initial

1 files changed, 244 insertions, 0 deletions

diff --git a/src/currency.c b/src/currency.c
new file mode 100644
index 0000000..1900a58
--- /dev/null
+++ b/src/currency.c
@@ -0,0 +1,244 @@
+#include <time.h>
+
+#include <glib.h>
+#include <glib/gstdio.h>
+#include <gio/gio.h>
+#include <libxml/tree.h>
+#include <libxml/xpath.h>
+#include <libxml/xpathInternals.h>
+
+#include "currency.h"
+#include "mp.h"
+
+typedef struct {
+    char *short_name;
+    MPNumber value;
+} currency;
+
+static currency *currencies = NULL;
+static int currency_count = 0;
+
+static gboolean downloading_rates = FALSE;
+static gboolean loaded_rates = FALSE;
+
+static char*
+get_rate_filepath()
+{
+    return g_build_filename(g_get_user_cache_dir (),
+                            "gcalctool",
+                            "eurofxref-daily.xml",
+                            NULL);
+}
+
+static int
+currency_get_index(const char *short_name)
+{
+    int i;
+    for (i = 0; i < currency_count; i++) {
+        if (!strcmp(short_name, currencies[i].short_name)) {
+            if (mp_is_negative(&currencies[i].value) ||
+                mp_is_zero(&currencies[i].value)) {
+                return -1;
+            } else {
+                return i;
+            }
+        }
+    }
+    return -1;
+}
+
+/* A file needs to be redownloaded if it doesn't exist, or every 7 days.
+ * When an error occur, it probably won't hurt to try to download again.
+ */
+static int
+currency_rates_needs_update()
+{
+    gchar *filename = get_rate_filepath ();
+    struct stat buf;
+    if (!g_file_test(filename, G_FILE_TEST_IS_REGULAR)) {
+        g_free(filename);
+        return 1;
+    }
+
+    if (g_stat(filename, &buf) == -1) {
+        g_free(filename);
+        return 1;
+    }
+    g_free(filename);
+
+    if (difftime(time(NULL), buf.st_mtime) > (60 * 60 * 24 * 7)) {
+        return 1;
+    }
+
+    return 0;
+}
+
+
+static void
+download_cb(GObject *object, GAsyncResult *result, gpointer user_data)
+{
+    GError *error = NULL;
+
+    if (g_file_copy_finish(G_FILE(object), result, &error))
+        g_debug("Rates updated");
+    else
+        g_warning("Couldn't download currency file: %s", error->message);
+    g_clear_error(&error);
+    downloading_rates = FALSE;
+}
+
+
+static void
+currency_download_rates()
+{
+    gchar *filename, *directory;
+    GFile *source, *dest;
+
+    downloading_rates = TRUE;
+    g_debug("Downloading rates...");
+
+    filename = get_rate_filepath();
+    directory = g_path_get_dirname(filename);
+    g_mkdir_with_parents(directory, 0755);
+    g_free(directory);
+
+    source = g_file_new_for_uri ("http://www.ecb.europa.eu/stats/eurofxref/eurofxref-daily.xml");
+    dest = g_file_new_for_path (filename);
+    g_free(filename);
+
+    g_file_copy_async (source, dest, G_FILE_COPY_OVERWRITE, G_PRIORITY_DEFAULT, NULL, NULL, NULL, download_cb, NULL);
+    g_object_unref(source);
+    g_object_unref(dest);
+}
+
+
+static void
+set_rate (xmlNodePtr node, currency *cur)
+{
+    xmlAttrPtr attribute;
+    for (attribute = node->properties; attribute; attribute = attribute->next) {
+        if (strcmp((char *)attribute->name, "currency") == 0) {
+            cur->short_name = (char *)xmlNodeGetContent((xmlNodePtr) attribute);
+        } else if (strcmp ((char *)attribute->name, "rate") == 0) {
+            char *val = (char *)xmlNodeGetContent ((xmlNodePtr) attribute);
