.files/bin/patchdir

#!/usr/bin/env python3
# (c) 2017-2021 Taeyeon Mori
# Requires libarchive-c
#pylint: disable=missing-module-docstring,missing-function-docstring

import argparse
import fnmatch
import pathlib
import contextlib
import os
import ctypes
import textwrap
import re
import shlex

import libarchive


# Extend libarchive-c
from libarchive import ffi
try:
    entry_copy_sourcepath = ffi.entry_copy_sourcepath
except AttributeError:
    entry_copy_sourcepath = ffi.ffi("entry_copy_sourcepath",
            [ffi.c_archive_entry_p, ffi.c_char_p],
            None)

try:
    read_disk_entry_from_file = ffi.read_disk_entry_from_file
except AttributeError:
    read_disk_entry_from_file = ffi.ffi("read_disk_entry_from_file",
            [ffi.c_archive_p, ffi.c_archive_entry_p, ffi.c_int, ffi.c_void_p],
            ffi.c_int, ffi.check_int)

try:
    write_set_format_filter_by_ext = ffi.write_set_format_filter_by_ext
except AttributeError:
    write_set_format_filter_by_ext = ffi.ffi("write_set_format_filter_by_ext",
            [ffi.c_archive_p, ffi.c_char_p],
            ffi.c_int, ffi.check_int)

try:
    read_extract2 = ffi.read_extract2
except AttributeError:
    read_extract2 = ffi.ffi("read_extract2",
            [ffi.c_archive_p, ffi.c_archive_entry_p, ffi.c_archive_p],
            ffi.c_int, ffi.check_int)

def to_bytes(path, encoding="utf-8"):
    if encoding == "fsencode":
        return os.fsencode(path)
    if isinstance(path, os.PathLike):
        path = os.fspath(path)
    if isinstance(path, bytes):
        return path
    if isinstance(path, str):
        return path.encode(encoding)
    raise ValueError(f"Don't know how to convert {path} to bytes")

class _DiskRead(libarchive.read.ArchiveRead):
    def add_file_to_archive(self, archive: libarchive.write.ArchiveWrite,
            path: os.PathLike, archive_name: os.PathLike=None, *, bufsize=ffi.page_size*8):
        archive_p = archive._pointer #pylint:disable=protected-access
        with open(path, 'rb') as fp: #pylint:disable=invalid-name
            with libarchive.entry.new_archive_entry() as entry_p:
                if archive_name:
                    entry_copy_sourcepath(entry_p, to_bytes(path, "fsencode"))
                    ffi.entry_update_pathname_utf8(entry_p, to_bytes(archive_name, "utf-8"))
                else:
                    ffi.entry_update_pathname_utf8(entry_p, to_bytes(path, "utf-8"))
                read_disk_entry_from_file(self._pointer, entry_p, fp.fileno(), None)
                ffi.write_header(archive_p, entry_p)
                buf = bytearray(bufsize)
                buf_ptr = ctypes.byref(ctypes.c_char.from_buffer(buf))
                write_data = ffi.write_data
                while (bytes_read := fp.readinto(buf)) > 0:
                    write_data(archive_p, buf_ptr, bytes_read)
                ffi.write_finish_entry(archive_p)

@contextlib.contextmanager
def disk_reader(path=None, flags=0, lookup=True):
    ard_p = ffi.read_disk_new()
    try:
        ffi.read_disk_set_behavior(ard_p, flags)
        if lookup:
            ffi.read_disk_set_standard_lookup(ard_p)
        if path:
            ffi.read_disk_open_w(ard_p, path)
        yield _DiskRead(ard_p)
    finally:
        ffi.read_free(ard_p)

