package repository

import (
	"context"
	"errors"

	"gorm.io/gorm"

	"github.com/gochat/gochat/internal/model"
)

// ErrAlreadyMember indicates the user is already a member of the account.
var ErrAlreadyMember = errors.New("user is already a member of this account")

// AgentRepo implements GORM repository for Agent (AccountUser + User) operations.
// Reference: Chatwoot app/controllers/api/v1/accounts/agents_controller.rb
// In Chatwoot, an "agent" is a User who belongs to an Account via AccountUser.
// The agents controller returns User objects with their AccountUser association.
type AgentRepo struct {
	db *gorm.DB
}

// NewAgentRepo creates a new Agent repository.
func NewAgentRepo(db *gorm.DB) *AgentRepo {
	return &AgentRepo{db: db}
}

// AgentDetail represents an agent as returned by the API — User with their
// AccountUser role/availability for the specific account.
// Reference: Chatwoot renders User objects with included account_users.
type AgentDetail struct {
	model.User
	Role          string `json:"role"`
	Availability  string `json:"availability"`
	AutoOffline   bool   `json:"auto_offline"`
	InvitedBy     uint   `json:"invited_by"`
	AccountUserID uint   `json:"account_user_id"`
}

// ListByAccount retrieves all agents (users) for an account with pagination.
// Reference: Chatwoot agents_controller.rb#index → Current.account.users
// Returns User objects joined with their AccountUser association for the account.
func (r *AgentRepo) ListByAccount(ctx context.Context, accountID uint, offset, limit int) ([]AgentDetail, int64, error) {
	var count int64
	if err := r.db.WithContext(ctx).
		Model(&model.AccountUser{}).
		Where("account_id = ?", accountID).
		Count(&count).Error; err != nil {
		return nil, 0, err
	}

	var accountUsers []model.AccountUser
	if err := r.db.WithContext(ctx).
		Where("account_id = ?", accountID).
		Order("id ASC").
		Offset(offset).Limit(limit).
		Find(&accountUsers).Error; err != nil {
		return nil, 0, err
	}

	if len(accountUsers) == 0 {
		return []AgentDetail{}, count, nil
	}

	// Collect user IDs
	userIDs := make([]uint, len(accountUsers))
	auMap := make(map[uint]model.AccountUser) // userID → AccountUser
	for i, au := range accountUsers {
		userIDs[i] = au.UserID
		auMap[au.UserID] = au
	}

	// Fetch users
	var users []model.User
	if err := r.db.WithContext(ctx).
		Where("id IN ?", userIDs).
		Find(&users).Error; err != nil {
		return nil, 0, err
	}

	// Build AgentDetail list
	details := make([]AgentDetail, 0, len(users))
	for _, u := range users {
		au, ok := auMap[u.ID]
		if !ok {
			continue
		}
		d := AgentDetail{
			User:          u,
			Role:          au.Role,
			Availability:  au.Availability,
			AutoOffline:   au.AutoOffline,
			InvitedBy:     au.InvitedBy,
			AccountUserID: au.ID,
		}
		details = append(details, d)
	}

	return details, count, nil
}

// FindAgentByID retrieves a single agent (user) by ID scoped to an account.
// Reference: Chatwoot agents_controller.rb#fetch_agent → agents.find(params[:id])
func (r *AgentRepo) FindAgentByID(ctx context.Context, userID, accountID uint) (*AgentDetail, error) {
	var au model.AccountUser
	if err := r.db.WithContext(ctx).
		Where("account_id = ? AND user_id = ?", accountID, userID).
		First(&au).Error; err != nil {
		return nil, err
	}

	var user model.User
	if err := r.db.WithContext(ctx).First(&user, userID).Error; err != nil {
		return nil, err
	}

	return &AgentDetail{
		User:          user,
		Role:          au.Role,
		Availability:  au.Availability,
		AutoOffline:   au.AutoOffline,
		InvitedBy:     au.InvitedBy,
		AccountUserID: au.ID,
	}, nil
}

// CreateAgent adds a user to an account (creates AccountUser).
// Reference: Chatwoot agents_controller.rb#create → AgentBuilder.new.perform
// If the user does not exist, creates the user first, then creates the AccountUser.
func (r *AgentRepo) CreateAgent(ctx context.Context, accountID uint, inviterID uint, name, email, role, availability string, autoOffline bool) (*AgentDetail, error) {
	// Find or create the user
	var user model.User
	err := r.db.WithContext(ctx).Where("email = ?", email).First(&user).Error
	if err == gorm.ErrRecordNotFound {
		// Create new user
		user = model.User{
			Name:     name,
			Email:    email,
			Provider: "email",
			Active:   true,
		}
		if err := r.db.WithContext(ctx).Create(&user).Error; err != nil {
			return nil, err
		}
	} else if err != nil {
		return nil, err
	}

