galaeth-draft/Galaeth.DAL/Repositories/BaseRepository.cs

using System.Data;
using System.Reflection;
using System.Text;
using Dapper;
using Galaeth.Core.Attributes.EntityAnnotation;
using Galaeth.Core.Exceptions;
using Galaeth.Core.Infrastructure;
using Galaeth.Core.RepositoryInterfaces;

namespace Galaeth.DAL.Repositories;

/// <inheritdoc />
public class BaseRepository<TEntity, TKeyType> : IGenericRepository<TEntity, TKeyType>
    where TEntity : class
{
    /// <summary>
    /// Instance of <see cref="IDbConnectionProvider"/>.
    /// </summary>
    private readonly IDbConnectionProvider _db;

    /// <summary>
    /// Initializes a new instance of the <see cref="BaseRepository{TEntity, TKeyType}"/> class.
    /// </summary>
    /// <param name="db">Instance of <see cref="IDbConnectionProvider"/>.</param>
    protected BaseRepository(IDbConnectionProvider db)
    {
        _db = db;
        SetupRepository();
    }

    /// <summary>
    /// Table name.
    /// </summary>
    protected string Table { get; set; }

    /// <summary>
    /// Primary key column name.
    /// </summary>
    private string PrimaryKeyColumn { get; set; }

    /// <summary>
    /// Whether the primary key should be treated as auto-generated by the database.
    /// </summary>
    private bool AutoPrimaryKey { get; set; }

    /// <summary>
    /// Generated select all query string.
    /// </summary>
    private string SelectAllQuery { get; set; }

    /// <summary>
    /// Generated find by id query string.
    /// </summary>
    private string FindByIdQuery { get; set; }

    /// <summary>
    /// Generated insert query string.
    /// </summary>
    private string InsertQuery { get; set; }

    /// <summary>
    /// Generated update query string.
    /// </summary>
    private string UpdateQuery { get; set; }

    /// <summary>
    /// Generated delete query string.
    /// </summary>
    private string DeleteQuery { get; set; }

    /// <inheritdoc cref="Galaeth.Core.RepositoryInterfaces.IGenericRepository{TEntity,TKeyType}" />
    public async Task<TEntity> FindByIdAsync(TKeyType id)
    {
        return await WithDatabaseAsync(async connection =>
        {
            var result = await connection.QueryFirstOrDefaultAsync<TEntity>(FindByIdQuery, new
            {
                pId = id,
            });

            return result;
        });
    }

    /// <inheritdoc cref="Galaeth.Core.RepositoryInterfaces.IGenericRepository{TEntity,TKeyType}" />
    public async Task<IEnumerable<TEntity>> GetAllAsync()
    {
        return await WithDatabaseAsync(async connection =>
        {
            var result = await connection.QueryAsync<TEntity>(SelectAllQuery);

            return result;
        });
    }

    /// <inheritdoc cref="Galaeth.Core.RepositoryInterfaces.IGenericRepository{TEntity,TKeyType}" />
    public async Task<TKeyType> AddAsync(TEntity entity)
    {
        return await WithDatabaseAsync(async connection =>
        {
            return await connection.QuerySingleAsync<TKeyType>(
                InsertQuery, entity);
        });
    }

    /// <inheritdoc cref="Galaeth.Core.RepositoryInterfaces.IGenericRepository{TEntity,TKeyType}" />
    public async Task AddAsync(IEnumerable<TEntity> entities)
    {
        await WithDatabaseAsync(async connection =>
        {
            await connection.ExecuteAsync(
                InsertQuery, entities);
        });
    }

    /// <inheritdoc cref="Galaeth.Core.RepositoryInterfaces.IGenericRepository{TEntity,TKeyType}" />
    public async Task<bool> UpdateAsync(TEntity entity)
    {
        return await WithDatabaseAsync(async connection => await connection.ExecuteAsync(UpdateQuery, entity) > 0);
    }

    /// <inheritdoc cref="Galaeth.Core.RepositoryInterfaces.IGenericRepository{TEntity,TKeyType}" />
    public async Task DeleteAsync(TKeyType id)
    {
        await WithDatabaseAsync(async connection => await connection.ExecuteAsync(DeleteQuery, new
        {
            pId = id,
        }));
    }

    /// <summary>
    /// Establish a connection and perform the query function.
    /// </summary>
    /// <param name="query">Query method to execute.</param>
    /// <typeparam name="T">The return type.</typeparam>
    /// <returns>Result of query.</returns>
    /// <exception cref="Exception">Thrown if an exception occurs.</exception>
    protected async Task<T> WithDatabaseAsync<T>(Func<IDbConnection, Task<T>> query)
    {
        var connection = await _db.OpenConnectionAsync();
        return await query(connection);
    }

