using GB5Shared.DTO.Ice;
using GB5Shared.DTO.Framework.Login;
using IceImportDAL.DTO.IceImportPipeline;

namespace IceImportBLL.Validators;

// Checks that every mandatory (IsOptional=1) ValueType 0/3/4/5 (Source/Expression/CodeToId/
// NameToId — the only types that read a real source column) IceMapDetails.SourceFieldName
// actually exists as a column somewhere in the parsed source data (legacy's CheckHeaderFieldsName).
// IsOptional=0 fields may legitimately be absent — the corresponding resolver falls back to
// IceMapDetailsOptionalFiledValue instead of erroring (see SourceValueResolver et al.).
// This is a header-level check, not a per-row one — guarded to run only once (on RowNumber==1) even
// though the pipeline invokes every IRowValidator per row; findings are tagged RowNumber=0 by
// convention to mark them as header-level rather than tied to a specific data row.
public class HeaderFieldExistenceValidator : IRowValidator
{
    public string Key => "HEADER_FIELD_EXISTENCE";

    private static readonly HashSet<short> SourceColumnValueTypes = new() { 0, 3, 4, 5 };

    public Task<List<IceImportFieldErrorDTO>> ValidateAsync(
        MappedEntityRowDTO row, IceMapDTO mapDefinition, ParsedImportDataSetDTO parsedData, LoginDTO login, CancellationToken ct)
    {
        var errors = new List<IceImportFieldErrorDTO>();
        if (row.RowNumber != 1) return Task.FromResult(errors);

        foreach (var detail in mapDefinition.IceMapDetailsArray)
        {
            if (!SourceColumnValueTypes.Contains(detail.IceMapDetailsValueType)) continue;
            if (detail.IceMapDetailsIsOptional == 0) continue;  // optional — falls back to OptionalFiledValue instead

            // Exclude ONLY the object/List container marker itself (e.g. the "EmployeeAddon" row) —
            // its SourceFieldName is a container label, never a real Excel column. Individual addon
            // fields (BONUSAPPL, INCAPPL, ...) commonly share ONE placeholder DestinationMemberId
            // whose MENTITYMEMBERS.DATATYPE is ALSO 5 (they don't map to a real typed POCO member),
            // so DestinationMemberDataType==5 alone cannot distinguish "the container" from "an addon
            // field routed through that same placeholder member" — IceMapDetailsAddonFields (only set
            // on real addon field rows, never on the container) is what actually distinguishes them.
            var isContainerMarker = detail.DestinationMemberDataType == 5 &&
                                     string.IsNullOrWhiteSpace(detail.IceMapDetailsAddonFields);
            if (isContainerMarker) continue;

            // Applies uniformly regardless of which entity group a detail row belongs to — including
            // Addon-designated fields (non-empty IceMapDetailsAddonFields, e.g. BONUSAPPL/INCAPPL,
            // grouped under the AddonEntityId sentinel): this check is keyed off ValueType/IsOptional/
            // SourceFieldName directly against the parsed file, never filtered by entity.
            var fieldName = detail.IceMapDetailsSourceFieldName?.Trim().ToUpperInvariant();
            if (string.IsNullOrEmpty(fieldName)) continue;

            var found = parsedData.Tables.Values.Any(t => t.Columns.Contains(fieldName));
            if (found) continue;

            errors.Add(new IceImportFieldErrorDTO
            {
                RowNumber = 0,
                EntityCode = detail.EntityCode ?? string.Empty,
                FieldName = detail.DestinationMemberMemberName ?? fieldName,
                Message = $"Required source column '{fieldName}' was not found in the uploaded file.",
                Severity = IceImportSeverity.Error
            });
        }

        return Task.FromResult(errors);
    }
}