from __future__ import annotations

import asyncio
import contextvars
import http
import logging
import re
import sys
import urllib
from asyncio.events import TimerHandle
from collections import deque
from collections.abc import Callable
from typing import Any, Literal

import httptools

from uvicorn._types import (
    ASGI3Application,
    ASGIReceiveEvent,
    ASGISendEvent,
    HTTPRequestEvent,
    HTTPScope,
)
from uvicorn.config import Config
from uvicorn.logging import TRACE_LOG_LEVEL
from uvicorn.protocols.http.flow_control import CLOSE_HEADER, HIGH_WATER_LIMIT, FlowControl, service_unavailable
from uvicorn.protocols.utils import get_client_addr, get_local_addr, get_path_with_query_string, get_remote_addr, is_ssl
from uvicorn.server import ServerState

HEADER_RE = re.compile(b'[\x00-\x1f\x7f()<>@,;:\\[\\]={} \t\\\\"]')
HEADER_VALUE_RE = re.compile(b"[\x00-\x08\x0a-\x1f\x7f]")


def _get_status_line(status_code: int) -> bytes:
    try:
        phrase = http.HTTPStatus(status_code).phrase.encode()
    except ValueError:
        phrase = b""
    return b"".join([b"HTTP/1.1 ", str(status_code).encode(), b" ", phrase, b"\r\n"])


STATUS_LINE = {status_code: _get_status_line(status_code) for status_code in range(100, 600)}


class HttpToolsProtocol(asyncio.Protocol):
    def __init__(
        self,
        config: Config,
        server_state: ServerState,
        app_state: dict[str, Any],
        _loop: asyncio.AbstractEventLoop | None = None,
    ) -> None:
        if not config.loaded:
            config.load()

        self.config = config
        self.app = config.loaded_app
        self.loop = _loop or asyncio.get_event_loop()
        self.logger = logging.getLogger("uvicorn.error")
        self.access_logger = logging.getLogger("uvicorn.access")
        self.access_log = self.access_logger.hasHandlers()
        self.parser = httptools.HttpRequestParser(self)

        try:
            # Enable dangerous leniencies to allow server to a response on the first request from a pipelined request.
            self.parser.set_dangerous_leniencies(lenient_data_after_close=True)
        except AttributeError:  # pragma: no cover
            # httptools < 0.6.3
            pass

        self.ws_protocol_class = config.ws_protocol_class
        self.root_path = config.root_path
        self.limit_concurrency = config.limit_concurrency
        self.app_state = app_state

        # Timeouts
        self.timeout_keep_alive_task: TimerHandle | None = None
        self.timeout_keep_alive = config.timeout_keep_alive

        # Global state
        self.server_state = server_state
        self.connections = server_state.connections
        self.tasks = server_state.tasks

        # Per-connection state
        self.transport: asyncio.Transport = None  # type: ignore[assignment]
        self.flow: FlowControl = None  # type: ignore[assignment]
        self.server: tuple[str, int | None] | None = None
        self.client: tuple[str, int] | None = None
        self.scheme: Literal["http", "https"] | None = None
        self.pipeline: deque[tuple[RequestResponseCycle, ASGI3Application]] = deque()

        # Per-request state
        self.scope: HTTPScope = None  # type: ignore[assignment]
        self.headers: list[tuple[bytes, bytes]] = None  # type: ignore[assignment]
        self.expect_100_continue = False
        self.cycle: RequestResponseCycle = None  # type: ignore[assignment]

    # Protocol interface
    def connection_made(  # type: ignore[override]
        self, transport: asyncio.Transport
    ) -> None:
        self.connections.add(self)

        self.transport = transport
        self.flow = FlowControl(transport)
        self.server = get_local_addr(transport)
        self.client = get_remote_addr(transport)
        self.scheme = "https" if is_ssl(transport) else "http"

        if self.logger.level <= TRACE_LOG_LEVEL:
            prefix = "%s:%d - " % self.client if self.client else ""
            self.logger.log(TRACE_LOG_LEVEL, "%sHTTP connection made", prefix)

    def connection_lost(self, exc: Exception | None) -> None:
        self.connections.discard(self)

        if self.logger.level <= TRACE_LOG_LEVEL:
            prefix = "%s:%d - " % self.client if self.client else ""
            self.logger.log(TRACE_LOG_LEVEL, "%sHTTP connection lost", prefix)

