package engine

import (
	"reflect"

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

// resolvedLoad carries typed phase outputs needed for validation and publication;
// it owns no source access, options, or long-lived schema state.
type resolvedLoad[T any] struct {
	configuration   T
	metadata        Metadata
	final           *document.Node
	referenceInput  *document.Node
	versionEvidence []*sourceVersionEvidence
	contexts        map[string]ResourceContext
}

func decodeLoadInput[T any](schema *schemaDescriptor, definition Definition[T], input assembledInput) (decodedConfiguration, []Diagnostic) {
	defaults := reflect.Zero(reflect.TypeFor[T]())
	if definition.Defaults != nil {
		defaults = reflect.ValueOf(definition.Defaults())
	}
	context := decodeContext{}
	if definition.Version != nil {
		context.versionPath = &definition.Version.Path
	}
	decoded, decodeIssues := decodeConfigurationWithContext(schema, defaults, input.document, context)
	if len(decodeIssues) != 0 {
		diagnostics := make([]Diagnostic, len(decodeIssues))
		for i, issue := range decodeIssues {
			diagnostics[i] = diagnosticFromDecodeIssue(issue)
		}
		return decodedConfiguration{}, diagnostics
	}
	if input.inheritance != nil {
		applyCompositionOrigins(&decoded, input.inheritance.origins)
	} else if input.composition != nil {
		applyCompositionOrigins(&decoded, input.composition.origins)
	}

	return decoded, nil
}

func resolveLoadInput[T any](schema *schemaDescriptor, definition Definition[T], input assembledInput, prepared postDecodeOverrideContext) (resolvedLoad[T], []Diagnostic) {
	var diagnostics []Diagnostic
	decoded := prepared.decoded
	configuration := decoded.value.Interface().(T)
	metadata := prepared.metadata
	builder := metadata.historyBuilder
	final := decoded.final
	referenceInput := prepared.referenceInput
	var resolutionSnapshots []resolutionSnapshot
	refreshReferenceInput := false
	if definition.Resolve != nil {
		resolved := runResolution(&configuration, definition.Resolve, schema, decoded, referenceInput, prepared.resolution)
		diagnostics = append(diagnostics, resolved.diagnostics...)
		if hasErrors(resolved.diagnostics) {
			return resolvedLoad[T]{}, diagnostics
		}
		final = resolved.final
		resolutionSnapshots = resolved.snapshots
		if builder != nil && len(resolutionSnapshots) != 0 {
			builder.observeResolutionEvidence(resolutionSnapshots)
		}
		applyResolutionMetadata(&metadata, resolved, prepared.resolution)
		finalizeEffectiveMetadataPaths(&metadata, final)
		refreshReferenceInput = true
	}
	if builder != nil {
		builder.model.final = final
	}
	if refreshReferenceInput {
		referenceInput = documentWithMetadataLocations(final, metadata, input.document)
	}
	var versionEvidence []*sourceVersionEvidence
	if input.versionState != nil {
		versionEvidence = append(versionEvidence, input.versionState.evidence...)
	}
	return resolvedLoad[T]{
		configuration: configuration, metadata: metadata, final: final, referenceInput: referenceInput,
		versionEvidence: versionEvidence, contexts: input.contexts,
	}, diagnostics
}

func detachLoadConfiguration[T any](schema *schemaDescriptor, configuration T, mode secretCloneMode) (T, *Diagnostic) {
	detached, issue := cloneConfigurationWithMode(schema, reflect.ValueOf(configuration), defaultProjectionLimits(), mode)
	if issue != nil {
		diagnostic := diagnosticFromDecodeIssue(decodeIssueFromProjection(issue))
		var zero T
		return zero, &diagnostic
	}
	return detached.Interface().(T), nil
}

func prepareInspectionHistory[T any](resolved resolvedLoad[T], counter *retainedNodeCounter) (*Inspection, bool) {
	metadata := resolved.metadata
	freezeMetadataHistory(&metadata, resolved.final)
	model := metadata.historyModel
	inspection := &Inspection{
		metadata: metadata,
		history:  model,
		final:    resolved.final,
	}
	if !addInspectionHistory(counter, inspection) {
		return nil, false
	}
	return inspection, true
}

func publishLoadResult[T any](schema *schemaDescriptor, definition Definition[T], resolved resolvedLoad[T], inspection *Inspection, references map[string]string, accumulator *diagnosticAccumulator) (*Loaded[T], error) {
	// A read-only validator can replace a value with an equal borrowed object.
	// Detach without re-reading the environment or discarding validated state.
	configuration, issue := detachLoadConfiguration(schema, resolved.configuration, cloneValidatedSecrets)
	if issue != nil {
		accumulator.add(*issue)
		return nil, accumulator.loadError()
	}
	metadata := inspection.metadata
	secrets := classifySecretPathsWithEvidence(schema, definition.Secret, metadata, resolved.versionEvidence)
	sources := sourceInfosWithVersionEvidence(accumulator.sources, resolved.versionEvidence, secrets, false)
	inspection.metadata = metadata
	inspection.sources = sources
	inspection.contexts = cloneResourceContexts(resolved.contexts)
	inspection.diagnostics = canonicalDiagnostics(accumulator.diagnostics)
	inspection.secrets = secrets
	inspection.secretReferences = cloneSecretReferences(references)
	return &Loaded[T]{Config: configuration, Inspection: inspection}, nil
}

func diagnosticFromSchemaIssue(issue *schemaIssue) Diagnostic {
	return Diagnostic{Code: issue.code, Severity: SeverityError, Path: issue.path.clone(), Message: issue.message}
}

func diagnosticFromDecodeIssue(issue decodeIssue) Diagnostic {
	return Diagnostic{
		Code: issue.code, Severity: SeverityError, Path: issue.path.clone(), Message: issue.message,
		Primary: documentLocationPointer(issue.location),
	}
}