"""Parsing and processing of CLI input (args, auth credentials, files, stdin).

"""
import os
import sys
import re
import json
import mimetypes
from getpass import getpass
from io import BytesIO
#noinspection PyCompatibility
from argparse import ArgumentParser, ArgumentTypeError, ArgumentError

try:
    from collections import OrderedDict
except ImportError:
    OrderedDict = dict

# TODO: Use MultiDict for headers once added to `requests`.
# https://github.com/jkbr/httpie/issues/130
from requests.structures import CaseInsensitiveDict

from .compat import urlsplit, str
from .sessions import VALID_SESSION_NAME_PATTERN


HTTP_POST = 'POST'
HTTP_GET = 'GET'
HTTP = 'http://'
HTTPS = 'https://'


# Various separators used in args
SEP_HEADERS = ':'
SEP_CREDENTIALS = ':'
SEP_PROXY = ':'
SEP_DATA = '='
SEP_DATA_RAW_JSON = ':='
SEP_FILES = '@'
SEP_QUERY = '=='

# Separators that become request data
SEP_GROUP_DATA_ITEMS = frozenset([
    SEP_DATA,
    SEP_DATA_RAW_JSON,
    SEP_FILES
])

# Separators allowed in ITEM arguments
SEP_GROUP_ITEMS = frozenset([
    SEP_HEADERS,
    SEP_QUERY,
    SEP_DATA,
    SEP_DATA_RAW_JSON,
    SEP_FILES
])


# Output options
OUT_REQ_HEAD = 'H'
OUT_REQ_BODY = 'B'
OUT_RESP_HEAD = 'h'
OUT_RESP_BODY = 'b'

OUTPUT_OPTIONS = frozenset([
    OUT_REQ_HEAD,
    OUT_REQ_BODY,
    OUT_RESP_HEAD,
    OUT_RESP_BODY
])

# Pretty
PRETTY_MAP = {
    'all': ['format', 'colors'],
    'colors': ['colors'],
    'format': ['format'],
    'none': []
}
PRETTY_STDOUT_TTY_ONLY = object()


# Defaults
OUTPUT_OPTIONS_DEFAULT = OUT_RESP_HEAD + OUT_RESP_BODY
OUTPUT_OPTIONS_DEFAULT_STDOUT_REDIRECTED = OUT_RESP_BODY


class Parser(ArgumentParser):
    """Adds additional logic to `argparse.ArgumentParser`.

    Handles all input (CLI args, file args, stdin), applies defaults,
    and performs extra validation.

    """

    def __init__(self, *args, **kwargs):
        kwargs['add_help'] = False
        super(Parser, self).__init__(*args, **kwargs)

    #noinspection PyMethodOverriding
    def parse_args(self, env, args=None, namespace=None):

        self.env = env
        self.args, no_options = super(Parser, self)\
            .parse_known_args(args, namespace)

        if self.args.debug:
            self.args.traceback = True

        # Arguments processing and environment setup.
        self._apply_no_options(no_options)
        self._apply_config()
        self._validate_download_options()
        self._setup_standard_streams()
        self._process_output_options()
        self._process_pretty_options()
        self._guess_method()
        self._parse_items()
        if not self.args.ignore_stdin and not env.stdin_isatty:
            self._body_from_file(self.env.stdin)
        if not (self.args.url.startswith((HTTP, HTTPS))):
            # Default to 'https://' if invoked as `https args`.
            scheme = HTTPS if self.env.progname == 'https' else HTTP
            self.args.url = scheme + self.args.url
        self._process_auth()

        return self.args

    # noinspection PyShadowingBuiltins
    def _print_message(self, message, file=None):
        # Sneak in our stderr/stdout.
        file = {
            sys.stdout: self.env.stdout,
            sys.stderr: self.env.stderr,
            None: self.env.stderr
        }.get(file, file)

        super(Parser, self)._print_message(message, file)

    def _setup_standard_streams(self):
        """
        Modify `env.stdout` and `env.stdout_isatty` based on args, if needed.

        """
        if not self.env.stdout_isatty and self.args.output_file:
            self.error('Cannot use --output, -o with redirected output.')

