"""
Task views for KeepItGoing.
"""

import logging
from django.contrib.auth.decorators import login_required
from django.db.models import Q
from django.shortcuts import render, redirect, get_object_or_404
from django.utils import timezone
from django.utils.http import url_has_allowed_host_and_scheme
from django.views import View
from django.views.decorators.http import require_POST
from rest_framework import generics, permissions, status, filters
from rest_framework.decorators import api_view, permission_classes
from rest_framework.response import Response
from django_filters.rest_framework import DjangoFilterBackend

from .models import Task, Tag, TimeEntry, TaskShare
from .serializers import (
    TaskSerializer,
    TaskListSerializer,
    TagSerializer,
    TimeEntrySerializer,
    TaskShareSerializer,
)
from .permissions import IsOwnerOrReadOnlyIfShared

logger = logging.getLogger(__name__)


def safe_redirect(request, next_url, fallback='dashboard'):
    """
    Safely redirect to next_url after validating it's not an open redirect.

    Only allows relative URLs or URLs to the same host.
    """
    if next_url and url_has_allowed_host_and_scheme(
        url=next_url,
        allowed_hosts={request.get_host()},
        require_https=request.is_secure()
    ):
        return redirect(next_url)
    return redirect(fallback)


# =============================================================================
# API Views
# =============================================================================

class TaskListCreateAPIView(generics.ListCreateAPIView):
    """API endpoint for listing and creating tasks."""

    permission_classes = [permissions.IsAuthenticated]
    filter_backends = [DjangoFilterBackend, filters.SearchFilter, filters.OrderingFilter]
    filterset_fields = ['status', 'priority', 'parent']
    search_fields = ['title', 'description']
    ordering_fields = ['due_date', 'priority', 'created_at', 'sort_order']

    def get_serializer_class(self):
        if self.request.method == 'GET':
            return TaskListSerializer
        return TaskSerializer

    def get_queryset(self):
        user = self.request.user
        # Include own tasks and shared tasks
        own_tasks = Task.objects.filter(user=user)
        shared_task_ids = TaskShare.objects.filter(
            shared_with=user, task__isnull=False
        ).values_list('task_id', flat=True)
        shared_tag_ids = TaskShare.objects.filter(
            shared_with=user, tag__isnull=False
        ).values_list('tag_id', flat=True)

        return Task.objects.filter(
            Q(id__in=own_tasks) |
            Q(id__in=shared_task_ids) |
            Q(tags__id__in=shared_tag_ids)
        ).prefetch_related('tags').distinct()


class TaskDetailAPIView(generics.RetrieveUpdateDestroyAPIView):
    """API endpoint for task details."""

    serializer_class = TaskSerializer
    permission_classes = [permissions.IsAuthenticated, IsOwnerOrReadOnlyIfShared]

    def get_queryset(self):
        user = self.request.user
        return Task.objects.filter(
            Q(user=user) |
            Q(shares__shared_with=user) |
            Q(tags__shares__shared_with=user)
        ).distinct()


class TagListCreateAPIView(generics.ListCreateAPIView):
    """API endpoint for listing and creating tags."""

    serializer_class = TagSerializer
    permission_classes = [permissions.IsAuthenticated]

    def get_queryset(self):
        user = self.request.user
        return Tag.objects.filter(
            Q(user=user) | Q(shares__shared_with=user)
        ).distinct()


class TagDetailAPIView(generics.RetrieveUpdateDestroyAPIView):
    """API endpoint for tag details."""

    serializer_class = TagSerializer
    permission_classes = [permissions.IsAuthenticated, IsOwnerOrReadOnlyIfShared]

    def get_queryset(self):
        user = self.request.user
        return Tag.objects.filter(
            Q(user=user) | Q(shares__shared_with=user)
        ).distinct()


class TimeEntryListCreateAPIView(generics.ListCreateAPIView):
    """API endpoint for time entries."""

    serializer_class = TimeEntrySerializer
    permission_classes = [permissions.IsAuthenticated]
    filterset_fields = ['task']

    def get_queryset(self):
        return TimeEntry.objects.filter(user=self.request.user)


class TimeEntryDetailAPIView(generics.RetrieveUpdateDestroyAPIView):
    """API endpoint for time entry details."""

