package retriever

import (
	"strings"
)

const (
	obrimRetrieverTypeJson = "json"
	obrimRetrieverTypeDb   = "db"

	obrimRetrieverCodeSuccessResource = "SUCCESS_RESOURCE_RETRIEVED"
	obrimRetrieverCodeSuccessPath     = "SUCCESS_PATH_RETRIEVED"
	obrimRetrieverCodeSuccessFields   = "SUCCESS_FIELDS_RETRIEVED"

	obrimRetrieverCodeFailedUnsupportedType  = "FAILED_UNSUPPORTED_TYPE"
	obrimRetrieverCodeFailedMissingConfig    = "FAILED_MISSING_CONFIGURATION"
	obrimRetrieverCodeFailedInvalidConfig    = "FAILED_INVALID_CONFIGURATION"
	obrimRetrieverCodeFailedResourceNotFound = "FAILED_RESOURCE_NOT_FOUND"
	obrimRetrieverCodeFailedPathNotFound     = "FAILED_PATH_NOT_FOUND"
	obrimRetrieverCodeFailedFieldNotFound    = "FAILED_FIELD_NOT_FOUND"
	obrimRetrieverCodeFailedNotImplemented   = "FAILED_NOT_IMPLEMENTED"
)

// ObrimRetrieverJsonProviderRegistry stores registered JSON providers.
var ObrimRetrieverJsonProviderRegistry = map[string]any{}

// ObrimRetrieverDbProviderRegistry stores registered database providers.
var ObrimRetrieverDbProviderRegistry = map[string]any{}

// ObrimRetrieverResponse defines the standardized utility response structure.
type ObrimRetrieverResponse struct {
	Status  bool           `json:"status"`
	Code    string         `json:"code"`
	Payload map[string]any `json:"payload"`
}

// ObrimRetriever retrieves data using a unified retrieval interface.
func ObrimRetriever(retrievalType string, config map[string]any) map[string]any {
	if !obrimRetrieverValidateType(retrievalType) {
		return obrimRetrieverBuildResponse(
			false,
			obrimRetrieverCodeFailedUnsupportedType,
			nil,
		)
	}

	validationCode := obrimRetrieverValidateConfig(retrievalType, config)

	if validationCode != "" {
		return obrimRetrieverBuildResponse(
			false,
			validationCode,
			nil,
		)
	}

	switch retrievalType {
	case obrimRetrieverTypeJson:
		return obrimRetrieverJson(config)

	case obrimRetrieverTypeDb:
		return obrimRetrieverDb(config)

	default:
		return obrimRetrieverBuildResponse(
			false,
			obrimRetrieverCodeFailedUnsupportedType,
			nil,
		)
	}
}

// ObrimRetrieverJsonRegister registers a JSON provider.
func ObrimRetrieverJsonRegister(resource string, provider any) {
	if strings.TrimSpace(resource) == "" {
		return
	}

	ObrimRetrieverJsonProviderRegistry[resource] = provider
}

// ObrimRetrieverDbRegister registers a database provider.
func ObrimRetrieverDbRegister(resource string, provider any) {
	if strings.TrimSpace(resource) == "" {
		return
	}

	ObrimRetrieverDbProviderRegistry[resource] = provider
}

// obrimRetrieverValidateType validates a retrieval type.
func obrimRetrieverValidateType(retrievalType string) bool {
	switch retrievalType {
	case obrimRetrieverTypeJson:
		return true

	case obrimRetrieverTypeDb:
		return true

	default:
		return false
	}
}

// obrimRetrieverValidateConfig validates retrieval configuration.
func obrimRetrieverValidateConfig(
	retrievalType string,
	config map[string]any,
) string {
	if config == nil {
		return obrimRetrieverCodeFailedMissingConfig
	}

	switch retrievalType {
	case obrimRetrieverTypeJson:
		return obrimRetrieverJsonValidate(config)

	case obrimRetrieverTypeDb:
		return obrimRetrieverDbValidate(config)

	default:
		return obrimRetrieverCodeFailedUnsupportedType
	}
}

// obrimRetrieverResolveProvider resolves a provider by resource identifier.
func obrimRetrieverResolveProvider(
	retrievalType string,
	resource string,
) (any, bool) {
	switch retrievalType {
	case obrimRetrieverTypeJson:
		provider, exists := ObrimRetrieverJsonProviderRegistry[resource]
		return provider, exists

	case obrimRetrieverTypeDb:
		provider, exists := ObrimRetrieverDbProviderRegistry[resource]
		return provider, exists

	default:
		return nil, false
	}
}

// obrimRetrieverBuildResponse builds a standardized utility response.
func obrimRetrieverBuildResponse(
	status bool,
	code string,
	payload map[string]any,
) map[string]any {
	return map[string]any{
		"status":  status,
		"code":    code,
		"payload": payload,
	}
}

