import au.com.console.jpaspecificationdsl.*   // 1. Import Kotlin magic

////
// 2. Declare JPA Entities
@Entity
data class TvShow(
    @Id
    @GeneratedValue
    val id: Int = 0,
    val name: String = "",
    val synopsis: String = "",
    val availableOnNetflix: Boolean = false,
    val releaseDate: String? = null,
    @OneToMany(cascade = arrayOf(javax.persistence.CascadeType.ALL))
    val starRatings: Set<StarRating> = emptySet())

@Entity
data class StarRating(
    @Id
    @GeneratedValue
    val id: Int = 0,
    val stars: Int = 0)


////
// 3. Declare JPA Repository with JpaSpecificationExecutor
@Repository
interface TvShowRepository : CrudRepository<TvShow, Int>, JpaSpecificationExecutor<TvShow>


////
// 4. Kotlin Properties are now usable to create fluent specifications
@Service
class MyService @Inject constructor(val tvShowRepo: TvShowRepository) {
   fun findShowsReleasedIn2010NotOnNetflix(): List<TvShow> {
     return tvShowRepo.findAll(TvShow::availableOnNetflix.isFalse() and TvShow::releaseDate.equal("2010"))
   }

   /* Fall back to spring API with some extra helpers for more complex join queries */
   fun findShowsWithComplexQuery(): List<TvShow> {
       return tvShowRepo.findAll(where { equal(it.join(TvShow::starRatings).get(StarRating::stars), 2) })
   }
}

fun hasName(name: String?): Specification<TvShow>? = name?.let {
    TvShow::name.equal(it)
}

fun availableOnNetflix(available: Boolean?): Specification<TvShow>? = available?.let {
    TvShow::availableOnNetflix.equal(it)
}

fun hasReleaseDateIn(releaseDates: List<String>?): Specification<TvShow>? = releaseDates?.let {
    TvShow::releaseDate.`in`(releaseDates)
}

fun hasKeywordIn(keywords: List<String>?): Specification<TvShow>? = keywords?.let {
    or(keywords.map(::hasKeyword))
}

fun hasKeyword(keyword: String?): Specification<TvShow>? = keyword?.let {
    TvShow::synopsis.like("%$keyword%")
}

    val shows = tvShowRepo.findAll(
            or(
                    and(
                            availableOnNetflix(false),
                            hasKeywordIn(listOf("Jimmy"))
                    ),
                    and(
                            availableOnNetflix(true),
                            or(
                                    hasKeyword("killer"),
                                    hasKeyword("monster")
                            )
                    )
            )
    )

    /**
     * A TV show query DTO - typically used at the service layer.
     */
    data class TvShowQuery(
            val name: String? = null,
            val availableOnNetflix: Boolean? = null,
            val keywords: List<String> = listOf(),
            val releaseDates: List<String> = listOf()
    )

    /**
     * A single TvShowQuery is equivalent to an AND of all supplied criteria.
     * Note: any criteria that is null will be ignored (not included in the query).
     */
    fun TvShowQuery.toSpecification(): Specification<TvShow> = and(
            hasName(name),
            availableOnNetflix(availableOnNetflix),
            hasKeywordIn(keywords),
            hasReleaseDateIn(releaseDates)
    )

    val query = TvShowQuery(availableOnNetflix = false, keywords = listOf("Rick", "Jimmy"))
    val shows = tvShowRepo.findAll(query.toSpecification())

fun <T, R> KProperty1<T, R?>.equal(x: R): Specification<T> = spec { equal(it, x) }

private fun <T, R> KProperty1<T, R?>.spec(makePredicate: CriteriaBuilder.(path: Path<R>) -> Predicate): Specification<T> =
    this.let { property -> where { root -> makePredicate(root.get(property)) } }