/* ui-ci.c: redirect to an external CI system
 *
 * Copyright (C) 2026 Saya Andy <saya.andy@posteo.com>
 *
 * Licensed under GNU General Public License v2
 *   (see COPYING for full license text)
 */

#define USE_THE_REPOSITORY_VARIABLE

#include "cgit.h"
#include "ui-ci.h"
#include "html.h"
#include "ui-shared.h"

/* Memoized outcome of resolving the ci url for this request: -1 while
 * unresolved, 0 when there is no ci url for the current ref, and 1 when
 * ci_url holds the url to redirect to.
 */
static int ci_resolved = -1;
static char *ci_url;

static int ref_is_tag(const char *ref)
{
	struct strbuf fullref = STRBUF_INIT;
	struct object_id oid;
	int is_tag;

	strbuf_addf(&fullref, "refs/tags/%s", ref);
	is_tag = !repo_get_oid(the_repository, fullref.buf, &oid);
	strbuf_release(&fullref);
	return is_tag;
}

/* Append the repository url with any ".git" suffix removed and all
 * slashes replaced by dashes, e.g. "sayauz/web.git" becomes
 * "sayauz-web".
 */
static void add_repo_slug(struct strbuf *buf, const char *url)
{
	size_t len, i;

	if (!strip_suffix(url, ".git", &len))
		len = strlen(url);
	for (i = 0; i < len; i++)
		strbuf_addch(buf, url[i] == '/' ? '-' : url[i]);
}

static char *expand_ci_url(const char *template)
{
	const char *p, *rest;
	struct strbuf buf = STRBUF_INIT;

	for (p = template; *p; p++) {
		if (*p != '$') {
			strbuf_addch(&buf, *p);
			continue;
		}
		if (skip_prefix(p, "$ref", &rest))
			strbuf_addstr(&buf, ctx.qry.head);
		else if (skip_prefix(p, "$repo", &rest))
			strbuf_addstr(&buf, ctx.repo->url);
		else if (skip_prefix(p, "$slug", &rest))
			add_repo_slug(&buf, ctx.repo->url);
		else if (skip_prefix(p, "$$", &rest))
			strbuf_addch(&buf, '$');
		else {
			strbuf_addch(&buf, '$');
			continue;
		}
		p = rest - 1;
	}
	return strbuf_detach(&buf, NULL);
}

/* Ask the ci filter whether the pipeline denoted by url actually exists.
 * The filter must not write to stdout, and signals "yes" by exiting with
 * a zero status.
 */
static int ci_filter_accepts(const char *refkind, const char *url)
{
	struct cgit_filter *filter = ctx.repo->ci_filter;

	if (!filter)
		return 1;
	if (cgit_open_filter(filter, ctx.qry.head, refkind, url))
		return 0;
	return !cgit_close_filter(filter);
}

static void resolve_ci_url(void)
{
	const char *template, *refkind;

	if (ci_resolved != -1)
		return;
	ci_resolved = 0;

	if (!ctx.repo || !ctx.qry.head || !cgit_have_repository())
		return;

	if (ref_is_tag(ctx.qry.head)) {
		refkind = "tag";
		template = ctx.repo->ci_tag_url;
	} else {
		refkind = "branch";
		template = ctx.repo->ci_branch_url;
	}
	if (!template)
		template = ctx.repo->ci_url;
	if (!template)
		return;

	ci_url = expand_ci_url(template);
	if (!ci_filter_accepts(refkind, ci_url)) {
		free(ci_url);
		ci_url = NULL;
		return;
	}
	ci_resolved = 1;
}

int cgit_ci_available(void)
{
	resolve_ci_url();
	return ci_resolved == 1;
}

void cgit_print_ci(void)
{
	resolve_ci_url();

	if (ci_resolved != 1) {
		cgit_print_error_page(404, "Not found",
				      "No ci url available for %s",
				      ctx.qry.head);
		return;
	}

	/* The expanded template is emitted verbatim rather than through
	 * cgit_redirect(), which percent-encodes characters such as '?',
	 * '=' and '%' that are meaningful in a ci url.  Refuse anything
	 * which could be used to smuggle in extra response headers.
	 */
	if (strpbrk(ci_url, "\r\n")) {
		cgit_print_error_page(500, "Internal server error",
				      "Malformed ci url");
		return;
	}

	htmlf("Status: 302 Found\nLocation: %s\n\n", ci_url);
}