#if NET48
using System.Data.Entity;
#else
using Microsoft.EntityFrameworkCore;
#endif
using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Threading;
using System.Threading.Tasks;
using AutoMapper;
using ECMJobRunner.Domain.Interfaces;
using ECMJobRunner.Infrastructure.Data;

namespace ECMJobRunner.Infrastructure.Repositories
{
    /// <summary>
    /// Generic repository implementation for Entity Framework
    /// Uses AutoMapper for DTO mapping
    /// </summary>
    /// <typeparam name="TEntity">Entity type</typeparam>
    public class Repository<TEntity> : IRepository<TEntity> where TEntity : class
    {
        /// <summary>
        /// Database context
        /// </summary>
        protected readonly JobRunnerDbContext _context;
        
        /// <summary>
        /// DbSet for the entity
        /// </summary>
        protected readonly DbSet<TEntity> _dbSet;
        
        /// <summary>
        /// AutoMapper instance for DTO mapping
        /// </summary>
        protected readonly IMapper _mapper;

        /// <summary>
        /// Constructor
        /// </summary>
        public Repository(JobRunnerDbContext context, IMapper mapper)
        {
            _context = context ?? throw new ArgumentNullException(nameof(context));
            _mapper = mapper ?? throw new ArgumentNullException(nameof(mapper));
            _dbSet = context.Set<TEntity>();
        }

        /// <inheritdoc/>
        public virtual async Task<TEntity?> GetByIdAsync(long id, CancellationToken cancellationToken = default)
        {
#if NET48
            return await _dbSet.FindAsync(cancellationToken, id);
#else
            return await _dbSet.FindAsync(new object[] { id }, cancellationToken);
#endif
        }

        /// <inheritdoc/>
        public virtual async Task<IEnumerable<TEntity>> GetAllAsync(CancellationToken cancellationToken = default)
        {
            return await _dbSet.ToListAsync(cancellationToken);
        }

        /// <inheritdoc/>
        public virtual async Task<IEnumerable<TEntity>> FindAsync(Expression<Func<TEntity, bool>> predicate, CancellationToken cancellationToken = default)
        {
            return await _dbSet.Where(predicate).ToListAsync(cancellationToken);
        }

        /// <inheritdoc/>
        public virtual async Task<TEntity?> SingleOrDefaultAsync(Expression<Func<TEntity, bool>> predicate, CancellationToken cancellationToken = default)
        {
            return await _dbSet.SingleOrDefaultAsync(predicate, cancellationToken);
        }

        /// <inheritdoc/>
        public virtual async Task<TEntity> AddAsync<TDto>(TDto dto, CancellationToken cancellationToken = default) where TDto : class
        {
            if (dto == null) throw new ArgumentNullException(nameof(dto));

            var entity = _mapper.Map<TEntity>(dto);

#if NET48
            _dbSet.Add(entity);
            await Task.CompletedTask;
#else
            await _dbSet.AddAsync(entity, cancellationToken);
#endif

            await SaveChangesAsync(cancellationToken);
            return entity;
        }

        /// <inheritdoc/>
        public virtual async Task<int> AddRangeAsync<TDto>(IEnumerable<TDto> dtos, CancellationToken cancellationToken = default) where TDto : class
        {
            if (dtos == null) throw new ArgumentNullException(nameof(dtos));

            var dtoList = dtos.ToList();
            if (!dtoList.Any())
                return 0;

            var entities = _mapper.Map<List<TEntity>>(dtoList);

#if NET48
            _dbSet.AddRange(entities);
            await Task.CompletedTask;
#else
            await _dbSet.AddRangeAsync(entities, cancellationToken);
#endif

            return await SaveChangesAsync(cancellationToken);
        }

        /// <inheritdoc/>
        public virtual async Task<int> UpdateAsync<TDto>(Expression<Func<TEntity, bool>> predicate, TDto dto, CancellationToken cancellationToken = default) where TDto : class
        {
            if (dto == null) throw new ArgumentNullException(nameof(dto));

            var entities = await _dbSet.Where(predicate).ToListAsync(cancellationToken);

            if (!entities.Any())
                return 0;

            foreach (var entity in entities)
            {
                _mapper.Map(dto, entity);
            }

            return await SaveChangesAsync(cancellationToken);
        }

        /// <inheritdoc/>
        public virtual async Task<bool> UpdateSingleAsync<TDto>(Expression<Func<TEntity, bool>> predicate, TDto dto, CancellationToken cancellationToken = default) where TDto : class
        {
            if (dto == null) throw new ArgumentNullException(nameof(dto));

            var entity = await SingleOrDefaultAsync(predicate, cancellationToken);

            if (entity == null)
                return false;

            _mapper.Map(dto, entity);

            await SaveChangesAsync(cancellationToken);
            return true;
        }

        /// <inheritdoc/>
        public virtual async Task<int> DeleteAsync(Expression<Func<TEntity, bool>> predicate, CancellationToken cancellationToken = default)
        {
            var entities = await _dbSet.Where(predicate).ToListAsync(cancellationToken);

            if (!entities.Any())
                return 0;

            _dbSet.RemoveRange(entities);

            return await SaveChangesAsync(cancellationToken);
        }

        /// <inheritdoc/>
        public virtual async Task<bool> DeleteSingleAsync(Expression<Func<TEntity, bool>> predicate, CancellationToken cancellationToken = default)
        {
            var entity = await SingleOrDefaultAsync(predicate, cancellationToken);

            if (entity == null)
                return false;

            _dbSet.Remove(entity);

            await SaveChangesAsync(cancellationToken);
            return true;
        }

        /// <inheritdoc/>
        public virtual async Task<int> SaveChangesAsync(CancellationToken cancellationToken = default)
        {
#if NET48
            return await _context.SaveChangesAsync();
#else
            return await _context.SaveChangesAsync(cancellationToken);
#endif
        }
    }
}