From c6562fa39bc3b609429fea9064a94cf080922da5 Mon Sep 17 00:00:00 2001
From: default <nobody@localhost>
Date: Sun, 15 Dec 2024 22:52:41 +0100
Subject: [PATCH] New function timeline_link_header().

---
 httpd.c    |  5 ++++-
 mastoapi.c | 31 ++++++++++++++++++++++++++++++-
 snac.h     |  2 +-
 3 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/httpd.c b/httpd.c
index 81d2f9e..0eff657 100644
--- a/httpd.c
+++ b/httpd.c
@@ -279,6 +279,7 @@ void httpd_connection(FILE *f)
     xs *payload  = NULL;
     xs *etag     = NULL;
     xs *last_modified = NULL;
+    xs *link     = NULL;
     int p_size   = 0;
     const char *p;
     int fcgi_id;
@@ -326,7 +327,7 @@ void httpd_connection(FILE *f)
             status = oauth_get_handler(req, q_path, &body, &b_size, &ctype);
 
         if (status == 0)
-            status = mastoapi_get_handler(req, q_path, &body, &b_size, &ctype);
+            status = mastoapi_get_handler(req, q_path, &body, &b_size, &ctype, &link);
 #endif /* NO_MASTODON_API */
 
         if (status == 0)
@@ -426,6 +427,8 @@ void httpd_connection(FILE *f)
         headers = xs_dict_append(headers, "etag", etag);
     if (!xs_is_null(last_modified))
         headers = xs_dict_append(headers, "last-modified", last_modified);
+    if (!xs_is_null(link))
+        headers = xs_dict_append(headers, "Link", link);
 
     /* if there are any additional headers, add them */
     const xs_dict *more_headers = xs_dict_get(srv_config, "http_headers");
diff --git a/mastoapi.c b/mastoapi.c
index be8be80..6b816f4 100644
--- a/mastoapi.c
+++ b/mastoapi.c
@@ -1434,8 +1434,35 @@ xs_list *mastoapi_timeline(snac *user, const xs_dict *args, const char *index_fn
 }
 
 
+xs_str *timeline_link_header(const char *endpoint, xs_list *timeline)
+/* returns a Link header with paging information */
+{
+    xs_str *s = NULL;
+
+    if (xs_list_len(timeline) == 0)
+        return NULL;
+
+    const xs_dict *first_st = xs_list_get(timeline, 0);
+    const xs_dict *last_st  = xs_list_get(timeline, -1);
+    const char *first_id    = xs_dict_get(first_st, "id");
+    const char *last_id     = xs_dict_get(last_st, "id");
+    const char *host        = xs_dict_get(srv_config, "host");
+    const char *protocol    = xs_dict_get_def(srv_config, "protocol", "https");
+
+    s = xs_fmt(
+        "<%s:/" "/%s%s?max_id=%s>; rel=\"next\", "
+        "<%s:/" "/%s%s?since_id=%s>; rel=\"prev\"",
+        protocol, host, endpoint, last_id,
+        protocol, host, endpoint, first_id);
+
+    srv_debug(1, xs_fmt("timeline_link_header %s", s));
+
+    return s;
+}
+
+
 int mastoapi_get_handler(const xs_dict *req, const char *q_path,
-                         char **body, int *b_size, char **ctype)
+                         char **body, int *b_size, char **ctype, xs_str **link)
 {
     (void)b_size;
 
@@ -1695,6 +1722,8 @@ int mastoapi_get_handler(const xs_dict *req, const char *q_path,
             xs *ifn = user_index_fn(&snac1, "private");
             xs *out = mastoapi_timeline(&snac1, args, ifn);
 
+            *link = timeline_link_header(cmd, out);
+
             *body  = xs_json_dumps(out, 4);
             *ctype = "application/json";
             status = HTTP_STATUS_OK;
diff --git a/snac.h b/snac.h
index acc175f..5b8b2f8 100644
--- a/snac.h
+++ b/snac.h
@@ -384,7 +384,7 @@ int oauth_post_handler(const xs_dict *req, const char *q_path,
                        const char *payload, int p_size,
                        char **body, int *b_size, char **ctype);
 int mastoapi_get_handler(const xs_dict *req, const char *q_path,
-                         char **body, int *b_size, char **ctype);
+                         char **body, int *b_size, char **ctype, xs_str **link);
 int mastoapi_post_handler(const xs_dict *req, const char *q_path,
                           const char *payload, int p_size,
                           char **body, int *b_size, char **ctype);