/*

 * Copyright (C) the libgit2 contributors. All rights reserved.

 *

 * This file is part of libgit2, distributed under the GNU GPL v2 with

 * a Linking Exception. For full terms see the included COPYING file.

 */

#include "filebuf.h"

#include "futils.h"

static const size_t WRITE_BUFFER_SIZE = (4096 * 2);

enum buferr_t {

  BUFERR_OK = 0,

  BUFERR_WRITE,

  BUFERR_ZLIB,

  BUFERR_MEM

};

#define ENSURE_BUF_OK(buf) if ((buf)->last_error != BUFERR_OK) { return -1; }

static int verify_last_error(git_filebuf *file)

{

  switch (file->last_error) {

  case BUFERR_WRITE:

    git_error_set(GIT_ERROR_OS, "failed to write out file");

    return -1;

  case BUFERR_MEM:

    git_error_set_oom();

    return -1;

  case BUFERR_ZLIB:

    git_error_set(GIT_ERROR_ZLIB,

      "Buffer error when writing out ZLib data");

    return -1;

  default:

    return 0;

  }

}

static int lock_file(git_filebuf *file, int flags, mode_t mode)

{

  if (git_fs_path_exists(file->path_lock) == true) {

    git_error_clear(); /* actual OS error code just confuses */

    git_error_set(GIT_ERROR_OS,

      "failed to lock file '%s' for writing", file->path_lock);

    return GIT_ELOCKED;

  }

  /* create path to the file buffer is required */

  if (flags & GIT_FILEBUF_CREATE_LEADING_DIRS) {

    /* XXX: Should dirmode here be configurable? Or is 0777 always fine? */

    file->fd = git_futils_creat_locked_withpath(file->path_lock, 0777, mode);

  } else {

    file->fd = git_futils_creat_locked(file->path_lock, mode);

  }

  if (file->fd < 0)

    return file->fd;

  file->fd_is_open = true;

  if ((flags & GIT_FILEBUF_APPEND) && git_fs_path_exists(file->path_original) == true) {

    git_file source;

    char buffer[GIT_BUFSIZE_FILEIO];

    ssize_t read_bytes;

    int error = 0;

    source = p_open(file->path_original, O_RDONLY);

    if (source < 0) {

      git_error_set(GIT_ERROR_OS,

        "failed to open file '%s' for reading",

        file->path_original);

      return -1;

    }

    while ((read_bytes = p_read(source, buffer, sizeof(buffer))) > 0) {

      if ((error = p_write(file->fd, buffer, read_bytes)) < 0)

        break;

      if (file->compute_digest)

        git_hash_update(&file->digest, buffer, read_bytes);

    }

    p_close(source);

    if (read_bytes < 0) {

      git_error_set(GIT_ERROR_OS, "failed to read file '%s'", file->path_original);

      return -1;

    } else if (error < 0) {

      git_error_set(GIT_ERROR_OS, "failed to write file '%s'", file->path_lock);

      return -1;

    }

  }

  return 0;

}

void git_filebuf_cleanup(git_filebuf *file)

{

  if (file->fd_is_open && file->fd >= 0)

    p_close(file->fd);

  if (file->created_lock && !file->did_rename && file->path_lock && git_fs_path_exists(file->path_lock))

    p_unlink(file->path_lock);

  if (file->compute_digest) {

    git_hash_ctx_cleanup(&file->digest);

    file->compute_digest = 0;

  }

  if (file->buffer)

    git__free(file->buffer);

  /* use the presence of z_buf to decide if we need to deflateEnd */

  if (file->z_buf) {

    git__free(file->z_buf);

    deflateEnd(&file->zs);

  }

  if (file->path_original)

    git__free(file->path_original);

  if (file->path_lock)

    git__free(file->path_lock);

  memset(file, 0x0, sizeof(git_filebuf));

  file->fd = -1;

}

GIT_INLINE(int) flush_buffer(git_filebuf *file)

{

  int result = file->write(file, file->buffer, file->buf_pos);

  file->buf_pos = 0;

  return result;

}

int git_filebuf_flush(git_filebuf *file)

{

  return flush_buffer(file);

}

static int write_normal(git_filebuf *file, void *source, size_t len)

{

  if (len > 0) {

    if (p_write(file->fd, (void *)source, len) < 0) {

      file->last_error = BUFERR_WRITE;

      return -1;

