From 4e0c7c752728943223671677e2667cdbad0adbde Mon Sep 17 00:00:00 2001
From: Carlos Garnacho <carlosg@gnome.org>
Date: Mon, 20 Mar 2023 11:19:54 +0100
Subject: core: Add helper SQLite function to tokenize FTS search terms

This function splits the search terms, and surrounds each of them with
double quotes so they are taken as individual literal strings to be
matched, quotes explicitly present in the search string are observed
and handled as a single search term, and implicitly closed in unfinished.
---
 .../core/tracker-db-interface-sqlite.c             | 62 ++++++++++++++++++++++
 1 file changed, 62 insertions(+)

(limited to 'src/libtracker-sparql')

diff --git a/src/libtracker-sparql/core/tracker-db-interface-sqlite.c b/src/libtracker-sparql/core/tracker-db-interface-sqlite.c
index 24c863616..2aa493ca9 100644
--- a/src/libtracker-sparql/core/tracker-db-interface-sqlite.c
+++ b/src/libtracker-sparql/core/tracker-db-interface-sqlite.c
@@ -1681,6 +1681,66 @@ function_sparql_print_value (sqlite3_context *context,
 	}
 }
 
+static void
+function_sparql_fts_tokenize (sqlite3_context *context,
+                              int              argc,
+                              sqlite3_value   *argv[])
+{
+	const gchar *fn = "SparqlFtsTokenizer helper";
+	gchar *text;
+	const gchar *p;
+	gboolean in_quote = FALSE;
+	gboolean in_space = FALSE;
+	gboolean started = FALSE;
+	int n_output_quotes = 0;
+	gunichar ch;
+	GString *str;
+	int len;
+	gchar *result;
+
+	if (argc > 1) {
+		result_context_function_error (context, fn, "Invalid argument count");
+		return;
+	}
+
+	text = g_strstrip (g_strdup (sqlite3_value_text (argv[0])));
+	str = g_string_new (NULL);
+	p = text;
+
+	while ((ch = g_utf8_get_char (p)) != 0) {
+		if (ch == '\"') {
+			n_output_quotes++;
+			in_quote = !in_quote;
+		} else if ((ch == ' ') != !!in_space) {
+			/* Ensure terms get independently quoted, unless
+			 * they are within a explicitly quoted part of the text.
+			 */
+			if (!in_quote && started) {
+				g_string_append_c (str, '"');
+				n_output_quotes++;
+			}
+
+			in_space = ch == ' ';
+		} else if (!started) {
+			/* Not a quote, nor a space at the first char. Add the starting quote */
+			g_string_append_c (str, '"');
+			n_output_quotes++;
+		}
+
+		g_string_append_unichar (str, ch);
+		started = TRUE;
+		p = g_utf8_next_char (p);
+	}
+
+	if (n_output_quotes % 2 != 0)
+		g_string_append_c (str, '"');
+
+	len = str->len;
+	result = g_string_free (str, FALSE);
+	sqlite3_result_text (context, result, len, g_free);
+	g_free (text);
+}
+
 static int
 check_interrupt (void *user_data)
 {
@@ -1757,6 +1817,8 @@ initialize_functions (TrackerDBInterface *db_interface)
 		  function_sparql_strlang },
 		{ "SparqlPrintValue", 2, SQLITE_ANY | SQLITE_DETERMINISTIC,
 		  function_sparql_print_value },
+		{ "SparqlFtsTokenize", 1, SQLITE_ANY | SQLITE_DETERMINISTIC,
+		  function_sparql_fts_tokenize },
 		/* Numbers */
 		{ "SparqlCeil", 1, SQLITE_ANY | SQLITE_DETERMINISTIC,
 		  function_sparql_ceil },
-- 
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