    serializer_class = TimeEntrySerializer
    permission_classes = [permissions.IsAuthenticated]

    def get_queryset(self):
        return TimeEntry.objects.filter(user=self.request.user)


@api_view(['POST'])
@permission_classes([permissions.IsAuthenticated])
def start_timer(request, task_id):
    """Start a timer for a task."""
    task = get_object_or_404(Task, id=task_id, user=request.user)

    # Check for existing running timer
    running = TimeEntry.objects.filter(
        user=request.user,
        ended_at__isnull=True
    ).first()

    if running:
        return Response(
            {'error': 'You already have a running timer. Stop it first.'},
            status=status.HTTP_400_BAD_REQUEST
        )

    entry = TimeEntry.objects.create(
        task=task,
        user=request.user,
        started_at=timezone.now()
    )

    return Response(TimeEntrySerializer(entry).data, status=status.HTTP_201_CREATED)


@api_view(['POST'])
@permission_classes([permissions.IsAuthenticated])
def stop_timer(request, entry_id):
    """Stop a running timer."""
    entry = get_object_or_404(
        TimeEntry,
        id=entry_id,
        user=request.user,
        ended_at__isnull=True
    )

    entry.ended_at = timezone.now()
    entry.save()

    return Response(TimeEntrySerializer(entry).data)


class TaskShareListCreateAPIView(generics.ListCreateAPIView):
    """API endpoint for sharing tasks."""

    serializer_class = TaskShareSerializer
    permission_classes = [permissions.IsAuthenticated]

    def get_queryset(self):
        return TaskShare.objects.filter(
            Q(owner=self.request.user) | Q(shared_with=self.request.user)
        )


class TaskShareDeleteAPIView(generics.DestroyAPIView):
    """API endpoint for removing a share."""

    serializer_class = TaskShareSerializer
    permission_classes = [permissions.IsAuthenticated]

    def get_queryset(self):
        return TaskShare.objects.filter(owner=self.request.user)


# =============================================================================
# Web Views (Django Templates)
# =============================================================================

class DashboardView(View):
    """Main dashboard view with 3-pane layout."""

    def get(self, request):
        if not request.user.is_authenticated:
            return redirect('login')

        today = timezone.now().date()

        # Get filter parameters
        current_filter = request.GET.get('filter', 'all')
        current_tag_id = request.GET.get('tag')
        selected_task_id = request.GET.get('selected')
        current_sort = request.GET.get('sort', 'default')

        # Base query
        tasks = Task.objects.filter(
            user=request.user,
            parent__isnull=True,
        ).prefetch_related('tags', 'subtasks')

        # Apply status filter (exclude completed by default unless showing all)
        if current_filter != 'completed':
            tasks = tasks.exclude(status='completed')

        # Apply filters (can combine tag + date filter)
        page_title_parts = []

        # Apply date/status filter first
        if current_filter == 'today':
            tasks = tasks.filter(due_date=today)
            page_title_parts.append("Today")
        elif current_filter == 'upcoming':
            tasks = tasks.filter(due_date__gt=today)
            page_title_parts.append("Upcoming")
        elif current_filter == 'overdue':
            tasks = [t for t in tasks if t.is_overdue]
            page_title_parts.append("Overdue")
        elif current_filter == 'completed':
            tasks = tasks.filter(status='completed')
            page_title_parts.append("Completed")
        else:
            page_title_parts.append("All Tasks")

        # Apply tag filter
        if current_tag_id:
            # Filter for tasks with specific tag
            if isinstance(tasks, list):
                tasks = [t for t in tasks if t.tags.filter(id=current_tag_id).exists()]
            else:
                tasks = tasks.filter(tags__id=current_tag_id)
            tag = Tag.objects.filter(id=current_tag_id, user=request.user).first()
            if tag:
                page_title_parts.append(tag.name)

        # Build page title
        page_title = " • ".join(page_title_parts) if len(page_title_parts) > 1 else page_title_parts[0]

