# Copyright 2016 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.

"""Manage various config files."""

import configparser
import functools
import itertools
import os
import shlex
import sys

_path = os.path.realpath(__file__ + '/../..')
if sys.path[0] != _path:
    sys.path.insert(0, _path)
del _path

# pylint: disable=wrong-import-position
import rh.hooks
import rh.shell


class Error(Exception):
    """Base exception class."""


class ValidationError(Error):
    """Config file has unknown sections/keys or other values."""


# Sentinel so we can handle None-vs-unspecified.
_UNSET = object()


class RawConfigParser(configparser.RawConfigParser):
    """Like RawConfigParser but with some default helpers."""

    # pylint doesn't like it when we extend the API.
    # pylint: disable=arguments-differ

    def options(self, section, default=_UNSET):
        """Return the options in |section|.

        Args:
          section: The section to look up.
          default: What to return if |section| does not exist.
        """
        try:
            return configparser.RawConfigParser.options(self, section)
        except configparser.NoSectionError:
            if default is not _UNSET:
                return default
            raise

    def items(self, section=_UNSET, default=_UNSET):
        """Return a list of (key, value) tuples for the options in |section|."""
        if section is _UNSET:
            return super().items()

        try:
            return configparser.RawConfigParser.items(self, section)
        except configparser.NoSectionError:
            if default is not _UNSET:
                return default
            raise


class PreUploadConfig(object):
    """A single (abstract) config used for `repo upload` hooks."""

    CUSTOM_HOOKS_SECTION = 'Hook Scripts'
    BUILTIN_HOOKS_SECTION = 'Builtin Hooks'
    BUILTIN_HOOKS_OPTIONS_SECTION = 'Builtin Hooks Options'
    BUILTIN_HOOKS_EXCLUDE_SECTION = 'Builtin Hooks Exclude Paths'
    TOOL_PATHS_SECTION = 'Tool Paths'
    OPTIONS_SECTION = 'Options'
    VALID_SECTIONS = {
        CUSTOM_HOOKS_SECTION,
        BUILTIN_HOOKS_SECTION,
        BUILTIN_HOOKS_OPTIONS_SECTION,
        BUILTIN_HOOKS_EXCLUDE_SECTION,
        TOOL_PATHS_SECTION,
        OPTIONS_SECTION,
    }

    OPTION_IGNORE_MERGED_COMMITS = 'ignore_merged_commits'
    VALID_OPTIONS = {OPTION_IGNORE_MERGED_COMMITS}

    def __init__(self, config=None, source=None):
        """Initialize.

        Args:
          config: A configparse.ConfigParser instance.
          source: Where this config came from. This is used in error messages to
              facilitate debugging. It is not necessarily a valid path.
        """
        self.config = config if config else RawConfigParser()
        self.source = source
        if config:
            self._validate()

    @property
    def custom_hooks(self):
        """List of custom hooks to run (their keys/names)."""
        return self.config.options(self.CUSTOM_HOOKS_SECTION, [])

    def custom_hook(self, hook):
        """The command to execute for |hook|."""
        return shlex.split(self.config.get(
            self.CUSTOM_HOOKS_SECTION, hook, fallback=''))

    @property
    def builtin_hooks(self):
        """List of all enabled builtin hooks (their keys/names)."""
        return [k for k, v in self.config.items(self.BUILTIN_HOOKS_SECTION, ())
                if rh.shell.boolean_shell_value(v, None)]

    def builtin_hook_option(self, hook):
        """The options to pass to |hook|."""
        return shlex.split(self.config.get(
            self.BUILTIN_HOOKS_OPTIONS_SECTION, hook, fallback=''))

    def builtin_hook_exclude_paths(self, hook):
        """List of paths for which |hook| should not be executed."""
        return shlex.split(self.config.get(
            self.BUILTIN_HOOKS_EXCLUDE_SECTION, hook, fallback=''))

    @property
    def tool_paths(self):
        """List of all tool paths."""
        return dict(self.config.items(self.TOOL_PATHS_SECTION, ()))

    def callable_custom_hooks(self):
        """Yield a CallableHook for each hook to be executed."""
        scope = rh.hooks.ExclusionScope([])
        for hook in self.custom_hooks:
            options = rh.hooks.HookOptions(hook,
                                           self.custom_hook(hook),
                                           self.tool_paths)
            func = functools.partial(rh.hooks.check_custom, options=options)
            yield rh.hooks.CallableHook(hook, func, scope)

    def callable_builtin_hooks(self):
        """Yield a CallableHook for each hook to be executed."""
        scope = rh.hooks.ExclusionScope([])
        for hook in self.builtin_hooks:
            options = rh.hooks.HookOptions(hook,
                                           self.builtin_hook_option(hook),
                                           self.tool_paths)
            func = functools.partial(rh.hooks.BUILTIN_HOOKS[hook],
                                     options=options)
            scope = rh.hooks.ExclusionScope(
                self.builtin_hook_exclude_paths(hook))
            yield rh.hooks.CallableHook(hook, func, scope)

    @property
    def ignore_merged_commits(self):
        """Whether to skip hooks for merged commits."""
        return rh.shell.boolean_shell_value(
            self.config.get(self.OPTIONS_SECTION,
                            self.OPTION_IGNORE_MERGED_COMMITS, fallback=None),
            False)

    def update(self, preupload_config):
        """Merge settings from |preupload_config| into ourself."""
        self.config.read_dict(preupload_config.config)

    def _validate(self):
        """Run consistency checks on the config settings."""
        config = self.config

