using SuiteLink.Client.Internal;
using SuiteLink.Client.Protocol;

namespace SuiteLink.Client.Tests.Internal;

public sealed class SuiteLinkSessionTests
{
    [Fact]
    public void NewSession_StartsDisconnected()
    {
        var session = new SuiteLinkSession();

        Assert.Equal(SuiteLinkSessionState.Disconnected, session.State);
    }

    [Fact]
    public void RegisterSubscription_TracksForwardAndReverseMappings()
    {
        var session = new SuiteLinkSession();

        session.RegisterSubscription("Pump001.Run", 0x1234, _ => { });

        Assert.True(session.TryGetTagId("Pump001.Run", out var tagId));
        Assert.Equal(0x1234u, tagId);
        Assert.True(session.TryGetItemName(0x1234, out var itemName));
        Assert.Equal("Pump001.Run", itemName);
    }

    [Fact]
    public void TryDispatchUpdate_KnownTag_InvokesRegisteredCallback()
    {
        var session = new SuiteLinkSession();
        SuiteLinkTagUpdate? callbackUpdate = null;

        session.RegisterSubscription("Pump001.Run", 0x1234, update => callbackUpdate = update);

        var decoded = new DecodedUpdate(
            TagId: 0x1234,
            Quality: 0x00C0,
            ElapsedMilliseconds: 10,
            Value: SuiteLinkValue.FromBoolean(true));

        var receivedAtUtc = new DateTimeOffset(2026, 03, 16, 18, 00, 00, TimeSpan.Zero);
        var dispatched = session.TryDispatchUpdate(decoded, receivedAtUtc, out var dispatchedUpdate);

        Assert.True(dispatched);
        Assert.NotNull(dispatchedUpdate);
        Assert.Equal("Pump001.Run", dispatchedUpdate.ItemName);
        Assert.Equal(0x1234u, dispatchedUpdate.TagId);
        Assert.Equal(0x00C0, dispatchedUpdate.Quality);
        Assert.Equal(10, dispatchedUpdate.ElapsedMilliseconds);
        Assert.Equal(receivedAtUtc, dispatchedUpdate.ReceivedAtUtc);
        Assert.Equal(dispatchedUpdate, callbackUpdate);
    }

    [Fact]
    public void TryDispatchUpdate_UnknownTag_ReturnsFalseAndDoesNotInvokeCallback()
    {
        var session = new SuiteLinkSession();
        var callbackCount = 0;

        session.RegisterSubscription("Pump001.Run", 0x1234, _ => callbackCount++);

        var decoded = new DecodedUpdate(
            TagId: 0x9999,
            Quality: 0x00C0,
            ElapsedMilliseconds: 5,
            Value: SuiteLinkValue.FromInt32(42));

        var dispatched = session.TryDispatchUpdate(decoded, DateTimeOffset.UtcNow, out var dispatchedUpdate);

        Assert.False(dispatched);
        Assert.Null(dispatchedUpdate);
        Assert.Equal(0, callbackCount);
    }

    [Fact]
    public void UnregisterByItemName_RemovesMappingsAndCallback()
    {
        var session = new SuiteLinkSession();
        var callbackCount = 0;

        session.RegisterSubscription("Pump001.Run", 0x1234, _ => callbackCount++);

        Assert.True(session.TryUnregisterByItemName("Pump001.Run", out var removedTagId));
        Assert.Equal(0x1234u, removedTagId);
        Assert.False(session.TryGetTagId("Pump001.Run", out _));
        Assert.False(session.TryGetItemName(0x1234, out _));

        var decoded = new DecodedUpdate(
            TagId: 0x1234,
            Quality: 0x00C0,
            ElapsedMilliseconds: 1,
            Value: SuiteLinkValue.FromBoolean(true));

        var dispatched = session.TryDispatchUpdate(decoded, DateTimeOffset.UtcNow, out _);

