using System.Net;
using System.Text;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Core.Abstractions;

namespace ZB.MOM.WW.OtOpcUa.Driver.MTConnect.Tests;

/// <summary>
///     Gitea #804 — the gaps a parity review against the ignitionoee Java MTConnect driver verified in this
///     driver, one region per gap. Each test failed against the pre-#804 driver; the capability matrix that
///     says which Java behaviours were already covered (and by which existing tests) is
///     <c>docs/drivers/MTConnect.md</c> §"Java reference parity (#804)".
/// </summary>
public sealed class MTConnectJavaParityTests
{
    private static CancellationToken Ct => TestContext.Current.CancellationToken;

    private const string OutOfRangeError =
        """
        <?xml version="1.0" encoding="UTF-8"?>
        <MTConnectError xmlns="urn:mtconnect.org:MTConnectError:2.0">
          <Header creationTime="2026-11-10T12:00:00Z" sender="agent" instanceId="1" version="2.7.0.12" bufferSize="16384"/>
          <Errors>
            <Error errorCode="OUT_OF_RANGE">'from' must be greater than 59962705</Error>
          </Errors>
        </MTConnectError>
        """;

    private const string NoDeviceError =
        """
        <MTConnectError xmlns="urn:mtconnect.org:MTConnectError:2.0">
          <Errors><Error errorCode="NO_DEVICE">Could not find the device 'nosuch'</Error></Errors>
        </MTConnectError>
        """;

    private static MTConnectAgentClient NewClient(HttpMessageHandler handler) =>
        new(new MTConnectDriverOptions { AgentUri = "http://agent:5000", RequestTimeoutMs = 5000 }, handler);

    private static async Task DrainAsync(IAsyncEnumerable<MTConnectStreamsResult> stream)
    {
        await foreach (var _ in stream)
        {
        }
    }

    // ───────────── gap 1: an Agent error document under a non-2xx status is the Agent's refusal ─────────────
    // cppagent 2.x (the fixture's mtconnect/agent:2.7, verified live) answers an evicted `from` and a count at or
    // above its buffer with HTTP 400 + MTConnectError OUT_OF_RANGE. Pre-#804 the client threw a bare
    // HttpRequestException, which the pump treats as a transient transport loss: it reconnected at the SAME
    // evicted cursor for ever and the OUT_OF_RANGE re-baseline never ran against a real 2.x Agent.

    [Fact]
    public async Task Sample_answered_400_with_an_out_of_range_document_surfaces_as_the_agents_refusal()
    {
        using var client = NewClient(new StubHandler(_ => Respond(HttpStatusCode.BadRequest, OutOfRangeError)));

        var ex = await Should.ThrowAsync<InvalidDataException>(async () => await DrainAsync(client.SampleAsync(1, Ct)));

        ex.Message.ShouldContain("OUT_OF_RANGE: 'from' must be greater than 59962705");
        ex.Message.ShouldContain("HTTP 400");
        MTConnectXml.IsAgentRefusal(ex).ShouldBeTrue();
    }

    [Fact]
    public async Task Current_answered_404_with_a_no_device_document_is_an_agent_refusal_not_a_comms_fault()
    {
        using var client = NewClient(new StubHandler(_ => Respond(HttpStatusCode.NotFound, NoDeviceError)));

        var ex = await Should.ThrowAsync<InvalidDataException>(() => client.CurrentAsync(Ct));

        ex.Message.ShouldContain("NO_DEVICE");
        MTConnectXml.IsAgentRefusal(ex).ShouldBeTrue();
    }

    [Fact]
    public async Task Probe_answered_404_with_an_error_document_carries_the_agents_own_words()
    {
        using var client = NewClient(new StubHandler(_ => Respond(HttpStatusCode.NotFound, NoDeviceError)));

        var ex = await Should.ThrowAsync<InvalidDataException>(() => client.ProbeAsync(Ct));

        ex.Message.ShouldContain("Could not find the device 'nosuch'");
        ex.Message.ShouldContain("expected <MTConnectDevices>");
    }

