using System.Data;
using System.Data.Common;
using Domain.Entities;
using Infrastructure.Sql;
using Microsoft.Data.SqlClient;

namespace Features.Auth.Repository;

/// <summary>
/// ADO.NET-based implementation of <see cref="IAuthRepository"/> backed by SQL Server stored procedures,
/// handling user registration, credential lookup/rotation, and account verification.
/// </summary>
/// <param name="connectionFactory">The factory used to create database connections.</param>
public class AuthRepository(ISqlConnectionFactory connectionFactory)
    : Infrastructure.Sql.Repository<Domain.Entities.UserAccount>(connectionFactory),
        IAuthRepository
{
    /// <summary>
    /// Registers a new user account and initial credential using the <c>USP_RegisterUser</c> stored
    /// procedure, then fetches and returns the newly created user.
    /// </summary>
    /// <remarks>
    /// The stored procedure's scalar result (expected to be the new user's ID) is parsed defensively:
    /// it may be returned as a <see cref="Guid"/>, a parseable <see cref="string"/>, or a 16-byte array.
    /// If the result cannot be interpreted, <see cref="Guid.Empty"/> is used, which will cause the
    /// subsequent lookup to fail.
    /// </remarks>
    /// <param name="username">Unique username for the user</param>
    /// <param name="firstName">User's first name</param>
    /// <param name="lastName">User's last name</param>
    /// <param name="email">User's email address</param>
    /// <param name="dateOfBirth">User's date of birth</param>
    /// <param name="passwordHash">Hashed password</param>
    /// <returns>The newly created UserAccount with generated ID</returns>
    /// <exception cref="Exception">Thrown when the newly registered user cannot be retrieved after registration.</exception>
    /// <exception cref="Microsoft.Data.SqlClient.SqlException">Thrown when the database command fails.</exception>
    public async Task<Domain.Entities.UserAccount> RegisterUserAsync(
        string username,
        string firstName,
        string lastName,
        string email,
        DateTime dateOfBirth,
        string passwordHash
    )
    {
        await using var connection = await CreateConnection();
        await using var command = connection.CreateCommand();

        command.CommandText = "USP_RegisterUser";
        command.CommandType = CommandType.StoredProcedure;

        AddParameter(command, "@Username", username);
        AddParameter(command, "@FirstName", firstName);
        AddParameter(command, "@LastName", lastName);
        AddParameter(command, "@Email", email);
        AddParameter(command, "@DateOfBirth", dateOfBirth);
        AddParameter(command, "@Hash", passwordHash);

        var result = await command.ExecuteScalarAsync();

        Guid userAccountId = Guid.Empty;
        if (result != null && result != DBNull.Value)
        {
            if (result is Guid g)
            {
                userAccountId = g;
            }
            else if (result is string s && Guid.TryParse(s, out var parsed))
            {
                userAccountId = parsed;
            }
            else if (result is byte[] bytes && bytes.Length == 16)
            {
                userAccountId = new Guid(bytes);
            }
            else
            {
                // Fallback: try to convert and parse string representation
                try
                {
                    var str = result.ToString();
                    if (!string.IsNullOrEmpty(str) && Guid.TryParse(str, out var p))
                        userAccountId = p;
                }
                catch
                {
                    userAccountId = Guid.Empty;
                }
            }
        }

        return await GetUserByIdAsync(userAccountId) ?? throw new Exception("Failed to retrieve newly registered user.");
    }

    /// <summary>
    /// Retrieves a user account by email address (typically used for login) using the
    /// <c>usp_GetUserAccountByEmail</c> stored procedure.
    /// </summary>
    /// <param name="email">Email address to search for</param>
    /// <returns>UserAccount if found, null otherwise</returns>
    /// <exception cref="Microsoft.Data.SqlClient.SqlException">Thrown when the database command fails.</exception>
    public async Task<Domain.Entities.UserAccount?> GetUserByEmailAsync(
        string email
    )
    {
        await using var connection = await CreateConnection();
        await using var command = connection.CreateCommand();
        command.CommandText = "usp_GetUserAccountByEmail";
        command.CommandType = CommandType.StoredProcedure;

        AddParameter(command, "@Email", email);

        await using var reader = await command.ExecuteReaderAsync();
        return await reader.ReadAsync() ? MapToEntity(reader) : null;
    }

    /// <summary>
    /// Retrieves a user account by username (typically used for login) using the
    /// <c>usp_GetUserAccountByUsername</c> stored procedure.
    /// </summary>
    /// <param name="username">Username to search for</param>
    /// <returns>UserAccount if found, null otherwise</returns>
    /// <exception cref="Microsoft.Data.SqlClient.SqlException">Thrown when the database command fails.</exception>
    public async Task<Domain.Entities.UserAccount?> GetUserByUsernameAsync(
        string username
    )
    {
        await using var connection = await CreateConnection();
        await using var command = connection.CreateCommand();
        command.CommandText = "usp_GetUserAccountByUsername";
        command.CommandType = CommandType.StoredProcedure;