@contextlib.contextmanager
def file_writer_ext(filename, target_filename=None):
    archive_p = ffi.write_new()
    try:
        bfn = to_bytes(filename, "fsencode")
        if target_filename is None:
            write_set_format_filter_by_ext(archive_p, bfn)
        else:
            write_set_format_filter_by_ext(archive_p, to_bytes(target_filename, "fsencode"))
        ffi.write_open_filename(archive_p, bfn)
        try:
            yield libarchive.write.ArchiveWrite(archive_p)
        finally:
            ffi.write_close(archive_p)
    finally:
        ffi.write_free(archive_p)

def extract_entry(entry: libarchive.entry.ArchiveEntry, dst_p: libarchive.ffi.c_archive_p, path: os.PathLike=None):
    archive_p, entry_p = entry._archive_p, entry._entry_p #pylint:disable=protected-access
    if path:
        ffi.entry_update_pathname_utf8(entry_p, to_bytes(path, "utf-8"))
    read_extract2(archive_p, entry_p, dst_p)

def copy_entry(entry: libarchive.entry.ArchiveEntry, dst: libarchive.write.ArchiveWrite, path: os.PathLike=None,
        *, bufsize=ffi.page_size*8):
    archive_p, entry_p, dst_p = entry._archive_p, entry._entry_p, dst._pointer #pylint:disable=protected-access
    if path:
        ffi.entry_update_pathname_utf8(entry_p, to_bytes(path, "utf-8"))
    # read_extract2 and write_data_block only supported with archive_write_disk :(
    #read_extract2(archive_p, entry_p, dst_p)
    ffi.write_header(dst_p, entry_p)
    buf_p = ctypes.create_string_buffer(bufsize)
    read_data, write_data = ffi.read_data, ffi.write_data
    while (bytes_read := read_data(archive_p, buf_p, bufsize)) > 0:
        write_data(dst_p, buf_p, bytes_read)
    ffi.write_finish_entry(dst_p)

def copy_all_entries(src: libarchive.read.ArchiveRead, dst: libarchive.write.ArchiveWrite) -> list[pathlib.Path]:
    entries = []
    with libarchive.entry.new_archive_entry() as entry_p:
        archive_p, dst_p = src._pointer, dst._pointer
        buf_p = ctypes.create_string_buffer(bufsize)
        read_data, write_data = ffi.read_data, ffi.write_data
        while ffi.read_next_header2(archive_p, entry_p) != ARCHIVE_EOF:
            entries.append(pathlib.Path(entry_pathname_w(entry_p)))
            #read_extract2(archive_p, entry_p, dst_p)
            ffi.write_header(dst_p, entry_p)
            while (bytes_read := read_data(archive_p, buf_p, bufsize)) > 0:
                write_data(dst_p, buf_p, bytes_read)
            ffi.write_finish_entry(dst_p)
    return entries

def list_all_entries(src: libarchive.read.ArchiveRead) -> list[pathlib.Path]:
    entries = []
    with libarchive.entry.new_archive_entry() as entry_p:
        src_p = src._pointer
        read_next_header2, ARCHIVE_EOF, entry_pathname_w, Path = \
            ffi.read_next_header2, ffi.ARCHIVE_EOF, ffi.entry_pathname_w, pathlib.Path
        while read_next_header2(src_p, entry_p) != ffi.ARCHIVE_EOF:
            entries.append(Path(entry_pathname_w(entry_p)))
    return entries

# Main
def confirm(msg, code=0):
    print(msg)
    reply = input("Continue? [n] ")
    if not (res := reply.lower().startswith("y")) and code != 0:
        sys.exit(code)
    return res

def glob_compile(pattern):
    return re.compile(fnmatch.translate(pattern))

