step3/api/QuestionsApi/Models/FlashcardModels.cs

using MongoDB.Bson;
using MongoDB.Bson.Serialization.Attributes;

namespace QuestionsApi.Models;

public static class FlashcardTypes
{
    public const string Basic = "basic";
    public const string Cloze = "cloze";
    public static readonly HashSet<string> All = [Basic, Cloze];
}

// A reserved, never-authenticatable owner id. Decks/notes owned by this id are shared,
// admin-curated content visible to every user (studied via their own independent schedule
// rows) rather than a real user's private content.
public static class FlashcardOwners
{
    public const string System = "system";
}

public static class FlashcardRatings
{
    public const string Again = "again";
    public const string Hard = "hard";
    public const string Good = "good";
    public const string Easy = "easy";
    public static readonly string[] All = [Again, Hard, Good, Easy];
}

public static class FlashcardScheduleStates
{
    public const string New = "new";
    public const string Learning = "learning";
    public const string Review = "review";
    public const string Relearning = "relearning";
}

public sealed class FlashcardDeck
{
    [BsonId, BsonRepresentation(BsonType.ObjectId)] public string? Id { get; set; }
    public string UserId { get; set; } = "";
    public string StableId { get; set; } = Guid.NewGuid().ToString();
    public string Name { get; set; } = "";
    public string NormalizedName { get; set; } = "";
    public string Description { get; set; } = "";
    public bool IsDefault { get; set; }
    public int? NewCardsPerDay { get; set; }
    public int? ReviewsPerDay { get; set; }
    public double? DesiredRetention { get; set; }
    public long Revision { get; set; } = 1;
    public DateTime CreatedUtc { get; set; } = DateTime.UtcNow;
    public DateTime UpdatedUtc { get; set; } = DateTime.UtcNow;
    public DateTime? ArchivedUtc { get; set; }
    [BsonIgnore] public bool IsSystem => UserId == FlashcardOwners.System;
}

public sealed class FlashcardImageReference
{
    public string Kind { get; set; } = "owned";
    public string AssetId { get; set; } = "";
}

public sealed class FlashcardNote
{
    [BsonId, BsonRepresentation(BsonType.ObjectId)] public string? Id { get; set; }
    public string UserId { get; set; } = "";
    public string StableId { get; set; } = Guid.NewGuid().ToString();
    public string DeckId { get; set; } = "";
    public string Type { get; set; } = FlashcardTypes.Basic;
    public string Prompt { get; set; } = "";
    public string Answer { get; set; } = "";
    public string Extra { get; set; } = "";
    public List<string> Tags { get; set; } = [];
    public List<FlashcardImageReference> Images { get; set; } = [];
    public string SourceQuestionExternalId { get; set; } = "";
    public string ContentFingerprint { get; set; } = "";
    public long Revision { get; set; } = 1;
    public DateTime CreatedUtc { get; set; } = DateTime.UtcNow;
    public DateTime UpdatedUtc { get; set; } = DateTime.UtcNow;
    public DateTime? ArchivedUtc { get; set; }
    [BsonIgnore] public bool IsSystem => UserId == FlashcardOwners.System;
}

public sealed class FlashcardSchedule
{
    [BsonId, BsonRepresentation(BsonType.ObjectId)] public string? Id { get; set; }
    public string UserId { get; set; } = "";
    public string NoteId { get; set; } = "";
    public int Variant { get; set; }
    public string State { get; set; } = FlashcardScheduleStates.New;
    public int? Step { get; set; }
    public double? Stability { get; set; }
    public double? Difficulty { get; set; }
    public DateTime DueUtc { get; set; } = DateTime.UtcNow;
    public DateTime? LastReviewUtc { get; set; }
    public DateTime? BuriedUntilUtc { get; set; }
    public bool IsSuspended { get; set; }
    public long Revision { get; set; } = 1;
    public string AlgorithmVersion { get; set; } = "fsrs-core-1.0.7";
    public DateTime CreatedUtc { get; set; } = DateTime.UtcNow;
}

public sealed class FlashcardReviewLog
{
    [BsonId] public string Id { get; set; } = "";
    public string UserId { get; set; } = "";
    public string CardId { get; set; } = "";
    public string Rating { get; set; } = "";
    public DateTime ReviewedUtc { get; set; }
    public int DurationSeconds { get; set; }
    public FlashcardScheduleSnapshot Before { get; set; } = new();
    public FlashcardScheduleSnapshot After { get; set; } = new();
    public DateTime CreatedUtc { get; set; } = DateTime.UtcNow;
    public DateTime? UndoneUtc { get; set; }
}

