using AcDream.Core.World;
using Xunit;

namespace AcDream.Core.Tests.World;

public sealed class TeleportAnimSequencerTests
{
    // --- Task 1.1: type presence ---

    [Fact]
    public void Enums_HaveExpectedValues()
    {
        Assert.Equal(0, (int)TeleportAnimState.Off);
        Assert.Equal(1, (int)TeleportAnimState.WorldFadeOut);
        Assert.Equal(2, (int)TeleportAnimState.TunnelFadeIn);
        Assert.Equal(3, (int)TeleportAnimState.Tunnel);
        Assert.Equal(4, (int)TeleportAnimState.TunnelContinue);
        Assert.Equal(5, (int)TeleportAnimState.TunnelFadeOut);
        Assert.Equal(6, (int)TeleportAnimState.WorldFadeIn);

        _ = TeleportEntryKind.Portal;
        _ = TeleportEntryKind.Login;
        _ = TeleportEntryKind.Death;
        _ = TeleportEntryKind.Logout;

        _ = TeleportAnimEvent.PlayEnterSound;
        _ = TeleportAnimEvent.PlayExitSound;
        _ = TeleportAnimEvent.Place;
        _ = TeleportAnimEvent.FireLoginComplete;
        _ = TeleportAnimEvent.EnterTunnel;
    }

    [Fact]
    public void Snapshot_DefaultsAreOff_ClearAlpha()
    {
        var snap = new TeleportAnimSnapshot(
            TeleportAnimState.Off, FadeAlpha: 0f, ShowTunnel: false, ShowPleaseWait: false);
        Assert.Equal(TeleportAnimState.Off, snap.State);
        Assert.Equal(0f, snap.FadeAlpha);
        Assert.False(snap.ShowTunnel);
        Assert.False(snap.ShowPleaseWait);
    }

    // --- Task 1.2: Begin(), IsActive, initial state ---

    [Theory]
    [InlineData(TeleportEntryKind.Portal,  TeleportAnimState.Tunnel)]
    [InlineData(TeleportEntryKind.Login,   TeleportAnimState.Tunnel)]
    [InlineData(TeleportEntryKind.Death,   TeleportAnimState.Tunnel)]
    [InlineData(TeleportEntryKind.Logout,  TeleportAnimState.WorldFadeOut)]
    public void Begin_SetsCorrectStartState(TeleportEntryKind kind, TeleportAnimState expectedStart)
    {
        var seq = new TeleportAnimSequencer();
        Assert.False(seq.IsActive);

        seq.Begin(kind);

        Assert.True(seq.IsActive);
        Assert.Equal(expectedStart, seq.State);
    }

    [Fact]
    public void Begin_EmitsPlayEnterSoundOnFirstTick()
    {
        // PlayEnterSound is edge-triggered on the first Tick after Begin.
        var seq = new TeleportAnimSequencer();
        seq.Begin(TeleportEntryKind.Portal);
        var (_, events) = seq.Tick(dt: 0f, worldReady: false);
        Assert.Contains(TeleportAnimEvent.PlayEnterSound, events);
    }

    // --- Task 1.3: State transitions — timing-correct Tick() ---

    // Helper: drive the sequencer forward by total elapsed time using small fixed steps.
    private static (TeleportAnimSnapshot snap, List<TeleportAnimEvent> allEvents)
        DriveSeconds(TeleportAnimSequencer seq, float seconds, bool worldReady, float step = 0.016f)
    {
        var allEvts = new List<TeleportAnimEvent>();
        float remaining = seconds;
        TeleportAnimSnapshot last = default;
        while (remaining > 0f)
        {
            float dt = Math.Min(step, remaining);
            var (snap, evts) = seq.Tick(dt, worldReady);
            last = snap;
            allEvts.AddRange(evts);
            remaining -= dt;
        }
        return (last, allEvts);
    }

    // --- Logout path: WorldFadeOut -> TunnelFadeIn -> Tunnel ---

    [Fact]
    public void Logout_AfterFadeTime_TransitionsToTunnelFadeIn()
    {
        var seq = new TeleportAnimSequencer();
        seq.Begin(TeleportEntryKind.Logout);

        // Consume the enter-sound tick at dt=0
        seq.Tick(0f, worldReady: false);

        // Drive just past FadeTime (1.0s)
        DriveSeconds(seq, TeleportAnimSequencer.FadeTime + 0.02f, worldReady: false);

