#!/usr/bin/env python3
"""Repair FernFlower's stale local variable references, scoped to the method.

The decompiler renames conflicting locals only sometimes: a declaration ends up
as `variantlist` while its uses stay `variantlist1`, and javac reports
"cannot find symbol ... variable variantlist1".

Renaming is confined to the enclosing method. That matters because the suffixed
name is often a real, correctly declared variable in a *different* method of the
same class, and a whole-file rename would corrupt it.

The method is found by its declaration line and the closing brace at the same
indentation, which is reliable for well-formed decompiled output.

    python fix_stale_locals.py <errors.txt> [--apply]
"""

import argparse
import collections
import os
import re

ERROR = re.compile(r'^(?P<file>[A-Za-z]:.*?\.java):(?P<line>\d+): error: (?P<msg>.*)$')
SYMBOL = re.compile(r'^ {2}symbol:\s*variable (?P<name>\w+)\s*$')
DECL = re.compile(r'^[ \t]*(?:final\s+)?[A-Za-z_$][\w$.<>,\[\] ]*\s+(?P<name>[A-Za-z_$]\w*)\s*(?==|;|,|\))')
METHOD = re.compile(r'^[ \t]{0,8}(?:(?:public|private|protected|static|final|abstract|synchronized|native|default|strictfp)\s+)*'
                    r'[\w$.<>,\[\] ]+\s+\w+\s*\([^;]*\)\s*(?:throws\s+[\w., ]+)?\s*\{\s*$')


def method_regions(lines):
    """Returns [(start_index, end_index_exclusive, indent)] for each method."""
    regions = []
    for i, line in enumerate(lines):
        if not METHOD.match(line):
            continue
        indent = len(line) - len(line.lstrip())
        close = ' ' * indent + '}'
        for j in range(i + 1, len(lines)):
            if lines[j].rstrip() == close:
                regions.append((i, j + 1, indent))
                break
    return regions


def region_of(regions, index):
    for start, end, _ in regions:
        if start <= index < end:
            return start, end
    return None


def main():
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument('errors')
    parser.add_argument('--apply', action='store_true')
    args = parser.parse_args()

    missing = collections.defaultdict(set)
    current = None
    with open(args.errors, encoding='utf-8', errors='replace') as handle:
        for raw in handle:
            line = raw.rstrip('\n').rstrip('\r')
            m = ERROR.match(line)
            if m:
                current = m.group('file')
                continue
            s = SYMBOL.match(line)
            if s and current:
                missing[current].add(s.group('name'))

    files_changed = 0
    renames = 0
    skipped = []

    for path in sorted(missing):
        if not os.path.isfile(path):
            continue
        with open(path, encoding='utf-8', errors='replace') as handle:
            text = handle.read()
        lines = text.split('\n')
        regions = method_regions(lines)

        # for each stale name, which regions hold the clean declaration
        edits = collections.defaultdict(list)  # old name -> list of (start, end)
        for name in sorted(missing[path]):
            pattern = re.compile(r'\b%s\b' % re.escape(name))
            longer = re.compile(r'\b%s\d+\b' % re.escape(name))
            shorter = name.rstrip('0123456789')
            shorter_pattern = re.compile(r'\b%s\b' % re.escape(shorter)) if shorter != name else None

            hits = 0
            for start, end, _indent in regions:
                chunk = '\n'.join(lines[start:end])
                if not pattern.search(chunk):
                    continue
                # Either direction may be the stale one: sometimes the use kept
                # the short name while the declaration gained a suffix.
                target = None
                if shorter_pattern is not None and shorter_pattern.search(chunk):
                    target = shorter
                else:
                    seen = {m.group(0) for m in longer.finditer(chunk)}
                    if len(seen) == 1:
                        target = seen.pop()
                if target is None:
                    continue
                edits[name].append((start, end, target))
                hits += 1

            if not hits:
                skipped.append('%s: nothing in scope matches %s'
                               % (os.path.basename(path), name))
            else:
                renames += hits

        if not edits:
            continue

        # rebuild from the last region so earlier edits keep their positions
        replacements = []
        for name, spans in edits.items():
            for start, end, target in spans:
                chunk = '\n'.join(lines[start:end])
                chunk = re.sub(r'\b%s\b' % re.escape(name), target, chunk)
                replacements.append((start, end, chunk))

        replacements.sort(key=lambda t: t[0], reverse=True)
        for start, end, chunk in replacements:
            lines[start:end] = chunk.split('\n')

        files_changed += 1
        if args.apply:
            with open(path, 'w', encoding='utf-8', newline='\n') as handle:
                handle.write('\n'.join(lines))

    print('methods fixed: %d across %d files' % (renames, files_changed))
    if skipped:
        print('unresolved %d:' % len(skipped))
        for line in sorted(set(skipped)):
            print('  %s' % line)
    if not args.apply:
        print('dry run, pass --apply to write')
    return 0


if __name__ == '__main__':
    raise SystemExit(main())