def parse_args(argv):
    parser = argparse.ArgumentParser(prog=argv[0], description="""
        Patch a folder structure with files from an archive.
        This will replace existing files with those of the same name in an archive,
        with the option to back up the old versions and generate a script to revert the changes.
    """)
    parser.add_argument("archive",                  type=pathlib.Path,
            help="Achive file name")
    parser.add_argument("-C", "--directory",        type=pathlib.Path,  default=pathlib.Path("."),
            help="Operate in <direcory>")
    parser.add_argument("-n", "--dry-run",          action="store_true",
            help="Perform a dry run")
    parser.add_argument("--noconfirm",              action="store_true",
            help="Don't ask for confirmation on possibly dangerous operations")
    target = parser.add_argument_group("Target")
    target.add_argument("-p", "--strip",            type=int,           default=0,
            help="Strip N leading path components from archived file names.", metavar="N")
    target.add_argument("-P", "--prefix",           type=pathlib.Path,  default=None,
            help="Prepend leading path components to archived file names.")
    fmatch = target.add_mutually_exclusive_group()
    fmatch.add_argument("-m", "--match", dest="match", type=glob_compile, default=None,
            help="Only extract files matching GLOB", metavar="GLOB")
    fmatch.add_argument("-M", "--regex", dest="match", type=re.compile, default=None,
            help="Only extract files matching REGEX", metavar="REGEX")
    backup = parser.add_argument_group("Backup")
    backup.add_argument("-B", "--backup-archive",   type=pathlib.Path,  default=None,
            help="Create an archive of the original files", metavar="FILE")
    backup.add_argument("-u", "--uninstall-script", type=pathlib.Path,  default=None,
            help="Filename to save an uninstall-scipt to. Shoul be combined with -B", metavar="FILE")
    backup.add_argument("-a", "--append",           action="store_true", default=False,
            help="Update existing backup files")
    preset = parser.add_mutually_exclusive_group()
    preset.add_argument("-U", "--uninstall-preset", action="store_const", dest="preset", const="uninstall",
            help="Short-hand for '-B %%n.uninstall.tar.xz -u %%n.uninstall.sh', %%n being the archive basename")
    preset.add_argument("-A", "--append-preset",    action="store_const", dest="preset", const="append",
            help="Short-hand for '-a -B patchdir_backup.tar.xz -u patchdir_restore.sh")

    args = parser.parse_args(argv[1:])

    if args.preset == "uninstall":
        # Ignore when combined with explicit -u and -B; allows general-purpose alias patchdir='patchdir -U'
        if args.backup_archive is None:
            args.backup_archive = pathlib.Path(f"{args.archive.stem}.uninstall.tar.xz")
        if args.uninstall_script is None:
            args.uninstall_script = pathlib.Path(f"{args.archive.stem}.uninstall.sh")
    elif args.preset == "append":
        args.append = True
        if args.backup_archive is None:
            args.backup_archive = pathlib.Path("patchdir_backup.tar.xz")
        if args.uninstall_script is None:
            args.uninstall_script = pathlib.Path("patchdir_restore.sh")

    if not args.noconfirm:
        if not args.uninstall_script or not args.backup_archive:
            confirm("Original files will be lost without -B and u. Consider using -U.", 1)

    return args

# Parsing uninstall scripts
SCRIPT_TAG = "#> patchdir restore script v1 <#"
SCRIPT_BACKUP_CMDS = {"restore"}
SCRIPT_REMOVE_CMDS = {"remove"}
SCRIPT_DIR_CMDS = {"remove_dir"}
SCRIPT_META_CMDS = {"cleanup"}
SCRIPT_CMDS = SCRIPT_BACKUP_CMDS|SCRIPT_REMOVE_CMDS|SCRIPT_DIR_CMDS|SCRIPT_META_CMDS

def read_script(path):
    # Relies on ordered dictionary implementation
    is_script = False
    operations = {}
    with open(path) as f:
        for ln, line in enumerate(f):
            if line.strip() == SCRIPT_TAG:
                is_script = True
            elif is_script:
                cmd = shlex.split(line)
                if len(cmd) != 2 or cmd[0] not in SCRIPT_CMDS:
                    raise ValueError(f"Failed to read invalid line {ln} in script {path}", line)
                if cmd not in SCRIPT_META_CMDS:
                    operations[pathlib.Path(cmd[1])] = cmd[0]
    if not is_script:
        raise ValueError("Script for appending {path} doesn't seem to be a pathdir script")
    return operations

def write_script(fp, cmd, path):
    fp.write(f"{cmd:10s} {shlex.quote(str(path))}\n")

