using System.Threading;
using BigRegister.Api.Data;
using BigRegister.Domain.Applications;

namespace BigRegister.Tests.Builders;

/// <summary>Fixture identities test builders share across the suite.</summary>
public static class TestIdentities
{
  /// The default owner for a builder-made <see cref="Aanvraag"/> — matches
  /// <see cref="DocumentStore.DemoOwner"/> (the demo's only seeded user) so a fixture that
  /// doesn't care about identity gets a realistic, elfproef-valid BSN for free.
  public const string DemoBsn = DocumentStore.DemoOwner;
}

/// <summary>
/// Type-state test-data builder for <see cref="Aanvraag"/>. "Build
/// test data through the same door production code uses" — <see cref="Aanvraag"/> itself is now
/// the closed Concept/Submitted/Decided union, so this builder no longer needs
/// to mirror production's guards (step-index bounds, "Afwijzen needs a toelichting") by hand —
/// it just calls the real nested constructors/required members, which enforce them. A call that
/// would build an illegal Aanvraag (e.g. deciding a still-Concept aanvraag, or an Afwijzen with
/// no toelichting) is refused the same way production refuses it: a still-Concept aanvraag has
/// no <c>.Decided(...)</c> to call in the first place, and a missing toelichting is a runtime
/// guard identical to <c>ApplicationStore.RecordBesluit</c>'s own. Start at
/// <see cref="Given.Concept"/>.
/// </summary>
public static class Given
{
  /// A fresh, unsubmitted wizard draft — step 0 of 0 until <see cref="ConceptAanvraag.AtStep"/>
  /// says otherwise, exactly what <c>ApplicationStore.CreateConcept</c> hands back.
  public static ConceptAanvraag Concept(string type = "registratie", string owner = TestIdentities.DemoBsn) =>
      new(type, owner);
}

/// <summary>A not-yet-submitted aanvraag. The only next step is <see cref="Submitted"/> — there
/// is deliberately no <c>Decided</c> here, since only a submitted aanvraag can be decided.</summary>
public sealed class ConceptAanvraag
{
  private readonly string _type;
  private readonly string _owner;
  private int _stepIndex;
  private int _stepCount;

  internal ConceptAanvraag(string type, string owner)
  {
    _type = type;
    _owner = owner;
  }

  /// The wizard's current position — step <paramref name="index"/> of <paramref name="of"/>.
  /// Bounds are <see cref="Aanvraag.Concept"/>'s OWN constructor's to enforce, not this
  /// builder's — an out-of-range pair fails at <see cref="Build"/>, the same
  /// <see cref="ArgumentOutOfRangeException"/> production throws, not a guard restated here.
  public ConceptAanvraag AtStep(int index, int of)
  {
    _stepIndex = index;
    _stepCount = of;
    return this;
  }

  /// Submits the draft — always assigns a Referentie AND SubmittedAt together (mirrors
  /// <c>ApplicationStore.Submit</c>), so a fixture built this way can never hit the
  /// null-forgiving derefs the earlier flat Aanvraag needed (there's nothing to force any
  /// more: both are required, non-null members of <see cref="Aanvraag.Submitted"/>).
  public SubmittedAanvraag Submitted(bool autoApprovable = false) => new(_type, _owner, autoApprovable);

  public Aanvraag.Concept Build() => new(_stepIndex, _stepCount)
  {
    Id = Guid.NewGuid().ToString(),
    Type = _type,
    Owner = _owner,
    DocumentIds = Array.Empty<string>(),
    CreatedAt = DateTimeOffset.UtcNow,
    UpdatedAt = DateTimeOffset.UtcNow,
  };
}

/// <summary>A submitted aanvraag, open for a behandelaar's decision. The only next step is
/// <see cref="Decided"/> — there is no way back to <see cref="ConceptAanvraag"/>.</summary>
public sealed class SubmittedAanvraag
{
  private static int _referentieSeq;

  private readonly string _type;
  private readonly string _owner;
  private readonly bool _autoApprovable;
  private readonly string _referentie;
  private readonly DateTimeOffset _submittedAt;
  private string? _zaakUrl;

  internal SubmittedAanvraag(string type, string owner, bool autoApprovable)
  {
    _type = type;
    _owner = owner;
    _autoApprovable = autoApprovable;
    // A plausible reference in SubmissionRules.NewReference's shape ("BIG-2026-" + a number) —
    // sequential (not random) so a fixture's value is reproducible across a test run.
    _referentie = $"BIG-2026-{Interlocked.Increment(ref _referentieSeq)}";
    _submittedAt = DateTimeOffset.UtcNow;
  }

