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#include <string.h>

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#include <errno.h>

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#include <stdlib.h>

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#include <event2/event.h>

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#include <fuse/fuse_opt.h>

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#include "lib/common.h"

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#include "lib/math.h"

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#include "lib/signals.h"

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#include "evfuse.h"

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const char *file_name = "hello";

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const char *file_data = "Hello World\n";

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static struct hello {

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    struct event_base *ev_base;

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    struct signals *signals;

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    struct evfuse *ev_fuse;

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} ctx;

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void hello_init (void *userdata, struct fuse_conn_info *conn) {

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    INFO("[hello.init] userdata=%p, conn=%p", userdata, conn);

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}

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void hello_destroy (void *userdata) {

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    INFO("[hello.destroy] userdata=%p", userdata);

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}

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void hello_lookup (fuse_req_t req, fuse_ino_t parent, const char *name) {

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    struct fuse_entry_param e;

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    INFO("[hello.lookup] (uid=%d, pid=%d) parent=%lu name=%s", fuse_req_ctx(req)->uid, fuse_req_ctx(req)->pid, parent, name);

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    // the world is flat

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    if (parent != 1 || strcmp(name, file_name)) {

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        fuse_reply_err(req, ENOENT);

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        return;

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    }

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    // set up the entry

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    memset(&e, 0, sizeof(e));

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    e.ino = 2;

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    e.attr_timeout = 1.0;

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    e.entry_timeout = 1.0;

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    e.attr.st_mode = S_IFREG | 0444;

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    e.attr.st_nlink = 1;

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    e.attr.st_size = strlen(file_data);

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    // reply

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    fuse_reply_entry(req, &e);

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}

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void hello_getattr (fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi) {

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    struct stat stbuf;

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    INFO("[hello.getattr] (uid=%d, pid=%d) ino=%lu, fi=%p", fuse_req_ctx(req)->uid, fuse_req_ctx(req)->pid, ino, fi);

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    memset(&stbuf, 0, sizeof(stbuf));

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    // the root dir, or the file?

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    if (ino == 1) {

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        stbuf.st_mode = S_IFDIR | 0555;

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        stbuf.st_nlink = 2;

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    } else if (ino == 2) {

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        stbuf.st_mode = S_IFREG | 0444;

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        stbuf.st_nlink = 1;

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        stbuf.st_size = strlen(file_data);

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    } else {

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        fuse_reply_err(req, ENOENT);

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        return;

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    }

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    // reply

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    fuse_reply_attr(req, &stbuf, 1.0);

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}

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struct dirbuf {

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    char *buf;

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    size_t len;

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    size_t off;

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};

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#define DIRBUF_INITIAL_SIZE 1024

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static int dirbuf_init (struct dirbuf *buf) {

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    buf->len = DIRBUF_INITIAL_SIZE;

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    buf->off = 0;

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    // allocate the mem

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    if ((buf->buf = malloc(buf->len)) == NULL)

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        ERROR("malloc");

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    // ok

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    return 0;

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error:

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    return -1;

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}

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/*

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 * Ensure that `new` bytes fit into the buf. If they already fit, update offset and set *retry = 0. If they don't fit,

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 * grow buf and set *retry = 1.

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 *

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 * Returns 0 on success, -1 on failure (don't retry).

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 */

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static int dirbuf_update (struct dirbuf *buf, size_t new, int *retry) {

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    if (buf->off + new <= buf->len) {

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        INFO("\thello.dirbuf_update: update offset by %zu from %zu -> %zu", new, buf->off, buf->off + new);

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        // great, it fit, update offset and return

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        buf->off += new;

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        *retry = 0;

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    } else {

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        size_t old_len = buf->len;

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        // calc new size

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        do {

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            buf->len *= 2;

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        } while (buf->off + new > buf->len);

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        INFO("\thello.dirbuf_update: grow size for %zu from %zu -> %zu", new, old_len, buf->len);

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        // realloc

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        if ((buf->buf = realloc(buf->buf, buf->len)) == NULL)

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            ERROR("realloc");

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        // done, just retry

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        *retry = 1;

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    }

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    // success

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    return 0;

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error:

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    return -1;

