"""Prioritization Engine — generates actionable suggestions based on task state."""

from datetime import datetime, timedelta
from zoneinfo import ZoneInfo
from sqlalchemy.orm import Session
from app.models import Task

BERLIN_TZ = ZoneInfo("Europe/Berlin")


def generate_suggestions(db: Session) -> list[dict]:
    """Analyze open tasks and generate prioritization suggestions.

    Returns a list of suggestion dicts with: id, content, type, severity.
    """
    now = datetime.now(BERLIN_TZ)
    today = now.date()
    suggestions = []
    suggestion_id = 1

    open_tasks = db.query(Task).filter(Task.status == "open").all()

    if not open_tasks:
        return []

    # --- 1. Overdue tasks ---
    overdue_tasks = [
        t for t in open_tasks
        if t.due_date and t.due_date.date() < today
    ]
    for t in overdue_tasks[:3]:  # Limit to top 3
        days_overdue = (today - t.due_date.date()).days
        suggestions.append({
            "id": suggestion_id,
            "content": f"⚠️ \"{t.title}\" is {days_overdue} day{'s' if days_overdue != 1 else ''} overdue. Reschedule or complete it.",
            "type": "overdue",
            "severity": "high",
            "task_id": t.id,
        })
        suggestion_id += 1

    # --- 2. Due tomorrow ---
    tomorrow = today + timedelta(days=1)
    due_tomorrow = [
        t for t in open_tasks
        if t.due_date and t.due_date.date() == tomorrow
    ]
    for t in due_tomorrow:
        suggestions.append({
            "id": suggestion_id,
            "content": f"📅 \"{t.title}\" is due tomorrow.",
            "type": "upcoming",
            "severity": "medium",
            "task_id": t.id,
        })
        suggestion_id += 1

    # --- 3. Due this week ---
    week_end = today + timedelta(days=7)
    due_this_week = [
        t for t in open_tasks
        if t.due_date and today < t.due_date.date() <= week_end
        and t.due_date.date() != tomorrow  # Already covered above
    ]
    if len(due_this_week) > 3:
        suggestions.append({
            "id": suggestion_id,
            "content": f"📋 You have {len(due_this_week)} tasks due this week. Plan your time.",
            "type": "workload",
            "severity": "medium",
        })
        suggestion_id += 1

    # --- 4. High-priority tasks without due dates ---
    high_no_date = [
        t for t in open_tasks
        if t.priority and t.priority <= 2 and not t.due_date
    ]
    for t in high_no_date[:2]:  # Limit to top 2
        suggestions.append({
            "id": suggestion_id,
            "content": f"🎯 \"{t.title}\" is high priority but has no deadline. Set a due date.",
            "type": "missing_date",
            "severity": "medium",
            "task_id": t.id,
        })
        suggestion_id += 1

    # --- 5. Tasks idle for 7+ days ---
    idle_threshold = now - timedelta(days=7)
    idle_tasks = [
        t for t in open_tasks
        if t.created_at and t.created_at < idle_threshold
        and (not t.due_date)  # Only flag idle tasks without deadlines
        and t.priority and t.priority >= 3  # Low/medium priority
    ]
    if len(idle_tasks) > 5:
        suggestions.append({
            "id": suggestion_id,
            "content": f"🧹 {len(idle_tasks)} low-priority tasks have been sitting for over a week. Review and clean up.",
            "type": "stale",
            "severity": "low",
        })
        suggestion_id += 1
    elif idle_tasks:
        oldest = max(idle_tasks, key=lambda t: (now - t.created_at).days if t.created_at else 0)
        if oldest.created_at:
            days_idle = (now - oldest.created_at).days
            suggestions.append({
                "id": suggestion_id,
                "content": f"🧹 \"{oldest.title}\" has been open for {days_idle} days. Still relevant?",
                "type": "stale",
                "severity": "low",
                "task_id": oldest.id,
            })
            suggestion_id += 1

    # --- 6. Too many high-priority tasks ---
    high_priority_count = len([t for t in open_tasks if t.priority and t.priority <= 2])
    if high_priority_count > 5:
        suggestions.append({
            "id": suggestion_id,
            "content": f"🔥 You have {high_priority_count} high-priority tasks. If everything is urgent, nothing is. Consider demoting some.",
            "type": "overload",
            "severity": "medium",
        })
        suggestion_id += 1

    # --- 7. No tasks due soon (might need planning) ---
    tasks_with_dates = [t for t in open_tasks if t.due_date]
    if len(open_tasks) > 10 and len(tasks_with_dates) < 3:
        suggestions.append({
            "id": suggestion_id,
            "content": "📆 Most of your tasks have no due dates. Consider scheduling your top priorities.",
            "type": "planning",
            "severity": "low",
        })
        suggestion_id += 1

    return suggestions