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/*
 * Copyright 2023 Parsley Debug View Contributors 
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */
package parsley.debug

import io.circe.*
import io.circe.syntax.*

import parsley.debug.internal.CJson.*

/** A frontend that emits a JSON-format string representing the parse tree.
  *
  * Unlike most other frontends, this frontend will call a continuation that will have the JSON value passed into after
  * it has been produced by traversing the tree.
  *
  * This continuation must return unit, as there are not many other ways to make it useful other than making this
  * impure. It is recommended that if one wants to extract multiple inputs from the same frontend with the same
  * continuation, that it is recorded to some kind of list or iterable structure.
  *
  * It is recommended that all memory-heavy types (e.g. closures) are not stored explicitly. Consult the documentation
  * on attaching debuggers to find out how to prevent that.
  */
sealed class JsonFormatter private [debug] (cont: Output => Unit) extends DebugView.Reusable {
  override private [debug] def render(input: =>String, tree: =>DebugTree): Unit =
    cont(
      JsonObject(
        "input" -> input.toJSON,
        "parse" -> tree.toJSON
      ).asJson
    )
}

object JsonFormatter {
  def apply(cont: Output => Unit): JsonFormatter = new JsonFormatter(cont)
}

/** A version of [[JsonFormatter]] that emits a JSON string instead of a [[io.circe.Json]] object. */
final class JsonStringFormatter private [debug] (
  cont: String => Unit,
  pretty: Boolean,
  indent: Int,
  escapeUnicode: Boolean
) extends JsonFormatter(json => {
    val printer = if (pretty) {
      new Printer(
        indent = List.fill(indent)(' ').mkString(""), // .repeat() is not portable
        escapeNonAscii = escapeUnicode,
        dropNullValues = false,
        lbraceRight = "\n",
        rbraceLeft = "\n",
        lbracketRight = "\n",
        rbracketLeft = "\n",
        colonRight = " ",
        arrayCommaRight = "\n",
        objectCommaRight = "\n"
      )
    } else {
      new Printer(
        indent = List.fill(indent)(' ').mkString(""), // .repeat() is not portable
        escapeNonAscii = escapeUnicode,
        dropNullValues = false
      )
    }

    cont(json.printWith(printer))
  })

object JsonStringFormatter {
  def apply(
    cont: String => Unit,
    pretty: Boolean = true,
    indent: Int = 2,
    escapeUnicode: Boolean = false
  ): JsonStringFormatter =
    new JsonStringFormatter(cont, pretty, indent, escapeUnicode)
}