package wow.doge.http4sdemo.services

import io.circe.generic.semiauto._
import monix.bio.IO
import monix.bio.Task
import monix.bio.UIO
import monix.reactive.Observable
import slick.jdbc.JdbcBackend
import slick.jdbc.JdbcProfile
import wow.doge.http4sdemo.dto.Author
import wow.doge.http4sdemo.dto.Book
import wow.doge.http4sdemo.dto.BookSearchMode
import wow.doge.http4sdemo.dto.BookSearchMode.AuthorName
import wow.doge.http4sdemo.dto.BookSearchMode.BookTitle
import wow.doge.http4sdemo.dto.BookUpdate
import wow.doge.http4sdemo.dto.NewAuthor
import wow.doge.http4sdemo.dto.NewBook
import wow.doge.http4sdemo.implicits._
import wow.doge.http4sdemo.slickcodegen.Tables

object LibraryService {
  sealed trait Error extends Exception {
    def message: String
    override def getMessage(): String = message
  }
  final case class EntityDoesNotExist(message: String) extends Error
  final case class EntityAlreadyExists(message: String) extends Error
  // final case class MyError2(message: String) extends Error
  // case object C3 extends Error { val message: String = "C3" }

  object Error {
    implicit val codec = deriveCodec[Error]
  }
}

trait LibraryService {

  import LibraryService._

  def getBooks: Observable[Book]

  def getBookById(id: Int): Task[Option[Book]]

  def searchBook(mode: BookSearchMode, value: String): Observable[Book]

  def updateBook(id: Int, updateData: BookUpdate): IO[Error, Unit]

  def deleteBook(id: Int): Task[Int]

  def insertBook(newBook: NewBook): IO[Error, Book]

  def insertAuthor(a: NewAuthor): Task[Int]

  def booksForAuthor(authorId: Int): Observable[Book]

}

class LibraryServiceImpl(
    profile: JdbcProfile,
    dbio: LibraryDbio,
    db: JdbcBackend.DatabaseDef
) extends LibraryService {
  import profile.api._

  import LibraryService._

  def getBooks = db.streamO(dbio.getBooks.transactionally)

  def getBookById(id: Int) = db.runL(dbio.getBook(id))

  def searchBook(mode: BookSearchMode, value: String): Observable[Book] =
    mode match {
      case BookTitle =>
        db.streamO(dbio.getBooksByTitle(value))

      case AuthorName =>
        Observable
          .fromTask((for {
            _ <- IO.unit
            id <- IO(value.toInt)
            author <- db.runL(dbio.getAuthor(id)).flatMap {
              case None =>
                IO.raiseError(
                  new EntityDoesNotExist(s"Author with id=$id does not exist")
                )
              case Some(value) => IO.pure(value)
            }
            books = db
              .streamO(dbio.getBooksForAuthor(id))
              .map(Book.fromBooksRow)
          } yield books).toTask)
          .flatten

    }

  def insertAuthor(a: NewAuthor): Task[Int] = db.runL(dbio.insertAuthor(a))

  def updateBook(id: Int, updateData: BookUpdate): IO[Error, Unit] =
    for {
      action <- UIO.deferAction(implicit s =>
        UIO(for {
          mbRow <- dbio.selectBook(id).result.headOption
          updatedRow <- mbRow match {
            case Some(value) =>
              println(s"Original value -> $value")
              println(s"Value to be updated with -> $updateData")
              DBIO.successful(updateData.update(value))
            case None =>
              DBIO.failed(
                EntityDoesNotExist(s"Book with id=$id does not exist")
              )
          }
          updateAction = dbio.selectBook(id).update(updatedRow)
          _ = println(s"SQL = ${updateAction.statements}")
          _ <- updateAction
        } yield ())
      )
      _ <- db
        .runTryL(action.transactionally.asTry)
        .mapErrorPartial { case e: Error =>
          e
        }
    } yield ()

  def deleteBook(id: Int) = db.runL(dbio.deleteBook(id))

