using Microsoft.EntityFrameworkCore;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net.Http.Headers;
using System.Text;
using System.Threading.Tasks;
using UniversityContracts.BindingModels;
using UniversityContracts.SearchModels;
using UniversityContracts.StoragesContracts;
using UniversityContracts.ViewModels;
using UniversityDataBaseImplemet.Models;

namespace UniversityDataBaseImplemet.Implements
{
    public class DocumentStorage : IDocumentStorage
    {
        public DocumentViewModel? GetElement(DocumentSearchModel model)
        {
            if (!model.Id.HasValue)
            {
                return null;
            }
            using var context = new Database();
            return context.Documents
                .Include(record => record.User)
                .FirstOrDefault(record => record.Id == model.Id
                    || record.Name.Equals(model.Name))
                ?.GetViewModel;
        }
        public List<DocumentViewModel> GetFilteredList(DocumentSearchModel model)
        {
            using var context = new Database();
            if (model.Id.HasValue)
            {
                return context.Documents
                    .Include(record => record.User)
                    .Where(record => record.Id.Equals(model.Id))
                    .Select(record => record.GetViewModel)
                    .ToList();
            }
            else if (model.DateFrom != null && model.DateTo != null && model.UserId.HasValue) // фильтрация для отчета#2 Поставщик
            {
                return context.Documents
                        .Where(d => d.Date >= model.DateFrom && d.Date <= model.DateTo)
                        .Join(context.StudentDocuments,
                            doc => doc.Id,
                            studDoc => studDoc.DocumentId,
                            (doc, studDoc) => new { Document = doc, StudentDocument = studDoc })
                        .Join(context.Students,
                            studDoc => studDoc.StudentDocument.StudentId,
                            stud => stud.Id,
                            (studDoc, stud) => new { studDoc.Document, Student = stud })
                        .Include(record => record.Student.EducationStatus)
                        .Join(context.StudentStreams,
                            studEdu => studEdu.Student.Id,
                            studStream => studStream.StudentId,
                            (studEdu, studStream) => new { studEdu.Document, studEdu.Student, studEdu.EducationStatus, StudentStream = studStream })
                        .Join(context.Streams,
                            studStream => studStream.StudentStream.StreamId,
                            stream => stream.Id,
                            (studStream, stream) => new { Stream = stream.Name, studStream.Student, studStream.EducationStatus.Name })
                        .Select(result => new {
                            result.Stream,
                            result.Student,
                            result.EducationStatus
                        })
                        .ToList();
            }
            else if (model.UserId.HasValue)
            {
                return context.Documents
                   .Include(record => record.User)
                   .Where(record => record.UserId == model.UserId)
                   .Select(record => record.GetViewModel)
                   .ToList();
            }            
            else
            {
                return new();
            }
        }
        public List<DocumentViewModel> GetFullList()
        {
            using var context = new Database();
            return context.Documents
                .Include(record => record.User)
                .Select(record => record.GetViewModel)
                .ToList();
        }
        public DocumentViewModel? Insert(DocumentBindingModel model)
        {
            var newDocument = Document.Create(model);
            if(newDocument == null) 
            {
                return null;
            }
            using var context = new Database();
            context.Documents.Add(newDocument);
            context.SaveChanges();
            return newDocument.GetViewModel;
        }
        public DocumentViewModel? Update(DocumentBindingModel model)
        {
            using var context = new Database();
            using var transaction = context.Database.BeginTransaction();
            try
            {
                var document = context.Documents
                    .Include(record => record.User)
                    .FirstOrDefault(record => record.Id.Equals(model.Id));
                if (document == null)
                {
                    return null;
                }
                document.Update(model);
                context.SaveChanges();
                transaction.Commit();
                return document.GetViewModel;
            }
            catch
            {
                transaction.Rollback();
                throw;
            }
        }
        public DocumentViewModel? Delete(DocumentBindingModel model)
        {
            using var context = new Database();
            var document = context.Documents
                .Include(record => record.User)
                .FirstOrDefault(record => record.Id.Equals(model.Id));
            if (document == null)
            {
                return null;
            }
            context.Documents.Remove(document);
            context.SaveChanges();
            return document.GetViewModel;
        }
    }
}