from __future__ import annotations

import calendar
from collections import defaultdict
from datetime import date

from flask import Blueprint, flash, redirect, render_template, request, url_for
from flask_login import current_user, login_required

from ..forms import TaskForm
from ..models import TaskInstance, User
from ..services.dates import month_label, today_local
from ..services.tasks import complete_task, create_task_template_and_instance, refresh_task_statuses, update_template_and_instance


bp = Blueprint("tasks", __name__, url_prefix="")


def _user_choices() -> list[tuple[int, str]]:
    return [(user.id, user.name) for user in User.query.order_by(User.name.asc()).all()]


@bp.route("/my-tasks")
@login_required
def my_tasks():
    tasks = (
        TaskInstance.query.filter_by(assigned_user_id=current_user.id)
        .order_by(TaskInstance.completed_at.is_(None).desc(), TaskInstance.due_date.asc())
        .all()
    )
    refresh_task_statuses(tasks)

    sections = {"open": [], "soon": [], "overdue": [], "completed": []}
    for task in tasks:
        sections[task.status].append(task)

    completed_count = len(sections["completed"])
    active_count = len(sections["open"]) + len(sections["soon"]) + len(sections["overdue"])
    completion_ratio = 0 if completed_count + active_count == 0 else round(completed_count / (completed_count + active_count) * 100)

    return render_template(
        "tasks/my_tasks.html",
        sections=sections,
        completion_ratio=completion_ratio,
        today=today_local(),
    )


@bp.route("/tasks")
@login_required
def all_tasks():
    query = TaskInstance.query
    status = request.args.get("status", "all")
    mine = request.args.get("mine")
    user_filter = request.args.get("user_id", type=int)
    sort = request.args.get("sort", "due")

    if mine == "1":
        query = query.filter(TaskInstance.assigned_user_id == current_user.id)
    elif user_filter:
        query = query.filter(TaskInstance.assigned_user_id == user_filter)

    if sort == "points":
        query = query.order_by(TaskInstance.points_awarded.desc(), TaskInstance.due_date.asc())
    elif sort == "user":
        query = query.order_by(TaskInstance.assigned_user_id.asc(), TaskInstance.due_date.asc())
    else:
        query = query.order_by(TaskInstance.completed_at.is_(None).desc(), TaskInstance.due_date.asc())

    tasks = query.all()
    refresh_task_statuses(tasks)

    if status != "all":
        status_map = {"completed": "completed", "overdue": "overdue", "open": "open", "soon": "soon"}
        selected = status_map.get(status)
        if selected:
            tasks = [task for task in tasks if task.status == selected]

    return render_template(
        "tasks/all_tasks.html",
        tasks=tasks,
        users=User.query.order_by(User.name.asc()).all(),
        filters={"status": status, "mine": mine, "user_id": user_filter, "sort": sort},
    )


@bp.route("/tasks/new", methods=["GET", "POST"])
@login_required
def create():
    form = TaskForm()
    form.assigned_user_id.choices = _user_choices()
    if request.method == "GET" and not form.due_date.data:
        form.due_date.data = today_local()

    if form.validate_on_submit():
        task = create_task_template_and_instance(form)
        flash(f"Aufgabe „{task.title}“ wurde angelegt.", "success")
        return redirect(url_for("tasks.my_tasks"))
    return render_template("tasks/task_form.html", form=form, mode="create", task=None)


@bp.route("/tasks/<int:task_id>/edit", methods=["GET", "POST"])
@login_required
def edit(task_id: int):
    task = TaskInstance.query.get_or_404(task_id)
    form = TaskForm(obj=task.task_template)
    form.assigned_user_id.choices = _user_choices()

    if request.method == "GET":
        form.title.data = task.title
        form.description.data = task.description
        form.default_points.data = task.points_awarded
        form.assigned_user_id.data = task.assigned_user_id or _user_choices()[0][0]
        form.due_date.data = task.due_date
        form.recurrence_interval_value.data = task.task_template.recurrence_interval_value or 1
        form.recurrence_interval_unit.data = task.task_template.recurrence_interval_unit
        form.active.data = task.task_template.active

    if form.validate_on_submit():
        update_template_and_instance(task, form)
        flash("Aufgabe und Vorlage wurden aktualisiert.", "success")
        return redirect(url_for("tasks.all_tasks"))

    return render_template("tasks/task_form.html", form=form, mode="edit", task=task)


@bp.route("/tasks/<int:task_id>/complete", methods=["POST"])
@login_required
def complete(task_id: int):
    task = TaskInstance.query.get_or_404(task_id)
    choice = request.form.get("completed_for", "me")
    if task.is_completed:
        flash("Diese Aufgabe ist bereits erledigt.", "info")
        return redirect(request.referrer or url_for("tasks.my_tasks"))

    completed_by_id = current_user.id
    if task.assigned_user_id and task.assigned_user_id != current_user.id and choice == "assigned":
        completed_by_id = task.assigned_user_id

    complete_task(task, completed_by_id)
    flash("Punkte verbucht. Gute Arbeit.", "success")
    return redirect(request.referrer or url_for("tasks.my_tasks"))


@bp.route("/calendar")
@login_required
def calendar_view():
    today = today_local()
    year = request.args.get("year", type=int) or today.year
    month = request.args.get("month", type=int) or today.month
    view = request.args.get("view", "calendar")

    tasks = TaskInstance.query.filter(
        TaskInstance.due_date >= date(year, month, 1),
        TaskInstance.due_date <= date(year, month, calendar.monthrange(year, month)[1]),
    ).order_by(TaskInstance.due_date.asc()).all()
    refresh_task_statuses(tasks)

    tasks_by_day: dict[int, list[TaskInstance]] = defaultdict(list)
    for task in tasks:
        tasks_by_day[task.due_date.day].append(task)

    month_calendar = calendar.Calendar(firstweekday=0).monthdayscalendar(year, month)
    return render_template(
        "tasks/calendar.html",
        current_year=year,
        current_month=month,
        current_label=month_label(year, month),
        month_calendar=month_calendar,
        tasks_by_day=tasks_by_day,
        view=view,
        tasks=tasks,
    )