#include "cache.h"
#include "refs.h"
#include "strbuf.h"
#include "worktree.h"

void free_worktrees(struct worktree **worktrees)
{
        int i = 0;

        for (i = 0; worktrees[i]; i++) {
                free(worktrees[i]->path);
                free(worktrees[i]);
        }
        free (worktrees);
}

/*
 * read 'path_to_ref' into 'ref'.  Also if is_detached is not NULL,
 * set is_detached to 1 (0) if the ref is detatched (is not detached).
 *
 * $GIT_COMMON_DIR/$symref (e.g. HEAD) is practically outside $GIT_DIR so
 * for linked worktrees, `resolve_ref_unsafe()` won't work (it uses
 * git_path). Parse the ref ourselves.
 *
 * return -1 if the ref is not a proper ref, 0 otherwise (success)
 */
static int parse_ref(char *path_to_ref, struct strbuf *ref, int *is_detached)
{
        if (is_detached)
                *is_detached = 0;
        if (!strbuf_readlink(ref, path_to_ref, 0)) {
                /* HEAD is symbolic link */
                if (!starts_with(ref->buf, "refs/") ||
                                check_refname_format(ref->buf, 0))
                        return -1;
        } else if (strbuf_read_file(ref, path_to_ref, 0) >= 0) {
                /* textual symref or detached */
                if (!starts_with(ref->buf, "ref:")) {
                        if (is_detached)
                                *is_detached = 1;
                } else {
                        strbuf_remove(ref, 0, strlen("ref:"));
                        strbuf_trim(ref);
                        if (check_refname_format(ref->buf, 0))
                                return -1;
                }
        } else
                return -1;
        return 0;
}

/**
 * get the main worktree
 */
static struct worktree *get_main_worktree(void)
{
        struct worktree *worktree = NULL;
        struct strbuf path = STRBUF_INIT;
        struct strbuf worktree_path = STRBUF_INIT;
        struct strbuf gitdir = STRBUF_INIT;
        struct strbuf head_ref = STRBUF_INIT;

        strbuf_addf(&gitdir, "%s", absolute_path(get_git_common_dir()));
        strbuf_addbuf(&worktree_path, &gitdir);
        if (!strbuf_strip_suffix(&worktree_path, "/.git"))
                strbuf_strip_suffix(&worktree_path, "/.");

        strbuf_addf(&path, "%s/HEAD", get_git_common_dir());

        if (parse_ref(path.buf, &head_ref, NULL) >= 0) {
                worktree = xmalloc(sizeof(struct worktree));
                worktree->path = strbuf_detach(&worktree_path, NULL);
                worktree->git_dir = strbuf_detach(&gitdir, NULL);
        }
        strbuf_release(&path);
        strbuf_release(&gitdir);
        strbuf_release(&worktree_path);
        strbuf_release(&head_ref);
        return worktree;
}

static struct worktree *get_linked_worktree(const char *id)
{
        struct worktree *worktree = NULL;
        struct strbuf path = STRBUF_INIT;
        struct strbuf worktree_path = STRBUF_INIT;
        struct strbuf gitdir = STRBUF_INIT;
        struct strbuf head_ref = STRBUF_INIT;

        if (!id)
                die("Missing linked worktree name");

        strbuf_addf(&gitdir, "%s/worktrees/%s",
                        absolute_path(get_git_common_dir()), id);
        strbuf_addf(&path, "%s/gitdir", gitdir.buf);
        if (strbuf_read_file(&worktree_path, path.buf, 0) <= 0)
                /* invalid gitdir file */
                goto done;

        strbuf_rtrim(&worktree_path);
        if (!strbuf_strip_suffix(&worktree_path, "/.git")) {
                strbuf_reset(&worktree_path);
                strbuf_addstr(&worktree_path, absolute_path("."));
                strbuf_strip_suffix(&worktree_path, "/.");
        }

        strbuf_reset(&path);
        strbuf_addf(&path, "%s/worktrees/%s/HEAD", get_git_common_dir(), id);

        if (parse_ref(path.buf, &head_ref, NULL) >= 0) {
                worktree = xmalloc(sizeof(struct worktree));
                worktree->path = strbuf_detach(&worktree_path, NULL);
                worktree->git_dir = strbuf_detach(&gitdir, NULL);
        }

done:
        strbuf_release(&path);
        strbuf_release(&gitdir);
        strbuf_release(&worktree_path);
        strbuf_release(&head_ref);
        return worktree;
}

struct worktree **get_worktrees(void)
{
        struct worktree **list = NULL;
        struct strbuf path = STRBUF_INIT;
        DIR *dir;
        struct dirent *d;
        int counter = 0, alloc = 2;

        list = xmalloc(alloc * sizeof(struct worktree *));

        if ((list[counter] = get_main_worktree()))
                counter++;

        strbuf_addf(&path, "%s/worktrees", get_git_common_dir());
        dir = opendir(path.buf);
        strbuf_release(&path);
        if (dir) {
                while ((d = readdir(dir)) != NULL) {
                        struct worktree *linked = NULL;
                        if (!strcmp(d->d_name, ".") || !strcmp(d->d_name, ".."))
                                continue;

                                if ((linked = get_linked_worktree(d->d_name))) {
                                        ALLOC_GROW(list, counter + 1, alloc);
                                        list[counter++] = linked;
                                }
                }
                closedir(dir);
        }
        ALLOC_GROW(list, counter + 1, alloc);
        list[counter] = NULL;
        return list;
}

char *find_shared_symref(const char *symref, const char *target)
{
        char *existing = NULL;
        struct strbuf path = STRBUF_INIT;
        struct strbuf sb = STRBUF_INIT;
        struct worktree **worktrees = get_worktrees();
        int i = 0;

        for (i = 0; worktrees[i]; i++) {
                strbuf_reset(&path);
                strbuf_reset(&sb);
                strbuf_addf(&path, "%s/%s", worktrees[i]->git_dir, symref);

                if (parse_ref(path.buf, &sb, NULL)) {
                        continue;
                }

                if (!strcmp(sb.buf, target)) {
                        existing = xstrdup(worktrees[i]->path);
                        break;
                }
        }

        strbuf_release(&path);
        strbuf_release(&sb);
        free_worktrees(worktrees);

        return existing;
}