using System.Net;
using System.Security.Cryptography;
using System.Text;
using Api.SeaHavenIndustries.Controllers;
using Api.SeaHavenIndustries.Infrastructure;
using Microsoft.Extensions.DependencyInjection;
using SeaHaven.DataServices.Interfaces;
using SeaHaven.Services.Helpers;
using SeaHaven.Services.Interfaces;

namespace SeaHavenIndustries.Tests;

/// <summary>
/// The anonymous Forgot Password flow over HTTP, against the real controller,
/// services, Identity and a relational database.
/// </summary>
public sealed class PasswordResetFlowTests
{
    private const string Alice = "alice@example.com";
    private const string Bob = "bob@example.com";
    private const string OldPassword = "Old@12345";
    private const string NewPassword = "New@67890";
    private const string CodeNotMatched = "{\"status\":\"Error\",\"message\":\"Code Not Matched\"}";
    private const string ResetFailed = "{\"status\":\"Error\",\"message\":\"Your email or code not found please check\"}";

    [Fact]
    public async Task Registered_user_resets_password_end_to_end_and_signs_in_with_the_new_one()
    {
        await using var host = await PasswordResetTestHost.StartAsync();
        await host.AddUserAsync(Alice, OldPassword);

        var requested = await host.ForgetPasswordAsync(Alice);
        Assert.Equal(HttpStatusCode.OK, requested.StatusCode);
        var code = host.Sent.LatestCodeFor(Alice);
        Assert.Matches("^[0-9]{6}$", code);

        var verified = await host.VerifyAsync(Alice, code);
        Assert.Equal(HttpStatusCode.OK, verified.StatusCode);
        Assert.Contains("Code Matched", await verified.Content.ReadAsStringAsync());

        var reset = await host.ResetAsync(Alice, code, NewPassword);
        Assert.Equal(HttpStatusCode.OK, reset.StatusCode);

        Assert.Equal(HttpStatusCode.OK, (await host.LoginAsync(Alice, NewPassword)).StatusCode);
        Assert.Equal(HttpStatusCode.Unauthorized, (await host.LoginAsync(Alice, OldPassword)).StatusCode);

        // A used code cannot be replayed.
        Assert.Equal(ResetFailed, await (await host.ResetAsync(Alice, code, "Other@24680")).Content.ReadAsStringAsync());
        Assert.Empty(await host.PendingCodesAsync());
    }

    [Fact]
    public async Task ForgetPassword_answers_registered_and_unregistered_emails_identically_and_emails_only_the_registered_one()
    {
        await using var host = await PasswordResetTestHost.StartAsync();
        await host.AddUserAsync(Alice, OldPassword);

        var registered = await host.ForgetPasswordAsync(Alice);
        var unregistered = await host.ForgetPasswordAsync("nobody@example.com");

        Assert.Equal(HttpStatusCode.OK, registered.StatusCode);
        Assert.Equal(registered.StatusCode, unregistered.StatusCode);
        Assert.Equal(await registered.Content.ReadAsStringAsync(), await unregistered.Content.ReadAsStringAsync());
        Assert.Contains(AuthenticationController.ForgetPasswordMessage, await registered.Content.ReadAsStringAsync());

        var message = Assert.Single(host.Sent.Messages);
        Assert.Equal(Alice, message.To);
        Assert.Single(await host.PendingCodesAsync(), row => row.UserId.Length > 0);
    }

    [Fact]
    public async Task ForgetPassword_hides_an_email_delivery_failure_behind_the_same_response()
    {
        await using var host = await PasswordResetTestHost.StartAsync(new ThrowingEmailSender());
        await host.AddUserAsync(Alice, OldPassword);

        var registered = await host.ForgetPasswordAsync(Alice);
        var unregistered = await host.ForgetPasswordAsync("nobody@example.com");

        Assert.Equal(HttpStatusCode.OK, registered.StatusCode);
        var body = await registered.Content.ReadAsStringAsync();
        Assert.Equal(await unregistered.Content.ReadAsStringAsync(), body);
        Assert.DoesNotContain("smtp-internal-detail", body);
        Assert.DoesNotContain(host.Logged.Lines, line => line.Contains(Alice, StringComparison.OrdinalIgnoreCase));
    }

