package jp.ymir.taskReporter.core
import scala.collection._
import scala.collection.immutable.StringLike
import scala.language.higherKinds
import scalaz._

object TSV {
  type Header = Seq[Symbol]
  type Field  = String
  type Record = Map[Symbol, Field]

  // ---
  type Failure[   F[_], R] = String => F[R]
  type Success[A, F[_], R] = A      => F[R]

  trait Parser[A] {
    def runParser[F[_], R](kf: Failure[F, R], ks: Success[A, F, R]): F[R]
  }

  implicit def ParserFunctor = new Functor[Parser] {
    def map[A, B](m: Parser[A])(f: A => B) = new Parser[B] {
      def runParser[F[_], R](kf: Failure[F, R], ks: Success[B, F, R]): F[R] = {
        def ks_(a: A) = ks(f(a))
        return m.runParser(kf, ks_)
      }
    }
  }

  implicit def ParserApplicative = new Applicative[Parser] {
    def point[A](a: => A) = new Parser[A] {
      def runParser[F[_], R](kf: Failure[F, R], ks: Success[A, F, R]): F[R] = ks(a)
    }

    def ap[A, B](m: => Parser[A])(fm: => Parser[A => B]) = new Parser[B] {
      def runParser[F[_], R](kf: Failure[F, R], ks: Success[B, F, R]): F[R] = {
        def ks_(f: A => B): F[R] = {
          def ks__(a: A) = ks(f(a))
          return m.runParser(kf, ks__)
        }
        return fm.runParser(kf, ks_)
      }
    }
  }

  implicit def ParserMonad = new Monad[Parser] {
    def point[A](a: => A) = implicitly[Applicative[Parser]].point(a)

    def bind[A, B](m: Parser[A])(f: A => Parser[B]) = new Parser[B] {
      def runParser[F[_], R](kf: Failure[F, R], ks: Success[B, F, R]): F[R] = {
        def ks_(a: A) = f(a).runParser(kf, ks)
        return m.runParser(kf, ks_)
      }
    }
  }

  def runParser[A](p: Parser[A]): Either[String, A] = {
    type F[A] = Either[String, A]
    def left (errMsg: String): F[A] = Left(errMsg)
    def right(x     : A     ): F[A] = Right(x)
    return p.runParser(left, right)
  }
  // ---

  def decode[A: FromRecord](tsv: StringLike[_]): Seq[A] = {
    val lines  = tsv.split('\n').filter(!_.isEmpty)
    val header = lines.head.split('\t').map(Symbol(_))
    val body   = lines.tail.map(line => (header zip line.split('\t')).toMap)
    return body.map(implicitly[FromRecord[A]].parseRecord)
  }

  trait FromRecord[A] {
    def parseRecord(r: Record): A
  }

  trait FromField[A] {
    def parseField(f: Field): A
  }
  def parseField[A: FromField](f: Field): A
    = implicitly[FromField[A]].parseField(f)

  trait ToRecord[A] {
    def toRecord(a: A): Record
  }

  trait ToField[A] {
    def toField(a: A): Field
  }

  // Option[A]
  implicit def OptionFromField[A: FromField] = new FromField[Option[A]] {
    def parseField(f: Field): Option[A] = {
      if (f.isEmpty) {
        return None
      }
      else {
        return Some(implicitly[FromField[A]].parseField(f))
      }
    }
  }

  // String
  implicit def StringFromField = new FromField[String] {
    def parseField(f: Field): String = f
  }

  // Int
  implicit def IntFromField = new FromField[Int] {
    def parseField(f: Field): Int = f.toInt
  }
}