package data

import (
    "encoding/json"
    "errors"
    "strconv"
)


// Default implementation of IRepository using an IDatastore.
type DefaultRepository[T IIdentifiable] struct {
    ds      IDatastore
    prefix  string
}

// TODO docstring
func NewDefaultRepository[T IIdentifiable](ds IDatastore, prefix string) *DefaultRepository[T] {
    return &DefaultRepository[T]{ ds: ds, prefix: prefix }
}

// Creates a new entry in the repository with the given object t. Throws an
// error if there already exists an entry with the same id, the json encoding
// fails or the connection to the IDatastore fails.
func (repo *DefaultRepository[T]) Create(t T) error {
    key := repo.prefix + ":" + strconv.FormatUint(uint64(t.Id()), 10)
    exists, err := repo.ds.KeyExists(key)
    if err != nil { return err }
    if exists { return errors.New("key already exits") }

    d, err := json.Marshal(t)
    if err != nil { return err }
    
    err = repo.ds.Set(key, string(d))
    if err != nil { return err }

    return nil
}

// Updates the entry with the same id as t in the repository with the values of
// t. Trows an error if the json encoding fails or the connection to the
// IDatastore fails.
func (repo *DefaultRepository[T]) Update(t T) error {
    key := repo.prefix + ":" + strconv.FormatUint(uint64(t.Id()), 10)
    exists, err := repo.ds.KeyExists(key)
    if err != nil { return err }
    if !exists { return errors.New("key does not exits") }

    d, err := json.Marshal(t)
    if err != nil { return err }
    
    err = repo.ds.Set(key, string(d))
    if err != nil { return err }

    return nil
}

func (repo *DefaultRepository[T]) Delete(t T) error {
    // TODO
    return nil
}

func (repo *DefaultRepository[T]) GetAll() ([]T, error) {
    // TODO
    return nil, nil
}

func (repo *DefaultRepository[T]) GetById(id uint) (T, error) {
    // TODO
    return *new(T), nil
}

func (repo *DefaultRepository[T]) GetByCriteria(c ISearchCriteria[T]) ([]T, error) {
    // TODO
    return nil, nil
}