/* lib9660: a simple ISO9660 reader library especially suited to embedded
 *          systems
 *
 * SPDX-License-Identifier: LicenseRef-ISC1
 * SPDX-FileCopyrightText: © 2014 Erin Shepherd
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice appears in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
 * OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 * PERFORMANCE OF THIS SOFTWARE.
 */

#include <fs/iso9660fs/lib9660.h>
#include <libk/string.h>
#include <sys/debug.h>

#define SEEK_END L9660_SEEK_END
#define SEEK_SET L9660_SEEK_SET
#define SEEK_CUR L9660_SEEK_CUR

#define DENT_EXISTS      (1 << 0)
#define DENT_ISDIR       (1 << 1)
#define DENT_ASSOCIATED  (1 << 2)
#define DENT_RECORD      (1 << 3)
#define DENT_PROTECTION  (1 << 4)
#define DENT_MULTIEXTENT (1 << 5)

#define PVD(vdesc) ((l9660_vdesc_primary*)(vdesc))

#ifdef L9660_BIG_ENDIAN
#define READ16(v) (((v).be[1]) | ((v).be[0] << 8))
#define READ32(v) (((v).be[3]) | ((v).be[2] << 8) | ((v).be[1]) << 16 | ((v).be[0] << 24))
#else
#define READ16(v) (((v).le[0]) | ((v).le[1] << 8))
#define READ32(v) (((v).le[0]) | ((v).le[1] << 8) | ((v).le[2]) << 16 | ((v).le[3] << 24))
#endif

#define HAVEBUFFER(f) (true)
#define BUF(f)        ((f)->buf)

#define ROCKRIDGE_FILENAME_MAX 0xFF

#define NM_CONTINUE 0x01
#define NM_CURRENT  0x02
#define NM_PARENT   0x04

static char* strchrnul(const char* s, int c) {
  while (*s && *s != c)
    s++;
  return (char*)s;
}

static inline uint16_t fsectoff(l9660_file* f) { return f->position % 2048; }

static inline uint32_t fsector(l9660_file* f) { return f->position / 2048; }

static inline uint32_t fnextsectpos(l9660_file* f) { return (f->position + 2047) & ~2047; }

const char* l9660_get_rockridge_name(l9660_dirent* dirent, char* out, size_t* out_len) {
  uint8_t* ptr = (uint8_t*)dirent + sizeof(*dirent) + dirent->name_len;

  if (!(dirent->name_len & 1))
    ptr++;

  uint8_t* end = (uint8_t*)dirent + dirent->length;

  size_t total = 0;
  bool found = false;

  while (ptr + sizeof(l9660_su_field) <= end) {
    l9660_su_field* sufield = (l9660_su_field*)ptr;

    if (sufield->len < 5 || ptr + sufield->len > end)
      break;

    if (sufield->sign[0] == 'N' && sufield->sign[1] == 'M') {
      uint8_t flags = sufield->data[0];

      if ((flags & NM_CURRENT)) {
        out[0] = '.';
        *out_len = 1;
        return out;
      }

      if ((flags & NM_PARENT)) {
        out[0] = '.';
        out[1] = '.';
        *out_len = 2;
        return out;
      }

      size_t part_len = sufield->len - 5;
      if (total + part_len > ROCKRIDGE_FILENAME_MAX)
        part_len = ROCKRIDGE_FILENAME_MAX - total;

      memcpy(out + total, &sufield->data[1], part_len);
      total += part_len;
      found = true;

      if (total < ROCKRIDGE_FILENAME_MAX)
        out[total] = '\0';
      else
        out[ROCKRIDGE_FILENAME_MAX - 1] = '\0';

      if (!(flags & NM_CONTINUE))
        break;
    }

    ptr += sufield->len;
  }

  if (!found)
    return NULL;

  *out_len = total;

  return out;
}

l9660_status l9660_openfs(l9660_fs* fs,
                          bool (*read_sector)(l9660_fs* fs, void* buf, uint32_t sector)) {
  fs->read_sector = read_sector;

#ifndef L9660_SINGLEBUFFER
  l9660_vdesc_primary* pvd = PVD(&fs->pvd);
#else
  last_file = NULL;
  l9660_vdesc_primary* pvd = PVD(gbuf);
#endif
  uint32_t idx = 0x10;
  for (;;) {
    // Read next sector
    if (!read_sector(fs, pvd, idx))
      return L9660_EIO;

    // Validate magic
    if (memcmp(pvd->hdr.magic, "CD001", 5) != 0)
      return L9660_EBADFS;

    if (pvd->hdr.type == 1)
      break; // Found PVD
    else if (pvd->hdr.type == 255)
      return L9660_EBADFS;
  }