+            mp_set_from_string(val, 10, &(cur->value));
+            xmlFree (val);
+        }
+    }
+}
+
+static void
+currency_load_rates()
+{
+    char *filename = get_rate_filepath();
+    xmlDocPtr document;
+    xmlXPathContextPtr xpath_ctx;
+    xmlXPathObjectPtr xpath_obj;
+    int i, len;
+
+    g_return_if_fail(g_file_test(filename, G_FILE_TEST_IS_REGULAR));
+
+    xmlInitParser();
+    document = xmlReadFile(filename, NULL, 0);
+    g_free (filename);
+    if (document == NULL) {
+        fprintf(stderr, "Couldn't parse data file\n");
+        return;
+    }
+
+    xpath_ctx = xmlXPathNewContext(document);
+    if (xpath_ctx == NULL) {
+        xmlFreeDoc(document);
+        fprintf(stderr, "Couldn't create XPath context\n");
+        return;
+    }
+
+    xmlXPathRegisterNs(xpath_ctx,
+                       BAD_CAST("xref"),
+                       BAD_CAST("http://www.ecb.int/vocabulary/2002-08-01/eurofxref"));
+    xpath_obj = xmlXPathEvalExpression(BAD_CAST("//xref:Cube[@currency][@rate]"),
+                                       xpath_ctx);
+
+    if (xpath_obj == NULL) {
+        xmlXPathFreeContext(xpath_ctx);
+        xmlFreeDoc(document);
+        fprintf(stderr, "Couldn't create XPath object\n");
+        return;
+    }
+
+    len = (xpath_obj->nodesetval) ? xpath_obj->nodesetval->nodeNr : 0;
+    currency_count = len + 1;
+    currencies = g_slice_alloc0(sizeof(currency) * currency_count);
+    for (i = 0; i < len; i++) {
+        if (xpath_obj->nodesetval->nodeTab[i]->type == XML_ELEMENT_NODE) {
+            set_rate(xpath_obj->nodesetval->nodeTab[i], &currencies[i]);
+        }
+
+        // Avoid accessing removed elements
+        if (xpath_obj->nodesetval->nodeTab[i]->type != XML_NAMESPACE_DECL)
+            xpath_obj->nodesetval->nodeTab[i] = NULL;
+    }
+
+    currencies[len].short_name = g_strdup("EUR");
+    MPNumber foo;
+    mp_set_from_integer(1, &foo);
+    currencies[len].value = foo;
+
+    xmlXPathFreeObject(xpath_obj);
+    xmlXPathFreeContext(xpath_ctx);
+    xmlFreeDoc(document);
+    xmlCleanupParser();
+
+    g_debug("Rates loaded");
+    loaded_rates = TRUE;
+}
+
+
+gboolean
+currency_convert(const MPNumber *from_amount,
+                 const char *source_currency, const char *target_currency,
+                 MPNumber *to_amount)
+{
+    int from_index, to_index;
+
+    if (downloading_rates)
+        return FALSE;
+
+    /* Update currency if necessary */
+    if (currency_rates_needs_update()) {
+        currency_download_rates();
+        return FALSE;
+    }
+    if (!loaded_rates)
+        currency_load_rates();
+  
+    from_index = currency_get_index(source_currency);
+    to_index = currency_get_index(target_currency);
+    if (from_index < 0 || to_index < 0)
+        return FALSE;
+
+    if (mp_is_zero(&currencies[from_index].value) ||
+        mp_is_zero(&currencies[to_index].value)) {
+        mp_set_from_integer(0, to_amount);
+        return FALSE;
+    }
+
+    mp_divide(from_amount, &currencies[from_index].value, to_amount);
+    mp_multiply(to_amount, &currencies[to_index].value, to_amount);
+
+    return TRUE;
+}
+
+void
+currency_free_resources()
+{
+    int i;
+
+    for (i = 0; i < currency_count; i++) {
+        if (currencies[i].short_name != NULL)
+            xmlFree(currencies[i].short_name);
+    }
+    g_slice_free1(currency_count * sizeof(currency), currencies);
+    currencies = NULL;
+    currency_count = 0;
+}