package handler

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"

	logmodel "github.com/perfect-panel/server/internal/model/log"
	"github.com/perfect-panel/server/internal/model/lottery"
	"gorm.io/gorm"
)

// CommissionHandler 发放"抽奖佣金"。写 user.commission 增量 + system_logs
// (Type=Commission, CommissionType=339 Lottery) —— 用新增的 CommissionTypeLottery
// 常量与 Purchase/Renewal 区分，账目侧对账更清晰。
//
// 幂等模型：DispatchRequest.IdempotencyKey → lottery_grant_ledger.external_ref。
// Reserve 命中即幂等，未命中才走真实发放。commission 直接发给中奖者本人，不做
// 家庭组归位（family owner 不代收成员的抽奖佣金）。
type CommissionHandler struct {
	deps CommissionDeps
}

// CommissionDeps 是 CommissionHandler 需要的最小依赖集。抽出到接口方便测试。
type CommissionDeps struct {
	Ledger lottery.LedgerService
	// UpdateCommission 对齐 UserModel.UpdateCommission 签名。
	UpdateCommission func(ctx context.Context, userId int64, delta int64, tx ...*gorm.DB) error
	// WriteCommissionLog 对齐 common.WriteCommissionLog 签名。
	WriteCommissionLog func(tx *gorm.DB, objectID int64, logType uint16, amount int64, orderNo string) error
}

// NewCommissionHandler 构造真实的 commission handler。
func NewCommissionHandler(deps CommissionDeps) *CommissionHandler {
	return &CommissionHandler{deps: deps}
}

func (*CommissionHandler) Type() string               { return lottery.PrizeTypeCommission }
func (*CommissionHandler) IsAuto() bool               { return true }
func (*CommissionHandler) ValidateClaim([]byte) error { return nil }

type commissionConfig struct {
	// AmountCents 是"分"级别的金额（与 user.commission 存储单位对齐）。
	AmountCents int64 `json:"amount_cents"`
}

type commissionPayload struct {
	Amount  int64  `json:"amount"`
	LogType uint16 `json:"log_type"`
	Message string `json:"message"`
	OrderNo string `json:"order_no"`
}

// Dispatch 在 caller 的事务内为中奖人发放佣金。
func (h *CommissionHandler) Dispatch(ctx context.Context, tx *gorm.DB, req lottery.DispatchRequest) (lottery.DispatchResult, error) {
	if tx == nil {
		return lottery.DispatchResult{}, errors.New("commission handler requires a transaction")
	}
	if req.IdempotencyKey == "" {
		return lottery.DispatchResult{}, errors.New("commission handler requires DispatchRequest.IdempotencyKey")
	}
	if h.deps.UpdateCommission == nil || h.deps.WriteCommissionLog == nil {
		return lottery.DispatchResult{}, errors.New("commission handler deps not fully wired")
	}

	var cfg commissionConfig
	if err := json.Unmarshal([]byte(req.Prize.Config), &cfg); err != nil {
		return lottery.DispatchResult{}, fmt.Errorf("decode commission config: %w", err)
	}
	if cfg.AmountCents <= 0 {
		return lottery.DispatchResult{}, fmt.Errorf("commission config amount_cents must be > 0, got %d", cfg.AmountCents)
	}

	// 佣金"发给中奖者本人"（不走家庭组归位）。
	targetUserID := req.UserId

	entry := lottery.GrantLedger{
		ExternalRef: req.IdempotencyKey,
		HandlerType: lottery.PrizeTypeCommission,
		UserId:      targetUserID,
		ActivityId:  req.ActivityId,
		DrawId:      req.DrawId,
		Amount:      cfg.AmountCents,
	}
	row, alreadyExisted, err := h.deps.Ledger.Reserve(ctx, tx, entry)
	if err != nil {
		return lottery.DispatchResult{}, fmt.Errorf("reserve grant ledger: %w", err)
	}
	if alreadyExisted {
		var payload commissionPayload
		if row.Payload != "" {
			_ = json.Unmarshal([]byte(row.Payload), &payload)
		}
		if payload.Message == "" {
			payload.Message = "佣金已到账"
		}
		return lottery.DispatchResult{State: lottery.DispatchStateAutoClaimed, Message: payload.Message}, nil
	}

	// 未存在 → 真实发放。UpdateCommission 用 gorm.Expr 原子累加，避免丢更新。
	if err := h.deps.UpdateCommission(ctx, targetUserID, cfg.AmountCents, tx); err != nil {
		return lottery.DispatchResult{}, fmt.Errorf("update commission for user %d: %w", targetUserID, err)
	}
	// 传 external_ref 到 WriteCommissionLog 的 orderNo 位（"lottery:*"），与业务 order 命名域天然区分。
	if err := h.deps.WriteCommissionLog(tx, targetUserID, logmodel.CommissionTypeLottery, cfg.AmountCents, req.IdempotencyKey); err != nil {
		return lottery.DispatchResult{}, fmt.Errorf("write commission log: %w", err)
	}

	payload := commissionPayload{
		Amount:  cfg.AmountCents,
		LogType: logmodel.CommissionTypeLottery,
		OrderNo: req.IdempotencyKey,
		Message: fmt.Sprintf("佣金已到账 %d", cfg.AmountCents),
	}
	raw, err := json.Marshal(payload)
	if err != nil {
		return lottery.DispatchResult{}, fmt.Errorf("marshal ledger payload: %w", err)
	}
	if err := tx.WithContext(ctx).
		Model(&lottery.GrantLedger{}).
		Where("id = ?", row.Id).
		UpdateColumn("payload", string(raw)).Error; err != nil {
		return lottery.DispatchResult{}, fmt.Errorf("update ledger payload: %w", err)
	}
	return lottery.DispatchResult{State: lottery.DispatchStateAutoClaimed, Message: payload.Message}, nil
}