	// Check if AccountUser already exists
	var existingAU model.AccountUser
	err = r.db.WithContext(ctx).
		Where("account_id = ? AND user_id = ?", accountID, user.ID).
		First(&existingAU).Error
	if err == nil {
		// Already a member — return conflict error
		return nil, ErrAlreadyMember
	} else if err != gorm.ErrRecordNotFound {
		return nil, err
	}

	// Create AccountUser
	au := model.AccountUser{
		UserID:      user.ID,
		AccountID:   accountID,
		Role:        role,
		Availability: availability,
		AutoOffline: autoOffline,
		InvitedBy:   inviterID,
	}
	if err := r.db.WithContext(ctx).Create(&au).Error; err != nil {
		return nil, err
	}

	return &AgentDetail{
		User:          user,
		Role:          au.Role,
		Availability:  au.Availability,
		InvitedBy:     au.InvitedBy,
		AccountUserID: au.ID,
	}, nil
}

// UpdateAgent updates both the User (name) and AccountUser (role, availability, auto_offline).
// Reference: Chatwoot agents_controller.rb#update → agent.update!(name) + current_account_user.update!(role, availability, auto_offline)
func (r *AgentRepo) UpdateAgent(ctx context.Context, userID, accountID uint, name, role, availability string, autoOffline bool) (*AgentDetail, error) {
	// Update user name if provided
	if name != "" {
		if err := r.db.WithContext(ctx).
			Model(&model.User{}).
			Where("id = ?", userID).
			Update("name", name).Error; err != nil {
			return nil, err
		}
	}

	// Update AccountUser attributes
	updates := map[string]interface{}{}
	if role != "" {
		updates["role"] = role
	}
	if availability != "" {
		updates["availability"] = availability
	}
	// Chatwoot always sends auto_offline (even false) via .compact filter
	// so we always update it when the request includes it
	updates["auto_offline"] = autoOffline
	if len(updates) > 0 {
		if err := r.db.WithContext(ctx).
			Model(&model.AccountUser{}).
			Where("account_id = ? AND user_id = ?", accountID, userID).
			Updates(updates).Error; err != nil {
			return nil, err
		}
	}

	return r.FindAgentByID(ctx, userID, accountID)
}

// DeleteAgent removes the AccountUser association (removes agent from account).
// Reference: Chatwoot agents_controller.rb#destroy → current_account_user.destroy!
// If the user has no other account memberships, deletes the user record too.
func (r *AgentRepo) DeleteAgent(ctx context.Context, userID, accountID uint) error {
	// Delete the AccountUser
	if err := r.db.WithContext(ctx).
		Where("account_id = ? AND user_id = ?", accountID, userID).
		Delete(&model.AccountUser{}).Error; err != nil {
		return err
	}

	// Check if user still has other account memberships
	var remainingCount int64
	r.db.WithContext(ctx).
		Model(&model.AccountUser{}).
		Where("user_id = ?", userID).
		Count(&remainingCount)

	// If no remaining memberships, delete user record
	// Reference: Chatwoot agents_controller.rb#delete_user_record
	if remainingCount == 0 {
		if err := r.db.WithContext(ctx).Delete(&model.User{}, userID).Error; err != nil {
			return err
		}
	}

	return nil
}

// BulkCreateAgents adds multiple agents to an account by email.
// Reference: Chatwoot agents_controller.rb#bulk_create
// For each email: find or create user, then create AccountUser.
// Silently skips emails that fail (duplicate, invalid, etc.) — matches Chatwoot behavior.
func (r *AgentRepo) BulkCreateAgents(ctx context.Context, accountID uint, inviterID uint, emails []string) ([]AgentDetail, error) {
	results := make([]AgentDetail, 0, len(emails))

	for _, email := range emails {
		name := email // Default name to email; Chatwoot uses email.split('@').first
		atIdx := indexOfAt(email)
		if atIdx > 0 {
			name = email[:atIdx]
		}

		detail, err := r.CreateAgent(ctx, accountID, inviterID, name, email, "agent", "offline", false)
		if err != nil {
			// Silently skip — Chatwoot rescues ActiveRecord::RecordInvalid and logs
			continue
		}
		results = append(results, *detail)
	}

	return results, nil
}

// indexOfAt returns the index of '@' in the email string.
func indexOfAt(email string) int {
	for i, c := range email {
		if c == '@' {
			return i
		}
	}
	return -1
}

// CountByAccount returns the number of agents in an account.
func (r *AgentRepo) CountByAccount(ctx context.Context, accountID uint) (int64, error) {
	var count int64
	err := r.db.WithContext(ctx).
		Model(&model.AccountUser{}).
		Where("account_id = ?", accountID).
		Count(&count).Error
	return count, err
}