package services

import (
	"FamilyHub/src/domain"
	"FamilyHub/src/repositories"
	"FamilyHub/src/utils"
	"context"
	"database/sql"
	"errors"
	"fmt"
	"log"
	"strings"
)

type TransactionService interface {
	Create(ctx context.Context, req domain.CreateTransactionRequest) (*domain.Transaction, error)
	GetByID(ctx context.Context, id int64) (*domain.Transaction, error)
	List(ctx context.Context, filter domain.TransactionListFilter) ([]*domain.Transaction, error)
	Analytics(ctx context.Context, filter domain.TransactionAnalyticsFilter) (domain.TransactionAnalytics, error)
	Update(ctx context.Context, id int64, req domain.UpdateTransactionRequest) (*domain.Transaction, error)
	Delete(ctx context.Context, id int64) error
}

type transactionService struct {
	repo         repositories.TransactionRepository
	activityRepo repositories.ActivityRepository
}

func NewTransactionService(repo repositories.TransactionRepository, activityRepo repositories.ActivityRepository) TransactionService {
	return &transactionService{repo: repo, activityRepo: activityRepo}
}

var (
	ErrTransactionNotFound  = errors.New("transaction not found")
	ErrTransactionPatch     = errors.New("empty update payload")
	ErrReceiptLinkConflict  = errors.New("receipt_id and detach_receipt cannot be used together")
	ErrReceiptAlreadyExists = errors.New("receipt already exists")
	ErrInvalidTransaction   = errors.New("type and category are required")
	ErrReceiptNotFound      = errors.New("receipt not found")
	ErrInvalidAnalytics     = errors.New("type must be income or expense")
)

func (s *transactionService) Create(ctx context.Context, req domain.CreateTransactionRequest) (*domain.Transaction, error) {
	log.Printf("transaction create request: payload=%s", utils.ToLogJSON(req))

	if strings.TrimSpace(req.Type) == "" || strings.TrimSpace(req.Category) == "" {
		log.Printf("transaction create failed: err=%v payload=%s", ErrInvalidTransaction, utils.ToLogJSON(req))
		return nil, ErrInvalidTransaction
	}

	transaction := &domain.Transaction{
		FamilyID:    req.FamilyID,
		Description: req.Description,
		Type:        req.Type,
		DateTime:    req.DateTime,
		Category:    req.Category,
		Amount:      req.Amount,
		CreatedBy:   req.CreatedBy,
		ReceiptID:   req.ReceiptID,
	}

	if err := s.repo.Create(ctx, transaction); err != nil {
		if errors.Is(err, repositories.ErrReceiptNotFound) {
			log.Printf("transaction create failed: err=%v payload=%s", ErrReceiptNotFound, utils.ToLogJSON(req))
			return nil, ErrReceiptNotFound
		}
		log.Printf("transaction create failed: err=%v payload=%s", err, utils.ToLogJSON(req))
		return nil, err
	}

	if s.activityRepo != nil {
		description := fmt.Sprintf("Created transaction %d", transaction.ID)
		_ = s.activityRepo.Create(ctx, &domain.ActivityLog{
			FamilyID:    &transaction.FamilyID,
			UserID:      transaction.CreatedBy,
			Action:      "create",
			EntityType:  "transaction",
			EntityID:    &transaction.ID,
			Description: description,
		})
	}

	log.Printf("transaction create response: payload=%s", utils.ToLogJSON(transaction))
	return transaction, nil
}

func (s *transactionService) GetByID(ctx context.Context, id int64) (*domain.Transaction, error) {
	transaction, err := s.repo.GetByID(ctx, id)
	if err != nil {
		return nil, err
	}
	if transaction == nil {
		return nil, ErrTransactionNotFound
	}

	return transaction, nil
}

func (s *transactionService) List(ctx context.Context, filter domain.TransactionListFilter) ([]*domain.Transaction, error) {
	if filter.Limit <= 0 {
		filter.Limit = 50
	}
	if filter.Limit > 200 {
		filter.Limit = 200
	}
	if filter.Offset < 0 {
		filter.Offset = 0
	}

	return s.repo.List(ctx, filter)
}

func (s *transactionService) Analytics(ctx context.Context, filter domain.TransactionAnalyticsFilter) (domain.TransactionAnalytics, error) {
	if filter.Type != nil {
		typeValue := strings.TrimSpace(*filter.Type)
		if typeValue != "income" && typeValue != "expense" {
			return domain.TransactionAnalytics{}, ErrInvalidAnalytics
		}
		filter.Type = &typeValue
	}

	return s.repo.Analytics(ctx, filter)
}

func (s *transactionService) Update(ctx context.Context, id int64, req domain.UpdateTransactionRequest) (*domain.Transaction, error) {
	if req.ReceiptID != nil && req.DetachReceipt {
		return nil, ErrReceiptLinkConflict
	}

	existing, err := s.repo.GetByID(ctx, id)
	if err != nil {
		return nil, err
	}
	if existing == nil {
		return nil, ErrTransactionNotFound
	}

	if req.Description == nil &&
		req.Type == nil &&
		req.DateTime == nil &&
		req.Category == nil &&
		req.Amount == nil &&
		req.ReceiptID == nil &&
		!req.DetachReceipt {
		return nil, ErrTransactionPatch
	}

	updated := &domain.Transaction{
		ID:          existing.ID,
		FamilyID:    existing.FamilyID,
		Description: existing.Description,
		Type:        existing.Type,
		DateTime:    existing.DateTime,
		Category:    existing.Category,
		Amount:      existing.Amount,
		CreatedAt:   existing.CreatedAt,
		CreatedBy:   existing.CreatedBy,
		ReceiptID:   existing.ReceiptID,
	}

	if req.Description != nil {
		updated.Description = req.Description
	}
	if req.Type != nil {
		updated.Type = *req.Type
	}
	if req.DateTime != nil {
		updated.DateTime = *req.DateTime
	}
	if req.Category != nil {
		updated.Category = *req.Category
	}
	if req.Amount != nil {
		updated.Amount = *req.Amount
	}

	syncReceipt := false
	if req.DetachReceipt {
		updated.ReceiptID = nil
		syncReceipt = true
	}
	if req.ReceiptID != nil {
		updated.ReceiptID = req.ReceiptID
		syncReceipt = true
	}

	if strings.TrimSpace(updated.Type) == "" || strings.TrimSpace(updated.Category) == "" {
		return nil, ErrInvalidTransaction
	}

	if err := s.repo.Update(ctx, updated, syncReceipt); err != nil {
		if errors.Is(err, repositories.ErrReceiptNotFound) {
			return nil, ErrReceiptNotFound
		}
		if errors.Is(err, sql.ErrNoRows) {
			return nil, ErrTransactionNotFound
		}
		return nil, err
	}

	return s.repo.GetByID(ctx, id)
}

func (s *transactionService) Delete(ctx context.Context, id int64) error {
	transaction, err := s.repo.GetByID(ctx, id)
	if err != nil {
		return err
	}
	if transaction == nil {
		return ErrTransactionNotFound
	}

	return s.repo.Delete(ctx, id)
}