# /opt/docker/dev/service_finder/backend/app/services/commission_service.py
"""
CommissionRule service layer — CRUD + Priority Resolution Engine + 2-Level MLM Distribution.

THOUGHT PROCESS:
- The Priority Algorithm (Campaign > Region > Tier) is implemented in
  get_active_rule() using SQLAlchemy case() expressions for server-side
  ordering. This avoids loading all matching rules into Python memory.
- Campaign rules (is_campaign=True) always sort before permanent rules.
- Specific region match (e.g. "HU") sorts before "GLOBAL".
- Higher tiers (PLATINUM=0, VIP=1, STANDARD=2, ENTERPRISE=3) sort first.
- Soft-delete is handled via is_active=False (not actual row deletion).
- The service uses async/await throughout for FastAPI compatibility.
- 2-Level MLM: distribute_commission() resolves Gen1 (direct referrer) and
  Gen2 (upline) payouts using commission_percent and upline_commission_percent.
"""

import logging
from datetime import date
from decimal import Decimal
from typing import Optional, List, Sequence
from sqlalchemy import select, func, case, or_, and_, delete as sa_delete
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy.orm import selectinload

from app.models.marketplace.commission import (
    CommissionRule,
    CommissionRuleType,
    CommissionTier,
)
from app.models.identity.identity import User
from app.schemas.commission import (
    CommissionRuleCreate,
    CommissionRuleUpdate,
    CommissionDistributionRequest,
    CommissionDistributionItem,
    CommissionDistributionResponse,
)

logger = logging.getLogger(__name__)


# ──────────────────────────────────────────────────────────────────────────────
# CRUD Operations
# ──────────────────────────────────────────────────────────────────────────────


async def create_commission_rule(
    db: AsyncSession,
    data: CommissionRuleCreate,
    admin_user_id: int,
) -> CommissionRule:
    """
    Create a new commission rule with validation.

    Args:
        db: Database session.
        data: Pydantic schema with rule data.
        admin_user_id: ID of the admin creating the rule.

    Returns:
        The newly created CommissionRule instance.
    """
    rule = CommissionRule(
        rule_type=CommissionRuleType(data.rule_type.value),
        tier=CommissionTier(data.tier.value),
        region_code=data.region_code,
        xp_reward=data.xp_reward,
        credit_reward=data.credit_reward,
        commission_percent=data.commission_percent,
        upline_commission_percent=data.upline_commission_percent,
        renewal_commission_percent=data.renewal_commission_percent,
        commission_max_amount=data.commission_max_amount,
        is_campaign=data.is_campaign,
        start_date=data.start_date,
        end_date=data.end_date,
        name=data.name,
        description=data.description,
        is_active=data.is_active,
        created_by=admin_user_id,
    )
    db.add(rule)
    await db.commit()
    await db.refresh(rule)
    logger.info(
        "Commission rule created: id=%d type=%s tier=%s region=%s",
        rule.id, rule.rule_type, rule.tier, rule.region_code,
    )
    return rule


async def update_commission_rule(
    db: AsyncSession,
    rule_id: int,
    data: CommissionRuleUpdate,
) -> Optional[CommissionRule]:
    """
    Partially update an existing commission rule.

    Only the fields explicitly set in the update schema are applied.
    Returns None if the rule does not exist.
    """
    stmt = select(CommissionRule).where(CommissionRule.id == rule_id)
    result = await db.execute(stmt)
    rule = result.scalar_one_or_none()
    if not rule:
        return None

    update_data = data.model_dump(exclude_unset=True)
    for field, value in update_data.items():
        # Map enum fields from schema enums to model enums
        if field == "rule_type" and value is not None:
            setattr(rule, field, CommissionRuleType(value.value))
        elif field == "tier" and value is not None:
            setattr(rule, field, CommissionTier(value.value))
        else:
            setattr(rule, field, value)

    await db.commit()
    await db.refresh(rule)
    logger.info("Commission rule updated: id=%d", rule.id)
    return rule


async def deactivate_commission_rule(
    db: AsyncSession,
    rule_id: int,
) -> Optional[CommissionRule]:
    """
    Soft-delete a commission rule by setting is_active=False.

