Render basic HTML envelopes with templating

1 files changed, 57 insertions, 0 deletions

diff --git a/template.c b/template.c
new file mode 100644
index 0000000..3caa8b2
--- /dev/null
+++ b/template.c
@@ -0,0 +1,57 @@
+/* Copyright (C) 2020  C. McEnroe <june@causal.agency>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <assert.h>
+#include <err.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sysexits.h>
+
+#include "archive.h"
+
+int templateRender(
+	FILE *file, const char *template,
+	const struct Variable *vars, EscapeFn *escape
+) {
+	for (bool subst = false; *template; subst ^= true) {
+		size_t len = strcspn(template, "[]");
+		if (subst) {
+			const char *value = NULL;
+			for (const struct Variable *var = vars; var->name; ++var) {
+				if (strlen(var->name) != len) continue;
+				if (strncmp(var->name, template, len)) continue;
+				value = var->value;
+				break;
+			}
+			if (!value) {
+				errx(
+					EX_SOFTWARE, "no value for template variable %.*s",
+					(int)len, template
+				);
+			}
+			int error = escape(file, value);
+			if (error) return error;
+		} else {
+			size_t n = fwrite(template, len, 1, file);
+			if (!n) return -1;
+		}
+		template += len;
+		if (*template) template++;
+	}
+	return 0;
+}