#!/usr/bin/env python
r'''
Repren is a simple but flexible command-line tool for rewriting file contents
according to a set of regular expression patterns, and to rename or move files
according to patterns. Essentially, it is a general-purpose, brute-force text
file refactoring tool. For example, repren could rename all occurrences of
certain class and variable names in a set of Java source files, while
simultaneously renaming the Java files according to the same pattern. It's more
powerful than usual options like `perl -pie`, `rpl`, or `sed`:

- It can also rename files, including moving files and creating directories.
- It supports fully expressive regular expression substitutions.
- It performs group renamings, i.e. rename "foo" as "bar", and "bar" as "foo"
  at once, without requiring a temporary intermediate rename.
- It is careful. It has a nondestructive mode, and prints clear stats on its
  changes. It leaves backups. File operations are done atomically, so
  interruptions never leave a previously existing file truncated or partly
  edited.
- It supports "magic" case-preserving renames that let you find and rename
  identifiers with case variants (lowerCamel, UpperCamel, lower_underscore, and
  UPPER_UNDERSCORE) consistently.
- It has this nice documentaion!

If file paths are provided, repren replaces those files in place, leaving a
backup with extension ".orig". If directory paths are provided, it applies
replacements recursively to all files in the supplied paths that are not in the
exclude pattern. If no arguments are supplied, it reads from stdin and writes
to stdout.

Patterns:

Patterns can be supplied in a text file, with one or more replacements consisting
of regular expression and replacement. For example:

    # Sample pattern file
    frobinator<tab>glurp
    WhizzleStick<tab>AcmeExtrudedPlasticFunProvider
    figure ([0-9+])<tab>Figure \1

(Where `<tab>` is an actual tab character.) Each line is a replacement.
Empty lines and #-prefixed comments are ignored.

As a short-cut, a single replacement can be specified on the command line using
`--from` (match) and `--to` (replacement).

Examples:

    # Here `patfile` is a patterns file.
    # Rewrite stdin:
    repren -p patfile < input > output

    # Shortcut with a single pattern replacement (replace foo with bar):
    repren --from foo --to bar < input > output

    # Rewrite a few files in place, also requiring matches be on word breaks:
    repren -p patfile --word-breaks myfile1 myfile2 myfile3

    # Rewrite whole directory trees. Since this is a big operation, we use
    # `-n` to do a dry run that only prints what would be done:
    repren -n -p patfile --word-breaks --full mydir1

    # Now actually do it:
    repren -p patfile --word-breaks --full mydir1

    # Same as above, for all case variants:
    repren -p patfile --word-breaks --preserve-case --full mydir1

Notes:

- As with sed, replacements are made line by line by default. Memory
  permitting, replacements may be done on entire files using `--at-once`.
- As with sed, replacement text may include backreferences to groups within the
  regular expression, using the usual syntax: \1, \2, etc.
- In the pattern file, both the regular expression and the replacement may
  contain the usual escapes `\n`, `\t`, etc. (To match a multi-line pattern,
  containing `\n`, you must must use `--at-once`.)
- Replacements are all matched on each input file, then all replaced, so it's
  possible to swap or otherwise change names in ways that would require
  multiple steps if done one replacement at at a time.
- If two patterns have matches that overlap, only one replacement is applied,
  with preference to the pattern appearing first in the patterns file.
- If one pattern is a subset of another, consider if `--word-breaks` will help.
- If patterns have special charaters, `--literal` may help.
- The case-preserving option works by adding all case variants to the pattern
  replacements, e.g. if the pattern file has foo_bar -> xxx_yyy, the
  replacements fooBar -> xxxYyy, FooBar -> XxxYyy, FOO_BAR -> XXX_YYY are also
  made. Assumes each pattern has one casing convention. (Plain ASCII names only.)
- The same logic applies to filenames, with patterns applied to the full file
  path with slashes replaced and then and parent directories created as needed,
  e.g. `my/path/to/filename` can be rewritten to `my/other/path/to/otherfile`.
  (Use caution and test with `-n`, especially when using absolute path
  arguments!)
- Files are never clobbered by renames. If a target already exists, or multiple
  files are renamed to the same target, numeric suffixes will be added to make
  the files distinct (".1", ".2", etc.).
- Files are created at a temporary location, then renamed, so original files are
  left intact in case of unexpected errors. File permissions are preserved.
- Backups are created of all modified files, with the suffix ".orig".
- By default, recursive searching omits paths starting with ".". This may be
  adjusted with `--exclude`. Files ending in `.orig` are always ignored.
- Data can be in any encoding, as it is treated as binary, and not interpreted
  in a specific encoding like UTF-8. This is less error prone in real-life
  situations where files have encoding inconsistencies. However, note the
  `--case-preserving` logic only handles casing conversions correctly for plain
  ASCII letters `[a-zA-Z]`.
'''

