# -*- coding: utf-8 -*-
"""
    proxy.py
    ~~~~~~~~
    ⚡⚡⚡ Fast, Lightweight, Pluggable, TLS interception capable proxy server focused on
    Network monitoring, controls & Application development, testing, debugging.

    :copyright: (c) 2013-present by Abhinav Singh and contributors.
    :license: BSD, see LICENSE for more details.
"""
from typing import TypeVar, NamedTuple, Optional, Dict, Type, Tuple, List

from ...common.constants import DEFAULT_DISABLE_HEADERS, COLON, HTTP_1_0, SLASH, CRLF
from ...common.constants import WHITESPACE, HTTP_1_1, DEFAULT_HTTP_PORT
from ...common.utils import build_http_request, build_http_response, find_http_line, text_

from .url import Url
from .methods import httpMethods
from .chunk import ChunkParser, chunkParserStates

HttpParserStates = NamedTuple(
    'HttpParserStates', [
        ('INITIALIZED', int),
        ('LINE_RCVD', int),
        ('RCVING_HEADERS', int),
        ('HEADERS_COMPLETE', int),
        ('RCVING_BODY', int),
        ('COMPLETE', int),
    ],
)
httpParserStates = HttpParserStates(1, 2, 3, 4, 5, 6)

HttpParserTypes = NamedTuple(
    'HttpParserTypes', [
        ('REQUEST_PARSER', int),
        ('RESPONSE_PARSER', int),
    ],
)
httpParserTypes = HttpParserTypes(1, 2)


T = TypeVar('T', bound='HttpParser')


class HttpParser:
    """HTTP request/response parser.

    TODO: Make me zero-copy by using memoryview.
    Currently due to chunk/buffer handling we
    are not able to utilize memoryview
    efficiently.

    For this to happen we must store `buffer`
    as List[memoryview] instead of raw bytes and
    update parser to work accordingly.
    """

    def __init__(self, parser_type: int) -> None:
        self.type: int = parser_type
        self.state: int = httpParserStates.INITIALIZED
        self.host: Optional[bytes] = None
        self.port: Optional[int] = None
        self.path: Optional[bytes] = None
        self.method: Optional[bytes] = None
        self.code: Optional[bytes] = None
        self.reason: Optional[bytes] = None
        self.version: Optional[bytes] = None
        # Total size of raw bytes passed for parsing
        self.total_size: int = 0
        # Buffer to hold unprocessed bytes
        self.buffer: bytes = b''
        # Internal headers datastructure:
        # - Keys are lower case header names.
        # - Values are 2-tuple containing original
        #   header and it's value as received.
        self.headers: Dict[bytes, Tuple[bytes, bytes]] = {}
        self.body: Optional[bytes] = None
        self.chunk: Optional[ChunkParser] = None
        # Internal request line as a url structure
        self._url: Optional[Url] = None

    @classmethod
    def request(cls: Type[T], raw: bytes) -> T:
        parser = cls(httpParserTypes.REQUEST_PARSER)
        parser.parse(raw)
        return parser

    @classmethod
    def response(cls: Type[T], raw: bytes) -> T:
        parser = cls(httpParserTypes.RESPONSE_PARSER)
        parser.parse(raw)
        return parser

    def header(self, key: bytes) -> bytes:
        """Convenient method to return original header value from internal datastructure."""
        if key.lower() not in self.headers:
            raise KeyError('%s not found in headers', text_(key))
        return self.headers[key.lower()][1]

    def has_header(self, key: bytes) -> bool:
        """Returns true if header key was found in payload."""
        return key.lower() in self.headers

    def add_header(self, key: bytes, value: bytes) -> None:
        """Add/Update a header to internal data structure."""
        self.headers[key.lower()] = (key, value)

    def add_headers(self, headers: List[Tuple[bytes, bytes]]) -> None:
        """Add/Update multiple headers to internal data structure"""
        for (key, value) in headers:
            self.add_header(key, value)

    def del_header(self, header: bytes) -> None:
        """Delete a header from internal data structure."""
        if header.lower() in self.headers:
            del self.headers[header.lower()]

    def del_headers(self, headers: List[bytes]) -> None:
        """Delete headers from internal datastructure."""
        for key in headers:
            self.del_header(key.lower())

    def set_url(self, url: bytes) -> None:
        """Given a request line, parses it and sets line attributes a.k.a. host, port, path."""
        self._url = Url.from_bytes(url)
        self._set_line_attributes()

    def has_host(self) -> bool:
        """Returns whether host line attribute was parsed or set.

