using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using UniversityContracts.BindingModels;
using UniversityContracts.ViewModels;
using UniversityModels.Models;

namespace UniversityDataBaseImplemet.Models
{
    public class Document : IDocumentModel
    {
        public int Id { get; private set; }
        [Required]
        public string Name { get; set; } = string.Empty;
        [Required]
        public DateTime Date { get; set; }
        [Required]
        public int UserId { get; set; }
        [ForeignKey("DocumentId")]
        public virtual List<StudentDocument> Students { get; set; } = new();
        [ForeignKey("DocumentId")]
        public virtual List<EducationGroupDocument> EducationGroupDocument { get; set; } = new();
        public virtual User User { get; set; }
        private List<StudentViewModel>? _documentStudents = null;
        [NotMapped]
        public List<StudentViewModel> DocumentStudents
        {
            get
            {
                if (_documentStudents == null)
                {
                    _documentStudents = Students.Select(x => new StudentViewModel(x.Student)).ToList();
                }
                return _documentStudents;
            }
        }
        private List<EducationGroupViewModel>? _documentEdGroups = null;
        [NotMapped]
        public List<EducationGroupViewModel> DocumentEdGroups
        {
            get
            {
                if (_documentEdGroups == null)
                {
                    _documentEdGroups = EducationGroupDocument.Select(x => new EducationGroupViewModel(x.EducationGroup)).ToList();
                }
                return _documentEdGroups;
            }
        }
        public static Document? Create(Database context, DocumentBindingModel? model)
        {
            if (model == null)
            {
                return null;
            }
            return new Document()
            {
                Id = model.Id,
                Name = model.Name,
                Date = model.Date,
                UserId = model.UserId,
                Students = model.DocumentStudents.Select(x => new StudentDocument()
                {
                    Student = context.Students.First(y => y.Id == x.Id),
                }).ToList()
            };
        }
        public void Update(DocumentBindingModel model)
        {
            if(model == null)
            {
                return;
            }
            Name = model.Name;
            Date = model.Date;
            UserId = model.UserId;
        }
        public void UpdateStudents(Database context, DocumentBindingModel model)
        {
            var documentStudents = context.StudentDocuments.Where(x => x.DocumentId == model.Id).ToList();
            List<int> currentStudents = documentStudents.Select(x => x.StudentId).ToList();
            List<int> modelStudents = model.DocumentStudents.Select(x => x.Id).ToList();
            if (documentStudents != null && documentStudents.Count > 0)
            {
                context.StudentDocuments.RemoveRange(documentStudents.Where(x => !modelStudents.Contains(x.StudentId)));
                model.DocumentStudents.RemoveAll(x => currentStudents.Contains(x.Id));
                context.SaveChanges();
            }
            var document = context.Documents.First(x => x.Id == Id);
            foreach (var record in model.DocumentStudents)
            {
                context.StudentDocuments.Add(new StudentDocument
                {
                    Document = document,
                    Student = context.Students.First(x => x.Id == record.Id),
                });
                context.SaveChanges();
            }
            _documentStudents = null;
        }
        public void UpdateGroups(Database context, DocumentBindingModel model)
        {
            var documentGroups = context.EducationGroupsDocuments.Where(x => x.DocumentId == model.Id).ToList();
            List<int> currentGroups = documentGroups.Select(x => x.EducationGroupId).ToList();
            List<int> modelGroups = model.DocumentGroups.Select(x => x.Id).ToList();
            if (documentGroups != null && documentGroups.Count > 0)
            {
                context.EducationGroupsDocuments.RemoveRange(documentGroups.Where(x => !modelGroups.Contains(x.EducationGroupId)));
                model.DocumentGroups.RemoveAll(x => currentGroups.Contains(x.Id));
                context.SaveChanges();
            }
            var document = context.Documents.First(x => x.Id == Id);
            foreach (var record in model.DocumentGroups)
            {
                context.EducationGroupsDocuments.Add(new EducationGroupDocument
                {
                    Document = document,
                    EducationGroup = context.EducationGroups.First(x => x.Id == record.Id),
                });
                context.SaveChanges();
            }
            _documentEdGroups = null;
        }
        public DocumentViewModel GetViewModel => new()
        {
            Id = Id,
            Name = Name,
            Date = Date,
            UserId = UserId,
            DocumentStudents = DocumentStudents,
            DocumentEdGroups = DocumentEdGroups,
        };
    }
}