        Assert.False(dispatched);
        Assert.Equal(0, callbackCount);
    }

    [Fact]
    public void RegisterSubscription_SameItemName_ReplacesOldTagAndCallback()
    {
        var session = new SuiteLinkSession();
        var oldCount = 0;
        var newCount = 0;

        session.RegisterSubscription("Pump001.Run", 0x1000, _ => oldCount++);
        session.RegisterSubscription("Pump001.Run", 0x2000, _ => newCount++);

        Assert.False(session.TryGetItemName(0x1000, out _));
        Assert.True(session.TryGetTagId("Pump001.Run", out var currentTagId));
        Assert.Equal(0x2000u, currentTagId);

        var oldDecoded = new DecodedUpdate(0x1000, 0x00C0, 1, SuiteLinkValue.FromBoolean(true));
        var newDecoded = new DecodedUpdate(0x2000, 0x00C0, 1, SuiteLinkValue.FromBoolean(true));

        Assert.False(session.TryDispatchUpdate(oldDecoded, DateTimeOffset.UtcNow, out _));
        Assert.True(session.TryDispatchUpdate(newDecoded, DateTimeOffset.UtcNow, out _));
        Assert.Equal(0, oldCount);
        Assert.Equal(1, newCount);
    }

    [Fact]
    public void RegisterSubscription_SameTagId_ReplacesOldItemAndCallback()
    {
        var session = new SuiteLinkSession();
        var oldCount = 0;
        var newCount = 0;

        session.RegisterSubscription("Pump001.Run", 0x1234, _ => oldCount++);
        session.RegisterSubscription("Pump002.Run", 0x1234, _ => newCount++);

        Assert.False(session.TryGetTagId("Pump001.Run", out _));
        Assert.True(session.TryGetTagId("Pump002.Run", out var replacementTagId));
        Assert.Equal(0x1234u, replacementTagId);

        var decoded = new DecodedUpdate(0x1234, 0x00C0, 1, SuiteLinkValue.FromBoolean(true));
        Assert.True(session.TryDispatchUpdate(decoded, DateTimeOffset.UtcNow, out var dispatchedUpdate));
        Assert.NotNull(dispatchedUpdate);
        Assert.Equal("Pump002.Run", dispatchedUpdate.ItemName);
        Assert.Equal(0, oldCount);
        Assert.Equal(1, newCount);
    }

    [Fact]
    public void TryDispatchUpdate_CallbackThrows_IsCaughtAndReported()
    {
        var session = new SuiteLinkSession();

        session.RegisterSubscription("Pump001.Run", 0x1234, _ => throw new InvalidOperationException("callback failure"));

        var decoded = new DecodedUpdate(
            TagId: 0x1234,
            Quality: 0x00C0,
            ElapsedMilliseconds: 5,
            Value: SuiteLinkValue.FromInt32(42));

        var dispatched = session.TryDispatchUpdate(
            decoded,
            DateTimeOffset.UtcNow,
            out var dispatchedUpdate,
            out var callbackException);

        Assert.False(dispatched);
        Assert.NotNull(dispatchedUpdate);
        Assert.NotNull(callbackException);
        Assert.Equal("callback failure", callbackException.Message);
    }

    [Fact]
    public void SetState_InvalidTransition_ThrowsInvalidOperationException()
    {
        var session = new SuiteLinkSession();

        var ex = Assert.Throws<InvalidOperationException>(() => session.SetState(SuiteLinkSessionState.SessionConnected));

        Assert.Contains("Invalid state transition", ex.Message);
        Assert.Equal(SuiteLinkSessionState.Disconnected, session.State);
    }

    [Fact]
    public void TryTransitionState_EnforcesExpectedCurrentStateAtomically()
    {
        var session = new SuiteLinkSession();

        Assert.True(session.TryTransitionState(SuiteLinkSessionState.Disconnected, SuiteLinkSessionState.TcpConnected));
        Assert.Equal(SuiteLinkSessionState.TcpConnected, session.State);

        Assert.False(session.TryTransitionState(SuiteLinkSessionState.Disconnected, SuiteLinkSessionState.HandshakeComplete));
        Assert.Equal(SuiteLinkSessionState.TcpConnected, session.State);
    }
}