    /// <summary>Positive control: a non-2xx body that is NOT an MTConnect error document keeps the status-only failure.</summary>
    [Fact]
    public async Task A_non_2xx_proxy_page_is_still_a_plain_http_failure()
    {
        using var client = NewClient(new StubHandler(_ => Respond(HttpStatusCode.BadGateway, "<html><body>502</body></html>")));

        await Should.ThrowAsync<HttpRequestException>(() => client.CurrentAsync(Ct));
    }

    /// <summary>The failure body is read only up to the cap: a huge error page never becomes a huge string.</summary>
    [Fact]
    public async Task An_error_document_beyond_the_body_cap_is_not_read_in_full()
    {
        var padding = new string(' ', 70 * 1024); // past the 64 KiB failure-body cap
        using var client = NewClient(new StubHandler(_ => Respond(HttpStatusCode.BadRequest, padding + OutOfRangeError)));

        // The document starts past the cap, so it is never seen: status-only failure, not a refusal.
        await Should.ThrowAsync<HttpRequestException>(async () => await DrainAsync(client.SampleAsync(1, Ct)));
    }

    // ───────────── gap 2 (driver-level, MTConnectSubscribeTests): repeated re-baselines without progress ─────────────

    // ───────────── gap 3: streams parser nesting bound ─────────────
    // ReadElement/ReadChildren recurse per nesting level; an unbounded depth from an unauthenticated peer is a
    // StackOverflowException, which .NET cannot catch — the whole server process dies.

    private static string Streams(string body) =>
        $"""
         <MTConnectStreams xmlns="urn:mtconnect.org:MTConnectStreams:2.0">
           <Header creationTime="2026-11-10T12:00:00Z" instanceId="1" bufferSize="16" firstSequence="1" lastSequence="5" nextSequence="6"/>
           <Streams>{body}</Streams>
         </MTConnectStreams>
         """;

    [Fact]
    public void Streams_parse_refuses_absurd_nesting_instead_of_recursing_without_bound()
    {
        const int depth = 80; // beyond the 64-level bound
        var xml = Streams(string.Concat(Enumerable.Repeat("<x>", depth)) + string.Concat(Enumerable.Repeat("</x>", depth)));

        var ex = Should.Throw<InvalidDataException>(() => MTConnectStreamsParser.Parse(xml));

        ex.Message.ShouldContain("levels deep");
    }

    /// <summary>Positive control: a real document's nesting (with a TABLE's Entry/Cell) parses under the bound.</summary>
    [Fact]
    public void Streams_parse_accepts_ordinary_device_nesting()
    {
        var xml = Streams(
            """
            <DeviceStream name="d" uuid="u"><ComponentStream component="Path" componentId="p">
              <Events>
                <WorkOffsetTable dataItemId="wo" timestamp="2026-11-10T12:00:00Z" sequence="5" count="1">
                  <Entry key="G54"><Cell key="X">1.0</Cell></Entry>
                </WorkOffsetTable>
                <Execution dataItemId="exec" timestamp="2026-11-10T12:00:00Z" sequence="4">ACTIVE</Execution>
              </Events>
            </ComponentStream></DeviceStream>
            """);

        var result = MTConnectStreamsParser.Parse(xml);

        result.Observations.Select(o => o.DataItemId).ShouldBe(["wo", "exec"]);
    }

    // ───────────── gap 4: DOCTYPE refused on every tree-building parse ─────────────
    // The streams parser already prohibited DTDs; the /probe parse (and the write-answer parse) went through
    // XDocument.Parse, which PARSES a DTD and expands its internal entities.

    private const string ProbeWithDoctype =
        """
        <?xml version="1.0"?>
        <!DOCTYPE MTConnectDevices [ <!ENTITY injected "Injected"> ]>
        <MTConnectDevices xmlns="urn:mtconnect.org:MTConnectDevices:2.0">
          <Header instanceId="1"/>
          <Devices><Device id="d1" name="&injected;"><DataItems><DataItem id="a" category="EVENT" type="AVAILABILITY"/></DataItems></Device></Devices>
        </MTConnectDevices>
        """;

