package pipeline

import (
	"context"
	"fmt"
	"reflect"
	"sort"
	"strings"

	"gitea.maximumdirect.net/eric/notarius/internal/framework/contracts"
)

type ValidatorSpec struct {
	Key            string                   `json:"key"`
	ExecutionClass contracts.ExecutionClass `json:"execution_class"`
}

type SerializedValidatorSpec struct {
	ValidatorSpec
	SupportsChunks    bool `json:"supports_chunks,omitempty"`
	SupportsArtifacts bool `json:"supports_artifacts,omitempty"`
}

type ValidatorTarget string

const (
	ValidatorTargetChunk      ValidatorTarget = "chunk"
	ValidatorTargetSerialized ValidatorTarget = "serialized"
	ValidatorTargetTyped      ValidatorTarget = "typed"
)

type ValidatorRegistry struct {
	typedEntries      map[artifactVariantKey]typedValidatorEntry
	chunkEntries      map[string]chunkValidatorEntry
	serializedEntries map[string]serializedValidatorEntry
}

type typedValidatorEntry struct {
	spec            ValidatorSpec
	kind            contracts.ArtifactKind
	valueType       reflect.Type
	validateOptions OptionValidator
	builder         func(BuildRequest) (any, error)
	validate        typedValidateOperation
}

type chunkValidatorEntry struct {
	spec            ValidatorSpec
	validateOptions OptionValidator
	builder         func(BuildRequest) (contracts.ChunkValidator, error)
}

type serializedValidatorEntry struct {
	spec            SerializedValidatorSpec
	validateOptions OptionValidator
	builder         func(BuildRequest) (contracts.SerializedValidator, error)
}

func NewValidatorRegistry() *ValidatorRegistry {
	return &ValidatorRegistry{
		typedEntries:      make(map[artifactVariantKey]typedValidatorEntry),
		chunkEntries:      make(map[string]chunkValidatorEntry),
		serializedEntries: make(map[string]serializedValidatorEntry),
	}
}

func RegisterTypedValidator[T any](registry *ValidatorRegistry, kind contracts.ArtifactKind, spec ValidatorSpec, constructor func() (contracts.TypedValidator[T], error)) error {
	if constructor == nil {
		return fmt.Errorf("validator constructor for %q must not be nil", strings.TrimSpace(spec.Key))
	}
	return RegisterTypedValidatorBuilder(registry, kind, spec, rejectUnconfiguredOptions, func(BuildRequest) (contracts.TypedValidator[T], error) {
		return constructor()
	})
}

func RegisterTypedValidatorBuilder[T any](registry *ValidatorRegistry, kind contracts.ArtifactKind, spec ValidatorSpec, validateOptions OptionValidator, builder func(BuildRequest) (contracts.TypedValidator[T], error)) error {
	if registry == nil {
		return fmt.Errorf("validator registry must not be nil")
	}
	normalizedSpec, err := normalizeValidatorSpec(spec)
	if err != nil {
		return err
	}
	kind = normalizeArtifactKind(kind)
	if kind == "" {
		return fmt.Errorf("typed validator %q artifact kind must not be empty", normalizedSpec.Key)
	}
	if validateOptions == nil {
		return fmt.Errorf("validator option validator for %q must not be nil", normalizedSpec.Key)
	}
	if builder == nil {
		return fmt.Errorf("validator builder for %q must not be nil", normalizedSpec.Key)
	}
	key := artifactVariantKey{module: normalizedSpec.Key, kind: kind}
	if _, ok := registry.typedEntries[key]; ok {
		return fmt.Errorf("validator %q variant for artifact kind %q is already registered", key.module, key.kind)
	}
	if registry.typedEntries == nil {
		registry.typedEntries = make(map[artifactVariantKey]typedValidatorEntry)
	}
	registry.typedEntries[key] = typedValidatorEntry{
		spec:            normalizedSpec,
		kind:            kind,
		valueType:       reflect.TypeFor[T](),
		validateOptions: validateOptions,
		builder: func(request BuildRequest) (any, error) {
			return builder(cloneBuildRequest(request))
		},
		validate: func(ctx context.Context, implementation any, target typedValidationTarget) (contracts.ValidationResult, error) {
			validator, ok := implementation.(contracts.TypedValidator[T])
			if !ok {
				return contracts.ValidationResult{}, fmt.Errorf("validator %q has incompatible implementation %T", normalizedSpec.Key, implementation)
			}
			value, err := exactTypedValue[T]("validate artifact value", target.value)
			if err != nil {
				return contracts.ValidationResult{}, err
			}
			return validator.Validate(ctx, contracts.TypedValidationRequest[T]{Stage: string(target.stage), LaneID: target.laneID, ModuleKey: target.moduleKey, Source: target.source, SourceID: target.sourceID, SourceInput: target.sourceInput, SessionID: target.sessionID, References: target.references, LLMProfile: target.llmProfile, Metadata: target.metadata, Chunk: target.chunk, Chunks: target.chunks, Ref: target.ref, Value: value})
		},
	}
	return nil
}