    [Fact]
    public async Task Stored_code_is_keyed_with_a_server_secret_and_the_plaintext_is_only_in_the_email()
    {
        await using var host = await PasswordResetTestHost.StartAsync();
        await host.AddUserAsync(Alice, OldPassword);

        await host.ForgetPasswordAsync(Alice);
        var code = host.Sent.LatestCodeFor(Alice);
        var row = Assert.Single(await host.PendingCodesAsync());

        Assert.Equal(string.Empty, row.Code);
        Assert.Matches("^[0-9a-f]{32}$", row.CodeSalt);
        Assert.Matches("^[0-9a-f]{64}$", row.CodeHash);
        // Salt and hash from the row alone are not enough to test a guess offline.
        Assert.NotEqual(Sha256Hex(row.CodeSalt + ":" + code), row.CodeHash);
        Assert.Equal(
            PasswordResetCodeSecrets.Hash(PasswordResetCodeSecrets.DeriveKey(PasswordResetTestHost.JwtSecret), row.CodeSalt, code),
            row.CodeHash);
        Assert.DoesNotContain(code, string.Join("|", row.Code, row.CodeHash, row.CodeSalt, row.Email, row.UserId));
    }

    [Fact]
    public async Task Code_expires_fifteen_minutes_after_it_is_issued()
    {
        await using var host = await PasswordResetTestHost.StartAsync();
        await host.AddUserAsync(Alice, OldPassword);
        await host.ForgetPasswordAsync(Alice);
        var code = host.Sent.LatestCodeFor(Alice);

        host.Time.Advance(TimeSpan.FromMinutes(15) - TimeSpan.FromSeconds(1));
        Assert.Equal(HttpStatusCode.OK, (await host.VerifyAsync(Alice, code)).StatusCode);

        host.Time.Advance(TimeSpan.FromSeconds(1));
        Assert.Equal(CodeNotMatched, await (await host.VerifyAsync(Alice, code)).Content.ReadAsStringAsync());
        Assert.Equal(ResetFailed, await (await host.ResetAsync(Alice, code, NewPassword)).Content.ReadAsStringAsync());
        Assert.Equal(HttpStatusCode.OK, (await host.LoginAsync(Alice, OldPassword)).StatusCode);
    }

    [Fact]
    public async Task Requesting_a_new_code_invalidates_the_previous_one()
    {
        await using var host = await PasswordResetTestHost.StartAsync();
        await host.AddUserAsync(Alice, OldPassword);

        await host.ForgetPasswordAsync(Alice);
        var first = host.Sent.LatestCodeFor(Alice);
        string second;
        do
        {
            await host.ForgetPasswordAsync(Alice);
            second = host.Sent.LatestCodeFor(Alice);
        }
        while (second == first);

        Assert.Equal(CodeNotMatched, await (await host.VerifyAsync(Alice, first)).Content.ReadAsStringAsync());
        Assert.Single(await host.PendingCodesAsync());
        Assert.Equal(HttpStatusCode.OK, (await host.ResetAsync(Alice, second, NewPassword)).StatusCode);
    }

    [Fact]
    public async Task Five_wrong_attempts_invalidate_the_code_until_a_new_one_is_requested()
    {
        await using var host = await PasswordResetTestHost.StartAsync();
        await host.AddUserAsync(Alice, OldPassword);
        await host.ForgetPasswordAsync(Alice);
        var code = host.Sent.LatestCodeFor(Alice);
        var wrong = WrongCode(code);

        // Verify and reset share one attempt budget.
        for (var attempt = 0; attempt < 3; attempt++)
            Assert.Equal(CodeNotMatched, await (await host.VerifyAsync(Alice, wrong)).Content.ReadAsStringAsync());
        for (var attempt = 0; attempt < 2; attempt++)
            Assert.Equal(ResetFailed, await (await host.ResetAsync(Alice, wrong, NewPassword)).Content.ReadAsStringAsync());

        Assert.Equal(CodeNotMatched, await (await host.VerifyAsync(Alice, code)).Content.ReadAsStringAsync());
        Assert.Equal(ResetFailed, await (await host.ResetAsync(Alice, code, NewPassword)).Content.ReadAsStringAsync());
        Assert.Empty(await host.PendingCodesAsync());
        Assert.Equal(HttpStatusCode.OK, (await host.LoginAsync(Alice, OldPassword)).StatusCode);

        await host.ForgetPasswordAsync(Alice);
        Assert.Equal(HttpStatusCode.OK, (await host.ResetAsync(Alice, host.Sent.LatestCodeFor(Alice), NewPassword)).StatusCode);
    }