# Helpers
def makedirs(path, dryrun=False):
    if path.is_dir():
        return set()

    created = set()
    stack = [path]
    while stack:
        path = stack[-1]
        if path.parent.is_dir():
            if path.exists():
                raise IOError("Exists but not a directory: '%s'" % path)
            if dryrun:
                return set(stack)
            os.mkdir(path)
            created.add(stack.pop())
        else:
            stack.append(path.parent)

    return created

def main(argv):
    args = parse_args(argv)

    with contextlib.ExitStack() as ctx:
        # archive name is the only argument not affected by -C
        archive = ctx.enter_context(libarchive.file_reader(str(args.archive)))

        # Change directory to target
        os.chdir(args.directory)

        do_append = False
        if args.append:
            # Check consistency for append
            checks = [p.exists()
                for p in (args.backup_archive, args.uninstall_script)
                if p is not None]
            do_append = any(check)
            if do_append and not all(check):
                raise FileExistsError("Inconsistency in existing files to append to.")
        else:
            if args.backup_archive and args.backup_archive.exists():
                if args.noconfirm:
                    print("\033[31mError: Backup archive file already exist\033[0m")
                    return 3
                else:
                    confirm("Backup archive already exists.", 3)

        uninstall_script = None
        operations = {}
        folders = set()
        files = set()
        if args.uninstall_script:
            if do_append:
                operations = read_script(args.uninstall_script)
            elif args.uninstall_script.exists():
                if args.noconfirm:
                    print("\033[31mError: Uninstall script file already exist\033[0m")
                    return 3
                else:
                    confirm("Uninstall script already exists. Overwrite?", 3)
            if not args.dry_run:
                uninstall_script = ctx.enter_context(open(args.uninstall_script, "w"))
                os.chmod(uninstall_script.fileno(), 0o755)
            else:
                uninstall_script = ctx.enter_context(open("/dev/null", "w"))
            uninstall_script_dir = args.uninstall_script.parent.resolve()

            uninstall_script.write(textwrap.dedent(f"""\
                #!/bin/sh -eu
                # Uninstall script generated by:
                # {shlex.join(sys.argv)}

                cd "`dirname "$0"`/{pathlib.Path.cwd().relative_to(uninstall_script_dir)}"

                BACKUP_ARCHIVE={f"'{args.backup_archive}'" if args.backup_archive else ' # No backup archive was created (-B)'}

                remove() {{
                    echo "Removing  $1"
                    rm "$1"
                }}
                remove_dir() {{
                    rmdir "$1" || echo "\\033[34mFailed to remove folder $1\\033[0m"
                }}
                if [ -n "$BACKUP_ARCHIVE" -a -f "$BACKUP_ARCHIVE" ]; then
                    restore() {{
                        echo "Restoring $1 from $BACKUP_ARCHIVE"
                        bsdtar -Uqxf "$BACKUP_ARCHIVE" "$1"
                    }}
                elif [ -n "${{PATCHDIR_LOSE_FILES-}}" ]; then
                    restore() {{
                        echo "Removing $1 \\033[31m[Previously existing file is lost]\\033[0m"
                        rm "$1"
                    }}
                elif ! grep -qE "restore\\s+([\\"'].+[\\"']|(?\\!script)\\S+\\s*(#.*)?\\$)" "$0"; then
                    : No files were overwritten
                else
                    echo "\\033[31mError: Cannot restore original files because no backup is available\\033[0m"
                    echo "Set PATCHDIR_LOSE_FILES=1 to remove changed files without restoring originals"
                    exit 66
                fi
                if [ "$1" = "-k" -o -n "$PATCHDIR_KEEP_BACKUP" ];
                    cleanup() {{
                        echo "Keeping $1"
                    }}
                else
                    cleanup() {{
                        echo "Cleaning up $1"
                        rm "$1"
                    }}
                fi

