# Copyright (C) 2023 The Android Open Source Project
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import abc
import dataclasses
import enum
import logging
import os
from pathlib import Path
from typing import Callable, Iterable, TypeAlias

import util
from util import BuildType

Action: TypeAlias = Callable[[], None]
Verifier: TypeAlias = Callable[[], None]


def de_src(p: Path) -> str:
    return str(p.relative_to(util.get_top_dir()))


def src(p: str) -> Path:
    return util.get_top_dir().joinpath(p)


class InWorkspace(enum.Enum):
    """For a given file in the source tree, the counterpart in the symlink forest
    could be one of these kinds.
    """

    SYMLINK = enum.auto()
    NOT_UNDER_SYMLINK = enum.auto()
    UNDER_SYMLINK = enum.auto()
    OMISSION = enum.auto()

    @staticmethod
    def ws_counterpart(src_path: Path) -> Path:
        return util.get_out_dir().joinpath("soong/workspace").joinpath(de_src(src_path))

    def verifier(self, src_path: Path) -> Verifier:
        @skip_for(BuildType.SOONG_ONLY)
        def f():
            ws_path = InWorkspace.ws_counterpart(src_path)
            actual: InWorkspace | None = None
            if ws_path.is_symlink():
                actual = InWorkspace.SYMLINK
                if not ws_path.exists():
                    logging.warning("Dangling symlink %s", ws_path)
            elif not ws_path.exists():
                actual = InWorkspace.OMISSION
            else:
                for p in ws_path.parents:
                    if not p.is_relative_to(util.get_out_dir()):
                        actual = InWorkspace.NOT_UNDER_SYMLINK
                        break
                    if p.is_symlink():
                        actual = InWorkspace.UNDER_SYMLINK
                        break

            if self != actual:
                raise AssertionError(
                    f"{ws_path} expected {self.name} but got {actual.name}"
                )
            logging.info(f"VERIFIED {de_src(ws_path)} {self.name}")

        return f


def skip_for(*build_types: util.BuildType):
    def decorator(func: Callable[[], any]) -> Callable[[], any]:
        def wrapper():
            if util.CURRENT_BUILD_TYPE not in build_types:
                return func()

        return wrapper

    return decorator


@skip_for(BuildType.SOONG_ONLY)
def verify_symlink_forest_has_only_symlink_leaves():
    """Verifies that symlink forest has only symlinks or directories but no
    files except for merged BUILD.bazel files"""

    top_in_ws = InWorkspace.ws_counterpart(util.get_top_dir())

    for root, _, files in os.walk(top_in_ws, topdown=True, followlinks=False):
        for file in files:
            if file == "soong_build_mtime" and top_in_ws.samefile(root):
                continue
            f = Path(root).joinpath(file)
            if file != "BUILD.bazel" and not f.is_symlink():
                raise AssertionError(f"{f} unexpected in symlink forest")

    logging.info("VERIFIED Symlink Forest has no real files except BUILD.bazel")


@dataclasses.dataclass(frozen=True)
class CujStep:
    verb: str
    """a human-readable description"""
    apply_change: Action
    """user action(s) that are performed prior to a build attempt"""
    verify: Verifier = verify_symlink_forest_has_only_symlink_leaves
    """post-build assertions, i.e. tests.
  Should raise `Exception` for failures.
  """


class CujGroup(abc.ABC):
    """A sequence of steps to be performed, such that at the end of all steps the
    initial state of the source tree is attained.
    NO attempt is made to achieve atomicity programmatically. It is left as the
    responsibility of the user.
    """
    def __init__(self, description: str):
        self._desc = description

    @property
    def description(self)-> str:
        return self._desc

    @abc.abstractmethod
    def get_steps(self) -> Iterable[CujStep]:
        pass


def sequence(*vs: Callable[[], None]) -> Callable[[], None]:
    def f():
        for v in vs:
            v()

    return f