# Author: jlevy
# Created: 2014-07-09

from __future__ import print_function
import re, sys, os, shutil, optparse, bisect

# Definitive version. Update with each release.
VERSION = "0.3.9"

DESCRIPTION = "repren: Multi-pattern string replacement and file renaming"
LONG_DESCRIPTION = __doc__.split("Patterns:")[0].strip()

BACKUP_SUFFIX = ".orig"
TEMP_SUFFIX = ".repren.tmp"
DEFAULT_EXCLUDE_PAT = r"\."


def log(op, msg):
    if op:
        msg = "- %s: %s" % (op, msg)
    print(msg, file=sys.stderr)


def fail(msg):
    print("error: " + msg, file=sys.stderr)
    sys.exit(1)


class _Tally:
    def __init__(self):
        self.files = 0
        self.chars = 0
        self.matches = 0
        self.valid_matches = 0
        self.files_changed = 0
        self.files_rewritten = 0
        self.renames = 0


_tally = _Tally()

# --- String matching ---


def _overlap(match1, match2):
    return match1.start() < match2.end() and match2.start() < match1.end()


def _sort_drop_overlaps(matches, source_name=None):
    '''Select and sort a set of disjoint intervals, omitting ones that overlap.'''
    non_overlaps = []
    starts = []
    for (match, replacement) in matches:
        index = bisect.bisect_left(starts, match.start())
        if index > 0:
            (prev_match, _) = non_overlaps[index - 1]
            if _overlap(prev_match, match):
                log(source_name, "Skipping overlapping match '%s' of '%s' that overlaps '%s' of '%s' on its left" %
                    (match.group(), match.re.pattern, prev_match.group(), prev_match.re.pattern))
                continue
        if index < len(non_overlaps):
            (next_match, _) = non_overlaps[index]
            if _overlap(next_match, match):
                log(source_name, "Skipping overlapping match '%s' of '%s' that overlaps '%s' of '%s' on its right" %
                    (match.group(), match.re.pattern, next_match.group(), next_match.re.pattern))
                continue
        starts.insert(index, match.start())
        non_overlaps.insert(index, (match, replacement))
    return non_overlaps


def _apply_replacements(input_str, matches):
    out = []
    pos = 0
    for (match, replacement) in matches:
        out.append(input_str[pos:match.start()])
        out.append(match.expand(replacement))
        pos = match.end()
    out.append(input_str[pos:])
    return "".join(out)


class _MatchCounts:
    def __init__(self, found=0, valid=0):
        self.found = found
        self.valid = valid

    def add(self, o):
        self.found += o.found
        self.valid += o.valid


def multi_replace(input_str, patterns, is_path=False, source_name=None):
    '''Replace all occurrences in the input given a list of patterns (regex,
  replacement), simultaneously, so that no replacement affects any other. E.g.
  { xxx -> yyy, yyy -> xxx } or { xxx -> yyy, y -> z } are possible. If matches
  overlap, one is selected, with matches appearing earlier in the list of
  patterns preferred.
  '''
    matches = []
    for (regex, replacement) in patterns:
        for match in regex.finditer(input_str):
            matches.append((match, replacement))
    valid_matches = _sort_drop_overlaps(matches, source_name=source_name)
    result = _apply_replacements(input_str, valid_matches)

    global _tally
    if not is_path:
        _tally.chars += len(input_str)
        _tally.matches += len(matches)
        _tally.valid_matches += len(valid_matches)

    return result, _MatchCounts(len(matches), len(valid_matches))

