from difflib import HtmlDiff
from django.shortcuts import get_object_or_404, render_to_response, redirect
from django.http import HttpResponseForbidden
from django.views.decorators.http import require_POST
from django.contrib.auth.decorators import login_required, user_passes_test
from django.contrib import messages
from django.template import RequestContext
from django.utils.functional import wraps
from markupwiki.models import Article, PUBLIC, DELETED, LOCKED
from markupwiki.forms import ArticleForm, StaffModerationForm

def title_check(view):
    def new_view(request, title, *args, **kwargs):
        newtitle = title.replace(' ', '_')
        if newtitle != title:
            return redirect(request.path.replace(title, newtitle))
        else:
            return view(request, title, *args, **kwargs)
    return wraps(view)(new_view)

@title_check
def view_article(request, title, n=None):
    ''' view an article (or a specific revision of an article)

    if n is specified will show nth revision, otherwise latest will be shown

    if the article does not exist the user will be redirected to the edit page

    Context:
        article - ``Article`` instance
        version - ``ArticleVersion`` to display
        form    - ``StaffModerationForm`` instance present if user is staff

    Template:
        article.html - default template used
    '''

    try:
        article = Article.objects.get(title=title)
    except Article.DoesNotExist:
        return redirect('edit_article', title)

    if n:
        version = article.versions.get(number=n)
    else:
        version = article.versions.latest()
        version.is_latest = True

    # set editable flag on article
    article.editable = article.is_editable_by_user(request.user)

    context = {'article':article, 'version': version}

    if request.user.is_staff:
        context['mod_form'] = StaffModerationForm(instance=article)

    return render_to_response('markupwiki/article.html', context,
                              context_instance=RequestContext(request))

@title_check
@login_required
def edit_article(request, title):
    ''' edit (or create) an article

        Context:
            title - title of article being edited
            article - article being edited (potentially None)
            form - form to edit article

        Templates:
            edit_article.html - Default template for editing the article.
            locked_article.html - Template shown if editing is locked.
    '''
    try:
        article = Article.objects.get(title=title)
    except Article.DoesNotExist:
        article = None

    # check for staff lock
    if article and not article.is_editable_by_user(request.user):
        return HttpResponseForbidden('not authorized to edit')

    if request.method == 'GET':
        # either get an empty ArticleForm or one based on latest version
        if article:

            if not article.get_write_lock(request.user):
                # set message and redirect
                messages.info(request, 'Someone else is currently editing this page, please wait and try again.')
                return redirect(article)

            version = article.versions.latest()
            form = ArticleForm(data={'body':version.body,
                               'body_markup_type':version.body_markup_type})
        else:
            form = ArticleForm()
    elif request.method == 'POST':
        form = ArticleForm(request.POST)
        if form.is_valid():
            if not article:
                # if article doesn't exist create it and start num at 0
                article = Article.objects.create(title=title,
                                                 creator=request.user)
                num = 0
            else:
                if not article.get_write_lock(request.user):
                    # set message and redirect
                    messages.error(request, 'Your session timed out and someone else is now editing this page.')
                    return redirect(article)

                # otherwise get latest num
                num = article.versions.latest().number + 1

            # create a new version attached to article specified in name
            version = form.save(False)
            version.article = article
            version.author = request.user
            version.number = num
            version.save()

            article.get_write_lock(request.user, release=True)

            # redirect to view article on save
            return redirect(article)

    return render_to_response('markupwiki/edit_article.html',
                              {'title':title, 'article':article, 'form': form},
                              context_instance=RequestContext(request))


@require_POST
@user_passes_test(lambda u: u.is_staff)
@title_check
def article_status(request, title):
    ''' POST-only view to update article status (staff-only)
    '''
    article = get_object_or_404(Article, title=title)
    article.status = int(request.POST['status'])
    article.save()

    return redirect(article)

@require_POST
@user_passes_test(lambda u: u.is_staff)
@title_check
def revert(request, title):
    ''' POST-only view to revert article to a specific revision
    '''
    article = get_object_or_404(Article, title=title)
    revision_id = int(request.POST['revision'])
    revision = get_object_or_404(revision, number=revision_id)
    ArticleVersion.objects.create(article=article, author=request.user,
                                  number=article.versions.latest().number,
                                  body=revision.body)

    return redirect(article)

@title_check
def article_history(request, title):
    article = get_object_or_404(Article, title=title)
    versions = article.versions.filter(removed=False)
    return render_to_response('markupwiki/history.html',
                              {'article':article, 'versions':versions},
                              context_instance=RequestContext(request))

@title_check
def article_diff(request, title):
    article = get_object_or_404(Article, title=title)
    from_id = int(request.GET['from'])
    to_id = int(request.GET['to'])
    from_version = article.versions.get(number=from_id)
    to_version = article.versions.get(number=to_id)
    differ = HtmlDiff()
    from_body = from_version.body.raw.split('\n')
    to_body = to_version.body.raw.split('\n')
    table = differ.make_table(from_body, to_body)
    return render_to_response('article_diff.html',
                              {'article': article, 'table':table,
                               'from': from_id, 'to':to_id},
                              context_instance=RequestContext(request))