# -*- coding: utf-8 -*-
# Copyright 2011 The ChromiumOS Authors
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

"""Compute image checksum."""


import os
import threading

from cros_utils import logger
from cros_utils.file_utils import FileUtils


class ImageChecksummer(object):
    """Compute image checksum."""

    class PerImageChecksummer(object):
        """Compute checksum for an image."""

        def __init__(self, label, log_level):
            self._lock = threading.Lock()
            self.label = label
            self._checksum = None
            self.log_level = log_level

        def Checksum(self):
            with self._lock:
                if not self._checksum:
                    logger.GetLogger().LogOutput(
                        "Acquiring checksum for '%s'." % self.label.name
                    )
                    self._checksum = None
                    if self.label.image_type != "local":
                        raise RuntimeError(
                            "Called Checksum on non-local image!"
                        )
                    if self.label.chromeos_image:
                        if os.path.exists(self.label.chromeos_image):
                            self._checksum = FileUtils().Md5File(
                                self.label.chromeos_image,
                                log_level=self.log_level,
                            )
                            logger.GetLogger().LogOutput(
                                "Computed checksum is " ": %s" % self._checksum
                            )
                    if not self._checksum:
                        raise RuntimeError("Checksum computing error.")
                    logger.GetLogger().LogOutput(
                        "Checksum is: %s" % self._checksum
                    )
                return self._checksum

    _instance = None
    _lock = threading.Lock()
    _per_image_checksummers = {}

    def __new__(cls, *args, **kwargs):
        with cls._lock:
            if not cls._instance:
                cls._instance = super(ImageChecksummer, cls).__new__(
                    cls, *args, **kwargs
                )
            return cls._instance

    def Checksum(self, label, log_level):
        if label.image_type != "local":
            raise RuntimeError("Attempt to call Checksum on non-local image.")
        with self._lock:
            if label.name not in self._per_image_checksummers:
                self._per_image_checksummers[
                    label.name
                ] = ImageChecksummer.PerImageChecksummer(label, log_level)
            checksummer = self._per_image_checksummers[label.name]

        try:
            return checksummer.Checksum()
        except:
            logger.GetLogger().LogError(
                "Could not compute checksum of image in label"
                " '%s'." % label.name
            )
            raise