public sealed class FlashcardScheduleSnapshot
{
    public string State { get; set; } = FlashcardScheduleStates.New;
    public int? Step { get; set; }
    public double? Stability { get; set; }
    public double? Difficulty { get; set; }
    public DateTime DueUtc { get; set; }
    public DateTime? LastReviewUtc { get; set; }
    public long Revision { get; set; }
}

public sealed class FlashcardMediaAsset
{
    [BsonId, BsonRepresentation(BsonType.ObjectId)] public string? Id { get; set; }
    public string UserId { get; set; } = "";
    public string FileName { get; set; } = "";
    public string ContentType { get; set; } = "";
    public byte[] Bytes { get; set; } = [];
    public DateTime CreatedUtc { get; set; } = DateTime.UtcNow;
}

public sealed class FlashcardSettings
{
    [BsonId, BsonRepresentation(BsonType.ObjectId)] public string? Id { get; set; }
    public string UserId { get; set; } = "";
    public int NewCardsPerDay { get; set; } = 20;
    public int ReviewsPerDay { get; set; } = 200;
    public double DesiredRetention { get; set; } = 0.90;
    public long Revision { get; set; } = 1;
    public DateTime UpdatedUtc { get; set; } = DateTime.UtcNow;
}

public sealed class UpsertFlashcardDeckRequest
{
    public string Name { get; set; } = "";
    public string Description { get; set; } = "";
    public int? NewCardsPerDay { get; set; }
    public int? ReviewsPerDay { get; set; }
    public double? DesiredRetention { get; set; }
    public long? ExpectedRevision { get; set; }
}

public sealed class UpsertFlashcardNoteRequest
{
    public string DeckId { get; set; } = "";
    public string StableId { get; set; } = "";
    public string Type { get; set; } = FlashcardTypes.Basic;
    public string Prompt { get; set; } = "";
    public string Answer { get; set; } = "";
    public string Extra { get; set; } = "";
    public List<string> Tags { get; set; } = [];
    public List<FlashcardImageReference> Images { get; set; } = [];
    public string SourceQuestionExternalId { get; set; } = "";
    public long? ExpectedRevision { get; set; }
}

public sealed class UpdateFlashcardSettingsRequest
{
    public int NewCardsPerDay { get; set; } = 20;
    public int ReviewsPerDay { get; set; } = 200;
    public double DesiredRetention { get; set; } = 0.90;
    public long? ExpectedRevision { get; set; }
}

public sealed class FlashcardDeckSummary
{
    public FlashcardDeck Deck { get; set; } = new();
    public int Total { get; set; }
    public int Due { get; set; }
    public int New { get; set; }
    public int Suspended { get; set; }
    public int Learning { get; set; }
    public int Review { get; set; }
    public int Mastered { get; set; }
}

public sealed class FlashcardLibraryResponse
{
    public List<FlashcardNote> Items { get; set; } = [];
    public int Total { get; set; }
}

public sealed class FlashcardLibraryQuery
{
    public string? DeckId { get; set; }
    public string? Tag { get; set; }
    public string? Type { get; set; }
    public string? State { get; set; }
    public string? Search { get; set; }
    public int Page { get; set; } = 1;
    public int PageSize { get; set; } = 50;
}

public sealed class FlashcardStudyRequest
{
    public string DeckId { get; set; } = "";
    public List<string> ExcludeCardIds { get; set; } = [];
    public DateTime StudyDayStartUtc { get; set; } = DateTime.UtcNow.Date;
    public bool Shuffle { get; set; }
}

public sealed class FlashcardBulkNoteIdsRequest
{
    public List<string> NoteIds { get; set; } = [];
}

public sealed class FlashcardMoveRequest
{
    public List<string> NoteIds { get; set; } = [];
    public string TargetDeckId { get; set; } = "";
}

public sealed class FlashcardBatchReviewRequest
{
    public List<FlashcardReviewRequest> Reviews { get; set; } = [];
}

public sealed class FlashcardBatchReviewResponse
{
    public List<FlashcardReviewResponse> Results { get; set; } = [];
}

public sealed class FlashcardUndoRequest
{
    public string ReviewLogId { get; set; } = "";
}

public sealed class FlashcardRatingOption
{
    public string Rating { get; set; } = "";
    public string IntervalLabel { get; set; } = "";
    public DateTime DueUtc { get; set; }
}

public sealed class FlashcardStudyCardResponse
{
    public FlashcardNote? Note { get; set; }
    public FlashcardSchedule? Card { get; set; }
    public List<FlashcardRatingOption> RatingOptions { get; set; } = [];
    public int DueRemaining { get; set; }
    public int NewRemaining { get; set; }
}

