summaryrefslogtreecommitdiff
path: root/src/currency.c
blob: 1900a585e6181e083ac4d3a0f22653af1816da0e (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
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;
}