app.py

import re
import unicodedata
import urllib
import flask

app = flask.Flask(__name__)

character_names = { "\n": "LF", "\r": "CR", "\t": "TAB" }

# Load the Unicode blocks list from our file.
unicode_blocks = []
with open("unidata-blocks.txt") as f:
  for line in f:
    if line.strip() == "" or line[0] == "#": continue
    m = re.match("([0-9A-F]+)\.\.([0-9A-F]+); (.*)", line)
    unicode_blocks.append({
      "start": int(m.group(1), 16),
      "end": int(m.group(2), 16),
      "name": m.group(3),
    })

def lookup_block(character):
  character = ord(character)
  for block in unicode_blocks:
    if block["start"] <= character <= block["end"]:
      return block["name"]
  return None

def highlight_content(text):
  ret = []
  for character in text:
    suspicious = False

    # How to display this character?
    if unicodedata.category(character)[0] in ("L", "N", "P", "S"):
      # letters, numbers, punctuation, and symbols -- things that should be displayable
      display = character
    elif character == " ":
      # show the space as a space
      display = " "
    elif character in character_names:
      # use some names that we preset
      display = character_names[character]
    else:
      # show the character as its name ("?" as fallback if character has no name)
      display = unicodedata.name(character, "?")
      suspicious = True

    if lookup_block(character) != "Basic Latin":
      suspicious = True

    if len(ret) > 0 and ret[-1]["character"]+character == "\r\n":
      ret[-1]["display"] += display
      continue

    ret.append({
      "codepoint": hex(ord(character)),
      "block": lookup_block(character),
      "character": character,
      "display": display,
      "eol": character in ("\n", "\r"),
      "suspicious": suspicious,
    })
  return ret

@app.route('/')
def hello():
  return flask.render_template('index.html')

@app.route('/highlight', methods=['POST'])
def highlight():
  content = highlight_content(flask.request.form['content'])
  return flask.render_template('highlight.html', content=content)

if __name__ == '__main__':
  app.run(host='0.0.0.0', debug=True)