    [Fact]
    public async Task Exhausting_a_code_invalidates_every_pending_code_for_that_email()
    {
        await using var host = await PasswordResetTestHost.StartAsync();
        var user = await host.AddUserAsync(Alice, OldPassword);
        await host.ForgetPasswordAsync(Alice);
        var older = host.Sent.LatestCodeFor(Alice);
        var newest = await host.AddSiblingCodeAsync(Alice, user.Id);

        for (var attempt = 0; attempt < 5; attempt++)
            await host.VerifyAsync(Alice, WrongCode(newest));

        Assert.Empty(await host.PendingCodesAsync());
        Assert.Equal(ResetFailed, await (await host.ResetAsync(Alice, older, NewPassword)).Content.ReadAsStringAsync());
    }

    [Fact]
    public async Task A_successful_reset_invalidates_every_pending_code_for_that_email()
    {
        await using var host = await PasswordResetTestHost.StartAsync();
        var user = await host.AddUserAsync(Alice, OldPassword);
        await host.ForgetPasswordAsync(Alice);
        var older = host.Sent.LatestCodeFor(Alice);
        var newest = await host.AddSiblingCodeAsync(Alice, user.Id);

        Assert.Equal(HttpStatusCode.OK, (await host.ResetAsync(Alice, newest, NewPassword)).StatusCode);

        Assert.Empty(await host.PendingCodesAsync());
        Assert.Equal(ResetFailed, await (await host.ResetAsync(Alice, older, "Other@24680")).Content.ReadAsStringAsync());
    }

    [Fact]
    public async Task Four_wrong_attempts_then_the_right_code_still_resets()
    {
        await using var host = await PasswordResetTestHost.StartAsync();
        await host.AddUserAsync(Alice, OldPassword);
        await host.ForgetPasswordAsync(Alice);
        var code = host.Sent.LatestCodeFor(Alice);

        for (var attempt = 0; attempt < 4; attempt++)
            Assert.Equal(CodeNotMatched, await (await host.VerifyAsync(Alice, WrongCode(code))).Content.ReadAsStringAsync());

        // A correct verify does not spend an attempt, so the reset after it still succeeds.
        Assert.Equal(HttpStatusCode.OK, (await host.VerifyAsync(Alice, code)).StatusCode);
        Assert.Equal(HttpStatusCode.OK, (await host.ResetAsync(Alice, code, NewPassword)).StatusCode);
    }

    [Fact]
    public async Task A_rejected_new_password_does_not_spend_an_attempt_or_the_code()
    {
        await using var host = await PasswordResetTestHost.StartAsync();
        await host.AddUserAsync(Alice, OldPassword);
        await host.ForgetPasswordAsync(Alice);
        var code = host.Sent.LatestCodeFor(Alice);

        for (var attempt = 0; attempt < 6; attempt++)
            Assert.Equal(ResetFailed, await (await host.ResetAsync(Alice, code, "weakpassword")).Content.ReadAsStringAsync());

        Assert.Equal(HttpStatusCode.OK, (await host.ResetAsync(Alice, code, NewPassword)).StatusCode);
    }

    [Fact]
    public async Task A_code_is_checked_only_against_the_email_it_was_issued_to()
    {
        await using var host = await PasswordResetTestHost.StartAsync();
        await host.AddUserAsync(Alice, OldPassword);
        await host.AddUserAsync(Bob, OldPassword);
        await host.ForgetPasswordAsync(Alice);
        await host.ForgetPasswordAsync(Bob);
        var aliceCode = host.Sent.LatestCodeFor(Alice);
        var bobCode = host.Sent.LatestCodeFor(Bob);

        if (aliceCode != bobCode)
        {
            Assert.Equal(CodeNotMatched, await (await host.VerifyAsync(Bob, aliceCode)).Content.ReadAsStringAsync());
            Assert.Equal(ResetFailed, await (await host.ResetAsync(Bob, aliceCode, NewPassword)).Content.ReadAsStringAsync());
        }

        // Exhausting Bob's attempts leaves Alice's code and budget untouched.
        for (var attempt = 0; attempt < 5; attempt++)
            await host.VerifyAsync(Bob, WrongCode(bobCode));

        var alice = Assert.Single(await host.PendingCodesAsync());
        Assert.Equal(Alice, alice.Email);
        Assert.Equal(0, alice.FailedAttempts);
        Assert.Equal(HttpStatusCode.OK, (await host.ResetAsync(Alice, aliceCode, NewPassword)).StatusCode);
        Assert.Equal(HttpStatusCode.OK, (await host.LoginAsync(Bob, OldPassword)).StatusCode);
    }

