/* 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"

static int escapeNull(FILE *file, const char *str) {
	size_t n = fwrite(str, strlen(str), 1, file);
	return (n ? 0 : -1);
}

int escapeURL(FILE *file, const char *str) {
	static const char *Safe = {
		"$-_.+!*'(),"
		"0123456789"
		"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
		"abcdefghijklmnopqrstuvwxyz"
	};
	while (*str) {
		size_t len = strspn(str, Safe);
		if (len) {
			size_t n = fwrite(str, len, 1, file);
			if (!n) return -1;
		}
		str += len;
		if (*str) {
			int n = fprintf(file, "%%%02X", *str++);
			if (n < 0) return n;
		}
	}
	return 0;
}

int escapeXML(FILE *file, const char *str) {
	while (*str) {
		size_t len = strcspn(str, "\"&<");
		if (len) {
			size_t n = fwrite(str, len, 1, file);
			if (!n) return -1;
		}
		str += len;
		int n = 0;
		switch (*str) {
			break; case '"': str++; n = fprintf(file, "&quot;");
			break; case '&': str++; n = fprintf(file, "&amp;");
			break; case '<': str++; n = fprintf(file, "&lt;");
		}
		if (n < 0) return n;
	}
	return 0;
}

int templateRender(
	FILE *file, const char *template,
	const struct Variable vars[], EscapeFn *escape
) {
	if (!escape) escape = escapeNull;
	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 && 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 if (len) {
			size_t n = fwrite(template, len, 1, file);
			if (!n) return -1;
		}
		template += len;
		if (*template) template++;
	}
	return 0;
}

char *templateURL(const char *template, const struct Variable vars[]) {
	size_t cap = strlen(template) + 1;
	for (const struct Variable *var = vars; var->name; ++var) {
		cap += 3 * strlen(var->value);
	}
	char *buf = malloc(cap);
	if (!buf) err(EX_OSERR, "malloc");

	FILE *file = fmemopen(buf, cap, "w");
	if (!file) err(EX_OSERR, "fmemopen");

	int error = templateRender(file, template, vars, escapeURL)
		|| fclose(file);
	assert(!error);
	return buf;
}