package deployer

import (
	"context"
	"encoding/json"
	"errors"
	"strings"
	"sync"
	"sync/atomic"
	"testing"
	"time"

	"github.com/alexei/tinyforge/internal/store"
	"github.com/alexei/tinyforge/internal/workload/plugin"
)

// fakeSource is a stub Source implementation registered exactly once
// (kind="dispatchertest") so each dispatch test can assert exactly which
// lifecycle method ran. Counters and the configured error are atomic /
// mutex-guarded because a future parallel run should not flake.
type fakeSource struct {
	kind string

	mu           sync.Mutex
	deployErr    error
	teardownErr  error
	reconcileErr error

	deployCount    atomic.Int32
	teardownCount  atomic.Int32
	reconcileCount atomic.Int32

	lastIntent plugin.DeploymentIntent
	lastDeps   plugin.Deps
}

func (f *fakeSource) Kind() string                   { return f.kind }
func (f *fakeSource) SchemaSample() any              { return struct{}{} }
func (f *fakeSource) Validate(json.RawMessage) error { return nil }

func (f *fakeSource) Deploy(_ context.Context, deps plugin.Deps, _ plugin.Workload, intent plugin.DeploymentIntent) error {
	f.deployCount.Add(1)
	f.mu.Lock()
	f.lastIntent = intent
	f.lastDeps = deps
	err := f.deployErr
	f.mu.Unlock()
	return err
}

func (f *fakeSource) Teardown(_ context.Context, deps plugin.Deps, _ plugin.Workload) error {
	f.teardownCount.Add(1)
	f.mu.Lock()
	f.lastDeps = deps
	err := f.teardownErr
	f.mu.Unlock()
	return err
}

func (f *fakeSource) Reconcile(_ context.Context, deps plugin.Deps, _ plugin.Workload) error {
	f.reconcileCount.Add(1)
	f.mu.Lock()
	f.lastDeps = deps
	err := f.reconcileErr
	f.mu.Unlock()
	return err
}

func (f *fakeSource) setDeployErr(err error)    { f.mu.Lock(); f.deployErr = err; f.mu.Unlock() }
func (f *fakeSource) setTeardownErr(err error)  { f.mu.Lock(); f.teardownErr = err; f.mu.Unlock() }
func (f *fakeSource) setReconcileErr(err error) { f.mu.Lock(); f.reconcileErr = err; f.mu.Unlock() }

// dispatchTestSource is the singleton fake registered into the plugin
// registry. Registration happens exactly once — subsequent calls would
// panic (RegisterSource panics on duplicate kind).
var dispatchTestSource = &fakeSource{kind: "dispatchertest"}

func init() {
	plugin.RegisterSource(dispatchTestSource)
}

// resetFake clears counters + queued errors between tests. The Source
// instance is shared (the registry can't be cleared per-test) so reset
// is the seam.
func resetFake(t *testing.T) {
	t.Helper()
	dispatchTestSource.mu.Lock()
	dispatchTestSource.deployErr = nil
	dispatchTestSource.teardownErr = nil
	dispatchTestSource.reconcileErr = nil
	dispatchTestSource.lastIntent = plugin.DeploymentIntent{}
	dispatchTestSource.lastDeps = plugin.Deps{}
	dispatchTestSource.mu.Unlock()
	dispatchTestSource.deployCount.Store(0)
	dispatchTestSource.teardownCount.Store(0)
	dispatchTestSource.reconcileCount.Store(0)
}

func newTestDeployer(t *testing.T) *Deployer {
	t.Helper()
	st, err := store.New(":memory:")
	if err != nil {
		t.Fatalf("create store: %v", err)
	}
	t.Cleanup(func() { st.Close() })
	// All other deps are nil — the fake source ignores them. The dispatch
	// surface itself does not dereference them.
	return New(nil, nil, st, nil, nil, nil, [32]byte{})
}

func sampleWorkload() plugin.Workload {
	return plugin.Workload{
		ID:           "wid-dispatch",
		Name:         "wkl",
		SourceKind:   "dispatchertest",
		SourceConfig: json.RawMessage(`{}`),
	}
}

// ---- DispatchPlugin ---------------------------------------------------------

func TestDispatchPlugin_HappyPath_CallsDeployOnce(t *testing.T) {
	resetFake(t)
	d := newTestDeployer(t)

	intent := plugin.DeploymentIntent{Reason: "manual", TriggeredBy: "alice"}
	if err := d.DispatchPlugin(context.Background(), sampleWorkload(), intent); err != nil {
		t.Fatalf("DispatchPlugin: %v", err)
	}
	if got := dispatchTestSource.deployCount.Load(); got != 1 {
		t.Fatalf("Deploy called %d times, want 1", got)
	}
	if dispatchTestSource.lastIntent.Reason != "manual" {
		t.Fatalf("intent.Reason = %q, want manual", dispatchTestSource.lastIntent.Reason)
	}
	if dispatchTestSource.lastIntent.TriggeredBy != "alice" {
		t.Fatalf("intent.TriggeredBy = %q, want alice", dispatchTestSource.lastIntent.TriggeredBy)
	}
}

func TestDispatchPlugin_UnknownKind_ReturnsRegistryError(t *testing.T) {
	resetFake(t)
	d := newTestDeployer(t)

	w := sampleWorkload()
	w.SourceKind = "no-such-kind"
	err := d.DispatchPlugin(context.Background(), w, plugin.DeploymentIntent{})
	if err == nil {
		t.Fatalf("expected error for unknown kind, got nil")
	}
	if !strings.Contains(err.Error(), "no source registered") {
		t.Fatalf("error = %q, want substring 'no source registered'", err.Error())
	}
	if got := dispatchTestSource.deployCount.Load(); got != 0 {
		t.Fatalf("Deploy must not be called for unknown kind, got %d", got)
	}
}

func TestDispatchPlugin_PropagatesSourceError(t *testing.T) {
	resetFake(t)
	d := newTestDeployer(t)

	want := errors.New("boom")
	dispatchTestSource.setDeployErr(want)

	err := d.DispatchPlugin(context.Background(), sampleWorkload(), plugin.DeploymentIntent{})
	if !errors.Is(err, want) {
		t.Fatalf("expected wrapped error to match %v, got %v", want, err)
	}
}