    [Fact]
    public void Probe_parse_refuses_a_doctype_from_a_string()
    {
        var ex = Should.Throw<InvalidDataException>(() => MTConnectProbeParser.Parse(ProbeWithDoctype));

        ex.Message.ShouldContain("not well-formed XML");
    }

    [Fact]
    public void Probe_parse_refuses_a_doctype_from_a_stream()
    {
        using var stream = new MemoryStream(Encoding.UTF8.GetBytes(ProbeWithDoctype));

        Should.Throw<InvalidDataException>(() => MTConnectProbeParser.Parse(stream));
    }

    /// <summary>A write answered with a DOCTYPE'd document cannot be read, so it is NOT reported as accepted.</summary>
    [Fact]
    public async Task A_write_answered_with_a_doctype_document_is_not_confirmed()
    {
        const string body =
            """
            <!DOCTYPE MTConnectError [ <!ENTITY e "x"> ]>
            <MTConnectError><Errors><Error errorCode="UNSUPPORTED">&e;</Error></Errors></MTConnectError>
            """;
        using var client = NewClient(new StubHandler(_ => Respond(HttpStatusCode.OK, body)));

        var outcome = await client.WriteObservationAsync("d", "item", "v", Ct);

        outcome.Accepted.ShouldBeFalse();
        outcome.AgentError.ShouldNotBeNull().ShouldContain("DOCTYPE");
    }

    // ───────────── gap 5: no fabricated non-finite floats ─────────────
    // .NET parses an overflowing literal to ±Infinity and accepts NaN/Infinity spellings; all were Good.

    [Theory]
    [InlineData(DriverDataType.Float64, "1e400", 0x803C0000u)]    // BadOutOfRange — a number the type cannot hold
    [InlineData(DriverDataType.Float64, "-1e400", 0x803C0000u)]
    [InlineData(DriverDataType.Float32, "1e39", 0x803C0000u)]     // fits a double, overflows a float
    [InlineData(DriverDataType.Float64, "NaN", 0x80740000u)]      // BadTypeMismatch — not a measurement
    [InlineData(DriverDataType.Float64, "Infinity", 0x80740000u)]
    [InlineData(DriverDataType.Float32, "-Infinity", 0x80740000u)]
    public void A_non_finite_float_is_never_served_as_good(DriverDataType type, string text, uint expected)
    {
        var snap = Coerce(type, text);

        snap.StatusCode.ShouldBe(expected);
        snap.Value.ShouldBeNull();
    }

    // ───────────── gap 6: an integer-valued decimal on an integral tag ─────────────
    // Agents format integer-valued items as "42.000000"; that was BadOutOfRange on every integral tag.

    [Theory]
    [InlineData(DriverDataType.Int32, "42.000000", 42)]
    [InlineData(DriverDataType.Int64, "1.5e3", 1500L)]
    [InlineData(DriverDataType.Int16, "-7.0", (short)-7)]
    [InlineData(DriverDataType.UInt32, "4000000000.0", 4000000000u)]
    public void An_integer_valued_decimal_converts_losslessly(DriverDataType type, string text, object expected)
    {
        var snap = Coerce(type, text);

        snap.StatusCode.ShouldBe(0u);
        snap.Value.ShouldBe(expected);
    }

    /// <summary>…but a REAL fraction is still refused, never truncated (deliberately stricter than the Java driver).</summary>
    [Theory]
    [InlineData(DriverDataType.Int32, "42.5")]
    [InlineData(DriverDataType.Int16, "40000.0")]
    [InlineData(DriverDataType.UInt16, "-1.0")]
    [InlineData(DriverDataType.Int64, "1e30")]
    public void A_fraction_or_an_out_of_range_decimal_stays_out_of_range(DriverDataType type, string text)
    {
        var snap = Coerce(type, text);