        Assert.Equal(TeleportAnimState.TunnelFadeIn, seq.State);
    }

    [Fact]
    public void Logout_After2xFadeTime_TransitionsToTunnel()
    {
        var seq = new TeleportAnimSequencer();
        seq.Begin(TeleportEntryKind.Logout);
        seq.Tick(0f, worldReady: false); // consume enter-sound

        DriveSeconds(seq, 2f * TeleportAnimSequencer.FadeTime + 0.02f, worldReady: false);

        Assert.Equal(TeleportAnimState.Tunnel, seq.State);
    }

    // --- Portal/Login/Death path: enters at Tunnel ---

    [Fact]
    public void Portal_StartsInTunnel_HoldsWhileNotReady()
    {
        var seq = new TeleportAnimSequencer();
        seq.Begin(TeleportEntryKind.Portal);
        seq.Tick(0f, worldReady: false); // consume enter-sound

        // Drive 10s — should not advance past Tunnel while !worldReady
        DriveSeconds(seq, 10f, worldReady: false);

        Assert.Equal(TeleportAnimState.Tunnel, seq.State);
    }

    [Fact]
    public void Portal_WhenWorldReady_TransitionsToTunnelContinue_EmitsEnterTunnelAndPlace()
    {
        var seq = new TeleportAnimSequencer();
        seq.Begin(TeleportEntryKind.Portal);
        seq.Tick(0f, worldReady: false); // consume enter-sound

        // The very first tick with worldReady=true should advance Tunnel→TunnelContinue and emit Place.
        var (_, evts) = seq.Tick(0.016f, worldReady: true);

        Assert.Equal(TeleportAnimState.TunnelContinue, seq.State);
        Assert.Contains(TeleportAnimEvent.Place, evts);
    }

    // --- TunnelContinue: MIN_CONTINUE hold then TunnelFadeOut ---

    [Fact]
    public void TunnelContinue_DoesNotAdvance_BeforeMinContinue()
    {
        var seq = new TeleportAnimSequencer();
        seq.Begin(TeleportEntryKind.Portal);
        seq.Tick(0f, worldReady: false);
        // Enter TunnelContinue
        seq.Tick(0.016f, worldReady: true);
        Assert.Equal(TeleportAnimState.TunnelContinue, seq.State);

        // Drive MinContinue - ε — should still be TunnelContinue
        DriveSeconds(seq, TeleportAnimSequencer.MinContinue - 0.1f, worldReady: true);

        Assert.Equal(TeleportAnimState.TunnelContinue, seq.State);
    }

    [Fact]
    public void TunnelContinue_AdvancesToTunnelFadeOut_AfterMinContinue()
    {
        var seq = new TeleportAnimSequencer();
        seq.Begin(TeleportEntryKind.Portal);
        seq.Tick(0f, worldReady: false);
        seq.Tick(0.016f, worldReady: true); // -> TunnelContinue

        DriveSeconds(seq, TeleportAnimSequencer.MinContinue + 0.05f, worldReady: true);

        Assert.Equal(TeleportAnimState.TunnelFadeOut, seq.State);
    }

    // --- MAX_CONTINUE forces progress even when !worldReady ---

    [Fact]
    public void TunnelContinue_ForcesAdvance_AtMaxContinue_EvenIfNotReady()
    {
        // Simulate: world never becomes fully ready but MAX_CONTINUE forces fade-out
        // This path exercises the safety-net from spec §3.4.
        var seq = new TeleportAnimSequencer();
        seq.Begin(TeleportEntryKind.Portal);
        seq.Tick(0f, worldReady: false);
        // Manually push the state to TunnelContinue by passing worldReady=true for one tick,
        // then simulate worldReady toggling back to false.
        seq.Tick(0.016f, worldReady: true); // -> TunnelContinue

        // Drive MaxContinue + ε with worldReady=false (simulating "world never loaded")
        DriveSeconds(seq, TeleportAnimSequencer.MaxContinue + 0.05f, worldReady: false);

        Assert.Equal(TeleportAnimState.TunnelFadeOut, seq.State);
    }

    // --- TunnelFadeOut -> WorldFadeIn: PlayExitSound edge event ---

    [Fact]
    public void TunnelFadeOut_EmitsPlayExitSound_OnTransitionToWorldFadeIn()
    {
        var seq = new TeleportAnimSequencer();
        seq.Begin(TeleportEntryKind.Portal);
        seq.Tick(0f, worldReady: false);
        seq.Tick(0.016f, worldReady: true); // -> TunnelContinue

