import sys
import os
import warnings
from contextlib import contextmanager
from pathlib import Path
from typing import Iterator, IO, Optional
from enum import Enum


try:
    import curses
except ImportError:
    curses = None  # Compiled w/o curses

from .compat import is_windows
from .config import DEFAULT_CONFIG_DIR, Config, ConfigFileError
from .encoding import UTF8

from .utils import repr_dict


class Levels(str, Enum):
    WARNING = 'warning'
    ERROR = 'error'


DISPLAY_THRESHOLDS = {
    Levels.WARNING: 2,
    Levels.ERROR: float('inf'),  # Never hide errors.
}


class Environment:
    """
    Information about the execution context
    (standard streams, config directory, etc).

    By default, it represents the actual environment.
    All of the attributes can be overwritten though, which
    is used by the test suite to simulate various scenarios.

    """
    is_windows: bool = is_windows
    config_dir: Path = DEFAULT_CONFIG_DIR
    stdin: Optional[IO] = sys.stdin  # `None` when closed fd (#791)
    stdin_isatty: bool = stdin.isatty() if stdin else False
    stdin_encoding: str = None
    stdout: IO = sys.stdout
    stdout_isatty: bool = stdout.isatty()
    stdout_encoding: str = None
    stderr: IO = sys.stderr
    stderr_isatty: bool = stderr.isatty()
    colors = 256
    program_name: str = 'http'
    if not is_windows:
        if curses:
            try:
                curses.setupterm()
                colors = curses.tigetnum('colors')
            except curses.error:
                pass
    else:
        # noinspection PyUnresolvedReferences
        import colorama.initialise
        stdout = colorama.initialise.wrap_stream(
            stdout, convert=None, strip=None,
            autoreset=True, wrap=True
        )
        stderr = colorama.initialise.wrap_stream(
            stderr, convert=None, strip=None,
            autoreset=True, wrap=True
        )
        del colorama

    def __init__(self, devnull=None, **kwargs):
        """
        Use keyword arguments to overwrite
        any of the class attributes for this instance.

        """
        assert all(hasattr(type(self), attr) for attr in kwargs.keys())
        self.__dict__.update(**kwargs)

        # The original STDERR unaffected by --quiet’ing.
        self._orig_stderr = self.stderr
        self._devnull = devnull

        # Keyword arguments > stream.encoding > default UTF-8
        if self.stdin and self.stdin_encoding is None:
            self.stdin_encoding = getattr(
                self.stdin, 'encoding', None) or UTF8
        if self.stdout_encoding is None:
            actual_stdout = self.stdout
            if is_windows:
                # noinspection PyUnresolvedReferences
                from colorama import AnsiToWin32
                if isinstance(self.stdout, AnsiToWin32):
                    # noinspection PyUnresolvedReferences
                    actual_stdout = self.stdout.wrapped
            self.stdout_encoding = getattr(
                actual_stdout, 'encoding', None) or UTF8

        self.quiet = kwargs.pop('quiet', 0)

    def __str__(self):
        defaults = dict(type(self).__dict__)
        actual = dict(defaults)
        actual.update(self.__dict__)
        actual['config'] = self.config
        return repr_dict({
            key: value
            for key, value in actual.items()
            if not key.startswith('_')
        })

    def __repr__(self):
        return f'<{type(self).__name__} {self}>'

    _config: Config = None

    @property
    def config(self) -> Config:
        config = self._config
        if not config:
            self._config = config = Config(directory=self.config_dir)
            if not config.is_new():
                try:
                    config.load()
                except ConfigFileError as e:
                    self.log_error(e, level='warning')
        return config

    @property
    def devnull(self) -> IO:
        if self._devnull is None:
            self._devnull = open(os.devnull, 'w+')
        return self._devnull

    @contextmanager
    def as_silent(self) -> Iterator[None]:
        original_stdout = self.stdout
        original_stderr = self.stderr

        try:
            self.stdout = self.devnull
            self.stderr = self.devnull
            yield
        finally:
            self.stdout = original_stdout
            self.stderr = original_stderr

    def log_error(self, msg: str, level: Levels = Levels.ERROR) -> None:
        if self.stdout_isatty and self.quiet >= DISPLAY_THRESHOLDS[level]:
            stderr = self.stderr  # Not directly /dev/null, since stderr might be mocked
        else:
            stderr = self._orig_stderr

        stderr.write(f'\n{self.program_name}: {level}: {msg}\n\n')

    def apply_warnings_filter(self) -> None:
        if self.quiet >= DISPLAY_THRESHOLDS[Levels.WARNING]:
            warnings.simplefilter("ignore")