#!/usr/bin/env python3

"""Replaces absolute line numbers in lit-tests with relative line numbers.

Writing line numbers like 152 in 'RUN: or CHECK:' makes tests hard to maintain:
inserting lines in the middle of the test means updating all the line numbers.

Encoding them relative to the current line helps, and tools support it:
    Lit will substitute %(line+2) with the actual line number
    FileCheck supports [[@LINE+2]]

This tool takes a regex which captures a line number, and a list of test files.
It searches for line numbers in the files and replaces them with a relative
line number reference.
"""

USAGE = """Example usage:
    find -type f clang/test/CodeCompletion | grep -v /Inputs/ | \\
    xargs relative_lines.py --dry-run --verbose --near=100 \\
    --pattern='-code-completion-at[ =]%s:(\d+)' \\
    --pattern='requires fix-it: {(\d+):\d+-(\d+):\d+}'
"""

import argparse
import re
import sys

def b(x):
    return bytes(x, encoding='utf-8')

parser = argparse.ArgumentParser(prog = 'relative_lines',
                                 description = __doc__,
                                 epilog = USAGE,
                                 formatter_class=argparse.RawTextHelpFormatter)
parser.add_argument('--near', type=int, default=20,
                    help = "maximum line distance to make relative")
parser.add_argument('--partial', action='store_true', default=False,
                    help = "apply replacements to files even if others failed")
parser.add_argument('--pattern', default=[], action='append',
                    type=lambda x: re.compile(b(x)),
                    help = "regex to match, with line numbers captured in ().")
parser.add_argument('--verbose', action='store_true', default=False,
                    help = "print matches applied")
parser.add_argument('--dry-run', action='store_true', default=False,
                    help = "don't apply replacements. Best with --verbose.")
parser.add_argument('files', nargs = '+')
args = parser.parse_args()

for file in args.files:
    try:
        contents = open(file, 'rb').read()
    except UnicodeDecodeError as e:
        print(f"{file}: not valid UTF-8 - {e}", file=sys.stderr)
    failures = 0

    def line_number(offset):
        return 1 + contents[:offset].count(b'\n')

    def replace_one(capture, line, offset):
        """Text to replace a capture group, e.g. 42 => %(line+1)"""
        try:
            target = int(capture)
        except ValueError:
            print(f"{file}:{line}: matched non-number '{capture}'", file=sys.stderr)
            return capture

        if args.near > 0 and abs(target - line) > args.near:
            print(f"{file}:{line}: target line {target} is farther than {args.near}", file=sys.stderr)
            return capture
        if target > line:
            delta = '+' + str(target - line)
        elif target < line:
            delta = '-' + str(line - target)
        else:
            delta = ''

        prefix = contents[:offset].rsplit(b'\n')[-1]
        is_lit = b'RUN' in prefix or b'DEFINE' in prefix
        text = ('%(line{0})' if is_lit else '[[@LINE{0}]]').format(delta)
        if args.verbose:
            print(f"{file}:{line}: {0} ==> {text}")
        return b(text)

    def replace_match(m):
        """Text to replace a whole match, e.g. --at=42:3 => --at=%(line+2):3"""
        line = 1 + contents[:m.start()].count(b'\n')
        result = b''
        pos = m.start()
        for index, capture in enumerate(m.groups()):
            index += 1 # re groups are conventionally 1-indexed
            result += contents[pos:m.start(index)]
            replacement = replace_one(capture, line, m.start(index))
            result += replacement
            if replacement == capture:
                global failures
                failures += 1
            pos = m.end(index)
        result += contents[pos:m.end()]
        return result

    for pattern in args.pattern:
        contents = re.sub(pattern, replace_match, contents)
    if failures > 0 and not args.partial:
        print(f"{file}: leaving unchanged (some failed, --partial not given)")
        continue
    if not args.dry_run:
        open(file, "wb").write(contents)