#include <u.h>
#include <base.h>
#include <base/macro/map.h>
#include <dirent.h>

/*
 * path history
 */
struct Key
{
    ino_t ino;
    dev_t dev;
};

#define hash(k) ((int32)k.ino ^ (int32)k.dev)
#define equal(k1, k2) (k1.ino == k2.ino && k1.dev == k2.dev)

struct fs·History
{
    SET_STRUCT_BODY(struct Key);
};

static
int
morehistory(fs·History *h, int n)
{
    SET_GROW(h, struct Key, n, hash, sys·Memory, nil);
}

static
int
addentry(fs·History *h, struct Key key, int *err)
{
    SET_PUT(h, key, hash, equal, morehistory, err);
}

static
void
forget(fs·History *h)
{
    if (!h)
        return;

    SET_RESET(h);
}

static
void
delete(fs·History *h)
{
    SET_FREE(h, sys·Memory, nil);
}

#undef hash
#undef equal

static
char *
strcpyn(char *dst, char *src, int n)
{
    while(*src && n-- > 0)
        *dst++ = *src++;

    *dst = 0;
    return dst;
}

/*
 * main functions
 */

int
fs·init(fs·Walker *fs, char *path)
{
    fs->base = fs->end = fs->path;

    if (!path || !path[0]) {
        path = getcwd(fs->path, arrlen(fs->path));
        if (!path)
            return 1;
        fs->end += strlen(path);
    } else 
        fs->end = strcpyn(fs->base, path, arrlen(fs->path));

    if (fs->path[0] != '/')
        fs->fd = AT_FDCWD;

    if (!fs->hist && !(fs->flags & fs·nolinks))
        fs->hist = calloc(1, sizeof(*fs->hist));

    return 0;
}

void
fs·fini(fs·Walker *fs)
{
    if (fs->hist) {
        delete(fs->hist);
        free(fs->hist);
    }
}

void
fs·walk(fs·Walker *fs)
{
    char *e, *b;
    DIR *dir;
    int new, fd, ofd, flags;
    fs·History *h;
    struct dirent *d;
    io·Stat cwd;
    struct fs·Entry *it;

    flags = 0;
    if(fs->flags & fs·nolinks)
        flags |= AT_SYMLINK_NOFOLLOW;

    /* get info for base relative to current fd */
    if(fstatat(fs->fd, fs->base, &cwd, flags) < 0){
        if(fs->flags & fs·verbose)
            errorf("stat: %s", fs->path);
        return;
    }

    /* if we hit a file, finish! */
    if(!S_ISDIR(cwd.st_mode)) {
        fs->func(fs->data, fs->base, fs->path, &cwd);
        return;
    }

    /* have we been here before? (cycle detection) */
    /* if not, add to our path history */
    if (!(fs->flags & fs·nolinks)) {
        addentry(fs->hist, (struct Key){.dev=cwd.st_dev, .ino=cwd.st_ino}, &new);
        if (!new)
            return;
    }

    /* 
     * operate on directory first if preorder traversal 
     * truncate recursion if callback returns an error code
     */ 
    if (fs->flags & fs·preorder) {
        if (fs->func(fs->data, fs->base, fs->path, &cwd))
            return;
    }

    /* open directory */
    if(!fs->max || fs->lev + 1 < fs->max) {
        fd = openat(fs->fd, fs->base, O_RDONLY | O_CLOEXEC | O_DIRECTORY);
        if (fd < 0)
            errorf("open %s:", fs->path);

        if (!(dir=fdopendir(fd))) {
            if(fs->flags & fs·verbose)
                errorf("fdopendir: %s", fs->path);
            return;
        }

        ofd = fs->fd, fs->fd = fd;

        /* traverse children */
        e = fs->end, b = fs->base;
        if (fs->end[-1] != '/')
            *fs->end++ = '/';

        fs->base = fs->end;
        while((d = readdir(dir))) {
            if (*d->d_name == '.') 
            if (d->d_name[1] == 0 ||                       /* . */ 
               (d->d_name[1] == '.' && d->d_name[2] == 0)) /* .. */ 
                continue;

            fs->end = strcpyn(fs->base, d->d_name, arrend(fs->path) - fs->base);

            fs->lev++;
            fs·walk(fs);
            fs->lev--;
        }
        *e      = 0;
        fs->fd  = ofd;
        fs->end = e, fs->base = b;
        closedir(dir);
    }

    /* operate on directory if postorder (default) traversal */
    if (!(fs->flags & fs·preorder))
        fs->func(fs->data, fs->base, fs->path, &cwd);

    if (!fs->lev)
        forget(fs->hist);
}