/*
 * Discovery of repositories on disk, so that an administrator can point cgit
 * at a directory instead of naming every repository in cgitrc. The tree below
 * that directory is walked for bare repositories and working trees, or when a
 * project list is configured only the paths it names are visited. Every
 * repository found is registered under its path relative to the root of the
 * scan, with owner, description and section taken from the files git keeps
 * beside it, and a cgitrc in the repository has the last word over all of them.
 */

#include "cgit.h"
#include "config.h"
#include "scan-tree.h"
#include "shared.h"

// Git writes this line into the description file of every repository it
// creates, so a repository still carrying it gets cgit's own default instead.
static const char *default_git_desc =
	"Unnamed repository; edit this file 'description' to name the repository.";

// The config callbacks are handed only a name and a value, so the repository
// being filled in waits here for the length of one add_repo call.
static struct cgit_repo *current_repo;

static int stat_entry(const char *dir, const char *name, struct stat *st)
{
	struct strbuf path = STRBUF_INIT;
	int err;

	strbuf_addf(&path, "%s/%s", dir, name);
	err = stat(path.buf, st);
	// A missing entry is the ordinary answer for a directory that is not a
	// repository, so only some other failure is worth reporting.
	if (err && errno != ENOENT)
		fprintf(stderr, "[cgit] Unable to stat %s: %s (%d)\n", dir, strerror(errno), errno);
	strbuf_release(&path);
	return err;
}

static int is_git_dir(const char *path)
{
	struct stat st;

	if (stat_entry(path, "objects", &st) || !S_ISDIR(st.st_mode))
		return 0;
	if (stat_entry(path, "HEAD", &st) || !S_ISREG(st.st_mode))
		return 0;
	return 1;
}

/*
 * A repository's own files belong to whoever can push to it, so the keys
 * that run a command, put raw markup on the page, hand a file to the browser
 * as markup, read a file off the disk or place a link wait on
 * trust-scan-config. A readme naming a git object, the form with a colon,
 * only reads from the repository and passes.
 */
static int trusted_key(const char *name, const char *value)
{
	int untrusted;

	if (ctx.cfg.trust_scan_config)
		return 1;
	untrusted =
		ends_with(name, "-filter")           ||
		!strcmp(name, "head-content")        ||
		!strcmp(name, "module-link")         ||
		starts_with(name, "module-link.")    ||
		!strcmp(name, "logo")                ||
		!strcmp(name, "logo-link")           ||
		!strcmp(name, "clone-url")           ||
		!strcmp(name, "enable-html-serving") ||
		(!strcmp(name, "readme") && !strchr(value, ':'));
	if (!untrusted)
		return 1;
	fprintf(stderr, "[cgit] Ignoring %s in %s: trust-scan-config is not set\n", name,
		current_repo->path);
	return 0;
}

static int apply_gitconfig(const char *key, const char *value,
		const __attribute__((unused)) struct config_context *cfg_ctx, void *cb)
{
	const char *name;

	// A key with no value is legal git config and nothing here can use it.
	if (!value)
		return 0;
	if (!strcmp(key, "gitweb.owner"))
		cgit_repo_config(current_repo, "owner", value);
	else if (!strcmp(key, "gitweb.description"))
		cgit_repo_config(current_repo, "desc", value);
	else if (!strcmp(key, "gitweb.category"))
		cgit_repo_config(current_repo, "section", value);
	else if (skip_prefix(key, "cgit.", &name) && trusted_key(name, value))
		cgit_repo_config(current_repo, name, value);

	return 0;
}

static void apply_cgitrc(const char *name, const char *value)
{
	if (trusted_key(name, value))
		cgit_repo_config(current_repo, name, value);
}

static char *find_char_back(char *start, char *from, int c)
{
	while (from >= start && *from != c)
		from--;
	return from < start ? NULL : from;
}

