using MongoDB.Bson;
using MongoDB.Driver;
using QuestionsApi.Models;

namespace QuestionsApi.Services;

public sealed class UserProfileStore
{
    private readonly IMongoDatabase _database;
    private readonly IMongoCollection<UserStudyProfile> _profiles;
    private readonly IMongoCollection<DeletedUserTombstone> _deletedUsers;

    private static readonly string[] OwnedCollections =
    [
        "QuestionAttempts", "UserRatings", "QuestionBookmarks", "UserNotepads",
        "ReviewQueueItems", "QuestionReviewAttempts", "ReviewQueueBackfillStates",
        "DynamicQuestionAttempts", "DynamicObjectiveMastery", "DynamicReviewItems",
        "CcsAttempts", "CcsUserRatings", "CcsRatedCaseResults", "ExamSimulations",
        "Step3Outcomes", "QuestionReports", "CcsCaseReports", "AppFeedback", "UserStudyProfiles",
        "ExternalIdentities", "ExternalAuthTransactions",
        "FlashcardDecks", "FlashcardNotes", "FlashcardSchedules", "FlashcardReviewLogs",
        "FlashcardMediaAssets", "FlashcardSettings", "FlashcardImportPreviews",
        "UserCreditAccounts", "CreditLedgerEntries", "StudySessions", "DailyMissionSets", "WeeklyGoals"
    ];

    public UserProfileStore(MongoDatabaseProvider mongo)
    {
        _database = mongo.Database;
        _profiles = _database.GetCollection<UserStudyProfile>("UserStudyProfiles");
        _deletedUsers = _database.GetCollection<DeletedUserTombstone>("DeletedUserTombstones");
        _profiles.Indexes.CreateOne(new CreateIndexModel<UserStudyProfile>(
            Builders<UserStudyProfile>.IndexKeys.Ascending(value => value.UserId),
            new CreateIndexOptions { Unique = true }));
    }

    public async Task<UserStudyProfile?> GetAsync(string userId) =>
        await _profiles.Find(value => value.UserId == userId).FirstOrDefaultAsync();

    public async Task<UserStudyProfile> UpsertAsync(string userId, UpdateUserStudyProfileRequest request)
    {
        var update = Builders<UserStudyProfile>.Update
            .Set(value => value.TargetExamDate, request.TargetExamDate)
            .Set(value => value.PreparationStage, request.PreparationStage)
            .Set(value => value.WeeklyGoalHours, request.WeeklyGoalHours)
            .Set(value => value.PreferredStudyMode, request.PreferredStudyMode)
            .Set(value => value.UpdatedUtc, DateTime.UtcNow)
            .Inc(value => value.Revision, 1)
            .SetOnInsert(value => value.UserId, userId);
        return await _profiles.FindOneAndUpdateAsync(
            value => value.UserId == userId,
            update,
            new FindOneAndUpdateOptions<UserStudyProfile> { IsUpsert = true, ReturnDocument = ReturnDocument.After });
    }

    public async Task<UserStudyProfile> UpdateTextScaleAsync(string userId, UpdateTextScaleRequest request)
    {
        var update = Builders<UserStudyProfile>.Update.Set(value => value.UpdatedUtc, DateTime.UtcNow);
        if (request.QuestionTextScale is { } questionScale)
            update = update.Set(value => value.QuestionTextScale, questionScale);
        if (request.CcsTextScale is { } ccsScale)
            update = update.Set(value => value.CcsTextScale, ccsScale);
        update = update.SetOnInsert(value => value.UserId, userId);
        return await _profiles.FindOneAndUpdateAsync(
            value => value.UserId == userId,
            update,
            new FindOneAndUpdateOptions<UserStudyProfile> { IsUpsert = true, ReturnDocument = ReturnDocument.After });
    }

    public Task<bool> IsDeletedAsync(string userId) =>
        _deletedUsers.Find(value => value.UserId == userId).AnyAsync();

    public async Task<Dictionary<string, List<object?>>> ExportAsync(string userId)
    {
        var result = new Dictionary<string, List<object?>>(StringComparer.OrdinalIgnoreCase);
        foreach (var collectionName in OwnedCollections)
        {
            var documents = await _database.GetCollection<BsonDocument>(collectionName)
                .Find(Builders<BsonDocument>.Filter.Eq("UserId", userId)).ToListAsync();
            result[collectionName] = documents.Select(document => Map(document)).ToList();
        }
        return result;
    }

    public async Task PurgeAsync(string userId)
    {
        await _deletedUsers.ReplaceOneAsync(
            value => value.UserId == userId,
            new DeletedUserTombstone { UserId = userId, DeletedUtc = DateTime.UtcNow },
            new ReplaceOptions { IsUpsert = true });

        foreach (var collectionName in OwnedCollections)
        {
            await _database.GetCollection<BsonDocument>(collectionName)
                .DeleteManyAsync(Builders<BsonDocument>.Filter.Eq("UserId", userId));
        }

        foreach (var collectionName in new[] { "QuestionReports", "CcsCaseReports", "AppFeedback" })
        {
            await _database.GetCollection<BsonDocument>(collectionName).UpdateManyAsync(
                Builders<BsonDocument>.Filter.Eq("ReviewedByUserId", userId),
                Builders<BsonDocument>.Update.Unset("ReviewedByUserId"));
        }
    }

    private static object? Map(BsonValue value)
    {
        if (value.IsBsonNull) return null;
        if (value.IsBsonDocument)
            return value.AsBsonDocument.Elements.ToDictionary(element => element.Name, element => Map(element.Value));
        if (value.IsBsonArray) return value.AsBsonArray.Select(Map).ToList();
        if (value.IsObjectId) return value.AsObjectId.ToString();
        if (value.IsValidDateTime) return value.ToUniversalTime();
        if (value.IsDecimal128) return Decimal128.ToDecimal(value.AsDecimal128);
        if (value.IsBsonBinaryData) return Convert.ToBase64String(value.AsBsonBinaryData.Bytes);
        if (value.IsBsonRegularExpression) return value.AsBsonRegularExpression.ToString();
        return BsonTypeMapper.MapToDotNetValue(value);
    }
}