func RegisterChunkValidator(registry *ValidatorRegistry, spec ValidatorSpec, constructor func() (contracts.ChunkValidator, error)) error {
	if constructor == nil {
		return fmt.Errorf("validator constructor for %q must not be nil", strings.TrimSpace(spec.Key))
	}
	return RegisterChunkValidatorBuilder(registry, spec, rejectUnconfiguredOptions, func(BuildRequest) (contracts.ChunkValidator, error) {
		return constructor()
	})
}

func RegisterChunkValidatorBuilder(registry *ValidatorRegistry, spec ValidatorSpec, validateOptions OptionValidator, builder func(BuildRequest) (contracts.ChunkValidator, error)) error {
	if registry == nil {
		return fmt.Errorf("validator registry must not be nil")
	}
	normalizedSpec, err := normalizeValidatorSpec(spec)
	if err != nil {
		return err
	}
	if validateOptions == nil {
		return fmt.Errorf("validator option validator for %q must not be nil", normalizedSpec.Key)
	}
	if builder == nil {
		return fmt.Errorf("validator builder for %q must not be nil", normalizedSpec.Key)
	}
	if _, ok := registry.chunkEntries[normalizedSpec.Key]; ok {
		return fmt.Errorf("chunk validator %q is already registered", normalizedSpec.Key)
	}
	if registry.chunkEntries == nil {
		registry.chunkEntries = make(map[string]chunkValidatorEntry)
	}
	registry.chunkEntries[normalizedSpec.Key] = chunkValidatorEntry{spec: normalizedSpec, validateOptions: validateOptions, builder: builder}
	return nil
}

func RegisterSerializedValidator(registry *ValidatorRegistry, spec SerializedValidatorSpec, constructor func() (contracts.SerializedValidator, error)) error {
	if constructor == nil {
		return fmt.Errorf("validator constructor for %q must not be nil", strings.TrimSpace(spec.Key))
	}
	return RegisterSerializedValidatorBuilder(registry, spec, rejectUnconfiguredOptions, func(BuildRequest) (contracts.SerializedValidator, error) {
		return constructor()
	})
}

func RegisterSerializedValidatorBuilder(registry *ValidatorRegistry, spec SerializedValidatorSpec, validateOptions OptionValidator, builder func(BuildRequest) (contracts.SerializedValidator, error)) error {
	if registry == nil {
		return fmt.Errorf("validator registry must not be nil")
	}
	normalizedValidatorSpec, err := normalizeValidatorSpec(spec.ValidatorSpec)
	if err != nil {
		return err
	}
	spec.ValidatorSpec = normalizedValidatorSpec
	if !spec.SupportsChunks && !spec.SupportsArtifacts {
		return fmt.Errorf("serialized validator %q must support chunks, artifacts, or both", spec.Key)
	}
	if validateOptions == nil {
		return fmt.Errorf("validator option validator for %q must not be nil", spec.Key)
	}
	if builder == nil {
		return fmt.Errorf("validator builder for %q must not be nil", spec.Key)
	}
	if _, ok := registry.serializedEntries[spec.Key]; ok {
		return fmt.Errorf("serialized validator %q is already registered", spec.Key)
	}
	if registry.serializedEntries == nil {
		registry.serializedEntries = make(map[string]serializedValidatorEntry)
	}
	registry.serializedEntries[spec.Key] = serializedValidatorEntry{spec: spec, validateOptions: validateOptions, builder: builder}
	return nil
}

