package validjsonschema

import (
	"bytes"
	"context"
	"fmt"

	"github.com/santhosh-tekuri/jsonschema/v6"

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

const Key = "generic/valid_json_schema"
const ReasonCodeInvalidJSON = "invalid_json"
const ReasonCodeSchemaInvalid = "json_schema_invalid"

type Options struct{}
type Validator struct{}

var _ contracts.SerializedValidator = (*Validator)(nil)

func New(Options) *Validator      { return &Validator{} }
func (v *Validator) Name() string { return Key }
func (v *Validator) ExecutionClass() contracts.ExecutionClass {
	return contracts.ExecutionClassDeterministic
}

func (v *Validator) Validate(_ context.Context, req contracts.SerializedValidationRequest) (contracts.ValidationResult, error) {
	return validate(req.Content, req.Schema.JSONSchema)
}

func validate(content, schemaContent []byte) (contracts.ValidationResult, error) {
	if len(schemaContent) == 0 {
		return contracts.ValidationResult{}, fmt.Errorf("response schema content is not available")
	}
	instance, err := jsonschema.UnmarshalJSON(bytes.NewReader(content))
	if err != nil {
		return contracts.ValidationResult{Approved: false, ReasonCode: ReasonCodeInvalidJSON, Message: "payload is not valid JSON"}, nil
	}
	schemaDocument, err := jsonschema.UnmarshalJSON(bytes.NewReader(schemaContent))
	if err != nil {
		return contracts.ValidationResult{}, fmt.Errorf("parse response schema: %w", err)
	}
	compiler := jsonschema.NewCompiler()
	if err := compiler.AddResource("schema.json", schemaDocument); err != nil {
		return contracts.ValidationResult{}, fmt.Errorf("load response schema: %w", err)
	}
	schema, err := compiler.Compile("schema.json")
	if err != nil {
		return contracts.ValidationResult{}, fmt.Errorf("compile response schema: %w", err)
	}
	if err := schema.Validate(instance); err != nil {
		return contracts.ValidationResult{Approved: false, ReasonCode: ReasonCodeSchemaInvalid, Message: "payload does not conform to response schema"}, nil
	}
	return contracts.ValidationResult{Approved: true}, nil
}

func Spec() pipeline.ValidatorSpec {
	return pipeline.ValidatorSpec{Key: Key, ExecutionClass: contracts.ExecutionClassDeterministic}
}

func Register(registry *pipeline.ValidatorRegistry) error {
	return pipeline.RegisterSerializedValidatorBuilder(registry, pipeline.SerializedValidatorSpec{
		ValidatorSpec: Spec(), SupportsChunks: true, SupportsArtifacts: true,
	}, validateOptions, func(request pipeline.BuildRequest) (contracts.SerializedValidator, error) {
		options, err := DecodeOptions(request.Options)
		if err != nil {
			return nil, err
		}
		return New(options), nil
	})
}

func DecodeOptions(options map[string]any) (Options, error) {
	if err := pipeline.RejectUnknownOptions(options); err != nil {
		return Options{}, err
	}
	return Options{}, nil
}
func validateOptions(options map[string]any) error { _, err := DecodeOptions(options); return err }