/**
 * Distribution Engine v1.2: Two-Phase Settlement System
 * 1. Primary: CPM Budget -> Participants (minus Platform Fee)
 * 2. Secondary: Credit Sale (FIN) -> Participants (minus Fee + Verification)
 * 3. Donation: Credit Allocation to SME (No Cash)
 */

import { supabase } from './supabase';
import { appendLedgerEntry } from './ledger';
import type { TransactionCategory } from '../types';

export interface PayoutResult {
  transactionId: string;
  totalDistributed: number;
  platformFee: number;
  recipientCount: number;
}

export interface DistributionRule {
  id: string;
  campaignId: string;
  citizenRewardRatio: number;
  smeDonationRatio: number;
  platformFeeRatio: number;
  ruleType: string;
  description: string | null;
}

/**
 * 캠페인별 정의된 동적 분배 룰 비율을 데이터베이스에서 가져온다. (P1-8)
 */
export async function getDistributionRules(campaignId: string): Promise<DistributionRule> {
  const fallback: DistributionRule = {
    id: 'fallback-rule',
    campaignId,
    citizenRewardRatio: 0.80,
    smeDonationRatio: 0.15,
    platformFeeRatio: 0.05,
    ruleType: 'DEFAULT',
    description: '폴백 기본 비율 (시민 80%, SME 15%, 플랫폼 5%)',
  };

  try {
    const { data, error } = await supabase
      .from('distribution_rules')
      .select('*')
      .eq('campaign_id', campaignId)
      .maybeSingle();

    if (error || !data) return fallback;

    return {
      id: String(data.id),
      campaignId: String(data.campaign_id),
      citizenRewardRatio: Number(data.citizen_reward_ratio),
      smeDonationRatio: Number(data.sme_donation_ratio),
      platformFeeRatio: Number(data.platform_fee_ratio),
      ruleType: String(data.rule_type),
      description: data.description ? String(data.description) : null,
    };
  } catch {
    return fallback;
  }
}

/**
 * [1차 분배] CPM이 예치한 캠페인 운영 예산을 시민 활동량에 따라 분배한다.
 * 플랫폼은 운영 대행 수수료(FEE)를 선취한다. (DB 정의 비율 기반 동적 분배)
 */
export async function distributeCampaignBudget(params: {
  campaignId: string;
  budgetAmount: number;
  platformFeeRate?: number; // 하위 호환성 유지
}): Promise<PayoutResult> {
  const { campaignId, budgetAmount, platformFeeRate } = params;
  const transactionId = crypto.randomUUID();

  // 0. 동적 분배 룰 쿼리 (P1-8)
  const rules = await getDistributionRules(campaignId);
  const feeRate = platformFeeRate !== undefined ? platformFeeRate : rules.platformFeeRatio;

  // 1. 플랫폼 수수료 및 보상 풀 계산
  const platformFee = Math.floor(budgetAmount * feeRate);
  const userPool = Math.floor(budgetAmount * rules.citizenRewardRatio);

  // 2. 활동 인증 데이터 집계
  const { data: participants } = await supabase
    .from('my_nature_contributions_view')
    .select('user_id, display_name, co2_grams')
    .eq('campaign_id', campaignId)
    .gt('co2_grams', 0);

  const totalCo2 = (participants || []).reduce((sum, p) => sum + Number(p.co2_grams), 0);
  
  if (totalCo2 === 0 || !participants || participants.length === 0) {
    throw new Error('분배할 활동 데이터가 없습니다.');
  }

  // 3. 플랫폼 수수료 원장 기록
  await appendLedgerEntry({
    transactionId,
    campaignId,
    senderId: 'CPM_ESCROW',
    senderName: '캠페인 예산 풀',
    receiverId: 'PLATFORM_OPERATIONS',
    receiverName: 'Carboany 플랫폼 운영',
    category: 'FEE_DEDUCTION' as TransactionCategory,
    asset: 'KRW',
    amount: platformFee,
    idempotencyKey: `p1-fee-${transactionId}`,
    description: `캠페인 운영 대행 수수료 (${(feeRate * 100).toFixed(1)}%)`,
  });

  // 4. 사용자별 활동비(현금성 포인트) 지급
  for (const p of participants) {
    const share = Number(p.co2_grams) / totalCo2;
    const amount = Math.floor(userPool * share);
    if (amount <= 0) continue;

    await appendLedgerEntry({
      transactionId,
      campaignId,
      senderId: 'CPM_ESCROW',
      senderName: '캠페인 예산 풀',
      receiverId: p.user_id,
      receiverName: p.display_name,
      category: 'POINT_REWARD' as TransactionCategory,
      asset: 'POINT',
      amount,
      idempotencyKey: `p1-reward-${campaignId}-${p.user_id}-${new Date().toISOString().slice(0, 10)}`,
      description: `활동 인증 보상 (감축량 기여도 ${(share * 100).toFixed(2)}%)`,
    });
  }

  return {
    transactionId,
    totalDistributed: userPool,
    platformFee,
    recipientCount: participants.length,
  };
}

