From b2d31bc42a7694c671186081ee0cac077a188b99 Mon Sep 17 00:00:00 2001
From: Sebastian Harl <sh@tokkee.org>
Date: Sat, 10 Sep 2016 19:15:35 -0400
Subject: [PATCH] plugin: Add a helper function to query timeseries
 information.

This is a wrapper around the registered timeseries fetcher plugin.
---
 src/core/plugin.c         | 25 +++++++++++++++++++++++++
 src/include/core/plugin.h | 14 ++++++++++++++
 2 files changed, 39 insertions(+)

diff --git a/src/core/plugin.c b/src/core/plugin.c
index 3fb0a77..ca04ae2 100644
--- a/src/core/plugin.c
+++ b/src/core/plugin.c
@@ -1555,6 +1555,31 @@ sdb_plugin_fetch_timeseries(const char *type, const char *id,
 	return ts;
 } /* sdb_plugin_fetch_timeseries */
 
+sdb_timeseries_info_t *
+sdb_plugin_describe_timeseries(const char *type, const char *id)
+{
+	ts_fetcher_t *fetcher;
+	sdb_timeseries_info_t *ts_info;
+
+	ctx_t *old_ctx;
+
+	if ((! type) || (! id))
+		return NULL;
+
+	fetcher = TS_FETCHER(sdb_llist_search_by_name(timeseries_fetcher_list, type));
+	if (! fetcher) {
+		sdb_log(SDB_LOG_ERR, "core: Cannot describe time-series of type %s: "
+				"no such plugin loaded", type);
+		errno = ENOENT;
+		return NULL;
+	}
+
+	old_ctx = ctx_set(fetcher->ts_ctx);
+	ts_info = fetcher->impl.describe(id, fetcher->ts_user_data);
+	ctx_set(old_ctx);
+	return ts_info;
+} /* sdb_plugin_describe_timeseries */
+
 int
 sdb_plugin_query(sdb_ast_node_t *ast,
 		sdb_store_writer_t *w, sdb_object_t *wd, sdb_strbuf_t *errbuf)
diff --git a/src/include/core/plugin.h b/src/include/core/plugin.h
index b12af78..6574330 100644
--- a/src/include/core/plugin.h
+++ b/src/include/core/plugin.h
@@ -434,6 +434,20 @@ sdb_timeseries_t *
 sdb_plugin_fetch_timeseries(const char *type, const char *id,
 		sdb_timeseries_opts_t *opts);
 
+/*
+ * sdb_plugin_describe_timeseries:
+ * Fetch information about the time-series identified by 'id' from a backend
+ * data-store of the specified 'type'. The type has to match an existing
+ * time-series fetcher callback's name. The identifier is passed through to
+ * the callback which then needs to make sense of it.
+ *
+ * Returns:
+ *  - a time-series information object on success
+ *  - NULL else
+ */
+sdb_timeseries_info_t *
+sdb_plugin_describe_timeseries(const char *type, const char *id);
+
 /*
  * sdb_plugin_query:
  * Query the store using the query specified by 'ast'. The result will be
-- 
2.30.2