package engine

import (
	"bytes"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"reflect"
	"strings"
	"testing"

	"gitea.maximumdirect.net/eric/ConfigKit/internal/document"
)

type explanationConcurrency struct {
	Transcription struct {
		Concurrency int `yaml:"concurrency"`
	} `yaml:"transcription"`
}

func TestExplainShowsDefaultBaseAndEffectiveOverlayValue(t *testing.T) {
	directory := t.TempDir()
	mainPath := writeImportFile(t, directory, "config.yml", "configkit:\n  imports: [{path: transcription.yml}]\n")
	writeImportFile(t, directory, "transcription.yml", "transcription:\n  concurrency: 8\n")
	writeImportFile(t, directory, filepath.Join("overlays", "testing.yml"), "transcription:\n  concurrency: 1\n")
	result, err := testLoad[explanationConcurrency](File(mainPath), Options[explanationConcurrency]{
		Imports: true, Overlay: "testing",
		Definition: Definition[explanationConcurrency]{Defaults: func() explanationConcurrency {
			value := explanationConcurrency{}
			value.Transcription.Concurrency = 4
			return value
		}},
	})
	if err != nil {
		t.Fatal(err)
	}
	explanation, ok := result.Explain(Keys("transcription", "concurrency"))
	if !ok {
		t.Fatal("known path was not explained")
	}
	if got := explanationValues(explanation); !reflect.DeepEqual(got, []string{"4\n", "8\n", "1\n"}) {
		t.Fatalf("history values = %#v", got)
	}
	if explanation.Effective.YAML != "1\n" || explanation.Origin.Layer != LayerOverlay ||
		len(explanation.Origin.Locations) != 1 || explanation.Origin.Locations[0].SourceID != "source-3" ||
		explanation.Origin.Locations[0].Line != 2 {
		t.Fatalf("effective explanation = %#v", explanation)
	}
	var rendered bytes.Buffer
	if err := result.WriteExplanation(&rendered, Keys("transcription", "concurrency")); err != nil ||
		!strings.Contains(rendered.String(), `layer="overlay"`) ||
		!strings.Contains(rendered.String(), `label="overlays/testing.yml"`) {
		t.Fatalf("rendered explanation = %v\n%s", err, rendered.String())
	}
}

type explanationConfig struct {
	Concurrency int               `yaml:"concurrency"`
	Equal       string            `yaml:"equal"`
	Limit       int               `yaml:"limit"`
	Items       []string          `yaml:"items"`
	Labels      map[string]string `yaml:"labels"`
	Dynamic     any               `yaml:"dynamic"`
	Maybe       *string           `yaml:"maybe"`
	Empty       []string          `yaml:"empty"`
	Credential  Secret            `yaml:"credential"`
	Classified  Secret            `yaml:"classified"`
	DerivedA    string            `yaml:"derived_a"`
	DerivedB    string            `yaml:"derived_b"`
}

func TestExplainReplaysCLIResolutionContainersAndSafeHistoricalValues(t *testing.T) {
	directory := t.TempDir()
	mainPath := writeImportFile(t, directory, "config.yml", `concurrency: 8
equal: same
limit: wrong-before-overlay
items: [base, removed]
labels: {base: retained}
dynamic: {retired: HISTORICAL_EXPLAIN_CANARY, public: visible}
credential: APP_SECRET
classified: APP_SECRET
`)
	writeImportFile(t, directory, filepath.Join("overlays", "testing.yml"), `concurrency: 1
equal: same
limit: 7
items: [overlay]
labels: {overlay: retained}
dynamic: selected
`)
	result, err := testLoadWithSecretLookup(File(mainPath), func(name string) (string, bool) {
		if name != "APP_SECRET" {
			t.Fatalf("secret lookup = %q", name)
		}
		return "RESOLVED_EXPLAIN_CANARY", true
	}, Options[explanationConfig]{
		Overlay: "testing",
		Overrides: []Override{
			{Path: Keys("concurrency"), Value: 2, Flag: "--concurrency"},
			{Path: Keys("equal"), Value: "same", Flag: "--equal"},
			{Path: Keys("items"), Value: []any{"cli", "restored"}, Flag: "--items"},
			{Path: Keys("labels"), Value: map[string]any{"cli": "retained"}, Flag: "--label"},
		},
		Definition: Definition[explanationConfig]{
			Defaults: func() explanationConfig {
				return explanationConfig{
					Concurrency: 4, Equal: "same", Labels: map[string]string{"default": "retained"},
					Maybe: nil, Empty: []string{}, Credential: SecretEnv("APP_SECRET"), Classified: SecretEnv("APP_SECRET"),
				}
			},
			Secret: func(path Path) bool {
				return path.String() == "/dynamic/retired" || path.String() == "/classified"
			},
			Resolve: func(configuration *explanationConfig, resolution *Resolution) error {
				Normalize(resolution, Keys("concurrency"), &configuration.Concurrency, 3,
					"normalized\nconcurrency", Keys("labels"))
				Normalize(resolution, Keys("equal"), &configuration.Equal, "same", "record equal value")
				Normalize(resolution, Keys("derived_a"), &configuration.DerivedA, "DERIVED_EXPLAIN_A",
					"derived cycle a", Keys("derived_b"))
				Normalize(resolution, Keys("derived_b"), &configuration.DerivedB, "DERIVED_EXPLAIN_B",
					"derived cycle b", Keys("derived_a"), Keys("dynamic"))
				return nil
			},
		},
	})
	if err != nil {
		t.Fatal(err)
	}

