#!/usr/bin/env python3

import re
import subprocess
import string

import click


@click.command()
@click.argument('texfile')
@click.argument('bibliography')
@click.argument('revision')
def generate_git_tex_diff(texfile, bibliography, revision):
    with open(texfile) as f:
        tex_lines = len(list(f))
    with open(bibliography) as f:
        bib_lines = len(list(f))

    tex_proc = subprocess.run(['git', 'diff', f'-U{tex_lines+1}', '--word-diff', '--color=always', revision, texfile],
            check=True, capture_output=True)

    bib_proc = subprocess.run(['git', 'diff', f'-U{bib_lines+1}', '--word-diff', '--color=always', revision, bibliography],
            check=True, capture_output=True)
    ADDITION_RE_R = '\033\\[32m\\{\\+(.*?)([^\\\\]%.*?)?\\+\\}\033\\[m'
    DELETION_RE_R = '\033\\[31m\\[-(.*?)([^\\\\]%.*?)?\\-]\033\\[m'
    addition_re = re.compile(ADDITION_RE_R)
    deletion_re = re.compile(DELETION_RE_R)
    combined_re = re.compile(f'{DELETION_RE_R}{ADDITION_RE_R}')
    csi_re = re.compile('\033\\[.*?m')
    bibtex_entry_def_re = re.compile('@.*?{(.*?),')

    bibliography_categories  = '\\DeclareBibliographyCategory{diff_new_entry}\n'
    bibliography_categories += '\\DeclareBibliographyCategory{diff_deleted_entry}\n'
    bibliography_categories += '\\AtEveryBibitem{\\ifcategory{diff_new_entry}{\\color{diffgreen}}{\\ifcategory{diff_deleted_entry}{\\color{diffred}}{\\color{black}}}}\n'

    added_entries, removed_entries = [], []
    for line in bib_proc.stdout.decode().splitlines():
        if (match := addition_re.fullmatch(line.strip())):
            if (entry_def := bibtex_entry_def_re.fullmatch(match.group(1))):
                added_entries.append(entry_def.group(1))

        if (match := deletion_re.fullmatch(line.strip())):
            if (entry_def := bibtex_entry_def_re.fullmatch(match.group(1))):
                removed_entries.append(entry_def.group(1))

    if added_entries:
        bibliography_categories += '\\addtocategory{diff_new_entry}{' + ','.join(added_entries) + '}\n'
    if removed_entries:
        bibliography_categories += '\\addtocategory{diff_deleted_entry}{' + ','.join(removed_entries) + '}\n'

    content_started = False
    document_started = False
    for line in tex_proc.stdout.decode().splitlines():

        if not content_started:
            if '@@' in line:
                content_started = True
            continue

        line = line.rstrip()
        if document_started: # diff results in preamble

            def suppress_small_changes(match):
                old, _1, new, _2 = match.groups()

                new_chars = list(new)
                for char in old:
                    if char not in string.ascii_letters:
                        continue

                    if char not in new_chars:
                        return match.group(0) # return original text

                    new_chars.remove(char)

                if any(char in string.ascii_letters for char in new_chars):
                    return match.group(0) # return original text

                return new

            line = combined_re.sub(suppress_small_changes, line)
            line = addition_re.sub(r' \\color{diffgreen}\1 \\color{black}', line)
            line = deletion_re.sub(r' \\color{diffred}\1 \\color{black}', line)

        else:
            if '\\begin{document}' in line:
                document_started = True
                print(bibliography_categories)
                print('\\definecolor{diffgreen}{HTML}{1e8449}')
                print('\\definecolor{diffred}{HTML}{cb4335}')

            line = addition_re.sub(r'\1', line)
            line = deletion_re.sub(r'', line)

        line = csi_re.sub('', line)
        print(line)

if __name__ == '__main__':
    generate_git_tex_diff()