    }

    if (file->compute_digest)

      git_hash_update(&file->digest, source, len);

  }

  return 0;

}

static int write_deflate(git_filebuf *file, void *source, size_t len)

{

  z_stream *zs = &file->zs;

  if (len > 0 || file->flush_mode == Z_FINISH) {

    zs->next_in = source;

    zs->avail_in = (uInt)len;

    do {

      size_t have;

      zs->next_out = file->z_buf;

      zs->avail_out = (uInt)file->buf_size;

      if (deflate(zs, file->flush_mode) == Z_STREAM_ERROR) {

        file->last_error = BUFERR_ZLIB;

        return -1;

      }

      have = file->buf_size - (size_t)zs->avail_out;

      if (p_write(file->fd, file->z_buf, have) < 0) {

        file->last_error = BUFERR_WRITE;

        return -1;

      }

    } while (zs->avail_out == 0);

    GIT_ASSERT(zs->avail_in == 0);

    if (file->compute_digest)

      git_hash_update(&file->digest, source, len);

  }

  return 0;

}

#define MAX_SYMLINK_DEPTH 5

static int resolve_symlink(git_str *out, const char *path)

{

  int i, error, root;

  ssize_t ret;

  struct stat st;

  git_str curpath = GIT_STR_INIT, target = GIT_STR_INIT;

  if ((error = git_str_grow(&target, GIT_PATH_MAX + 1)) < 0 ||

      (error = git_str_puts(&curpath, path)) < 0)

    return error;

  for (i = 0; i < MAX_SYMLINK_DEPTH; i++) {

    error = p_lstat(curpath.ptr, &st);

    if (error < 0 && errno == ENOENT) {

      error = git_str_puts(out, curpath.ptr);

      goto cleanup;

    }

    if (error < 0) {

      git_error_set(GIT_ERROR_OS, "failed to stat '%s'", curpath.ptr);

      error = -1;

      goto cleanup;

    }

    if (!S_ISLNK(st.st_mode)) {

      error = git_str_puts(out, curpath.ptr);

      goto cleanup;

    }

    ret = p_readlink(curpath.ptr, target.ptr, GIT_PATH_MAX);

    if (ret < 0) {

      git_error_set(GIT_ERROR_OS, "failed to read symlink '%s'", curpath.ptr);

      error = -1;

      goto cleanup;

    }

    if (ret == GIT_PATH_MAX) {

      git_error_set(GIT_ERROR_INVALID, "symlink target too long");

      error = -1;

      goto cleanup;

    }

    /* readlink(2) won't NUL-terminate for us */

    target.ptr[ret] = '\0';

    target.size = ret;

    root = git_fs_path_root(target.ptr);

    if (root >= 0) {

      if ((error = git_str_sets(&curpath, target.ptr)) < 0)

        goto cleanup;

    } else {

      git_str dir = GIT_STR_INIT;

      if ((error = git_fs_path_dirname_r(&dir, curpath.ptr)) < 0)

        goto cleanup;

      git_str_swap(&curpath, &dir);

      git_str_dispose(&dir);

      if ((error = git_fs_path_apply_relative(&curpath, target.ptr)) < 0)

        goto cleanup;

    }

  }

  git_error_set(GIT_ERROR_INVALID, "maximum symlink depth reached");

  error = -1;

cleanup:

  git_str_dispose(&curpath);

  git_str_dispose(&target);

  return error;

}

int git_filebuf_open(git_filebuf *file, const char *path, int flags, mode_t mode)

{

  return git_filebuf_open_withsize(file, path, flags, mode, WRITE_BUFFER_SIZE);

}

int git_filebuf_open_withsize(git_filebuf *file, const char *path, int flags, mode_t mode, size_t size)

{

  int compression, error = -1;

  size_t path_len, alloc_len;

  GIT_ASSERT_ARG(file);

  GIT_ASSERT_ARG(path);

  GIT_ASSERT(file->buffer == NULL);

  memset(file, 0x0, sizeof(git_filebuf));

  if (flags & GIT_FILEBUF_DO_NOT_BUFFER)

    file->do_not_buffer = true;

  if (flags & GIT_FILEBUF_FSYNC)

    file->do_fsync = true;

  file->buf_size = size;

  file->buf_pos = 0;

  file->fd = -1;

  file->last_error = BUFERR_OK;