// obrimRetrieverJson processes JSON retrieval requests.
func obrimRetrieverJson(config map[string]any) map[string]any {
	resource := config["resource"].(string)

	provider, exists := obrimRetrieverResolveProvider(
		obrimRetrieverTypeJson,
		resource,
	)

	if !exists {
		return obrimRetrieverBuildResponse(
			false,
			obrimRetrieverCodeFailedResourceNotFound,
			nil,
		)
	}

	if fields, exists := config["fields"]; exists {
		return obrimRetrieverJsonFields(provider, fields)
	}

	if path, exists := config["path"]; exists {
		return obrimRetrieverJsonPath(provider, path.(string))
	}

	return obrimRetrieverJsonResource(provider)
}

// obrimRetrieverJsonResource retrieves an entire resource.
func obrimRetrieverJsonResource(provider any) map[string]any {
	data, success := obrimRetrieverJsonRetrieve(provider)

	if !success {
		return obrimRetrieverBuildResponse(
			false,
			obrimRetrieverCodeFailedResourceNotFound,
			nil,
		)
	}

	return obrimRetrieverBuildResponse(
		true,
		obrimRetrieverCodeSuccessResource,
		map[string]any{
			"data": data,
		},
	)
}

// obrimRetrieverJsonPath retrieves a value using a dot-notation path.
func obrimRetrieverJsonPath(provider any, path string) map[string]any {
	data, success := obrimRetrieverJsonRetrieve(provider)

	if !success {
		return obrimRetrieverBuildResponse(
			false,
			obrimRetrieverCodeFailedResourceNotFound,
			nil,
		)
	}

	value, found := obrimRetrieverJsonResolvePath(data, path)

	if !found {
		return obrimRetrieverBuildResponse(
			false,
			obrimRetrieverCodeFailedPathNotFound,
			nil,
		)
	}

	return obrimRetrieverBuildResponse(
		true,
		obrimRetrieverCodeSuccessPath,
		map[string]any{
			"data": value,
		},
	)
}

// obrimRetrieverJsonFields retrieves multiple values using field selection.
func obrimRetrieverJsonFields(provider any, fieldsValue any) map[string]any {
	data, success := obrimRetrieverJsonRetrieve(provider)

	if !success {
		return obrimRetrieverBuildResponse(
			false,
			obrimRetrieverCodeFailedResourceNotFound,
			nil,
		)
	}

	fields, valid := obrimRetrieverJsonNormalizeFields(fieldsValue)

	if !valid {
		return obrimRetrieverBuildResponse(
			false,
			obrimRetrieverCodeFailedInvalidConfig,
			nil,
		)
	}

	result := map[string]any{}

	for _, field := range fields {
		value, found := obrimRetrieverJsonResolvePath(data, field)

		if !found {
			return obrimRetrieverBuildResponse(
				false,
				obrimRetrieverCodeFailedFieldNotFound,
				nil,
			)
		}

		result[field] = value
	}

	return obrimRetrieverBuildResponse(
		true,
		obrimRetrieverCodeSuccessFields,
		map[string]any{
			"data": result,
		},
	)
}

// obrimRetrieverJsonValidate validates JSON retrieval configuration.
func obrimRetrieverJsonValidate(config map[string]any) string {
	resourceValue, exists := config["resource"]

	if !exists {
		return obrimRetrieverCodeFailedMissingConfig
	}

	resource, valid := resourceValue.(string)

	if !valid {
		return obrimRetrieverCodeFailedInvalidConfig
	}

	if strings.TrimSpace(resource) == "" {
		return obrimRetrieverCodeFailedInvalidConfig
	}

	_, pathExists := config["path"]
	_, fieldsExists := config["fields"]

	if pathExists && fieldsExists {
		return obrimRetrieverCodeFailedInvalidConfig
	}

	if pathExists {
		path, valid := config["path"].(string)

		if !valid || strings.TrimSpace(path) == "" {
			return obrimRetrieverCodeFailedInvalidConfig
		}
	}

	if fieldsExists {
		fields, valid := obrimRetrieverJsonNormalizeFields(config["fields"])

		if !valid || len(fields) == 0 {
			return obrimRetrieverCodeFailedInvalidConfig
		}
	}

	return ""
}

// obrimRetrieverDb processes database retrieval requests.
func obrimRetrieverDb(config map[string]any) map[string]any {
	return obrimRetrieverBuildResponse(
		false,
		obrimRetrieverCodeFailedNotImplemented,
		nil,
	)
}

// obrimRetrieverDbValidate validates database retrieval configuration.
func obrimRetrieverDbValidate(config map[string]any) string {
	return ""
}

// obrimRetrieverJsonRetrieve retrieves resource data from a provider.
func obrimRetrieverJsonRetrieve(provider any) (any, bool) {
	switch retrievalProvider := provider.(type) {
	case func() any:
		return retrievalProvider(), true

	case func() map[string]any:
		return retrievalProvider(), true

	case func() (any, bool):
		return retrievalProvider()

	case map[string]any:
		return retrievalProvider, true

	default:
		return nil, false
	}
}

// obrimRetrieverJsonResolvePath resolves a dot-notation path.
func obrimRetrieverJsonResolvePath(data any, path string) (any, bool) {
	current := data

	for _, segment := range strings.Split(path, ".") {
		object, valid := current.(map[string]any)

		if !valid {
			return nil, false
		}

		value, exists := object[segment]

		if !exists {
			return nil, false
		}

		current = value
	}

	return current, true
}

// obrimRetrieverJsonNormalizeFields normalizes field selections.
func obrimRetrieverJsonNormalizeFields(fieldsValue any) ([]string, bool) {
	switch fields := fieldsValue.(type) {
	case []string:
		return fields, true

	case []any:
		result := make([]string, 0, len(fields))

		for _, field := range fields {
			fieldString, valid := field.(string)

			if !valid {
				return nil, false
			}

			result = append(result, fieldString)
		}

		return result, true

	default:
		return nil, false
	}
}