package engine

import (
	"bytes"
	"strings"
	"testing"

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

func inheritanceInspectionForTest(t *testing.T, sources ...*document.Node) (*Inspection, *inheritanceScope) {
	t.Helper()
	composed, diagnostics := composeDocuments(sources...)
	if len(diagnostics) != 0 {
		t.Fatal(diagnostics)
	}
	return inheritanceInspectionFromComposition(t, composed)
}

func inheritanceInspectionFromComposition(t *testing.T, composed *composedDocument) (*Inspection, *inheritanceScope) {
	t.Helper()
	expanded, diagnostics := expandInheritanceWithOrigins(composed.root, composed.origins, defaultProjectionLimits())
	if len(diagnostics) != 0 {
		t.Fatal(diagnostics)
	}
	baseline := &document.Node{Kind: document.Mapping}
	presence := make(map[string]inputPresence)
	collectPresence(expanded.root, Path{}, presence)
	decoded := decodedConfiguration{
		baseline: baseline, final: expanded.root, presence: presence, origins: expanded.origins,
	}
	metadata := metadataFromDecoded(decoded)
	applyInheritanceMetadata(&metadata, composed.root, composed.origins, composed.overlays, expanded)
	finalizeMetadataPaths(&metadata, expanded.root, composed.applications, baseline, composed.root)
	return &Inspection{
		metadata: metadata, baseline: baseline, input: expanded.root,
		inputOrigins: expanded.origins, final: expanded.root,
		applications: composed.applications, inheritance: expanded.operations,
	}, expanded
}

func TestInheritanceHistoryFollowsFinalParentAfterSourceOverlay(t *testing.T) {
	base, diagnostics := composeDocuments(parseCompositionDocument(t, "source-1", "parent: {value: original}\nchild: {extends: parent}\n"))
	if len(diagnostics) != 0 {
		t.Fatal(diagnostics)
	}
	assembly := newAssemblyAccumulator(base)
	if diagnostics := assembly.applyOverlay(parseCompositionDocument(t, "source-2", "parent: {value: latest}\n"), nil, nil, LayerOverlay); len(diagnostics) != 0 {
		t.Fatal(diagnostics)
	}
	inspection, _ := inheritanceInspectionFromComposition(t, assembly.current)
	path := Keys("child", "value")
	explanation, found := inspection.Explain(path)
	if !found || explanation.Effective.YAML != "latest\n" ||
		len(explanation.History) == 0 || explanation.History[len(explanation.History)-1].Origin.Locations[0].SourceID != "source-2" {
		t.Fatalf("overlaid parent contribution = %#v, %v", explanation, found)
	}
	parentHistory := inspection.Metadata().History(Keys("parent", "value"))
	if len(parentHistory) < 2 || parentHistory[0].Origin.Layer != LayerBase ||
		parentHistory[len(parentHistory)-1].Origin.Layer != LayerOverlay {
		t.Fatalf("parent source history = %#v", parentHistory)
	}
}

func TestInheritanceHistoryPreservesCancellationAndSupersededDirective(t *testing.T) {
	base, diagnostics := composeDocuments(parseCompositionDocument(t, "source-1", "parent: {value: one}\nchild: {extends: missing, value: own}\n"))
	if len(diagnostics) != 0 {
		t.Fatal(diagnostics)
	}
	assembly := newAssemblyAccumulator(base)
	if diagnostics := assembly.applyOverlay(parseCompositionDocument(t, "source-2", "child: {extends: null}\n"), nil, nil, LayerOverlay); len(diagnostics) != 0 {
		t.Fatal(diagnostics)
	}
	inspection, _ := inheritanceInspectionFromComposition(t, assembly.current)
	control := Keys("child", inheritanceKey)
	history := inspection.Metadata().History(control)
	if len(history) < 3 || history[0].Origin.Locations[0].SourceID != "source-1" ||
		history[1].Origin.Locations[0].SourceID != "source-2" ||
		history[len(history)-1].Origin.Operation != ChangeInheritance {
		t.Fatalf("superseded and cancelled directive history = %#v", history)
	}
	explanation, found := inspection.Explain(control)
	if !found || explanation.Effective.Present || len(explanation.History) < 3 ||
		explanation.History[len(explanation.History)-1].After.Present {
		t.Fatalf("cancelled directive explanation = %#v, %v", explanation, found)
	}
	value, found := inspection.Explain(Keys("child", "value"))
	if !found || value.Effective.YAML != "own\n" {
		t.Fatalf("cancelled relationship changed own value = %#v, %v", value, found)
	}
}

