"""Routen des Projekte-Moduls — voller Funktionsumfang aus dem HTML-Prototyp.

Alles ist login_required und strikt auf current_user gescoped. Schreibende
Aktionen laufen als POST + Redirect (PRG-Muster), damit kein Reload doppelt
ausführt.
"""

from datetime import date, datetime, timedelta
from urllib.parse import urlparse

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

from ..extensions import db
from .models import Project, Task
from .helpers import next_color, due_badge, sort_tasks, today_label
from .pdf import build_todo_pdf
from . import bp

VALID_FILTERS = {"all", "open", "overdue", "soon", "done"}


def _redirect_back():
    """Zur vorigen Ansicht zurück (erhält z.B. den Filter), sonst zur Übersicht."""
    ref = request.referrer
    if ref:
        parsed = urlparse(ref)
        if not parsed.netloc or parsed.netloc == urlparse(request.host_url).netloc:
            return redirect(ref)
    return redirect(url_for("projects.index"))


def _owned_project_or_none(project_id):
    """Projekt des aktuellen Users per (string) ID holen — oder None."""
    try:
        pid = int(project_id)
    except (TypeError, ValueError):
        return None
    return Project.query.filter_by(id=pid, user_id=current_user.id).first()


@bp.route("/")
@login_required
def index():
    flt = request.args.get("filter", "all")
    if flt not in VALID_FILTERS:
        flt = "all"

    today = date.today()
    week = today + timedelta(days=7)

    projects = (
        Project.query.filter_by(user_id=current_user.id)
        .order_by(Project.created_at)
        .all()
    )
    tasks = Task.query.filter_by(user_id=current_user.id).all()
    projects_by_id = {p.id: p for p in projects}

    # Statistik-Leiste
    stats = {
        "open": sum(1 for t in tasks if not t.done),
        "done": sum(1 for t in tasks if t.done),
        "overdue": sum(1 for t in tasks if not t.done and t.due_date and t.due_date < today),
        "projects": len(projects),
    }

    # Ansicht "Nach Projekt"
    project_views = []
    for p in projects:
        ptasks = sort_tasks([t for t in tasks if t.project_id == p.id])
        project_views.append(
            {
                "project": p,
                "tasks": ptasks,
                "open": sum(1 for t in ptasks if not t.done),
                "total": len(ptasks),
            }
        )
    proj_open_total = sum(v["open"] for v in project_views)

    # Ansicht "Alle Aufgaben" (gefiltert)
    def keep(t):
        if flt == "open":
            return not t.done
        if flt == "done":
            return t.done
        if flt == "overdue":
            return not t.done and t.due_date and t.due_date < today
        if flt == "soon":
            return not t.done and t.due_date and today <= t.due_date <= week
        return True

    all_tasks = sort_tasks([t for t in tasks if keep(t)])

    return render_template(
        "projects/index.html",
        projects=projects,
        projects_by_id=projects_by_id,
        project_views=project_views,
        proj_open_total=proj_open_total,
        all_tasks=all_tasks,
        stats=stats,
        active_filter=flt,
        today_label=today_label(),
    )


# ── Projekte ─────────────────────────────────────────────────────────────
@bp.route("/projects", methods=["POST"])
@login_required
def create_project():
    name = (request.form.get("name") or "").strip()
    if not name:
        flash("Projektname fehlt.", "error")
        return _redirect_back()

    count = Project.query.filter_by(user_id=current_user.id).count()
    project = Project(user_id=current_user.id, name=name[:120], color=next_color(count))
    db.session.add(project)
    db.session.commit()
    return _redirect_back()


@bp.route("/projects/<int:project_id>/delete", methods=["POST"])
@login_required
def delete_project(project_id):
    project = Project.query.filter_by(id=project_id, user_id=current_user.id).first_or_404()
    # Aufgaben bleiben erhalten, verlieren nur die Projektzuordnung.
    for t in project.tasks:
        t.project_id = None
    db.session.delete(project)
    db.session.commit()
    flash("Projekt gelöscht. Aufgaben bleiben erhalten.", "info")
    return _redirect_back()


# ── Aufgaben ─────────────────────────────────────────────────────────────
@bp.route("/tasks", methods=["POST"])
@login_required
def create_task():
    text = (request.form.get("text") or "").strip()
    if not text:
        flash("Aufgabentext fehlt.", "error")
        return _redirect_back()

    project = _owned_project_or_none(request.form.get("project_id"))
    due_raw = (request.form.get("due_date") or "").strip()
    due = None
    if due_raw:
        try:
            due = datetime.strptime(due_raw, "%Y-%m-%d").date()
        except ValueError:
            due = None

    task = Task(
        user_id=current_user.id,
        text=text[:500],
        project_id=project.id if project else None,
        due_date=due,
    )
    db.session.add(task)
    db.session.commit()
    return _redirect_back()


@bp.route("/tasks/<int:task_id>/toggle", methods=["POST"])
@login_required
def toggle_task(task_id):
    task = Task.query.filter_by(id=task_id, user_id=current_user.id).first_or_404()
    task.done = not task.done
    db.session.commit()
    return _redirect_back()


@bp.route("/tasks/<int:task_id>/delete", methods=["POST"])
@login_required
def delete_task(task_id):
    task = Task.query.filter_by(id=task_id, user_id=current_user.id).first_or_404()
    db.session.delete(task)
    db.session.commit()
    return _redirect_back()


# ── PDF-Export (druckbare To-Do-Liste) ──────────────────────────────────
@bp.route("/export.pdf")
@login_required
def export_pdf():
    projects = (
        Project.query.filter_by(user_id=current_user.id)
        .order_by(Project.created_at)
        .all()
    )
    tasks = Task.query.filter_by(user_id=current_user.id).all()
    pdf_bytes = build_todo_pdf(projects, tasks)

    filename = f"aufgaben_{date.today().isoformat()}.pdf"
    return Response(
        pdf_bytes,
        mimetype="application/pdf",
        headers={"Content-Disposition": f"inline; filename={filename}"},
    )


# Fälligkeits-Badge als Template-Global verfügbar machen.
bp.add_app_template_global(due_badge, "due_badge")