"""财务视角：应退金额、退费预览（原价口径）"""
from __future__ import annotations

from typing import Any, Optional

from models import StudentAccount, Course, MonthlySnapshot


def _f(val) -> float:
    if val is None:
        return 0.0
    return float(val)


def is_refunded_account(
    account: StudentAccount,
    ledger: Optional[dict] = None,
    snap: Optional[MonthlySnapshot] = None,
) -> bool:
    if (account.account_status or '') == 'refunded':
        return True
    if snap and _f(snap.refund_amount) > 0:
        end_bal = ledger.get('end_balance') if ledger else None
        end_less = ledger.get('end_lessons') if ledger else None
        if end_bal is not None and _f(end_bal) == 0 and _f(end_less) == 0:
            return True
    return False


def regular_lessons_from_ledger(account: StudentAccount, ledger: dict) -> float:
    v = ledger.get('end_lessons')
    if v is not None:
        return _f(v)
    return _f(account.normal_hours)


def gift_lessons_from_ledger(account: StudentAccount, ledger: dict) -> float:
    v = ledger.get('end_gift_lessons')
    if v is not None:
        return _f(v)
    return _f(account.gifted_hours)


def original_unit_price(
    account: StudentAccount,
    snap: Optional[MonthlySnapshot] = None,
) -> Optional[float]:
    if account.original_price_per_lesson is not None:
        v = float(account.original_price_per_lesson)
        if v > 0:
            return v
    if snap and snap.unit_price is not None:
        v = float(snap.unit_price)
        if v > 0:
            return v
    return None


def account_refund_display(
    account: StudentAccount,
    ledger: Optional[dict] = None,
    snap: Optional[MonthlySnapshot] = None,
) -> dict[str, Any]:
    """单账户应退展示（列表用）"""
    ledger = ledger or {}
    if is_refunded_account(account, ledger, snap):
        return {'kind': 'refunded', 'text': '已退费', 'sort_value': -1.0}

    orig = original_unit_price(account, snap)
    regular = regular_lessons_from_ledger(account, ledger)

    if orig is None:
        return {'kind': 'no_price', 'text': '-', 'sort_value': -1.0}

    if regular <= 0:
        total = _f(ledger.get('end_total_lessons')) or _f(account.total_hours)
        gift = gift_lessons_from_ledger(account, ledger)
        if gift > 0 or total > 0:
            return {'kind': 'gift_only', 'text': '¥0（已入赠课）', 'sort_value': 0.0}
        return {'kind': 'zero', 'text': '¥0.00', 'amount': 0.0, 'sort_value': 0.0}

    amount = round(orig * regular, 2)
    return {
        'kind': 'amount',
        'text': None,
        'amount': amount,
        'sort_value': amount,
    }


def aggregate_student_refund(
    accounts: list[StudentAccount],
    ledger_by_account: dict[int, dict],
    snap_by_account: Optional[dict[int, MonthlySnapshot]] = None,
) -> dict[str, Any]:
    """学员行：汇总多账户应退展示"""
    snap_by_account = snap_by_account or {}
    if not accounts:
        return {'kind': 'none', 'text': '-', 'sort_value': -1.0}

    parts = [
        account_refund_display(
            a,
            ledger_by_account.get(a.id, {}),
            snap_by_account.get(a.id),
        )
        for a in accounts
    ]
    if all(p['kind'] == 'refunded' for p in parts):
        return {'kind': 'refunded', 'text': '已退费', 'sort_value': -1.0}
    if all(p['kind'] == 'no_price' for p in parts):
        return {'kind': 'no_price', 'text': '-', 'sort_value': -1.0}

    amounts = [p['amount'] for p in parts if p['kind'] == 'amount']
    if amounts:
        total = round(sum(amounts), 2)
        return {'kind': 'amount', 'amount': total, 'sort_value': total}

    if all(p['kind'] in ('gift_only', 'zero') for p in parts):
        return {'kind': 'gift_only', 'text': '¥0（已入赠课）', 'sort_value': 0.0}

    return {'kind': 'no_price', 'text': '-', 'sort_value': -1.0}


def build_refund_preview(
    account: StudentAccount,
    course: Optional[Course],
    ledger: dict,
    snap: Optional[MonthlySnapshot] = None,
) -> dict[str, Any]:
    """学员详情：退费预览区块数据"""
    regular = regular_lessons_from_ledger(account, ledger)
    gift = gift_lessons_from_ledger(account, ledger)
    consumed = _f(account.consumed_normal)
    paid_total = _f(account.cumulative_amount)
    balance = ledger.get('end_balance')
    if balance is None:
        balance = None
    else:
        balance = _f(balance)

    orig_unit = original_unit_price(account)
    total_purchased_normal = consumed + regular
    total_all_hours = consumed + regular + gift + _f(account.consumed_gifted)

    if orig_unit is None:
        return {
            'has_original': False,
            'course_name': (course.course_code or course.name) if course else '—',
            'refund_line': None,
        }

    original_total = round(orig_unit * total_purchased_normal, 2) if total_purchased_normal > 0 else 0.0
    discount = round(max(0, original_total - paid_total), 2)
    consume_unit = round(paid_total / total_all_hours, 2) if total_all_hours > 0 else 0.0
    refund_due = round(orig_unit * regular, 2) if regular > 0 else 0.0

    if is_refunded_account(account, ledger, snap):
        refund_due = 0.0
        refund_label = '已退费'
    elif regular <= 0 and (gift > 0 or _f(ledger.get('end_total_lessons')) > 0):
        refund_due = 0.0
        refund_label = '¥0（已入赠课）'
    else:
        refund_label = None

    return {
        'has_original': True,
        'course_name': (course.course_code or course.name) if course else '—',
        'original_total': original_total,
        'paid_total': paid_total,
        'discount': discount,
        'original_unit': orig_unit,
        'consume_unit': consume_unit,
        'consumed_normal': consumed,
        'regular_remaining': regular,
        'gift_remaining': gift,
        'balance': balance,
        'refund_due': refund_due,
        'refund_label': refund_label,
    }


def build_students_finance(
    students: list,
    accounts_by_student: dict[int, list[StudentAccount]],
    ledger_by_account: dict[int, dict],
    snap_by_account: dict[int, MonthlySnapshot],
) -> dict[int, dict]:
    out = {}
    for s in students:
        accs = accounts_by_student.get(s.id, [])
        out[s.id] = aggregate_student_refund(
            accs,
            ledger_by_account,
            snap_by_account,
        )
    return out