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}

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static int dirbuf_add (fuse_req_t req, size_t req_size, off_t req_off, struct dirbuf *buf, off_t ent_off, off_t next_off, const char *ent_name, fuse_ino_t ent_ino) {

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    struct stat stbuf;

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    size_t ent_size;

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    int err, retry;

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    INFO("\thello.dirbuf_add: req_size=%zu, req_off=%zu, buf->len=%zu, buf->off=%zu, ent_off=%zu, next_off=%zu, ent_name=%s, ent_ino=%lu",

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        req_size, req_off, buf->len, buf->off, ent_off, next_off, ent_name, ent_ino);

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    // skip entries as needed

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    if (buf->len >= req_size || ent_off < req_off) 

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        return 0;

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    // set ino

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    stbuf.st_ino = ent_ino;

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    // add the dirent and update dirbuf until it fits

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    do {

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        ent_size = fuse_add_direntry(req, buf->buf + buf->off, buf->len - buf->off, ent_name, &stbuf, next_off);

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    } while (!(err = dirbuf_update(buf, ent_size, &retry)) && retry);

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    if (err)

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        return err;

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    // success

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    return 0;

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}

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static int dirbuf_done (fuse_req_t req, struct dirbuf *buf, size_t req_size) {

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    int err;

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    // send the reply, return the error later

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    err = fuse_reply_buf(req, buf->buf, MIN(buf->off, req_size));

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    INFO("\thello.dirbuf_done: MIN(%zu, %zu)=%zu, err=%d", buf->off, req_size, MIN(buf->off, req_size), err);

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    // free the dirbuf

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    free(buf->buf);

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    // return the error code

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    return err;

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}

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void hello_readdir (fuse_req_t req, fuse_ino_t ino, size_t size, off_t off, struct fuse_file_info *fi) {

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    int err = 0;

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    struct dirbuf buf;

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    INFO("[hello.readdir] ino=%lu, size=%zu, off=%zu, fi=%p", ino, size, off, fi);

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    // there exists only one dir

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    if (ino != 1) {

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        fuse_reply_err(req, ENOTDIR);

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        return;

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    }

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    // fill in the dirbuf

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    if (dirbuf_init(&buf))

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        ERROR("failed to init dirbuf");

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    if (    dirbuf_add(req, size, off, &buf, 0, 1,  ".",        1)

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        ||  dirbuf_add(req, size, off, &buf, 1, 2,  "..",       1)

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        ||  dirbuf_add(req, size, off, &buf, 2, 3,  file_name,  2)

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    ) ERROR("failed to add dirents to buf");

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    // send it

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    if ((err = -dirbuf_done(req, &buf, size)))

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        EERROR(-err, "failed to send buf");

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    // success

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    return;

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error:

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    if ((err = fuse_reply_err(req, err ? err : EIO)))

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        EWARNING(err, "failed to send error reply");

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}

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struct fuse_lowlevel_ops hello_llops = {

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    .init = &hello_init,

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    .destroy = &hello_destroy,

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    .lookup = &hello_lookup,

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    .getattr = &hello_getattr,

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    .readdir = &hello_readdir,

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};

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int main (int argc, char **argv) {

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    struct fuse_args fuse_args = FUSE_ARGS_INIT(argc, argv);

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    // zero

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    memset(&ctx, 0, sizeof(ctx));

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    // init libevent

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    if ((ctx.ev_base = event_base_new()) == NULL)

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        ERROR("event_base_new");

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    // setup signals

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    if ((ctx.signals = signals_default(ctx.ev_base)) == NULL)

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        ERROR("signals_default");

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    // open fuse

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    if ((ctx.ev_fuse = evfuse_new(ctx.ev_base, &fuse_args, &hello_llops, &ctx)) == NULL)

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        ERROR("evfuse_new");

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    // run libevent

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    INFO("running libevent loop");

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    if (event_base_dispatch(ctx.ev_base))

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        PERROR("event_base_dispatch");

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    // clean shutdown

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error :

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    // cleanup

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    if (ctx.ev_fuse)

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        evfuse_close(ctx.ev_fuse);

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    if (ctx.signals)

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        signals_free(ctx.signals);

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    if (ctx.ev_base)

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        event_base_free(ctx.ev_base);

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    fuse_opt_free_args(&fuse_args);

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}

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