namespace LinqExercise
{
    using System;
    using System.Collections.Generic;
    using System.IO;
    using System.Linq;

    public class LinqExercise
    {
        public static void Main()
        {
            const string FilePath = @"../../Students-data.txt";

            List<string> result = new List<string>();

            StreamReader readData = new StreamReader(FilePath);
            string headerLine = readData.ReadLine();

            string line;
            while ((line = readData.ReadLine()) != null)
            {
                result.Add(line);
            }

            List<Student> students = new List<Student>();

            foreach (string data in result)
            {
                string[] tokens = data.Split();

                int id = int.Parse(tokens[0]);
                string firstName = tokens[1];
                string lastName = tokens[2];
                string email = tokens[3];
                string gender = tokens[4];
                string studentType = tokens[5];
                int examResult = int.Parse(tokens[6]);
                int homeworksSent = int.Parse(tokens[7]);
                int homeworksEvaluated = int.Parse(tokens[8]);
                double teamworkScore = double.Parse(tokens[9]);
                int attendancesCount = int.Parse(tokens[10]);
                double bonus = double.Parse(tokens[11]);

                students.Add(new Student(
                id,
                firstName,
                lastName,
                email,
                gender,
                studentType,
                examResult,
                homeworksSent,
                homeworksEvaluated,
                teamworkScore,
                attendancesCount,
                bonus));
            }

            // TODO write LINQ queries here

            //1
            //var maleStudents = students
            //    .Where(e => e.Gender == "Male");

            //foreach (var student in maleStudents)
            //{
            //    Console.WriteLine(student.FirstName + " " + student.LastName + " - " + student.Gender);
            //}

            //2
            //var studentsFirstNameA = students
            //    .Where(e => e.FirstName.StartsWith("A"));

            //foreach (var student in studentsFirstNameA)
            //{
            //    Console.WriteLine(student.FirstName + " " + student.LastName);
            //}

            //3
            //var studentsOn = students
            //    .Where(e => e.StudentType == "Online" && e.ExamResult >= 350);

            //foreach (var student in studentsOn)
            //{
            //    Console.WriteLine("{0} {1} ({2}) - {3}",
            //        student.FirstName, student.LastName, student.StudentType, student.ExamResult);
            //}

            //4
            //var studentsOn = students
            //    .Where(e => e.StudentType == "Online" && e.ExamResult >= 300)
            //    .OrderByDescending(e => e.ExamResult);

            //foreach (var student in studentsOn)
            //{
            //    Console.WriteLine("{0} {1} ({2}) - {3}",
            //        student.FirstName, student.LastName, student.StudentType, student.ExamResult);
            //}

            //5
            //var studentsHomework = students
            //    .Where(e => e.HomeworksSent == 0)
            //    .OrderBy(e => e.FirstName).ThenBy(e => e.LastName);

            //foreach (var student in studentsHomework)
            //{
            //    Console.WriteLine("{0} {1} ({2} homeworks sent)",
            //        student.FirstName, student.LastName, student.HomeworksSent);
            //}

            //6
            //var studentsOnSite = students
            //    .Where(e => e.StudentType == "Onsite")
            //    .Select(e => e.Email);

            //foreach (var studentEmail in studentsOnSite)
            //{
            //    Console.WriteLine(studentEmail);
            //}

            //7
            //var studentsOnSite = students
            //    .Where(e => e.AttendancesCount < 5)
            //    .Select(e => new
            //    {
            //        e.ExamResult,
            //        e.AttendancesCount
            //    });

            //foreach (var student in studentsOnSite)
            //{
            //    Console.WriteLine("Result: {0}, attendances: {1}", student.ExamResult, student.AttendancesCount);
            //}

            //8
            //var studentsBonus = students
            //    .Where(e => e.Bonus >= 4)
            //    .Count();

            //Console.WriteLine(studentsBonus);

            //9
            var avgExamStudents = students
                .Select(d => new
                {
                    OnlineAverage = students.Where(s => s.StudentType == "Online").Select(s => s.ExamResult).Average(),
                    OnsiteAverage = students.Where(s => s.StudentType == "Onsite").Select(s => s.ExamResult).Average()
                })
                .Distinct();

            foreach (var student in avgExamStudents)
            {
                Console.WriteLine("Online average: " + student.OnlineAverage);
                Console.WriteLine("Onsite average: " + student.OnsiteAverage);
            }

            //10
            var studentsTWScore = students
                .Select(d => new
                {
                    Max = students
                    .Where(s => s.TeamworkScore == students
                        .Select(t => t.TeamworkScore).Max())
                    .Count()
                })
                .Distinct();

            foreach (var student in studentsTWScore)
            {
                Console.WriteLine(student.Max);
            }

            //11
            //var groupStudents = students
            //    .GroupBy(s => s.FirstName.First())
            //    .OrderBy(g => g.Key);

            ////I set this because console window limits the lines of output and you see only part of the output, you need to manually modify it
            ////the other way is in console window -> properties -> layout -> screen buffer size -> height
            //Console.BufferHeight = 1021;

            //foreach (var groupName in groupStudents)
            //{
            //    Console.WriteLine(groupName.Key);
            //    foreach (var student in groupName)
            //    {
            //        Console.WriteLine("  {0} {1}", student.FirstName, student.LastName);
            //    }
            //}

            //12
            var groupByType = students
                .OrderByDescending(s => s.ExamResult)
                .GroupBy(s => s.StudentType);


            Console.BufferHeight = 1021;

            foreach (var group in groupByType)
            {
                Console.WriteLine(group.Key);
                foreach (var student in group)
                {
                    Console.WriteLine("  {0} {1} - {2}",
                        student.FirstName, student.LastName, student.ExamResult);
                }
            }
        }
    }
}