package lib

import (
	"strconv"
	"strings"
)

// ParseNumeric parses a numeric string that may use comma or period as
// decimal or thousands separator. Returns the float value and true on success.
//
// Rules:
//  1. Both comma and period → last one is decimal separator
//  2. Only one separator type → count digits after last occurrence:
//     - 3 digits → ambiguous → hint decides (default: thousands)
//     - other → decimal separator
//  3. No separators → plain integer
//
// Hint: locale like "en", "de", "nl". Empty = default (comma=thousands).
func ParseNumeric(s string, hint string) (float64, bool) {
	s = strings.TrimSpace(s)
	if s == "" {
		return 0, false
	}
	s = strings.TrimPrefix(s, "+")

	hasComma := strings.Contains(s, ",")
	hasPeriod := strings.Contains(s, ".")

	switch {
	case hasComma && hasPeriod:
		// Last separator is the decimal one
		if strings.LastIndex(s, ",") > strings.LastIndex(s, ".") {
			// "1.234,56" → comma is decimal
			s = strings.ReplaceAll(s, ".", "")
			s = strings.Replace(s, ",", ".", 1)
		} else {
			// "1,234.56" → period is decimal
			s = strings.ReplaceAll(s, ",", "")
		}

	case hasComma:
		last := strings.LastIndex(s, ",")
		after := s[last+1:]
		if len(after) == 3 && commaIsThousands(hint) {
			// "1,234" in en context → thousands
			s = strings.ReplaceAll(s, ",", "")
		} else {
			// "12,5" or "1,23" → decimal
			s = strings.ReplaceAll(s, ",", ".")
		}

	case hasPeriod:
		last := strings.LastIndex(s, ".")
		after := s[last+1:]
		if len(after) == 3 && !commaIsThousands(hint) {
			// "1.234" in de context → thousands
			s = strings.ReplaceAll(s, ".", "")
		}
		// else: period is decimal (default), leave as-is
	}

	v, err := strconv.ParseFloat(s, 64)
	return v, err == nil
}

// commaIsThousands returns true if comma is used as thousands separator
// in the given locale (English convention). False for European convention.
func commaIsThousands(hint string) bool {
	switch strings.ToLower(hint) {
	case "de", "nl", "fr", "es", "it", "pt", "ru", "tr", "pl", "cs", "da", "sv", "nb", "fi":
		return false
	default:
		return true // en, en-us, en-gb, ja, zh, ko, "" (default)
	}
}