"""Analytics service for progress dashboard and chart data.

Aggregates workout log data into stats, trends, and chart-ready formats.
"""

import re
from datetime import date, timedelta

import structlog
from sqlmodel import Session, select

from app.models.workout_day import WorkoutDay
from app.models.workout_log import WorkoutLog
from app.models.workout_session import WorkoutSession

logger = structlog.get_logger(__name__)


def _weight_to_float(weight_str: str) -> float:
    """Convert weight string to float for volume calculations.

    Args:
        weight_str: Weight like '30 lbs' or 'BW'.

    Returns:
        Numeric weight, or 0.0 for bodyweight.
    """
    if not weight_str or weight_str.upper() == "BW":
        return 0.0
    match = re.search(r"(\d+(?:\.\d+)?)", weight_str)
    return float(match.group(1)) if match else 0.0


class AnalyticsService:
    """Aggregates workout data for dashboards and charts.

    Args:
        session: An active SQLModel Session.
    """

    def __init__(self, session: Session) -> None:
        self._session = session

    def get_user_stats(self, user_id: int) -> dict:
        """Get summary statistics for a user.

        Returns:
            Dict with keys: total_sessions, total_volume, total_sets,
            current_streak, last_workout_date.
        """
        all_sessions = self._session.exec(
            select(WorkoutSession)
            .where(WorkoutSession.user_id == user_id)
            .order_by(WorkoutSession.date.desc())
        ).all()

        # Only count sessions that still have log entries
        sessions = []
        total_volume = 0.0
        total_sets = 0
        for ws in all_sessions:
            logs = self._session.exec(
                select(WorkoutLog).where(WorkoutLog.session_id == ws.id)
            ).all()
            if not logs:
                continue
            sessions.append(ws)
            for log_entry in logs:
                total_sets += 1
                weight = _weight_to_float(log_entry.weight_used)
                total_volume += log_entry.reps_completed * weight
        total_sessions = len(sessions)

        current_streak = 0
        if sessions:
            week_start = date.today() - timedelta(days=date.today().weekday())
            for week_offset in range(52):
                week_check = week_start - timedelta(weeks=week_offset)
                week_end = week_check + timedelta(days=6)
                has_session = any(
                    week_check <= ws.date <= week_end for ws in sessions
                )
                if has_session:
                    current_streak += 1
                else:
                    break

        last_workout = sessions[0].date if sessions else None

        return {
            "total_sessions": total_sessions,
            "total_volume": round(total_volume),
            "total_sets": total_sets,
            "current_streak": current_streak,
            "last_workout_date": last_workout,
        }

    def get_exercise_progress(
        self, user_id: int, exercise_id: int,
    ) -> dict:
        """Get chart-ready progress data for a specific exercise.

        Returns:
            Dict with keys: dates, reps, weights, volumes.
        """
        sessions = self._session.exec(
            select(WorkoutSession)
            .where(WorkoutSession.user_id == user_id)
            .order_by(WorkoutSession.date.asc())
        ).all()

        dates = []
        reps = []
        weights = []
        volumes = []

        for ws in sessions:
            logs = self._session.exec(
                select(WorkoutLog).where(
                    WorkoutLog.session_id == ws.id,
                    WorkoutLog.exercise_id == exercise_id,
                )
            ).all()

            if not logs:
                continue

            avg_reps = sum(
                log_entry.reps_completed for log_entry in logs
            ) / len(logs)
            weight = _weight_to_float(logs[0].weight_used)
            session_volume = sum(
                log_entry.reps_completed * _weight_to_float(log_entry.weight_used)
                for log_entry in logs
            )

            dates.append(ws.date.isoformat())
            reps.append(round(avg_reps, 1))
            weights.append(weight)
            volumes.append(round(session_volume))

        return {
            "dates": dates,
            "reps": reps,
            "weights": weights,
            "volumes": volumes,
        }

    def get_volume_by_day(self, user_id: int) -> dict:
        """Get total volume broken down by workout day.

        Returns:
            Dict mapping workout day name to total volume.
        """
        days = self._session.exec(select(WorkoutDay)).all()
        day_map = {d.id: d.name for d in days}

        sessions = self._session.exec(
            select(WorkoutSession)
            .where(WorkoutSession.user_id == user_id)
        ).all()

        volume_by_day = {}
        for ws in sessions:
            day_name = day_map.get(ws.workout_day_id, "Unknown")
            logs = self._session.exec(
                select(WorkoutLog).where(WorkoutLog.session_id == ws.id)
            ).all()

            if not logs:
                continue

            day_volume = sum(
                log_entry.reps_completed * _weight_to_float(log_entry.weight_used)
                for log_entry in logs
            )
            volume_by_day[day_name] = (
                volume_by_day.get(day_name, 0) + round(day_volume)
            )

        return volume_by_day