        AddParameter(command, "@Username", username);

        await using var reader = await command.ExecuteReaderAsync();
        return await reader.ReadAsync() ? MapToEntity(reader) : null;
    }

    /// <summary>
    /// Retrieves the active (non-revoked) credential for a user account using the
    /// <c>USP_GetActiveUserCredentialByUserAccountId</c> stored procedure.
    /// </summary>
    /// <param name="userAccountId">ID of the user account</param>
    /// <returns>Active UserCredential if found, null otherwise</returns>
    /// <exception cref="Microsoft.Data.SqlClient.SqlException">Thrown when the database command fails.</exception>
    public async Task<UserCredential?> GetActiveCredentialByUserAccountIdAsync(
        Guid userAccountId
    )
    {
        await using var connection = await CreateConnection();
        await using var command = connection.CreateCommand();
        command.CommandText = "USP_GetActiveUserCredentialByUserAccountId";
        command.CommandType = CommandType.StoredProcedure;

        AddParameter(command, "@UserAccountId", userAccountId);

        await using var reader = await command.ExecuteReaderAsync();
        return await reader.ReadAsync() ? MapToCredentialEntity(reader) : null;
    }

    /// <summary>
    /// Rotates a user's credential by invalidating all existing credentials and creating a new one,
    /// using the <c>USP_RotateUserCredential</c> stored procedure.
    /// </summary>
    /// <param name="userAccountId">ID of the user account</param>
    /// <param name="newPasswordHash">New hashed password</param>
    /// <exception cref="Microsoft.Data.SqlClient.SqlException">Thrown when the database command fails.</exception>
    public async Task RotateCredentialAsync(
        Guid userAccountId,
        string newPasswordHash
    )
    {
        await using var connection = await CreateConnection();
        await using var command = connection.CreateCommand();
        command.CommandText = "USP_RotateUserCredential";
        command.CommandType = CommandType.StoredProcedure;

        AddParameter(command, "@UserAccountId_", userAccountId);
        AddParameter(command, "@Hash", newPasswordHash);

        await command.ExecuteNonQueryAsync();
    }

    /// <summary>
    /// Retrieves a user account by ID using the <c>usp_GetUserAccountById</c> stored procedure.
    /// </summary>
    /// <param name="userAccountId">ID of the user account</param>
    /// <returns>UserAccount if found, null otherwise</returns>
    /// <exception cref="Microsoft.Data.SqlClient.SqlException">Thrown when the database command fails.</exception>
    public async Task<Domain.Entities.UserAccount?> GetUserByIdAsync(
        Guid userAccountId
    )
    {
        await using var connection = await CreateConnection();
        await using var command = connection.CreateCommand();
        command.CommandText = "usp_GetUserAccountById";
        command.CommandType = CommandType.StoredProcedure;

        AddParameter(command, "@UserAccountId", userAccountId);

        await using var reader = await command.ExecuteReaderAsync();
        return await reader.ReadAsync() ? MapToEntity(reader) : null;
    }

    /// <summary>
    /// Marks a user account as confirmed by creating a verification record via the
    /// <c>USP_CreateUserVerification</c> stored procedure. If the user is already verified, this is a
    /// no-op and the existing user is returned (idempotent). If a concurrent request verifies the user
    /// first, the resulting duplicate-key SQL exception (error 2601/2627) is swallowed.
    /// </summary>
    /// <param name="userAccountId">ID of the user account to confirm</param>
    /// <returns>The confirmed <see cref="Domain.Entities.UserAccount"/>, or <c>null</c> if the user account does not exist.</returns>
    /// <exception cref="Microsoft.Data.SqlClient.SqlException">Thrown when the database command fails for a reason other than a duplicate verification record.</exception>
    public async Task<Domain.Entities.UserAccount?> ConfirmUserAccountAsync(
        Guid userAccountId
    )
    {
        var user = await GetUserByIdAsync(userAccountId);
        if (user == null)
        {
            return null;
        }

        // Idempotency: if already verified, treat as successful confirmation.
        if (await IsUserVerifiedAsync(userAccountId))
        {
            return user;
        }

        await using var connection = await CreateConnection();
        await using var command = connection.CreateCommand();
        command.CommandText = "USP_CreateUserVerification";
        command.CommandType = CommandType.StoredProcedure;

        AddParameter(command, "@UserAccountID_", userAccountId);

        try
        {
            await command.ExecuteNonQueryAsync();
        }
        catch (SqlException ex) when (IsDuplicateVerificationViolation(ex))
        {
            // A concurrent request verified this user first. Keep behavior idempotent.
        }

        // Fetch and return the updated user
        return await GetUserByIdAsync(userAccountId);
    }