    [Fact]
    public async Task Concurrent_checks_can_never_consume_more_than_five_attempts()
    {
        await using var host = await PasswordResetTestHost.StartAsync();
        await host.AddUserAsync(Alice, OldPassword);
        await host.ForgetPasswordAsync(Alice);
        var row = Assert.Single(await host.PendingCodesAsync());
        var now = host.Time.GetUtcNow().UtcDateTime;

        var results = await Task.WhenAll(Enumerable.Range(0, 20).Select(async _ =>
        {
            await using var scope = host.Services.CreateAsyncScope();
            return await scope.ServiceProvider.GetRequiredService<IForgetPasswordDataService>()
                .TryConsumeAttemptAsync(row.Id, 5, now, CancellationToken.None);
        }));

        Assert.Equal(5, results.Count(consumed => consumed));
        Assert.Equal(5, Assert.Single(await host.PendingCodesAsync()).FailedAttempts);
    }

    [Fact]
    public async Task VerificationCode_without_an_email_fails_generically_and_never_matches_another_users_code()
    {
        await using var host = await PasswordResetTestHost.StartAsync();
        await host.AddUserAsync(Alice, OldPassword);
        await host.ForgetPasswordAsync(Alice);
        var code = host.Sent.LatestCodeFor(Alice);

        // The old client contract: code in the query string, no body, no content type.
        var legacy = await host.Client.SendAsync(PasswordResetTestHost.Post($"api/Authentication/VerificationCode?code={code}"));

        Assert.Equal(HttpStatusCode.BadRequest, legacy.StatusCode);
        Assert.Equal(CodeNotMatched, await legacy.Content.ReadAsStringAsync());
        Assert.Equal(0, Assert.Single(await host.PendingCodesAsync()).FailedAttempts);
    }

    [Fact]
    public async Task Email_and_code_in_the_query_string_are_ignored()
    {
        await using var host = await PasswordResetTestHost.StartAsync();
        await host.AddUserAsync(Alice, OldPassword);

        var queryRequest = await host.Client.SendAsync(PasswordResetTestHost.Post($"api/Authentication/ForgetPassword?Email={Uri.EscapeDataString(Alice)}"));
        await host.WaitForEmailDrainAsync();
        var bodyRequest = await host.ForgetPasswordAsync("nobody@example.com");
        Assert.Equal(HttpStatusCode.OK, queryRequest.StatusCode);
        Assert.Equal(await bodyRequest.Content.ReadAsStringAsync(), await queryRequest.Content.ReadAsStringAsync());
        Assert.Empty(host.Sent.Messages);

        await host.ForgetPasswordAsync(Alice);
        var code = host.Sent.LatestCodeFor(Alice);
        var verified = await host.Client.SendAsync(PasswordResetTestHost.Post(
            $"api/Authentication/VerificationCode?email={Uri.EscapeDataString(Alice)}&code={code}"));

        Assert.Equal(HttpStatusCode.BadRequest, verified.StatusCode);
        Assert.Equal(CodeNotMatched, await verified.Content.ReadAsStringAsync());
    }

    [Fact]
    public async Task Each_endpoint_allows_ten_requests_per_client_per_window_then_answers_429()
    {
        await using var host = await PasswordResetTestHost.StartAsync();
        const string client = "203.0.113.5";

        for (var request = 0; request < PasswordResetRateLimiting.PermitLimit; request++)
            Assert.Equal(HttpStatusCode.OK, (await host.ForgetPasswordAsync($"n{request}@example.com", client)).StatusCode);

        var limited = await host.ForgetPasswordAsync("n@example.com", client);
        Assert.Equal(HttpStatusCode.TooManyRequests, limited.StatusCode);
        Assert.Equal(
            "{\"status\":\"Error\",\"message\":\"Too many requests. Please try again later.\"}",
            await limited.Content.ReadAsStringAsync());

        // A left-hand X-Forwarded-For entry written by the caller does not buy a new bucket.
        Assert.Equal(HttpStatusCode.TooManyRequests, (await host.ForgetPasswordAsync("n@example.com", "198.51.100.1, " + client)).StatusCode);

