# SPDX-FileCopyrightText: ☭ Emery Hemingway
# SPDX-License-Identifier: Unlicense

import std/[base64, json, options, sets, sequtils, streams, strutils, tables, typetraits]
import ./values

proc `$`*(s: Symbol): string =
  let sym = string s
  if sym.len > 0 and sym[0] in {'A'..'z'} and not sym.anyIt(char(it) in { '\x00'..'\x19', '"', '\\', '|' }):
    result = sym
  else:
    result = newStringOfCap(sym.len shl 1)
    result.add('|')
    for c in sym:
      case c
      of '\\':
        result.add("\\\\")
      of '/':
        result.add("\\/")
      of '\x08':
        result.add("\\b")
      of '\x0c':
        result.add("\\f")
      of '\x0a':
        result.add("\\n")
      of '\x0d':
        result.add("\\r")
      of '\x09':
        result.add("\\t")
      of '|':
        result.add("\\|")
      else:
        result.add(c)
    result.add('|')

type TextMode* = enum textPreserves, textJson

proc writeText*[E](stream: Stream; pr: Preserve[E]; mode = textPreserves) =
  ## Encode Preserves to a `Stream` as text.
  if pr.embedded: write(stream, "#!")
  case pr.kind:
  of pkBoolean:
    case pr.bool
    of false: write(stream, "#f")
    of true: write(stream, "#t")
  of pkFloat:
    write(stream, $pr.float)
    write(stream, 'f')
  of pkDouble:
    write(stream, $pr.double)
  of pkRegister:
    write(stream, $pr.register)
  of pkBigInt:
    write(stream, $pr.bigint)
  of pkString:
    write(stream, escapeJson(pr.string))
  of pkByteString:
    if pr.bytes.allIt(char(it) in {' '..'!', '#'..'~'}):
      write(stream, "#\"")
      write(stream, cast[string](pr.bytes))
      write(stream, '"')
    else:
      if pr.bytes.len > 64:
        write(stream, "#[") #]#
        write(stream, base64.encode(pr.bytes))
        write(stream, ']')
      else:
        const alphabet = "0123456789abcdef"
        write(stream, "#x\"")
        for b in pr.bytes:
          write(stream, alphabet[int(b shr 4)])
          write(stream, alphabet[int(b and 0xf)])
        write(stream, '"')
  of pkSymbol:
    let sym = pr.symbol.string
    if sym.len > 0 and sym[0] in {'A'..'z'} and not sym.anyIt(char(it) in { '\x00'..'\x19', '"', '\\', '|' }):
      write(stream, sym)
    else:
      write(stream, '|')
      for c in sym:
        case c
        of '\\':
          write(stream, "\\\\")
        of '/':
          write(stream, "\\/")
        of '\x08':
          write(stream, "\\b")
        of '\x0c':
          write(stream, "\\f")
        of '\x0a':
          write(stream, "\\n")
        of '\x0d':
          write(stream, "\\r")
        of '\x09':
          write(stream, "\\t")
        of '|':
          write(stream, "\\|")
        else:
          write(stream, c)
      write(stream, '|')
  of pkRecord:
    assert(pr.record.len > 0)
    write(stream, '<')
    writeText(stream, pr.record[pr.record.high], mode)
    for i in 0..<pr.record.high:
      write(stream, ' ')
      writeText(stream, pr.record[i], mode)
    write(stream, '>')
  of pkSequence:
    write(stream, '[')
    var insertSeperator: bool
    case mode
    of textPreserves:
      for val in pr.sequence:
        if insertSeperator: write(stream, ' ')
        else: insertSeperator = true
        writeText(stream, val, mode)
    of textJson:
      for val in pr.sequence:
        if insertSeperator: write(stream, ',')
        else: insertSeperator = true
        writeText(stream, val, mode)
    write(stream, ']')
  of pkSet:
    write(stream, "#{")
    var insertSeperator: bool
    for val in pr.set.items:
      if insertSeperator: write(stream, ' ')
      else: insertSeperator = true
      writeText(stream, val, mode)
    write(stream, '}')
  of pkDictionary:
    write(stream, '{')
    var insertSeperator: bool
    case mode
    of textPreserves:
      for (key, value) in pr.dict.items:
        if insertSeperator: write(stream, ' ')
        else: insertSeperator = true
        writeText(stream, key, mode)
        write(stream, ": ")
        writeText(stream, value, mode)
    of textJson:
      for (key, value) in pr.dict.items:
        if insertSeperator: write(stream, ',')
        else: insertSeperator = true
        writeText(stream, key, mode)
        write(stream, ':')
        writeText(stream, value, mode)
    write(stream, '}')
  of pkEmbedded:
    write(stream, "#!")
    when compiles($pr.embed) and not E is void:
      write(stream, $pr.embed)
    else:
      write(stream, "…")

proc `$`*[E](pr: Preserve[E]): string =
  ## Generate the textual representation of ``pr``.
  var stream = newStringStream()
  writeText(stream, pr, textPreserves)
  result = move stream.data