    Returns the deactivated rule, or None if not found.
    """
    stmt = select(CommissionRule).where(CommissionRule.id == rule_id)
    result = await db.execute(stmt)
    rule = result.scalar_one_or_none()
    if not rule:
        return None

    rule.is_active = False
    await db.commit()
    await db.refresh(rule)
    logger.info("Commission rule deactivated: id=%d", rule.id)
    return rule


async def hard_delete_commission_rule(
    db: AsyncSession,
    rule_id: int,
) -> bool:
    """
    Permanently delete a commission rule (admin-only, use with caution).

    Returns True if deleted, False if not found.
    """
    stmt = select(CommissionRule).where(CommissionRule.id == rule_id)
    result = await db.execute(stmt)
    rule = result.scalar_one_or_none()
    if not rule:
        return False

    await db.delete(rule)
    await db.commit()
    logger.info("Commission rule hard-deleted: id=%d", rule_id)
    return True


# ──────────────────────────────────────────────────────────────────────────────
# Priority Resolution Engine
# ──────────────────────────────────────────────────────────────────────────────


async def get_active_rule(
    db: AsyncSession,
    rule_type: CommissionRuleType,
    tier: CommissionTier,
    region_code: str,
    transaction_date: date,
) -> Optional[CommissionRule]:
    """
    Priority Resolution Algorithm: Find the most specific active rule.

    Resolution order (highest priority first):
    1. Campaign rules (is_campaign=True) over permanent rules
    2. Most specific region match (e.g. "HU" > "GLOBAL")
    3. Highest tier match (PLATINUM > VIP > STANDARD > ENTERPRISE)

    Falls back to GLOBAL/STANDARD default if no specific match exists.

    Args:
        db: Database session.
        rule_type: L1_REWARD or L2_COMMISSION.
        tier: The referrer/buyer's tier.
        region_code: ISO 3166-1 alpha-2 region code.
        transaction_date: The date of the transaction.

    Returns:
        The best matching CommissionRule, or None if no rule exists.
    """
    # Build priority expressions using SQLAlchemy case()
    # Lower numeric value = higher priority
    campaign_priority = case(
        (CommissionRule.is_campaign == True, 0),   # campaigns first
        else_=1
    )

    region_priority = case(
        (CommissionRule.region_code == region_code, 0),   # exact region match
        (CommissionRule.region_code == "GLOBAL", 1),       # global fallback
        else_=2
    )

    # Tier ordering: PLATINUM (0) > VIP (1) > STANDARD (2) > ENTERPRISE (3) > CONTRACTED (4)
    tier_order = {
        CommissionTier.PLATINUM: 0,
        CommissionTier.VIP: 1,
        CommissionTier.STANDARD: 2,
        CommissionTier.ENTERPRISE: 3,
        CommissionTier.CONTRACTED: 4,
    }
    tier_priority = case(
        *[(CommissionRule.tier == k, v) for k, v in tier_order.items()],
        else_=99
    )

    stmt = (
        select(CommissionRule)
        .where(
            CommissionRule.rule_type == rule_type,
            CommissionRule.is_active == True,
            # Date range: NULL means "always valid"
            or_(
                CommissionRule.start_date.is_(None),
                CommissionRule.start_date <= transaction_date
            ),
            or_(
                CommissionRule.end_date.is_(None),
                CommissionRule.end_date >= transaction_date
            ),
            # Region: match exact or GLOBAL
            or_(
                CommissionRule.region_code == region_code,
                CommissionRule.region_code == "GLOBAL"
            ),
            # Tier: match exact or STANDARD fallback
            or_(
                CommissionRule.tier == tier,
                CommissionRule.tier == CommissionTier.STANDARD
            )
        )
        .order_by(campaign_priority, region_priority, tier_priority)
        .limit(1)
    )

    result = await db.execute(stmt)
    rule = result.scalar_one_or_none()

