/* Copyright (c) 2009-2017 Dovecot authors, see the included COPYING file */

#include "lib.h"
#include "mail-storage-private.h"
#include "istream-private.h"
#include "index-mail.h"
#include "istream-mail.h"

struct mail_istream {
	struct istream_private istream;

	struct mail *mail;
	uoff_t expected_size;
	unsigned int files_read_increased:1;
	unsigned int input_has_body:1;
};

static bool i_stream_mail_try_get_cached_size(struct mail_istream *mstream)
{
	struct mail *mail = mstream->mail;
	enum mail_lookup_abort orig_lookup_abort;

	if (mstream->expected_size != (uoff_t)-1)
		return TRUE;

	/* make sure this call doesn't change any existing error message,
	   just in case there's already something important in it. */
	mail_storage_last_error_push(mail->box->storage);
	orig_lookup_abort = mail->lookup_abort;
	mail->lookup_abort = MAIL_LOOKUP_ABORT_NOT_IN_CACHE;
	if (mail_get_physical_size(mail, &mstream->expected_size) < 0)
		mstream->expected_size = (uoff_t)-1;
	mail->lookup_abort = orig_lookup_abort;
	mail_storage_last_error_pop(mail->box->storage);
	return mstream->expected_size != (uoff_t)-1;
}

static const char *
i_stream_mail_get_cached_mail_id(struct mail_istream *mstream ATTR_UNUSED)
{
#if 0
	/* FIXME: This function may get called in the middle of header parsing,
	   which then goes into parsing cached headers and causes crashes.
	   So disable this for now. Eventually it would be nice if recursion
	   was possible by each parser using its own private struct. */
	static const char *headers[] = {
		"Message-Id",
		"Date",
		"Subject"
	};
	struct mail *mail = mstream->mail;
	enum mail_lookup_abort orig_lookup_abort;
	const char *value, *ret = "";
	unsigned int i;

	orig_lookup_abort = mail->lookup_abort;
	mail->lookup_abort = MAIL_LOOKUP_ABORT_NOT_IN_CACHE;
	for (i = 0; i < N_ELEMENTS(headers); i++) {
		if (mail_get_first_header(mail, headers[i], &value) > 0) {
			ret = t_strdup_printf("%s=%s", headers[i], value);
			break;
		}
	}
	mail->lookup_abort = orig_lookup_abort;
	return ret;
#else
	return "";
#endif
}

static void
i_stream_mail_set_size_corrupted(struct mail_istream *mstream, size_t size)
{
	uoff_t cur_size = mstream->istream.istream.v_offset + size;
	const char *str, *mail_id;
	char chr;

	if (mstream->expected_size < cur_size) {
		str = "smaller";
		chr = '<';
	} else {
		str = "larger";
		chr = '>';
	}

	mail_id = i_stream_mail_get_cached_mail_id(mstream);
	if (mail_id[0] != '\0')
		mail_id = t_strconcat(", cached ", mail_id, NULL);
	io_stream_set_error(&mstream->istream.iostream,
		"Cached message size %s than expected "
		"(%"PRIuUOFF_T" %c %"PRIuUOFF_T", box=%s, UID=%u%s)", str,
		mstream->expected_size, chr, cur_size,
		mailbox_get_vname(mstream->mail->box),
		mstream->mail->uid, mail_id);
	mail_set_cache_corrupted_reason(mstream->mail, MAIL_FETCH_PHYSICAL_SIZE,
		t_strdup_printf("read(%s) failed: %s",
				i_stream_get_name(&mstream->istream.istream),
				mstream->istream.iostream.error));
	mstream->istream.istream.stream_errno = EINVAL;
}

static ssize_t
i_stream_mail_read(struct istream_private *stream)
{
	struct mail_istream *mstream = (struct mail_istream *)stream;
	size_t size;
	ssize_t ret;

	i_stream_seek(stream->parent, stream->parent_start_offset +
		      stream->istream.v_offset);

	ret = i_stream_read_copy_from_parent(&stream->istream);
	size = i_stream_get_data_size(&stream->istream);
	if (ret > 0) {
		mstream->mail->transaction->stats.files_read_bytes += ret;
		if (!mstream->files_read_increased) {
			mstream->files_read_increased = TRUE;
			mstream->mail->transaction->stats.files_read_count++;
		}
		if (mstream->expected_size < stream->istream.v_offset + size) {
			i_stream_mail_set_size_corrupted(mstream, size);
			return -1;
		}
	} else if (ret == -1 && stream->istream.eof) {
		if (!mstream->input_has_body) {
			/* trying to read past the header, but this stream
			   doesn't have the body */
			return -1;
		}
		if (stream->istream.stream_errno != 0) {
			if (stream->istream.stream_errno == ENOENT) {
				/* update mail's expunged-flag if needed */
				index_mail_refresh_expunged(mstream->mail);
			}
			return -1;
		}
		if (i_stream_mail_try_get_cached_size(mstream) &&
		    mstream->expected_size > stream->istream.v_offset + size) {
			i_stream_mail_set_size_corrupted(mstream, size);
			return -1;
		}
	}
	return ret;
}

struct istream *i_stream_create_mail(struct mail *mail, struct istream *input,
				     bool input_has_body)
{
	struct mail_istream *mstream;

	mstream = i_new(struct mail_istream, 1);
	mstream->mail = mail;
	mstream->input_has_body = input_has_body;
	mstream->expected_size = (uoff_t)-1;
	(void)i_stream_mail_try_get_cached_size(mstream);
	mstream->istream.max_buffer_size = input->real_stream->max_buffer_size;
	mstream->istream.stream_size_passthrough = TRUE;

	mstream->istream.read = i_stream_mail_read;

	mstream->istream.istream.readable_fd = input->readable_fd;
	mstream->istream.istream.blocking = input->blocking;
	mstream->istream.istream.seekable = input->seekable;
	return i_stream_create(&mstream->istream, input,
			       i_stream_get_fd(input));
}