"""The SQlite blob file-like object."""

import os

from dfvfs.file_io import file_io
from dfvfs.lib import errors
from dfvfs.lib import sqlite_database
from dfvfs.resolver import resolver


class SQLiteBlobFile(file_io.FileIO):
    """File input/output (IO) object using sqlite."""

    _OPERATORS = frozenset(["==", "=", "IS"])

    def __init__(self, resolver_context, path_spec):
        """Initializes the file-like object.

        Args:
          resolver_context (Context): resolver context.
          path_spec (PathSpec): a path specification.
        """
        super().__init__(resolver_context, path_spec)
        self._blob = None
        self._current_offset = 0
        self._database_object = None
        self._number_of_rows = None
        self._size = 0
        self._table_name = None

    def _Close(self):
        """Closes the file-like object."""
        if self._database_object:
            self._database_object.Close()

        self._blob = None
        self._current_offset = 0
        self._size = 0
        self._table_name = None

    def _Open(self):
        """Opens the file-like object defined by path specification.

        Raises:
          AccessError: if the access to open the file was denied.
          OSError: if the file-like object could not be opened.
          PathSpecError: if the path specification is incorrect.
        """
        if not self._path_spec.HasParent():
            raise errors.PathSpecError("Unsupported path specification without parent.")

        table_name = getattr(self._path_spec, "table_name", None)
        if table_name is None:
            raise errors.PathSpecError("Path specification missing table name.")

        column_name = getattr(self._path_spec, "column_name", None)
        if column_name is None:
            raise errors.PathSpecError("Path specification missing column name.")

        row_condition = getattr(self._path_spec, "row_condition", None)
        if row_condition:
            if not isinstance(row_condition, tuple) or len(row_condition) != 3:
                raise errors.PathSpecError(
                    "Unsupported row_condition not a tuple in the form: "
                    "(column_name, operator, value)."
                )

        row_index = getattr(self._path_spec, "row_index", None)
        if row_index is not None and not isinstance(row_index, int):
            raise errors.PathSpecError("Unsupported row_index not of integer type.")

        if not row_condition and row_index is None:
            raise errors.PathSpecError(
                "Path specification requires either a row_condition or row_index."
            )

        if self._database_object:
            raise OSError("Database file already set.")

        file_object = resolver.Resolver.OpenFileObject(
            self._path_spec.parent, resolver_context=self._resolver_context
        )
        database_object = sqlite_database.SQLiteDatabaseFile()
        database_object.Open(file_object)

        # Sanity check the table and column names.
        rows = []
        error_string = ""
        if not database_object.HasTable(table_name):
            error_string = f"Missing table: {table_name:s}"

        elif not database_object.HasColumn(table_name, column_name):
            error_string = f"Missing column: {column_name:s} in table: {table_name:s}"

        elif not row_condition:
            query = (
                f"SELECT {column_name:s} FROM {table_name:s} LIMIT 1 "
                f"OFFSET {row_index:d}"
            )
            rows = database_object.Query(query)

        elif not database_object.HasColumn(table_name, row_condition[0]):
            condition_column_name = row_condition[0]
            error_string = (
                f"Missing row condition column: {condition_column_name:s} in table: "
                f"{table_name:s}"
            )

        elif row_condition[1] not in self._OPERATORS:
            condition_operator = row_condition[1]
            error_string = (
                f"Unsupported row condition operator: {condition_operator:s}."
            )

        else:
            condition_column_name = row_condition[0]
            condition_operator = row_condition[1]
            query = (
                f"SELECT {column_name:s} FROM {table_name:s} "
                f"WHERE {condition_column_name:s} {condition_operator:s} ?"
            )
            rows = database_object.Query(query, parameters=(row_condition[2],))

        # Make sure the query returns a single row, using cursor.rowcount
        # is not reliable for this purpose.
        if not error_string and (len(rows) != 1 or len(rows[0]) != 1):
            if not row_condition:
                error_string = (
                    f"Unable to open blob in table: {table_name:s} and column: "
                    f"{column_name:s} for row: {row_index:d}."
                )

            else:
                row_condition_string = " ".join(
                    [f"{value!s}" for value in iter(row_condition)]
                )
                error_string = (
                    f"Unable to open blob in table: {table_name:s} and column: "
                    f"{column_name:s} where: {row_condition_string:s}."
                )

        if error_string:
            database_object.Close()
            raise OSError(error_string)

        self._blob = rows[0][0]
        self._current_offset = 0
        self._database_object = database_object
        self._size = len(self._blob)
        self._table_name = table_name

    # TODO: remove this when there is a move this to a central temp file
    # manager. https://github.com/log2timeline/dfvfs/issues/92
    def GetNumberOfRows(self):
        """Retrieves the number of rows of the table.

        Returns:
          int: number of rows.

        Raises:
          OSError: if the file-like object has not been opened.
        """
        if not self._database_object:
            raise OSError("Not opened.")

        if self._number_of_rows is None:
            self._number_of_rows = self._database_object.GetNumberOfRows(
                self._table_name
            )

        return self._number_of_rows

    # Note: that the following functions do not follow the style guide
    # because they are part of the file-like object interface.
    # pylint: disable=invalid-name

    def read(self, size=None):
        """Reads a byte string from the file-like object at the current offset.

        The function will read a byte string of the specified size or
        all of the remaining data if no size was specified.

        Args:
          size (Optional[int]): number of bytes to read, where None is all
              remaining data.

        Returns:
          bytes: data read.

        Raises:
          OSError: if the read failed.
        """
        if not self._database_object:
            raise OSError("Not opened.")

        if self._current_offset < 0:
            raise OSError("Invalid offset value out of bounds.")

        if size == 0 or self._current_offset >= self._size:
            return b""

        if size is None:
            size = self._size
        if self._current_offset + size > self._size:
            size = self._size - self._current_offset

        start_offset = self._current_offset
        self._current_offset += size
        return self._blob[start_offset : self._current_offset]

    def seek(self, offset, whence=os.SEEK_SET):
        """Seeks to an offset within the file-like object.

        Args:
          offset (int): offset to seek to.
          whence (Optional(int)): value that indicates whether offset is an absolute
              or relative position within the file.

        Raises:
          OSError: if the seek failed.
        """
        if not self._database_object:
            raise OSError("Not opened.")

        if whence == os.SEEK_CUR:
            offset += self._current_offset
        elif whence == os.SEEK_END:
            offset += self._size
        elif whence != os.SEEK_SET:
            raise OSError("Unsupported whence.")

        if offset < 0:
            raise OSError("Invalid offset value out of bounds.")

        self._current_offset = offset

    def get_offset(self):
        """Retrieves the current offset into the file-like object.

        Returns:
          int: current offset into the file-like object.

        Raises:
          OSError: if the file-like object has not been opened.
        """
        if not self._database_object:
            raise OSError("Not opened.")

        return self._current_offset

    def get_size(self):
        """Retrieves the size of the file-like object.

        Returns:
          int: size of the file-like object data.

        Raises:
          OSError: if the file-like object has not been opened.
        """
        if not self._database_object:
            raise OSError("Not opened.")

        return self._size