        // Another client, and the same client on another endpoint, are unaffected.
        Assert.Equal(HttpStatusCode.OK, (await host.ForgetPasswordAsync("n@example.com", "203.0.113.6")).StatusCode);
        Assert.Equal(HttpStatusCode.BadRequest, (await host.VerifyAsync("n@example.com", "000000", client)).StatusCode);
    }

    [Theory]
    [InlineData("api/Authentication/VerificationCode")]
    [InlineData("api/Authentication/ResetPassword")]
    public async Task Verify_and_reset_are_rate_limited_per_client(string path)
    {
        await using var host = await PasswordResetTestHost.StartAsync();
        const string client = "203.0.113.9";
        var body = new { email = Alice, code = "000000", password = NewPassword };

        for (var request = 0; request < PasswordResetRateLimiting.PermitLimit; request++)
            Assert.Equal(HttpStatusCode.BadRequest, (await host.Client.SendAsync(PasswordResetTestHost.Post(path, body, client))).StatusCode);

        Assert.Equal(HttpStatusCode.TooManyRequests, (await host.Client.SendAsync(PasswordResetTestHost.Post(path, body, client))).StatusCode);
    }

    [Fact]
    public async Task No_code_or_email_reaches_the_logs_during_the_whole_flow()
    {
        await using var host = await PasswordResetTestHost.StartAsync();
        await host.AddUserAsync(Alice, OldPassword);

        await host.ForgetPasswordAsync(Alice);
        await host.ForgetPasswordAsync("nobody@example.com");
        var code = host.Sent.LatestCodeFor(Alice);
        await host.VerifyAsync(Alice, WrongCode(code));
        await host.VerifyAsync(Alice, code);
        await host.ResetAsync(Alice, code, NewPassword);

        Assert.NotEmpty(host.Logged.Lines);
        Assert.DoesNotContain(host.Logged.Lines, line => line.Contains(code, StringComparison.Ordinal));
        Assert.DoesNotContain(host.Logged.Lines, line => line.Contains(WrongCode(code), StringComparison.Ordinal));
        Assert.DoesNotContain(host.Logged.Lines, line => line.Contains("@example.com", StringComparison.OrdinalIgnoreCase));
        Assert.DoesNotContain(host.Logged.Lines, line => line.Contains(NewPassword, StringComparison.Ordinal));
    }

    [Fact]
    public void Api_host_registers_forwarded_headers_and_rate_limiting_in_the_right_order()
    {
        var program = File.ReadAllText(Path.Combine(RepoRoot(), "Api.SeaHavenIndustries", "Program.cs"));

        Assert.Contains("builder.Services.AddPasswordResetRateLimiting();", program);
        Assert.Contains("builder.Services.AddPasswordResetEmailDelivery();", program);
        var build = program.IndexOf("builder.Build()", StringComparison.Ordinal);
        var forwarded = program.IndexOf("app.UseForwardedHeaders()", StringComparison.Ordinal);
        var firstMiddleware = program.IndexOf("app.Use", build, StringComparison.Ordinal);
        var routing = program.IndexOf("app.UseRouting()", StringComparison.Ordinal);
        var limiter = program.IndexOf("app.UseRateLimiter()", StringComparison.Ordinal);
        var controllers = program.IndexOf("app.MapControllers()", StringComparison.Ordinal);

        Assert.True(forwarded > build && forwarded == firstMiddleware, "UseForwardedHeaders must be the first middleware.");
        Assert.True(routing < limiter, "UseRateLimiter must run after UseRouting so endpoint policies apply.");
        Assert.True(limiter < controllers);
    }

    private static string WrongCode(string code) =>
        ((int.Parse(code) + 1) % 1_000_000).ToString("D6");

    private static string Sha256Hex(string value) =>
        Convert.ToHexString(SHA256.HashData(Encoding.UTF8.GetBytes(value))).ToLowerInvariant();

    private static string RepoRoot()
    {
        var directory = new DirectoryInfo(AppContext.BaseDirectory);
        while (directory is not null
            && !File.Exists(Path.Combine(directory.FullName, "Api.SeaHavenIndustries", "Program.cs")))
        {
            directory = directory.Parent;
        }

        return directory?.FullName
            ?? throw new InvalidOperationException("Could not locate the repository root from " + AppContext.BaseDirectory);
    }

    private sealed class ThrowingEmailSender : IEmailSender
    {
        public Task<bool> SendEmailAsync(string emailTo, string subject, string body) =>
            throw new InvalidOperationException("smtp-internal-detail " + emailTo);
    }
}