func TestInheritanceHistoryProjectsNestedDestinationValues(t *testing.T) {
	inspection, _ := inheritanceInspectionForTest(t, parseCompositionDocument(t, "source-1", `base:
  settings:
    primary: {value: old}
    secondary: {extends: primary}
custom:
  extends: base
  settings:
    primary: {value: new}
`))
	path := Keys("custom", "settings", "secondary", "value")
	history := inspection.Metadata().History(path)
	structural := 0
	for _, change := range history {
		if change.Origin.Operation == ChangeInheritance {
			structural++
		}
	}
	if structural == 0 {
		t.Fatalf("nested destination history = %#v", history)
	}
	explanation, found := inspection.Explain(path)
	if !found || explanation.Effective.YAML != "new\n" ||
		len(explanation.Origin.Inheritance) == 0 ||
		explanation.Origin.Inheritance[len(explanation.Origin.Inheritance)-1].To.String() != path.String() {
		t.Fatalf("nested destination explanation = %#v, %v", explanation, found)
	}
	for _, change := range explanation.History {
		if change.Origin.Operation == ChangeDecoding {
			t.Fatalf("nested inheritance was attributed to decoding: %#v", explanation.History)
		}
	}
}

func TestInheritanceHistoryShowsParentAndEqualChildContribution(t *testing.T) {
	inspection, _ := inheritanceInspectionForTest(t,
		parseCompositionDocument(t, "source-1", "parent: {value: same}\n"),
		parseCompositionDocument(t, "source-2", "child: {extends: parent, value: same}\n"))
	path := Keys("child", "value")
	history := inspection.Metadata().History(path)
	var structural []Change
	for _, change := range history {
		if change.Origin.Operation == ChangeInheritance {
			structural = append(structural, change)
		}
	}
	if len(structural) != 2 || structural[0].Origin.Locations[0].SourceID != "source-1" ||
		structural[1].Origin.Locations[0].SourceID != "source-2" ||
		len(structural[0].Dependencies) != 2 || structural[0].Dependencies[0].String() != "/parent" ||
		len(structural[0].Origin.Inheritance) != 1 {
		t.Fatalf("equal-valued structural history = %#v", history)
	}
	explanation, found := inspection.Explain(path)
	if !found || explanation.Effective.YAML != "same\n" {
		t.Fatalf("explanation = %#v, %v", explanation, found)
	}
	var equalEvents int
	for _, change := range explanation.History {
		if change.Origin.Operation == ChangeDecoding {
			t.Fatalf("inheritance was attributed to decoding: %#v", explanation.History)
		}
		if change.Origin.Operation == ChangeInheritance && change.Before.YAML == change.After.YAML {
			equalEvents++
		}
	}
	if equalEvents != 2 {
		t.Fatalf("equal parent and child operations = %#v", explanation.History)
	}
	parentHistory := inspection.Metadata().History(Keys("parent", "value"))
	for _, change := range parentHistory {
		if change.Origin.Operation == ChangeInheritance {
			t.Fatalf("source definition acquired a destination operation: %#v", parentHistory)
		}
	}
}