#ifdef L9660_SINGLEBUFFER
  memcpy(&fs->root_dir_ent, &pvd->root_dir_ent, pvd->root_dir_ent.length);
#endif

  return L9660_OK;
}

l9660_status l9660_fs_open_root(l9660_dir* dir, l9660_fs* fs) {
  l9660_file* f = &dir->file;
#ifndef L9660_SINGLEBUFFER
  l9660_dirent* dirent = &PVD(&fs->pvd)->rde.root_dir_ent;
#else
  l9660_dirent* dirent = &fs->root_dir_ent;
#endif

  f->fs = fs;
  f->first_sector = READ32(dirent->sector);
  f->length = READ32(dirent->size);
  f->position = 0;

  return L9660_OK;
}

static l9660_status buffer(l9660_file* f) {
#ifdef L9660_SINGLEBUFFER
  last_file = f;
#endif
  if (!f->fs->read_sector(f->fs, BUF(f), f->first_sector + f->position / 2048))
    return L9660_EIO;
  else
    return L9660_OK;
}

static l9660_status prebuffer(l9660_file* f) {
  if (!HAVEBUFFER(f) || (f->position % 2048) == 0)
    return buffer(f);
  else
    return L9660_OK;
}

static l9660_status openat_raw(l9660_file* child, l9660_dir* parent, const char* name, bool isdir) {
  char rr_namebuf[ROCKRIDGE_FILENAME_MAX];
  l9660_status rv;
  l9660_dirent* dent = NULL;
  size_t dent_rr_name_len = 0;
  if ((rv = l9660_seekdir(parent, 0)))
    return rv;

  do {
    const char* seg = name;
    name = strchrnul(name, '/');
    size_t seglen = name - seg;

    /* ISO9660 stores '.' as '\0' */
    if (seglen == 1 && *seg == '.')
      seg = "\0";

    /* ISO9660 stores ".." as '\1' */
    if (seglen == 2 && seg[0] == '.' && seg[1] == '.') {
      seg = "\1";
      seglen = 1;
    }

    for (;;) {
      if ((rv = l9660_readdir(parent, &dent)))
        return rv;

      /* EOD */
      if (!dent)
        return L9660_ENOENT;

      const char* rockridge_name = l9660_get_rockridge_name(dent, rr_namebuf, &dent_rr_name_len);

      if (rockridge_name == NULL) {
        /* wrong length */
        if (seglen != dent->name_len)
          continue;

        /* check name */
        if (memcmp(seg, dent->name, seglen) != 0)
          continue;

        /* check for a revision tag */
        if (dent->name_len > seglen && dent->name[seglen] != ';')
          continue;

        /* all tests pass */
        break;
      } else {
        if (seglen == dent_rr_name_len && memcmp(seg, rockridge_name, seglen) == 0)
          break;

        continue;
      }
    }

    child->fs = parent->file.fs;
    child->first_sector = READ32(dent->sector);
    child->length = READ32(dent->size);
    child->position = 0;

    if (*name && (dent->flags & DENT_ISDIR) == 0)
      return L9660_ENOTDIR;

    parent = (l9660_dir*)child;

    if (*name == '/')
      name++;
  } while (*name);

  if (isdir) {
    if ((dent->flags & DENT_ISDIR) == 0)
      return L9660_ENOTDIR;
  } else {
    if ((dent->flags & DENT_ISDIR) != 0)
      return L9660_ENOTFILE;
  }

  return L9660_OK;
}

l9660_status l9660_opendirat(l9660_dir* dir, l9660_dir* parent, const char* path) {
  return openat_raw(&dir->file, parent, path, true);
}

static inline unsigned aligneven(unsigned v) { return v + (v & 1); }

l9660_status l9660_readdir(l9660_dir* dir, l9660_dirent** pdirent) {
  l9660_status rv;
  l9660_file* f = &dir->file;

rebuffer:
  if (f->position >= f->length) {
    *pdirent = NULL;
    return L9660_OK;
  }

  if ((rv = prebuffer(f)))
    return rv;

  char* off = BUF(f) + fsectoff(f);
  if (*off == 0) {
    // Padded end of sector
    f->position = fnextsectpos(f);
    goto rebuffer;
  }

  l9660_dirent* dirent = (l9660_dirent*)off;
  f->position += aligneven(dirent->length);

  *pdirent = dirent;
  return L9660_OK;
}

l9660_status l9660_openat(l9660_file* child, l9660_dir* parent, const char* name) {
  return openat_raw(child, parent, name, false);
}

/*! Seek the file to \p offset from \p whence */
l9660_status l9660_seek(l9660_file* f, int whence, int32_t offset) {
  l9660_status rv;
  uint32_t cursect = fsector(f);

  switch (whence) {
  case SEEK_SET:
    f->position = offset;
    break;

  case SEEK_CUR:
    f->position = f->position + offset;
    break;

  case SEEK_END:
    f->position = f->length - offset;
    break;
  }

  if (fsector(f) != cursect && fsectoff(f) != 0) {
    if ((rv = buffer(f)))
      return rv;
  }

  return L9660_OK;
}

uint32_t l9660_tell(l9660_file* f) { return f->position; }

l9660_status l9660_read(l9660_file* f, void* buf, size_t size, size_t* read) {
  l9660_status rv;

  if ((rv = prebuffer(f)))
    return rv;

  uint16_t rem = 2048 - fsectoff(f);
  if (rem > f->length - f->position)
    rem = f->length - f->position;
  if (rem < size)
    size = rem;

  memcpy(buf, BUF(f) + fsectoff(f), size);

  *read = size;
  f->position += size;

  return L9660_OK;
}