,
+ O_RDONLY);
+ if (-1 == fd)
+ {
+ GNUNET_log_strerror_file (GNUNET_ERROR_TYPE_ERROR,
+ "open",
+ filename);
+
+ return GNUNET_SYSERR;
+ }
+ if (0 !=
+ fstat (fd,
+ &sb))
+ {
+ GNUNET_log_strerror_file (GNUNET_ERROR_TYPE_ERROR,
+ "open",
+ filename);
+ GNUNET_break (0 == close (fd));
+ return GNUNET_OK;
+ }
+ map = GNUNET_malloc_large (sb.st_size + 1);
+ if (NULL == map)
+ {
+ GNUNET_log_strerror (GNUNET_ERROR_TYPE_ERROR,
+ "malloc");
+ GNUNET_break (0 == close (fd));
+ return GNUNET_SYSERR;
+ }
+ if (sb.st_size !=
+ read (fd,
+ map,
+ sb.st_size))
+ {
+ GNUNET_log_strerror_file (GNUNET_ERROR_TYPE_ERROR,
+ "read",
+ filename);
+ GNUNET_break (0 == close (fd));
+ return GNUNET_OK;
+ }
+ GNUNET_break (0 == close (fd));
+ GNUNET_array_grow (loaded,
+ loaded_length,
+ loaded_length + 1);
+ loaded[loaded_length - 1].name = GNUNET_strndup (name,
+ (lang - 1) - name);
+ loaded[loaded_length - 1].lang = GNUNET_strndup (lang,
+ end - lang);
+ loaded[loaded_length - 1].value = map;
+ return GNUNET_OK;
+}
+
+
+/**
+ * Preload templates.
+ */
+int
+TMH_templating_init ()
+{
+ char *dn;
+ int ret;
+
+ {
+ char *path;
+
+ path = GNUNET_OS_installation_get_path (GNUNET_OS_IPK_DATADIR);
+ if (NULL == path)
+ {
+ GNUNET_break (0);
+ return GNUNET_SYSERR;
+ }
+ GNUNET_asprintf (&dn,
+ "%s/merchant/templates/",
+ path);
+ GNUNET_free (path);
+ }
+ ret = GNUNET_DISK_directory_scan (dn,
+ &load_template,
+ NULL);
+ GNUNET_free (dn);
+ if (-1 == ret)
+ {
+ GNUNET_break (0);
+ return GNUNET_SYSERR;
+ }
+ return GNUNET_OK;
+}
+
+
+/**
+ * Nicely shut down.
+ */
+void __attribute__ ((destructor))
+get_orders_fini ()
+{
+ for (unsigned int i = 0; i<loaded_length; i++)
+ {
+ GNUNET_free (loaded[i].name);
+ GNUNET_free (loaded[i].lang);
+ GNUNET_free (loaded[i].value);
+ }
+ GNUNET_array_grow (loaded,
+ loaded_length,
+ 0);
+}