func TestInheritanceHistoryRetainsControlsAndDisplacedPaths(t *testing.T) {
	inspection, _ := inheritanceInspectionForTest(t,
		parseCompositionDocument(t, "source-1", "parent: {branch: {detail: inherited}}\n"),
		parseCompositionDocument(t, "source-2", "child: {extends: parent, branch: replaced}\n"))
	control := Keys("child", inheritanceKey)
	controlHistory := inspection.Metadata().History(control)
	if len(controlHistory) < 2 || controlHistory[len(controlHistory)-1].Origin.Operation != ChangeInheritance {
		t.Fatalf("control history = %#v", controlHistory)
	}
	controlExplanation, found := inspection.Explain(control)
	if !found || controlExplanation.Effective.Present ||
		controlExplanation.History[len(controlExplanation.History)-1].After.Present {
		t.Fatalf("consumed control = %#v, %v", controlExplanation, found)
	}
	path := Keys("child", "branch", "detail")
	if _, found := inspection.Metadata().Lookup(path); found {
		t.Fatal("displaced descendant remained effective")
	}
	listed := false
	for _, historical := range inspection.Metadata().HistoricalPaths() {
		if historical.String() == path.String() {
			listed = true
		}
	}
	if !listed {
		t.Fatal("displaced inherited descendant was not enumerable")
	}
	history := inspection.Metadata().History(path)
	if len(history) < 2 || history[len(history)-1].Origin.Operation != ChangeInheritance {
		t.Fatalf("displaced descendant history = %#v", history)
	}
	explanation, found := inspection.Explain(path)
	if !found || explanation.Effective.Present {
		t.Fatalf("displaced descendant explanation = %#v, %v", explanation, found)
	}
	var sawInherited, sawRemoval bool
	for _, change := range explanation.History {
		if change.Origin.Operation != ChangeInheritance {
			continue
		}
		sawInherited = sawInherited || change.After.Present
		sawRemoval = sawRemoval || (change.Before.Present && !change.After.Present)
	}
	if !sawInherited || !sawRemoval {
		t.Fatalf("displaced value sequence = %#v", explanation.History)
	}
	var rendered bytes.Buffer
	if err := inspection.WriteExplanation(&rendered, path); err != nil ||
		!strings.Contains(rendered.String(), "structural inheritance") {
		t.Fatalf("rendered structural explanation = %q, %v", rendered.String(), err)
	}
}

func TestInheritanceHistoryPrecedesApplicationResolution(t *testing.T) {
	inspection, _ := inheritanceInspectionForTest(t,
		parseCompositionDocument(t, "source-1", "parent: {value: original}\nchild: {extends: parent}\n"))
	path := Keys("child", "value")
	replacement := &document.Node{Kind: document.String, Text: "derived"}
	snapshot := resolutionSnapshot{
		change: Change{Path: path, Origin: Origin{Layer: LayerResolution, Operation: ChangeNormalization}},
		after:  replacement,
	}
	final := document.Clone(inspection.final)
	replaceHistoryPath(&final, path, replacement)
	inspection.final = final
	inspection.resolution = []resolutionSnapshot{snapshot}
	inspection.metadata.history[path.String()] = append(inspection.metadata.history[path.String()], snapshot.change)
	inspection.metadata.fields[path.String()] = FieldInfo{Explicit: true, Origin: snapshot.change.Origin}
	history := inspection.Metadata().History(path)
	if len(history) < 2 || history[len(history)-2].Origin.Operation != ChangeInheritance ||
		history[len(history)-1].Origin.Operation != ChangeNormalization {
		t.Fatalf("resolution order = %#v", history)
	}
	explanation, found := inspection.Explain(path)
	if !found || explanation.Effective.YAML != "derived\n" ||
		explanation.History[len(explanation.History)-1].Origin.Operation != ChangeNormalization {
		t.Fatalf("resolved explanation = %#v, %v", explanation, found)
	}
}

func TestHistoryNodeBudgetCountsSharedInheritanceEvidenceOnce(t *testing.T) {
	shared := &document.Node{Kind: document.String, Text: "shared"}
	extra := &document.Node{Kind: document.String, Text: "extra"}
	expansion := &inheritanceScope{
		root:         shared,
		operations:   []inheritanceOperation{{parent: shared, effective: shared}},
		replacements: []inheritanceReplacement{{before: shared, after: extra}},
	}
	if !historyNodesWithin(2, nil, nil, nil, nil, nil, expansion) ||
		historyNodesWithin(1, nil, nil, nil, nil, nil, expansion) {
		t.Fatal("shared evidence node accounting is incorrect")
	}
}

func TestInheritanceExpansionEnforcesRetainedHistoryBudget(t *testing.T) {
	input := parseCompositionDocument(t, "source-1", "parent: {value: original}\nchild: {extends: parent, value: replacement}\n")
	if _, diagnostics := expandInheritanceWithBudgets(input, nil, defaultProjectionLimits(), 2); len(diagnostics) != 1 || diagnostics[0].Code != CodeExplainLimitExceeded {
		t.Fatalf("retained history limit = %#v", diagnostics)
	}
	if _, diagnostics := expandInheritanceWithBudgets(input, nil, defaultProjectionLimits(), 100); len(diagnostics) != 0 {
		t.Fatalf("sufficient retained history budget = %#v", diagnostics)
	}
}