"""MinimumWorkload service — CRUD and validation helpers.

BE-CAL-004: user-level workload config read/write + future validation entry point.
"""

from __future__ import annotations

import copy
from typing import Optional

from sqlalchemy.orm import Session

from app.models.minimum_workload import (
    DEFAULT_WORKLOAD_CONFIG,
    CATEGORIES,
    PERIODS,
    MinimumWorkload,
)
from app.schemas.calendar import (
    MinimumWorkloadConfig,
    MinimumWorkloadUpdate,
    WorkloadWarningItem,
)


# ---------------------------------------------------------------------------
# Read
# ---------------------------------------------------------------------------

def get_workload_config(db: Session, user_id: int) -> dict:
    """Return the raw config dict for *user_id*, falling back to defaults."""
    row = db.query(MinimumWorkload).filter(MinimumWorkload.user_id == user_id).first()
    if row is None:
        return copy.deepcopy(DEFAULT_WORKLOAD_CONFIG)
    return row.config


def get_workload_row(db: Session, user_id: int) -> Optional[MinimumWorkload]:
    """Return the ORM row or None."""
    return db.query(MinimumWorkload).filter(MinimumWorkload.user_id == user_id).first()


# ---------------------------------------------------------------------------
# Write (upsert)
# ---------------------------------------------------------------------------

def upsert_workload_config(
    db: Session,
    user_id: int,
    update: MinimumWorkloadUpdate,
) -> MinimumWorkload:
    """Create or update the workload config for *user_id*.

    Only the periods present in *update* are overwritten; the rest keep
    their current (or default) values.
    """
    row = db.query(MinimumWorkload).filter(MinimumWorkload.user_id == user_id).first()

    if row is None:
        row = MinimumWorkload(
            user_id=user_id,
            config=copy.deepcopy(DEFAULT_WORKLOAD_CONFIG),
        )
        db.add(row)

    # Merge provided periods into existing config
    current = copy.deepcopy(row.config) if row.config else copy.deepcopy(DEFAULT_WORKLOAD_CONFIG)

    for period in PERIODS:
        period_data = getattr(update, period, None)
        if period_data is not None:
            current[period] = period_data.model_dump()

    # Ensure JSON column is flagged as dirty for SQLAlchemy
    row.config = current
    db.flush()
    return row


def replace_workload_config(
    db: Session,
    user_id: int,
    config: MinimumWorkloadConfig,
) -> MinimumWorkload:
    """Full replace of the workload config for *user_id*."""
    row = db.query(MinimumWorkload).filter(MinimumWorkload.user_id == user_id).first()

    if row is None:
        row = MinimumWorkload(user_id=user_id, config=config.model_dump())
        db.add(row)
    else:
        row.config = config.model_dump()

    db.flush()
    return row


# ---------------------------------------------------------------------------
# Validation entry point (BE-CAL-007 will flesh this out)
# ---------------------------------------------------------------------------

def check_workload_warnings(
    db: Session,
    user_id: int,
    scheduled_minutes: dict[str, dict[str, int]],
) -> list[WorkloadWarningItem]:
    """Compare *scheduled_minutes* against the user's configured thresholds.

    ``scheduled_minutes`` has the same shape as the config:
        {"daily": {"work": N, ...}, "weekly": {...}, ...}

    Returns a list of warnings for every (period, category) where the
    scheduled total is below the minimum.  An empty list means no warnings.

    This is the entry point that BE-CAL-007 and the calendar API endpoints
    will call.
    """
    config = get_workload_config(db, user_id)
    warnings: list[WorkloadWarningItem] = []

    for period in PERIODS:
        cfg_period = config.get(period, {})
        sch_period = scheduled_minutes.get(period, {})
        for cat in CATEGORIES:
            minimum = cfg_period.get(cat, 0)
            if minimum <= 0:
                continue
            current = sch_period.get(cat, 0)
            if current < minimum:
                shortfall = minimum - current
                warnings.append(WorkloadWarningItem(
                    period=period,
                    category=cat,
                    current_minutes=current,
                    minimum_minutes=minimum,
                    shortfall_minutes=shortfall,
                    message=(
                        f"{period.capitalize()} {cat.replace('_', '-')} workload "
                        f"is {current} min, below minimum of {minimum} min "
                        f"(shortfall: {shortfall} min)"
                    ),
                ))

    return warnings