using System.Globalization;
using System.Text.RegularExpressions;
using GeradoresService.Core;

namespace GeradoresService.Generators.Financeiro;

/// <summary>
/// Referência Multibanco: entidade (5) + referência (9) + montante.
/// Os 2 últimos dígitos da referência são controlo: 98 - (Σ dígito × peso mod 97),
/// calculado sobre entidade(5) + referência(7) + montante em cêntimos(8).
/// </summary>
public sealed partial class ReferenciaMultibancoGenerator : GeneratorBase
{
    private static readonly int[] Weights = [51, 73, 17, 89, 38, 62, 45, 53, 15, 50, 5, 49, 34, 81, 76, 27, 90, 9, 30, 3];

    public override string Id => "multibanco";
    public override string Name => "Referência Multibanco";
    public override string Category => Categories.Financeiro;
    public override string Description => "Entidade, referência e montante com dígitos de controlo válidos.";

    public override GeneratedItem Generate(GeneratorContext context)
    {
        var entity = (10000 + context.Random.Next(90000)).ToString();
        var cents = 100 + context.Random.Next(50000);
        var reference = context.Digits(7);
        reference += CheckDigits(entity, reference, cents);

        var amount = (cents / 100m).ToString("0.00", CultureInfo.InvariantCulture);
        return new GeneratedItem($"{entity} {FormatReference(reference)} {amount}", new Dictionary<string, string>
        {
            ["Entidade"] = entity,
            ["Referência"] = FormatReference(reference),
            ["Montante"] = $"{amount} €",
        });
    }

    public static string CheckDigits(string entity, string reference7, long cents)
    {
        var chk = entity + reference7 + cents.ToString("D8");
        var sum = 0;
        for (var i = 0; i < 20; i++)
            sum += (chk[i] - '0') * Weights[i];
        return (98 - sum % 97).ToString("D2");
    }

    private static string FormatReference(string r) => $"{r[..3]} {r[3..6]} {r[6..]}";

    public override ValidationResult Validate(string value)
    {
        var m = Pattern().Match(value.Trim());
        if (!m.Success)
            return ValidationResult.WrongFormat("Formato esperado: entidade (5 dígitos), referência (9 dígitos) e montante, ex.: 12345 123 456 789 10.00");

        var entity = m.Groups["ent"].Value;
        var reference = Checksums.Clean(m.Groups["ref"].Value);
        var amount = decimal.Parse(m.Groups["val"].Value.Replace(',', '.'), CultureInfo.InvariantCulture);
        var cents = (long)Math.Round(amount * 100);
        if (cents > 99_999_999)
            return ValidationResult.WrongFormat("Montante demasiado elevado.");

        var expected = CheckDigits(entity, reference[..7], cents);
        var details = new List<string>
        {
            $"Entidade: {entity}",
            $"Montante: {amount.ToString("0.00", CultureInfo.InvariantCulture)} €",
            $"Dígitos de controlo esperados: {expected}",
        };
        return reference[7..] == expected
            ? ValidationResult.Valid($"{entity} {FormatReference(reference)} {amount.ToString("0.00", CultureInfo.InvariantCulture)}", "Referência Multibanco válida.", details)
            : ValidationResult.BadChecksum($"Dígitos de controlo inválidos: esperado {expected}, encontrado {reference[7..]}.", details);
    }

    [GeneratedRegex(@"^(?<ent>\d{5})[\s|;]+(?<ref>\d{3}\s?\d{3}\s?\d{3})[\s|;]+(?<val>\d{1,6}(?:[.,]\d{1,2})?)\s*€?$")]
    private static partial Regex Pattern();
}