from flask import Blueprint, jsonify
from app.auth import login_required
from app.db import query

bp = Blueprint("api", __name__, url_prefix="/api")


@bp.route("/chart-data/<int:user_id>")
@login_required
def chart_data(user_id):
    """Return weight & BMI over time for Chart.js."""
    checkins = query(
        """SELECT weight_kg, bmi, checked_in_at
           FROM checkins WHERE user_id = %s
           ORDER BY checked_in_at ASC""",
        (user_id,),
    )

    labels = [c["checked_in_at"].strftime("%d %b") for c in checkins]
    weights = [float(c["weight_kg"]) for c in checkins]
    bmis = [float(c["bmi"]) if c["bmi"] else None for c in checkins]

    return jsonify({
        "labels": labels,
        "weights": weights,
        "bmis": bmis,
    })


@bp.route("/comparison")
@login_required
def comparison():
    """Return all-user comparison data for bar charts."""
    users = query("""
        SELECT
            u.id,
            u.display_name,
            u.username,
            u.starting_weight_kg,
            (SELECT weight_kg FROM checkins WHERE user_id = u.id ORDER BY checked_in_at ASC LIMIT 1) as first_weight,
            (SELECT weight_kg FROM checkins WHERE user_id = u.id ORDER BY checked_in_at DESC LIMIT 1) as current_weight
        FROM users u
        WHERE (SELECT COUNT(*) FROM checkins WHERE user_id = u.id) > 0
        ORDER BY u.display_name
    """)

    names = []
    pct_lost = []
    kg_lost = []

    for u in users:
        start_w = float(u["starting_weight_kg"] or u["first_weight"] or 0)
        current_w = float(u["current_weight"] or start_w)
        if start_w > 0:
            lost = start_w - current_w
            pct = round((lost / start_w) * 100, 1)
        else:
            lost = 0
            pct = 0
        names.append(u["display_name"] or u["username"])
        pct_lost.append(pct)
        kg_lost.append(round(lost, 1))

    return jsonify({
        "names": names,
        "pct_lost": pct_lost,
        "kg_lost": kg_lost,
    })


@bp.route("/weekly-change/<int:user_id>")
@login_required
def weekly_change(user_id):
    """Return weekly weight changes for bar chart."""
    checkins = query(
        """SELECT weight_kg, checked_in_at
           FROM checkins WHERE user_id = %s
           ORDER BY checked_in_at ASC""",
        (user_id,),
    )

    if len(checkins) < 2:
        return jsonify({"labels": [], "changes": []})

    labels = []
    changes = []
    for i in range(1, len(checkins)):
        prev_w = float(checkins[i - 1]["weight_kg"])
        curr_w = float(checkins[i]["weight_kg"])
        change = round(curr_w - prev_w, 1)
        label = checkins[i]["checked_in_at"].strftime("%d %b")
        labels.append(label)
        changes.append(change)

    return jsonify({"labels": labels, "changes": changes})