package engine

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

func applyOverrides(base *composedDocument, sources []SourceInfo, overrides []Override, rule *VersionRule, limits importLimits) (*composedDocument, []SourceInfo, []Diagnostic) {
	if len(overrides) == 0 {
		return base, cloneSourceInfos(sources), nil
	}
	assembly := newAssemblyAccumulator(cloneComposedDocument(base))
	allSources, diagnostics := assembly.applyOverrides(sources, overrides, rule, limits)
	if len(diagnostics) != 0 {
		return nil, allSources, diagnostics
	}
	return assembly.current, allSources, nil
}

func (a *assemblyAccumulator) applyOverrides(sources []SourceInfo, overrides []Override, rule *VersionRule, limits importLimits) ([]SourceInfo, []Diagnostic) {
	if len(overrides) == 0 {
		return cloneSourceInfos(sources), nil
	}
	prepared, allSources, diagnostics := prepareOverrides(a.current, sources, overrides, rule, limits)
	if len(diagnostics) != 0 {
		return allSources, diagnostics
	}
	for _, override := range prepared {
		applyPreparedOverride(a.current, override, &a.index)
		a.current.inputBytes += override.bytes
		a.current.inputNodes += override.nodes
	}
	return allSources, nil
}

func applyPreparedOverride(result *composedDocument, override preparedOverride, index *mappingIndex) {
	location := document.Location{SourceID: override.source.ID}
	mergeOverlayOrigin(result.origins, Path{}, location, LayerCLI)
	current := result.root
	currentPath := Path{}
	for segmentIndex, segment := range override.path.segments {
		path := currentPath.Key(segment.key)
		position := index.find(current, segment.key)
		if segmentIndex < len(override.path.segments)-1 {
			if position < 0 {
				child := &document.Node{Kind: document.Mapping, Location: location, Mapping: []document.Entry{}}
				index.append(current, document.Entry{Key: segment.key, KeyLocation: location, ValueLocation: location, Value: child})
				collectOverlayOrigins(result.origins, child, path, LayerCLI)
				current = child
			} else {
				current = current.Mapping[position].Value
				mergeOverlayOrigin(result.origins, path, location, LayerCLI)
			}
			currentPath = path
			continue
		}

		previous := cloneOrigin(result.origins[path.String()])
		var displaced []displacedDefinition
		if position < 0 {
			incoming := document.Clone(override.value)
			index.append(current, document.Entry{Key: segment.key, KeyLocation: location, ValueLocation: location, Value: incoming})
			collectOverlayOrigins(result.origins, incoming, path, LayerCLI)
		} else {
			existing := current.Mapping[position].Value
			displaced = affectedOverrideOrigins(existing, override.value, result.origins, path, index)
			if existing.Kind == document.Mapping && override.value.Kind == document.Mapping {
				mergeOverlayOrigin(result.origins, path, location, LayerCLI)
				mergeOverlayMappings(result, existing, override.value, path, LayerCLI, false, nil, index)
			} else {
				deleteOriginSubtree(result.origins, path, existing)
				current.Mapping[position] = document.Entry{Key: segment.key, KeyLocation: location, ValueLocation: location, Value: document.Clone(override.value)}
				collectOverlayOrigins(result.origins, current.Mapping[position].Value, path, LayerCLI)
			}
		}
		result.overlays = append(result.overlays, overlayRecord{change: Change{
			Path: path.clone(), Origin: overlayOrigin(LayerCLI, location), Previous: previousOrigins(previous),
		}, displaced: displaced})
		result.applications = append(result.applications, historyApplication{
			layer: LayerCLI, path: path.clone(), value: override.value,
			origin: overlayOrigin(LayerCLI, location),
		})
	}
}

func affectedOverrideOrigins(existing, incoming *document.Node, origins map[string]Origin, path Path, index *mappingIndex) []displacedDefinition {
	var displaced []displacedDefinition
	collectAffectedOverrideOrigins(&displaced, existing, incoming, origins, path, index)
	return sortDisplacedDefinitions(displaced)
}

func collectAffectedOverrideOrigins(displaced *[]displacedDefinition, existing, incoming *document.Node, origins map[string]Origin, path Path, index *mappingIndex) {
	if existing.Kind != document.Mapping || incoming.Kind != document.Mapping {
		collectDisplacedOrigins(displaced, existing, origins, path, Origin{})
		return
	}
	*displaced = append(*displaced, displacedDefinition{path: path.clone(), origin: cloneOrigin(origins[path.String()])})
	for _, entry := range incoming.Mapping {
		position := index.find(existing, entry.Key)
		if position < 0 {
			continue
		}
		childPath := path.Key(entry.Key)
		childExisting := existing.Mapping[position].Value
		if childExisting.Kind == document.Mapping && entry.Value.Kind == document.Mapping {
			collectAffectedOverrideOrigins(displaced, childExisting, entry.Value, origins, childPath, index)
		} else {
			collectDisplacedOrigins(displaced, childExisting, origins, childPath, Origin{})
		}
	}
}