package service

import (
	"context"
	"encoding/json"
	"errors"

	"gorm.io/datatypes"

	"github.com/gochat/gochat/internal/model"
	"github.com/gochat/gochat/internal/repository"
	applogger "github.com/gochat/gochat/pkg/logger"
)

// CustomAttributeValueService handles setting and removing custom attribute values
// on conversations and contacts.
// Reference: Chatwoot app/controllers/api/v1/accounts/custom_attribute_definitions_controller.rb
// The value operations merge/remove individual keys into the CustomAttributes jsonb field.
type CustomAttributeValueService struct {
	defRepo   *repository.CustomAttributeDefinitionRepo
	convRepo  *repository.ConversationRepo
	contactRepo *repository.ContactRepo
}

// NewCustomAttributeValueService creates a new service.
func NewCustomAttributeValueService(
	defRepo *repository.CustomAttributeDefinitionRepo,
	convRepo *repository.ConversationRepo,
	contactRepo *repository.ContactRepo,
) *CustomAttributeValueService {
	return &CustomAttributeValueService{
		defRepo:   defRepo,
		convRepo:  convRepo,
		contactRepo: contactRepo,
	}
}

// SetAttributeValueRequest is the DTO for setting a custom attribute value.
type SetAttributeValueRequest struct {
	AttributeName string      `json:"attribute_name" validate:"required,min=1"`
	Value         interface{} `json:"value" validate:"required"`
}

// validateAttributeDefinition checks that the attribute definition exists for the account and model.
func (s *CustomAttributeValueService) validateAttributeDefinition(ctx context.Context, accountID uint, attributeName, attributeModel string) (*model.CustomAttributeDefinition, error) {
	defs, _, err := s.defRepo.FindByAccountAndModel(ctx, accountID, attributeModel, 0, 1000)
	if err != nil {
		return nil, err
	}
	for _, def := range defs {
		if def.AttributeName == attributeName {
			return &def, nil
		}
	}
	return nil, errors.New("custom attribute definition not found for this model type")
}

// mergeIntoJSON merges a single key-value pair into an existing datatypes.JSON object.
// If the existing JSON is nil or empty, it creates a new map.
func mergeIntoJSON(existing datatypes.JSON, key string, value interface{}) (datatypes.JSON, error) {
	var mapData map[string]interface{}
	if existing != nil && len(existing) > 0 {
		if err := json.Unmarshal(existing, &mapData); err != nil {
			// If unmarshal fails, start fresh
			mapData = make(map[string]interface{})
		}
	} else {
		mapData = make(map[string]interface{})
	}
	mapData[key] = value
	result, err := json.Marshal(mapData)
	if err != nil {
		return nil, err
	}
	return datatypes.JSON(result), nil
}

// removeFromJSON removes a single key from an existing datatypes.JSON object.
// If the key doesn't exist, the JSON is returned unchanged.
func removeFromJSON(existing datatypes.JSON, key string) (datatypes.JSON, error) {
	if existing == nil || len(existing) == 0 {
		return datatypes.JSON("{}"), nil
	}
	var mapData map[string]interface{}
	if err := json.Unmarshal(existing, &mapData); err != nil {
		return nil, err
	}
	delete(mapData, key)
	result, err := json.Marshal(mapData)
	if err != nil {
		return nil, err
	}
	return datatypes.JSON(result), nil
}

// SetConversationAttributeValue sets a custom attribute value on a conversation.
// It validates the attribute definition exists for the account and "conversation" model,
// then merges the value into the conversation's CustomAttributes jsonb field.
func (s *CustomAttributeValueService) SetConversationAttributeValue(ctx context.Context, accountID, conversationID uint, req *SetAttributeValueRequest) (*model.Conversation, error) {
	// Validate attribute definition exists for conversation model
	def, err := s.validateAttributeDefinition(ctx, accountID, req.AttributeName, "conversation")
	if err != nil {
		return nil, err
	}

	// Validate value type matches attribute_type
	if err := validateValueType(def.AttributeType, req.Value); err != nil {
		return nil, err
	}

	// Fetch the conversation
	conversation, err := s.convRepo.FindByAccountAndID(ctx, accountID, conversationID)
	if err != nil {
		return nil, err
	}

	// Merge the new attribute value into existing custom attributes
	merged, mergeErr := mergeIntoJSON(conversation.CustomAttributes, req.AttributeName, req.Value)
	if mergeErr != nil {
		applogger.L().Errorf("Merge custom attribute value failed: %v", mergeErr)
		return nil, mergeErr
	}

	if err := s.convRepo.UpdateCustomAttributes(ctx, conversationID, merged); err != nil {
		applogger.L().Errorf("Update conversation custom attributes failed: %v", err)
		return nil, err
	}

	// Re-fetch to return updated state
	conversation, err = s.convRepo.FindByAccountAndID(ctx, accountID, conversationID)
	if err != nil {
		return nil, err
	}
	return conversation, nil
}