  /* Allocate the main cache buffer */

  if (!file->do_not_buffer) {

    file->buffer = git__malloc(file->buf_size);

    GIT_ERROR_CHECK_ALLOC(file->buffer);

  }

  /* If we are hashing on-write, allocate a new hash context */

  if (flags & GIT_FILEBUF_HASH_SHA1) {

    file->compute_digest = 1;

    if (git_hash_ctx_init(&file->digest, GIT_HASH_ALGORITHM_SHA1) < 0)

      goto cleanup;

  } else if (flags & GIT_FILEBUF_HASH_SHA256) {

    file->compute_digest = 1;

    if (git_hash_ctx_init(&file->digest, GIT_HASH_ALGORITHM_SHA256) < 0)

      goto cleanup;

  }

  compression = flags >> GIT_FILEBUF_DEFLATE_SHIFT;

  /* If we are deflating on-write, */

  if (compression != 0) {

    /* Initialize the ZLib stream */

    if (deflateInit(&file->zs, compression) != Z_OK) {

      git_error_set(GIT_ERROR_ZLIB, "failed to initialize zlib");

      goto cleanup;

    }

    /* Allocate the Zlib cache buffer */

    file->z_buf = git__malloc(file->buf_size);

    GIT_ERROR_CHECK_ALLOC(file->z_buf);

    /* Never flush */

    file->flush_mode = Z_NO_FLUSH;

    file->write = &write_deflate;

  } else {

    file->write = &write_normal;

  }

  /* If we are writing to a temp file */

  if (flags & GIT_FILEBUF_TEMPORARY) {

    git_str tmp_path = GIT_STR_INIT;

    /* Open the file as temporary for locking */

    file->fd = git_futils_mktmp(&tmp_path, path, mode);

    if (file->fd < 0) {

      git_str_dispose(&tmp_path);

      goto cleanup;

    }

    file->fd_is_open = true;

    file->created_lock = true;

    /* No original path */

    file->path_original = NULL;

    file->path_lock = git_str_detach(&tmp_path);

    GIT_ERROR_CHECK_ALLOC(file->path_lock);

  } else {

    git_str resolved_path = GIT_STR_INIT;

    if ((error = resolve_symlink(&resolved_path, path)) < 0)

      goto cleanup;

    /* Save the original path of the file */

    path_len = resolved_path.size;

    file->path_original = git_str_detach(&resolved_path);

    /* create the locking path by appending ".lock" to the original */

    GIT_ERROR_CHECK_ALLOC_ADD(&alloc_len, path_len, GIT_FILELOCK_EXTLENGTH);

    file->path_lock = git__malloc(alloc_len);

    GIT_ERROR_CHECK_ALLOC(file->path_lock);

    memcpy(file->path_lock, file->path_original, path_len);

    memcpy(file->path_lock + path_len, GIT_FILELOCK_EXTENSION, GIT_FILELOCK_EXTLENGTH);

    if (git_fs_path_isdir(file->path_original)) {

      git_error_set(GIT_ERROR_FILESYSTEM, "path '%s' is a directory", file->path_original);

      error = GIT_EDIRECTORY;

      goto cleanup;

    }

    /* open the file for locking */

    if ((error = lock_file(file, flags, mode)) < 0)

      goto cleanup;

    file->created_lock = true;

  }

  return 0;

cleanup:

  git_filebuf_cleanup(file);

  return error;

}

int git_filebuf_hash(unsigned char *out, git_filebuf *file)

{

  GIT_ASSERT_ARG(out);

  GIT_ASSERT_ARG(file);

  GIT_ASSERT_ARG(file->compute_digest);

  flush_buffer(file);

  if (verify_last_error(file) < 0)

    return -1;

  git_hash_final(out, &file->digest);

  git_hash_ctx_cleanup(&file->digest);

  file->compute_digest = 0;

  return 0;

}

int git_filebuf_commit_at(git_filebuf *file, const char *path)

{

  git__free(file->path_original);

  file->path_original = git__strdup(path);

  GIT_ERROR_CHECK_ALLOC(file->path_original);

  return git_filebuf_commit(file);

}

int git_filebuf_commit(git_filebuf *file)

{

  /* temporary files cannot be committed */

  GIT_ASSERT_ARG(file);

