import scala.language.implicitConversions    

import scala.language.reflectiveCalls

import scala.annotation.tailrec   

import scala.io.Source

abstract class Rexp 

case object ZERO extends Rexp

case object ONE extends Rexp

case class CHARS(f: Char => Boolean) extends Rexp

case class ALT(r1: Rexp, r2: Rexp) extends Rexp 

case class SEQ(r1: Rexp, r2: Rexp) extends Rexp 

case class STAR(r: Rexp) extends Rexp 

case class RECD(x: String, r: Rexp) extends Rexp

case class PLUS(r: Rexp) extends Rexp

case class OPT(r: Rexp) extends Rexp

case class NTIMES(r: Rexp, n: Int) extends Rexp

abstract class Val

case object Empty extends Val

case class Chr(c: Char) extends Val

case class Sequ(v1: Val, v2: Val) extends Val

case class Left(v: Val) extends Val

case class Right(v: Val) extends Val

case class Stars(vs: List[Val]) extends Val

case class Rec(x: String, v: Val) extends Val

// some convenience for typing in regular expressions

def charlist2rexp(s : List[Char]): Rexp = s match {

  case Nil => ONE

  case c::Nil => CHARS(_ == c)

  case c::s => SEQ(CHARS(_ == c), charlist2rexp(s))

}

implicit def string2rexp(s : String) : Rexp = charlist2rexp(s.toList)

implicit def RexpOps(r: Rexp) = new {

  def | (s: Rexp) = ALT(r, s)

  def % = STAR(r)

  def ~ (s: Rexp) = SEQ(r, s)

}

implicit def stringOps(s: String) = new {

  def | (r: Rexp) = ALT(s, r)

  def | (r: String) = ALT(s, r)

  def % = STAR(s)

  def ~ (r: Rexp) = SEQ(s, r)

  def ~ (r: String) = SEQ(s, r)

  def $ (r: Rexp) = RECD(s, r)

}

def Alts(rs: List[Rexp]) : Rexp = rs match {

  case Nil => ZERO

  case r::Nil => r

  case r::rs => ALT(r, Alts(rs))

}

def ALTS(rs: Rexp*) = Alts(rs.toList)

def Seqs(rs: List[Rexp]) : Rexp = rs match {

  case Nil => ONE

  case r::Nil => r

  case r::rs => SEQ(r, Seqs(rs))

}

def SEQS(rs: Rexp*) = Seqs(rs.toList)

// nullable function: tests whether the regular 

// expression can recognise the empty string

def nullable (r: Rexp) : Boolean = r match {

  case ZERO => false

  case ONE => true

  case CHARS(_) => false

  case ALT(r1, r2) => nullable(r1) || nullable(r2)

  case SEQ(r1, r2) => nullable(r1) && nullable(r2)

  case STAR(_) => true

  case RECD(_, r1) => nullable(r1)

  case PLUS(r) => nullable(r)

  case OPT(_) => true

  case NTIMES(r, n) => if (n == 0) true else nullable(r)

}

// derivative of a regular expression w.r.t. a character

def der (c: Char, r: Rexp) : Rexp = r match {

  case ZERO => ZERO

  case ONE => ZERO

  case CHARS(f) => if (f(c)) ONE else ZERO

  case ALT(r1, r2) => ALT(der(c, r1), der(c, r2))

  case SEQ(r1, r2) => 

    if (nullable(r1)) ALT(SEQ(der(c, r1), r2), der(c, r2))

    else SEQ(der(c, r1), r2)

  case STAR(r) => SEQ(der(c, r), STAR(r))

  case RECD(_, r1) => der(c, r1)

  case PLUS(r) => SEQ(der(c, r), STAR(r))

  case OPT(r) => ALT(der(c, r), ZERO)

  case NTIMES(r, n) => if (n == 0) ZERO else SEQ(der(c, r), NTIMES(r, n - 1))

}

// derivative w.r.t. a string (iterates der)

@tailrec

def ders (s: List[Char], r: Rexp) : Rexp = s match {

  case Nil => r

  case c::s => ders(s, der(c, r))

}

// extracts a string from value

def flatten(v: Val) : String = v match {

  case Empty => ""

  case Chr(c) => c.toString

  case Left(v) => flatten(v)

  case Right(v) => flatten(v)

  case Sequ(v1, v2) => flatten(v1) + flatten(v2)

  case Stars(vs) => vs.map(flatten(_)).mkString

  case Rec(_, v) => flatten(v)

}

// extracts an environment from a value

def env(v: Val) : List[(String, String)] = v match {

  case Empty => Nil

  case Chr(c) => Nil

  case Left(v) => env(v)

  case Right(v) => env(v)

  case Sequ(v1, v2) => env(v1) ::: env(v2)

  case Stars(vs) => vs.flatMap(env)

  case Rec(x, v) => (x, flatten(v))::env(v)

