"""An interface to manage files contained within a pod.

The File class should not be accessed directly. Instead, file objects should be
retrieved using the methods "create_file" or "get_file" from the Pod class.

  pod = pods.Pod('/home/growler/my-site/')

You can create a new file.

  pod.create_file('/README.md')

You can retrieve an existing file.

  pod.get_file('/README.md')

You can delete a file.

  file = pod.get_file('/README.md')
  file.delete()

When using the File class, you must always use the file's "pod path" -- that is, the
file's absolute path within the pod, excluding the pod's root directory.
"""

from grow.common import utils
from grow.pods import messages
import mimetypes
import os

mimetypes.add_type('text/plain', '.md')
mimetypes.add_type('text/plain', '.yaml')
mimetypes.add_type('text/plain', '.yml')

try:
    from google.appengine.ext import blobstore
except ImportError:
    blobstore = None


class Error(Exception):
    pass


class FileExistsError(Error):
    pass


class FileDoesNotExistError(Error):
    pass


class File(object):

    def __init__(self, pod_path, pod):
        utils.validate_name(pod_path)
        self.pod_path = pod_path
        self.pod = pod

    @classmethod
    def create(cls, pod_path, content, pod):
        file_obj = cls(pod_path, pod)
        file_obj.update_content(content)
        return file_obj

    @classmethod
    def get(cls, pod_path, pod):
        file_obj = cls(pod_path, pod)
        file_obj.get_content()
        return file_obj

    @property
    def mimetype(self):
        return mimetypes.guess_type(self.pod_path)[0]

    @classmethod
    def list(cls, pod, prefix='/'):
        paths = sorted(pod.list_dir(prefix))
        return [File(path, pod) for path in paths]

    def delete(self):
        return self.pod.delete_file(self.pod_path)

    def move_to(self, dest_pod_path):
        self.pod.move_file_to(self.pod_path, dest_pod_path)

    def get_content(self):
        try:
            return self.pod.read_file(self.pod_path)
        except IOError as e:
            raise FileDoesNotExistError(e)

    def update_content(self, content):
        if isinstance(content, unicode):
            content = content.encode('utf-8')
        if content is None:
            content = ''
        self.pod.write_file(self.pod_path, content)

    def get_http_headers(self):
        """Returns the HTTP headers used to serve this file."""
        headers = {}
        if self.mimetype:
            headers['Content-Type'] = self.mimetype
        if blobstore and self.pod.storage.is_cloud_storage:
            pod_path = self.pod_path.lstrip('/')
            root = '/' + self.pod.root.lstrip('/')
            path = '/gs' + os.path.join(root, pod_path)
            headers['X-AppEngine-BlobKey'] = blobstore.create_gs_key(path)
        return headers

    def to_message(self):
        message = messages.FileMessage()
        message.pod_path = self.pod_path
        message.mimetype = self.mimetype
        return message