        if self.cycle and not self.cycle.response_complete:
            self.cycle.disconnected = True
        if self.cycle is not None:
            self.cycle.message_event.set()
        if self.flow is not None:
            self.flow.resume_writing()
        if exc is None:
            self.transport.close()
            self._unset_keepalive_if_required()

        self.parser = None  # type: ignore[assignment]

    def eof_received(self) -> None:
        pass

    def _unset_keepalive_if_required(self) -> None:
        if self.timeout_keep_alive_task is not None:
            self.timeout_keep_alive_task.cancel()
            self.timeout_keep_alive_task = None

    def _get_upgrade(self) -> bytes | None:
        connection = []
        upgrade = None
        for name, value in self.headers:
            if name == b"connection":
                connection = [token.lower().strip() for token in value.split(b",")]
            if name == b"upgrade":
                upgrade = value.lower()
        if b"upgrade" in connection:
            return upgrade
        return None  # pragma: full coverage

    def _should_upgrade_to_ws(self) -> bool:
        if self.ws_protocol_class is None:
            return False
        return True

    def _unsupported_upgrade_warning(self) -> None:
        self.logger.warning("Unsupported upgrade request.")
        if not self._should_upgrade_to_ws():
            msg = "No supported WebSocket library detected. Please use \"pip install 'uvicorn[standard]'\", or install 'websockets' or 'wsproto' manually."  # noqa: E501
            self.logger.warning(msg)

    def _should_upgrade(self) -> bool:
        upgrade = self._get_upgrade()
        return upgrade == b"websocket" and self._should_upgrade_to_ws()

    def data_received(self, data: bytes) -> None:
        self._unset_keepalive_if_required()

        try:
            self.parser.feed_data(data)
        except httptools.HttpParserError:
            msg = "Invalid HTTP request received."
            self.logger.warning(msg)
            self.send_400_response(msg)
            return
        except httptools.HttpParserUpgrade:
            if self._should_upgrade():
                self.handle_websocket_upgrade()
            else:
                self._unsupported_upgrade_warning()

    def handle_websocket_upgrade(self) -> None:
        if self.logger.level <= TRACE_LOG_LEVEL:
            prefix = "%s:%d - " % self.client if self.client else ""
            self.logger.log(TRACE_LOG_LEVEL, "%sUpgrading to WebSocket", prefix)

        self.connections.discard(self)
        method = self.scope["method"].encode()
        output = [method, b" ", self.url, b" HTTP/1.1\r\n"]
        for name, value in self.scope["headers"]:
            output += [name, b": ", value, b"\r\n"]
        output.append(b"\r\n")
        protocol = self.ws_protocol_class(  # type: ignore[call-arg, misc]
            config=self.config,
            server_state=self.server_state,
            app_state=self.app_state,
        )
        protocol.connection_made(self.transport)
        protocol.data_received(b"".join(output))
        self.transport.set_protocol(protocol)

    def send_400_response(self, msg: str) -> None:
        content = [STATUS_LINE[400]]
        for name, value in self.server_state.default_headers:
            content.extend([name, b": ", value, b"\r\n"])  # pragma: full coverage
        content.extend(
            [
                b"content-type: text/plain; charset=utf-8\r\n",
                b"content-length: " + str(len(msg)).encode("ascii") + b"\r\n",
                b"connection: close\r\n",
                b"\r\n",
                msg.encode("ascii"),
            ]
        )
        self.transport.write(b"".join(content))
        self.transport.close()

    def on_message_begin(self) -> None:
        self.url = b""
        self.expect_100_continue = False
        self.headers = []
        self.scope = {  # type: ignore[typeddict-item]
            "type": "http",
            "asgi": {"version": self.config.asgi_version, "spec_version": "2.3"},
            "http_version": "1.1",
            "server": self.server,
            "client": self.client,
            "scheme": self.scheme,  # type: ignore[typeddict-item]
            "root_path": self.root_path,
            "headers": self.headers,
            "state": self.app_state.copy(),
        }

    # Parser callbacks
    def on_url(self, url: bytes) -> None:
        self.url += url

    def on_header(self, name: bytes, value: bytes) -> None:
        name = name.lower()
        if name == b"expect" and value.lower() == b"100-continue":
            self.expect_100_continue = True
        self.headers.append((name, value))

    def on_headers_complete(self) -> None:
        http_version = self.parser.get_http_version()
        method = self.parser.get_method()
        self.scope["method"] = method.decode("ascii")
        if http_version != "1.1":
            self.scope["http_version"] = http_version
        if self.parser.should_upgrade() and self._should_upgrade():
            return
        parsed_url = httptools.parse_url(self.url)
        raw_path = parsed_url.path
        path = raw_path.decode("ascii")
        if "%" in path:
            path = urllib.parse.unquote(path)
        full_path = self.root_path + path
        full_raw_path = self.root_path.encode("ascii") + raw_path
        self.scope["path"] = full_path
        self.scope["raw_path"] = full_raw_path
        self.scope["query_string"] = parsed_url.query or b""