  /// <summary>Registers this aanvraag's already-known OpenZaak zaak URL — mirrors
  /// <see cref="ApplicationStore.SetZaakUrl"/>, the one production writer of this field, so a
  /// fixture that needs a pre-existing zaak doesn't reach past <c>Build()</c> to mutate the
  /// result by hand.</summary>
  public SubmittedAanvraag WithZaakUrl(string zaakUrl)
  {
    _zaakUrl = zaakUrl;
    return this;
  }

  /// <summary>Records a behandelaar's decision. Unlike the earlier builder, there is no
  /// hand-written toelichting guard mirroring <c>BeoordelingRules.RequiresToelichting</c> any
  /// more — <see cref="Aanvraag.Decided.Afgewezen"/>/<see cref="Aanvraag.Decided.MeerInfoGevraagd"/>
  /// simply have a `required string Toelichting` member; the null-coalescing throw below is the
  /// one place a null has to turn into an exception (this method's own parameter is still the
  /// nullable <c>string?</c> a wire request would carry), same failure production's own
  /// <c>ApplicationStore.RecordBesluit</c> raises for the identical input.</summary>
  public DecidedAanvraag Decided(Besluit besluit, string? toelichting = null) => new(BuildDecided(besluit, toelichting));

  private Aanvraag.Decided BuildDecided(Besluit besluit, string? toelichting)
  {
    var (id, createdAt) = (Guid.NewGuid().ToString(), _submittedAt);
    return besluit switch
    {
      Besluit.Goedkeuren => new Aanvraag.Decided.Goedgekeurd
      {
        Id = id,
        Type = _type,
        Owner = _owner,
        DocumentIds = Array.Empty<string>(),
        CreatedAt = createdAt,
        UpdatedAt = createdAt,
        ZaakUrl = _zaakUrl,
        Referentie = _referentie,
        SubmittedAt = _submittedAt,
      },
      Besluit.Afwijzen => new Aanvraag.Decided.Afgewezen
      {
        Id = id,
        Type = _type,
        Owner = _owner,
        DocumentIds = Array.Empty<string>(),
        CreatedAt = createdAt,
        UpdatedAt = createdAt,
        ZaakUrl = _zaakUrl,
        Referentie = _referentie,
        SubmittedAt = _submittedAt,
        Toelichting = toelichting ?? throw new ArgumentException("Afwijzen requires a toelichting.", nameof(toelichting)),
      },
      Besluit.MeerInfoOpvragen => new Aanvraag.Decided.MeerInfoGevraagd
      {
        Id = id,
        Type = _type,
        Owner = _owner,
        DocumentIds = Array.Empty<string>(),
        CreatedAt = createdAt,
        UpdatedAt = createdAt,
        ZaakUrl = _zaakUrl,
        Referentie = _referentie,
        SubmittedAt = _submittedAt,
        Toelichting = toelichting ?? throw new ArgumentException("MeerInfoOpvragen requires a toelichting.", nameof(toelichting)),
      },
      _ => throw new ArgumentOutOfRangeException(nameof(besluit), besluit, "Unknown besluit."),
    };
  }

  public Aanvraag.Submitted Build() => new()
  {
    Id = Guid.NewGuid().ToString(),
    Type = _type,
    Owner = _owner,
    DocumentIds = Array.Empty<string>(),
    CreatedAt = _submittedAt,
    UpdatedAt = _submittedAt,
    ZaakUrl = _zaakUrl,
    Referentie = _referentie,
    SubmittedAt = _submittedAt,
    AutoApprovable = _autoApprovable,
  };
}

/// <summary>A submitted aanvraag with a behandelaar's decision already recorded — terminal in
/// the builder too, matching Goedgekeurd/Afgewezen being terminal in the domain
/// (<see cref="BigRegister.Domain.Beoordeling.BeoordelingRules.CanDecide"/>); a fixture that
/// needs a SECOND besluit (the MeerInfoGevraagd "still decidable" case) builds fresh from
/// <see cref="Given.Concept"/> again, exactly as a real second request would. Just a one-line
/// wrapper around the already-fully-built <see cref="Aanvraag.Decided"/> value — construction moved
/// all the actual construction (and its invariant enforcement) into
/// <see cref="SubmittedAanvraag.Decided"/> itself, so there's nothing left for this type to do
/// except keep <c>.Decided(...).Build()</c> a valid two-call chain for the existing test
/// suite.</summary>
public sealed class DecidedAanvraag(Aanvraag.Decided value)
{
  public Aanvraag.Decided Build() => value;
}