#!/usr/bin/env python3
#
# Copyright OpenEmbedded Contributors
#
# SPDX-License-Identifier: MIT
#

import argparse
import os
import re
import sys

from collections import defaultdict
from concurrent.futures import ThreadPoolExecutor
from dataclasses import dataclass
from pathlib import Path

if sys.version_info < (3, 8, 0):
    raise RuntimeError("Sorry, python 3.8.0 or later is required for this script.")

SSTATE_PREFIX = "sstate:"
SSTATE_EXTENSION = ".tar.zst"
# SSTATE_EXTENSION = ".tgz"
# .siginfo.done files are mentioned in the original script?
SSTATE_SUFFIXES = (
    SSTATE_EXTENSION,
    f"{SSTATE_EXTENSION}.siginfo",
    f"{SSTATE_EXTENSION}.done",
)

RE_SSTATE_PKGSPEC = re.compile(
    rf"""sstate:(?P<pn>[^:]*):
         (?P<package_target>[^:]*):
         (?P<pv>[^:]*):
         (?P<pr>[^:]*):
         (?P<sstate_pkgarch>[^:]*):
         (?P<sstate_version>[^_]*):
         (?P<bb_unihash>[^_]*)_
         (?P<bb_task>[^:]*)
         (?P<ext>({"|".join([re.escape(s) for s in SSTATE_SUFFIXES])}))$""",
    re.X,
)


# Really we'd like something like a Path subclass which implements a stat
# cache here, unfortunately there's no good way to do that transparently
# (yet); see:
#
# https://github.com/python/cpython/issues/70219
# https://discuss.python.org/t/make-pathlib-extensible/3428/77
@dataclass
class SstateEntry:
    """Class for keeping track of an entry in sstate-cache."""

    path: Path
    match: re.Match
    stat_result: os.stat_result = None

    def __hash__(self):
        return self.path.__hash__()

    def __getattr__(self, name):
        return self.match.group(name)


# this is what's in the original script; as far as I can tell, it's an
# implementation artefact which we don't need?
def find_archs():
    # all_archs
    builder_arch = os.uname().machine

    # FIXME
    layer_paths = [Path("../..")]

    tune_archs = set()
    re_tune = re.compile(r'AVAILTUNES .*=.*"(.*)"')
    for path in layer_paths:
        for tunefile in [
            p for p in path.glob("meta*/conf/machine/include/**/*") if p.is_file()
        ]:
            with open(tunefile) as f:
                for line in f:
                    m = re_tune.match(line)
                    if m:
                        tune_archs.update(m.group(1).split())

    # all_machines
    machine_archs = set()
    for path in layer_paths:
        for machine_file in path.glob("meta*/conf/machine/*.conf"):
            machine_archs.add(machine_file.parts[-1][:-5])

    extra_archs = set()
    all_archs = (
        set(
            arch.replace("-", "_")
            for arch in machine_archs | tune_archs | set(["allarch", builder_arch])
        )
        | extra_archs
    )

    print(all_archs)


# again, not needed?
def find_tasks():
    print(set([p.bb_task for p in paths]))


def collect_sstate_paths(args):
    def scandir(path, paths):
        # Assume everything is a directory; by not checking we avoid needing an
        # additional stat which is potentially a synchronous roundtrip over NFS
        try:
            for p in path.iterdir():
                filename = p.parts[-1]
                if filename.startswith(SSTATE_PREFIX):
                    if filename.endswith(SSTATE_SUFFIXES):
                        m = RE_SSTATE_PKGSPEC.match(p.parts[-1])
                        assert m
                        paths.add(SstateEntry(p, m))
                    # ignore other things (includes things like lockfiles)
                else:
                    scandir(p, paths)

        except NotADirectoryError:
            pass

    paths = set()
    # TODO: parellise scandir
    scandir(Path(args.cache_dir), paths)

    def path_stat(p):
        p.stat_result = p.path.lstat()

    if args.remove_duplicated:
        # This is probably slightly performance negative on a local filesystem
        # when we interact with the GIL; over NFS it's a massive win.
        with ThreadPoolExecutor(max_workers=args.jobs) as executor:
            executor.map(path_stat, paths)

    return paths


def remove_by_stamps(args, paths):
    all_sums = set()
    for stamps_dir in args.stamps_dir:
        stamps_path = Path(stamps_dir)
        assert stamps_path.is_dir()
        re_sigdata = re.compile(r"do_.*\.sigdata\.([^.]*)")
        all_sums |= set(
            [
                re_sigdata.search(x.parts[-1]).group(1)
                for x in stamps_path.glob("*/*/*.do_*.sigdata.*")
            ]
        )
        re_setscene = re.compile(r"do_.*_setscene\.([^.]*)")
        all_sums |= set(
            [
                re_setscene.search(x.parts[-1]).group(1)
                for x in stamps_path.glob("*/*/*.do_*_setscene.*")
            ]
        )
    return [p for p in paths if p.bb_unihash not in all_sums]