	concurrency, ok := result.Explain(Keys("concurrency"))
	if !ok {
		t.Fatal("concurrency was not explained")
	}
	if got := explanationValues(concurrency); !reflect.DeepEqual(got, []string{"4\n", "8\n", "1\n", "2\n", "3\n"}) {
		t.Fatalf("concurrency history = %#v", got)
	}
	if got := historyValueLayers(concurrency); !reflect.DeepEqual(got, []Layer{LayerDefault, LayerBase, LayerOverlay, LayerCLI, LayerResolution}) {
		t.Fatalf("concurrency layers = %#v", got)
	}
	if concurrency.History[4].Before.YAML != "2\n" || concurrency.History[4].Reasons[0] != "normalized\nconcurrency" ||
		concurrency.History[4].Dependencies[0].String() != "/labels" {
		t.Fatalf("resolution history = %#v", concurrency.History[4])
	}

	equal, _ := result.Explain(Keys("equal"))
	if len(equal.History) != 5 {
		t.Fatalf("equal writes were lost: %#v", equal.History)
	}
	for _, change := range equal.History[1:] {
		if change.Before.YAML != "same\n" || change.After.YAML != "same\n" {
			t.Fatalf("equal replacement = %#v", change)
		}
	}

	limit, _ := result.Explain(Keys("limit"))
	if got := explanationValues(limit); !reflect.DeepEqual(got, []string{"0\n", "wrong-before-overlay\n", "7\n"}) {
		t.Fatalf("overridden invalid input was not retained: %#v", got)
	}
	removed, ok := result.Explain(Keys("dynamic", "retired"))
	if !ok || removed.Effective.Present || len(removed.History) < 2 {
		t.Fatalf("removed path = %#v, %v", removed, ok)
	}
	for _, change := range removed.History {
		if strings.Contains(change.Before.YAML+change.After.YAML, "HISTORICAL_EXPLAIN_CANARY") {
			t.Fatalf("historical secret escaped redaction: %#v", change)
		}
	}
	if !removed.History[0].After.Redacted || removed.History[len(removed.History)-1].After.Present {
		t.Fatalf("removed secret history = %#v", removed.History)
	}
	dynamic, _ := result.Explain(Keys("dynamic"))
	if len(dynamic.History) < 3 || !dynamic.History[1].After.Redacted ||
		strings.Contains(dynamic.History[1].After.YAML, "HISTORICAL_EXPLAIN_CANARY") {
		t.Fatalf("container redaction history = %#v", dynamic.History)
	}

	items, _ := result.Explain(Keys("items"))
	if len(items.History) != 4 || !strings.Contains(items.History[1].After.YAML, "removed") ||
		strings.Contains(items.History[2].After.YAML, "removed") || !strings.Contains(items.History[3].After.YAML, "restored") {
		t.Fatalf("atomic sequence history = %#v", items.History)
	}
	removedIndex, ok := result.Explain(Keys("items").Index(1))
	if !ok || !removedIndex.History[1].Before.Present || removedIndex.History[1].After.Present ||
		!removedIndex.History[2].After.Present {
		t.Fatalf("sequence descendant history = %#v", removedIndex.History)
	}
	labels, _ := result.Explain(Keys("labels"))
	if len(labels.History) != 4 || !strings.Contains(labels.Effective.YAML, "default: retained") ||
		!strings.Contains(labels.Effective.YAML, "overlay: retained") || !strings.Contains(labels.Effective.YAML, "cli: retained") {
		t.Fatalf("composite mapping history = %#v", labels)
	}
	if labels.Origin.Layer != LayerCLI || len(labels.Origin.Locations) != 3 {
		t.Fatalf("composite effective origin = %#v", labels.Origin)
	}