/*
 * A positive depth counts separators from the left of the path and a negative
 * one counts back from the right.
 */
static char *section_slash(struct strbuf *relpath, int depth)
{
	char *slash;

	if (depth > 0) {
		slash = relpath->buf - 1;
		while (depth && (slash = strchr(slash + 1, '/')))
			depth--;
	} else {
		slash = relpath->buf + relpath->len;
		while (slash && depth && (slash = find_char_back(relpath->buf, slash - 1, '/')))
			depth++;
	}
	return slash && !depth ? slash : NULL;
}

static void set_section_from_path(struct strbuf *relpath, int depth)
{
	char *slash = section_slash(relpath, depth);

	if (!slash)
		return;
	*slash = '\0';
	current_repo->section = cgit_strdup_first_line(relpath->buf);
	*slash = '/';
	if (starts_with(current_repo->name, current_repo->section)) {
		current_repo->name += strlen(current_repo->section);
		if (*current_repo->name == '/')
			current_repo->name++;
	}
}

static void add_repo(const char *base, struct strbuf *path)
{
	struct stat st;
	struct passwd *pwd;
	size_t pathlen;
	struct strbuf relpath = STRBUF_INIT;
	char *comma;
	size_t desc_size;

	if (stat(path->buf, &st)) {
		fprintf(stderr, "[cgit] Unable to access %s: %s (%d)\n", path->buf, strerror(errno), errno);
		return;
	}

	strbuf_addch(path, '/');
	pathlen = path->len;

	if (ctx.cfg.strict_export) {
		struct stat export_st;

		strbuf_addstr(path, ctx.cfg.strict_export);
		if (stat(path->buf, &export_st))
			return;
		strbuf_setlen(path, pathlen);
	}

	strbuf_addstr(path, "noweb");
	if (!stat(path->buf, &st))
		return;
	strbuf_setlen(path, pathlen);

	if (!starts_with(path->buf, base))
		strbuf_addbuf(&relpath, path);
	else
		strbuf_addstr(&relpath, path->buf + strlen(base) + 1);

	// Drop the trailing slash added above, or the "/.git" suffix test
	// below never matches and a working tree is named "repo/.git".
	if (relpath.len && relpath.buf[relpath.len - 1] == '/')
		strbuf_setlen(&relpath, relpath.len - 1);
	if (relpath.len >= 5 && !strcmp(relpath.buf + relpath.len - 5, "/.git"))
		strbuf_setlen(&relpath, relpath.len - 5);
	else if (!strcmp(relpath.buf, ".git"))
		strbuf_setlen(&relpath, 0);
	// The scan root may itself be the repository, leaving nothing after
	// the base, so that one is named after its directory.
	if (!relpath.len) {
		const char *end = path->buf + pathlen - 1, *start;

		if (end - path->buf >= 5 && !strncmp(end - 5, "/.git", 5))
			end -= 5;
		start = end;
		while (start > path->buf && start[-1] != '/')
			start--;
		strbuf_add(&relpath, start, end - start);
	}

	current_repo = cgit_add_repo(relpath.buf);
	// Set before the config files are read, since a warning about a key
	// found in them names the repository by this path.
	current_repo->path = cgit_strdup_first_line(path->buf);
	if (ctx.cfg.enable_git_config) {
		// A pusher wrote this file, so a broken one is skipped with a
		// warning rather than allowed to end the request.
		struct config_options opts = { .error_action = CONFIG_ERROR_SILENT };

		strbuf_addstr(path, "config");
		if (git_config_from_file_with_options(apply_gitconfig, path->buf, NULL,
				CONFIG_SCOPE_UNKNOWN, &opts))
			fprintf(stderr, "[cgit] Ignoring unreadable config in %s\n", path->buf);
		strbuf_setlen(path, pathlen);
	}

	if (ctx.cfg.remove_suffix) {
		size_t urllen;
		strip_suffix(current_repo->url, ".git", &urllen);
		strip_suffix_mem(current_repo->url, &urllen, "/");
		current_repo->url[urllen] = '\0';
	}
	while (!current_repo->owner) {
		if (!(pwd = getpwuid(st.st_uid))) {
			fprintf(stderr, "[cgit] Unable to read the owner of %s: %s (%d)\n",
				path->buf, strerror(errno), errno);
			break;
		}
		// A gecos field puts the owner's name in front of a comma
		// separated list of office and phone details.
		if (pwd->pw_gecos && (comma = strchr(pwd->pw_gecos, ',')))
			*comma = '\0';
		current_repo->owner = cgit_strdup_first_line(pwd->pw_gecos ? pwd->pw_gecos : pwd->pw_name);
	}

