package scala.sys.process

import scala.annotation.tailrec

import collection.mutable.ListBuffer

import Character.isWhitespace

/** A simple enough command line parser using shell quote conventions.

*/

private final val SQ = '\''

private final val EOF = -1

/** Split the line into tokens separated by whitespace.

/** Split the line into tokens separated by whitespace or quotes.

*

* Tokens may be surrounded by quotes and may contain whitespace or escaped quotes.

*

* @return list of tokens

* @return either an error message or reverse list of tokens

*/

def tokenize(line: String, errorFn: String => Unit): List[String] = {

val accum = ListBuffer.empty[String]

val buf = new java.lang.StringBuilder

var pos = 0

import Character.isWhitespace

import java.lang.{StringBuilder => Builder}

import collection.mutable.ArrayBuffer

def cur: Int = if (done) EOF else line.charAt(pos)

def bump() = pos += 1

def put() = { buf.append(cur.toChar); bump() }

def done = pos >= line.length

var accum: List[String] = Nil

var pos = 0

var start = 0

val qpos = new ArrayBuffer[Int](16) // positions of paired quotes

def skipWhitespace() = while (isWhitespace(cur)) bump()

def cur: Int = if (done) EOF else line.charAt(pos)

def bump() = pos += 1

def done = pos >= line.length

// Collect to end of word, handling quotes. False for missing end quote.

def word(): Boolean = {

// Skip to the next quote as given.

def skipToQuote(q: Int): Boolean = {

var escaped = false

def terminal: Boolean = cur match {

case _ if escaped => escaped = false ; false

case '\\' => escaped = true ; false

case `q` | EOF => true

case _ => false

}

while (!terminal) bump()

!done

}

// Skip to a word boundary, where words can be quoted and quotes can be escaped

def skipToDelim(): Boolean = {

var escaped = false

var Q = EOF

var lastQ = 0

def inQuote = Q != EOF

def badquote() = errorFn(s"Unmatched quote [${lastQ}](${line.charAt(lastQ)})")

def finish(): Boolean = if (!inQuote) !escaped else { badquote(); false}

def quote() = { qpos += pos ; bump() }

@tailrec def advance(): Boolean = cur match {

case EOF => finish()

case _ if escaped => escaped = false; put(); advance()

case '\\' => escaped = true; bump(); advance()

case q if q == Q => Q = EOF; bump(); advance()

case q @ (DQ | SQ) if !inQuote => Q = q; lastQ = pos; bump(); advance()

case c if isWhitespace(c) && !inQuote => finish()

case _ => put(); advance()

case _ if escaped => escaped = false ; bump() ; advance()

case '\\' => escaped = true ; bump() ; advance()

case q @ (DQ | SQ) => { quote() ; skipToQuote(q) } && { quote() ; advance() }

case EOF => true

case c if isWhitespace(c) => true

case _ => bump(); advance()

}

advance()

}

def skipWhitespace() = while (isWhitespace(cur)) bump()

def copyText() = {

val buf = new Builder

var p = start

var i = 0

while (p < pos) {

if (i >= qpos.size) {

buf.append(line, p, pos)

p = pos

} else if (p == qpos(i)) {

buf.append(line, qpos(i)+1, qpos(i+1))

p = qpos(i+1)+1

i += 2

} else {

buf.append(line, p, qpos(i))

p = qpos(i)

}

}

buf.toString

}

def text() = {

val res = buf.toString

buf.setLength(0)

val res =

if (qpos.isEmpty) line.substring(start, pos)

else if (qpos(0) == start && qpos(1) == pos) line.substring(start+1, pos-1)

else copyText()

qpos.clear()

res

}

def badquote() = errorFn(s"Unmatched quote [${qpos.last}](${line.charAt(qpos.last)})")

@tailrec def loop(): List[String] = {

skipWhitespace()

if (done) accum.toList

else if (!word()) Nil

start = pos

if (done) accum.reverse

else if (!skipToDelim()) { badquote() ; Nil }

else {

accum += text()

accum ::= text()

loop()

}

}