        NOTE: Host field WILL be None for incoming local WebServer requests."""
        return self.host is not None

    def is_http_1_1_keep_alive(self) -> bool:
        """Returns true for HTTP/1.1 keep-alive connections."""
        return self.version == HTTP_1_1 and \
            (
                not self.has_header(b'Connection') or
                self.header(b'Connection').lower() == b'keep-alive'
            )

    def is_connection_upgrade(self) -> bool:
        """Returns true for websocket upgrade requests."""
        return self.version == HTTP_1_1 and \
            self.has_header(b'Connection') and \
            self.has_header(b'Upgrade')

    def is_https_tunnel(self) -> bool:
        """Returns true for HTTPS CONNECT tunnel request."""
        return self.method == httpMethods.CONNECT

    def is_chunked_encoded(self) -> bool:
        """Returns true if transfer-encoding chunked is used."""
        return b'transfer-encoding' in self.headers and \
               self.headers[b'transfer-encoding'][1].lower() == b'chunked'

    def content_expected(self) -> bool:
        """Returns true if content-length is present and not 0."""
        return b'content-length' in self.headers and int(self.header(b'content-length')) > 0

    def body_expected(self) -> bool:
        """Returns true if content or chunked response is expected."""
        return self.content_expected() or self.is_chunked_encoded()

    def parse(self, raw: bytes) -> None:
        """Parses Http request out of raw bytes.

        Check for `HttpParser.state` after `parse` has successfully returned.
        """
        self.total_size += len(raw)
        raw = self.buffer + raw
        self.buffer, more = b'', len(raw) > 0
        while more and self.state != httpParserStates.COMPLETE:
            # gte with HEADERS_COMPLETE also encapsulated RCVING_BODY state
            more, raw = self._process_body(raw) \
                if self.state >= httpParserStates.HEADERS_COMPLETE else \
                self._process_line_and_headers(raw)
        self.buffer = raw

    def build(self, disable_headers: Optional[List[bytes]] = None, for_proxy: bool = False) -> bytes:
        """Rebuild the request object."""
        assert self.method and self.version and self.type == httpParserTypes.REQUEST_PARSER
        if disable_headers is None:
            disable_headers = DEFAULT_DISABLE_HEADERS
        body: Optional[bytes] = self._get_body_or_chunks()
        path = self.path or b'/'
        if for_proxy:
            assert self.host and self.port and self._url
            path = (
                b'http' if not self._url.scheme else self._url.scheme +
                COLON + SLASH + SLASH +
                self.host +
                COLON +
                str(self.port).encode() +
                path
            ) if not self.is_https_tunnel() else (self.host + COLON + str(self.port).encode())
        return build_http_request(
            self.method, path, self.version,
            headers={} if not self.headers else {
                self.headers[k][0]: self.headers[k][1] for k in self.headers if
                k.lower() not in disable_headers
            },
            body=body,
        )

    def build_response(self) -> bytes:
        """Rebuild the response object."""
        assert self.code and self.version and self.type == httpParserTypes.RESPONSE_PARSER
        return build_http_response(
            status_code=int(self.code),
            protocol_version=self.version,
            reason=self.reason,
            headers={} if not self.headers else {
                self.headers[k][0]: self.headers[k][1] for k in self.headers
            },
            body=self._get_body_or_chunks(),
        )