        # Apply sorting before converting to list
        if not isinstance(tasks, list):
            if current_sort == 'due_date':
                # Sort by due date (nulls last), then priority
                from django.db.models import F
                tasks = tasks.order_by(F('due_date').asc(nulls_last=True), '-priority')
            elif current_sort == 'due_date_desc':
                # Sort by due date descending (nulls last), then priority
                from django.db.models import F
                tasks = tasks.order_by(F('due_date').desc(nulls_last=True), '-priority')
            elif current_sort == 'priority':
                # Sort by priority, then due date
                tasks = tasks.order_by('-priority', 'due_date')
            elif current_sort == 'priority_low':
                # Sort by priority (low to high), then due date
                tasks = tasks.order_by('priority', 'due_date')
            # else: default ordering from model (sort_order, -priority, due_date, created_at)

        # Convert to list if not already (for overdue filter)
        if not isinstance(tasks, list):
            tasks = list(tasks)

        # Apply sorting to lists (for overdue filter case)
        else:
            priority_order = {'high': 3, 'medium': 2, 'low': 1}
            if current_sort == 'due_date':
                tasks = sorted(tasks, key=lambda t: (t.due_date or timezone.now().date() + timezone.timedelta(days=9999), -priority_order.get(t.priority, 0)))
            elif current_sort == 'due_date_desc':
                tasks = sorted(tasks, key=lambda t: (t.due_date or timezone.now().date() - timezone.timedelta(days=9999), -priority_order.get(t.priority, 0)), reverse=True)
            elif current_sort == 'priority':
                tasks = sorted(tasks, key=lambda t: (-priority_order.get(t.priority, 0), t.due_date or timezone.now().date() + timezone.timedelta(days=9999)))
            elif current_sort == 'priority_low':
                tasks = sorted(tasks, key=lambda t: (priority_order.get(t.priority, 0), t.due_date or timezone.now().date() + timezone.timedelta(days=9999)))

        # Get all tags for sidebar with task counts
        from django.db.models import Count, Q
        tags = Tag.objects.filter(
            user=request.user,
            is_archived=False
        ).annotate(
            task_count=Count(
                'tasks',
                filter=Q(tasks__parent__isnull=True) & ~Q(tasks__status='completed'),
                distinct=True
            )
        )

        # Task counts for sidebar
        all_tasks = Task.objects.filter(
            user=request.user,
            parent__isnull=True
        ).exclude(status='completed')

        completed_tasks = Task.objects.filter(
            user=request.user,
            parent__isnull=True,
            status='completed'
        )

        task_counts = {
            'all': all_tasks.count(),
            'today': all_tasks.filter(due_date=today).count(),
            'upcoming': all_tasks.filter(due_date__gt=today).count(),
            'overdue': sum(1 for t in all_tasks if t.is_overdue),
            'completed': completed_tasks.count(),
        }

        # Check for running timer
        running_timer = TimeEntry.objects.filter(
            user=request.user,
            ended_at__isnull=True
        ).select_related('task').first()

        # Selected task for detail panel
        selected_task = None
        if selected_task_id:
            selected_task = Task.objects.filter(
                id=selected_task_id,
                user=request.user
            ).prefetch_related('tags').first()

        return render(request, 'tasks/dashboard.html', {
            'tasks': tasks,
            'page_title': page_title,
            'tags': tags,
            'task_counts': task_counts,
            'current_filter': current_filter,
            'current_tag_id': current_tag_id,
            'current_sort': current_sort,
            'selected_task_id': selected_task_id,
            'selected_task': selected_task,
            'running_timer': running_timer,
        })


class TaskListView(View):
    """Task list view with filtering."""

    def get(self, request):
        if not request.user.is_authenticated:
            return redirect('login')

        tasks = Task.objects.filter(
            user=request.user,
            parent__isnull=True
        ).prefetch_related('tags', 'subtasks')

