ndeg.fetch-debug_2.10.0.5.0.source-code.document.scala Maven / Gradle / Ivy

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Simple & Efficient data access for Scala and Scala.js
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/*
 * Copyright 2016 47 Degrees, LLC. 
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package fetch.document

import java.io.Writer

case object DocNil                             extends Document
case object DocBreak                           extends Document
case class DocText(txt: String)                extends Document
case class DocGroup(doc: Document)             extends Document
case class DocNest(indent: Int, doc: Document) extends Document
case class DocCons(hd: Document, tl: Document) extends Document

/**
  * A basic pretty-printing library, based on Lindig's strict version
  * of Wadler's adaptation of Hughes' pretty-printer.
  *
  * @author Michel Schinz
  * @version 1.0
  */
abstract class Document {
  def ::(hd: Document): Document  = DocCons(hd, this)
  def ::(hd: String): Document    = DocCons(DocText(hd), this)
  def :/:(hd: Document): Document = hd :: DocBreak :: this
  def :/:(hd: String): Document   = hd :: DocBreak :: this

  /**
    * Format this document on `writer` and try to set line
    * breaks so that the result fits in `width` columns.
    */
  def format(width: Int, writer: Writer) {
    type FmtState = (Int, Boolean, Document)

    def fits(w: Int, state: List[FmtState]): Boolean = state match {
      case _ if w < 0 =>
        false
      case List() =>
        true
      case (_, _, DocNil) :: z =>
        fits(w, z)
      case (i, b, DocCons(h, t)) :: z =>
        fits(w, (i, b, h) :: (i, b, t) :: z)
      case (_, _, DocText(t)) :: z =>
        fits(w - t.length(), z)
      case (i, b, DocNest(ii, d)) :: z =>
        fits(w, (i + ii, b, d) :: z)
      case (_, false, DocBreak) :: z =>
        fits(w - 1, z)
      case (_, true, DocBreak) :: z =>
        true
      case (i, _, DocGroup(d)) :: z =>
        fits(w, (i, false, d) :: z)
    }

    def spaces(n: Int) {
      var rem = n
      while (rem >= 16) { writer write "                "; rem -= 16 }
      if (rem >= 8) { writer write "        "; rem -= 8 }
      if (rem >= 4) { writer write "    "; rem -= 4 }
      if (rem >= 2) { writer write "  "; rem -= 2 }
      if (rem == 1) { writer write " " }
    }

    def fmt(k: Int, state: List[FmtState]): Unit = state match {
      case List() => ()
      case (_, _, DocNil) :: z =>
        fmt(k, z)
      case (i, b, DocCons(h, t)) :: z =>
        fmt(k, (i, b, h) :: (i, b, t) :: z)
      case (i, _, DocText(t)) :: z =>
        writer write t
        fmt(k + t.length(), z)
      case (i, b, DocNest(ii, d)) :: z =>
        fmt(k, (i + ii, b, d) :: z)
      case (i, true, DocBreak) :: z =>
        writer write "\n"
        spaces(i)
        fmt(i, z)
      case (i, false, DocBreak) :: z =>
        writer write " "
        fmt(k + 1, z)
      case (i, b, DocGroup(d)) :: z =>
        val fitsFlat = fits(width - k, (i, false, d) :: z)
        fmt(k, (i, !fitsFlat, d) :: z)
      case _ =>
        ()
    }

    fmt(0, (0, false, DocGroup(this)) :: Nil)
  }
}

object Document {

  /** The empty document */
  def empty = DocNil

  /** A break, which will either be turned into a space or a line break */
  def break = DocBreak

  /** A document consisting of some text literal */
  def text(s: String): Document = DocText(s)

  /**
    * A group, whose components will either be printed with all breaks
    * rendered as spaces, or with all breaks rendered as line breaks.
    */
  def group(d: Document): Document = DocGroup(d)

  /** A nested document, which will be indented as specified. */
  def nest(i: Int, d: Document): Document = DocNest(i, d)
}