// Package money ports Czech-locale currency parsing from scripts/infer_payments.py.
package money

import (
	"errors"
	"strconv"
	"strings"
)

// ErrInvalidAmount is returned by ParseCZK when the input cannot be parsed.
var ErrInvalidAmount = errors.New("money: invalid CZK amount")

// ParseCZK parses a Czech-locale amount string and returns the value in CZK
// as a float64. Mirrors scripts/infer_payments.py parse_czk_amount:
//
//   - empty input → (0, nil)
//   - "Kč"/"CZK" suffixes stripped (case-sensitive, like Python)
//   - comma present → comma is decimal sep, dots/spaces are thousand seps
//     ("1.500,00" → 1500.0)
//   - no comma, 2+ dots → all dots are thousand seps ("1.500.000" → 1500000.0)
//   - no comma, ≤1 dot → dot is decimal sep ("1.500" → 1.5)
//   - on parse failure → (0, ErrInvalidAmount); callers wanting Python's
//     silent-zero behaviour can discard the error: v, _ := ParseCZK(s)
func ParseCZK(s string) (float64, error) {
	if s == "" {
		return 0, nil
	}

	s = strings.ReplaceAll(s, "Kč", "")
	s = strings.ReplaceAll(s, "CZK", "")
	s = strings.TrimSpace(s)

	if strings.ContainsRune(s, ',') {
		s = strings.ReplaceAll(s, ".", "")
		s = strings.ReplaceAll(s, " ", "")
		s = strings.ReplaceAll(s, ",", ".")
	} else if strings.Count(s, ".") > 1 {
		s = strings.ReplaceAll(s, ".", "")
		s = strings.ReplaceAll(s, " ", "")
	} else {
		s = strings.ReplaceAll(s, " ", "")
	}

	v, err := strconv.ParseFloat(s, 64)
	if err != nil {
		return 0, ErrInvalidAmount
	}
	return v, nil
}