    /// <summary>
    /// Establish a connection and perform the query function.
    /// </summary>
    /// <param name="query">Query method to execute.</param>
    protected async Task WithDatabaseAsync(Func<IDbConnection, Task> query)
    {
        var connection = await _db.OpenConnectionAsync();
        await query(connection);
    }

    /// <summary>
    /// Fetch a comma separated list of property names.
    /// </summary>
    /// <param name="excludeKey">True to exclude key property.</param>
    /// <returns>Comma separated list of column names.</returns>
    private static string GetPropertyNames(bool excludeKey = false)
    {
        var properties = typeof(TEntity).GetProperties()
            .Where(p => !excludeKey || p.GetCustomAttribute<PrimaryKeyAttribute>() == null)
            .Where(p => p.IsDefined(typeof(PrimaryKeyAttribute), true) ||
                        p.IsDefined(typeof(ColumnMappingAttribute), true));

        var values = string.Join(", ", properties.Select(p => $"@{p.Name}"));

        return values;
    }

    /// <summary>
    /// Setup repository.
    /// </summary>
    private void SetupRepository()
    {
        var entityType = typeof(TEntity);
        var properties = entityType.GetProperties();
        var propertiesExcludingKey = properties
            .Where(p => p.GetCustomAttribute<PrimaryKeyAttribute>() == null);

        // Set up table name.
        var tableAttribute = entityType.GetCustomAttribute<TableMappingAttribute>();
        if (tableAttribute is null)
        {
            Table = typeof(TEntity).Name + "s";
        }
        else
        {
            Table = tableAttribute.Name;
        }

        // Set up primary key.
        var primaryKeyProperties = properties.Where(p => p.IsDefined(typeof(PrimaryKeyAttribute), true)).ToList();

        if (primaryKeyProperties is null || primaryKeyProperties.Count == 0)
        {
            throw new PrimaryKeyMissingException(typeof(TEntity));
        }

        if (primaryKeyProperties.Count > 1)
        {
            throw new MultiplePrimaryKeysException(typeof(TEntity));
        }

        var primaryKeyProperty = primaryKeyProperties.First();
        var primaryKey = primaryKeyProperty.GetCustomAttribute<PrimaryKeyAttribute>();
        var primaryKeyCol = primaryKeyProperty.GetCustomAttribute<ColumnMappingAttribute>();

        if (primaryKeyCol is null)
        {
            throw new MissingColumnAttributeException(typeof(TEntity));
        }

        PrimaryKeyColumn = primaryKeyCol!.Name;
        AutoPrimaryKey = primaryKey!.AutoGenerated;

        SelectAllQuery = $"SELECT * FROM {Table};";
        FindByIdQuery = $"SELECT * FROM {Table} WHERE {PrimaryKeyColumn} = @pId;";

        // Add query.
        var columns = string.Join(", ", properties
            .Where(p => !AutoPrimaryKey || !p.IsDefined(typeof(PrimaryKeyAttribute)))
            .Where(p => p.IsDefined(typeof(ColumnMappingAttribute)))
            .Select(p => p.GetCustomAttribute<ColumnMappingAttribute>() !.Name));

        var propertyNames = GetPropertyNames(AutoPrimaryKey);

        var insertQuery = new StringBuilder();
        insertQuery.Append(
            $"INSERT INTO {Table} ({columns}) VALUES ({propertyNames}) RETURNING {PrimaryKeyColumn};");

        InsertQuery = insertQuery.ToString();

        // Update query.
        var updateQuery = new StringBuilder();
        updateQuery.Append($"UPDATE {Table} SET");
        foreach (var property in propertiesExcludingKey.Where(p => p.IsDefined(typeof(ColumnMappingAttribute))))
        {
            var columnAttr = property.GetCustomAttribute<ColumnMappingAttribute>();
            var propertyName = property.Name;
            updateQuery.Append($" {columnAttr!.Name} = @{propertyName},");
        }

        updateQuery.Remove(updateQuery.Length - 1, 1);
        updateQuery.Append($" WHERE {PrimaryKeyColumn} = @{primaryKeyProperty.Name};");
        UpdateQuery = updateQuery.ToString();

        // Delete query.
        DeleteQuery = $"DELETE FROM {Table} WHERE {PrimaryKeyColumn} = @pId;";
    }
}