"""
Shared business-logic helpers.

Keep route handlers thin — calculation logic lives here.
"""

from app.db import query, execute
from app.config import SYDNEY_TZ
from datetime import datetime, timedelta


# ---------------------------------------------------------------------------
# Milestones — single source of truth for keys, thresholds, and labels
# ---------------------------------------------------------------------------

MILESTONES = [
    # (key, check_fn_or_description, emoji + display label)
    ("first_checkin", "count >= 1", "✅ First Check-in"),
    ("5_checkins",    "count >= 5", "🔥 5 Check-ins"),
    ("10_checkins",   "count >= 10", "💪 10 Check-ins"),
    ("25_checkins",   "count >= 25", "🎯 25 Check-ins"),
    ("lost_1kg",      "lost >= 1",  "⭐ 1kg Lost"),
    ("lost_2kg",      "lost >= 2",  "⭐ 2kg Lost"),
    ("lost_5kg",      "lost >= 5",  "🌟 5kg Lost"),
    ("lost_10kg",     "lost >= 10", "💎 10kg Lost"),
    ("lost_15kg",     "lost >= 15", "👑 15kg Lost"),
    ("lost_20kg",     "lost >= 20", "🏆 20kg Lost"),
]

# Quick lookup: milestone_key → display label (used in templates)
MILESTONE_LABELS = {key: label for key, _, label in MILESTONES}


# ---------------------------------------------------------------------------
# Weight calculations
# ---------------------------------------------------------------------------

def calculate_bmi(weight_kg, height_cm):
    """Calculate BMI from weight (kg) and height (cm)."""
    if not weight_kg or not height_cm or float(height_cm) == 0:
        return None
    h_m = float(height_cm) / 100.0
    return round(float(weight_kg) / (h_m * h_m), 1)


def calculate_weight_change(start_w, current_w):
    """Return (kg_lost, pct_lost) from a start and current weight.

    kg_lost is positive when weight decreased.
    pct_lost is the percentage of start weight that was lost.
    """
    start_w = float(start_w or 0)
    current_w = float(current_w or start_w)

    if start_w > 0:
        kg_lost = round(start_w - current_w, 1)
        pct_lost = round((kg_lost / start_w) * 100, 1)
    else:
        kg_lost = 0.0
        pct_lost = 0.0

    return kg_lost, pct_lost


# ---------------------------------------------------------------------------
# Streaks
# ---------------------------------------------------------------------------

def calculate_streak(user_id):
    """Calculate current and best consecutive-day check-in streaks."""
    rows = query(
        """SELECT DISTINCT (checked_in_at AT TIME ZONE 'UTC' AT TIME ZONE 'Australia/Sydney')::date AS d
           FROM checkins WHERE user_id = %s ORDER BY d DESC""",
        (user_id,),
    )
    if not rows:
        return {"current": 0, "best": 0}

    days = [r["d"] for r in rows]
    today = datetime.now(SYDNEY_TZ).date()

    # Current streak: must include today or yesterday to count
    current = 0
    expected = today
    if days[0] == today or days[0] == today - timedelta(days=1):
        expected = days[0]
        for d in days:
            if d == expected:
                current += 1
                expected -= timedelta(days=1)
            else:
                break

    # Best streak
    best = 1
    run = 1
    for i in range(1, len(days)):
        if days[i] == days[i - 1] - timedelta(days=1):
            run += 1
            best = max(best, run)
        else:
            run = 1

    best = max(best, current)
    return {"current": current, "best": best}


# ---------------------------------------------------------------------------
# Milestone checker
# ---------------------------------------------------------------------------

def check_milestones(user_id, user):
    """Check and award any new milestones after a check-in."""
    checkins = query(
        "SELECT weight_kg, checked_in_at FROM checkins WHERE user_id = %s ORDER BY checked_in_at ASC",
        (user_id,),
    )
    if not checkins:
        return

    starting = float(user.get("starting_weight_kg") or checkins[0]["weight_kg"])
    current = float(checkins[-1]["weight_kg"])
    total_lost = starting - current
    count = len(checkins)

    milestone_checks = [
        ("first_checkin", count >= 1),
        ("5_checkins",    count >= 5),
        ("10_checkins",   count >= 10),
        ("25_checkins",   count >= 25),
        ("lost_1kg",      total_lost >= 1),
        ("lost_2kg",      total_lost >= 2),
        ("lost_5kg",      total_lost >= 5),
        ("lost_10kg",     total_lost >= 10),
        ("lost_15kg",     total_lost >= 15),
        ("lost_20kg",     total_lost >= 20),
    ]

    for key, achieved in milestone_checks:
        if achieved:
            try:
                execute(
                    "INSERT INTO milestones (user_id, milestone_key) VALUES (%s, %s) ON CONFLICT DO NOTHING",
                    (user_id, key),
                )
            except Exception:
                pass


# ---------------------------------------------------------------------------
# Form helpers
# ---------------------------------------------------------------------------

def parse_profile_fields(form):
    """Extract the common profile fields from a request form.

    Returns a dict suitable for both signup and profile-update flows.
    """
    return {
        "display_name": form.get("display_name", "").strip(),
        "height_cm":    form.get("height_cm") or None,
        "age":          form.get("age") or None,
        "gender":       form.get("gender") or None,
        "goal_weight_kg":     form.get("goal_weight_kg") or None,
        "starting_weight_kg": form.get("starting_weight_kg") or None,
        "is_private":   form.get("is_private") == "on",
    }