package payCenter

import (
	"context"
	"errors"
	"fmt"
	"math/big"
	"strconv"
	"strings"

	"videoweb/pub/common/log"
)

// FenToYuan 用整数拆分分/元，避免浮点运算改变下单金额及签名原文。
func FenToYuan(price int64) string {
	amount := big.NewInt(price)
	negative := amount.Sign() < 0
	amount.Abs(amount)
	yuan := new(big.Int)
	fen := new(big.Int)
	yuan.QuoRem(amount, big.NewInt(100), fen)
	result := yuan.String()
	if fen.Sign() != 0 {
		result += fmt.Sprintf(".%02d", fen.Int64())
	}
	if negative {
		return "-" + result
	}
	return result
}

func YuanToFen(ctx context.Context, money string) int64 {
	result, err := ParseYuanToFen(money)
	if err != nil {
		log.Error("【新支付中心金额转换】元转分失败", log.E(err))
	}
	return result
}

// ParseYuanToFen 只接受十进制金额和最多两位小数，拒绝指数、内嵌符号和溢出。
func ParseYuanToFen(money string) (int64, error) {
	money = strings.TrimSpace(money)
	if money == "" {
		return 0, errors.New("money is empty")
	}

	negative := strings.HasPrefix(money, "-")
	if negative {
		money = money[1:]
		if money == "" {
			return 0, errors.New("money is empty")
		}
	}
	parts := strings.Split(money, ".")
	if len(parts) > 2 {
		return 0, fmt.Errorf("invalid money format %q", money)
	}
	if strings.ReplaceAll(money, ".", "") == "" {
		return 0, errors.New("money has no digits")
	}
	for _, part := range parts {
		for _, digit := range part {
			if digit < '0' || digit > '9' {
				return 0, errors.New("money must contain only decimal digits")
			}
		}
	}
	if parts[0] == "" {
		parts[0] = "0"
	}

	yuan, ok := new(big.Int).SetString(parts[0], 10)
	if !ok {
		return 0, fmt.Errorf("invalid yuan amount %q", money)
	}

	decimalPart := "00"
	if len(parts) == 2 {
		decimalPart = parts[1]
		if len(decimalPart) > 2 {
			return 0, fmt.Errorf("money has more than two decimal places: %q", money)
		}
		if len(decimalPart) == 0 {
			decimalPart = "00"
		} else if len(decimalPart) == 1 {
			decimalPart += "0"
		}
	}
	cents, err := strconv.ParseInt(decimalPart, 10, 64)
	if err != nil {
		return 0, fmt.Errorf("invalid fen amount %q: %w", money, err)
	}

	total := new(big.Int).Mul(yuan, big.NewInt(100))
	total.Add(total, big.NewInt(cents))
	if negative {
		total.Neg(total)
	}
	if !total.IsInt64() {
		return 0, fmt.Errorf("money overflows int64 fen: %q", money)
	}
	return total.Int64(), nil
}