    def _process_body(self, raw: bytes) -> Tuple[bool, bytes]:
        # Ref: http://www.ietf.org/rfc/rfc2616.txt
        # 3.If a Content-Length header field (section 14.13) is present, its
        #   decimal value in OCTETs represents both the entity-length and the
        #   transfer-length. The Content-Length header field MUST NOT be sent
        #   if these two lengths are different (i.e., if a Transfer-Encoding
        #   header field is present). If a message is received with both a
        #   Transfer-Encoding header field and a Content-Length header field,
        #   the latter MUST be ignored.
        #
        # TL;DR -- Give transfer-encoding header preference over content-length.
        if self.is_chunked_encoded():
            if not self.chunk:
                self.chunk = ChunkParser()
            raw = self.chunk.parse(raw)
            if self.chunk.state == chunkParserStates.COMPLETE:
                self.body = self.chunk.body
                self.state = httpParserStates.COMPLETE
            more = False
        elif b'content-length' in self.headers:
            self.state = httpParserStates.RCVING_BODY
            if self.body is None:
                self.body = b''
            total_size = int(self.header(b'content-length'))
            received_size = len(self.body)
            self.body += raw[:total_size - received_size]
            if self.body and \
                    len(self.body) == int(self.header(b'content-length')):
                self.state = httpParserStates.COMPLETE
            more, raw = len(raw) > 0, raw[total_size - received_size:]
        else:
            # HTTP/1.0 scenario only
            assert self.version == HTTP_1_0
            self.state = httpParserStates.RCVING_BODY
            # Received a packet without content-length header
            # and no transfer-encoding specified.
            #
            # Ref https://github.com/abhinavsingh/proxy.py/issues/398
            # See TestHttpParser.test_issue_398 scenario
            self.body = raw
            more, raw = False, b''
        return more, raw

    def _process_line_and_headers(self, raw: bytes) -> Tuple[bool, bytes]:
        """Returns False when no CRLF could be found in received bytes."""
        line, raw = find_http_line(raw)
        if line is None:
            return False, raw

        if self.state == httpParserStates.INITIALIZED:
            self._process_line(line)
            self.state = httpParserStates.LINE_RCVD
        elif self.state in (httpParserStates.LINE_RCVD, httpParserStates.RCVING_HEADERS):
            if self.state == httpParserStates.LINE_RCVD:
                # LINE_RCVD state is equivalent to RCVING_HEADERS
                self.state = httpParserStates.RCVING_HEADERS
            if line.strip() == b'':  # Blank line received.
                self.state = httpParserStates.HEADERS_COMPLETE
            else:
                self._process_header(line)

        # When server sends a response line without any header or body e.g.
        # HTTP/1.1 200 Connection established\r\n\r\n
        if self.state == httpParserStates.LINE_RCVD and \
                self.type == httpParserTypes.RESPONSE_PARSER and \
                raw == CRLF:
            self.state = httpParserStates.COMPLETE
        elif self.state == httpParserStates.HEADERS_COMPLETE and \
                not self.body_expected() and \
                raw == b'':
            self.state = httpParserStates.COMPLETE

        return len(raw) > 0, raw

    def _process_line(self, raw: bytes) -> None:
        line = raw.split(WHITESPACE)
        if self.type == httpParserTypes.REQUEST_PARSER:
            self.method = line[0].upper()
            self.set_url(line[1])
            self.version = line[2]
        else:
            self.version = line[0]
            self.code = line[1]
            self.reason = WHITESPACE.join(line[2:])

    def _process_header(self, raw: bytes) -> None:
        parts = raw.split(COLON)
        key = parts[0].strip()
        value = COLON.join(parts[1:]).strip()
        self.add_headers([(key, value)])

    def _get_body_or_chunks(self) -> Optional[bytes]:
        return ChunkParser.to_chunks(self.body) \
            if self.body and self.is_chunked_encoded() else \
            self.body

    def _set_line_attributes(self) -> None:
        if self.type == httpParserTypes.REQUEST_PARSER:
            if self.is_https_tunnel() and self._url:
                self.host = self._url.hostname
                self.port = 443 if self._url.port is None else self._url.port
            elif self._url:
                self.host, self.port = self._url.hostname, self._url.port \
                    if self._url.port else DEFAULT_HTTP_PORT
            else:
                raise KeyError(
                    'Invalid request. Method: %r, Url: %r' %
                    (self.method, self._url),
                )
            self.path = self._url.remainder