package engine

import (
	"slices"
	"sort"

	"go.maximumdirect.net/configkit/internal/document"
)

type historySelection struct {
	path           Path
	phase          historyPhase
	payload        historyPayloadRef
	reportedPath   Path
	role           historyRole
	before         bool
	after          bool
	attribution    historyAttribution
	hasAttribution bool
	previous       []Origin
}

type historySensitivityCandidate struct {
	path      Path
	sensitive bool
	classify  bool
}

func (model *historyModel) selectHistory(path Path) []historySelection {
	if model == nil || !path.valid() || !model.hasObservedShape(path) {
		return nil
	}

	candidateSet := make(map[int]struct{})
	for _, observationID := range model.observationsByPointer[path.String()] {
		candidateSet[observationID] = struct{}{}
	}
	// Producers register all affected before/after paths. Exact facts cover
	// ancestor replacements; descendants cover operations within an enclosing
	// query. Logical operations are still deduplicated by payload below.
	model.affectedPathIndex.visitDescendants(path.String(), func(observationID int) {
		candidateSet[observationID] = struct{}{}
	})
	candidates := make([]int, 0, len(candidateSet))
	for observationID := range candidateSet {
		candidates = append(candidates, observationID)
	}
	slices.Sort(candidates)

	selections := make([]historySelection, 0, len(candidates))
	selectionByPayload := make(map[historyPayloadRef]int)
	for _, observationID := range candidates {
		observation := model.observations[observationID]
		if observation.role == historyRoleInventory {
			continue
		}
		reportedPath := observation.reportedPath
		attributionRef := observation.attributionRef
		if observation.role == historyRoleContribution {
			if !historyObservationMatchesQuery(path, observation.path) {
				continue
			}
			application, found := model.applicationPayload(observation.payload)
			if !found {
				continue
			}
			if pathContains(observation.path, path) && len(observation.path.segments) < len(path.segments) {
				local, ok := historyApplicationLocalPath(application, path)
				if !ok {
					continue
				}
				if _, present := documentAtPathWithLookup(application.value, local, model.documentLookup); !present {
					continue
				}
			}
			if operationPath, relevant := applicationOperationPath(application, path, model.documentLookup); relevant {
				reportedPath = operationPath
			}
		} else if !historyObservationMatchesQuery(path, observation.path) {
			continue
		}
		selectionIndex, found := selectionByPayload[observation.payload]
		if !found {
			selectionIndex = len(selections)
			selectionByPayload[observation.payload] = selectionIndex
			selection := historySelection{
				path:         path.clone(),
				phase:        observation.phase,
				payload:      observation.payload,
				reportedPath: reportedPath.clone(),
				role:         observation.role,
			}
			if attribution, ok := model.resolveAttribution(attributionRef); ok {
				selection.attribution = attribution
				selection.hasAttribution = true
			}
			selections = append(selections, selection)
		}
		selection := &selections[selectionIndex]
		selection.before = selection.before || observation.beforePresent
		selection.after = selection.after || observation.afterPresent
	}
	if len(selections) == 0 {
		return nil
	}

	var previous *Origin
	for index := range selections {
		selection := &selections[index]
		if selection.hasAttribution && metadataHistoryRole(selection.role) {
			if previous != nil {
				selection.previous = []Origin{cloneOrigin(*previous)}
			}
			origin := cloneOrigin(selection.attribution.origin)
			previous = &origin
		}
	}
	return selections
}

func historyObservationMatchesQuery(query, observed Path) bool {
	if matchesPathShape(query, observed) {
		return true
	}
	return pathContains(query, observed) && pathShapePrefixMatches(query, observed)
}

func (model *historyModel) hasObservedShape(path Path) bool {
	if model == nil || !path.valid() {
		return false
	}
	for _, candidate := range model.shapesByPointer[path.String()] {
		if matchesPathShape(path, candidate) {
			return true
		}
	}
	return false
}

func (model *historyModel) concreteShapes(pointer string) []Path {
	if model == nil {
		return nil
	}
	shapes := model.shapesByPointer[pointer]
	cloned := make([]Path, len(shapes))
	for index, path := range shapes {
		cloned[index] = path.clone()
	}
	return cloned
}

func (model *historyModel) observedPaths() []Path {
	if model == nil {
		return nil
	}
	paths := make([]Path, len(model.shapeOrder))
	for index, path := range model.shapeOrder {
		paths[index] = path.clone()
	}
	return paths
}

func (model *historyModel) historicalPaths() []Path {
	if model == nil {
		return []Path{}
	}
	pointers := make([]string, 0, len(model.shapesByPointer))
	for pointer := range model.shapesByPointer {
		pointers = append(pointers, pointer)
	}
	sort.Strings(pointers)
	paths := make([]Path, 0, len(pointers))
	for _, pointer := range pointers {
		path, err := ParsePath(pointer)
		if err == nil {
			paths = append(paths, path)
		}
	}
	return paths
}

func (model *historyModel) latestHistoricalLocation(path Path) (Location, bool) {
	selections := model.selectHistory(path)
	for selectionIndex := len(selections) - 1; selectionIndex >= 0; selectionIndex-- {
		selection := selections[selectionIndex]
		if selection.hasAttribution {
			if location, found := latestOriginDocumentLocation(selection.attribution.origin); found {
				return Location{SourceID: location.SourceID, Line: location.Line, Column: location.Column}, true
			}
		}
		for previousIndex := len(selection.previous) - 1; previousIndex >= 0; previousIndex-- {
			if location, found := latestOriginDocumentLocation(selection.previous[previousIndex]); found {
				return Location{SourceID: location.SourceID, Line: location.Line, Column: location.Column}, true
			}
		}
	}
	return Location{}, false
}

