@using Microsoft.AspNetCore.WebUtilities

@inject NavigationManager Navigation

@if (IsAuthenticated)
{
    @AuthenticatedView
}
else if (IsCodeRequest)
{
    @PostAuthView
}
else
{
    if (IsAuthStateChecking)
    {
        if (Loader != null)
        {
            @Loader
        }
    }
    else
    {
        @PreAuthView
    }
}

@code
{
    [Parameter] public RenderFragment PreAuthView { get; set; }
    [Parameter] public RenderFragment PostAuthView { get; set; }
    [Parameter] public RenderFragment AuthenticatedView { get; set; }
    [Parameter] public RenderFragment? Loader { get; set; }

    [Parameter] public Func<Task<bool>> GetAuthState { get; set; }
    [Parameter] public Func<Task<string>> GetLoginUrl { get; set; }
    [Parameter] public Func<string, Task<bool>> HandleCode { get; set; }

    private bool IsAuthStateChecking = true;
    private bool IsCodeRequest = false;
    private bool IsAuthenticated = false;

    private string Code;

    protected override async Task OnAfterRenderAsync(bool firstRender)
    {
        if (!firstRender)
            return;

        await Load();
    }

    private async Task Load()
    {
        IsAuthenticated = false;
        IsAuthStateChecking = true;
        
        IsCodeRequest = HandleQueryCode();
        await InvokeAsync(StateHasChanged);

        if (IsCodeRequest)
        {
            var codeCorrect = await HandleCode.Invoke(Code);

            if (codeCorrect)
            {
                IsAuthenticated = true;
                await InvokeAsync(StateHasChanged);
                return;
            }
        }

        IsAuthenticated = await GetAuthState.Invoke();
        IsAuthStateChecking = false;
        await InvokeAsync(StateHasChanged);

        var url = await GetLoginUrl.Invoke();
        Navigation.NavigateTo(url, true);
    }

    public async Task Reload()
        => await Load();

    private bool HandleQueryCode()
    {
        var uri = new Uri(Navigation.Uri);
        var query = QueryHelpers.ParseQuery(uri.Query);

        if (!query.TryGetValue("code", out var codeValues))
            return false;

        if (codeValues.Count == 0)
            return false;

        var code = codeValues.First();

        if (string.IsNullOrEmpty(code))
            return false;

        Code = code;
        return true;
    }
}