package capacity

import (
	"context"
	"errors"
	"sync"
	"testing"
	"time"
)

// stubClassifier is a deterministic IntentClassifier: it records every text it
// was asked about so a test can pin whether L3 ran at all (裁决 14.4.4 的
// CAPACITY_L3_ENABLED 默认关).
type stubClassifier struct {
	mu      sync.Mutex
	seen    []string
	verdict Judgment
	err     error
	calls   int
}

func (s *stubClassifier) Classify(_ context.Context, text string) (Judgment, error) {
	s.mu.Lock()
	defer s.mu.Unlock()
	s.calls++
	s.seen = append(s.seen, text)
	if s.err != nil {
		return Judgment{}, s.err
	}
	return s.verdict, nil
}

func (s *stubClassifier) callCount() int {
	s.mu.Lock()
	defer s.mu.Unlock()
	return s.calls
}

func l3Config(c IntentClassifier, ttl time.Duration) Config {
	cfg := activeConfig()
	cfg.L3Enabled = true
	cfg.L3Classifier = c
	cfg.L3CacheTTL = ttl
	return cfg
}

// TestDecide_L3Disabled_ClassifierNeverRuns pins the default-off red line: with
// CAPACITY_L3_ENABLED false the classifier must never be consulted, even when one
// is configured, so L1/L2/L4 behavior is unchanged.
func TestDecide_L3Disabled_ClassifierNeverRuns(t *testing.T) {
	stub := &stubClassifier{verdict: Judgment{IsTask: true, Confidence: 0.9}}
	cfg := activeConfig()
	cfg.L3Classifier = stub // configured but not enabled
	cfg.L3CacheTTL = time.Minute

	// A turn no heuristic can decide: L1 needs a task verb + object, L2 needs a
	// leaning window. "那件事后来如何" carries no signal at all.
	dec := New(cfg).Decide(context.Background(), in("那件事后来如何"))
	if stub.callCount() != 0 {
		t.Fatalf("classifier calls = %d, want 0 while L3 is disabled", stub.callCount())
	}
	if dec.State != StateQuiet {
		t.Fatalf("state = %s, want quiet (conservative default)", dec.State)
	}
}

// TestDecide_L3AwakensUndecidedTurn pins that an enabled L3 layer turns an
// otherwise undecided turn into a wake with the classifier's own confidence, and
// advertises the awake tool set.
func TestDecide_L3AwakensUndecidedTurn(t *testing.T) {
	stub := &stubClassifier{verdict: Judgment{IsTask: true, TaskKind: "query", Confidence: 0.82}}
	dec := New(l3Config(stub, time.Minute)).Decide(context.Background(), in("那件事后来如何"))

	if stub.callCount() != 1 {
		t.Fatalf("classifier calls = %d, want 1", stub.callCount())
	}
	if dec.State != StateAwake {
		t.Fatalf("state = %s, want awake (L3 verdict)", dec.State)
	}
	if dec.Confidence != 0.82 {
		t.Fatalf("confidence = %v, want the classifier's 0.82", dec.Confidence)
	}
	if dec.Judgment.IsTask != true {
		t.Errorf("judgment = %+v, want the classifier's isTask=true written back for L4", dec.Judgment)
	}
	if !contains(dec.AllowedTools, "web-search") {
		t.Errorf("allowed = %v, want the awake set including web-search", dec.AllowedTools)
	}
}

// TestDecide_L3ComplexKindWakesFull pins the quantified gate's upper branch: a
// "complex" task kind maps to the full state rather than awake.
func TestDecide_L3ComplexKindWakesFull(t *testing.T) {
	stub := &stubClassifier{verdict: Judgment{IsTask: true, TaskKind: taskKindComplex, Confidence: 0.9}}
	dec := New(l3Config(stub, time.Minute)).Decide(context.Background(), in("那件事后来如何"))
	if dec.State != StateFull {
		t.Fatalf("state = %s, want full for a complex task kind", dec.State)
	}
}

// TestDecide_L3LowConfidenceIsUndecided pins the conservative gate: a verdict the
// model is unsure about must not wake anything, and must not be written back as a
// task either (the L4 write-back feeds the learning loop, so a hesitant verdict
// recorded as a task would teach the wrong habit).
func TestDecide_L3LowConfidenceIsUndecided(t *testing.T) {
	stub := &stubClassifier{verdict: Judgment{IsTask: true, Confidence: 0.3}}
	dec := New(l3Config(stub, time.Minute)).Decide(context.Background(), in("那件事后来如何"))
	if stub.callCount() != 1 {
		t.Fatalf("classifier calls = %d, want 1", stub.callCount())
	}
	if dec.State != StateQuiet {
		t.Fatalf("state = %s, want quiet (below-threshold verdict is undecided)", dec.State)
	}
	if dec.Judgment.IsTask {
		t.Fatalf("judgment = %+v, want isTask=false (a below-threshold verdict is not a task)", dec.Judgment)
	}
}