public sealed class FlashcardReviewRequest
{
    public string ClientReviewId { get; set; } = "";
    public string CardId { get; set; } = "";
    public string Rating { get; set; } = "";
    public long ExpectedRevision { get; set; }
    public DateTime ReviewedUtc { get; set; }
    public int DurationSeconds { get; set; }
    public DateTime StudyDayStartUtc { get; set; } = DateTime.UtcNow.Date;
}

public sealed class FlashcardReviewResponse
{
    public FlashcardSchedule Card { get; set; } = new();
    public List<FlashcardRatingOption> RatingOptions { get; set; } = [];
    public bool Duplicate { get; set; }
}

public sealed class FlashcardDashboardCounts
{
    public int Due { get; set; }
    public int NewAvailable { get; set; }
    public int ReviewedThisWeek { get; set; }
    public int Learning { get; set; }
    public int Review { get; set; }
    public int CurrentStreakDays { get; set; }
    public int ReviewsToday { get; set; }
    public int DailyGoal { get; set; }
}

public static class FlashcardImportFormats
{
    public const string Csv = "csv";
    public const string Json = "json";
}

public static class FlashcardImportRowActions
{
    public const string Create = "create";
    public const string Update = "update";
    public const string Skip = "skip";
    public const string Error = "error";
}

public sealed class FlashcardImportPendingRecord
{
    public int RowNumber { get; set; }
    public string Action { get; set; } = FlashcardImportRowActions.Create;
    public string? Error { get; set; }
    public string StableId { get; set; } = "";
    public string DeckName { get; set; } = "";
    public string Type { get; set; } = FlashcardTypes.Basic;
    public string Prompt { get; set; } = "";
    public string Answer { get; set; } = "";
    public string Extra { get; set; } = "";
    public List<string> Tags { get; set; } = [];
    public string SourceQuestionExternalId { get; set; } = "";
    public List<FlashcardSchedule> Cards { get; set; } = [];
    public List<FlashcardReviewLog> ReviewLogs { get; set; } = [];
}

public sealed class FlashcardImportPreview
{
    [BsonId] public string Id { get; set; } = "";
    public string UserId { get; set; } = "";
    public string Format { get; set; } = FlashcardImportFormats.Csv;
    public List<FlashcardImportPendingRecord> Records { get; set; } = [];
    public DateTime CreatedUtc { get; set; } = DateTime.UtcNow;
    public DateTime ExpiresUtc { get; set; } = DateTime.UtcNow.AddHours(1);
}

public sealed class FlashcardImportPreviewRow
{
    public int RowNumber { get; set; }
    public string Action { get; set; } = FlashcardImportRowActions.Create;
    public string? Error { get; set; }
    public string StableId { get; set; } = "";
    public string Deck { get; set; } = "";
    public string Type { get; set; } = FlashcardTypes.Basic;
    public string Prompt { get; set; } = "";
    public string Answer { get; set; } = "";
}

public sealed class FlashcardImportPreviewResponse
{
    public string ImportToken { get; set; } = "";
    public int CreateCount { get; set; }
    public int UpdateCount { get; set; }
    public int SkipCount { get; set; }
    public int ErrorCount { get; set; }
    public List<FlashcardImportPreviewRow> Rows { get; set; } = [];
}

public sealed class FlashcardImportCommitRequest
{
    public string ImportToken { get; set; } = "";
}

public sealed class FlashcardImportCommitResponse
{
    public int Created { get; set; }
    public int Updated { get; set; }
    public int Skipped { get; set; }
    public int Errored { get; set; }
    public List<FlashcardImportPreviewRow> Errors { get; set; } = [];
}

public sealed class FlashcardExportOmission
{
    public string Kind { get; set; } = "";
    public string Reason { get; set; } = "";
}

public sealed class FlashcardJsonExport
{
    public int SchemaVersion { get; set; } = 1;
    public DateTime ExportedUtc { get; set; } = DateTime.UtcNow;
    public FlashcardSettings Settings { get; set; } = new();
    public List<FlashcardDeck> Decks { get; set; } = [];
    public List<FlashcardJsonExportNote> Notes { get; set; } = [];
}

public sealed class FlashcardJsonExportNote
{
    public FlashcardNote Note { get; set; } = new();
    public List<FlashcardSchedule> Cards { get; set; } = [];
    public List<FlashcardReviewLog> ReviewLogs { get; set; } = [];
    public List<FlashcardJsonExportImage> Images { get; set; } = [];
}

public sealed class FlashcardJsonExportImage
{
    public string AssetId { get; set; } = "";
    public string FileName { get; set; } = "";
    public string ContentType { get; set; } = "";
    public string Base64Bytes { get; set; } = "";
}