        // Drive through MinContinue -> TunnelFadeOut
        DriveSeconds(seq, TeleportAnimSequencer.MinContinue + 0.05f, worldReady: true);
        Assert.Equal(TeleportAnimState.TunnelFadeOut, seq.State);

        // Drive through FadeTime -> WorldFadeIn; PlayExitSound should fire on that edge
        var (_, evts) = DriveSeconds(seq, TeleportAnimSequencer.FadeTime + 0.05f, worldReady: true);
        Assert.Equal(TeleportAnimState.WorldFadeIn, seq.State);
        Assert.Contains(TeleportAnimEvent.PlayExitSound, evts);
    }

    // --- WorldFadeIn -> Off: FireLoginComplete edge event ---

    [Fact]
    public void WorldFadeIn_EmitsFireLoginComplete_OnTransitionToOff()
    {
        var seq = new TeleportAnimSequencer();
        seq.Begin(TeleportEntryKind.Portal);
        seq.Tick(0f, worldReady: false);
        seq.Tick(0.016f, worldReady: true); // -> TunnelContinue
        DriveSeconds(seq, TeleportAnimSequencer.MinContinue + 0.05f, worldReady: true);
        DriveSeconds(seq, TeleportAnimSequencer.FadeTime + 0.05f, worldReady: true); // -> WorldFadeIn

        var (_, evts) = DriveSeconds(seq, TeleportAnimSequencer.FadeTime + 0.05f, worldReady: true);

        Assert.Equal(TeleportAnimState.Off, seq.State);
        Assert.False(seq.IsActive);
        Assert.Contains(TeleportAnimEvent.FireLoginComplete, evts);
    }

    // --- Task 1.4: FadeAlpha endpoints and monotonicity ---

    [Fact]
    public void FadeAlpha_IsZeroAtStart_OfWorldFadeOut()
    {
        var seq = new TeleportAnimSequencer();
        seq.Begin(TeleportEntryKind.Logout);
        var (snap, _) = seq.Tick(dt: 0f, worldReady: false);
        // At elapsed=0 in WorldFadeOut: smoothstep(0)=0 => alpha=0 (world fully visible).
        Assert.Equal(0f, snap.FadeAlpha, precision: 4);
    }

    [Fact]
    public void FadeAlpha_IsOneAtEnd_OfWorldFadeOut()
    {
        var seq = new TeleportAnimSequencer();
        seq.Begin(TeleportEntryKind.Logout);
        seq.Tick(0f, worldReady: false); // consume enter-sound tick, elapsed≈0

        // Drive to just BEFORE the transition (so we're still in WorldFadeOut)
        DriveSeconds(seq, TeleportAnimSequencer.FadeTime - 0.02f, worldReady: false);
        Assert.Equal(TeleportAnimState.WorldFadeOut, seq.State);

        var (snap, _) = seq.Tick(0f, worldReady: false);
        // smoothstep(clamp((1.0-0.02)/1.0,0,1)) should be close to 1
        Assert.True(snap.FadeAlpha > 0.95f, $"Expected FadeAlpha near 1, got {snap.FadeAlpha}");
    }

    [Fact]
    public void FadeAlpha_IsMonotonicallyIncreasing_DuringWorldFadeOut()
    {
        var seq = new TeleportAnimSequencer();
        seq.Begin(TeleportEntryKind.Logout);
        seq.Tick(0f, worldReady: false);

        float prev = -1f;
        // Sample 50 steps within FadeTime
        float step = TeleportAnimSequencer.FadeTime / 50f;
        for (int i = 0; i < 48; i++) // stop before transition
        {
            var (snap, _) = seq.Tick(step, worldReady: false);
            if (seq.State != TeleportAnimState.WorldFadeOut) break;
            Assert.True(snap.FadeAlpha >= prev - 0.001f,
                $"Alpha decreased: {prev} -> {snap.FadeAlpha} at step {i}");
            prev = snap.FadeAlpha;
        }
    }

    [Fact]
    public void FadeAlpha_IsZero_DuringTunnelStates()
    {
        var seq = new TeleportAnimSequencer();
        seq.Begin(TeleportEntryKind.Portal);
        seq.Tick(0f, worldReady: false);