func (r *ValidatorRegistry) validateOptions(resolved ResolvedValidator) error {
	if r == nil {
		return fmt.Errorf("validator registry must not be nil")
	}
	key := strings.TrimSpace(resolved.Binding.Module)
	var validator OptionValidator
	switch resolved.Target {
	case ValidatorTargetTyped:
		entry, ok := r.typedEntry(key, resolved.ArtifactKind)
		if ok {
			validator = entry.validateOptions
		}
	case ValidatorTargetChunk:
		entry, ok := r.chunkEntry(key)
		if ok {
			validator = entry.validateOptions
		}
	case ValidatorTargetSerialized:
		entry, ok := r.serializedEntry(key)
		if ok {
			validator = entry.validateOptions
		}
	}
	if validator == nil {
		return fmt.Errorf("validator %q construction entry is not registered", key)
	}
	return validateRegisteredOptions(validator, resolved.Binding.Options)
}

func (r *ValidatorRegistry) Spec(key string) (ValidatorSpec, bool) {
	if r == nil {
		return ValidatorSpec{}, false
	}
	normalized := strings.TrimSpace(key)
	if entry, found := r.chunkEntries[normalized]; found {
		return entry.spec, true
	}
	if entry, found := r.serializedEntries[normalized]; found {
		return entry.spec.ValidatorSpec, true
	}
	if kinds := r.registeredTypedKinds(normalized); len(kinds) > 0 {
		entry, found := r.typedEntry(normalized, kinds[0])
		return entry.spec, found
	}
	return ValidatorSpec{}, false
}

func (r *ValidatorRegistry) typedEntry(key string, kind contracts.ArtifactKind) (typedValidatorEntry, bool) {
	if r == nil {
		return typedValidatorEntry{}, false
	}
	entry, ok := r.typedEntries[artifactVariantKey{module: strings.TrimSpace(key), kind: normalizeArtifactKind(kind)}]
	return entry, ok
}

func (r *ValidatorRegistry) chunkEntry(key string) (chunkValidatorEntry, bool) {
	if r == nil {
		return chunkValidatorEntry{}, false
	}
	entry, ok := r.chunkEntries[strings.TrimSpace(key)]
	return entry, ok
}

func (r *ValidatorRegistry) serializedEntry(key string) (serializedValidatorEntry, bool) {
	if r == nil {
		return serializedValidatorEntry{}, false
	}
	entry, ok := r.serializedEntries[strings.TrimSpace(key)]
	return entry, ok
}

func (r *ValidatorRegistry) registeredTypedKinds(key string) []contracts.ArtifactKind {
	if r == nil {
		return nil
	}
	module := strings.TrimSpace(key)
	kinds := make([]contracts.ArtifactKind, 0)
	for variant := range r.typedEntries {
		if variant.module == module {
			kinds = append(kinds, variant.kind)
		}
	}
	sortArtifactKinds(kinds)
	return kinds
}

func (r *ValidatorRegistry) RegisteredSpecs() []ValidatorSpec {
	if r == nil {
		return nil
	}
	keys := r.RegisteredKeys()
	specs := make([]ValidatorSpec, 0, len(keys))
	for _, key := range keys {
		if spec, ok := r.Spec(key); ok {
			specs = append(specs, spec)
		}
	}
	return specs
}

func (r *ValidatorRegistry) RegisteredKeys() []string {
	if r == nil {
		return nil
	}
	keys := make(map[string]struct{})
	for key := range r.typedEntries {
		keys[key.module] = struct{}{}
	}
	for key := range r.chunkEntries {
		keys[key] = struct{}{}
	}
	for key := range r.serializedEntries {
		keys[key] = struct{}{}
	}
	return sortedRegistryKeys(keys)
}

func normalizeValidatorSpec(spec ValidatorSpec) (ValidatorSpec, error) {
	normalized := ValidatorSpec{Key: strings.TrimSpace(spec.Key), ExecutionClass: spec.ExecutionClass}
	if normalized.Key == "" {
		return ValidatorSpec{}, fmt.Errorf("validator key must not be empty")
	}
	switch normalized.ExecutionClass {
	case contracts.ExecutionClassDeterministic, contracts.ExecutionClassLLMBacked:
	default:
		return ValidatorSpec{}, fmt.Errorf("validator %q execution class %q is not supported", normalized.Key, normalized.ExecutionClass)
	}
	return normalized, nil
}

func sortValidatorSpecs(specs []ValidatorSpec) {
	sort.Slice(specs, func(i, j int) bool { return specs[i].Key < specs[j].Key })
}