func (model *historyModel) sensitivityCandidates(inherited []secretDependency) []historySensitivityCandidate {
	if model == nil {
		return nil
	}
	candidates := make([]historySensitivityCandidate, 0, len(model.observations))
	indices := make(map[string][]int)
	seenAttributions := make(map[historyAttributionRef]struct{})
	add := func(path Path, sensitive, classify bool) {
		if !path.valid() {
			return
		}
		pointer := path.String()
		for _, index := range indices[pointer] {
			if slices.Equal(candidates[index].path.segments, path.segments) {
				candidates[index].sensitive = candidates[index].sensitive || sensitive
				candidates[index].classify = candidates[index].classify || classify
				return
			}
		}
		index := len(candidates)
		candidates = append(candidates, historySensitivityCandidate{path: path.clone(), sensitive: sensitive, classify: classify})
		indices[pointer] = append(indices[pointer], index)
	}
	for _, observation := range model.observations {
		concreteCandidate := observation.role == historyRoleControl
		if observation.role == historyRoleContribution {
			if application, found := model.applicationPayload(observation.payload); found && len(application.sequences) != 0 {
				concreteCandidate = true
			}
		}
		add(observation.path, observation.sensitive, concreteCandidate)
		if parsed, err := ParsePath(observation.path.String()); err == nil {
			add(parsed, observation.sensitive, true)
		}
		if _, seen := seenAttributions[observation.attributionRef]; seen {
			continue
		}
		seenAttributions[observation.attributionRef] = struct{}{}
		if attribution, found := model.resolveAttribution(observation.attributionRef); found {
			for _, dependency := range attribution.dependencies {
				if dependency.valid() {
					add(dependency, false, true)
				}
			}
		}
	}
	for _, link := range inherited {
		add(link.target, false, true)
		add(link.dependency, false, true)
	}
	return candidates
}

// sensitivityDependencies returns the original attribution edges and the
// bidirectional links represented by inheritance payloads. It intentionally
// does not derive edges from the public metadata projection, which may omit
// evidence needed to keep historical values redacted.
func (model *historyModel) sensitivityDependencies() (dependencies, inherited []secretDependency) {
	if model == nil {
		return nil, nil
	}
	// Every affected subtree fact borrows its operation's attribution. Expand
	// each logical target/dependency list once, not once for every descendant.
	type dependencyAttribution struct {
		ref    historyAttributionRef
		target string
	}
	seen := make(map[dependencyAttribution]struct{})
	for _, observation := range model.observations {
		if observation.phase == historyPhaseInheritance || observation.attributionRef == noHistoryAttribution {
			continue
		}
		key := dependencyAttribution{ref: observation.attributionRef, target: observation.reportedPath.String()}
		if _, found := seen[key]; found {
			continue
		}
		seen[key] = struct{}{}
		attribution, found := model.resolveAttribution(observation.attributionRef)
		if !found {
			continue
		}
		for _, dependency := range attribution.dependencies {
			if observation.reportedPath.valid() && dependency.valid() {
				dependencies = append(dependencies, secretDependency{
					target: observation.reportedPath.clone(), dependency: dependency.clone(),
				})
			}
		}
	}
	for _, payload := range model.inheritancePayloads {
		for _, operation := range payload.operations {
			if operation.control != nil {
				control := operation.control.path
				for _, contributor := range operation.controlOrigin.contributors {
					if control.valid() && contributor.source.valid() {
						inherited = append(inherited, secretDependency{
							target: control.clone(), dependency: contributor.source.clone(),
						})
					}
				}
				continue
			}
			if operation.transfer == nil || operation.parent == nil {
				continue
			}
			transfer := operation.transfer
			walkDocument(operation.parent, transfer.to, func(destination Path, _ *document.Node) {
				relative, ok := relativeHistoryPath(transfer.to, destination)
				if !ok {
					return
				}
				source := appendInheritancePath(transfer.from, relative)
				if _, found := operation.parentOrigins[source.String()]; !found {
					return
				}
				inherited = append(inherited, secretDependency{
					target: destination.clone(), dependency: source,
				})
			})
		}
	}
	return dependencies, inherited
}

func (model *historyModel) resolveAttribution(ref historyAttributionRef) (historyAttribution, bool) {
	if model == nil || ref < 0 || int(ref) >= len(model.attributions) {
		return historyAttribution{}, false
	}
	attribution := model.attributions[ref]
	return historyAttribution{
		origin:       cloneOrigin(attribution.origin),
		reasons:      append([]string(nil), attribution.reasons...),
		dependencies: clonePaths(attribution.dependencies),
	}, true
}

func (model *historyModel) applicationPayload(ref historyPayloadRef) (historyApplication, bool) {
	if model == nil || ref.id < 0 {
		return historyApplication{}, false
	}
	var payloads []historySourcePayload
	switch ref.phase {
	case historyPhaseSources:
		payloads = model.sourcePayloads
	case historyPhaseCLI:
		payloads = model.cliPayloads
	default:
		return historyApplication{}, false
	}
	if ref.id >= len(payloads) || payloads[ref.id].kind != historySourceApplicationPayload {
		return historyApplication{}, false
	}
	return payloads[ref.id].application, true
}

func pathShapePrefixMatches(left, right Path) bool {
	length := min(len(left.segments), len(right.segments))
	leftPrefix := Path{segments: clonePathSegments(left.segments[:length], 0)}
	rightPrefix := Path{segments: clonePathSegments(right.segments[:length], 0)}
	return matchesPathShape(leftPrefix, rightPrefix)
}

func metadataHistoryRole(role historyRole) bool {
	switch role {
	case historyRoleDefinition, historyRoleCompositeDefinition, historyRoleOperation, historyRoleControl:
		return true
	default:
		return false
	}
}