        snap.StatusCode.ShouldBe(0x803C0000u);
        snap.Value.ShouldBeNull();
    }

    private static DataValueSnapshot Coerce(DriverDataType type, string text)
    {
        var index = new MTConnectObservationIndex([new MTConnectTagDefinition("x", type)]);
        index.Apply(new MTConnectStreamsResult(
            1L, 2L, 1L, [new MTConnectObservation("x", text, new DateTime(2026, 11, 10, 12, 0, 0, DateTimeKind.Utc))]));

        return index.Get("x");
    }

    // ───────────── gap 7: sibling containers resolving to one folder name ─────────────
    // Two same-named sibling folders share one path key in the browse picker; the second one's data items were
    // listed but unreachable on expand. Merged into ONE folder (what the Java driver does).

    private const string CollidingProbe =
        """
        <MTConnectDevices xmlns="urn:mtconnect.org:MTConnectDevices:2.0">
          <Header instanceId="1"/>
          <Devices>
            <Device id="d1" name="Mill">
              <Components>
                <Axes id="ax" name="Axes">
                  <Components>
                    <Rotary id="c_rot" name="C"><DataItems><DataItem id="c_angle" category="SAMPLE" type="ANGLE"/></DataItems></Rotary>
                    <Linear id="c_lin" name="C"><DataItems><DataItem id="c_pos" category="SAMPLE" type="POSITION"/></DataItems></Linear>
                    <Linear id="X"><DataItems><DataItem id="x_pos" category="SAMPLE" type="POSITION"/></DataItems></Linear>
                    <Linear id="x2" name="X"><DataItems><DataItem id="x2_pos" category="SAMPLE" type="POSITION"/></DataItems></Linear>
                  </Components>
                </Axes>
              </Components>
            </Device>
          </Devices>
        </MTConnectDevices>
        """;

    [Fact]
    public async Task Sibling_components_resolving_to_one_name_share_one_folder_and_keep_every_data_item()
    {
        var client = CannedAgentClient.FromFixtures();
        client.Probe = MTConnectProbeParser.Parse(CollidingProbe);
        var driver = new MTConnectDriver(new MTConnectDriverOptions { AgentUri = "http://agent:5000" }, "mt1", _ => client);
        await driver.InitializeAsync("{}", Ct);

        var cap = new CapturingBuilder();
        await driver.DiscoverAsync(cap, Ct);

        cap.Folders.Select(f => f.Path).ShouldBe(["Mill", "Mill/Axes", "Mill/Axes/C", "Mill/Axes/X"]);
        cap.Variables.Single(v => v.Attr.FullName == "c_angle").ParentPath.ShouldBe("Mill/Axes/C");
        cap.Variables.Single(v => v.Attr.FullName == "c_pos").ParentPath.ShouldBe("Mill/Axes/C");
        cap.Variables.Single(v => v.Attr.FullName == "x_pos").ParentPath.ShouldBe("Mill/Axes/X");   // id fallback
        cap.Variables.Single(v => v.Attr.FullName == "x2_pos").ParentPath.ShouldBe("Mill/Axes/X");  // name
    }

    // ───────────── gap 8: structural elements are not components ─────────────

    [Fact]
    public void A_structural_element_under_components_or_devices_is_skipped_not_fatal()
    {
        const string xml =
            """
            <MTConnectDevices xmlns="urn:mtconnect.org:MTConnectDevices:2.0">
              <Header instanceId="1"/>
              <Devices>
                <Description>agent-wide note</Description>
                <Device id="d1" name="Mill">
                  <Components>
                    <Description>stray, schema-invalid</Description>
                    <Controller id="ctl"><DataItems><DataItem id="mode" category="EVENT" type="CONTROLLER_MODE"/></DataItems></Controller>
                  </Components>
                </Device>
              </Devices>
            </MTConnectDevices>
            """;

        var model = MTConnectProbeParser.Parse(xml);

        model.Devices.ShouldHaveSingleItem().Components.ShouldHaveSingleItem().Id.ShouldBe("ctl");
    }

