package engine

import (
	"bytes"
	"reflect"
	"strings"
	"testing"

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

func TestSequenceHistoryReplaysAppendAtAssignedIndexes(t *testing.T) {
	policy := sequencePolicy{identityFields: map[string]string{"/records": "id", "/other": "id"}}
	first := parseCompositionDocument(t, "source-1", "records: [{id: a, value: first}]\nother: [{id: x}]\n")
	second := parseCompositionDocument(t, "source-2", "records: [{id: b, value: second}]\nother: [{id: y}]\n")
	composed, diagnostics := composeDocumentsWithPolicy(policy, first, second)
	if len(diagnostics) != 0 {
		t.Fatalf("compose diagnostics = %#v", diagnostics)
	}
	for applicationIndex, application := range composed.applications {
		for path, want := range map[string]int{"/records": 1, "/other": 1} {
			sequence, present := documentAtPath(application.value, mustParsePath(t, path))
			if !present || sequence.Kind != document.Sequence || len(sequence.Sequence) != want {
				t.Errorf("application %d retained %s = %#v, %v; want one source fragment item", applicationIndex, path, sequence, present)
			}
		}
	}

	working := parseCompositionDocument(t, "defaults", "records: [{id: default}]\nother: [{id: default}]\n")
	index := new(mappingIndex)
	for _, application := range composed.applications {
		applyHistoryApplication(&working, application, index)
	}
	for path, want := range map[string][]string{
		"/records": {"a", "b"},
		"/other":   {"x", "y"},
	} {
		sequence, present := documentAtPath(working, mustParsePath(t, path))
		if !present || sequence.Kind != document.Sequence || len(sequence.Sequence) != len(want) {
			t.Fatalf("replayed %s = %#v", path, sequence)
		}
		for itemIndex, id := range want {
			field := sequence.Sequence[itemIndex].Mapping[0].Value.Text
			if field != id {
				t.Errorf("replayed %s[%d].id = %q, want %q", path, itemIndex, field, id)
			}
		}
	}

	application := composed.applications[1]
	cloned := cloneHistoryApplications(composed.applications)
	cloned[1].sequences[0].path.segments[0].key = "mutated"
	if composed.applications[1].sequences[0].path.String() != "/records" {
		t.Fatal("cloned sequence history path aliases its source")
	}
	addedPath := Keys("records").Index(1).Key("value")
	if operation, relevant := applicationOperationPath(application, addedPath, nil); !relevant || operation.String() != addedPath.String() {
		t.Fatalf("appended value operation = %s, %v", operation.String(), relevant)
	}
	if _, relevant := applicationOperationPath(application, Keys("records").Index(0).Key("value"), nil); relevant {
		t.Fatal("later contribution was reported as changing an earlier record")
	}
	origin := historyApplicationOrigin(application, addedPath, nil)
	if len(origin.Locations) != 1 || origin.Locations[0].SourceID != "source-2" {
		t.Fatalf("appended value origin = %#v", origin)
	}
	overlay := historyApplication{
		layer: LayerOverlay,
		value: parseCompositionDocument(t, "overlay", "records: []\n"),
	}
	applyHistoryApplication(&working, overlay, index)
	replaced, present := documentAtPath(working, Keys("records"))
	if !present || replaced.Kind != document.Sequence || len(replaced.Sequence) != 0 {
		t.Fatalf("ordinary later list replacement = %#v, %v", replaced, present)
	}
}

func TestSequenceHistoryPreservesTierReplacementAndEmptyLists(t *testing.T) {
	policy := sequencePolicy{identityFields: map[string]string{"/records": "id", "/independent": "id"}}
	first, diagnostics := composeDocumentsWithPolicy(policy,
		parseCompositionDocument(t, "underlay-1a", "records: [{id: shared}]\nindependent: [{id: x}]\n"),
		parseCompositionDocument(t, "underlay-1b", "records: [{id: lower}]\n"),
	)
	if len(diagnostics) != 0 {
		t.Fatalf("first tier diagnostics = %#v", diagnostics)
	}
	for index := range first.applications {
		first.applications[index].layer = LayerUnderlay
	}
	second, diagnostics := composeDocumentsWithPolicy(policy,
		parseCompositionDocument(t, "underlay-2", "records: [{id: shared}]\nindependent: []\n"),
	)
	if len(diagnostics) != 0 {
		t.Fatalf("second tier diagnostics = %#v", diagnostics)
	}
	main, diagnostics := composeDocumentsWithPolicy(policy,
		parseCompositionDocument(t, "main", "records: []\n"),
	)
	if len(diagnostics) != 0 {
		t.Fatalf("main diagnostics = %#v", diagnostics)
	}