// RemoveConversationAttributeValue removes a custom attribute key from a conversation.
func (s *CustomAttributeValueService) RemoveConversationAttributeValue(ctx context.Context, accountID, conversationID uint, attributeName string) (*model.Conversation, error) {
	// Validate attribute definition exists
	if _, err := s.validateAttributeDefinition(ctx, accountID, attributeName, "conversation"); err != nil {
		return nil, err
	}

	// Fetch the conversation
	conversation, err := s.convRepo.FindByAccountAndID(ctx, accountID, conversationID)
	if err != nil {
		return nil, err
	}

	// Remove the key from custom attributes
	updated, removeErr := removeFromJSON(conversation.CustomAttributes, attributeName)
	if removeErr != nil {
		applogger.L().Errorf("Remove custom attribute value failed: %v", removeErr)
		return nil, removeErr
	}

	if err := s.convRepo.UpdateCustomAttributes(ctx, conversationID, updated); err != nil {
		applogger.L().Errorf("Update conversation custom attributes failed: %v", err)
		return nil, err
	}

	// Re-fetch to return updated state
	conversation, err = s.convRepo.FindByAccountAndID(ctx, accountID, conversationID)
	if err != nil {
		return nil, err
	}
	return conversation, nil
}

// SetContactAttributeValue sets a custom attribute value on a contact.
func (s *CustomAttributeValueService) SetContactAttributeValue(ctx context.Context, accountID, contactID uint, req *SetAttributeValueRequest) (*model.Contact, error) {
	// Validate attribute definition exists for contact model
	def, err := s.validateAttributeDefinition(ctx, accountID, req.AttributeName, "contact")
	if err != nil {
		return nil, err
	}

	// Validate value type matches attribute_type
	if err := validateValueType(def.AttributeType, req.Value); err != nil {
		return nil, err
	}

	// Fetch the contact
	contact, err := s.contactRepo.FindByAccountAndID(ctx, accountID, contactID)
	if err != nil {
		return nil, err
	}

	// Merge the new attribute value into existing custom attributes
	merged, mergeErr := mergeIntoJSON(contact.CustomAttributes, req.AttributeName, req.Value)
	if mergeErr != nil {
		applogger.L().Errorf("Merge custom attribute value failed: %v", mergeErr)
		return nil, mergeErr
	}

	if err := s.contactRepo.UpdateCustomAttributes(ctx, contactID, merged); err != nil {
		applogger.L().Errorf("Update contact custom attributes failed: %v", err)
		return nil, err
	}

	// Re-fetch to return updated state
	contact, err = s.contactRepo.FindByAccountAndID(ctx, accountID, contactID)
	if err != nil {
		return nil, err
	}
	return contact, nil
}

// RemoveContactAttributeValue removes a custom attribute key from a contact.
func (s *CustomAttributeValueService) RemoveContactAttributeValue(ctx context.Context, accountID, contactID uint, attributeName string) (*model.Contact, error) {
	// Validate attribute definition exists
	if _, err := s.validateAttributeDefinition(ctx, accountID, attributeName, "contact"); err != nil {
		return nil, err
	}

	// Fetch the contact
	contact, err := s.contactRepo.FindByAccountAndID(ctx, accountID, contactID)
	if err != nil {
		return nil, err
	}

	// Remove the key from custom attributes
	updated, removeErr := removeFromJSON(contact.CustomAttributes, attributeName)
	if removeErr != nil {
		applogger.L().Errorf("Remove custom attribute value failed: %v", removeErr)
		return nil, removeErr
	}

	if err := s.contactRepo.UpdateCustomAttributes(ctx, contactID, updated); err != nil {
		applogger.L().Errorf("Update contact custom attributes failed: %v", err)
		return nil, err
	}

	// Re-fetch to return updated state
	contact, err = s.contactRepo.FindByAccountAndID(ctx, accountID, contactID)
	if err != nil {
		return nil, err
	}
	return contact, nil
}

// validateValueType checks that the provided value matches the expected attribute type.
func validateValueType(attributeType string, value interface{}) error {
	switch attributeType {
	case "text", "link":
		if _, ok := value.(string); !ok {
			return errors.New("value must be a string for text/link attribute type")
		}
	case "number":
		// JSON numbers can be float or int — accept both
		switch value.(type) {
		case float64, int, int64, int32, float32:
			// OK
		default:
			return errors.New("value must be a number for number attribute type")
		}
	case "date":
		if _, ok := value.(string); !ok {
			return errors.New("value must be a string (date format) for date attribute type")
		}
	case "checkbox":
		if _, ok := value.(bool); !ok {
			return errors.New("value must be a boolean for checkbox attribute type")
		}
	case "list":
		// List can hold any JSON-serializable value
		return nil
	default:
		return nil // Unknown types are accepted
	}
	return nil
}