package engine

import (
	"reflect"
	"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)
	}

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