        # FIXME: Come up with a cleaner solution.
        if self.args.download:

            if not self.env.stdout_isatty:
                # Use stdout as tge download output file.
                self.args.output_file = self.env.stdout

            # With `--download`, we write everything that would normally go to
            # `stdout` to `stderr` instead. Let's replace the stream so that
            # we don't have to use many `if`s throughout the codebase.
            # The response body will be treated separately.
            self.env.stdout = self.env.stderr
            self.env.stdout_isatty = self.env.stderr_isatty

        elif self.args.output_file:
            # When not `--download`ing, then `--output` simply replaces
            # `stdout`. The file is opened for appending, which isn't what
            # we want in this case.
            self.args.output_file.seek(0)
            self.args.output_file.truncate()

            self.env.stdout = self.args.output_file
            self.env.stdout_isatty = False

    def _apply_config(self):
        if (not self.args.json
                and self.env.config.implicit_content_type == 'form'):
            self.args.form = True

    def _process_auth(self):
        """
        If only a username provided via --auth, then ask for a password.
        Or, take credentials from the URL, if provided.

        """
        url = urlsplit(self.args.url)

        if self.args.auth:
            if not self.args.auth.has_password():
                # Stdin already read (if not a tty) so it's save to prompt.
                if self.args.ignore_stdin:
                    self.error('Unable to prompt for passwords because'
                               ' --ignore-stdin is set.')
                self.args.auth.prompt_password(url.netloc)

        elif url.username is not None:
            # Handle http://username:password@hostname/
            username, password = url.username, url.password
            self.args.auth = AuthCredentials(
                key=username,
                value=password,
                sep=SEP_CREDENTIALS,
                orig=SEP_CREDENTIALS.join([username, password])
            )

    def _apply_no_options(self, no_options):
        """For every `--no-OPTION` in `no_options`, set `args.OPTION` to
        its default value. This allows for un-setting of options, e.g.,
        specified in config.

        """
        invalid = []

        for option in no_options:
            if not option.startswith('--no-'):
                invalid.append(option)
                continue

            # --no-option => --option
            inverted = '--' + option[5:]
            for action in self._actions:
                if inverted in action.option_strings:
                    setattr(self.args, action.dest, action.default)
                    break
            else:
                invalid.append(option)

        if invalid:
            msg = 'unrecognized arguments: %s'
            self.error(msg % ' '.join(invalid))

    def _body_from_file(self, fd):
        """There can only be one source of request data.

        Bytes are always read.

        """
        if self.args.data:
            self.error('Request body (from stdin or a file) and request '
                       'data (key=value) cannot be mixed.')
        self.args.data = getattr(fd, 'buffer', fd).read()

    def _guess_method(self):
        """Set `args.method` if not specified to either POST or GET
        based on whether the request has data or not.

        """
        if self.args.method is None:
            # Invoked as `http URL'.
            assert not self.args.items
            if not self.args.ignore_stdin and not self.env.stdin_isatty:
                self.args.method = HTTP_POST
            else:
                self.args.method = HTTP_GET

        # FIXME: False positive, e.g., "localhost" matches but is a valid URL.
        elif not re.match('^[a-zA-Z]+$', self.args.method):
            # Invoked as `http URL item+'. The URL is now in `args.method`
            # and the first ITEM is now incorrectly in `args.url`.
            try:
                # Parse the URL as an ITEM and store it as the first ITEM arg.
                self.args.items.insert(
                    0,
                    KeyValueArgType(*SEP_GROUP_ITEMS).__call__(self.args.url)
                )

            except ArgumentTypeError as e:
                if self.args.traceback:
                    raise
                self.error(e.message)

            else:
                # Set the URL correctly
                self.args.url = self.args.method
                # Infer the method
                has_data = (
                    (not self.args.ignore_stdin and
                     not self.env.stdin_isatty) or any(
                        item.sep in SEP_GROUP_DATA_ITEMS
                        for item in self.args.items
                    )
                )
                self.args.method = HTTP_POST if has_data else HTTP_GET

    def _parse_items(self):
        """Parse `args.items` into `args.headers`, `args.data`, `args.params`,
         and `args.files`.