  def insertBook(newBook: NewBook): IO[Error, Book] =
    IO.deferAction { implicit s =>
      for {
        action <- UIO(for {
          _ <- dbio
            .selectBookByIsbn(newBook.isbn)
            .map(Book.fromBooksTableFn)
            .result
            .headOption
            .flatMap {
              case None => DBIO.successful(())
              case Some(_) =>
                DBIO.failed(
                  EntityAlreadyExists(
                    s"Book with isbn=${newBook.isbn} already exists"
                  )
                )
            }
          _ <- dbio.getAuthor(newBook.authorId).flatMap {
            case None =>
              DBIO.failed(
                EntityDoesNotExist(
                  s"Author with id=${newBook.authorId} does not exist"
                )
              )
            case Some(_) => DBIO.successful(())
          }
          book <- dbio.insertBookAndGetBook(newBook)
        } yield book)
        book <- db
          .runTryL(action.transactionally.asTry)
          .mapErrorPartial { case e: Error =>
            e
          }
      } yield book
    }

  def booksForAuthor(authorId: Int) =
    db.streamO(dbio.getBooksForAuthor(authorId).transactionally)
      .map(Book.fromBooksRow)

}

class LibraryDbio(val profile: JdbcProfile) {
  import profile.api._

  /*  */

  def getBooks: StreamingDBIO[Seq[Book], Book] = Query.getBooksInner.result

  def insertBookAndGetId(newBook: NewBook): DBIO[Int] =
    Query.insertBookGetId += newBook

  def insertBookAndGetBook(newBook: NewBook): DBIO[Book] =
    Query.insertBookGetBook += newBook

  def insertAuthor(newAuthor: NewAuthor): DBIO[Int] =
    Query.insertAuthorGetId += newAuthor

  def selectBook(id: Int) = Tables.Books.filter(_.bookId === id)

  def getAuthor(id: Int) =
    Query.selectAuthor(id).map(Author.fromAuthorsTableFn).result.headOption

  def deleteBook(id: Int) = selectBook(id).delete

  def getBook(id: Int) = selectBook(id)
    .map(Book.fromBooksTableFn)
    .result
    .headOption

  def selectBookByIsbn(isbn: String) = Tables.Books.filter(_.isbn === isbn)

  def getBooksByTitle(title: String) =
    Tables.Books.filter(_.bookTitle === title).map(Book.fromBooksTableFn).result

  def getBooksForAuthor(authorId: Int) =
    Query.booksForAuthorInner(authorId).result

  private object Query {

    val getBooksInner = Book.fromBooksTable

    val insertBookGetId =
      NewBook.fromBooksTable.returning(Tables.Books.map(_.bookId))

    val insertBookGetBook = NewBook.fromBooksTable.returning(getBooksInner)

    val insertAuthorGetId =
      Tables.Authors
        .map(a => (a.authorName).mapTo[NewAuthor])
        .returning(Tables.Authors.map(_.authorId))

    // val insertAuthor = NewAuthor.fromAuthorsTable

    def booksForAuthorInner(authorId: Int) = for {
      b <- Tables.Books
      a <- Tables.Authors
      if b.authorId === a.authorId && b.authorId === authorId
    } yield b

    def selectAuthor(authorId: Int) =
      Tables.Authors.filter(_.authorId === authorId)
  }
}

trait NoopLibraryService extends LibraryService {
  def getBooks: Observable[Book] =
    Observable.raiseError(new NotImplementedError)

  def getBookById(id: Int): Task[Option[Book]] =
    IO.terminate(new NotImplementedError)

  def searchBook(
      mode: BookSearchMode,
      value: String
  ): Observable[Book] = Observable.raiseError(new NotImplementedError)

  def updateBook(
      id: Int,
      updateData: BookUpdate
  ): IO[LibraryService.Error, Unit] = IO.terminate(new NotImplementedError)

  def deleteBook(id: Int): Task[Int] = IO.terminate(new NotImplementedError)

  def insertBook(newBook: NewBook): IO[LibraryService.Error, Book] =
    IO.terminate(new NotImplementedError)

  def insertAuthor(a: NewAuthor): Task[Int] =
    IO.terminate(new NotImplementedError)

  def booksForAuthor(authorId: Int): Observable[Book] =
    Observable.raiseError(new NotImplementedError)

}