    // ───────────── plumbing ─────────────

    private static HttpResponseMessage Respond(HttpStatusCode status, string body) =>
        new(status) { Content = new StringContent(body, Encoding.UTF8, "application/xml") };

    private sealed class StubHandler(Func<HttpRequestMessage, HttpResponseMessage> respond) : HttpMessageHandler
    {
        protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken ct) =>
            Task.FromResult(respond(request));
    }

    // ───────────── Java regression scenarios this driver already met (coverage, not gaps) ─────────────
    // Ported from the Java MTConnectMultipartReaderTest / MTConnectStreamsParserTest cases that had no
    // .NET counterpart. Each passed before #804; they pin behaviour the matrix records as "covered".

    private static string Doc(long first, long next, string observations = "") => Streams(
        $"""<DeviceStream name="d"><ComponentStream component="Path" componentId="p"><Events>{observations}</Events></ComponentStream></DeviceStream>""")
        .Replace("firstSequence=\"1\"", $"firstSequence=\"{first}\"").Replace("nextSequence=\"6\"", $"nextSequence=\"{next}\"");

    private static HttpResponseMessage MultipartResponse(byte[] body) => MultipartResponse(new ByteArrayContent(body));

    private static HttpResponseMessage MultipartResponse(HttpContent content)
    {
        content.Headers.ContentType =
            System.Net.Http.Headers.MediaTypeHeaderValue.Parse("multipart/x-mixed-replace; boundary=b0");

        return new HttpResponseMessage(HttpStatusCode.OK) { Content = content };
    }

    private static async Task<List<MTConnectStreamsResult>> CollectAsync(MTConnectAgentClient client, int count)
    {
        var results = new List<MTConnectStreamsResult>();
        await foreach (var chunk in client.SampleAsync(1, Ct))
        {
            results.Add(chunk);
            if (results.Count == count)
            {
                break;
            }
        }

        return results;
    }

    /// <summary>Java <c>contentLengthIsHonoredOverBoundaryScanning</c>: a document whose text contains the boundary token is returned whole.</summary>
    [Fact]
    public async Task A_declared_content_length_is_authoritative_over_a_boundary_token_inside_the_document()
    {
        var doc = Doc(1, 2, "<Message dataItemId=\"m\" timestamp=\"2026-11-10T12:00:00Z\">see\r\n--b0 inside the text</Message>");
        var payload = Encoding.UTF8.GetBytes(doc);
        var body = Encoding.ASCII.GetBytes($"--b0\r\nContent-type: text/xml\r\nContent-length: {payload.Length}\r\n\r\n")
            .Concat(payload).Concat("\r\n--b0--\r\n"u8.ToArray()).ToArray();
        using var client = NewClient(new StubHandler(_ => MultipartResponse(body)));

        var chunk = (await CollectAsync(client, 1)).ShouldHaveSingleItem();

        chunk.Observations.ShouldHaveSingleItem().Value.ShouldContain("--b0 inside the text");
    }

    /// <summary>Java <c>preambleBeforeTheFirstBoundaryIsSkipped</c> + <c>lineFeedOnlyFramingIsAccepted</c>.</summary>
    [Fact]
    public async Task A_preamble_is_skipped_and_line_feed_only_framing_is_accepted()
    {
        var first = Encoding.UTF8.GetBytes(Doc(1, 2));
        var second = Encoding.UTF8.GetBytes(Doc(2, 3));
        var body = Encoding.ASCII.GetBytes("this is preamble text\n--b0\nContent-length: " + first.Length + "\n\n")
            .Concat(first)
            .Concat(Encoding.ASCII.GetBytes("\n--b0\nContent-length: " + second.Length + "\n\n"))
            .Concat(second)
            .Concat("\n--b0--\n"u8.ToArray()).ToArray();
        using var client = NewClient(new StubHandler(_ => MultipartResponse(body)));

        var chunks = await CollectAsync(client, 2);