                {SCRIPT_TAG}
                # Restore Files #
                """))

            if operations:
                for cmd, path in operations:
                    if cmd not in SCRIPT_DIR_CMDS:
                        write_script(uninstall_script, cmd, path)

        backup_archive = None
        backup_archive_prepended = set()
        if args.backup_archive:
            if do_append:
                # Prepend old contents
                backup_archive_tmpname = args.backup_archive.with_name(args.backup_archive.name + ".tmp")
                if not args.dry_run:
                    backup_archive = ctx.enter_context(file_writer_ext(backup_archive_tmpname, args.backup_archive))
                else:
                    backup_archive = ctx.enter_context(file_writer_ext("/dev/null", args.backup_archive))
                with libarchive.file_reader(str(args.backup_archive)) as ar:
                    backup_archive_prepended.update(copy_all_entries(ar, backup_archive))
            else:
                if not args.dry_run:
                    backup_archive = ctx.enter_context(file_writer_ext(args.backup_archive))
                else:
                    backup_archive = ctx.enter_context(file_writer_ext("/dev/null", args.backup_archive))
            disk_rdr = ctx.enter_context(disk_reader())

        # Check consistency
        prev_restore_files = set()
        prev_remove_files = set()
        for op, path in operations:
            if op in SCRIPT_BACKUP_CMDS:
                if backup_archive and path not in backup_archive_prepended:
                    print("\033[34mWarn: {path} referenced in uninstall script but missing in backup archive\033[0m")
                prev_restore_files.add(path)
            elif op in SCRIPT_REMOVE_CMDS:
                prev_remove_files.add(path)
            elif op == "remove_dir":
                folders.add(path)

        # Open disk for writing
        if not args.dry_run:
            extract = ctx.enter_context(libarchive.extract.new_archive_write_disk(
                libarchive.extract.EXTRACT_TIME|libarchive.extract.EXTRACT_UNLINK))

        root = pathlib.PurePath('/')
        for entry in archive:
            if args.match:
                if not args.match.match('/'+entry.path):
                    continue

            epath = pathlib.Path(entry.path)

            if args.strip:
                epath = pathlib.Path(*epath.parts[args.strip:])

            if args.prefix:
                epath = args.prefix / epath

            if entry.isdir:
                folders |= makedirs(epath, args.dry_run)
            else:
                folders |= makedirs(epath.parent, args.dry_run)

                # Archive might have multiple versions of the same file.
                # Use the last one, but don't overwrite the backup with intermediate copies
                if epath not in files:
                    files.add(epath)
                    if epath.exists():
                        # Backup
                        if backup_archive:
                            print(f"Backing up {epath} to {args.backup_archive}")
                            # Skip if an older version in archive or it originally didn't exist
                            if epath not in backup_archive_prepended and epath not in prev_remove_files:
                                disk_rdr.add_file_to_archive(backup_archive, epath)
                        if uninstall_script and epath not in operations:
                            write_script(uninstall_script, "restore", epath)
                    elif uninstall_script:
                        write_script(uninstall_script, "remove", epath)

                print(f"Extracting {epath}")
                if not args.dry_run:
                    extract_entry(entry, extract, epath)

        if do_append and backup_archive and not args.dry_run:
            os.rename(backup_archive_tmpname, args.backup_archive)

        if uninstall_script and folders:
            uninstall_script.write("\n# Remove folders #\n")

            if folders:
                for dname in sorted(folders, key=lambda x: len(x.parts), reverse=True):
                    write_script(uninstall_script, "remove_dir", dname)

        if uninstall_script:
            uninstall_script.write(f"\n# Remove script #\n")
            write_script(uninstall_script, "cleanup", args.uninstall_script)
            if args.backup_archive:
                write_script(uninstall_script, "cleanup", args.backup_archive)

    return 0


if __name__ == "__main__":
    import sys
    sys.exit(main(sys.argv))