        """
        self.args.headers = CaseInsensitiveDict()
        self.args.data = ParamDict() if self.args.form else OrderedDict()
        self.args.files = OrderedDict()
        self.args.params = ParamDict()

        try:
            parse_items(items=self.args.items,
                        headers=self.args.headers,
                        data=self.args.data,
                        files=self.args.files,
                        params=self.args.params)
        except ParseError as e:
            if self.args.traceback:
                raise
            self.error(e.message)

        if self.args.files and not self.args.form:
            # `http url @/path/to/file`
            file_fields = list(self.args.files.keys())
            if file_fields != ['']:
                self.error(
                    'Invalid file fields (perhaps you meant --form?): %s'
                    % ','.join(file_fields))

            fn, fd = self.args.files['']
            self.args.files = {}

            self._body_from_file(fd)

            if 'Content-Type' not in self.args.headers:
                mime, encoding = mimetypes.guess_type(fn, strict=False)
                if mime:
                    content_type = mime
                    if encoding:
                        content_type = '%s; charset=%s' % (mime, encoding)
                    self.args.headers['Content-Type'] = content_type

    def _process_output_options(self):
        """Apply defaults to output options, or validate the provided ones.

        The default output options are stdout-type-sensitive.

        """
        if not self.args.output_options:
            self.args.output_options = (
                OUTPUT_OPTIONS_DEFAULT
                if self.env.stdout_isatty
                else OUTPUT_OPTIONS_DEFAULT_STDOUT_REDIRECTED
            )

        unknown_output_options = set(self.args.output_options) - OUTPUT_OPTIONS
        if unknown_output_options:
            self.error(
                'Unknown output options: %s' % ','.join(unknown_output_options)
            )

        if self.args.download and OUT_RESP_BODY in self.args.output_options:
            # Response body is always downloaded with --download and it goes
            # through a different routine, so we remove it.
            self.args.output_options = str(
                set(self.args.output_options) - set(OUT_RESP_BODY))

    def _process_pretty_options(self):
        if self.args.prettify == PRETTY_STDOUT_TTY_ONLY:
            self.args.prettify = PRETTY_MAP[
                'all' if self.env.stdout_isatty else 'none']
        elif self.args.prettify and self.env.is_windows:
            self.error('Only terminal output can be colorized on Windows.')
        else:
            # noinspection PyTypeChecker
            self.args.prettify = PRETTY_MAP[self.args.prettify]

    def _validate_download_options(self):
        if not self.args.download:
            if self.args.download_resume:
                self.error('--continue only works with --download')
        if self.args.download_resume and not (
                self.args.download and self.args.output_file):
            self.error('--continue requires --output to be specified')


class ParseError(Exception):
    pass


class KeyValue(object):
    """Base key-value pair parsed from CLI."""

    def __init__(self, key, value, sep, orig):
        self.key = key
        self.value = value
        self.sep = sep
        self.orig = orig

    def __eq__(self, other):
        return self.__dict__ == other.__dict__


class SessionNameValidator(object):

    def __init__(self, error_message):
        self.error_message = error_message

    def __call__(self, value):
        # Session name can be a path or just a name.
        if (os.path.sep not in value
                and not VALID_SESSION_NAME_PATTERN.search(value)):
            raise ArgumentError(None, self.error_message)
        return value


class KeyValueArgType(object):
    """A key-value pair argument type used with `argparse`.

    Parses a key-value arg and constructs a `KeyValue` instance.
    Used for headers, form data, and other key-value pair types.

    """

    key_value_class = KeyValue

    def __init__(self, *separators):
        self.separators = separators

    def __call__(self, string):
        """Parse `string` and return `self.key_value_class()` instance.

        The best of `self.separators` is determined (first found, longest).
        Back slash escaped characters aren't considered as separators
        (or parts thereof). Literal back slash characters have to be escaped
        as well (r'\\').