        // In Tunnel state, overlay alpha should be 0 (the tunnel viewport is shown; no alpha quad needed)
        var (snap, _) = seq.Tick(0.016f, worldReady: false);
        Assert.Equal(TeleportAnimState.Tunnel, seq.State);
        Assert.Equal(0f, snap.FadeAlpha);
    }

    [Fact]
    public void ShowTunnel_TrueInTunnelFamilyStates_FalseOtherwise()
    {
        // Logout path: WorldFadeOut -> TunnelFadeIn -> Tunnel -> TunnelContinue -> TunnelFadeOut -> WorldFadeIn -> Off
        var seq = new TeleportAnimSequencer();
        seq.Begin(TeleportEntryKind.Logout);
        seq.Tick(0f, worldReady: false);

        // WorldFadeOut: ShowTunnel = false
        var (snap, _) = seq.Tick(0.016f, worldReady: false);
        Assert.Equal(TeleportAnimState.WorldFadeOut, seq.State);
        Assert.False(snap.ShowTunnel);

        // Advance to TunnelFadeIn
        DriveSeconds(seq, TeleportAnimSequencer.FadeTime, worldReady: false);
        Assert.Equal(TeleportAnimState.TunnelFadeIn, seq.State);
        var (snap2, _) = seq.Tick(0f, worldReady: false);
        Assert.True(snap2.ShowTunnel);

        // Advance to Tunnel
        DriveSeconds(seq, TeleportAnimSequencer.FadeTime, worldReady: false);
        Assert.Equal(TeleportAnimState.Tunnel, seq.State);
        var (snap3, _) = seq.Tick(0f, worldReady: false);
        Assert.True(snap3.ShowTunnel);
    }

    [Fact]
    public void ShowPleaseWait_TrueOnlyInTunnelContinue()
    {
        var seq = new TeleportAnimSequencer();
        seq.Begin(TeleportEntryKind.Portal);
        seq.Tick(0f, worldReady: false);

        // Tunnel: ShowPleaseWait false
        var (snap1, _) = seq.Tick(0.016f, worldReady: false);
        Assert.Equal(TeleportAnimState.Tunnel, seq.State);
        Assert.False(snap1.ShowPleaseWait);

        // Advance to TunnelContinue
        var (snap2, _) = seq.Tick(0.016f, worldReady: true);
        Assert.Equal(TeleportAnimState.TunnelContinue, seq.State);
        Assert.True(snap2.ShowPleaseWait);
    }

    // --- Task 1.5: Full portal event sequence and logout event sequence ---

    // Helper: run the sequencer to completion collecting ordered events.
    private static List<TeleportAnimEvent> RunToOff(
        TeleportEntryKind kind, bool worldReadyAfterFirstTunnel = true, float step = 0.05f)
    {
        var seq     = new TeleportAnimSequencer();
        var allEvts = new List<TeleportAnimEvent>();
        seq.Begin(kind);

        int safetyNet = 5000;
        while (seq.IsActive && --safetyNet > 0)
        {
            // Simulate world becoming ready on first Tick inside Tunnel
            bool ready = worldReadyAfterFirstTunnel && seq.State == TeleportAnimState.Tunnel;
            var (_, evts) = seq.Tick(step, worldReady: ready);
            allEvts.AddRange(evts);
        }
        return allEvts;
    }

    [Fact]
    public void Portal_FullSequence_EventsInOrder()
    {
        var evts = RunToOff(TeleportEntryKind.Portal);

        // Required events in order: PlayEnterSound, Place, PlayExitSound, FireLoginComplete.
        // EnterTunnel is optional but must come before Place if present.
        int enterIdx = evts.IndexOf(TeleportAnimEvent.PlayEnterSound);
        int placeIdx = evts.IndexOf(TeleportAnimEvent.Place);
        int exitIdx  = evts.IndexOf(TeleportAnimEvent.PlayExitSound);
        int loginIdx = evts.IndexOf(TeleportAnimEvent.FireLoginComplete);

        Assert.True(enterIdx >= 0, "PlayEnterSound must fire");
        Assert.True(placeIdx >= 0, "Place must fire");
        Assert.True(exitIdx  >= 0, "PlayExitSound must fire");
        Assert.True(loginIdx >= 0, "FireLoginComplete must fire");