    if rule:
        logger.debug(
            "Active rule resolved: id=%d type=%s tier=%s region=%s campaign=%s",
            rule.id, rule.rule_type, rule.tier, rule.region_code, rule.is_campaign,
        )
    else:
        logger.warning(
            "No active rule found for type=%s tier=%s region=%s date=%s",
            rule_type, tier, region_code, transaction_date,
        )

    return rule


# ──────────────────────────────────────────────────────────────────────────────
# Admin Listing with Filters & Pagination
# ──────────────────────────────────────────────────────────────────────────────


async def list_rules(
    db: AsyncSession,
    page: int = 1,
    page_size: int = 20,
    rule_type: Optional[CommissionRuleType] = None,
    tier: Optional[CommissionTier] = None,
    region_code: Optional[str] = None,
    is_active: Optional[bool] = None,
    is_campaign: Optional[bool] = None,
) -> tuple[Sequence[CommissionRule], int]:
    """
    List commission rules with optional filters and pagination.

    Returns:
        Tuple of (rules_list, total_count).
    """
    # Build base query
    base_query = select(CommissionRule)

    # Apply filters
    conditions = []
    if rule_type is not None:
        conditions.append(CommissionRule.rule_type == rule_type)
    if tier is not None:
        conditions.append(CommissionRule.tier == tier)
    if region_code is not None:
        conditions.append(CommissionRule.region_code == region_code)
    if is_active is not None:
        conditions.append(CommissionRule.is_active == is_active)
    if is_campaign is not None:
        conditions.append(CommissionRule.is_campaign == is_campaign)

    if conditions:
        base_query = base_query.where(and_(*conditions))

    # Get total count
    count_query = select(func.count()).select_from(base_query.subquery())
    count_result = await db.execute(count_query)
    total = count_result.scalar() or 0

    # Apply pagination and ordering
    offset = (page - 1) * page_size
    stmt = (
        base_query
        .order_by(CommissionRule.updated_at.desc())
        .offset(offset)
        .limit(page_size)
    )

    result = await db.execute(stmt)
    rules = result.scalars().all()

    return rules, total


# ──────────────────────────────────────────────────────────────────────────────
# 2-Level MLM Commission Distribution Engine
# ──────────────────────────────────────────────────────────────────────────────


async def _lookup_user(
    db: AsyncSession,
    user_id: int,
) -> Optional[User]:
    """Look up a user by ID, return None if not found or deleted."""
    stmt = select(User).where(
        User.id == user_id,
        User.is_deleted == False,
    )
    result = await db.execute(stmt)
    return result.scalar_one_or_none()


async def _calculate_commission(
    amount: float,
    percent: Optional[float],
    max_amount: Optional[float],
) -> float:
    """
    Calculate commission amount from a percentage, capped by max_amount.

    Args:
        amount: The transaction/subscription amount.
        percent: The commission percentage (e.g. 5.00 = 5%).
        max_amount: Optional cap on the commission payout.

    Returns:
        The calculated commission amount.
    """
    if not percent or percent <= 0:
        return 0.0

    commission = float(Decimal(str(amount)) * Decimal(str(percent)) / Decimal("100"))

    if max_amount is not None and max_amount > 0:
        commission = min(commission, float(max_amount))

    return round(commission, 2)


async def distribute_commission(
    db: AsyncSession,
    request: CommissionDistributionRequest,
) -> CommissionDistributionResponse:
    """
    2-Level MLM Commission Distribution Engine.

    When a referred company makes a purchase, this function:
    1. Looks up the buyer and their referrer (Gen1)
    2. Finds the active commission rule for Gen1's tier/region
    3. Calculates Gen1's commission using commission_percent
    4. If Gen1 has a referrer (Gen2/upline), calculates Gen2's commission
       using upline_commission_percent from the SAME rule

    Args:
        db: Database session.
        request: Distribution request with buyer_user_id, transaction_amount,
                 transaction_date, and region_code.

