package usecase

import (
	"context"
	"errors"

	"github.com/gofrs/uuid/v5"
)

// ErrInsufficientCredit is returned when order exceeds available credit
var ErrInsufficientCredit = errors.New("insufficient credit: order total exceeds available credit line")

// CheckCreditLine verifies if a company has enough credit to place an order
func (s *Service) CheckCreditLine(ctx context.Context, companyID uuid.UUID, orderTotalCents int64) (bool, error) {
	company, err := s.repo.GetCompany(ctx, companyID)
	if err != nil {
		return false, err
	}
	if company == nil {
		return false, errors.New("company not found")
	}

	// If no credit limit, credit line is not enabled
	if company.CreditLimitCents == 0 {
		return false, errors.New("credit line not enabled for this company")
	}

	availableCredit := company.CreditLimitCents - company.CreditUsedCents
	return orderTotalCents <= availableCredit, nil
}

// UseCreditLine reserves credit for an order (call during CreateOrder with payment_method=CREDIT_LINE)
func (s *Service) UseCreditLine(ctx context.Context, companyID uuid.UUID, amountCents int64) error {
	company, err := s.repo.GetCompany(ctx, companyID)
	if err != nil {
		return err
	}
	if company == nil {
		return errors.New("company not found")
	}

	availableCredit := company.CreditLimitCents - company.CreditUsedCents
	if amountCents > availableCredit {
		return ErrInsufficientCredit
	}

	// Update credit used
	company.CreditUsedCents += amountCents
	return s.repo.UpdateCompany(ctx, company)
}

// ReleaseCreditLine releases credit when order is paid or cancelled
func (s *Service) ReleaseCreditLine(ctx context.Context, companyID uuid.UUID, amountCents int64) error {
	company, err := s.repo.GetCompany(ctx, companyID)
	if err != nil {
		return err
	}
	if company == nil {
		return errors.New("company not found")
	}

	company.CreditUsedCents -= amountCents
	if company.CreditUsedCents < 0 {
		company.CreditUsedCents = 0
	}
	return s.repo.UpdateCompany(ctx, company)
}

// SetCreditLimit updates a company's credit limit (admin only)
func (s *Service) SetCreditLimit(ctx context.Context, companyID uuid.UUID, limitCents int64) error {
	company, err := s.repo.GetCompany(ctx, companyID)
	if err != nil {
		return err
	}
	if company == nil {
		return errors.New("company not found")
	}

	company.CreditLimitCents = limitCents
	return s.repo.UpdateCompany(ctx, company)
}