package service

// PlatformUserService handles business logic for Platform API user endpoints.
// Reference: Chatwoot Platform::Api::V1::UsersController — AccessToken authenticated
//
// These endpoints are distinct from the SuperAdmin-platform routes because they use
// AccessToken authentication (api_access_token header) instead of JWT+SuperAdmin.
// The Permissible system governs which resources each PlatformApp can access.
import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"time"

	"github.com/gochat/gochat/internal/model"
	"github.com/gochat/gochat/internal/repository"
	"gorm.io/datatypes"
	"gorm.io/gorm"
)

// PlatformUserService provides user CRUD for Platform API (AccessToken auth).
type PlatformUserService struct {
	userRepo        *repository.UserRepo
	permissibleRepo *repository.PermissibleRepo
	accessTokenRepo *repository.AccessTokenRepo
	accountUserRepo *repository.AccountUserRepo
}

type PlatformUserRequest struct {
	Name             string         `json:"name"`
	DisplayName      string         `json:"display_name"`
	Email            string         `json:"email"`
	Password         string         `json:"password"`
	CustomAttributes map[string]any `json:"custom_attributes"`
}

type PlatformUserResponse struct {
	User         model.User
	AccessToken  string
	AccountUsers []model.AccountUser
}

// NewPlatformUserService creates a new PlatformUserService.
func NewPlatformUserService(
	userRepo *repository.UserRepo,
	permissibleRepo *repository.PermissibleRepo,
	extras ...any,
) *PlatformUserService {
	svc := &PlatformUserService{
		userRepo:        userRepo,
		permissibleRepo: permissibleRepo,
	}
	for _, extra := range extras {
		switch repo := extra.(type) {
		case *repository.AccessTokenRepo:
			svc.accessTokenRepo = repo
		case *repository.AccountUserRepo:
			svc.accountUserRepo = repo
		}
	}
	return svc
}

// ValidatePermissible checks that the PlatformApp has permission to access the target user.
func (s *PlatformUserService) ValidatePermissible(ctx context.Context, platformAppID uint, userID uint) error {
	perm, err := s.permissibleRepo.FindByPlatformAppAndResource(ctx, platformAppID, model.PermissibleTypeUser, userID)
	if err != nil {
		// GORM returns "record not found" when no matching row — treat as non-permissible
		return errors.New("non permissible resource")
	}
	if perm == nil {
		return errors.New("non permissible resource")
	}
	return nil
}

// GetUser retrieves a user by ID, after verifying permissible access.
func (s *PlatformUserService) GetUser(ctx context.Context, platformAppID uint, userID uint) (*model.User, error) {
	if err := s.ValidatePermissible(ctx, platformAppID, userID); err != nil {
		return nil, err
	}
	return s.userRepo.FindByID(ctx, userID)
}

func (s *PlatformUserService) GetUserResponse(ctx context.Context, platformAppID uint, userID uint) (*PlatformUserResponse, error) {
	user, err := s.GetUser(ctx, platformAppID, userID)
	if err != nil {
		return nil, err
	}
	return s.BuildUserResponse(ctx, user)
}

// CreateUser creates a new user and auto-creates a Permissible record.
// Reference: Chatwoot UsersController#create — skips confirmation, auto-permissible
func (s *PlatformUserService) CreateUser(ctx context.Context, platformAppID uint, req PlatformUserRequest) (*PlatformUserResponse, error) {
	user, err := s.userRepo.FindByEmail(ctx, req.Email)
	if err != nil {
		if !errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, err
		}
		confirmedAt := time.Now().UTC()
		attrs, attrsErr := marshalCustomAttributes(req.CustomAttributes)
		if attrsErr != nil {
			return nil, attrsErr
		}
		user = &model.User{
			Name:             req.Name,
			DisplayName:      req.DisplayName,
			Email:            req.Email,
			Password:         req.Password,
			Provider:         "email",
			CustomAttributes: attrs,
			ConfirmedAt:      &confirmedAt,
			Active:           true,
		}
		if err := s.userRepo.Create(ctx, user); err != nil {
			return nil, err
		}
	}

