package binancerecharge

import (
	"fmt"
	"math/big"
	"net/http"
	"strings"
)

func parsePositiveDecimal(value string, field string) (*big.Rat, string, error) {
	normalized, err := normalizeDecimal(value)
	if err != nil {
		return nil, "", NewAppError(http.StatusBadRequest, "invalid_"+field, field+" must be a decimal number")
	}
	rat, ok := new(big.Rat).SetString(normalized)
	if !ok || rat.Sign() <= 0 {
		return nil, "", NewAppError(http.StatusBadRequest, "invalid_"+field, field+" must be greater than 0")
	}
	return rat, normalized, nil
}

func parseNonNegativeDecimal(value string, field string) (*big.Rat, string, error) {
	normalized, err := normalizeDecimal(value)
	if err != nil {
		return nil, "", NewAppError(http.StatusBadRequest, "invalid_"+field, field+" must be a decimal number")
	}
	rat, ok := new(big.Rat).SetString(normalized)
	if !ok || rat.Sign() < 0 {
		return nil, "", NewAppError(http.StatusBadRequest, "invalid_"+field, field+" must be greater than or equal to 0")
	}
	return rat, normalized, nil
}

func normalizeDecimal(value string) (string, error) {
	value = strings.TrimSpace(value)
	if value == "" {
		return "", fmt.Errorf("blank decimal")
	}
	rat, ok := new(big.Rat).SetString(value)
	if !ok {
		return "", fmt.Errorf("invalid decimal")
	}
	return trimDecimalZeros(rat.FloatString(8)), nil
}

func trimDecimalZeros(value string) string {
	value = strings.TrimSpace(value)
	if !strings.Contains(value, ".") {
		return value
	}
	value = strings.TrimRight(value, "0")
	value = strings.TrimRight(value, ".")
	if value == "" || value == "-0" {
		return "0"
	}
	return value
}

func decimalEqual(left string, right string) bool {
	leftRat, ok := new(big.Rat).SetString(strings.TrimSpace(left))
	if !ok {
		return false
	}
	rightRat, ok := new(big.Rat).SetString(strings.TrimSpace(right))
	if !ok {
		return false
	}
	return leftRat.Cmp(rightRat) == 0
}

func calculateGold(amount *big.Rat, rate *big.Rat) (int64, error) {
	product := new(big.Rat).Mul(amount, rate)
	gold := new(big.Int).Quo(product.Num(), product.Denom())
	if !gold.IsInt64() {
		return 0, NewAppError(http.StatusBadRequest, "gold_amount_too_large", "gold amount is too large")
	}
	return gold.Int64(), nil
}