# --- Case handling (only used for case-preserving magic) ---

# TODO: Could handle dash-separated names as well.

# FooBarBaz -> Foo, Bar, Baz
# XMLFooHTTPBar -> XML, Foo, HTTP, Bar
_camel_split_pat1 = re.compile("([^A-Z])([A-Z])")
_camel_split_pat2 = re.compile("([A-Z])([A-Z][^A-Z])")

_name_pat = re.compile(r"\w+")


def _split_name(name):
    '''Split a camel-case or underscore-formatted name into words. Return separator and words.'''
    if name.find("_") >= 0:
        return "_", name.split("_")
    else:
        temp = _camel_split_pat1.sub("\\1\t\\2", name)
        temp = _camel_split_pat2.sub("\\1\t\\2", temp)
        return "", temp.split("\t")


def _capitalize(word):
    return word[0].upper() + word[1:].lower()


def to_lower_camel(name):
    words = _split_name(name)[1]
    return words[0].lower() + "".join([_capitalize(word) for word in words[1:]])


def to_upper_camel(name):
    words = _split_name(name)[1]
    return "".join([_capitalize(word) for word in words])


def to_lower_underscore(name):
    words = _split_name(name)[1]
    return "_".join([word.lower() for word in words])


def to_upper_underscore(name):
    words = _split_name(name)[1]
    return "_".join([word.upper() for word in words])


def _transform_expr(expr, transform):
    return _name_pat.sub(lambda m: transform(m.group()), expr)


def all_case_variants(expr):
    '''Return all casing variations of an expression, replacing each name with
  lower- and upper-case camel-case and underscore style names, in fixed order.'''
    return [_transform_expr(expr, transform)
            for transform in [to_lower_camel, to_upper_camel, to_lower_underscore, to_upper_underscore]]

# --- File handling ---


def make_parent_dirs(path):
    '''Ensure parent directories of a file are created as needed.'''
    dirname = os.path.dirname(path)
    if dirname and not os.path.isdir(dirname):
        os.makedirs(dirname)
    return path


def move_file(source_path, dest_path, clobber=False):
    if not clobber:
        trailing_num = re.compile("(.*)[.]\d+$")
        i = 1
        while os.path.exists(dest_path):
            match = trailing_num.match(dest_path)
            if match:
                dest_path = match.group(1)
            dest_path = "%s.%s" % (dest_path, i)
            i += 1
    shutil.move(source_path, dest_path)


def transform_stream(transform, stream_in, stream_out, by_line=False):
    counts = _MatchCounts()
    if by_line:
        for line in stream_in:
            if transform:
                (new_line, new_counts) = transform(line)
                counts.add(new_counts)
            else:
                new_line = line
            stream_out.write(new_line)
    else:
        contents = stream_in.read()
        (new_contents, new_counts) = transform(contents) if transform else contents
        stream_out.write(new_contents)
    return counts


def transform_file(transform, source_path, dest_path,
                   orig_suffix=BACKUP_SUFFIX,
                   temp_suffix=TEMP_SUFFIX,
                   by_line=False,
                   dry_run=False):
    '''Transform full contents of file at source_path with specified function,
  either line-by-line or at once in memory, writing dest_path atomically and keeping a backup.
  Source and destination may be the same path.'''
    counts = _MatchCounts()
    global _tally
    changed = False
    if transform:
        orig_path = source_path + orig_suffix
        temp_path = dest_path + temp_suffix
        # TODO: This will create a directory even in dry_run mode, but perhaps that's acceptable.
        # https://github.com/jlevy/repren/issues/6
        make_parent_dirs(temp_path)
        perms = os.stat(source_path).st_mode & 0o777
        with open(source_path, "rb") as stream_in:
            with os.fdopen(os.open(temp_path, os.O_WRONLY | os.O_CREAT, perms), "wb") as stream_out:
                counts = transform_stream(transform, stream_in, stream_out, by_line=by_line)

        # All the above happens in dry-run mode so we get tallies.
        # Important: We don't modify original file until the above succeeds without exceptions.
        if not dry_run and (dest_path != source_path or counts.found > 0):
            move_file(source_path, orig_path, clobber=True)
            move_file(temp_path, dest_path, clobber=False)
        else:
            # If we're in dry-run mode, or if there were no changes at all, just forget the output.
            os.remove(temp_path)

