from __future__ import with_statement  # for python 2.5
from django.conf import settings
from django.core.urlresolvers import reverse

from djangorestframework.resource import Resource
from djangorestframework.response import Response, status
from djangorestframework.emitters import BaseEmitter

from pygments.formatters import HtmlFormatter
from pygments.lexers import get_lexer_by_name
from pygments import highlight

from forms import PygmentsForm

import os
import uuid
import operator

# We need somewhere to store the code that we highlight
HIGHLIGHTED_CODE_DIR = os.path.join(settings.MEDIA_ROOT, 'pygments')
MAX_FILES = 20

def remove_oldest_files(dir, max_files):
    """Remove the oldest files in a directory 'dir', leaving at most 'max_files' remaining.
    We use this to limit the number of resources in the sandbox."""
    filepaths = [os.path.join(dir, file) for file in os.listdir(dir)]
    ctime_sorted_paths = [item[0] for item in sorted([(path, os.path.getctime(path)) for path in filepaths],
                                                     key=operator.itemgetter(1), reverse=True)]
    [os.remove(path) for path in ctime_sorted_paths[max_files:]]


class HTMLEmitter(BaseEmitter):
    """Basic emitter which just returns the content without any further serialization."""
    media_type = 'text/html'


class PygmentsRoot(Resource):
    """This example demonstrates a simple RESTful Web API aound the awesome pygments library.
    This top level resource is used to create highlighted code snippets, and to list all the existing code snippets."""
    form = PygmentsForm
    allowed_methods = anon_allowed_methods = ('GET', 'POST',)

    def get(self, request, auth):
        """Return a list of all currently existing snippets."""
        unique_ids = sorted(os.listdir(HIGHLIGHTED_CODE_DIR))
        return [reverse('pygments-instance', args=[unique_id]) for unique_id in unique_ids]

    def post(self, request, auth, content):
        """Create a new highlighed snippet and return it's location.
        For the purposes of the sandbox example, also ensure we delete the oldest snippets if we have > MAX_FILES."""
        unique_id = str(uuid.uuid1())
        pathname = os.path.join(HIGHLIGHTED_CODE_DIR, unique_id)

        lexer = get_lexer_by_name(content['lexer'])
        linenos = 'table' if content['linenos'] else False
        options = {'title': content['title']} if content['title'] else {}
        formatter = HtmlFormatter(style=content['style'], linenos=linenos, full=True, **options)
        
        with open(pathname, 'w') as outfile:
            highlight(content['code'], lexer, formatter, outfile)
        
        remove_oldest_files(HIGHLIGHTED_CODE_DIR, MAX_FILES)

        return Response(status.HTTP_201_CREATED, headers={'Location': reverse('pygments-instance', args=[unique_id])})


class PygmentsInstance(Resource):
    """Simply return the stored highlighted HTML file with the correct mime type.
    This Resource only emits HTML and uses a standard HTML emitter rather than the emitters.DocumentingHTMLEmitter class."""
    allowed_methods = anon_allowed_methods = ('GET',)
    emitters = (HTMLEmitter,)

    def get(self, request, auth, unique_id):
        """Return the highlighted snippet."""
        pathname = os.path.join(HIGHLIGHTED_CODE_DIR, unique_id)
        if not os.path.exists(pathname):
            return Resource(status.HTTP_404_NOT_FOUND)
        return open(pathname, 'r').read()

    def delete(self, request, auth, unique_id):
        """Delete the highlighted snippet."""
        pathname = os.path.join(HIGHLIGHTED_CODE_DIR, unique_id)
        if not os.path.exists(pathname):
            return Resource(status.HTTP_404_NOT_FOUND)
        return os.remove(pathname)