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

"""
import os
import sys
import re
import json
import mimetypes
import getpass
from io import BytesIO
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 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.
                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.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.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