package service

import (
	"context"
	"errors"
	"fmt"
	"regexp"
	"strings"

	"gorm.io/datatypes"

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

// 1:1 Chatwoot: attribute_key format regex — /\A[\p{L}\p{N}_.-]+\z/
// Unicode letters/digits + underscore + dot + hyphen
var attributeKeyFormatRegex = regexp.MustCompile(`^[\p{L}\p{N}_.-]+$`)

// 1:1 Chatwoot: STANDARD_ATTRIBUTES — reserved attribute keys per model
var StandardAttributes = map[string][]string{
	"conversation": {"status", "priority", "assignee_id", "inbox_id", "team_id", "display_id", "campaign_id", "labels", "browser_language", "country_code", "referer", "created_at", "last_activity_at"},
	"contact":      {"name", "email", "phone_number", "identifier", "country_code", "city", "company_name", "created_at", "last_activity_at", "referer", "blocked"},
	"company":      {"name", "domain", "description", "contacts_count", "created_at", "updated_at", "last_activity_at"},
}

// CustomAttributeDefinitionService implements business logic for custom attribute definitions.
// Reference: Chatwoot app/controllers/api/v1/accounts/custom_attribute_definitions_controller.rb
type CustomAttributeDefinitionService struct {
	repo *repository.CustomAttributeDefinitionRepo
}

// NewCustomAttributeDefinitionService creates a new service.
func NewCustomAttributeDefinitionService(repo *repository.CustomAttributeDefinitionRepo) *CustomAttributeDefinitionService {
	return &CustomAttributeDefinitionService{repo: repo}
}

// CreateCustomAttributeDefinitionRequest is the DTO for creating a definition.
// Chatwoot compatibility: uses attribute_key, attribute_display_type, attribute_description
type CreateCustomAttributeDefinitionRequest struct {
	AttributeKey          string         `json:"attribute_key" validate:"required,min=1"`              // Chatwoot: attribute_key (maps to attribute_name)
	AttributeDisplayName  string         `json:"attribute_display_name" validate:"required,min=1"`
	AttributeDisplayType  string         `json:"attribute_display_type" validate:"required,oneof=text number date checkbox list link currency percent"` // 1:1 Chatwoot: added currency, percent
	AttributeModel        string         `json:"attribute_model" validate:"required,oneof=conversation contact company"` // 1:1 Chatwoot: added company_attribute
	DefaultValue          datatypes.JSON `json:"default_value,omitempty"`
	AttributeValues       datatypes.JSON `json:"attribute_values,omitempty"`  // Predefined valid values for list-type attributes
	RegexPattern          string         `json:"regex_pattern,omitempty"`    // Regex validation pattern
	RegexCue              string         `json:"regex_cue,omitempty"`        // Regex validation hint
	AttributeDescription  string         `json:"attribute_description,omitempty"`
}

// UpdateCustomAttributeDefinitionRequest is the DTO for updating a definition.
// Chatwoot compatibility: uses attribute_key, attribute_display_type, attribute_description
type UpdateCustomAttributeDefinitionRequest struct {
	AttributeDisplayName  string         `json:"attribute_display_name,omitempty" validate:"omitempty,min=1"`
	AttributeDisplayType  string         `json:"attribute_display_type,omitempty" validate:"omitempty,oneof=text number date checkbox list link"`
	DefaultValue          datatypes.JSON `json:"default_value,omitempty"`
	AttributeValues       datatypes.JSON `json:"attribute_values,omitempty"`
	RegexPattern          string         `json:"regex_pattern,omitempty"`
	RegexCue              string         `json:"regex_cue,omitempty"`
	AttributeDescription  string         `json:"attribute_description,omitempty"`
}

// Create creates a new custom attribute definition for an account.
func (s *CustomAttributeDefinitionService) Create(ctx context.Context, accountID uint, req *CreateCustomAttributeDefinitionRequest) (*model.CustomAttributeDefinition, error) {
	if err := pkgvalidator.ValidateStruct(req); err != nil {
		return nil, err
	}

	// 1:1 Chatwoot: normalize_attribute_fields — strip whitespace
	req.AttributeKey = strings.TrimSpace(req.AttributeKey)
	req.AttributeDisplayName = strings.TrimSpace(req.AttributeDisplayName)