	maybe, _ := result.Explain(Keys("maybe"))
	empty, _ := result.Explain(Keys("empty"))
	if !maybe.Effective.Present || maybe.Effective.YAML != "null\n" || !empty.Effective.Present || empty.Effective.YAML != "[]\n" {
		t.Fatalf("null/empty snapshots = maybe %#v empty %#v", maybe.Effective, empty.Effective)
	}
	credential, _ := result.Explain(Keys("credential"))
	if credential.SecretReference == nil || credential.SecretReference.Name != "APP_SECRET" || credential.Effective.YAML != "APP_SECRET\n" {
		t.Fatalf("secret reference = %#v", credential)
	}
	classified, _ := result.Explain(Keys("classified"))
	if classified.SecretReference != nil || !classified.Effective.Redacted ||
		strings.Contains(classified.Effective.YAML, "APP_SECRET") {
		t.Fatalf("classified secret reference = %#v", classified)
	}
	var derivedExplanations []Explanation
	for _, path := range []Path{Keys("derived_a"), Keys("derived_b")} {
		derived, _ := result.Explain(path)
		if !derived.Effective.Redacted || strings.Contains(derived.Effective.YAML, "DERIVED_EXPLAIN") {
			t.Fatalf("dependency closure at %s = %#v", path.String(), derived)
		}
		derivedExplanations = append(derivedExplanations, derived)
	}

	formatted := fmt.Sprintf("%v %#v %v", removed, credential, derivedExplanations)
	encoded, marshalErr := json.Marshal(append([]Explanation{removed, credential, classified}, derivedExplanations...))
	if marshalErr != nil || strings.Contains(formatted+string(encoded), "RESOLVED_EXPLAIN_CANARY") ||
		strings.Contains(formatted+string(encoded), "HISTORICAL_EXPLAIN_CANARY") ||
		strings.Contains(formatted+string(encoded), "DERIVED_EXPLAIN") {
		t.Fatalf("public records disclosed a canary: %s %s", formatted, encoded)
	}

	concurrency.Path.segments[0].key = "mutated"
	concurrency.History[4].Reasons[0] = "mutated"
	concurrency.History[4].Dependencies[0].segments[0].key = "mutated"
	result.Config.Concurrency = 99
	again, _ := result.Explain(Keys("concurrency"))
	if again.Path.String() != "/concurrency" || again.Effective.YAML != "3\n" ||
		again.History[4].Reasons[0] != "normalized\nconcurrency" ||
		again.History[4].Dependencies[0].String() != "/labels" {
		t.Fatalf("returned explanation aliased internal history: %#v", again)
	}

	var first, second bytes.Buffer
	if err := result.WriteExplanation(&first, Keys("concurrency")); err != nil {
		t.Fatal(err)
	}
	if err := result.WriteExplanation(&second, Keys("concurrency")); err != nil || first.String() != second.String() {
		t.Fatalf("nondeterministic rendering: %v\n%s\n%s", err, first.String(), second.String())
	}
	if strings.Contains(first.String(), "\nconcurrency\"") || !strings.Contains(first.String(), `"normalized\nconcurrency"`) {
		t.Fatalf("reason controls were not escaped: %q", first.String())
	}
	unknownOutput := bytes.NewBufferString("unchanged")
	if err := result.WriteExplanation(unknownOutput, Keys("unknown")); !errors.Is(err, errExplanationUnknownPath) || unknownOutput.String() != "unchanged" {
		t.Fatalf("unknown writer = %q, %v", unknownOutput.String(), err)
	}
	if _, ok := result.Explain(Keys("items").Index(-1)); ok {
		t.Fatal("malformed path was explained")
	}
	wantWriteError := errors.New("write failed")
	if err := result.WriteExplanation(errorWriter{err: wantWriteError}, Keys("concurrency")); !errors.Is(err, wantWriteError) {
		t.Fatalf("writer error = %v", err)
	}
	if err := result.WriteExplanation(shortWriter{}, Keys("concurrency")); !errors.Is(err, io.ErrShortWrite) {
		t.Fatalf("short writer error = %v", err)
	}
	var invalidInput bytes.Buffer
	if err := result.WriteExplanation(&invalidInput, Keys("limit")); err != nil ||
		!strings.Contains(invalidInput.String(), "policy-validated input") ||
		strings.Contains(invalidInput.String(), "wrong-before-overlay\n    source: layer=\"base\"\n    before (canonical typed)") {
		t.Fatalf("historical representation rendering = %v\n%s", err, invalidInput.String())
	}
}