        """

        class Escaped(str):
            """Represents an escaped character."""

        def tokenize(s):
            """Tokenize `s`. There are only two token types - strings
            and escaped characters:

            tokenize(r'foo\=bar\\baz')
            => ['foo', Escaped('='), 'bar', Escaped('\\'), 'baz']

            """
            tokens = ['']
            esc = False
            for c in s:
                if esc:
                    tokens.extend([Escaped(c), ''])
                    esc = False
                else:
                    if c == '\\':
                        esc = True
                    else:
                        tokens[-1] += c
            return tokens

        tokens = tokenize(string)

        # Sorting by length ensures that the longest one will be
        # chosen as it will overwrite any shorter ones starting
        # at the same position in the `found` dictionary.
        separators = sorted(self.separators, key=len)

        for i, token in enumerate(tokens):

            if isinstance(token, Escaped):
                continue

            found = {}
            for sep in separators:
                pos = token.find(sep)
                if pos != -1:
                    found[pos] = sep

            if found:
                # Starting first, longest separator found.
                sep = found[min(found.keys())]

                key, value = token.split(sep, 1)

                # Any preceding tokens are part of the key.
                key = ''.join(tokens[:i]) + key

                # Any following tokens are part of the value.
                value += ''.join(tokens[i + 1:])

                break

        else:
            raise ArgumentTypeError(
                '"%s" is not a valid value' % string)

        return self.key_value_class(
            key=key, value=value, sep=sep, orig=string)


class AuthCredentials(KeyValue):
    """Represents parsed credentials."""

    def _getpass(self, prompt):
        # To allow mocking.
        return getpass.getpass(prompt)

    def has_password(self):
        return self.value is not None

    def prompt_password(self, host):
        try:
            self.value = self._getpass(
                'http: password for %s@%s: ' % (self.key, host))
        except (EOFError, KeyboardInterrupt):
            sys.stderr.write('\n')
            sys.exit(0)


class AuthCredentialsArgType(KeyValueArgType):
    """A key-value arg type that parses credentials."""

    key_value_class = AuthCredentials

    def __call__(self, string):
        """Parse credentials from `string`.

        ("username" or "username:password").

        """
        try:
            return super(AuthCredentialsArgType, self).__call__(string)
        except ArgumentTypeError:
            # No password provided, will prompt for it later.
            return self.key_value_class(
                key=string,
                value=None,
                sep=SEP_CREDENTIALS,
                orig=string
            )


class ParamDict(OrderedDict):
    """Multi-value dict for URL parameters and form data."""

    #noinspection PyMethodOverriding
    def __setitem__(self, key, value):
        """ If `key` is assigned more than once, `self[key]` holds a
        `list` of all the values.

        This allows having multiple fields with the same name in form
        data and URL params.

        """
        if key not in self:
            super(ParamDict, self).__setitem__(key, value)
        else:
            if not isinstance(self[key], list):
                super(ParamDict, self).__setitem__(key, [self[key]])
            self[key].append(value)


def parse_items(items, data=None, headers=None, files=None, params=None):
    """Parse `KeyValue` `items` into `data`, `headers`, `files`,
    and `params`.

    """
    if headers is None:
        headers = CaseInsensitiveDict()
    if data is None:
        data = OrderedDict()
    if files is None:
        files = OrderedDict()
    if params is None:
        params = ParamDict()

    for item in items:

        value = item.value
        key = item.key

        if item.sep == SEP_HEADERS:
            target = headers
        elif item.sep == SEP_QUERY:
            target = params
        elif item.sep == SEP_FILES:
            try:
                with open(os.path.expanduser(value), 'rb') as f:
                    value = (os.path.basename(value),
                             BytesIO(f.read()))
            except IOError as e:
                raise ParseError(
                    'Invalid argument "%s": %s' % (item.orig, e))
            target = files

        elif item.sep in [SEP_DATA, SEP_DATA_RAW_JSON]:
            if item.sep == SEP_DATA_RAW_JSON:
                try:
                    value = json.loads(item.value)
                except ValueError:
                    raise ParseError('"%s" is not valid JSON' % item.orig)
            target = data

        else:
            raise TypeError(item)

        target[key] = value

    return headers, data, files, params