	assembly := newAssemblyAccumulator(first)
	if diagnostics := assembly.applyOverlay(second.root, second.origins, second.applications, LayerUnderlay); len(diagnostics) != 0 {
		t.Fatalf("second tier handoff diagnostics = %#v", diagnostics)
	}
	if diagnostics := assembly.applyOverlay(main.root, main.origins, main.applications, LayerBase); len(diagnostics) != 0 {
		t.Fatalf("main handoff diagnostics = %#v", diagnostics)
	}
	if len(assembly.current.applications) != 4 {
		t.Fatalf("retained source applications = %d, want 4", len(assembly.current.applications))
	}

	working := parseCompositionDocument(t, "defaults", "records: [{id: default}]\nindependent: [{id: default}]\n")
	index := new(mappingIndex)
	for _, application := range assembly.current.applications {
		applyHistoryApplication(&working, application, index)
	}
	for path, want := range map[string][]string{
		"/records":     nil,
		"/independent": nil,
	} {
		sequence, present := documentAtPath(working, mustParsePath(t, path))
		if !present || sequence.Kind != document.Sequence || len(sequence.Sequence) != len(want) {
			t.Errorf("replayed replacement %s = %#v, want an explicit empty sequence", path, sequence)
		}
	}

	// The same identity may appear in separate tiers, while each tier still
	// retains its individual source applications for explanation replay.
	if got := []Layer{assembly.current.applications[0].layer, assembly.current.applications[1].layer,
		assembly.current.applications[2].layer, assembly.current.applications[3].layer}; !reflect.DeepEqual(got, []Layer{LayerUnderlay, LayerUnderlay, LayerUnderlay, LayerBase}) {
		t.Fatalf("application layers = %#v", got)
	}
}

func TestHistoryMergeSupportsSemanticIndexedPrefixes(t *testing.T) {
	root := parseCompositionDocument(t, "base", "records: [{id: one, helper: {value: old}}]\n")
	application := historyApplication{
		path:  Keys("records").Index(0).Key("helper"),
		value: parseCompositionDocument(t, "helper", "value: new\n"),
	}
	applyHistoryApplication(&root, application, new(mappingIndex))
	value, present := documentAtPath(root, Keys("records").Index(0).Key("helper").Key("value"))
	if !present || value.Text != "new" {
		t.Fatalf("indexed helper replay = %#v, %v", value, present)
	}
}

func TestProjectedSequenceHistoryAgreesAcrossMetadataAndExplanation(t *testing.T) {
	policy := sequencePolicy{identityFields: map[string]string{"/records": "id"}}
	composed, diagnostics := composeDocumentsWithPolicy(policy,
		parseCompositionDocument(t, "first", "records: [{id: first, token: public}]"),
		parseCompositionDocument(t, "second", "records: [{id: second, token: private}]"),
	)
	if len(diagnostics) != 0 {
		t.Fatalf("compose diagnostics = %#v", diagnostics)
	}
	path := Keys("records").Index(1).Key("token")
	var metadata Metadata
	finalizeMetadataPaths(&metadata, composed.root, composed.applications)
	if !metadata.hasHistoricalPath(path) {
		t.Fatalf("projected metadata omitted shifted path %s: %#v", path, metadata.historicalPaths)
	}

	inspection := &Inspection{
		metadata: metadata, baseline: &document.Node{Kind: document.Mapping},
		input: composed.root, final: composed.root, applications: composed.applications,
	}
	inspection.secrets = classifySecretPaths(nil, func(candidate Path) bool {
		return reflect.DeepEqual(candidate, path)
	}, metadata, composed.root, composed.applications)
	explanation, ok := inspection.Explain(path)
	if !ok || !explanation.Effective.Redacted {
		t.Fatalf("shifted explanation = %#v, %v", explanation, ok)
	}
	var foundSecondOrigin bool
	for _, change := range explanation.History {
		for _, location := range change.Origin.Locations {
			foundSecondOrigin = foundSecondOrigin || location.SourceID == "second"
		}
	}
	if !foundSecondOrigin {
		t.Fatalf("shifted history lost second source attribution: %#v", explanation.History)
	}
	var rendered bytes.Buffer
	if err := inspection.WriteExplanation(&rendered, path); err != nil {
		t.Fatal(err)
	}
	if !strings.Contains(rendered.String(), `path: "/records/1/token"`) || strings.Contains(rendered.String(), "private") {
		t.Fatalf("shifted explanation rendering is incomplete or unsafe: %s", rendered.String())
	}
}

