using Microsoft.EntityFrameworkCore;
using System.Linq.Expressions;

namespace Core.Blueprint.DAL.SQLServer
{
    /// <summary>
    /// The <see cref="EntityRepository{TEntity, TContext}"/> class provides a comprehensive generic repository 
    /// for managing entities using Entity Framework Core with SQL Server as the underlying database.
    /// Designed as a package for consumption by external applications.
    /// </summary>
    /// <typeparam name="TEntity">The entity type managed by the repository. Must be a class.</typeparam>
    /// <typeparam name="TContext">The database context type. Must inherit from <see cref="DbContext"/>.</typeparam>
    public class EntityRepository<TEntity, TContext> : IEntityRepository<TEntity, TContext>
        where TEntity : class
        where TContext : DbContext
    {
        private readonly TContext _context;
        private readonly DbSet<TEntity> _dbSet;

        /// <summary>
        /// Initializes a new instance of the <see cref="EntityRepository{TEntity, TContext}"/> class with a specified database context.
        /// </summary>
        /// <param name="context">The <see cref="TContext"/> for database operations.</param>
        public EntityRepository(TContext context)
        {
            _context = context;
            _dbSet = _context.Set<TEntity>();
        }

        /// <summary>
        /// Retrieves all entities of type <typeparamref name="TEntity"/> from the database.
        /// </summary>
        /// <returns>A task representing the asynchronous operation, with a list of entities as the result.</returns>
        public async Task<IEnumerable<TEntity>> GetAllAsync()
        {
            return await _dbSet.ToListAsync();
        }

        /// <summary>
        /// Retrieves all entities of type <typeparamref name="TEntity"/> from the database that match a specified filter.
        /// </summary>
        /// <param name="predicate">An expression to filter entities.</param>
        /// <returns>A task representing the asynchronous operation, with a list of filtered entities as the result.</returns>
        public async Task<IEnumerable<TEntity>> GetByConditionAsync(Expression<Func<TEntity, bool>> predicate)
        {
            return await _dbSet.Where(predicate).ToListAsync();
        }

        /// <summary>
        /// Retrieves a single entity of type <typeparamref name="TEntity"/> by its identifier.
        /// </summary>
        /// <param name="id">The identifier of the entity.</param>
        /// <returns>A task representing the asynchronous operation, with the entity as the result, or null if not found.</returns>
        public async Task<TEntity?> GetByIdAsync(int id)
        {
            var existingEntity = await _dbSet.FindAsync(id);

            if (existingEntity != null)
            {
                _context.Entry(existingEntity).State = EntityState.Detached;
            }

            return existingEntity;
        }

        /// <summary>
        /// Adds a new entity to the database.
        /// </summary>
        /// <param name="entity">The entity to add.</param>
        /// <returns>A task representing the asynchronous operation.</returns>
        public async Task AddAsync(TEntity entity)
        {
            await _dbSet.AddAsync(entity);
        }

        /// <summary>
        /// Adds multiple entities to the database.
        /// </summary>
        /// <param name="entities">The collection of entities to add.</param>
        /// <returns>A task representing the asynchronous operation.</returns>
        public async Task AddRangeAsync(IEnumerable<TEntity> entities)
        {
            await _dbSet.AddRangeAsync(entities);
        }

        /// <summary>
        /// Updates an existing entity in the database.
        /// </summary>
        /// <param name="entity">The entity to update.</param>
        /// <returns>The updated entity.</returns>
        public TEntity Update(TEntity entity)
        {
            _dbSet.Attach(entity);
            _context.Entry(entity).State = EntityState.Modified;
            return entity;
        }

        /// <summary>
        /// Updates multiple entities in the database.
        /// </summary>
        /// <param name="entities">The collection of entities to update.</param>
        public void UpdateRange(IEnumerable<TEntity> entities)
        {
            foreach (var entity in entities)
            {
                _dbSet.Attach(entity);
                _context.Entry(entity).State = EntityState.Modified;
            }
        }

        /// <summary>
        /// Deletes an entity from the database.
        /// </summary>
        /// <param name="entity">The entity to delete.</param>
        public void Delete(TEntity entity)
        {
            if (_context.Entry(entity).State == EntityState.Detached)
            {
                _dbSet.Attach(entity);
            }
            _dbSet.Remove(entity);
        }

        /// <summary>
        /// Deletes multiple entities from the database.
        /// </summary>
        /// <param name="entities">The collection of entities to delete.</param>
        public void DeleteRange(IEnumerable<TEntity> entities)
        {
            _dbSet.RemoveRange(entities);
        }

        /// <summary>
        /// Retrieves the first entity matching the specified condition or null if no match is found.
        /// </summary>
        /// <param name="predicate">An expression to filter entities.</param>
        /// <returns>A task representing the asynchronous operation, with the matched entity as the result.</returns>
        public async Task<TEntity?> FirstOrDefaultAsync(Expression<Func<TEntity, bool>> predicate)
        {
            return await _dbSet.FirstOrDefaultAsync(predicate);
        }

        /// <summary>
        /// Determines if any entities exist that match the specified condition.
        /// </summary>
        /// <param name="predicate">An expression to filter entities.</param>
        /// <returns>A task representing the asynchronous operation, with a boolean result indicating existence.</returns>
        public async Task<bool> AnyAsync(Expression<Func<TEntity, bool>> predicate)
        {
            return await _dbSet.AnyAsync(predicate);
        }

        /// <summary>
        /// Saves all pending changes to the database.
        /// </summary>
        /// <returns>A task representing the asynchronous operation.</returns>
        public async Task SaveAsync()
        {
            await _context.SaveChangesAsync();
        }

        /// <summary>
        /// Executes a raw SQL query and maps the result to the specified entity type.
        /// </summary>
        /// <param name="sql">The raw SQL query.</param>
        /// <param name="parameters">Optional parameters for the query.</param>
        /// <returns>An <see cref="IEnumerable{TEntity}"/> representing the result set.</returns>
        public async Task<IEnumerable<TEntity>> ExecuteRawSqlAsync(string sql, params object[] parameters)
        {
            return await _dbSet.FromSqlRaw(sql, parameters).ToListAsync();
        }

        /// <summary>
        /// Counts the total number of entities in the database.
        /// </summary>
        /// <returns>A task representing the asynchronous operation, with the count as the result.</returns>
        public async Task<int> CountAsync()
        {
            return await _dbSet.CountAsync();
        }
    }
}