Sample script for SF-0033.

iana-charset-names-to-swift.py

#!/usr/bin/python3

import re
from typing import List, Optional
import urllib.request as request
import xml.etree.ElementTree as ElemTree

REQUIRED_CHARSET_NAMES: List[str] = [
  "UTF-8",
  "US-ASCII",
  "EUC-JP",
  "ISO-8859-1",
  "Shift_JIS",
  "ISO-8859-2",
  "UTF-16",
  "windows-1251",
  "windows-1252",
  "windows-1253",
  "windows-1254",
  "windows-1250",
  "ISO-2022-JP",
  "macintosh",
  "UTF-16BE",
  "UTF-16LE",
  "UTF-32",
  "UTF-32BE",
  "UTF-32LE",
]
CHARSETS_XML_URL = "https://www.iana.org/assignments/character-sets/character-sets.xml"
CHARSETS_XML_STRING = request.urlopen(request.Request(CHARSETS_XML_URL)).read()
CHARSETS_XML_ROOT = ElemTree.fromstring(CHARSETS_XML_STRING)
CHARSETS_XML_NS = "http://www.iana.org/assignments"
CHARSETS_XML_RECORD_ELEMENTS = CHARSETS_XML_ROOT.findall(
  "./{%s}registry/{%s}record" %(CHARSETS_XML_NS, CHARSETS_XML_NS)
)
SWIFT_CODE_INDENT = "    "


class IANACharsetNameRecord:
  def __init__(self, recordElem: ElemTree.Element):
    self._name: str = recordElem.find('./{%s}name' %(CHARSETS_XML_NS)).text
    self._preferredMIMEName: Optional[str] = getattr(recordElem.find('./{%s}preferred_alias' %(CHARSETS_XML_NS)), 'text', None)
    self._aliases: List[str] = list(map(
      lambda aliasElem: aliasElem.text,
      recordElem.findall('./{%s}alias' %(CHARSETS_XML_NS))
    ))
    self._camelCasedName = None

  @property
  def name(self) -> str:
    return self._name
  
  @property
  def preferredMIMEName(self) -> Optional[str]:
    return self._preferredMIMEName
  
  @property
  def representativeName(self) -> str:
    return self.preferredMIMEName or self.name

  @property
  def aliases(self) -> List[str]:
    return self._aliases
  
  @property
  def camelCasedName(self) -> str:
    if (self._camelCasedName is not None):
      return self._camelCasedName
    
    camelCasedName = ""
    previousWord = None
    for ii, word in enumerate(re.split(r"[^0-9A-Za-z]", self.representativeName)):
      if (ii == 0):
        camelCasedName = word.lower()
      else:
        if re.search(r"[0-9]$", previousWord) and re.search(r"^[0-9]", word):
          camelCasedName += "_"
        
        if (re.fullmatch("[A-Z]+", word)):
          camelCasedName += word
        else:
          camelCasedName += word.capitalize()

      previousWord = word

    self._camelCasedName = camelCasedName
    return camelCasedName
  
  @property
  def swiftCodeLines(self) -> List[str]:
    def __stringLiteralOrNil(string: Optional[str]) -> str:
        if (string is None):
          return 'nil'
        return f'"{string}"'

    lines: List[str] = []
    lines.append(f"/// IANA Charset `{self.representativeName}`.")
    lines.append(f"static let {self.camelCasedName} = IANACharset(")
    lines.append(f"{SWIFT_CODE_INDENT}preferredMIMEName: {__stringLiteralOrNil(self.preferredMIMEName)},")
    lines.append(f'{SWIFT_CODE_INDENT}name: "{self.name}",')
    lines.append(f"{SWIFT_CODE_INDENT}aliases: [")
    for alias in self.aliases:
      lines.append(f"{SWIFT_CODE_INDENT * 2}\"{alias}\",")
    lines.append(f"{SWIFT_CODE_INDENT}]")
    lines.append(")")
    return lines


def generateSwiftCode() -> str:
  result = "extension IANACharset {"
  for record in map(lambda recordElem: IANACharsetNameRecord(recordElem), CHARSETS_XML_RECORD_ELEMENTS):
    if (record.representativeName not in REQUIRED_CHARSET_NAMES):
      continue
    result += "\n"
    result += "\n".join(map(lambda line: SWIFT_CODE_INDENT + line, record.swiftCodeLines))
    result += "\n"
  result += "}\n"
  return result


print(generateSwiftCode())