package cluster

import (
	"context"
	"testing"

	"webui4frpc/internal/store"
)

// staleTokenWith copies the engine's current state but rewrites the given
// forward's disabled flag, standing in for a token a neighbour captured before
// this node's decision.
func staleTokenWith(eng *Engine, local, remote string, port int, disabled bool) State {
	s := eng.state
	out := State{
		LeaderID: s.LeaderID,
		Nodes:    s.Nodes,
		Cycle:    s.Cycle,
		Topology: map[string]*TopoEntry{},
	}
	for id, e := range s.Topology {
		cp := *e
		if cp.Local.Name == local && cp.Remote.Name == remote && cp.Link.RemotePort == port {
			cp.Link.Disabled = disabled
			cp.Active = !disabled
		}
		out.Topology[id] = &cp
	}
	return out
}

// TestLocalDisableSurvivesAdoption is the regression test for the wipe that made
// the ring's authority unachievable.
//
// OnToken/AdoptState replace e.state wholesale. A stop decided between two token
// cycles was therefore erased by the next adoption whenever the incoming token
// had been captured before the decision — so the flag never reached the other
// members and the forward kept running. Written as a probe BEFORE the fix: it
// reported "after adopting a stale token: known=true disabled=false".
func TestLocalDisableSurvivesAdoption(t *testing.T) {
	eng := newTestEngine("n1", true)
	eng.state.AddPending(store.Local{Name: "web"}, store.Remote{Name: "frps1"}, store.Link{RemotePort: 18081})
	if _, err := eng.OnToken(context.Background(), &Token{Cycle: 1, State: eng.state, SentAt: 1}); err != nil {
		t.Fatal(err)
	}

	// Local decision: stop it.
	eng.UpdateTopologyDisabled("web", "frps1", 18081, true)
	if d, _ := eng.TopologyDisabled("web", "frps1", 18081); !d {
		t.Fatal("precondition: the local stop should be visible")
	}

	// A token captured BEFORE the decision arrives.
	stale := staleTokenWith(eng, "web", "frps1", 18081, false)
	if _, err := eng.OnToken(context.Background(), &Token{Cycle: 2, State: stale, SentAt: 2}); err != nil {
		t.Fatal(err)
	}
	// Assert on the STATE, not the TopologyDisabled() accessor: the accessor
	// short-circuits to the pending local decision, so it would report the stop
	// even when the state about to be forwarded still says "enabled". What
	// matters is that the token this node sends on carries the decision.
	assertForwardedDisabled(t, eng, "web", "frps1", 18081, true)
}

// assertForwardedDisabled checks the disabled value a DOWNSTREAM node would see
// in the token this engine forwards — the value that actually propagates.
func assertForwardedDisabled(t *testing.T, eng *Engine, local, remote string, port int, want bool) {
	t.Helper()
	// Model one hop: a fresh engine adopts exactly what this one would send.
	peer := newTestEngine("peer", false)
	peer.AdoptState(eng.state)
	got, known := peer.TopologyDisabled(local, remote, port)
	if !known {
		t.Fatalf("peer learned no entry for %s→%s:%d", local, remote, port)
	}
	if got != want {
		t.Fatalf("the forwarded token carries disabled=%v, want %v — the decision did not "+
			"propagate, so the other members would keep the old state", got, want)
	}
}

// TestLocalReEnableSurvivesAdoption: a re-enable needs the same protection. The
// value false is easy to overlook — nothing "looks" stopped, yet losing it just
// as silently strands the forward in the stopped state.
func TestLocalReEnableSurvivesAdoption(t *testing.T) {
	eng := newTestEngine("n1", true)
	eng.state.AddPending(store.Local{Name: "web"}, store.Remote{Name: "frps1"}, store.Link{RemotePort: 18081})
	if _, err := eng.OnToken(context.Background(), &Token{Cycle: 1, State: eng.state, SentAt: 1}); err != nil {
		t.Fatal(err)
	}
	eng.UpdateTopologyDisabled("web", "frps1", 18081, true)
	eng.UpdateTopologyDisabled("web", "frps1", 18081, false)

	// A token that still says disabled (captured mid-stop) arrives.
	mid := staleTokenWith(eng, "web", "frps1", 18081, true)
	if _, err := eng.OnToken(context.Background(), &Token{Cycle: 2, State: mid, SentAt: 2}); err != nil {
		t.Fatal(err)
	}
	assertForwardedDisabled(t, eng, "web", "frps1", 18081, false)
}

// TestConfirmedDecisionStopsBeingAsserted: once the ring reports the same value
// the decision is confirmed everywhere, so this node must stop overriding —
// otherwise it would fight a later decision made elsewhere.
func TestConfirmedDecisionStopsBeingAsserted(t *testing.T) {
	eng := newTestEngine("n1", true)
	eng.state.AddPending(store.Local{Name: "web"}, store.Remote{Name: "frps1"}, store.Link{RemotePort: 18081})
	if _, err := eng.OnToken(context.Background(), &Token{Cycle: 1, State: eng.state, SentAt: 1}); err != nil {
		t.Fatal(err)
	}

	eng.UpdateTopologyDisabled("web", "frps1", 18081, true)
	if len(eng.localDisabled) != 1 {
		t.Fatalf("a pending decision should be tracked, got %v", eng.localDisabled)
	}
	// The ring comes back agreeing.
	agreed := staleTokenWith(eng, "web", "frps1", 18081, true)
	if _, err := eng.OnToken(context.Background(), &Token{Cycle: 2, State: agreed, SentAt: 2}); err != nil {
		t.Fatal(err)
	}
	if len(eng.localDisabled) != 0 {
		t.Fatalf("a confirmed decision must stop being asserted, still tracking %v", eng.localDisabled)
	}

	// A peer now decides the opposite; this node must follow the ring.
	peerSaysEnabled := staleTokenWith(eng, "web", "frps1", 18081, false)
	if _, err := eng.OnToken(context.Background(), &Token{Cycle: 3, State: peerSaysEnabled, SentAt: 3}); err != nil {
		t.Fatal(err)
	}
	if d, _ := eng.TopologyDisabled("web", "frps1", 18081); d {
		t.Fatal("this node kept overriding a peer's later decision; the ring is not authoritative")
	}
}

// TestLocalDecisionsDoNotAccumulate: the tracking map is swept against the live
// topology, so a long-lived cluster cannot grow it without bound.
func TestLocalDecisionsDoNotAccumulate(t *testing.T) {
	eng := newTestEngine("n1", true)
	eng.state.AddPending(store.Local{Name: "web"}, store.Remote{Name: "frps1"}, store.Link{RemotePort: 18081})
	if _, err := eng.OnToken(context.Background(), &Token{Cycle: 1, State: eng.state, SentAt: 1}); err != nil {
		t.Fatal(err)
	}

	// Decisions for forwards this node has never seen.
	eng.UpdateTopologyDisabled("ghost1", "frps1", 1, true)
	eng.UpdateTopologyDisabled("ghost2", "frps1", 2, true)
	if len(eng.localDisabled) != 2 {
		t.Fatalf("expected 2 tracked decisions, got %d", len(eng.localDisabled))
	}
	// A cycle runs: neither ghost is in the topology, so both are swept.
	if _, err := eng.OnToken(context.Background(), &Token{Cycle: 2, State: eng.state, SentAt: 2}); err != nil {
		t.Fatal(err)
	}
	if len(eng.localDisabled) != 0 {
		t.Fatalf("decisions for forwards outside the topology must be swept, got %v", eng.localDisabled)
	}
}