func TestSecretsBootstrapLoadAndExplanationRemainSeparateAndSafe(t *testing.T) {
	const name = "CONFIGKIT_EXPLAIN_BOOTSTRAP_TEST"
	previous, present := os.LookupEnv(name)
	if err := os.Unsetenv(name); err != nil {
		t.Fatal(err)
	}
	t.Cleanup(func() {
		if present {
			_ = os.Setenv(name, previous)
		} else {
			_ = os.Unsetenv(name)
		}
	})
	directory := t.TempDir()
	writeSecretTestFile(t, directory, name, "BOOTSTRAP_EXPLAIN_CANARY\n")
	report, err := LoadSecretsDir(directory)
	if err != nil || len(report.Entries()) != 1 || report.Entries()[0].Status != SecretFileLoaded {
		t.Fatalf("bootstrap = %#v, %v", report, err)
	}
	type config struct {
		Credential Secret `yaml:"credential"`
	}
	result, err := testLoad[config](Bytes("config.yml", []byte("credential: "+name+"\n")))
	if err != nil {
		t.Fatal(err)
	}
	var output bytes.Buffer
	if err := result.WriteExplanation(&output, Keys("credential")); err != nil {
		t.Fatal(err)
	}
	if !strings.Contains(output.String(), name) || strings.Contains(output.String(), "BOOTSTRAP_EXPLAIN_CANARY") {
		t.Fatalf("explanation mixed bootstrap value into reference report: %s", output.String())
	}
}

func TestHistoryNodeBudgetCountsSharedTreesOnce(t *testing.T) {
	leaf := &document.Node{Kind: document.String, Text: "value"}
	root := &document.Node{Kind: document.Mapping, Mapping: []document.Entry{{Key: "value", Value: leaf}}}
	applications := []historyApplication{{layer: LayerBase, value: root}}
	if !historyNodesWithin(2, root, root, root, applications, nil) {
		t.Fatal("structurally shared history was counted more than once")
	}
	other := document.Clone(root)
	if historyNodesWithin(3, root, other, root, applications, nil) {
		t.Fatal("distinct retained nodes did not consume the budget")
	}
}

func explanationValues(explanation Explanation) []string {
	values := make([]string, len(explanation.History))
	for index, change := range explanation.History {
		values[index] = change.After.YAML
	}
	return values
}

func historyValueLayers(explanation Explanation) []Layer {
	layers := make([]Layer, len(explanation.History))
	for index, change := range explanation.History {
		layers[index] = change.Origin.Layer
	}
	return layers
}

func TestExplanationReconcilesDefaultsAfterInputReplacement(t *testing.T) {
	type cfg struct {
		M map[string]int `yaml:"m"`
	}
	for _, base := range []string{"null", "replaced-text"} {
		for _, cli := range []bool{false, true} {
			t.Run(fmt.Sprintf("%s/cli=%v", base, cli), func(t *testing.T) {
				root := t.TempDir()
				main := writeImportFile(t, root, "main.yml", "m: "+base+"\n")
				opts := Options[cfg]{Definition: Definition[cfg]{Defaults: func() cfg { return cfg{M: map[string]int{"a": 1}} }}}
				if cli {
					opts.Overrides = []Override{{Path: Keys("m"), Value: map[string]any{"b": 2}, Flag: "--m"}}
				} else {
					writeImportFile(t, root, "overlays/p.yml", "m: {b: 2}\n")
					opts.Overlay = "p"
				}
				result, err := testLoad(File(main), opts)
				if err != nil {
					t.Fatal(err)
				}
				for _, path := range []Path{Keys("m"), Keys("m", "a")} {
					explanation, ok := result.Explain(path)
					if !ok {
						t.Fatal("missing explanation")
					}
					last := explanation.History[len(explanation.History)-1]
					if last.After != explanation.Effective || last.Origin.Operation != ChangeDecoding {
						t.Fatalf("history does not reconcile final value: %#v", explanation)
					}
					info, _ := result.Metadata().Lookup(path)
					if last.Origin.Layer != info.Origin.Layer {
						t.Fatal("decoding lost effective origin")
					}
				}
			})
		}
	}
}

