package payment

import (
	"context"
	"errors"
)

// Channel codes used in API body `channel`.
const (
	ChannelWechat = "wechat"
	ChannelAlipay = "alipay"
	ChannelBank   = "bank"
)

// Client scenes used in API body `client`.
const (
	ClientMiniProgram = "mini_program"
	ClientApp         = "app"
	ClientH5          = "h5"
)

var (
	ErrUnsupportedChannel = errors.New("unsupported payment channel")
	ErrUnsupportedClient  = errors.New("unsupported payment client for channel")
	ErrNotImplemented     = errors.New("payment channel not implemented")
)

// PrepayRequest is channel-agnostic prepay input.
type PrepayRequest struct {
	OutTradeNo  string
	Description string
	AmountFen   int64
	Currency    string
	NotifyURL   string
	Attach      string
	// Payer identity: WeChat uses OpenID; Alipay uses BuyerID.
	OpenID  string
	BuyerID string
	Extra   map[string]string
}

// PrepayResult holds client-side invoke params (JSON-serializable).
type PrepayResult struct {
	PrepayID string         `json:"prepay_id,omitempty"`
	Payload  map[string]any `json:"payload"`
}

// RefundRequest is channel-agnostic refund input.
type RefundRequest struct {
	OutTradeNo    string
	TransactionID string
	OutRefundNo   string
	Reason        string
	NotifyURL     string
	RefundFen     int64
	TotalFen      int64
	Currency      string
}

// RefundResult is channel-agnostic refund output.
type RefundResult struct {
	RefundID      string `json:"refund_id"`
	OutRefundNo   string `json:"out_refund_no"`
	TransactionID string `json:"transaction_id"`
	OutTradeNo    string `json:"out_trade_no"`
	Status        string `json:"status"`
}

// NotifyResult is a normalized pay-success notify.
type NotifyResult struct {
	OutTradeNo    string `json:"out_trade_no"`
	TransactionID string `json:"transaction_id"`
	TradeState    string `json:"trade_state"`
	AmountFen     int64  `json:"amount_fen"`
	Success       bool   `json:"success"`
	Attach        string `json:"attach,omitempty"`
}

// Channel abstracts WeChat / Alipay / bank card providers.
type Channel interface {
	Name() string
	Prepay(ctx context.Context, client string, req *PrepayRequest) (*PrepayResult, error)
	Refund(ctx context.Context, req *RefundRequest) (*RefundResult, error)
	ParsePayNotify(ctx context.Context, headers map[string]string, body []byte) (*NotifyResult, error)
}