        # Apply filters
        status_filter = request.GET.get('status')
        tag_filter = request.GET.get('tag')
        priority_filter = request.GET.get('priority')

        if status_filter:
            tasks = tasks.filter(status=status_filter)
        if tag_filter:
            tasks = tasks.filter(tags__id=tag_filter)
        if priority_filter:
            tasks = tasks.filter(priority=priority_filter)

        tags = Tag.objects.filter(user=request.user, is_archived=False)

        return render(request, 'tasks/task_list.html', {
            'tasks': tasks,
            'tags': tags,
            'current_status': status_filter,
            'current_tag': tag_filter,
            'current_priority': priority_filter,
        })


class TaskDetailView(View):
    """Task detail view."""

    def get(self, request, task_id):
        if not request.user.is_authenticated:
            return redirect('login')

        task = get_object_or_404(Task, id=task_id, user=request.user)
        time_entries = task.time_entries.all()[:10]
        tags = Tag.objects.filter(user=request.user)

        return render(request, 'tasks/task_detail.html', {
            'task': task,
            'time_entries': time_entries,
            'tags': tags,
        })

    def post(self, request, task_id):
        if not request.user.is_authenticated:
            return redirect('login')

        task = get_object_or_404(Task, id=task_id, user=request.user)

        task.title = request.POST.get('title', task.title)
        task.description = request.POST.get('description', '')
        task.status = request.POST.get('status', task.status)
        task.priority = request.POST.get('priority', task.priority)

        due_date = request.POST.get('due_date')
        task.due_date = due_date if due_date else None

        due_time = request.POST.get('due_time')
        task.due_time = due_time if due_time else None

        task.recurrence = request.POST.get('recurrence', 'none')

        task.save()

        # Handle tags
        tag_ids = request.POST.getlist('tags')
        task.tags.set(tag_ids)

        # Redirect to next URL if provided, otherwise back to task detail
        next_url = request.POST.get('next')
        if next_url:
            return safe_redirect(request, next_url, fallback=f'/task/{task.id}/')

        return redirect('task-detail', task_id=task.id)


class TaskCreateView(View):
    """Create new task."""

    def get(self, request):
        if not request.user.is_authenticated:
            return redirect('login')

        tags = Tag.objects.filter(user=request.user, is_archived=False)

        return render(request, 'tasks/task_create.html', {
            'tags': tags,
        })

    def post(self, request):
        if not request.user.is_authenticated:
            return redirect('login')

        task = Task.objects.create(
            user=request.user,
            title=request.POST.get('title'),
            description=request.POST.get('description', ''),
            status=request.POST.get('status', 'pending'),
            priority=request.POST.get('priority', 'medium'),
            due_date=request.POST.get('due_date') or None,
            due_time=request.POST.get('due_time') or None,
            recurrence=request.POST.get('recurrence', 'none'),
        )

        tag_ids = request.POST.getlist('tags')
        task.tags.set(tag_ids)

        return redirect('task-detail', task_id=task.id)


@login_required
@require_POST
def task_quick_add(request):
    """Quick add task from dashboard."""
    task = Task.objects.create(
        user=request.user,
        title=request.POST.get('title'),
        due_date=request.POST.get('due_date') or None,
    )
    # Handle optional tag
    tag_id = request.POST.get('tag')
    if tag_id:
        task.tags.add(tag_id)

    next_url = request.POST.get('next', 'dashboard')
    return safe_redirect(request, next_url, fallback='dashboard')


@login_required
@require_POST
def subtask_create(request, task_id):
    """Create a subtask for a task."""
    parent_task = get_object_or_404(Task, id=task_id, user=request.user)

    title = request.POST.get('title', '').strip()
    if title:
        subtask = Task.objects.create(
            user=request.user,
            title=title,
            parent=parent_task,
        )
        # Inherit tags from parent
        subtask.tags.set(parent_task.tags.all())

    next_url = request.POST.get('next', request.META.get('HTTP_REFERER', 'dashboard'))
    return safe_redirect(request, next_url, fallback='dashboard')


@login_required
@require_POST
def task_toggle_status(request, task_id):
    """Toggle task completion status."""
    task = get_object_or_404(Task, id=task_id, user=request.user)

    if task.status == 'completed':
        task.status = 'pending'
    else:
        task.status = 'completed'
    task.save()

    next_url = request.POST.get('next', 'dashboard')
    return safe_redirect(request, next_url, fallback='dashboard')


