from datetime import timezone
from flask import Blueprint, render_template
from app.auth import login_required, get_current_user
from app.db import query, query_one
from app.config import SYDNEY_TZ
from app.utils import calculate_streak, calculate_weight_change

bp = Blueprint("dashboard", __name__)


@bp.route("/")
@login_required
def index():
    user = get_current_user()
    uid = user["id"]

    # --- Single query: latest, first, count via window functions ----------
    summary = query_one("""
        SELECT
            total,
            first_weight,
            latest_weight,
            latest_bmi,
            latest_at
        FROM (
            SELECT
                COUNT(*) OVER ()                                                   AS total,
                FIRST_VALUE(weight_kg) OVER (ORDER BY checked_in_at ASC)           AS first_weight,
                FIRST_VALUE(weight_kg) OVER (ORDER BY checked_in_at DESC)          AS latest_weight,
                FIRST_VALUE(bmi)       OVER (ORDER BY checked_in_at DESC)          AS latest_bmi,
                FIRST_VALUE(checked_in_at) OVER (ORDER BY checked_in_at DESC)     AS latest_at,
                ROW_NUMBER()           OVER (ORDER BY checked_in_at DESC)          AS rn
            FROM checkins
            WHERE user_id = %s
        ) sub
        WHERE rn = 1
    """, (uid,))

    # Build lightweight "latest" dict for the template
    latest = None
    weight_change = None
    weight_change_pct = None
    total_checkins = 0

    if summary:
        total_checkins = summary["total"]
        latest = {
            "weight_kg": summary["latest_weight"],
            "bmi": summary["latest_bmi"],
            "checked_in_at": summary["latest_at"],
        }
        kg_lost, pct_lost = calculate_weight_change(
            summary["first_weight"], summary["latest_weight"]
        )
        weight_change = round(-kg_lost, 1)
        weight_change_pct = round(-pct_lost, 1)

    # Recent check-ins (last 5)
    recent_checkins = query(
        "SELECT * FROM checkins WHERE user_id = %s ORDER BY checked_in_at DESC LIMIT 5",
        (uid,),
    )

    # Activity feed (recent check-ins from all users)
    activity = query("""
        SELECT c.*, u.display_name, u.username
        FROM checkins c
        JOIN users u ON c.user_id = u.id
        WHERE u.is_private = FALSE OR u.id = %s
        ORDER BY c.checked_in_at DESC
        LIMIT 10
    """, (uid,))

    # Milestones
    milestones = query(
        "SELECT * FROM milestones WHERE user_id = %s ORDER BY achieved_at DESC",
        (uid,),
    )

    # Streak
    streak = calculate_streak(uid)

    # --- Pre-compute chart data (eliminates 2 client-side fetches) --------
    chart_checkins = query(
        """SELECT weight_kg, bmi, checked_in_at
           FROM checkins WHERE user_id = %s
           ORDER BY checked_in_at ASC""",
        (uid,),
    )

    chart_labels = []
    chart_weights = []
    weekly_labels = []
    weekly_changes = []

    for i, c in enumerate(chart_checkins):
        dt = c["checked_in_at"]
        if dt.tzinfo is None:
            dt = dt.replace(tzinfo=timezone.utc)
        label = dt.astimezone(SYDNEY_TZ).strftime("%d %b")
        chart_labels.append(label)
        chart_weights.append(float(c["weight_kg"]))

        if i > 0:
            prev_w = float(chart_checkins[i - 1]["weight_kg"])
            curr_w = float(c["weight_kg"])
            weekly_labels.append(label)
            weekly_changes.append(round(curr_w - prev_w, 1))

    return render_template(
        "dashboard.html",
        user=user,
        latest=latest,
        stats={"total_checkins": total_checkins},
        weight_change=weight_change,
        weight_change_pct=weight_change_pct,
        recent_checkins=recent_checkins,
        activity=activity,
        milestones=milestones,
        streak=streak,
        chart_labels=chart_labels,
        chart_weights=chart_weights,
        weekly_labels=weekly_labels,
        weekly_changes=weekly_changes,
    )