    Returns:
        CommissionDistributionResponse with payout breakdown for Gen1 and Gen2.
    """
    items: List[CommissionDistributionItem] = []
    total_commission = 0.0

    # 1. Look up the buyer
    buyer = await _lookup_user(db, request.buyer_user_id)
    if not buyer:
        logger.warning(
            "Commission distribution: buyer user %d not found or deleted",
            request.buyer_user_id,
        )
        return CommissionDistributionResponse(
            transaction_amount=request.transaction_amount,
            items=[],
            total_commission=0.0,
        )

    # 2. Find Gen1 (the buyer's direct referrer)
    gen1_user_id = buyer.referred_by_id
    if not gen1_user_id:
        logger.info(
            "Commission distribution: buyer %d has no referrer (Gen1)",
            request.buyer_user_id,
        )
        return CommissionDistributionResponse(
            transaction_amount=request.transaction_amount,
            items=[],
            total_commission=0.0,
        )

    gen1 = await _lookup_user(db, gen1_user_id)
    if not gen1:
        logger.warning(
            "Commission distribution: Gen1 user %d not found or deleted",
            gen1_user_id,
        )
        return CommissionDistributionResponse(
            transaction_amount=request.transaction_amount,
            items=[],
            total_commission=0.0,
        )

    # 3. Resolve the active commission rule for Gen1
    gen1_tier = CommissionTier(gen1.commission_tier) if hasattr(gen1, 'commission_tier') and gen1.commission_tier else CommissionTier.STANDARD
    try:
        gen1_tier_enum = CommissionTier(gen1_tier)
    except ValueError:
        gen1_tier_enum = CommissionTier.STANDARD

    rule = await get_active_rule(
        db,
        rule_type=CommissionRuleType.L2_COMMISSION,
        tier=gen1_tier_enum,
        region_code=request.region_code,
        transaction_date=request.transaction_date,
    )

    if not rule:
        logger.warning(
            "Commission distribution: no active L2_COMMISSION rule for "
            "tier=%s region=%s date=%s",
            gen1_tier_enum, request.region_code, request.transaction_date,
        )
        return CommissionDistributionResponse(
            transaction_amount=request.transaction_amount,
            items=[],
            total_commission=0.0,
        )

    # 4. Calculate Gen1 commission
    gen1_amount = await _calculate_commission(
        request.transaction_amount,
        float(rule.commission_percent) if rule.commission_percent else None,
        float(rule.commission_max_amount) if rule.commission_max_amount else None,
    )

    if gen1_amount > 0:
        items.append(CommissionDistributionItem(
            level=1,
            user_id=gen1.id,
            commission_percent=float(rule.commission_percent) if rule.commission_percent else 0.0,
            commission_amount=gen1_amount,
            rule_id=rule.id,
        ))
        total_commission += gen1_amount

    # 5. Find Gen2 (Gen1's referrer / upline)
    gen2_user_id = gen1.referred_by_id
    if gen2_user_id:
        gen2 = await _lookup_user(db, gen2_user_id)
        if gen2:
            # 6. Calculate Gen2 commission using upline_commission_percent
            gen2_amount = await _calculate_commission(
                request.transaction_amount,
                float(rule.upline_commission_percent) if rule.upline_commission_percent else None,
                float(rule.commission_max_amount) if rule.commission_max_amount else None,
            )

            if gen2_amount > 0:
                items.append(CommissionDistributionItem(
                    level=2,
                    user_id=gen2.id,
                    commission_percent=float(rule.upline_commission_percent) if rule.upline_commission_percent else 0.0,
                    commission_amount=gen2_amount,
                    rule_id=rule.id,
                ))
                total_commission += gen2_amount
        else:
            logger.warning(
                "Commission distribution: Gen2 user %d not found or deleted",
                gen2_user_id,
            )

    logger.info(
        "Commission distributed: buyer=%d gen1=%d(%.2f%%) gen2=%d(%.2f%%) "
        "amount=%.2f total_commission=%.2f rule=%d",
        request.buyer_user_id,
        gen1.id,
        float(rule.commission_percent) if rule.commission_percent else 0,
        gen2_user_id or 0,
        float(rule.upline_commission_percent) if rule.upline_commission_percent else 0,
        request.transaction_amount,
        total_commission,
        rule.id,
    )

    return CommissionDistributionResponse(
        transaction_amount=request.transaction_amount,
        items=items,
        total_commission=round(total_commission, 2),
    )