using System.ComponentModel.DataAnnotations;
using System.Globalization;
using System.Text.RegularExpressions;

namespace QRPay.Models;

public class PaymentRequest : IValidatableObject
{
    private static readonly Regex IbanRegex = new(
        "^[A-Z]{2}[0-9]{2}[A-Z0-9]{4}[0-9]{7}([A-Z0-9]?){0,16}$",
        RegexOptions.Compiled);

    [StringLength(70, ErrorMessage = "Name cannot exceed 70 characters")]
    public string Name { get; set; } = string.Empty;

    [Required(ErrorMessage = "IBAN is required")]
    public string IBAN { get; set; } = string.Empty;

    [Required(ErrorMessage = "Amount is required")]
    [Range(typeof(decimal), "0.01", "999999.99", ErrorMessage = "Amount must be between €0.01 and €999,999.99")]
    public decimal? Amount { get; set; }

    [StringLength(140, ErrorMessage = "Remark cannot exceed 140 characters")]
    public string Remark { get; set; } = string.Empty;

    public string NormalizedIBAN => NormalizeIban(IBAN);

    public static string NormalizeIban(string? iban)
    {
        return string.IsNullOrWhiteSpace(iban)
            ? string.Empty
            : iban.Replace(" ", string.Empty, StringComparison.Ordinal).ToUpperInvariant();
    }

    public IReadOnlyList<string> ValidateForQrRoute()
    {
        var errors = new List<string>();
        var normalizedIban = NormalizedIBAN;

        if (string.IsNullOrWhiteSpace(normalizedIban))
        {
            errors.Add("Missing required query parameter: iban.");
        }
        else if (!IbanRegex.IsMatch(normalizedIban))
        {
            errors.Add("Invalid IBAN format.");
        }

        if (Amount is null)
        {
            errors.Add("Missing required query parameter: amount.");
        }
        else if (Amount < 0.01m || Amount > 999999.99m)
        {
            errors.Add("Amount must be between 0.01 and 999999.99 EUR.");
        }

        if (!string.IsNullOrEmpty(Name) && Name.Length > 70)
        {
            errors.Add("Name cannot exceed 70 characters.");
        }

        if (!string.IsNullOrEmpty(Remark) && Remark.Length > 140)
        {
            errors.Add("Remark cannot exceed 140 characters.");
        }

        return errors;
    }

    public static bool TryParseAmount(string? value, out decimal amount)
    {
        return decimal.TryParse(
            value,
            NumberStyles.Number,
            CultureInfo.InvariantCulture,
            out amount);
    }

    public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
    {
        if (!string.IsNullOrWhiteSpace(IBAN) && !IbanRegex.IsMatch(NormalizedIBAN))
        {
            yield return new ValidationResult(
                "Please enter a valid IBAN",
                [nameof(IBAN)]);
        }
    }
}