package auth

import (
	"context"
	"errors"

	"github.com/google/uuid"
	"github.com/jackc/pgx/v5"
)

var (
	ErrNotCompanyOwner     = errors.New("company owner required")
	ErrCannotRemoveOwner   = errors.New("transfer ownership before removing the company owner")
	ErrTransferSelf        = errors.New("user is already the company owner")
	ErrOwnerRequired       = errors.New("new owner must be an active company member")
)

// CompanyOwnerID returns the billing representative for the company, if set.
func (s *Service) CompanyOwnerID(ctx context.Context, companyID uuid.UUID) (uuid.UUID, bool, error) {
	var owner *uuid.UUID
	err := s.Pool.QueryRow(ctx, `SELECT owner_user_id FROM companies WHERE id = $1`, companyID).Scan(&owner)
	if errors.Is(err, pgx.ErrNoRows) {
		return uuid.Nil, false, ErrCompanyNotFound
	}
	if err != nil {
		return uuid.Nil, false, err
	}
	if owner == nil || *owner == uuid.Nil {
		return uuid.Nil, false, nil
	}
	return *owner, true, nil
}

// IsCompanyOwner reports whether userID is the company's owner_user_id.
func (s *Service) IsCompanyOwner(ctx context.Context, companyID, userID uuid.UUID) (bool, error) {
	ownerID, ok, err := s.CompanyOwnerID(ctx, companyID)
	if err != nil {
		return false, err
	}
	return ok && ownerID == userID, nil
}

// TransferOwnership sets a new company owner. The target must be an active member.
// The new owner is promoted to membership admin so they retain team powers.
func (s *Service) TransferOwnership(ctx context.Context, companyID, newOwnerID uuid.UUID) error {
	tx, err := s.Pool.Begin(ctx)
	if err != nil {
		return err
	}
	defer tx.Rollback(ctx)

	var current *uuid.UUID
	err = tx.QueryRow(ctx, `SELECT owner_user_id FROM companies WHERE id = $1 FOR UPDATE`, companyID).Scan(&current)
	if errors.Is(err, pgx.ErrNoRows) {
		return ErrCompanyNotFound
	}
	if err != nil {
		return err
	}
	if current != nil && *current == newOwnerID {
		return ErrTransferSelf
	}

	var status string
	err = tx.QueryRow(ctx, `
		SELECT status FROM memberships
		WHERE company_id = $1 AND user_id = $2`, companyID, newOwnerID).Scan(&status)
	if errors.Is(err, pgx.ErrNoRows) {
		return ErrOwnerRequired
	}
	if err != nil {
		return err
	}
	if status != "active" {
		return ErrOwnerRequired
	}

	_, err = tx.Exec(ctx, `
		UPDATE memberships
		SET role = 'admin', status = 'active', updated_at = now()
		WHERE company_id = $1 AND user_id = $2`, companyID, newOwnerID)
	if err != nil {
		return err
	}

	tag, err := tx.Exec(ctx, `
		UPDATE companies SET owner_user_id = $2, updated_at = now() WHERE id = $1`, companyID, newOwnerID)
	if err != nil {
		return err
	}
	if tag.RowsAffected() == 0 {
		return ErrCompanyNotFound
	}
	return tx.Commit(ctx)
}