        Assert.True(enterIdx < placeIdx, "PlayEnterSound must precede Place");
        Assert.True(placeIdx < exitIdx,  "Place must precede PlayExitSound");
        Assert.True(exitIdx  < loginIdx, "PlayExitSound must precede FireLoginComplete");
    }

    [Fact]
    public void Logout_FullSequence_EventsInOrder_WithEnterTunnelAfterFades()
    {
        var evts = RunToOff(TeleportEntryKind.Logout);

        int enterIdx  = evts.IndexOf(TeleportAnimEvent.PlayEnterSound);
        int tunnelIdx = evts.IndexOf(TeleportAnimEvent.EnterTunnel);
        int placeIdx  = evts.IndexOf(TeleportAnimEvent.Place);
        int exitIdx   = evts.IndexOf(TeleportAnimEvent.PlayExitSound);
        int loginIdx  = evts.IndexOf(TeleportAnimEvent.FireLoginComplete);

        Assert.True(enterIdx  >= 0, "PlayEnterSound must fire");
        Assert.True(tunnelIdx >= 0, "EnterTunnel must fire (Logout path goes through WorldFadeOut->TunnelFadeIn->Tunnel)");
        Assert.True(placeIdx  >= 0, "Place must fire");
        Assert.True(exitIdx   >= 0, "PlayExitSound must fire");
        Assert.True(loginIdx  >= 0, "FireLoginComplete must fire");

        Assert.True(enterIdx  < tunnelIdx, "PlayEnterSound must precede EnterTunnel");
        Assert.True(tunnelIdx < placeIdx,  "EnterTunnel must precede Place");
        Assert.True(placeIdx  < exitIdx,   "Place must precede PlayExitSound");
        Assert.True(exitIdx   < loginIdx,  "PlayExitSound must precede FireLoginComplete");
    }

    [Fact]
    public void Portal_NoEventsFiredTwice()
    {
        var evts = RunToOff(TeleportEntryKind.Portal);
        Assert.Equal(1, evts.Count(e => e == TeleportAnimEvent.PlayEnterSound));
        Assert.Equal(1, evts.Count(e => e == TeleportAnimEvent.Place));
        Assert.Equal(1, evts.Count(e => e == TeleportAnimEvent.PlayExitSound));
        Assert.Equal(1, evts.Count(e => e == TeleportAnimEvent.FireLoginComplete));
    }

    [Fact]
    public void Death_BehavesIdenticallyToPortal_FullSequence()
    {
        var portalEvts = RunToOff(TeleportEntryKind.Portal);
        var deathEvts  = RunToOff(TeleportEntryKind.Death);
        // Same event sequence (both enter at Tunnel)
        Assert.Equal(portalEvts, deathEvts);
    }

    [Fact]
    public void Login_BehavesIdenticallyToPortal_FullSequence()
    {
        var portalEvts = RunToOff(TeleportEntryKind.Portal);
        var loginEvts  = RunToOff(TeleportEntryKind.Login);
        Assert.Equal(portalEvts, loginEvts);
    }

    [Fact]
    public void AfterOff_IsActiveIsFalse_AndStateIsOff()
    {
        RunToOff(TeleportEntryKind.Portal);
        var seq = new TeleportAnimSequencer();
        seq.Begin(TeleportEntryKind.Portal);

        // Drain to Off
        for (int i = 0; i < 5000 && seq.IsActive; i++)
        {
            bool ready = seq.State == TeleportAnimState.Tunnel;
            seq.Tick(0.05f, worldReady: ready);
        }

        Assert.False(seq.IsActive);
        Assert.Equal(TeleportAnimState.Off, seq.State);
    }

    // --- Task 1.6: EnterTunnel fired for Portal path via Begin() ---

    [Fact]
    public void Portal_EmitsEnterTunnel_OnFirstTick()
    {
        // Portal begins directly in Tunnel; EnterTunnel signals "world is now hidden".
        var seq = new TeleportAnimSequencer();
        seq.Begin(TeleportEntryKind.Portal);

        // First tick: should emit PlayEnterSound AND EnterTunnel (both on entry)
        var (_, evts) = seq.Tick(0f, worldReady: false);
        Assert.Contains(TeleportAnimEvent.PlayEnterSound, evts);
        Assert.Contains(TeleportAnimEvent.EnterTunnel,   evts);
    }
}