// ---- DispatchTeardown -------------------------------------------------------

func TestDispatchTeardown_HappyPath_CallsTeardownOnce(t *testing.T) {
	resetFake(t)
	d := newTestDeployer(t)

	if err := d.DispatchTeardown(context.Background(), sampleWorkload()); err != nil {
		t.Fatalf("DispatchTeardown: %v", err)
	}
	if got := dispatchTestSource.teardownCount.Load(); got != 1 {
		t.Fatalf("Teardown called %d times, want 1", got)
	}
	if got := dispatchTestSource.deployCount.Load(); got != 0 {
		t.Fatalf("Teardown must not call Deploy, got %d Deploy calls", got)
	}
}

func TestDispatchTeardown_UnknownKind_ReturnsRegistryError(t *testing.T) {
	resetFake(t)
	d := newTestDeployer(t)

	w := sampleWorkload()
	w.SourceKind = "no-such-kind"
	err := d.DispatchTeardown(context.Background(), w)
	if err == nil || !strings.Contains(err.Error(), "no source registered") {
		t.Fatalf("expected unknown-kind error, got %v", err)
	}
}

func TestDispatchTeardown_PropagatesSourceError(t *testing.T) {
	resetFake(t)
	d := newTestDeployer(t)

	want := errors.New("teardown failed")
	dispatchTestSource.setTeardownErr(want)

	err := d.DispatchTeardown(context.Background(), sampleWorkload())
	if !errors.Is(err, want) {
		t.Fatalf("expected wrapped error to match %v, got %v", want, err)
	}
}

// ---- DispatchReconcile ------------------------------------------------------

func TestDispatchReconcile_HappyPath_CallsReconcileOnce(t *testing.T) {
	resetFake(t)
	d := newTestDeployer(t)

	if err := d.DispatchReconcile(context.Background(), sampleWorkload()); err != nil {
		t.Fatalf("DispatchReconcile: %v", err)
	}
	if got := dispatchTestSource.reconcileCount.Load(); got != 1 {
		t.Fatalf("Reconcile called %d times, want 1", got)
	}
}

func TestDispatchReconcile_UnknownKind_ReturnsRegistryError(t *testing.T) {
	resetFake(t)
	d := newTestDeployer(t)

	w := sampleWorkload()
	w.SourceKind = "no-such-kind"
	err := d.DispatchReconcile(context.Background(), w)
	if err == nil || !strings.Contains(err.Error(), "no source registered") {
		t.Fatalf("expected unknown-kind error, got %v", err)
	}
}

func TestDispatchReconcile_PropagatesSourceError(t *testing.T) {
	resetFake(t)
	d := newTestDeployer(t)

	want := errors.New("reconcile failed")
	dispatchTestSource.setReconcileErr(want)

	err := d.DispatchReconcile(context.Background(), sampleWorkload())
	if !errors.Is(err, want) {
		t.Fatalf("expected wrapped error to match %v, got %v", want, err)
	}
}

// ---- PluginDeps -------------------------------------------------------------

func TestPluginDeps_PassesStoreAndEncKey(t *testing.T) {
	resetFake(t)
	d := newTestDeployer(t)

	if err := d.DispatchPlugin(context.Background(), sampleWorkload(), plugin.DeploymentIntent{}); err != nil {
		t.Fatalf("dispatch: %v", err)
	}
	got := dispatchTestSource.lastDeps
	if got.Store != d.store {
		t.Fatalf("Deps.Store mismatch: got %p want %p", got.Store, d.store)
	}
	// EncKey is a value type — compare bytes.
	if got.EncKey != d.encKey {
		t.Fatalf("Deps.EncKey not propagated")
	}
}

func TestPluginDeps_DNSReadUnderRWMutex_NoDeadlockOnHotSwap(t *testing.T) {
	// PluginDeps takes dnsMu.RLock; SetDNSProvider takes dnsMu.Lock. A bug
	// where the read code path also took the write lock would deadlock
	// when a concurrent SetDNSProvider runs. Run both in parallel goroutines
	// and assert both finish.
	d := newTestDeployer(t)

	const N = 50
	var wg sync.WaitGroup
	wg.Add(2 * N)
	for i := 0; i < N; i++ {
		go func() { defer wg.Done(); _ = d.PluginDeps() }()
		go func() { defer wg.Done(); d.SetDNSProvider(nil) }()
	}
	done := make(chan struct{})
	go func() { wg.Wait(); close(done) }()

	// Real timeout: a deadlock here would hang `go test` for the entire
	// package timeout (default 10 min) and report no useful diagnostic.
	// Bound at 2s so a regression fails this test specifically.
	select {
	case <-done:
	case <-time.After(2 * time.Second):
		t.Fatal("deadlock: PluginDeps/SetDNSProvider did not finish within 2s")
	}
}