        # Handle 503 responses when 'limit_concurrency' is exceeded.
        if self.limit_concurrency is not None and (
            len(self.connections) >= self.limit_concurrency or len(self.tasks) >= self.limit_concurrency
        ):
            app = service_unavailable
            message = "Exceeded concurrency limit."
            self.logger.warning(message)
        else:
            app = self.app

        existing_cycle = self.cycle
        self.cycle = RequestResponseCycle(
            scope=self.scope,
            transport=self.transport,
            flow=self.flow,
            logger=self.logger,
            access_logger=self.access_logger,
            access_log=self.access_log,
            default_headers=self.server_state.default_headers,
            message_event=asyncio.Event(),
            expect_100_continue=self.expect_100_continue,
            keep_alive=http_version != "1.0",
            on_response=self.on_response_complete,
        )
        if existing_cycle is None or existing_cycle.response_complete:
            # Standard case - start processing the request.
            self._start_asgi_task(self.cycle, app)
        else:
            # Pipelined HTTP requests need to be queued up.
            self.flow.pause_reading()
            self.pipeline.appendleft((self.cycle, app))

    def _start_asgi_task(self, cycle: RequestResponseCycle, app: ASGI3Application) -> None:
        if self.config.reset_contextvars:
            # Opt-in workaround for https://github.com/python/cpython/issues/140947:
            # asyncio can leak context vars between tasks. Hides context set in the
            # lifespan or by external instrumentation.
            if sys.version_info >= (3, 11):  # pragma: py-lt-311
                task = self.loop.create_task(cycle.run_asgi(app), context=contextvars.Context())
            else:  # pragma: py-gte-311
                task = contextvars.Context().run(self.loop.create_task, cycle.run_asgi(app))
        else:
            task = self.loop.create_task(cycle.run_asgi(app))
        task.add_done_callback(self.tasks.discard)
        self.tasks.add(task)

    def on_body(self, body: bytes) -> None:
        if (self.parser.should_upgrade() and self._should_upgrade()) or self.cycle.response_complete:
            return
        self.cycle.body += body
        if len(self.cycle.body) > HIGH_WATER_LIMIT:
            self.flow.pause_reading()
        self.cycle.message_event.set()

    def on_message_complete(self) -> None:
        if (self.parser.should_upgrade() and self._should_upgrade()) or self.cycle.response_complete:
            return
        self.cycle.more_body = False
        self.cycle.message_event.set()

    def on_response_complete(self) -> None:
        # Callback for pipelined HTTP requests to be started.
        self.server_state.total_requests += 1

        if self.transport.is_closing():
            return

        self._unset_keepalive_if_required()

        # Unpause data reads if needed.
        self.flow.resume_reading()

        # Unblock any pipelined events. If there are none, arm the
        # Keep-Alive timeout instead.
        if self.pipeline:
            cycle, app = self.pipeline.pop()
            self._start_asgi_task(cycle, app)
        else:
            self.timeout_keep_alive_task = self.loop.call_later(
                self.timeout_keep_alive, self.timeout_keep_alive_handler
            )

    def shutdown(self) -> None:
        """
        Called by the server to commence a graceful shutdown.
        """
        if self.cycle is None or self.cycle.response_complete:
            self.transport.close()
        else:
            self.cycle.keep_alive = False

    def pause_writing(self) -> None:
        """
        Called by the transport when the write buffer exceeds the high water mark.
        """
        self.flow.pause_writing()  # pragma: full coverage

    def resume_writing(self) -> None:
        """
        Called by the transport when the write buffer drops below the low water mark.
        """
        self.flow.resume_writing()  # pragma: full coverage

    def timeout_keep_alive_handler(self) -> None:
        """
        Called on a keep-alive connection if no new data is received after a short
        delay.
        """
        if not self.transport.is_closing():
            self.transport.close()


class RequestResponseCycle:
    def __init__(
        self,
        scope: HTTPScope,
        transport: asyncio.Transport,
        flow: FlowControl,
        logger: logging.Logger,
        access_logger: logging.Logger,
        access_log: bool,
        default_headers: list[tuple[bytes, bytes]],
        message_event: asyncio.Event,
        expect_100_continue: bool,
        keep_alive: bool,
        on_response: Callable[..., None],
    ):
        self.scope = scope
        self.transport = transport
        self.flow = flow
        self.logger = logger
        self.access_logger = access_logger
        self.access_log = access_log
        self.default_headers = default_headers
        self.message_event = message_event
        self.on_response = on_response

