"""Daily Digest and Weekly Retrospective generation."""

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

BERLIN_TZ = ZoneInfo("Europe/Berlin")


def generate_daily_digest(db: Session) -> dict:
    """Generate a structured daily digest.

    Returns a dict with sections: greeting, today_events, top_tasks,
    overdue, due_today, new_since_yesterday, stats.
    """
    now = datetime.now(BERLIN_TZ)
    today_start = datetime.combine(now.date(), datetime.min.time()).replace(tzinfo=BERLIN_TZ)
    today_end = datetime.combine(now.date(), datetime.max.time()).replace(tzinfo=BERLIN_TZ)
    yesterday = today_start - timedelta(days=1)

    # Greeting based on time of day
    hour = now.hour
    if hour < 12:
        greeting = "Good morning"
    elif hour < 17:
        greeting = "Good afternoon"
    else:
        greeting = "Good evening"

    # Today's events
    todays_events = db.query(Event).filter(
        Event.start_time >= today_start,
        Event.start_time <= today_end
    ).order_by(Event.start_time).all()

    # Top 5 priority tasks
    top_tasks = db.query(Task).filter(
        Task.status == "open"
    ).order_by(Task.priority, Task.position).limit(5).all()

    # Overdue tasks
    overdue = db.query(Task).filter(
        Task.status == "open",
        Task.due_date != None,
        Task.due_date < today_start
    ).order_by(Task.due_date).all()

    # Due today
    due_today = db.query(Task).filter(
        Task.status == "open",
        Task.due_date != None,
        Task.due_date >= today_start,
        Task.due_date <= today_end
    ).all()

    # New tasks since yesterday
    new_tasks = db.query(Task).filter(
        Task.status == "open",
        Task.created_at >= yesterday
    ).count()

    # Total open
    total_open = db.query(Task).filter(Task.status == "open").count()

    # Pending calls
    pending_calls = db.query(CallItem).filter(
        CallItem.status == "pending"
    ).all()

    priority_labels = {1: "Very High", 2: "High", 3: "Medium", 4: "Low"}

    result = {
        "greeting": greeting,
        "date": now.strftime("%A, %B %d, %Y"),
        "total_open": total_open,
        "events_today": [
            {
                "title": e.title,
                "time": f"{e.start_time.astimezone(BERLIN_TZ).strftime('%H:%M')} - {e.end_time.astimezone(BERLIN_TZ).strftime('%H:%M')}"
            }
            for e in todays_events
        ],
        "top_tasks": [
            {"id": t.id, "title": t.title, "priority": priority_labels.get(t.priority, "Low")}
            for t in top_tasks
        ],
        "overdue": [
            {
                "id": t.id,
                "title": t.title,
                "days_overdue": (now.date() - t.due_date.date()).days
            }
            for t in overdue
        ],
        "due_today": [
            {"id": t.id, "title": t.title}
            for t in due_today
        ],
        "new_since_yesterday": new_tasks,
        "stats": {
            "events_count": len(todays_events),
            "overdue_count": len(overdue),
            "due_today_count": len(due_today),
        }
    }

    # Only include pending_calls section if there are pending calls
    if pending_calls:
        result["pending_calls"] = [
            {"person": c.person, "reason": c.reason}
            for c in pending_calls
        ]

    return result


def generate_weekly_retro(db: Session) -> dict:
    """Generate a weekly retrospective summary.

    Looks at the past 7 days: what was completed, what slipped,
    what's still open, and workload trends.
    """
    now = datetime.now(BERLIN_TZ)
    week_ago = now - timedelta(days=7)
    today_start = datetime.combine(now.date(), datetime.min.time()).replace(tzinfo=BERLIN_TZ)

    # Tasks completed this week (check for status change isn't tracked,
    # so we look at tasks with status=completed that exist)
    completed_this_week = db.query(Task).filter(
        Task.status == "completed"
    ).count()

    # Tasks still open
    total_open = db.query(Task).filter(Task.status == "open").count()

    # Tasks in review
    in_review = db.query(Task).filter(Task.status == "review").count()

    # Overdue tasks
    overdue = db.query(Task).filter(
        Task.status == "open",
        Task.due_date != None,
        Task.due_date < today_start
    ).order_by(Task.due_date).all()

    # Tasks created this week
    created_this_week = db.query(Task).filter(
        Task.created_at >= week_ago,
        Task.status.notin_(["dismissed"])
    ).count()

    # Tasks by priority
    priority_breakdown = {}
    for prio in [1, 2, 3, 4]:
        count = db.query(Task).filter(
            Task.status == "open", Task.priority == prio
        ).count()
        priority_breakdown[prio] = count

    # Tasks by origin
    origin_breakdown = db.query(
        Task.origin, func.count(Task.id)
    ).filter(Task.status == "open").group_by(Task.origin).all()

    # Events this week
    events_this_week = db.query(Event).filter(
        Event.start_time >= week_ago,
        Event.start_time <= now
    ).count()

    priority_labels = {1: "Very High", 2: "High", 3: "Medium", 4: "Low"}

    return {
        "period": f"{week_ago.strftime('%b %d')} - {now.strftime('%b %d, %Y')}",
        "completed": completed_this_week,
        "created": created_this_week,
        "total_open": total_open,
        "in_review": in_review,
        "overdue": [
            {
                "id": t.id,
                "title": t.title,
                "days_overdue": (now.date() - t.due_date.date()).days
            }
            for t in overdue
        ],
        "priority_breakdown": {
            priority_labels[k]: v for k, v in priority_breakdown.items()
        },
        "origin_breakdown": {
            (origin or "unknown"): count for origin, count in origin_breakdown
        },
        "events_attended": events_this_week,
        "net_change": created_this_week - completed_this_week,
        "health": "growing" if created_this_week > completed_this_week + 5 else
                  "shrinking" if completed_this_week > created_this_week + 3 else "stable",
    }