        # Reject unknown sections.
        bad_sections = set(config.sections()) - self.VALID_SECTIONS
        if bad_sections:
            raise ValidationError(
                f'{self.source}: unknown sections: {bad_sections}')

        # Reject blank custom hooks.
        for hook in self.custom_hooks:
            if not config.get(self.CUSTOM_HOOKS_SECTION, hook):
                raise ValidationError(
                    f'{self.source}: custom hook "{hook}" cannot be blank')

        # Reject unknown builtin hooks.
        valid_builtin_hooks = set(rh.hooks.BUILTIN_HOOKS.keys())
        if config.has_section(self.BUILTIN_HOOKS_SECTION):
            hooks = set(config.options(self.BUILTIN_HOOKS_SECTION))
            bad_hooks = hooks - valid_builtin_hooks
            if bad_hooks:
                raise ValidationError(
                    f'{self.source}: unknown builtin hooks: {bad_hooks}')
        elif config.has_section(self.BUILTIN_HOOKS_OPTIONS_SECTION):
            raise ValidationError('Builtin hook options specified, but missing '
                                  'builtin hook settings')

        if config.has_section(self.BUILTIN_HOOKS_OPTIONS_SECTION):
            hooks = set(config.options(self.BUILTIN_HOOKS_OPTIONS_SECTION))
            bad_hooks = hooks - valid_builtin_hooks
            if bad_hooks:
                raise ValidationError(
                    f'{self.source}: unknown builtin hook options: {bad_hooks}')

        # Verify hooks are valid shell strings.
        for hook in self.custom_hooks:
            try:
                self.custom_hook(hook)
            except ValueError as e:
                raise ValidationError(
                    f'{self.source}: hook "{hook}" command line is invalid: {e}'
                ) from e

        # Verify hook options are valid shell strings.
        for hook in self.builtin_hooks:
            try:
                self.builtin_hook_option(hook)
            except ValueError as e:
                raise ValidationError(
                    f'{self.source}: hook options "{hook}" are invalid: {e}'
                ) from e

        # Reject unknown tools.
        valid_tools = set(rh.hooks.TOOL_PATHS.keys())
        if config.has_section(self.TOOL_PATHS_SECTION):
            tools = set(config.options(self.TOOL_PATHS_SECTION))
            bad_tools = tools - valid_tools
            if bad_tools:
                raise ValidationError(
                    f'{self.source}: unknown tools: {bad_tools}')

        # Reject unknown options.
        if config.has_section(self.OPTIONS_SECTION):
            options = set(config.options(self.OPTIONS_SECTION))
            bad_options = options - self.VALID_OPTIONS
            if bad_options:
                raise ValidationError(
                    f'{self.source}: unknown options: {bad_options}')


class PreUploadFile(PreUploadConfig):
    """A single config (file) used for `repo upload` hooks.

    This is an abstract class that requires subclasses to define the FILENAME
    constant.

    Attributes:
      path: The path of the file.
    """
    FILENAME = None

    def __init__(self, path):
        """Initialize.

        Args:
          path: The config file to load.
        """
        super().__init__(source=path)

        self.path = path
        try:
            self.config.read(path)
        except configparser.ParsingError as e:
            raise ValidationError(f'{path}: {e}') from e

        self._validate()

    @classmethod
    def from_paths(cls, paths):
        """Search for files within paths that matches the class FILENAME.

        Args:
          paths: List of directories to look for config files.

        Yields:
          For each valid file found, an instance is created and returned.
        """
        for path in paths:
            path = os.path.join(path, cls.FILENAME)
            if os.path.exists(path):
                yield cls(path)


class LocalPreUploadFile(PreUploadFile):
    """A single config file for a project (PREUPLOAD.cfg)."""
    FILENAME = 'PREUPLOAD.cfg'

    def _validate(self):
        super()._validate()

        # Reject Exclude Paths section for local config.
        if self.config.has_section(self.BUILTIN_HOOKS_EXCLUDE_SECTION):
            raise ValidationError(
                f'{self.path}: [{self.BUILTIN_HOOKS_EXCLUDE_SECTION}] is not '
                'valid in local files')


class GlobalPreUploadFile(PreUploadFile):
    """A single config file for a repo (GLOBAL-PREUPLOAD.cfg)."""
    FILENAME = 'GLOBAL-PREUPLOAD.cfg'


class PreUploadSettings(PreUploadConfig):
    """Settings for `repo upload` hooks.

    This encompasses multiple config files and provides the final (merged)
    settings for a particular project.
    """

    def __init__(self, paths=('',), global_paths=()):
        """Initialize.

        All the config files found will be merged together in order.

        Args:
          paths: The directories to look for config files.
          global_paths: The directories to look for global config files.
        """
        super().__init__()

        self.paths = []
        for config in itertools.chain(
                GlobalPreUploadFile.from_paths(global_paths),
                LocalPreUploadFile.from_paths(paths)):
            self.paths.append(config.path)
            self.update(config)


        # We validated configs in isolation, now do one final pass altogether.
        self.source = '{' + '|'.join(self.paths) + '}'
        self._validate()