        _tally.files += 1
        if counts.found > 0:
            _tally.files_rewritten += 1
            changed = True
        if dest_path != source_path:
            _tally.renames += 1
            changed = True
    elif dest_path != source_path:
        if not dry_run:
            make_parent_dirs(dest_path)
            move_file(source_path, dest_path, clobber=False)
        _tally.files += 1
        _tally.renames += 1
        changed = True
    if changed:
        _tally.files_changed += 1

    return counts


def rewrite_file(path, patterns, do_renames=False, do_contents=False, by_line=False, dry_run=False):
    dest_path = multi_replace(path, patterns, is_path=True)[0] if do_renames else path
    transform = None
    if do_contents:
        transform = lambda contents: multi_replace(contents, patterns, source_name=path)
    counts = transform_file(transform, path, dest_path, by_line=by_line, dry_run=dry_run)
    if counts.found > 0:
        log("modify", "%s: %s matches" % (path, counts.found))
    if dest_path != path:
        log("rename", "%s -> %s" % (path, dest_path))


def walk_files(paths, exclude_pat=DEFAULT_EXCLUDE_PAT):
    out = []
    exclude_re = re.compile(exclude_pat)
    for path in paths:
        if not os.path.exists(path):
            fail("path not found: %s" % path)
        if os.path.isfile(path):
            out.append(path)
        else:
            for (root, dirs, files) in os.walk(path):
                # Prune files that are excluded, and always prune backup files.
                out += [os.path.join(root, f) for f in files
                        if not exclude_re.match(f) and not f.endswith(BACKUP_SUFFIX) and not f.endswith(TEMP_SUFFIX)]
                # Prune subdirectories.
                dirs[:] = [d for d in dirs if not exclude_re.match(d)]
    return out


def rewrite_files(root_paths, patterns,
                  do_renames=False,
                  do_contents=False,
                  exclude_pat=DEFAULT_EXCLUDE_PAT,
                  by_line=False,
                  dry_run=False):
    paths = walk_files(root_paths, exclude_pat=exclude_pat)
    log(None, "Found %s files in: %s" % (len(paths), ", ".join(root_paths)))
    for path in paths:
        rewrite_file(path, patterns, do_renames=do_renames, do_contents=do_contents, by_line=by_line, dry_run=dry_run)

# --- Invocation ---


def parse_patterns(patterns_str, literal=False, word_breaks=False, insensitive=False, preserve_case=False):
    patterns = []
    flags = re.I if insensitive else 0
    for line in patterns_str.splitlines():
        bits = None
        try:
            bits = line.split('\t')
            if line.strip().startswith("#"):
                continue
            elif line.strip() and len(bits) == 2:
                (regex, replacement) = bits
                if literal:
                    regex = re.escape(regex)
                pairs = []
                if preserve_case:
                    pairs += zip(all_case_variants(regex), all_case_variants(replacement))
                pairs.append((regex, replacement))
                # Avoid spurious overlap warnings by removing dups.
                pairs = sorted(set(pairs))
                for (regex_variant, replacement_variant) in pairs:
                    if word_breaks:
                        regex_variant = r'\b' + regex_variant + r'\b'
                    patterns.append((re.compile(regex_variant, flags), replacement_variant))
            else:
                fail("invalid line in pattern file: %s" % bits)
        except Exception as e:
            fail("error parsing pattern: %s: %s" % (e, bits))
    return patterns

# Remove excessive epilog formatting in optparse.
optparse.OptionParser.format_epilog = lambda self, formatter: self.epilog