// TestDecide_L3ClassifierErrorKeepsConservativeDefault pins that a model failure
// is reported as "no verdict" rather than crashing or waking tools.
func TestDecide_L3ClassifierErrorKeepsConservativeDefault(t *testing.T) {
	stub := &stubClassifier{err: errors.New("upstream down")}
	dec := New(l3Config(stub, time.Minute)).Decide(context.Background(), in("那件事后来如何"))
	if dec.State != StateQuiet {
		t.Fatalf("state = %s, want quiet after a classifier error", dec.State)
	}
}

// TestDecide_L3CacheReusesVerdict pins the L3 output cache (裁决 14.4.4): the same
// turn text costs one model call inside the TTL, and a different turn still costs
// its own call.
func TestDecide_L3CacheReusesVerdict(t *testing.T) {
	stub := &stubClassifier{verdict: Judgment{IsTask: true, Confidence: 0.9}}
	d := New(l3Config(stub, time.Minute))
	ctx := context.Background()

	for i := 0; i < 3; i++ {
		if dec := d.Decide(ctx, in("那件事后来如何")); dec.State != StateAwake {
			t.Fatalf("call %d state = %s, want awake", i, dec.State)
		}
	}
	if got := stub.callCount(); got != 1 {
		t.Fatalf("classifier calls = %d, want 1 (cached verdict reused)", got)
	}
	d.Decide(ctx, in("那件事后来如何？"))
	if got := stub.callCount(); got != 2 {
		t.Fatalf("classifier calls = %d, want 2 (different text is not cached)", got)
	}
}

// TestL3Cache_ExpiredEntryIsReclassified pins the TTL bound itself.
func TestL3Cache_ExpiredEntryIsReclassified(t *testing.T) {
	stub := &stubClassifier{verdict: Judgment{IsTask: true, Confidence: 0.9}}
	c := newL3Cache(stub, time.Minute)
	ctx := context.Background()
	if _, err := c.classify(ctx, "那件事后来如何"); err != nil {
		t.Fatalf("classify: %v", err)
	}
	// Backdate the stored entry past the TTL.
	c.mu.Lock()
	for k, e := range c.entries {
		e.at = time.Now().Add(-2 * time.Minute)
		c.entries[k] = e
	}
	c.mu.Unlock()
	if _, err := c.classify(ctx, "那件事后来如何"); err != nil {
		t.Fatalf("classify: %v", err)
	}
	if got := stub.callCount(); got != 2 {
		t.Fatalf("classifier calls = %d, want 2 (expired entry reclassified)", got)
	}
}

// TestL3Cache_EmptyTextIsNotClassified pins that an empty turn is a sentinel
// error rather than a model call.
func TestL3Cache_EmptyTextIsNotClassified(t *testing.T) {
	stub := &stubClassifier{verdict: Judgment{IsTask: true, Confidence: 0.9}}
	c := newL3Cache(stub, time.Minute)
	if _, err := c.classify(context.Background(), "   "); !errors.Is(err, ErrEmptyTurn) {
		t.Fatalf("err = %v, want ErrEmptyTurn", err)
	}
	if stub.callCount() != 0 {
		t.Fatalf("classifier calls = %d, want 0", stub.callCount())
	}
}

// TestParseL3Judgment pins the wire parsing: a fenced JSON reply is accepted, a
// prose reply is an error, and a hallucinated confidence is clamped.
func TestParseL3Judgment(t *testing.T) {
	ok, err := parseL3Judgment("```json\n{\"isTask\":true,\"taskKind\":\"query\",\"confidence\":0.7}\n```")
	if err != nil {
		t.Fatalf("parseL3Judgment: %v", err)
	}
	if !ok.IsTask || ok.TaskKind != "query" || ok.Confidence != 0.7 {
		t.Fatalf("parsed = %+v, want isTask=true taskKind=query confidence=0.7", ok)
	}
	if _, err := parseL3Judgment("我觉得这是一个任务"); err == nil {
		t.Fatal("prose reply parsed without error, want failure")
	}
	if got := clampUnit(7.5); got != 1 {
		t.Errorf("clampUnit(7.5) = %v, want 1", got)
	}
}