func TestIntegerVersionInspectionRetainsInputAndReconcilesTypedValue(t *testing.T) {
	type config struct {
		Version string `yaml:"version"`
	}
	rule := &VersionRule{Path: Keys("version"), Check: func(version Version, _ *Validation) error {
		if version.Text != "4" {
			t.Errorf("version = %#v", version)
		}
		return nil
	}}
	options := Options[config]{Definition: Definition[config]{
		Defaults: func() config { return config{Version: "4"} },
		Version:  rule,
	}}
	first, err := testLoad(Bytes("version.yml", []byte("version: 4\n")), options)
	if err != nil {
		t.Fatal(err)
	}
	second, err := testLoad(Bytes("version.yml", []byte("version: 4\n")), options)
	if err != nil {
		t.Fatal(err)
	}
	if first.Config.Version != "4" || second.Config.Version != "4" {
		t.Fatalf("configurations = %#v / %#v", first.Config, second.Config)
	}
	inputVersion, inputOK := documentAtPath(first.applications[0].value, Keys("version"))
	finalVersion, finalOK := documentAtPath(first.final, Keys("version"))
	if !inputOK || inputVersion.Kind != document.Number || inputVersion.Text != "4" ||
		!finalOK || finalVersion.Kind != document.String || finalVersion.Text != "4" {
		t.Fatalf("input/final = %#v / %#v", inputVersion, finalVersion)
	}

	info, ok := first.Metadata().Lookup(Keys("version"))
	if !ok || !info.Explicit || info.Null || info.Origin.Layer != LayerBase || len(info.Origin.Locations) != 1 ||
		info.Origin.Locations[0].SourceID != "source-1" || info.Origin.Locations[0].Line != 1 {
		t.Fatalf("version metadata = %#v, %v", info, ok)
	}
	explanation, ok := first.Explain(Keys("version"))
	if !ok || explanation.Effective.YAML != "'4'\n" {
		t.Fatalf("version explanation = %#v, %v", explanation, ok)
	}
	foundInput, foundDecoding := false, false
	for _, change := range explanation.History {
		if change.After.YAML == "4\n" && change.Origin.Layer == LayerBase {
			foundInput = true
		}
		if change.Before.YAML == "4\n" && change.After.YAML == "'4'\n" && change.Origin.Operation == ChangeDecoding {
			foundDecoding = true
		}
		if change.Origin.Layer == LayerResolution {
			t.Fatalf("conversion recorded as resolution: %#v", change)
		}
	}
	if !foundInput || !foundDecoding {
		t.Fatalf("version history = %#v", explanation.History)
	}
	paths := first.Metadata().HistoricalPaths()
	foundPath := false
	for _, path := range paths {
		if path.String() == "/version" {
			foundPath = true
		}
	}
	if !foundPath || len(first.Metadata().History(Keys("version"))) < 2 {
		t.Fatalf("historical version paths/history = %#v / %#v", paths, first.Metadata().History(Keys("version")))
	}

	var effective strings.Builder
	if err := first.WriteEffective(&effective); err != nil || effective.String() != "version: '4'\n" {
		t.Fatalf("effective output = %q, %v", effective.String(), err)
	}
	first.Config.Version = "mutated"
	effective.Reset()
	if err := first.WriteEffective(&effective); err != nil || effective.String() != "version: '4'\n" || second.Config.Version != "4" {
		t.Fatalf("detached results = %q / %#v, %v", effective.String(), second.Config, err)
	}
}