if __name__ == '__main__':
    USAGE = "%prog -p <pattern-file> [options] [path ...]"
    parser = optparse.OptionParser(usage=USAGE, description=DESCRIPTION, epilog="\n" + __doc__, version=VERSION)
    parser.add_option("--from", help="single replacement: match string", dest="from_pat")
    parser.add_option("--to", help="single replacement: replacement string", dest="to_pat")
    parser.add_option("-p", "--patterns", help="file with multiple replacement patterns (see below)", dest="pat_file")
    parser.add_option("--full",
                      help="do file renames and search/replace on file contents",
                      dest="do_full",
                      action="store_true")
    parser.add_option("--renames",
                      help="do file renames only; do not modify file contents",
                      dest="do_renames",
                      action="store_true")
    parser.add_option("--literal",
                      help="use exact string matching, rather than regular expresion matching",
                      dest="literal",
                      action="store_true")
    parser.add_option("-i", "--insensitive", help="match case-insensitively", dest="insensitive", action="store_true")
    parser.add_option("--preserve-case",
                      help="do case-preserving magic to transform all case variants (see below)",
                      dest="preserve_case",
                      action="store_true")
    parser.add_option("-b", "--word-breaks",
                      help="require word breaks (regex \\b) around all matches",
                      dest="word_breaks",
                      action="store_true")
    parser.add_option("--exclude",
                      help="file/directory name regex to exclude",
                      dest="exclude_pat",
                      default=DEFAULT_EXCLUDE_PAT)
    parser.add_option("--at-once",
                      help="transform each file's contents at once, instead of line by line",
                      dest="at_once",
                      action="store_true")
    parser.add_option("-t", "--parse-only",
                      help="parse and show patterns only",
                      dest="parse_only",
                      action="store_true")
    parser.add_option("-n", "--dry-run",
                      help="dry run: just log matches without changing files",
                      dest="dry_run",
                      action="store_true")

    (options, root_paths) = parser.parse_args()

    if options.dry_run:
        log(None, "Dry run: No files will be changed")

    options.do_contents = not options.do_renames
    options.do_renames = options.do_renames or options.do_full

    # log(None, "Settings: %s" % options)

    if options.pat_file:
        if options.from_pat or options.to_pat:
            parser.error("cannot use both --patterns and --from/--to")
    elif options.from_pat is None or options.to_pat is None:
        parser.error("must specify --patterns or both --from and --to")
    if options.insensitive and options.preserve_case:
        parser.error("cannot use --insensitive and --preserve-case at once")

    by_line = not options.at_once

    if options.pat_file:
        with open(options.pat_file, "rb") as f:
            pat_str = f.read()
    else:
        pat_str = '%s\t%s' % (options.from_pat, options.to_pat)
    patterns = parse_patterns(pat_str,
                              literal=options.literal,
                              word_breaks=options.word_breaks,
                              insensitive=options.insensitive,
                              preserve_case=options.preserve_case)

    if len(patterns) == 0:
        fail("found no parse patterns")

    log(None, ("Using %s patterns:\n  " % len(patterns)) + "\n  ".join(["'%s' -> '%s'" % (regex.pattern, replacement)
                                                                        for (regex, replacement) in patterns]))

    if not options.parse_only:
        if len(root_paths) > 0:
            rewrite_files(root_paths, patterns,
                          do_renames=options.do_renames,
                          do_contents=options.do_contents,
                          exclude_pat=options.exclude_pat,
                          by_line=by_line,
                          dry_run=options.dry_run)

            log(None, "Read %s files (%s chars), found %s matches (%s skipped due to overlaps)" %
                (_tally.files, _tally.chars, _tally.valid_matches, _tally.matches - _tally.valid_matches))
            change_words = "Dry run: Would have changed" if options.dry_run else "Changed"
            log(None, "%s %s files (%s rewritten and %s renamed)" % (change_words, _tally.files_changed,
                                                                     _tally.files_rewritten, _tally.renames))
        else:
            if options.do_renames:
                parser.error("can't specify --renames on stdin; give filename arguments")
            if options.dry_run:
                parser.error("can't specify --dry-run on stdin; give filename arguments")
            transform = lambda contents: multi_replace(contents, patterns)
            transform_stream(transform, sys.stdin, sys.stdout, by_line=by_line)

            log(None, "Read %s chars, made %s replacements (%s skipped due to overlaps)" %
                (_tally.chars, _tally.valid_matches, _tally.matches - _tally.valid_matches))

# TODO:
#   --undo mode to revert a previous run by using .orig files; --clean mode to remove .orig files
#   Expose re.MULTILINE flag
#   Log collisions
#   Separate patterns file for renames and replacements
#   Quiet and verbose modes (the latter logging each substitution)
#   Support --preserve-case for Unicode (non-ASCII) characters (messy)
