org.ensime.sexp.SexpPrettyPrinter.scala Maven / Gradle / Ivy

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// Copyright: 2010 - 2018 https://github.com/ensime/ensime-server/graphs
// License: http://www.gnu.org/licenses/lgpl-3.0.en.html
package org.ensime.sexp

/**
 * The output is a non-standard interpretation of "pretty lisp" ---
 * emacs style formatting requires counting the length of the text on
 * the current line and indenting off that, which is not so easy when
 * all you have is a `StringBuilder`.
 */
trait SexpPrettyPrinter extends SexpPrinter {
  val Indent = 2

  def print(sexp: Sexp, sb: StringBuilder): Unit = print(sexp, sb, 0)

  private def print(sexp: Sexp, sb: StringBuilder, indent: Int): Unit =
    sexp match {
      case SexpData(data) => printData(data, sb, indent)
      case SexpList(els)  => printList(els, sb, indent)
      case SexpCons(x, y) => printCons(x, y, sb, indent)
      case atom: SexpAtom => printAtom(atom, sb)
    }

  protected def printCons(x: Sexp,
                          y: Sexp,
                          sb: StringBuilder,
                          indent: Int): Unit = {
    // recursive, could blow up for big trees
    sb.append('(')
    print(x, sb, indent)
    sb.append(" .\n")
    printIndent(sb, indent + Indent)
    print(y, sb, indent + Indent)
    sb.append(')')
  }

  protected def printData(data: Map[SexpSymbol, Sexp],
                          sb: StringBuilder,
                          indent: Int): Unit =
    if (data.isEmpty) print(SexpNil, sb)
    else {
      sb.append("(\n")
      printSeq(data, sb.append('\n')) { el =>
        printIndent(sb, indent + Indent)
        printSymbol(el._1.value, sb)
        sb.append(' ')
        print(el._2, sb, indent + Indent)
      }
      sb.append('\n')
      printIndent(sb, indent)
      sb.append(')')
    }

  protected def printList(els: List[Sexp],
                          sb: StringBuilder,
                          indent: Int): Unit =
    if (els.isEmpty) print(SexpNil, sb)
    else {
      sb.append('(')
      printSeq(els, { sb.append("\n"); printIndent(sb, indent + Indent) }) {
        print(_, sb, indent + Indent)
      }
      sb.append(')')
    }

  protected def printIndent(sb: StringBuilder, indent: Int): Unit =
    (0 until indent) foreach { _ =>
      sb.append(' ')
    }

}

object SexpPrettyPrinter extends SexpPrettyPrinter