def remove_duplicated(args, paths):
    # Skip populate_lic as it produces duplicates in a normal build
    #
    # 9ae16469e707 sstate-cache-management: skip populate_lic archives when removing duplicates
    valid_paths = [p for p in paths if p.bb_task != "populate_lic"]

    keep = dict()
    remove = list()
    for p in valid_paths:
        sstate_sig = ":".join([p.pn, p.sstate_pkgarch, p.bb_task, p.ext])
        if sstate_sig not in keep:
            keep[sstate_sig] = p
        elif p.stat_result.st_mtime > keep[sstate_sig].stat_result.st_mtime:
            remove.append(keep[sstate_sig])
            keep[sstate_sig] = p
        else:
            remove.append(p)

    return remove


def remove_orphans(args, paths):
    remove = list()
    pathsigs = defaultdict(list)
    for p in paths:
        sstate_sig = ":".join([p.pn, p.sstate_pkgarch, p.bb_task])
        pathsigs[sstate_sig].append(p)
    for k, v in pathsigs.items():
        if len([p for p in v if p.ext == SSTATE_EXTENSION]) == 0:
            remove.extend(v)
    return remove


def parse_arguments():
    parser = argparse.ArgumentParser(description="sstate cache management utility.")

    parser.add_argument(
        "--cache-dir",
        default=os.environ.get("SSTATE_CACHE_DIR"),
        help="""Specify sstate cache directory, will use the environment
            variable SSTATE_CACHE_DIR if it is not specified.""",
    )

    # parser.add_argument(
    #     "--extra-archs",
    #     help="""Specify list of architectures which should be tested, this list
    #         will be extended with native arch, allarch and empty arch. The
    #         script won't be trying to generate list of available archs from
    #         AVAILTUNES in tune files.""",
    # )

    # parser.add_argument(
    #     "--extra-layer",
    #     help="""Specify the layer which will be used for searching the archs,
    #         it will search the meta and meta-* layers in the top dir by
    #         default, and will search meta, meta-*, <layer1>, <layer2>,
    #         ...<layern> when specified. Use "," as the separator.
    #
    #         This is useless for --stamps-dir or when --extra-archs is used.""",
    # )

    parser.add_argument(
        "-d",
        "--remove-duplicated",
        action="store_true",
        help="""Remove the duplicated sstate cache files of one package, only
            the newest one will be kept. The duplicated sstate cache files
            of one package must have the same arch, which means sstate cache
            files with multiple archs are not considered duplicate.

            Conflicts with --stamps-dir.""",
    )

    parser.add_argument(
        "--remove-orphans",
        action="store_true",
        help=f"""Remove orphan siginfo files from the sstate cache, i.e. those
            where this is no {SSTATE_EXTENSION} file but there are associated
            tracking files.""",
    )

    parser.add_argument(
        "--stamps-dir",
        action="append",
        help="""Specify the build directory's stamps directories, the sstate
            cache file which IS USED by these build diretories will be KEPT,
            other sstate cache files in cache-dir will be removed. Can be
            specified multiple times for several directories.

            Conflicts with --remove-duplicated.""",
    )

    parser.add_argument(
        "-j", "--jobs", default=8, type=int, help="Run JOBS jobs in parallel."
    )

    # parser.add_argument(
    #     "-L",
    #     "--follow-symlink",
    #     action="store_true",
    #     help="Remove both the symbol link and the destination file, default: no.",
    # )

    parser.add_argument(
        "-n", "--dry-run", action="store_true", help="Don't execute, just go through the motions."
    )

    parser.add_argument(
        "-y",
        "--yes",
        action="store_true",
        help="""Automatic yes to prompts; assume "yes" as answer to all prompts
            and run non-interactively.""",
    )

    parser.add_argument(
        "-v", "--verbose", action="store_true", help="Explain what is being done."
    )

    parser.add_argument(
        "-D",
        "--debug",
        action="count",
        default=0,
        help="Show debug info, repeat for more debug info.",
    )

    args = parser.parse_args()
    if args.cache_dir is None or (
        not args.remove_duplicated and not args.stamps_dir and not args.remove_orphans
    ):
        parser.print_usage()
        sys.exit(1)

    return args


def main():
    args = parse_arguments()

    paths = collect_sstate_paths(args)
    if args.remove_duplicated:
        remove = remove_duplicated(args, paths)
    elif args.stamps_dir:
        remove = remove_by_stamps(args, paths)
    else:
        remove = list()

    if args.remove_orphans:
        remove = set(remove) | set(remove_orphans(args, paths))

    if args.debug >= 1:
        print("\n".join([str(p.path) for p in remove]))
    print(f"{len(remove)} out of {len(paths)} files will be removed!")
    if args.dry_run:
        return 0

    if not args.yes:
        print("Do you want to continue (y/n)?")
        confirm = input() in ("y", "Y")
    else:
        confirm = True
    if confirm:
        # TODO: parallelise remove
        for p in remove:
            p.path.unlink()


if __name__ == "__main__":
    main()