func TestReplacedProjectedSensitiveRecordRemainsRedacted(t *testing.T) {
	policy := sequencePolicy{identityFields: map[string]string{"/records": "id"}}
	composed, diagnostics := composeDocumentsWithPolicy(policy,
		parseCompositionDocument(t, "first", "records: [{id: first, token: public}]"),
		parseCompositionDocument(t, "second", "records: [{id: second, token: PRIVATE-RECORD-CANARY}]"),
	)
	if len(diagnostics) != 0 {
		t.Fatalf("compose diagnostics = %#v", diagnostics)
	}
	applications := append([]historyApplication(nil), composed.applications...)
	applications = append(applications, historyApplication{
		layer: LayerOverlay,
		value: parseCompositionDocument(t, "replacement", "records: [{id: replacement, token: visible}]"),
	})
	final := applications[len(applications)-1].value
	path := Keys("records").Index(1).Key("token")
	var metadata Metadata
	finalizeMetadataPaths(&metadata, final, applications)
	inspection := &Inspection{
		metadata: metadata, baseline: &document.Node{Kind: document.Mapping},
		input: final, final: final, applications: applications,
	}
	inspection.secrets = classifySecretPaths(nil, func(candidate Path) bool {
		return reflect.DeepEqual(candidate, path)
	}, metadata, final, applications)
	explanation, ok := inspection.Explain(path)
	if !ok || explanation.Effective.Present {
		t.Fatalf("replaced shifted record explanation = %#v, %v", explanation, ok)
	}
	var rendered bytes.Buffer
	if err := inspection.WriteExplanation(&rendered, path); err != nil {
		t.Fatal(err)
	}
	if strings.Contains(rendered.String(), "PRIVATE-RECORD-CANARY") || !strings.Contains(rendered.String(), "[REDACTED]") {
		t.Fatalf("replaced sensitive history leaked or was not redacted: %s", rendered.String())
	}
}

func TestSequenceHistoryReplaysCombinationEvidence(t *testing.T) {
	tests := []struct {
		name      string
		operation sequenceMode
		lower     string
		higher    string
	}{
		{
			name:      "append",
			operation: sequenceModeAppend,
			lower:     "records: [{id: first}, {id: last}]\n",
			higher:    "records: [{id: added}]\n",
		},
		{
			name:      "upsert",
			operation: sequenceModeUpsert,
			lower: `records:
  - id: first
    label: same
    nested: {removed: lower}
  - id: middle
  - id: last
    nested: {removed: lower}
`,
			higher: `records:
  - id: last
    nested: {kept: higher}
  - id: first
    label: same
  - id: added
`,
		},
		{
			name:      "replace",
			operation: sequenceModeReplace,
			lower:     "records: [{id: discarded}]\n",
			higher:    "records: [{id: replacement}]\n",
		},
	}
	for _, test := range tests {
		t.Run(test.name, func(t *testing.T) {
			lowerRoot := parseCompositionDocument(t, "lower", test.lower)
			higherRoot := parseCompositionDocument(t, "higher", test.higher)
			lower, _ := documentAtPath(lowerRoot, Keys("records"))
			higher, _ := documentAtPath(higherRoot, Keys("records"))
			fields := []string(nil)
			if test.operation != sequenceModeReplace {
				fields = []string{"id"}
			}
			combined, diagnostics := combineSequence(lower, higher, sequenceCombinationPolicy(test.operation, fields...), sequenceCombinationContext{destination: Keys("records")})
			if len(diagnostics) != 0 {
				t.Fatalf("combine diagnostics = %#v", diagnostics)
			}

			mode := sequenceHistoryMapped
			if test.operation == sequenceModeReplace {
				mode = sequenceHistoryReplace
			}
			length := 0
			if mode == sequenceHistoryReplace {
				length = len(combined.higherItems)
			}
			application := historyApplication{
				layer: LayerOverlay,
				value: higherRoot,
				sequences: []sequenceHistoryContribution{{
					path: Keys("records"), mode: mode, length: length,
					items: combined.higherItems, replacements: combined.replacements,
				}},
			}
			application.sequencesByPath = indexSequenceHistoryContributions(application.sequences)
			replayed := document.Clone(lowerRoot)
			applyHistoryApplication(&replayed, application, new(mappingIndex))
			got, present := documentAtPath(replayed, Keys("records"))
			if !present || !reflect.DeepEqual(got.Sequence, combined.value.Sequence) {
				t.Fatalf("replayed sequence = %#v, want combination = %#v", got, combined.value.Sequence)
			}
		})
	}
}