/**
 * [2차 분배] 발행된 탄소배출권을 금융사(FIN)에 매각하고, 그 수익을 시민에게 추가 분배한다.
 */
export async function distributeCreditSaleProceeds(params: {
  tradeId: string;
  campaignId: string;
  saleAmount: number;
  verificationCost: number;
  platformFeeRate?: number; // 하위 호환성 유지
}): Promise<PayoutResult> {
  const { tradeId, campaignId, saleAmount, verificationCost, platformFeeRate } = params;

  // 0. 동적 분배 룰 쿼리 (P1-8)
  const rules = await getDistributionRules(campaignId);
  const feeRate = platformFeeRate !== undefined ? platformFeeRate : rules.platformFeeRatio;

  // 1. 공제액 계산
  const platformFee = Math.floor(saleAmount * feeRate);
  const netPool = Math.floor(saleAmount * rules.citizenRewardRatio) - verificationCost;

  if (netPool <= 0) throw new Error('공제 후 분배 가능한 잔액이 없습니다.');

  // 2. 기여 참여자 목록 재조회
  const { data: participants } = await supabase
    .from('my_nature_contributions_view')
    .select('user_id, display_name, co2_grams')
    .eq('campaign_id', campaignId)
    .gt('co2_grams', 0);

  const totalCo2 = (participants || []).reduce((sum, p) => sum + Number(p.co2_grams), 0);

  // 3. 원장 기록: 수수료 및 검증비
  await appendLedgerEntry({
    transactionId: tradeId,
    campaignId,
    senderId: 'FIN_PAYMENT',
    senderName: '금융사 매입 대금',
    receiverId: 'PLATFORM_FINANCE',
    receiverName: 'Carboany 금융 수수료',
    category: 'FEE_DEDUCTION' as TransactionCategory,
    asset: 'KRW',
    amount: platformFee,
    idempotencyKey: `p2-fee-${tradeId}`,
    description: `배출권 거래 중개 수수료 (${(feeRate * 100).toFixed(1)}%)`,
  });

  await appendLedgerEntry({
    transactionId: tradeId,
    campaignId,
    senderId: 'FIN_PAYMENT',
    senderName: '금융사 매입 대금',
    receiverId: 'VERIFICATION_ENTITY',
    receiverName: '외부 검증 기관',
    category: 'FEE_DEDUCTION' as TransactionCategory,
    asset: 'KRW',
    amount: verificationCost,
    idempotencyKey: `p2-verif-${tradeId}`,
    description: `외부 검증비 정산`,
  });

  // 4. 시민 추가 수익 공유
  if (totalCo2 > 0 && participants) {
    for (const p of participants) {
      const share = Number(p.co2_grams) / totalCo2;
      const amount = Math.floor(netPool * share);
      if (amount <= 0) continue;

      await appendLedgerEntry({
        transactionId: tradeId,
        campaignId,
        senderId: 'FIN_PAYMENT',
        senderName: '금융사 매입 대금',
        receiverId: p.user_id,
        receiverName: p.display_name,
        category: 'POINT_REWARD' as TransactionCategory,
        asset: 'POINT',
        amount,
        idempotencyKey: `p2-dist-${tradeId}-${p.user_id}`,
        description: `탄소배출권 매각 수익 공유 (기여도 ${(share * 100).toFixed(2)}%)`,
      });
    }
  }

  return {
    transactionId: tradeId,
    totalDistributed: netPool,
    platformFee,
    recipientCount: participants?.length || 0,
  };
}

/**
 * [상생/기부] 탄소배출권을 SME에게 기부/기여한다.
 */
export async function donateCreditsToSme(params: {
  campaignId: string;
  smeId: string;
  smeName: string;
  amountTon: number;
  reason?: string;
}): Promise<string> {
  const { campaignId, smeId, smeName, amountTon, reason } = params;
  const transactionId = crypto.randomUUID();

  await appendLedgerEntry({
    transactionId,
    campaignId,
    senderId: 'CPM_DECISION',
    senderName: '캠페인 의사결정체',
    receiverId: smeId,
    receiverName: smeName,
    category: 'CREDIT_DONATION' as TransactionCategory,
    asset: 'TON',
    amount: amountTon,
    idempotencyKey: `sme-alloc-${transactionId}`,
    description: reason || `${smeName} 기업에 탄소배출권 기부/기여 (${amountTon} tCO₂e)`,
  });

  return transactionId;
}