feat: loans

internal/service/loan.go

@@ -0,0 +1,195 @@
+package service
+
+import (
+	"fmt"
+	"time"
+
+	"git.juancwu.dev/juancwu/budgit/internal/model"
+	"git.juancwu.dev/juancwu/budgit/internal/repository"
+	"github.com/google/uuid"
+)
+
+type CreateLoanDTO struct {
+	SpaceID         string
+	UserID          string
+	Name            string
+	Description     string
+	OriginalAmount  int
+	InterestRateBps int
+	StartDate       time.Time
+	EndDate         *time.Time
+}
+
+type UpdateLoanDTO struct {
+	ID              string
+	Name            string
+	Description     string
+	OriginalAmount  int
+	InterestRateBps int
+	StartDate       time.Time
+	EndDate         *time.Time
+}
+
+const LoansPerPage = 25
+
+type LoanService struct {
+	loanRepo    repository.LoanRepository
+	receiptRepo repository.ReceiptRepository
+}
+
+func NewLoanService(loanRepo repository.LoanRepository, receiptRepo repository.ReceiptRepository) *LoanService {
+	return &LoanService{
+		loanRepo:    loanRepo,
+		receiptRepo: receiptRepo,
+	}
+}
+
+func (s *LoanService) CreateLoan(dto CreateLoanDTO) (*model.Loan, error) {
+	if dto.Name == "" {
+		return nil, fmt.Errorf("loan name cannot be empty")
+	}
+	if dto.OriginalAmount <= 0 {
+		return nil, fmt.Errorf("amount must be positive")
+	}
+
+	now := time.Now()
+	loan := &model.Loan{
+		ID:                  uuid.NewString(),
+		SpaceID:             dto.SpaceID,
+		Name:                dto.Name,
+		Description:         dto.Description,
+		OriginalAmountCents: dto.OriginalAmount,
+		InterestRateBps:     dto.InterestRateBps,
+		StartDate:           dto.StartDate,
+		EndDate:             dto.EndDate,
+		IsPaidOff:           false,
+		CreatedBy:           dto.UserID,
+		CreatedAt:           now,
+		UpdatedAt:           now,
+	}
+
+	if err := s.loanRepo.Create(loan); err != nil {
+		return nil, err
+	}
+	return loan, nil
+}
+
+func (s *LoanService) GetLoan(id string) (*model.Loan, error) {
+	return s.loanRepo.GetByID(id)
+}
+
+func (s *LoanService) GetLoanWithSummary(id string) (*model.LoanWithPaymentSummary, error) {
+	loan, err := s.loanRepo.GetByID(id)
+	if err != nil {
+		return nil, err
+	}
+
+	totalPaid, err := s.loanRepo.GetTotalPaidForLoan(id)
+	if err != nil {
+		return nil, err
+	}
+
+	receiptCount, err := s.loanRepo.GetReceiptCountForLoan(id)
+	if err != nil {
+		return nil, err
+	}
+
+	return &model.LoanWithPaymentSummary{
+		Loan:           *loan,
+		TotalPaidCents: totalPaid,
+		RemainingCents: loan.OriginalAmountCents - totalPaid,
+		ReceiptCount:   receiptCount,
+	}, nil
+}
+
+func (s *LoanService) GetLoansWithSummaryForSpace(spaceID string) ([]*model.LoanWithPaymentSummary, error) {
+	loans, err := s.loanRepo.GetBySpaceID(spaceID)
+	if err != nil {
+		return nil, err
+	}
+
+	return s.attachSummaries(loans)
+}
+
+func (s *LoanService) GetLoansWithSummaryForSpacePaginated(spaceID string, page int) ([]*model.LoanWithPaymentSummary, int, error) {
+	total, err := s.loanRepo.CountBySpaceID(spaceID)
+	if err != nil {
+		return nil, 0, err
+	}
+
+	totalPages := (total + LoansPerPage - 1) / LoansPerPage
+	if totalPages < 1 {
+		totalPages = 1
+	}
+	if page < 1 {
+		page = 1
+	}
+	if page > totalPages {
+		page = totalPages
+	}
+
+	offset := (page - 1) * LoansPerPage
+	loans, err := s.loanRepo.GetBySpaceIDPaginated(spaceID, LoansPerPage, offset)
+	if err != nil {
+		return nil, 0, err
+	}
+
+	result, err := s.attachSummaries(loans)
+	if err != nil {
+		return nil, 0, err
+	}
+
+	return result, totalPages, nil
+}
+
+func (s *LoanService) attachSummaries(loans []*model.Loan) ([]*model.LoanWithPaymentSummary, error) {
+	result := make([]*model.LoanWithPaymentSummary, len(loans))
+	for i, loan := range loans {
+		totalPaid, err := s.loanRepo.GetTotalPaidForLoan(loan.ID)
+		if err != nil {
+			return nil, err
+		}
+		receiptCount, err := s.loanRepo.GetReceiptCountForLoan(loan.ID)
+		if err != nil {
+			return nil, err
+		}
+		result[i] = &model.LoanWithPaymentSummary{
+			Loan:           *loan,
+			TotalPaidCents: totalPaid,
+			RemainingCents: loan.OriginalAmountCents - totalPaid,
+			ReceiptCount:   receiptCount,
+		}
+	}
+	return result, nil
+}
+
+func (s *LoanService) UpdateLoan(dto UpdateLoanDTO) (*model.Loan, error) {
+	if dto.Name == "" {
+		return nil, fmt.Errorf("loan name cannot be empty")
+	}
+	if dto.OriginalAmount <= 0 {
+		return nil, fmt.Errorf("amount must be positive")
+	}
+
+	existing, err := s.loanRepo.GetByID(dto.ID)
+	if err != nil {
+		return nil, err
+	}
+
+	existing.Name = dto.Name
+	existing.Description = dto.Description
+	existing.OriginalAmountCents = dto.OriginalAmount
+	existing.InterestRateBps = dto.InterestRateBps
+	existing.StartDate = dto.StartDate
+	existing.EndDate = dto.EndDate
+	existing.UpdatedAt = time.Now()
+
+	if err := s.loanRepo.Update(existing); err != nil {
+		return nil, err
+	}
+	return existing, nil
+}
+
+func (s *LoanService) DeleteLoan(id string) error {
+	return s.loanRepo.Delete(id)
+}