using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using WguApp.Controls;
using WguApp.Models;
using WguApp.Services;

namespace WguApp.Views;

public partial class TermPage : ContentPage
{

    private Term _term;

    private List<Course> _courses = [];
    
    public TermPage(Term term)
    {
        InitializeComponent();
        
        _term = term;
        
        Title = string.IsNullOrWhiteSpace(_term.Name) ? "Term" : _term.Name;
        TitleEntry.Text = _term.Name;
        
        StartDatePicker.Date = _term.StartDate;
        EndDatePicker.Date = _term.EndDate;
    }

    private async Task RefreshCourseList()
    {
        _courses.Clear();
        _courses = await DatabaseService.GetCoursesByTermId(_term.Id);
        
        CourseButtonStack.Children.Clear();

        foreach (var course in _courses)
        {
            var btn = new CustomButton()
            {
                Text = course.Name,
                DateText = $"{DateOnly.FromDateTime(course.StartDate).ToString()} - {DateOnly.FromDateTime(course.EndDate).ToString()}"
            };
            
            CourseButtonStack.Add(btn);

            btn.Clicked += (sender, e) =>
            {
                HandleCourseButtonClick(course);
            };
        }
    }
    
    protected override async void OnNavigatedTo(NavigatedToEventArgs args)
    {
        try
        {
            await RefreshCourseList();
        }
        catch (Exception e)
        {
            await DisplayAlert("Error", e.Message, "Ok");
        }
    }

    private async void HandleCourseButtonClick(Course course)
    {
        await Navigation.PushAsync(new CoursePage(course));
    }

    private async void SaveButton_OnClicked(object? sender, EventArgs e)
    {
        var validationResult = ValidateFields();

        if (!validationResult.result)
        {
            await DisplayAlert("Validation Error", validationResult.msg, "Ok");
            return;
        }
        
        _term.Name = TitleEntry.Text;
        _term.StartDate = StartDatePicker.Date;
        _term.EndDate = EndDatePicker.Date;
        
        var updateResult = await DatabaseService.UpdateTerm(_term);

        if (updateResult)
        {
            await DisplayAlert("Info", $"{_term.Name} Saved!", "Ok");
        }
        else
        {
            await DisplayAlert("Error", "Could not save term", "Ok");
        }

        Title = _term.Name;
    }

    private (string msg, bool result) ValidateFields()
    {
        var message = string.Empty;
        
        if (string.IsNullOrWhiteSpace(TitleEntry.Text)) message += "Title cannot be blank\n";
        if (StartDatePicker.Date > EndDatePicker.Date) message += "Start Date cannot be after the End Date\n";

        return string.IsNullOrWhiteSpace(message) ? (message, true) : (message, false);
    }

    private async void DeleteButton_OnClicked(object? sender, EventArgs e)
    {
        var result = await DisplayAlert("Delete Term", $"Do you really want to delete '{_term.Name}'? This action cannot be undone.", "Delete", "Cancel");
        if (!result) return;
        
        await DatabaseService.DeleteTerm(_term);
        await Navigation.PopAsync();
    }

    private async void AddCourseButton_OnClicked(object? sender, EventArgs e)
    {
        if (_courses.Count >= 6)
        {
            await DisplayAlert("Info", $"Cannot add more than 6 courses per term", "Ok");
            return;
        }
        
        var course = new Course()
        {
            TermId = _term.Id,
            Name = "New Course",
            StartDate = DateTime.Today,
            EndDate = DateTime.Today.AddDays(30),
            InstructorName = "",
            InstructorEmail = "",
            InstructorPhone = "",
            StartNotifCheck = false,
            EndNotifCheck = false,
            Status = CourseStatus.Planned,
            Notes = ""
        };
        
        await DatabaseService.AddCourse(course);

        await RefreshCourseList();
    }
}