}

// injection part

def mkeps(r: Rexp) : Val = r match {

  case ONE => Empty

  case ALT(r1, r2) => 

    if (nullable(r1)) Left(mkeps(r1)) else Right(mkeps(r2))

  case SEQ(r1, r2) => Sequ(mkeps(r1), mkeps(r2))

  case STAR(r) => Stars(Nil)

  case RECD(x, r) => Rec(x, mkeps(r))

  case PLUS(r) => Stars(List(mkeps(r)))

  case OPT(_) => Right(Empty)

  case NTIMES(r, n) => Stars(List.fill(n)(mkeps(r)))

}

def inj(r: Rexp, c: Char, v: Val) : Val = (r, v) match {

  case (STAR(r), Sequ(v1, Stars(vs))) => Stars(inj(r, c, v1)::vs)

  case (SEQ(r1, r2), Sequ(v1, v2)) => Sequ(inj(r1, c, v1), v2)

  case (SEQ(r1, r2), Left(Sequ(v1, v2))) => Sequ(inj(r1, c, v1), v2)

  case (SEQ(r1, r2), Right(v2)) => Sequ(mkeps(r1), inj(r2, c, v2))

  case (ALT(r1, r2), Left(v1)) => Left(inj(r1, c, v1))

  case (ALT(r1, r2), Right(v2)) => Right(inj(r2, c, v2))

  case (CHARS(_), Empty) => Chr(c) 

  case (RECD(x, r1), _) => Rec(x, inj(r1, c, v))

  case (PLUS(r), Sequ(v1, Stars(vs))) => Stars(inj(r, c, v1)::vs)

  case (OPT(r), Left(v1)) => Left(inj(r, c, v1))

  case (NTIMES(r, n), Sequ(v1, Stars(vs))) => Stars(inj(r, c, v1)::vs)

}

// main unsimplified lexing function (produces a value)

def lex(r: Rexp, s: List[Char]) : Val = s match {

  case Nil => if (nullable(r)) mkeps(r) else throw new Exception("Not matched")

  case c::cs => inj(r, c, lex(der(c, r), cs))

}

def lexing(r: Rexp, s: String) : Try[Val] = Try(lex(r, s.toList))

// some "rectification" functions for simplification

def F_ID(v: Val): Val = v

def F_RIGHT(f: Val => Val) = (v:Val) => Right(f(v))

def F_LEFT(f: Val => Val) = (v:Val) => Left(f(v))

def F_ALT(f1: Val => Val, f2: Val => Val) = (v:Val) => v match {

  case Right(v) => Right(f2(v))

  case Left(v) => Left(f1(v))

}

def F_SEQ(f1: Val => Val, f2: Val => Val) = (v:Val) => v match {

  case Sequ(v1, v2) => Sequ(f1(v1), f2(v2))

}

def F_SEQ_Empty1(f1: Val => Val, f2: Val => Val) = (v:Val) => Sequ(f1(Empty), f2(v))

def F_SEQ_Empty2(f1: Val => Val, f2: Val => Val) = (v:Val) => Sequ(f1(v), f2(Empty))

def F_RECD(f: Val => Val) = (v:Val) => v match {

  case Rec(x, v) => Rec(x, f(v))

}

def F_ERROR(v: Val): Val = throw new Exception("error")

// simplification of regular expressions returning also an

// rectification function; no simplification under STAR 

def simp(r: Rexp): (Rexp, Val => Val) = r match {

  case ALT(r1, r2) => {

    val (r1s, f1s) = simp(r1)

    val (r2s, f2s) = simp(r2)

    (r1s, r2s) match {

      case (ZERO, _) => (r2s, F_RIGHT(f2s))

      case (_, ZERO) => (r1s, F_LEFT(f1s))

      case _ => if (r1s == r2s) (r1s, F_LEFT(f1s))

                else (ALT (r1s, r2s), F_ALT(f1s, f2s)) 

    }

  }

  case SEQ(r1, r2) => {

    val (r1s, f1s) = simp(r1)

    val (r2s, f2s) = simp(r2)

    (r1s, r2s) match {

      case (ZERO, _) => (ZERO, F_ERROR)

      case (_, ZERO) => (ZERO, F_ERROR)

      case (ONE, _) => (r2s, F_SEQ_Empty1(f1s, f2s))

      case (_, ONE) => (r1s, F_SEQ_Empty2(f1s, f2s))

      case _ => (SEQ(r1s,r2s), F_SEQ(f1s, f2s))

    }

  }

  case RECD(x, r1) => {

    val (r1s, f1s) = simp(r1)

    (RECD(x, r1s), F_RECD(f1s))

  }

  case r => (r, F_ID)

}

def lex_simp(r: Rexp, s: List[Char]) : Val = s match {

  case Nil => if (nullable(r)) mkeps(r) else throw new Exception("Not matched")

  case c::cs => {

    val (r_simp, f_simp) = simp(der(c, r))

    inj(r, c, f_simp(lex_simp(r_simp, cs)))

  }

}

// Some Tests

//============

def time_needed[T](i: Int, code: => T) = {

  val start = System.nanoTime()

  for (j <- 1 to i) code

  val end = System.nanoTime()