    /// <summary>
    /// Checks whether a user account has been verified by querying the
    /// <c>dbo.UserVerification</c> table for a matching record.
    /// </summary>
    /// <param name="userAccountId">ID of the user account</param>
    /// <returns>True if the user has a verification record, false otherwise</returns>
    /// <exception cref="Microsoft.Data.SqlClient.SqlException">Thrown when the database command fails.</exception>
    public async Task<bool> IsUserVerifiedAsync(Guid userAccountId)
    {
        await using var connection = await CreateConnection();
        await using var command = connection.CreateCommand();
        command.CommandText =
            "SELECT TOP 1 1 FROM dbo.UserVerification WHERE UserAccountID = @UserAccountID";
        command.CommandType = CommandType.Text;

        AddParameter(command, "@UserAccountID", userAccountId);

        var result = await command.ExecuteScalarAsync();
        return result != null && result != DBNull.Value;
    }

    /// <summary>
    /// Determines whether a <see cref="SqlException"/> represents a duplicate key violation
    /// (SQL Server error 2601 or 2627), used to detect a concurrent duplicate verification insert.
    /// </summary>
    /// <param name="ex">The SQL exception to inspect.</param>
    /// <returns>True if the exception represents a duplicate key violation, false otherwise.</returns>
    private static bool IsDuplicateVerificationViolation(SqlException ex)
    {
        // 2601/2627 are duplicate key violations in SQL Server.
        return ex.Number == 2601 || ex.Number == 2627;
    }


    /// <summary>
    /// Maps a data reader row to a UserAccount entity.
    /// </summary>
    /// <param name="reader">The data reader positioned on the row to map.</param>
    /// <returns>The mapped <see cref="Domain.Entities.UserAccount"/> instance.</returns>
    protected override Domain.Entities.UserAccount MapToEntity(
        DbDataReader reader
    )
    {
        return new Domain.Entities.UserAccount
        {
            UserAccountId = reader.GetGuid(reader.GetOrdinal("UserAccountId")),
            Username = reader.GetString(reader.GetOrdinal("Username")),
            FirstName = reader.GetString(reader.GetOrdinal("FirstName")),
            LastName = reader.GetString(reader.GetOrdinal("LastName")),
            Email = reader.GetString(reader.GetOrdinal("Email")),
            CreatedAt = reader.GetDateTime(reader.GetOrdinal("CreatedAt")),
            UpdatedAt = reader.IsDBNull(reader.GetOrdinal("UpdatedAt"))
                ? null
                : reader.GetDateTime(reader.GetOrdinal("UpdatedAt")),
            DateOfBirth = reader.GetDateTime(reader.GetOrdinal("DateOfBirth")),
            Timer = reader.IsDBNull(reader.GetOrdinal("Timer"))
                ? null
                : (byte[])reader["Timer"],
        };
    }

    /// <summary>
    /// Maps a data reader row to a UserCredential entity. The <c>Timer</c> column is mapped only if
    /// present in the reader's schema, allowing this method to support result sets that omit it.
    /// </summary>
    /// <param name="reader">The data reader positioned on the row to map.</param>
    /// <returns>The mapped <see cref="UserCredential"/> instance.</returns>
    private static UserCredential MapToCredentialEntity(DbDataReader reader)
    {
        var entity = new UserCredential
        {
            UserCredentialId = reader.GetGuid(
                reader.GetOrdinal("UserCredentialId")
            ),
            UserAccountId = reader.GetGuid(reader.GetOrdinal("UserAccountId")),
            Hash = reader.GetString(reader.GetOrdinal("Hash")),
            CreatedAt = reader.GetDateTime(reader.GetOrdinal("CreatedAt")),
        };

        // Optional columns
        var hasTimer =
            reader
                .GetSchemaTable()
                ?.Rows.Cast<System.Data.DataRow>()
                .Any(r =>
                    string.Equals(
                        r["ColumnName"]?.ToString(),
                        "Timer",
                        StringComparison.OrdinalIgnoreCase
                    )
                ) ?? false;

        if (hasTimer)
        {
            entity.Timer = reader.IsDBNull(reader.GetOrdinal("Timer"))
                ? null
                : (byte[])reader["Timer"];
        }

        return entity;
    }

    /// <summary>
    /// Helper method to add a parameter to a database command, converting <c>null</c> values to
    /// <see cref="DBNull.Value"/>.
    /// </summary>
    /// <param name="command">The command to add the parameter to.</param>
    /// <param name="name">The parameter name (including any prefix, e.g. "@Username").</param>
    /// <param name="value">The parameter value, or <c>null</c> to bind <see cref="DBNull.Value"/>.</param>
    private static void AddParameter(
        DbCommand command,
        string name,
        object? value
    )
    {
        var p = command.CreateParameter();
        p.ParameterName = name;
        p.Value = value ?? DBNull.Value;
        command.Parameters.Add(p);
    }
}