	// 1:1 Chatwoot: attribute_key format validation — /\A[\p{L}\p{N}_.-]+\z/
	if !attributeKeyFormatRegex.MatchString(req.AttributeKey) {
		return nil, fmt.Errorf("attribute_key format invalid: must contain only letters, numbers, underscores, dots, and hyphens")
	}

	// 1:1 Chatwoot: attribute_must_not_conflict — key cannot be a standard attribute
	modelKey := strings.TrimSuffix(req.AttributeModel, "_attribute") // "conversation", "contact", "company"
	if standardAttrs, ok := StandardAttributes[modelKey]; ok {
		for _, sa := range standardAttrs {
			if req.AttributeKey == sa {
				return nil, fmt.Errorf("attribute_key '%s' conflicts with standard attribute for %s", req.AttributeKey, modelKey)
			}
		}
	}

	def := &model.CustomAttributeDefinition{
		AccountID:            accountID,
		AttributeName:        req.AttributeKey,
		AttributeDisplayName: req.AttributeDisplayName,
		AttributeType:        req.AttributeDisplayType,
		AttributeModel:       req.AttributeModel,
		DefaultValue:         req.DefaultValue,
		AttributeValues:      req.AttributeValues,
		RegexPattern:         req.RegexPattern,
		RegexCue:             req.RegexCue,
		Description:          req.AttributeDescription,
	}

	if err := s.repo.Create(ctx, def); err != nil {
		applogger.L().Errorf("Create custom attribute definition failed: %v", err)
		return nil, err
	}

	return def, nil
}

// Get retrieves a definition by ID, verifying it belongs to the account.
func (s *CustomAttributeDefinitionService) Get(ctx context.Context, accountID, id uint) (*model.CustomAttributeDefinition, error) {
	def, err := s.repo.GetByID(ctx, id)
	if err != nil {
		return nil, err
	}
	if def.AccountID != accountID {
		return nil, errors.New("custom attribute definition not found")
	}
	return def, nil
}

// List retrieves definitions for an account, optionally filtered by attribute_model.
func (s *CustomAttributeDefinitionService) List(ctx context.Context, accountID uint, attributeModel string, offset, limit int) ([]model.CustomAttributeDefinition, int64, error) {
	if attributeModel != "" {
		return s.repo.FindByAccountAndModel(ctx, accountID, attributeModel, offset, limit)
	}
	return s.repo.FindByAccount(ctx, accountID, offset, limit)
}

// Update modifies a definition, verifying it belongs to the account.
func (s *CustomAttributeDefinitionService) Update(ctx context.Context, accountID, id uint, req *UpdateCustomAttributeDefinitionRequest) (*model.CustomAttributeDefinition, error) {
	if err := pkgvalidator.ValidateStruct(req); err != nil {
		return nil, err
	}

	def, err := s.repo.GetByID(ctx, id)
	if err != nil {
		return nil, err
	}
	if def.AccountID != accountID {
		return nil, errors.New("custom attribute definition not found")
	}

	if req.AttributeDisplayName != "" {
		def.AttributeDisplayName = req.AttributeDisplayName
	}
	if req.AttributeDisplayType != "" {
		def.AttributeType = req.AttributeDisplayType
	}
	if req.DefaultValue != nil {
		def.DefaultValue = req.DefaultValue
	}
	if req.AttributeValues != nil {
		def.AttributeValues = req.AttributeValues
	}
	if req.RegexPattern != "" {
		def.RegexPattern = req.RegexPattern
	}
	if req.RegexCue != "" {
		def.RegexCue = req.RegexCue
	}
	if req.AttributeDescription != "" {
		def.Description = req.AttributeDescription
	}

	if err := s.repo.Update(ctx, def); err != nil {
		applogger.L().Errorf("Update custom attribute definition failed: %v", err)
		return nil, err
	}

	return def, nil
}

// Delete soft-deletes a definition, verifying it belongs to the account.
func (s *CustomAttributeDefinitionService) Delete(ctx context.Context, accountID, id uint) error {
	def, err := s.repo.GetByID(ctx, id)
	if err != nil {
		return err
	}
	if def.AccountID != accountID {
		return errors.New("custom attribute definition not found")
	}

	return s.repo.Delete(ctx, id)
}