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"""A differ for creating an HTML representations of proposal diffs."""
from __future__ import annotations
import html
import re
from difflib import Differ
class CombinedHtmlDiff:
"""Create an HTML representation of the differences between two pieces
of text.
"""
highlight_regex = re.compile(r'([\+\-\^]+)')
def __init__(self, source, proposal):
proposal = html.escape(proposal)
differ = Differ()
self.diff: list[str] = list(differ.compare(
source.splitlines(keepends=True),
proposal.splitlines(keepends=True),
))
def make_text(self) -> str:
return '\n'.join(self.diff)
def make_html(self) -> str:
"""Return the HTML representation of the differences between
`source` and `proposal`.
:param source: the original text
:param proposal: the proposed text
"""
html = []
diff = self.diff[:]
line = diff.pop(0)
next = diff.pop(0)
while True:
html.append(self._handle_line(line, next))
line = next
try:
next = diff.pop(0)
except IndexError:
html.append(self._handle_line(line))
break
return ''.join(html).rstrip()
def _handle_line(self, line: str, next: str | None = None) -> str:
"""Handle an individual line in a diff."""
prefix = line[0]
text = line[2:]
if prefix == ' ':
return text
elif prefix == '?':
return ''
if next is not None and next[0] == '?':
tag = prefix == '+' and 'ins' or 'del'
text = self._highlight_text(text, next, tag)
css_class = prefix == '+' and 'prop-added' or 'prop-removed'
return f'<span class="{css_class}">{text.rstrip()}</span>\n'
def _highlight_text(self, text: str, next: str, tag: str) -> str:
"""Highlight the specific changes made to a line by adding
<ins> and <del> tags.
"""
next = next[2:]
new_text: list[str] = []
start = 0
for match in self.highlight_regex.finditer(next):
new_text.extend((
text[start:match.start()],
f'<{tag}>',
text[match.start():match.end()],
f'</{tag}>',
))
start = match.end()
new_text.append(text[start:])
return ''.join(new_text)
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