	if (current_repo->desc == cgit_default_repo_desc || !current_repo->desc) {
		strbuf_addstr(path, "description");
		if (!stat(path->buf, &st))
			cgit_read_first_line(path->buf, &current_repo->desc, &desc_size);
		strbuf_setlen(path, pathlen);
		if (current_repo->desc && !strcmp(current_repo->desc, default_git_desc)) {
			free(current_repo->desc);
			current_repo->desc = cgit_default_repo_desc;
		}
	}

	if (ctx.cfg.section_from_path)
		set_section_from_path(&relpath, ctx.cfg.section_from_path);

	strbuf_addstr(path, "cgitrc");
	if (!stat(path->buf, &st))
		config_file_parse(path->buf, apply_cgitrc);

	strbuf_release(&relpath);
}

static int should_scan(const struct dirent *ent)
{
	if (ent->d_name[0] != '.')
		return 1;
	if (ent->d_name[1] == '\0')
		return 0;
	if (ent->d_name[1] == '.' && ent->d_name[2] == '\0')
		return 0;
	return ctx.cfg.scan_hidden_path;
}

// Symlinks are followed so that a link into the scan path counts, which means
// a link back at an ancestor would recurse until the path ran out of room.
// Each directory is entered once.
static struct {
	dev_t dev;
	ino_t ino;
} *visited;
static size_t visited_nr, visited_alloc;

static int already_visited(const char *path)
{
	struct stat st;
	size_t i;

	if (stat(path, &st))
		return 0;
	for (i = 0; i < visited_nr; i++)
		if (visited[i].dev == st.st_dev && visited[i].ino == st.st_ino)
			return 1;
	ALLOC_GROW(visited, visited_nr + 1, visited_alloc);
	visited[visited_nr].dev = st.st_dev;
	visited[visited_nr].ino = st.st_ino;
	visited_nr++;
	return 0;
}

static void scan_path(const char *base, const char *path)
{
	DIR *dir;
	struct dirent *ent;
	struct strbuf pathbuf = STRBUF_INIT;
	size_t pathlen = strlen(path);
	struct stat st;

	if (already_visited(path))
		return;
	dir = opendir(path);
	if (!dir) {
		fprintf(stderr, "[cgit] Unable to open %s: %s (%d)\n", path, strerror(errno), errno);
		return;
	}

	strbuf_add(&pathbuf, path, pathlen);
	if (is_git_dir(pathbuf.buf)) {
		add_repo(base, &pathbuf);
		goto end;
	}
	strbuf_addstr(&pathbuf, "/.git");
	if (is_git_dir(pathbuf.buf)) {
		add_repo(base, &pathbuf);
		goto end;
	}
	// Take in the '/' that "/.git" left in the buffer, since the loop below
	// truncates to this length and then appends an entry name straight on.
	pathlen++;
	while ((ent = readdir(dir))) {
		if (!should_scan(ent))
			continue;
		strbuf_setlen(&pathbuf, pathlen);
		strbuf_addstr(&pathbuf, ent->d_name);
		if (stat(pathbuf.buf, &st)) {
			fprintf(stderr, "[cgit] Unable to stat %s: %s (%d)\n", pathbuf.buf, strerror(errno),
				errno);
			continue;
		}
		if (S_ISDIR(st.st_mode))
			scan_path(base, pathbuf.buf);
	}
end:
	strbuf_release(&pathbuf);
	closedir(dir);
}

void scan_projects(const char *path, const char *projectsfile)
{
	struct strbuf line = STRBUF_INIT;
	FILE *projects;
	int err;

	projects = fopen(projectsfile, "r");
	if (!projects) {
		fprintf(stderr, "[cgit] Unable to open project list %s: %s (%d)\n",
			projectsfile, strerror(errno), errno);
		return;
	}
	while (strbuf_getline(&line, projects) != EOF) {
		if (!line.len)
			continue;
		strbuf_insert(&line, 0, "/", 1);
		strbuf_insert(&line, 0, path, strlen(path));
		scan_path(path, line.buf);
	}
	if ((err = ferror(projects))) {
		fprintf(stderr, "[cgit] Unable to read project list %s: %s (%d)\n",
			projectsfile, strerror(err), err);
	}
	fclose(projects);
	strbuf_release(&line);
}

void scan_tree(const char *path)
{
	scan_path(path, path);
}