func TestMappedSequenceHistoryReplacesWholeRecordsAndKeepsDisplacedEvidence(t *testing.T) {
	lowerRoot := parseCompositionDocument(t, "lower", `records:
  - id: first
    label: same
  - id: middle
  - id: last
    nested: {removed: LOWER-CANARY}
`)
	higherRoot := parseCompositionDocument(t, "higher", `records:
  - id: last
    nested: {kept: higher}
  - id: first
    label: same
  - id: added
`)
	lower, _ := documentAtPath(lowerRoot, Keys("records"))
	higher, _ := documentAtPath(higherRoot, Keys("records"))
	combined, diagnostics := combineSequence(
		lower, higher,
		sequenceCombinationPolicy(sequenceModeUpsert, "id"),
		sequenceCombinationContext{destination: Keys("records")},
	)
	if len(diagnostics) != 0 {
		t.Fatal(diagnostics)
	}
	application := historyApplication{
		layer: LayerOverlay, value: higherRoot,
		sequences: []sequenceHistoryContribution{{
			path: Keys("records"), mode: sequenceHistoryMapped,
			items: combined.higherItems, replacements: combined.replacements,
		}},
	}
	application.sequencesByPath = indexSequenceHistoryContributions(application.sequences)
	clonedApplications := cloneHistoryApplications([]historyApplication{application})
	clonedApplications[0].sequences[0].items[0].outputIndex = 99
	clonedApplications[0].sequences[0].replacements[0].outputIndex = 99
	if application.sequences[0].items[0].outputIndex == 99 || application.sequences[0].replacements[0].outputIndex == 99 {
		t.Fatal("cloned mapped history aliases its source projections")
	}

	query := Keys("records").Index(2).Key("nested").Key("removed")
	operationPath, relevant := applicationOperationPath(application, query, nil)
	if !relevant || operationPath.String() != "/records/2" {
		t.Fatalf("removed descendant operation = %s, %v", operationPath.String(), relevant)
	}
	localPath, ok := historyApplicationLocalPath(application, Keys("records").Index(2).Key("nested").Key("kept"))
	if !ok || localPath.String() != "/records/0/nested/kept" {
		t.Fatalf("mapped effective path localizes to %s, %v", localPath.String(), ok)
	}
	origin := historyApplicationOrigin(application, operationPath, nil)
	if len(origin.Locations) != 1 || origin.Locations[0].SourceID != "higher" {
		t.Fatalf("replacement operation origin = %#v", origin)
	}
	var walkedMappedPath bool
	walkHistoryApplication(application, func(local, effective Path, _ *document.Node) {
		if local.String() == "/records/0/nested/kept" && effective.String() == "/records/2/nested/kept" {
			walkedMappedPath = true
		}
	})
	if !walkedMappedPath {
		t.Fatal("history walk did not project a noncontiguous incoming item")
	}

	replayed := document.Clone(lowerRoot)
	applyHistoryApplication(&replayed, application, new(mappingIndex))
	sequence, _ := documentAtPath(replayed, Keys("records"))
	if _, present := documentAtPath(sequence.Sequence[2], Keys("nested", "removed")); present {
		t.Fatal("whole-record replacement retained an omitted descendant")
	}
	if value, present := documentAtPath(sequence.Sequence[2], Keys("nested", "kept")); !present || value.Text != "higher" {
		t.Fatalf("replacement descendant = %#v, %v", value, present)
	}
	if sequence.Sequence[1].Mapping[0].Value.Text != "middle" {
		t.Fatal("unchanged neighboring record moved or changed")
	}
	if value, present := documentAtPath(lowerRoot, Keys("records").Index(2).Key("nested").Key("removed")); !present || value.Text != "LOWER-CANARY" {
		t.Fatalf("displaced lower contribution was not retained as raw history: %#v, %v", value, present)
	}
	if got := application.sequences[0].replacements; !reflect.DeepEqual(got, combined.replacements) || len(got) != 2 {
		t.Fatalf("replacement evidence lost equal-valued or noncontiguous events: %#v", got)
	}
}

func mustParsePath(t *testing.T, value string) Path {
	t.Helper()
	path, err := ParsePath(value)
	if err != nil {
		t.Fatal(err)
	}
	return path
}