namespace OpenNest.Data;

/// <summary>
/// One bounded page request for browsing saved nests (<c>GET /api/nests/query</c>).
/// The server filters and pages in SQL; the client and server share these bounds.
/// </summary>
public sealed class NestQuery
{
    public const int DefaultLimit = 100;
    public const int MaxLimit = 500;
    public const int MaxSearchLength = 200;

    /// <summary>
    /// Case-insensitive substring matched against name, customer, material, grade, made by,
    /// comments and status (stored and display names). Blank means no filter.
    /// </summary>
    public string Search { get; init; } = "";

    /// <summary>Only nests in this status; null means any.</summary>
    public NestStatus? Status { get; init; }

    /// <summary>
    /// Only nests of this material name, compared by <see cref="SharedListNames.Key"/>
    /// (case and spacing ignored); null means any.
    /// </summary>
    public string? Material { get; init; }

    /// <summary>
    /// Only nests of this grade, compared like <see cref="Material"/>; null means any and
    /// blank means nests with no grade recorded.
    /// </summary>
    public string? MaterialGrade { get; init; }

    /// <summary>Only nests of this thickness, compared at four decimals; null means any.</summary>
    public double? Thickness { get; init; }

    /// <summary>Column to order by; ties are broken by id in the same direction.</summary>
    public NestSortField Sort { get; init; } = NestSortField.SavedAt;

    /// <summary>Largest/newest/Z first when true (the default, newest saved first).</summary>
    public bool Descending { get; init; } = true;

    /// <summary>Number of matching records to skip, zero or greater.</summary>
    public int Offset { get; init; }

    /// <summary>Maximum records returned, 1 to <see cref="MaxLimit"/>.</summary>
    public int Limit { get; init; } = DefaultLimit;

    /// <summary>The search text as matched: trimmed, never null.</summary>
    public string NormalizedSearch => (Search ?? "").Trim();

    /// <summary>The first violated bound, or null when the query may be sent.</summary>
    public string? GetValidationError()
    {
        if (!Enum.IsDefined(Sort))
            return "sort must be a supported column.";
        if (Offset < 0)
            return "offset must be zero or greater.";
        if (Limit < 1 || Limit > MaxLimit)
            return $"limit must be between 1 and {MaxLimit}.";
        if (NormalizedSearch.Length > MaxSearchLength)
            return $"search must be at most {MaxSearchLength} characters.";
        // SQLite LIKE stops at an embedded NUL, which would turn the rest of the text into a wildcard.
        if (NormalizedSearch.Contains('\0'))
            return "search must not contain NUL characters.";
        if (Status is { } status && !Enum.IsDefined(status))
            return "status must be a supported status.";
        if (Thickness is { } thickness && (!double.IsFinite(thickness) || thickness < 0))
            return "thickness must be a finite number, zero or greater.";
        return (Material is null ? null : DrawingLibraryRules.TextError("material", Material, DrawingLibraryRules.MaxTextLength))
            ?? (MaterialGrade is null ? null : DrawingLibraryRules.TextError("materialGrade", MaterialGrade, DrawingLibraryRules.MaxTextLength));
    }
}