func TestSensitiveIntegerVersionStaysRedactedWithoutSecretLookup(t *testing.T) {
	type config struct {
		Version string `yaml:"version"`
	}
	lookups := 0
	result, err := testLoadWithSecretLookup(Bytes("version.yml", []byte("version: 987654321\n")), func(string) (string, bool) {
		lookups++
		return "CREDENTIAL_CANARY", true
	}, Options[config]{Definition: Definition[config]{
		Version: &VersionRule{Path: Keys("version"), Check: func(Version, *Validation) error { return nil }},
		Secret:  func(path Path) bool { return path.String() == "/version" },
	}})
	if err != nil || result.Config.Version != "987654321" || lookups != 0 {
		t.Fatalf("result = %#v, lookups = %d, err = %v", result, lookups, err)
	}
	var effective strings.Builder
	if err := result.WriteEffective(&effective); err != nil {
		t.Fatal(err)
	}
	explanation, ok := result.Explain(Keys("version"))
	formatted := effective.String() + fmt.Sprintf("%#v %#v", explanation, result.Metadata().History(Keys("version")))
	if !ok || !explanation.Effective.Redacted || strings.Contains(formatted, "987654321") || strings.Contains(formatted, "CREDENTIAL_CANARY") {
		t.Fatalf("sensitive inspection = %q / %#v", effective.String(), explanation)
	}
}

func TestExplanationReplaysResolutionAdditionsAndOverlappingIntent(t *testing.T) {
	type cfg struct {
		M map[string]any `yaml:"m"`
	}
	for _, overlap := range []bool{false, true} {
		t.Run(fmt.Sprint(overlap), func(t *testing.T) {
			result, err := testLoad(Bytes("base", []byte("m: {old: 1}\n")), Options[cfg]{Definition: Definition[cfg]{Resolve: func(c *cfg, r *Resolution) error {
				c.M["new"] = map[string]any{"child": int64(7)}
				delete(c.M, "old")
				r.Record(Keys("m", "new"), ChangeDerivedDefault, "add nested", Keys("m", "old"))
				r.Record(Keys("m", "old"), ChangeNormalization, "remove old")
				if overlap {
					r.Record(Keys("m"), ChangeNormalization, "update container")
				}
				return nil
			}}})
			if err != nil {
				t.Fatal(err)
			}
			for _, path := range []Path{Keys("m"), Keys("m", "new"), Keys("m", "new", "child"), Keys("m", "old")} {
				x, ok := result.Explain(path)
				if !ok {
					t.Fatal("missing known history")
				}
				var count int
				for _, v := range x.History {
					if v.Origin.Layer == LayerResolution {
						count++
						if overlap && len(v.Reasons) != 3 {
							t.Fatal("lost overlapping intent")
						}
					}
				}
				if overlap && count != 1 {
					t.Fatalf("overlapping records applied %d times", count)
				}
				last := x.History[len(x.History)-1]
				if last.After != x.Effective {
					t.Fatalf("incorrect replay for %s: %#v", path, x)
				}
			}
		})
	}
}

func TestExplanationReplayDescriptorsRemainDetachedAcrossQueries(t *testing.T) {
	type config struct {
		Count int `yaml:"count"`
	}
	result, err := testLoad(Bytes("resolution-explanation.yml", []byte("count: 1\n")), Options[config]{
		Definition: Definition[config]{Resolve: func(value *config, resolution *Resolution) error {
			value.Count = 2
			resolution.Record(Keys("count"), ChangeNormalization, "normalized", Keys("count"))
			return nil
		}},
	})
	if err != nil {
		t.Fatal(err)
	}
	first, ok := result.Explain(Keys("count"))
	if !ok {
		t.Fatal("missing explanation")
	}
	var firstResolution *ValueChange
	for index := range first.History {
		if first.History[index].Origin.Layer == LayerResolution {
			firstResolution = &first.History[index]
			break
		}
	}
	if firstResolution == nil || len(firstResolution.Reasons) != 1 || len(firstResolution.Dependencies) != 1 {
		t.Fatalf("resolution history = %#v", first.History)
	}
	firstResolution.Reasons[0] = "mutated"
	firstResolution.Dependencies[0].segments[0].key = "mutated"

	second, ok := result.Explain(Keys("count"))
	if !ok {
		t.Fatal("missing repeated explanation")
	}
	for _, change := range second.History {
		if change.Origin.Layer == LayerResolution {
			if !reflect.DeepEqual(change.Reasons, []string{"normalized"}) || len(change.Dependencies) != 1 || change.Dependencies[0].String() != "/count" {
				t.Fatalf("repeated explanation observed caller mutation: %#v", change)
			}
			return
		}
	}
	t.Fatalf("resolution change missing from repeated explanation: %#v", second.History)
}