@page "/teams/create"
@attribute [Authorize]
@using Microsoft.EntityFrameworkCore
@using WebApp.Components.Shared.Components
@using MudBlazor
@using WebApp.Services
@inject AppDbContext Context
@inject NavigationManager NavigationManager
@inject ISnackbar Snackbar
@inject FormValidationService ValidationService

@if (_events is null || _editContext is null)
{
    <p><em>Loading...</em></p>
    return;
}

<PageHeader
    Title="Create"
    Subtitle="Team"
    ShowBackButton="true"
    BackButtonUrl="@(ReturnUrl ?? "/teams")" />

<EditForm method="post" EditContext="@_editContext" OnInvalidSubmit="OnInvalidSubmit" FormName="create" Enhance>
    <FormChangeTracker @ref="_formChangeTracker" />
    <AntiforgeryToken />
    <DataAnnotationsValidator />
    
    <ValidationErrorDisplay Errors="_validationErrors" />
    
    <MudGrid>
        <MudItem xs="12" sm="7">
            <MudPaper Elevation="2" Class="pa-6">
                <MudSelect T="EventDefinition" Value="@Team.Event" ValueChanged="OnEventChanged" Label="Event">

                    @foreach (var evt in _events)
                    {
                        <MudSelectItem T="EventDefinition" Value="@(evt)"></MudSelectItem>
                    }
                </MudSelect>
                @switch (_existingTeams?.Count)
                {
                    case 1:
                        <MudAlert Severity="Severity.Info" Class="my-2">
                            A team for @Team.Event.Name already exists. This will be team 2, and the existing team will become team 1.
                        </MudAlert>
                        break;
                    case >= 2:
                        <MudAlert Severity="Severity.Error" Class="my-2">
                            Two teams for @Team.Event.Name already exist. Cannot create a third team.
                        </MudAlert>
                        break;
                }

                <MudDivider Class="my-4" />

                <StudentToggleSelector Students="@_students"
                                      @bind-SelectedStudents="_selectedStudents"
                                      Title="Students"
                                      ShowFullName="true" />

                <MudStack Class="mt-4">
                    <TeamCaptainSelector Students="@_selectedStudents"
                                        @bind-SelectedCaptain="Team.Captain"
                                        Title="Captain" />
                </MudStack>
            </MudPaper>
        </MudItem>
    </MudGrid>
    @if (!string.IsNullOrEmpty(_errorMessage))
    {
        <MudAlert Severity="Severity.Error" Class="mt-3">@_errorMessage</MudAlert>
    }
</EditForm>

<FormActions>
    <MudButton OnClick="AddTeam" Variant="Variant.Filled" Color="Color.Primary">Add</MudButton>
    <MudButton OnClick="HandleCancel" Variant="Variant.Text">Cancel</MudButton>
</FormActions>

@code {
    [SupplyParameterFromQuery]
    private string? ReturnUrl { get; set; }

    [SupplyParameterFromForm]
    private Team Team { get; set; } = new();

    private FormChangeTracker? _formChangeTracker;
    private EditContext? _editContext;
    private List<string> _validationErrors = new();
    private List<EventDefinition>? _events;
    private List<Student> _students = [];
    private IEnumerable<Student> _selectedStudents = [];
    private string? _errorMessage;
    private List<Team>? _existingTeams;

    protected override async Task OnInitializedAsync()
    {
        _events =
            await Context.Events
                .OrderBy(e => e.Name)
                .ToListAsync();

        _students = await Context.Students.ToListAsync();
        
        _editContext = new EditContext(Team);
    }

    private void OnInvalidSubmit(EditContext editContext)
    {
        _validationErrors = ValidationService.HandleInvalidSubmit(editContext, Team, errors => _validationErrors = errors);
        StateHasChanged();
    }

    private async Task OnEventChanged(EventDefinition selectedEvent)
    {
        Team.Event = selectedEvent;

        // Clear any previous error messages
        _errorMessage = null;

        // Get all existing teams for this event
        _existingTeams = await Context.Teams
            .Include(t => t.Event)
            .Where(t => t.Event.Id == selectedEvent.Id)
            .ToListAsync();
    }

    private async Task AddTeam()
    {
        // Validate before processing
        if (_editContext != null)
        {
            var errors = ValidationService.CollectValidationErrors(_editContext, Team);
            if (errors.Any())
            {
                _validationErrors = ValidationService.HandleInvalidSubmit(_editContext, Team, err => _validationErrors = err);
                StateHasChanged();
                return;
            }
        }

        _validationErrors.Clear();
        
        // Clear previous error message
        _errorMessage = null;

        try
        {
            // Get current count of teams for this event
            var existingTeamCount = await Context.Teams
                .CountAsync(t => t.Event.Id == Team.Event.Id);

            // Prohibit creation of third team
            if (existingTeamCount >= 2)
            {
                _errorMessage = $"Cannot create a third team for {Team.Event.Name}. Maximum of 2 teams allowed.";
                Snackbar.Add(_errorMessage, Severity.Error);
                return;
            }

            // Handle automatic numbering based on event format
            if (Team.Event.EventFormat == EventFormat.Individual && _selectedStudents.Count() == 1)
            {
                // For individual events, use student's first name as identifier
                var student = _selectedStudents.First();
                Team.Identifier = student.FirstName;
                Team.Captain = student;
            }
            else if (existingTeamCount == 1)
            {
                // This is the second team - assign numbers
                var existingTeam = await Context.Teams
                    .FirstOrDefaultAsync(t => t.Event.Id == Team.Event.Id);

                if (existingTeam != null)
                {
                    // Update existing team to number 1
                    existingTeam.Identifier = "1";
                    Context.Teams.Update(existingTeam);
                }

                // Set new team to number 2
                Team.Identifier = "2";
            }
            else
            {
                // This is the first team - no number
                Team.Identifier = null;
            }

            // Add selected students to the team
            foreach (var student in _selectedStudents)
            {
                Team.Students.Add(student);
            }

            Context.Teams.Add(Team);

            await Context.SaveChangesAsync();
            Snackbar.Add($"Team '{Team}' created successfully.", Severity.Success);
            _formChangeTracker?.AllowNavigation();
            NavigationManager.NavigateTo(ReturnUrl ?? "/teams");
        }
        catch (DbUpdateException ex)
        {
            ValidationService.HandleDbUpdateException(
                ex,
                "An error occurred while creating the team.",
                "team",
                "creating");
        }
        catch (Exception ex)
        {
            ValidationService.HandleException(ex);
        }
    }

    private void HandleCancel()
    {
        _formChangeTracker?.AllowNavigation();
        NavigationManager.NavigateTo(ReturnUrl ?? "/teams");
    }
}