using System.Net;
using System.Security.Claims;
using Data.SeaHavenIndustries;
using Microsoft.AspNetCore.Identity;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;
using SeaHaven.DataServices.Interfaces;
using SeaHaven.Services.Configuration;
using SeaHaven.Services.DTOs;
using SeaHaven.Services.Helpers;
using SeaHaven.Services.Interfaces;

namespace SeaHaven.Services.Implementation;

public sealed class TeamMemberInviteService : ITeamMemberInviteService
{
    /// <summary>The prototype states no lifetime; seven days is the product decision.</summary>
    public static readonly TimeSpan InviteLifetime = TimeSpan.FromDays(7);

    private readonly ITeamMemberInviteDataService _inviteDataService;
    private readonly UserManager<ApplicationUser> _userManager;
    private readonly IEmailSender _emailSender;
    private readonly FrontendOptions _frontendOptions;
    private readonly TimeProvider _timeProvider;
    private readonly ILogger<TeamMemberInviteService> _logger;

    public TeamMemberInviteService(
        ITeamMemberInviteDataService inviteDataService,
        UserManager<ApplicationUser> userManager,
        IEmailSender emailSender,
        IOptions<FrontendOptions> frontendOptions,
        TimeProvider timeProvider,
        ILogger<TeamMemberInviteService> logger)
    {
        _inviteDataService = inviteDataService;
        _userManager = userManager;
        _emailSender = emailSender;
        _frontendOptions = frontendOptions.Value;
        _timeProvider = timeProvider;
        _logger = logger;
    }

    public async Task<IssuedTeamMemberInvite> CreateAsync(string userId, CancellationToken cancellationToken)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(userId);

        var (invite, issued) = NewInvite(userId);
        await _inviteDataService.AddAsync(invite, cancellationToken);
        return issued;
    }

    public async Task<bool> SendAsync(
        IssuedTeamMemberInvite invite,
        string email,
        string name,
        CancellationToken cancellationToken)
    {
        ArgumentNullException.ThrowIfNull(invite);
        cancellationToken.ThrowIfCancellationRequested();

        var link = $"{_frontendOptions.FrontendBaseUrl?.TrimEnd('/')}/invite#{invite.Token}";
        var body =
            $"<p>Hi {WebUtility.HtmlEncode(name)},</p>" +
            "<p>You've been added to Seahaven. Set your password and confirm your email to finish creating your account.</p>" +
            // clicktracking=off stops SendGrid rewriting the link, so the token never passes through its redirect.
            $"<p><a clicktracking=off href=\"{WebUtility.HtmlEncode(link)}\">Finish registration</a></p>" +
            $"<p>This link expires in {InviteLifetime.Days} days and can be used once.</p>";

        var sent = await _emailSender.SendEmailAsync(email, "You're invited to Seahaven", body);
        if (!sent)
            _logger.LogWarning("Team member invite email could not be sent for invite expiring {ExpiresAt}.", invite.ExpiresAt);

        return sent;
    }

    public async Task<TeamMemberInviteResendOutcomeDTO> ResendAsync(
        string userId,
        ClaimsPrincipal caller,
        CancellationToken cancellationToken)
    {
        if (caller?.IsInRole("Admin") != true)
            return ResendFailure("Forbidden");

        cancellationToken.ThrowIfCancellationRequested();
        var user = await _userManager.FindByIdAsync(userId);
        if (user is null)
            return ResendFailure("Team member not found.");

        if (user.IsDeleted == true || user.PendingRegistration != true || string.IsNullOrWhiteSpace(user.Email))
            return ResendFailure("Only pending team members can be re-invited.");

        if (await ReissueAsync(user, cancellationToken) != true)
            return ResendFailure("The invite could not be emailed. Try again.");

        return new TeamMemberInviteResendOutcomeDTO { Success = true };
    }

    public async Task<bool?> ReissueAsync(ApplicationUser user, CancellationToken cancellationToken)
    {
        ArgumentNullException.ThrowIfNull(user);
        ArgumentException.ThrowIfNullOrWhiteSpace(user.Email);

        var (invite, issued) = NewInvite(user.Id);
        await _inviteDataService.ReplaceOpenForUserAsync(invite, NowUtc(), cancellationToken);

        // A deactivated member cannot register; the admin re-sends the invite after reactivating them.
        if (user.IsDeleted == true)
            return null;

        var name = $"{user.FirstName ?? ""} {user.LastName ?? ""}".Trim();
        return await SendAsync(issued, user.Email, name, cancellationToken);
    }

    private (TeamMemberInvite Invite, IssuedTeamMemberInvite Issued) NewInvite(string userId)
    {
        var now = NowUtc();
        var token = TeamMemberInviteSecrets.NewToken();
        var invite = new TeamMemberInvite
        {
            UserId = userId,
            TokenHash = TeamMemberInviteSecrets.HashToken(token),
            CreatedAt = now,
            ExpiresAt = now.Add(InviteLifetime)
        };
        return (invite, new IssuedTeamMemberInvite(token, invite.ExpiresAt));
    }

    private DateTime NowUtc() => _timeProvider.GetUtcNow().UtcDateTime;

    private static TeamMemberInviteResendOutcomeDTO ResendFailure(string error) =>
        new() { Success = false, Error = error };
}