package configkit

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

func metadataFromDecoded(decoded decodedConfiguration) Metadata {
	metadata := Metadata{
		fields:  make(map[string]FieldInfo),
		history: make(map[string][]Change),
	}
	baseline := make(map[string]*document.Node)
	indexDocument(decoded.baseline, Path{}, baseline)
	for pointer := range baseline {
		path, err := ParsePath(pointer)
		if err != nil {
			continue
		}
		metadata.history[pointer] = append(metadata.history[pointer], Change{
			Path: path, Origin: Origin{Layer: LayerDefault},
		})
	}
	for pointer := range decoded.presence {
		path, err := ParsePath(pointer)
		if err != nil {
			continue
		}
		origin := cloneOrigin(decoded.origins[pointer])
		change := Change{Path: path, Origin: origin}
		if _, ok := baseline[pointer]; ok {
			change.Previous = []Origin{{Layer: LayerDefault}}
		}
		metadata.history[pointer] = append(metadata.history[pointer], change)
	}
	collectFieldInfo(decoded.final, Path{}, decoded, metadata.fields)
	return metadata
}

func collectFieldInfo(node *document.Node, path Path, decoded decodedConfiguration, fields map[string]FieldInfo) {
	pointer := path.String()
	_, explicit := decoded.presence[pointer]
	fields[pointer] = FieldInfo{
		Explicit: explicit,
		Null:     node.Kind == document.Null,
		Origin:   cloneOrigin(decoded.origins[pointer]),
	}
	switch node.Kind {
	case document.Mapping:
		for _, entry := range node.Mapping {
			collectFieldInfo(entry.Value, path.Key(entry.Key), decoded, fields)
		}
	case document.Sequence:
		for index, child := range node.Sequence {
			collectFieldInfo(child, path.Index(index), decoded, fields)
		}
	}
}

func indexDocument(node *document.Node, path Path, index map[string]*document.Node) {
	if node == nil {
		return
	}
	index[path.String()] = node
	switch node.Kind {
	case document.Mapping:
		for _, entry := range node.Mapping {
			indexDocument(entry.Value, path.Key(entry.Key), index)
		}
	case document.Sequence:
		for position, child := range node.Sequence {
			indexDocument(child, path.Index(position), index)
		}
	}
}

func cloneMetadata(metadata Metadata) Metadata {
	if metadata.fields == nil && metadata.history == nil {
		return Metadata{}
	}
	cloned := Metadata{
		fields:  make(map[string]FieldInfo, len(metadata.fields)),
		history: make(map[string][]Change, len(metadata.history)),
	}
	for path, info := range metadata.fields {
		cloned.fields[path] = cloneFieldInfo(info)
	}
	for path, changes := range metadata.history {
		clonedChanges := make([]Change, len(changes))
		for index, change := range changes {
			clonedChanges[index] = cloneChange(change)
		}
		cloned.history[path] = clonedChanges
	}
	return cloned
}

func applyResolutionMetadata(metadata *Metadata, resolved resolutionResult) {
	for _, snapshot := range resolved.snapshots {
		pointer := snapshot.change.Path.String()
		change := cloneChange(snapshot.change)
		if info, ok := metadata.fields[pointer]; ok {
			change.Previous = []Origin{cloneOrigin(info.Origin)}
			info.Origin = cloneOrigin(change.Origin)
			metadata.fields[pointer] = info
		}
		metadata.history[pointer] = append(metadata.history[pointer], change)
	}
	for _, delta := range resolved.deltas {
		record := coveringResolutionSnapshot(resolved.snapshots, delta.path)
		if record == nil {
			continue
		}
		for pointer, info := range metadata.fields {
			path, err := ParsePath(pointer)
			if err != nil || !pathContains(delta.path, path) {
				continue
			}
			info.Origin = cloneOrigin(record.change.Origin)
			metadata.fields[pointer] = info
		}
	}
	refreshResolutionFields(metadata.fields, resolved.final, resolved.snapshots)
}

func coveringResolutionSnapshot(snapshots []resolutionSnapshot, path Path) *resolutionSnapshot {
	var covering *resolutionSnapshot
	for index := range snapshots {
		snapshot := &snapshots[index]
		if pathContains(snapshot.change.Path, path) && (covering == nil || len(snapshot.change.Path.segments) > len(covering.change.Path.segments)) {
			covering = snapshot
		}
	}
	return covering
}

func refreshResolutionFields(fields map[string]FieldInfo, final *document.Node, snapshots []resolutionSnapshot) {
	finalPaths := make(map[string]*document.Node)
	indexDocument(final, Path{}, finalPaths)
	for pointer := range fields {
		if _, ok := finalPaths[pointer]; !ok {
			delete(fields, pointer)
		}
	}
	for pointer, node := range finalPaths {
		if info, ok := fields[pointer]; ok {
			info.Null = node.Kind == document.Null
			fields[pointer] = info
			continue
		}
		origin := Origin{Layer: LayerResolution}
		if path, err := ParsePath(pointer); err == nil {
			if covering := coveringResolutionSnapshot(snapshots, path); covering != nil {
				origin = cloneOrigin(covering.change.Origin)
			}
		}
		fields[pointer] = FieldInfo{Null: node.Kind == document.Null, Origin: origin}
	}
}