  (end - start)/(i * 1.0e9)

}

val r0 = ("a" | "ab") ~ ("b" | "")

println(lexing(r0, "ab"))

println(lexing_simp(r0, "ab"))

val r1 = ("a" | "ab") ~ ("bcd" | "cd")

println(lexing_simp(r1, "abcd"))

println(lexing_simp((("" | "a") ~ ("ab" | "b")), "ab"))

println(lexing_simp((("" | "a") ~ ("b" | "ab")), "ab"))

println(lexing_simp((("" | "a") ~ ("c" | "ab")), "ab"))

// Some more Tests

//=================

val ALL = CHARS((c) => true)

val reg = ALL.% ~ "a" ~ NTIMES(ALL, 3) ~ "bc"

// Two Simple Tests for the While Language

//========================================

// Lexing Rules 

val SYM = CHARS ("abcdefghijklmnopqrstuvwxyz" contains _)

val DIGIT = CHARS("0123456789" contains _)

val ID = SYM ~ (SYM | DIGIT).% 

val NUM = PLUS(DIGIT)

val KEYWORD : Rexp = "skip" | "while" | "do" | "if" | "then" | "else" | "read" | "write" | "true" | "false"

val SEMI: Rexp = ";"

val OP: Rexp = ":=" | "==" | "-" | "+" | "*" | "!=" | "<" | ">" | "<=" | ">=" | "%" | "/"

val WHITESPACE = PLUS(" " | "\n" | "\t")

val RPAREN: Rexp = ")"

val LPAREN: Rexp = "("

val BEGIN: Rexp = "{"

val END: Rexp = "}"

val STRING: Rexp = "\"" ~ SYM.% ~ "\""

val WHILE_REGS = (("k" $ KEYWORD) | 

                  ("i" $ ID) | 

                  ("o" $ OP) | 

                  ("n" $ NUM) | 

                  ("s" $ SEMI) | 

                  ("str" $ STRING) |

                  ("p" $ (LPAREN | RPAREN)) | 

                  ("b" $ (BEGIN | END)) | 

                  ("w" $ WHITESPACE)).%

/*

val WHILE_REGS = (KEYWORD | 

                  ID | 

                  OP | 

                  NUM | 

                  SEMI | 

                  LPAREN | RPAREN | 

                  BEGIN | END | 

                  WHITESPACE).%

*/

println("prog0 test")

val prog0 = """read n"""

println("prog1 test")

val prog1 = """read  n; write (n)"""

// Bigger Test

//=============

val prog2 = """

i := 2;

max := 100;

while i < max do {

  isprime := 1;

  j := 2;

  while (j * j) <= i + 1  do {

    if i % j == 0 then isprime := 0  else skip;

    j := j + 1

  };

  if isprime == 1 then write i else skip;

  i := i + 1

}"""

println("prog2 test - tokens")

val prog3 = """

write "fib";

read n;

minus1 := 0;

minus2 := 1;

while n > 0 do {

  temp := minus2;

  minus2 := minus1 + minus2;

  minus1 := temp;

  n := n - 1

};

write "result";

write minus2

"""

println("prog3 test - tokens")

// Sulzmann's tests

//==================

val sulzmann = ("a" | "b" | "ab").%

println(lexing_simp(sulzmann, "a" * 10))

for (i <- 1 to 4501 by 500) {

  println(i + ": " + "%.5f".format(time_needed(1, lexing_simp(sulzmann, "a" * i))))

}

for (i <- 1 to 2001 by 500) {

  println(i + ": " + "%.5f".format(time_needed(1, lexing_simp(sulzmann, "ab" * i))))

}

// first benchmark regex 

//=======================

val reWord = CHARS("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789" contains _)

val reWordStar = STAR(reWord)

val optionSet1 = "-" | "+" | "."

val optionSet2 = "-" | "."

val atTheRate = "@"

val period = "."

val optionSet3 = "," | ";"

val whitespace = " "

val re01 = reWordPlus

val re02 = STAR(optionSet1 ~ reWordPlus)

val re03 = atTheRate

val re04 = reWordPlus

val re05 = STAR(optionSet2 ~ reWordPlus)

val re06 = period

val re07 = reWordPlus

val re08 = re05

val re09 = optionSet3

val re10 = STAR(whitespace)

val re11 = reWordPlus

val re12 = re02

val re13 = atTheRate

val re14 = reWordPlus

val re15 = re05

val re16 = period

val re17 = reWordPlus

val re18 = re05

val re01_08 = SEQS(re01, re02, re03, re04, re05, re06, re07, re08)

val re09_10 = re09 ~ re10

val re11_18 = re01_08

val re = re01_08 ~ STAR(re09_10 ~ re11_18)

def process(s: String, i: Int) : Unit = {

  println(i + " " + "%.5f".format(time_needed(1, lexing(re, s))))

}

val filename = "../tests/emails.txt"

val filelines = Source.fromFile(filename).getLines.take(76).zipWithIndex

filelines.foreach({ case (s: String, i: Int) => process(s, i) })