	// Auto-create Permissible record (PlatformApp can access this user)
	if _, err := s.permissibleRepo.FindByPlatformAppAndResource(ctx, platformAppID, model.PermissibleTypeUser, user.ID); err != nil {
		if !errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, err
		}
		perm := &model.Permissible{
			PlatformAppID:   platformAppID,
			PermissibleType: model.PermissibleTypeUser,
			PermissibleID:   user.ID,
		}
		if err := s.permissibleRepo.Create(ctx, perm); err != nil {
			return nil, err
		}
	}

	return s.BuildUserResponse(ctx, user)
}

// UpdateUser updates a user, after verifying permissible access.
// Reference: Chatwoot UsersController#update — merges custom_attributes, skips reconfirmation
func (s *PlatformUserService) UpdateUser(ctx context.Context, platformAppID uint, userID uint, req PlatformUserRequest) (*PlatformUserResponse, error) {
	if err := s.ValidatePermissible(ctx, platformAppID, userID); err != nil {
		return nil, err
	}

	user, err := s.userRepo.FindByID(ctx, userID)
	if err != nil {
		return nil, err
	}

	if req.Name != "" {
		user.Name = req.Name
	}
	if req.DisplayName != "" {
		user.DisplayName = req.DisplayName
	}
	if req.Email != "" {
		user.Email = req.Email
	}
	if req.Password != "" {
		user.Password = req.Password
	}
	if req.CustomAttributes != nil {
		merged := platformJSONObj(user.CustomAttributes)
		for key, value := range req.CustomAttributes {
			merged[key] = value
		}
		attrs, err := marshalCustomAttributes(merged)
		if err != nil {
			return nil, err
		}
		user.CustomAttributes = attrs
	}

	if err := s.userRepo.Update(ctx, user); err != nil {
		return nil, err
	}
	return s.BuildUserResponse(ctx, user)
}

func (s *PlatformUserService) BuildUserResponse(ctx context.Context, user *model.User) (*PlatformUserResponse, error) {
	if user == nil {
		return nil, errors.New("user is nil")
	}
	accessToken, err := s.currentAccessToken(ctx, user.ID)
	if err != nil {
		return nil, err
	}
	var accountUsers []model.AccountUser
	if s.accountUserRepo != nil {
		accountUsers, err = s.accountUserRepo.FindByUserWithAccounts(ctx, user.ID)
		if err != nil {
			return nil, err
		}
	}
	return &PlatformUserResponse{User: *user, AccessToken: accessToken, AccountUsers: accountUsers}, nil
}

func (s *PlatformUserService) TokenResponse(ctx context.Context, platformAppID uint, userID uint) (*PlatformUserResponse, error) {
	return s.GetUserResponse(ctx, platformAppID, userID)
}

func (s *PlatformUserService) currentAccessToken(ctx context.Context, userID uint) (string, error) {
	if s.accessTokenRepo == nil {
		return "", nil
	}
	tokens, err := s.accessTokenRepo.FindActiveByOwner(ctx, model.AccessTokenOwnerTypeUser, userID)
	if err != nil {
		return "", fmt.Errorf("failed to load access token: %w", err)
	}
	if len(tokens) > 0 {
		return tokens[0].Token, nil
	}
	plainToken, err := generatePlatformAccessToken()
	if err != nil {
		return "", err
	}
	accessToken := &model.AccessToken{
		OwnerType:   model.AccessTokenOwnerTypeUser,
		OwnerID:     userID,
		Token:       plainToken,
		TokenPrefix: tokenPrefix(plainToken),
		Name:        "Personal Access Token",
	}
	if err := s.accessTokenRepo.Create(ctx, accessToken); err != nil {
		return "", err
	}
	return plainToken, nil
}

// DeleteUser deletes a user, after verifying permissible access.
// Reference: Chatwoot UsersController#destroy — uses DeleteObjectJob (async)
func (s *PlatformUserService) DeleteUser(ctx context.Context, platformAppID uint, userID uint) error {
	if err := s.ValidatePermissible(ctx, platformAppID, userID); err != nil {
		return err
	}
	return s.userRepo.Delete(ctx, userID)
}

func marshalCustomAttributes(attrs map[string]any) (datatypes.JSON, error) {
	if attrs == nil {
		return datatypes.JSON([]byte(`{}`)), nil
	}
	data, err := json.Marshal(attrs)
	if err != nil {
		return nil, err
	}
	return datatypes.JSON(data), nil
}

func platformJSONObj(raw datatypes.JSON) map[string]any {
	if len(raw) == 0 {
		return map[string]any{}
	}
	var obj map[string]any
	if err := json.Unmarshal(raw, &obj); err != nil || obj == nil {
		return map[string]any{}
	}
	return obj
}

// ListPermissibleUsers returns all users that the PlatformApp has permissible access to.
func (s *PlatformUserService) ListPermissibleUsers(ctx context.Context, platformAppID uint) ([]model.User, error) {
	permissibles, err := s.permissibleRepo.FindByPlatformAppID(ctx, platformAppID)
	if err != nil {
		return nil, err
	}

	var users []model.User
	for _, perm := range permissibles {
		if perm.PermissibleType == model.PermissibleTypeUser {
			user, err := s.userRepo.FindByID(ctx, perm.PermissibleID)
			if err != nil {
				continue // skip missing users
			}
			users = append(users, *user)
		}
	}
	return users, nil
}