package service

import (
	"fmt"
	"regexp"

	"spend-sparrow/db"
	"spend-sparrow/log"
	"spend-sparrow/types"

	"github.com/google/uuid"
	"github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/promauto"
)

var (
	safeInputRegex = regexp.MustCompile(`^[a-zA-Z0-9äöüß -]+$`)

	accountMetric = promauto.NewCounterVec(
		prometheus.CounterOpts{
			Name: "spendsparrow_account_total",
			Help: "The total of account operations",
		},
		[]string{"operation"},
	)
)

type Account interface {
	Add(user *types.User, name string) (*types.Account, error)
	Update(user *types.User, id uuid.UUID, name string) (*types.Account, error)
	Get(user *types.User, id uuid.UUID) (*types.Account, error)
	GetAll(user *types.User) ([]*types.Account, error)
	Delete(user *types.User, id uuid.UUID) error
}

type AccountImpl struct {
	db       db.Account
	clock    Clock
	random   Random
	settings *types.Settings
}

func NewAccountImpl(db db.Account, random Random, clock Clock, settings *types.Settings) Account {
	return AccountImpl{
		db:       db,
		clock:    clock,
		random:   NewRandomImpl(),
		settings: settings,
	}
}

func (s AccountImpl) Add(user *types.User, name string) (*types.Account, error) {
	accountMetric.WithLabelValues("add").Inc()

	if user == nil {
		return nil, ErrUnauthorized
	}

	newId, err := s.random.UUID()
	if err != nil {
		return nil, types.ErrInternal
	}

	err = s.validateAccount(name)
	if err != nil {
		return nil, err
	}

	account := &types.Account{
		Id:     newId,
		UserId: user.Id,

		Name: name,

		CurrentBalance:  0,
		LastTransaction: nil,
		OinkBalance:     0,

		CreatedAt: s.clock.Now(),
		CreatedBy: user.Id,
		UpdatedAt: nil,
		UpdatedBy: nil,
	}

	err = s.db.Insert(user.Id, account)
	if err != nil {
		return nil, types.ErrInternal
	}

	savedAccount, err := s.db.Get(user.Id, newId)
	if err != nil {
		log.Error("account %v not found after insert: %v", newId, err)
		return nil, types.ErrInternal
	}
	return savedAccount, nil
}

func (s AccountImpl) Update(user *types.User, id uuid.UUID, name string) (*types.Account, error) {
	accountMetric.WithLabelValues("update").Inc()
	if user == nil {
		return nil, ErrUnauthorized
	}
	err := s.validateAccount(name)
	if err != nil {
		return nil, err
	}

	account, err := s.db.Get(user.Id, id)
	if err != nil {
		if err == db.ErrNotFound {
			return nil, fmt.Errorf("account %v not found: %w", id, ErrBadRequest)
		}
		return nil, types.ErrInternal
	}

	timestamp := s.clock.Now()
	account.Name = name
	account.UpdatedAt = &timestamp
	account.UpdatedBy = &user.Id

	err = s.db.Update(user.Id, account)
	if err != nil {
		return nil, types.ErrInternal
	}

	return account, nil
}

func (s AccountImpl) Get(user *types.User, id uuid.UUID) (*types.Account, error) {
	accountMetric.WithLabelValues("get").Inc()

	if user == nil {
		return nil, ErrUnauthorized
	}

	account, err := s.db.Get(user.Id, id)
	if err != nil {
		if err == db.ErrNotFound {
			return nil, fmt.Errorf("account %v not found: %w", id, ErrBadRequest)
		}
		return nil, types.ErrInternal
	}

	return account, nil
}

func (s AccountImpl) GetAll(user *types.User) ([]*types.Account, error) {
	accountMetric.WithLabelValues("get_all").Inc()
	if user == nil {
		return nil, ErrUnauthorized
	}

	accounts, err := s.db.GetAll(user.Id)
	if err != nil {
		return nil, types.ErrInternal
	}

	return accounts, nil
}

func (s AccountImpl) Delete(user *types.User, id uuid.UUID) error {
	accountMetric.WithLabelValues("delete").Inc()
	if user == nil {
		return ErrUnauthorized
	}

	account, err := s.db.Get(user.Id, id)
	if err != nil {
		if err == db.ErrNotFound {
			return fmt.Errorf("account %v not found: %w", id, ErrBadRequest)
		}
		return types.ErrInternal
	}

	if account.UserId != user.Id {
		return types.ErrUnauthorized
	}

	err = s.db.Delete(user.Id, account.Id)
	if err != nil {
		return types.ErrInternal
	}

	return nil
}

func (s AccountImpl) validateAccount(name string) error {
	if name == "" {
		return fmt.Errorf("field \"name\" needs to be set: %w", ErrBadRequest)
	} else if !safeInputRegex.MatchString(name) {
		return fmt.Errorf("use only letters, dashes and spaces for \"name\": %w", ErrBadRequest)
	} else {
		return nil
	}
}