        chunks.Select(c => c.NextSequence).ShouldBe([2L, 3L]);
    }

    /// <summary>Java <c>aBodyShorterThanItsDeclaredContentLengthThrows</c>: truncation is a lost stream, never an orderly end.</summary>
    [Fact]
    public async Task A_part_shorter_than_its_declared_content_length_is_a_lost_stream()
    {
        var payload = Encoding.UTF8.GetBytes(Doc(1, 2));
        var body = Encoding.ASCII.GetBytes($"--b0\r\nContent-length: {payload.Length + 500}\r\n\r\n").Concat(payload).ToArray();
        using var client = NewClient(new StubHandler(_ => MultipartResponse(body)));

        await Should.ThrowAsync<MTConnectStreamEndedException>(async () => await DrainAsync(client.SampleAsync(1, Ct)));
    }

    /// <summary>Java <c>aPartLargerThanTheBufferCapIsRefused</c>: a peer that never frames a part cannot grow the buffer unbounded.</summary>
    [Fact]
    public async Task A_part_larger_than_the_buffer_cap_is_refused()
    {
        var head = "--b0\r\nContent-type: text/xml\r\n\r\n"u8.ToArray();
        using var client = NewClient(new StubHandler(_ => MultipartResponse(new StreamContent(new EndlessPart(head)))));

        var ex = await Should.ThrowAsync<InvalidDataException>(async () => await DrainAsync(client.SampleAsync(1, Ct)));

        ex.Message.ShouldContain("refusing to buffer further");
    }

    /// <summary>Java <c>timestampWithANonZuluOffsetIsNormalizedToTheSameInstant</c>: the SourceTimestamp is the Agent's instant, in UTC.</summary>
    [Fact]
    public void A_timestamp_with_a_non_zulu_offset_is_normalized_to_the_same_utc_instant()
    {
        var result = MTConnectStreamsParser.Parse(
            Doc(1, 2, """<Execution dataItemId="e" timestamp="2026-11-10T14:00:00.5+02:00">ACTIVE</Execution>"""));

        var at = result.Observations.ShouldHaveSingleItem().TimestampUtc;
        at.ShouldBe(new DateTime(2026, 11, 10, 12, 0, 0, 500, DateTimeKind.Utc));
        at.Kind.ShouldBe(DateTimeKind.Utc);
    }

    /// <summary>
    ///     Java <c>anAbsurdlyDeepErrorDocumentStillYieldsTheAgentsWords</c>: the new nesting bound applies to the
    ///     observation walk only, so a deeply nested error document still reports the Agent's own text.
    /// </summary>
    [Fact]
    public void An_absurdly_deep_error_document_still_yields_the_agents_words()
    {
        var nest = string.Concat(Enumerable.Repeat("<x>", 100));
        var unnest = string.Concat(Enumerable.Repeat("</x>", 100));
        var xml = $"""<MTConnectError><Errors>{nest}<Error errorCode="OUT_OF_RANGE">deep</Error>{unnest}</Errors></MTConnectError>""";

        var ex = Should.Throw<InvalidDataException>(() => MTConnectStreamsParser.Parse(xml));

        ex.Message.ShouldContain("OUT_OF_RANGE: deep");
    }

    /// <summary>A read-only stream that serves <c>head</c> then an endless run of document bytes with no boundary.</summary>
    private sealed class EndlessPart(byte[] head) : Stream
    {
        private long _position;

        public override int Read(byte[] buffer, int offset, int count)
        {
            var written = 0;
            while (written < count)
            {
                buffer[offset + written] = _position < head.Length ? head[_position] : (byte)'a';
                _position++;
                written++;
            }

            return written;
        }

        public override bool CanRead => true;
        public override bool CanSeek => false;
        public override bool CanWrite => false;
        public override long Length => throw new NotSupportedException();
        public override long Position { get => _position; set => throw new NotSupportedException(); }
        public override void Flush() { }
        public override long Seek(long offset, SeekOrigin origin) => throw new NotSupportedException();
        public override void SetLength(long value) => throw new NotSupportedException();
        public override void Write(byte[] buffer, int offset, int count) => throw new NotSupportedException();
    }
}