namespace BigRegister.Domain.Documents;

/// <summary>
/// SERVER-OWNED document category config. The frontend renders these; it never
/// hardcodes file types, size limits, labels, required-ness or the post-delivery
/// flag. Adding a new category or changing a rule is a backend-only change.
/// </summary>
public sealed record DocumentCategory(
    string CategoryId,
    string Label,
    string Description,
    bool Required,
    IReadOnlyList<string> AcceptedTypes,
    int MaxSizeMb,
    bool Multiple,
    bool AllowPostDelivery);

public static class DocumentRules
{
    private static readonly string[] Pdf = { "application/pdf" };
    private static readonly string[] PdfImage = { "application/pdf", "image/jpeg", "image/png" };

    private static readonly DocumentCategory Diploma = new("diploma", "Diplomabewijs",
        "Upload uw diploma als PDF-bestand.", true, Pdf, 10, false, false);
    private static readonly DocumentCategory Identiteit = new("identiteit", "Identiteitsbewijs",
        "Upload een kopie van uw paspoort of ID-kaart.", true, PdfImage, 10, false, true);
    private static readonly DocumentCategory Taalvaardigheid = new("taalvaardigheid", "Bewijs Nederlandse taalvaardigheid",
        "Upload een bewijs van uw Nederlandse taalvaardigheid op het vereiste niveau (B2).", true, PdfImage, 10, false, true);

    /// <summary>
    /// The MAXIMAL set of categories a wizard can ever ask for. Used to validate an
    /// upload POST (any real category must resolve) — <see cref="CategoriesFor"/>
    /// decides which subset is actually presented for a given set of answers.
    /// </summary>
    public static IReadOnlyList<DocumentCategory> AllCategoriesFor(string wizardId) => wizardId switch
    {
        "registratie" => new[] { Diploma, Identiteit, Taalvaardigheid },
        "herregistratie" => new[]
        {
            new DocumentCategory("werkervaring", "Bewijs van werkervaring",
                "Upload bewijs van uw gewerkte uren (bijv. een werkgeversverklaring).", true, Pdf, 10, true, true),
            new DocumentCategory("nascholing", "Nascholingscertificaten",
                "Upload uw nascholingscertificaten (optioneel).", false, PdfImage, 10, true, true),
        },
        _ => Array.Empty<DocumentCategory>(),
    };

    /// <summary>
    /// The categories to PRESENT for a wizard, given the answers that affect required
    /// documents. RULES (registratie): a diploma upload is required ONLY for a manually
    /// entered diploma (a DUO diploma is verified digitally, and nothing is required
    /// before a diploma is chosen); proof of Dutch taalvaardigheid is required only when
    /// the applicant confirms ("ja") they meet the language requirement. Answer-agnostic
    /// wizards get their full set.
    /// </summary>
    public static IReadOnlyList<DocumentCategory> CategoriesFor(
        string wizardId, string? diplomaHerkomst = null, string? taalvaardigheid = null)
    {
        if (wizardId != "registratie") return AllCategoriesFor(wizardId);
        var result = new List<DocumentCategory>();
        if (diplomaHerkomst == "handmatig") result.Add(Diploma);
        result.Add(Identiteit);
        if (taalvaardigheid == "ja") result.Add(Taalvaardigheid);
        return result;
    }

    public static DocumentCategory? Find(string wizardId, string categoryId) =>
        AllCategoriesFor(wizardId).FirstOrDefault(c => c.CategoryId == categoryId);

    /// <summary>
    /// Authoritative upload validation (the client check is UX-only). Returns a
    /// rejection reason, or null when the file is acceptable.
    /// </summary>
    public static string? RejectUpload(DocumentCategory? category, string contentType, long sizeBytes)
    {
        if (category is null) return "Onbekende documentcategorie.";
        if (!category.AcceptedTypes.Contains(contentType))
            return $"Bestandstype niet toegestaan voor {category.Label}.";
        if (sizeBytes > (long)category.MaxSizeMb * 1024 * 1024)
            return $"Bestand is groter dan {category.MaxSizeMb} MB.";
        return null;
    }
}