  GIT_ASSERT(file->path_original);

  file->flush_mode = Z_FINISH;

  flush_buffer(file);

  if (verify_last_error(file) < 0)

    goto on_error;

  file->fd_is_open = false;

  if (file->do_fsync && p_fsync(file->fd) < 0) {

    git_error_set(GIT_ERROR_OS, "failed to fsync '%s'", file->path_lock);

    goto on_error;

  }

  if (p_close(file->fd) < 0) {

    git_error_set(GIT_ERROR_OS, "failed to close file at '%s'", file->path_lock);

    goto on_error;

  }

  file->fd = -1;

  if (p_rename(file->path_lock, file->path_original) < 0) {

    git_error_set(GIT_ERROR_OS, "failed to rename lockfile to '%s'", file->path_original);

    goto on_error;

  }

  if (file->do_fsync && git_futils_fsync_parent(file->path_original) < 0)

    goto on_error;

  file->did_rename = true;

  git_filebuf_cleanup(file);

  return 0;

on_error:

  git_filebuf_cleanup(file);

  return -1;

}

GIT_INLINE(void) add_to_cache(git_filebuf *file, const void *buf, size_t len)

{

  memcpy(file->buffer + file->buf_pos, buf, len);

  file->buf_pos += len;

}

int git_filebuf_write(git_filebuf *file, const void *buff, size_t len)

{

  const unsigned char *buf = buff;

  ENSURE_BUF_OK(file);

  if (file->do_not_buffer)

    return file->write(file, (void *)buff, len);

  for (;;) {

    size_t space_left = file->buf_size - file->buf_pos;

    /* cache if it's small */

    if (space_left > len) {

      add_to_cache(file, buf, len);

      return 0;

    }

    add_to_cache(file, buf, space_left);

    if (flush_buffer(file) < 0)

      return -1;

    len -= space_left;

    buf += space_left;

  }

}

int git_filebuf_reserve(git_filebuf *file, void **buffer, size_t len)

{

  size_t space_left = file->buf_size - file->buf_pos;

  *buffer = NULL;

  ENSURE_BUF_OK(file);

  if (len > file->buf_size) {

    file->last_error = BUFERR_MEM;

    return -1;

  }

  if (space_left <= len) {

    if (flush_buffer(file) < 0)

      return -1;

  }

  *buffer = (file->buffer + file->buf_pos);

  file->buf_pos += len;

  return 0;

}

int git_filebuf_printf(git_filebuf *file, const char *format, ...)

{

  va_list arglist;

  size_t space_left, len, alloclen;

  int written, res;

  char *tmp_buffer;

  ENSURE_BUF_OK(file);

  space_left = file->buf_size - file->buf_pos;

  do {

    va_start(arglist, format);

    written = p_vsnprintf((char *)file->buffer + file->buf_pos, space_left, format, arglist);

    va_end(arglist);

    if (written < 0) {

      file->last_error = BUFERR_MEM;

      return -1;

    }

    len = written;

    if (len + 1 <= space_left) {

      file->buf_pos += len;

      return 0;

    }

    if (flush_buffer(file) < 0)

      return -1;

    space_left = file->buf_size - file->buf_pos;

  } while (len + 1 <= space_left);

  if (GIT_ADD_SIZET_OVERFLOW(&alloclen, len, 1) ||

    !(tmp_buffer = git__malloc(alloclen))) {

    file->last_error = BUFERR_MEM;

    return -1;

  }

  va_start(arglist, format);

  written = p_vsnprintf(tmp_buffer, len + 1, format, arglist);

  va_end(arglist);

  if (written < 0) {

    git__free(tmp_buffer);

    file->last_error = BUFERR_MEM;

    return -1;

  }

  res = git_filebuf_write(file, tmp_buffer, len);

  git__free(tmp_buffer);

  return res;

}

int git_filebuf_stats(time_t *mtime, size_t *size, git_filebuf *file)

{

  int res;

  struct stat st;

  if (file->fd_is_open)

    res = p_fstat(file->fd, &st);

  else

    res = p_stat(file->path_original, &st);

  if (res < 0) {

    git_error_set(GIT_ERROR_OS, "could not get stat info for '%s'",

      file->path_original);

    return res;

  }

  if (mtime)

    *mtime = st.st_mtime;

  if (size)

    *size = (size_t)st.st_size;

  return 0;

}