#include "cache.h"
#include "dir.h"
#include "iterator.h"
#include "dir-iterator.h"

struct dir_iterator_level {
        DIR *dir;

        /*
         * The length of the directory part of path at this level
         * (including a trailing '/'):
         */
        size_t prefix_len;
};

/*
 * The full data structure used to manage the internal directory
 * iteration state. It includes members that are not part of the
 * public interface.
 */
struct dir_iterator_int {
        struct dir_iterator base;

        /*
         * The number of levels currently on the stack. After the first
         * call to dir_iterator_begin(), if it succeeds to open the
         * first level's dir, this will always be at least 1. Then,
         * when it comes to zero the iteration is ended and this
         * struct is freed.
         */
        size_t levels_nr;

        /* The number of levels that have been allocated on the stack */
        size_t levels_alloc;

        /*
         * A stack of levels. levels[0] is the uppermost directory
         * that will be included in this iteration.
         */
        struct dir_iterator_level *levels;
};

/*
 * Push a level in the iter stack and initialize it with information from
 * the directory pointed by iter->base->path. It is assumed that this
 * strbuf points to a valid directory path. Return 0 on success and -1
 * otherwise, leaving the stack unchanged.
 */
static int push_level(struct dir_iterator_int *iter)
{
        struct dir_iterator_level *level;

        ALLOC_GROW(iter->levels, iter->levels_nr + 1, iter->levels_alloc);
        level = &iter->levels[iter->levels_nr++];

        if (!is_dir_sep(iter->base.path.buf[iter->base.path.len - 1]))
                strbuf_addch(&iter->base.path, '/');
        level->prefix_len = iter->base.path.len;

        level->dir = opendir(iter->base.path.buf);
        if (!level->dir) {
                if (errno != ENOENT) {
                        warning_errno("error opening directory '%s'",
                                      iter->base.path.buf);
                }
                iter->levels_nr--;
                return -1;
        }

        return 0;
}

/*
 * Pop the top level on the iter stack, releasing any resources associated
 * with it. Return the new value of iter->levels_nr.
 */
static int pop_level(struct dir_iterator_int *iter)
{
        struct dir_iterator_level *level =
                &iter->levels[iter->levels_nr - 1];

        if (level->dir && closedir(level->dir))
                warning_errno("error closing directory '%s'",
                              iter->base.path.buf);
        level->dir = NULL;

        return --iter->levels_nr;
}

/*
 * Populate iter->base with the necessary information on the next iteration
 * entry, represented by the given dirent de. Return 0 on success and -1
 * otherwise.
 */
static int prepare_next_entry_data(struct dir_iterator_int *iter,
                                   struct dirent *de)
{
        strbuf_addstr(&iter->base.path, de->d_name);
        /*
         * We have to reset these because the path strbuf might have
         * been realloc()ed at the previous strbuf_addstr().
         */
        iter->base.relative_path = iter->base.path.buf +
                                   iter->levels[0].prefix_len;
        iter->base.basename = iter->base.path.buf +
                              iter->levels[iter->levels_nr - 1].prefix_len;

        if (lstat(iter->base.path.buf, &iter->base.st)) {
                if (errno != ENOENT)
                        warning_errno("failed to stat '%s'", iter->base.path.buf);
                return -1;
        }

        return 0;
}

int dir_iterator_advance(struct dir_iterator *dir_iterator)
{
        struct dir_iterator_int *iter =
                (struct dir_iterator_int *)dir_iterator;

        if (S_ISDIR(iter->base.st.st_mode)) {
                if (push_level(iter) && iter->levels_nr == 0) {
                        /* Pushing the first level failed */
                        return dir_iterator_abort(dir_iterator);
                }
        }

        /* Loop until we find an entry that we can give back to the caller. */
        while (1) {
                struct dirent *de;
                struct dir_iterator_level *level =
                        &iter->levels[iter->levels_nr - 1];

                strbuf_setlen(&iter->base.path, level->prefix_len);
                errno = 0;
                de = readdir(level->dir);

                if (!de) {
                        if (errno)
                                warning_errno("error reading directory '%s'",
                                              iter->base.path.buf);
                        else if (pop_level(iter) == 0)
                                return dir_iterator_abort(dir_iterator);
                        continue;
                }

                if (is_dot_or_dotdot(de->d_name))
                        continue;

                if (prepare_next_entry_data(iter, de))
                        continue;

                return ITER_OK;
        }
}

int dir_iterator_abort(struct dir_iterator *dir_iterator)
{
        struct dir_iterator_int *iter = (struct dir_iterator_int *)dir_iterator;

        for (; iter->levels_nr; iter->levels_nr--) {
                struct dir_iterator_level *level =
                        &iter->levels[iter->levels_nr - 1];

                if (level->dir && closedir(level->dir)) {
                        int saved_errno = errno;
                        strbuf_setlen(&iter->base.path, level->prefix_len);
                        errno = saved_errno;
                        warning_errno("error closing directory '%s'",
                                      iter->base.path.buf);
                }
        }

        free(iter->levels);
        strbuf_release(&iter->base.path);
        free(iter);
        return ITER_DONE;
}

struct dir_iterator *dir_iterator_begin(const char *path)
{
        struct dir_iterator_int *iter = xcalloc(1, sizeof(*iter));
        struct dir_iterator *dir_iterator = &iter->base;
        int saved_errno;

        strbuf_init(&iter->base.path, PATH_MAX);
        strbuf_addstr(&iter->base.path, path);

        ALLOC_GROW(iter->levels, 10, iter->levels_alloc);
        iter->levels_nr = 0;

        /*
         * Note: stat already checks for NULL or empty strings and
         * inexistent paths.
         */
        if (stat(iter->base.path.buf, &iter->base.st) < 0) {
                saved_errno = errno;
                goto error_out;
        }

        if (!S_ISDIR(iter->base.st.st_mode)) {
                saved_errno = ENOTDIR;
                goto error_out;
        }

        return dir_iterator;

error_out:
        dir_iterator_abort(dir_iterator);
        errno = saved_errno;
        return NULL;
}