@login_required
@require_POST
def task_delete(request, task_id):
    """Delete a task (soft delete)."""
    task = get_object_or_404(Task, id=task_id, user=request.user)
    task.is_deleted = True
    task.save()

    next_url = request.POST.get('next', 'dashboard')
    return safe_redirect(request, next_url, fallback='dashboard')


@login_required
def task_detail_partial(request, task_id):
    """Return task detail HTML partial for AJAX requests."""
    task = get_object_or_404(Task, id=task_id, user=request.user)
    tags = Tag.objects.filter(user=request.user, is_archived=False)

    # Check for running timer
    running_timer = TimeEntry.objects.filter(
        user=request.user,
        ended_at__isnull=True
    ).select_related('task').first()

    return render(request, 'tasks/_task_detail.html', {
        'task': task,
        'tags': tags,
        'running_timer': running_timer,
    })


@login_required
@require_POST
def web_timer_start(request, task_id):
    """Start a timer for a task (web view)."""
    task = get_object_or_404(Task, id=task_id, user=request.user)
    logger.debug(f"Starting timer for task: {task.title} (id: {task_id})")

    # Stop any existing running timer first (properly to calculate duration)
    running_entries = TimeEntry.objects.filter(
        user=request.user,
        ended_at__isnull=True
    )

    stopped_count = 0
    for entry in running_entries:
        entry.ended_at = timezone.now()
        entry.save()  # This will calculate duration_seconds
        stopped_count += 1

    logger.debug(f"Stopped {stopped_count} existing timers")

    # Create new timer
    entry = TimeEntry.objects.create(
        task=task,
        user=request.user,
        started_at=timezone.now()
    )
    logger.debug(f"Created new timer entry: {entry.id}")

    next_url = request.POST.get('next', 'dashboard')
    return safe_redirect(request, next_url, fallback='dashboard')


@login_required
@require_POST
def web_timer_stop(request, task_id):
    """Stop a timer for a task (web view)."""
    logger.debug(f"Stopping timer for task_id: {task_id}")

    # Get the running timer and stop it properly (to trigger save() and calculate duration)
    entries = TimeEntry.objects.filter(
        user=request.user,
        task_id=task_id,
        ended_at__isnull=True
    )

    stopped_count = 0
    for entry in entries:
        entry.ended_at = timezone.now()
        entry.save()  # This will calculate duration_seconds
        stopped_count += 1

    logger.debug(f"Stopped {stopped_count} timer entries")

    next_url = request.POST.get('next', 'dashboard')
    return safe_redirect(request, next_url, fallback='dashboard')


class TagListView(View):
    """List tags."""

    def get(self, request):
        if not request.user.is_authenticated:
            return redirect('login')

        tags = Tag.objects.filter(user=request.user)
        return render(request, 'tasks/tag_list.html', {'tags': tags})

    def post(self, request):
        if not request.user.is_authenticated:
            return redirect('login')

        Tag.objects.create(
            user=request.user,
            name=request.POST.get('name'),
            color=request.POST.get('color', '#3B82F6'),
        )
        return redirect('tag-list')


class TagDetailView(View):
    """Edit a tag."""

    def get(self, request, tag_id):
        if not request.user.is_authenticated:
            return redirect('login')

        tag = get_object_or_404(Tag, id=tag_id, user=request.user)
        return render(request, 'tasks/tag_edit.html', {'tag': tag})

    def post(self, request, tag_id):
        if not request.user.is_authenticated:
            return redirect('login')

        tag = get_object_or_404(Tag, id=tag_id, user=request.user)
        tag.name = request.POST.get('name', tag.name)
        tag.color = request.POST.get('color', tag.color)
        tag.description = request.POST.get('description', tag.description)
        tag.save()

        next_url = request.POST.get('next', 'tag-list')
        return safe_redirect(request, next_url, fallback='tag-list')


@login_required
@require_POST
def tag_delete(request, tag_id):
    """Delete a tag (soft delete)."""
    tag = get_object_or_404(Tag, id=tag_id, user=request.user)
    tag.is_deleted = True
    tag.save()

    next_url = request.POST.get('next', 'tag-list')
    return safe_redirect(request, next_url, fallback='tag-list')