        # Connection state
        self.disconnected = False
        self.keep_alive = keep_alive
        self.waiting_for_100_continue = expect_100_continue

        # Request state
        self.body = bytearray()
        self.more_body = True

        # Response state
        self.response_started = False
        self.response_complete = False
        self.chunked_encoding: bool | None = None
        self.expected_content_length = 0

    # ASGI exception wrapper
    async def run_asgi(self, app: ASGI3Application) -> None:
        try:
            result = await app(  # type: ignore[func-returns-value]
                self.scope, self.receive, self.send
            )
        except BaseException as exc:
            msg = "Exception in ASGI application\n"
            self.logger.error(msg, exc_info=exc)
            if not self.response_started:
                await self.send_500_response()
            else:
                self.transport.close()
        else:
            if result is not None:
                msg = "ASGI callable should return None, but returned '%s'."
                self.logger.error(msg, result)
                self.transport.close()
            elif not self.response_started and not self.disconnected:
                msg = "ASGI callable returned without starting response."
                self.logger.error(msg)
                await self.send_500_response()
            elif not self.response_complete and not self.disconnected:
                msg = "ASGI callable returned without completing response."
                self.logger.error(msg)
                self.transport.close()
        finally:
            self.on_response = lambda: None

    async def send_500_response(self) -> None:
        await self.send(
            {
                "type": "http.response.start",
                "status": 500,
                "headers": [
                    (b"content-type", b"text/plain; charset=utf-8"),
                    (b"content-length", b"21"),
                    (b"connection", b"close"),
                ],
            }
        )
        await self.send({"type": "http.response.body", "body": b"Internal Server Error", "more_body": False})

    # ASGI interface
    async def send(self, message: ASGISendEvent) -> None:
        if self.flow.write_paused and not self.disconnected:
            await self.flow.drain()  # pragma: full coverage

        if self.disconnected:
            return  # pragma: full coverage

        if not self.response_started:
            # Sending response status line and headers
            if message["type"] != "http.response.start":
                raise RuntimeError(f"Expected ASGI message 'http.response.start', but got '{message['type']}'.")

            self.response_started = True
            self.waiting_for_100_continue = False

            status_code = message["status"]
            headers = self.default_headers + list(message.get("headers", []))

            if CLOSE_HEADER in self.scope["headers"] and CLOSE_HEADER not in headers:
                headers = headers + [CLOSE_HEADER]

            if self.access_log:
                self.access_logger.info(
                    '%s - "%s %s HTTP/%s" %d',
                    get_client_addr(self.scope),
                    self.scope["method"],
                    get_path_with_query_string(self.scope),
                    self.scope["http_version"],
                    status_code,
                )

            # Write response status line and headers
            content = [STATUS_LINE[status_code]]

            for name, value in headers:
                if HEADER_RE.search(name):
                    raise RuntimeError("Invalid HTTP header name.")  # pragma: full coverage
                if HEADER_VALUE_RE.search(value):
                    raise RuntimeError("Invalid HTTP header value.")

                name = name.lower()
                if name == b"content-length" and self.chunked_encoding is None:
                    self.expected_content_length = int(value.decode())
                    self.chunked_encoding = False
                elif name == b"transfer-encoding" and value.lower() == b"chunked":
                    self.expected_content_length = 0
                    self.chunked_encoding = True
                elif name == b"connection" and value.lower() == b"close":
                    self.keep_alive = False
                content.extend([name, b": ", value, b"\r\n"])

            if self.chunked_encoding is None and self.scope["method"] != "HEAD" and status_code not in (204, 304):
                # Neither content-length nor transfer-encoding specified
                self.chunked_encoding = True
                content.append(b"transfer-encoding: chunked\r\n")

            content.append(b"\r\n")
            self.transport.write(b"".join(content))

        elif not self.response_complete:
            # Sending response body
            if message["type"] != "http.response.body":
                raise RuntimeError(f"Expected ASGI message 'http.response.body', but got '{message['type']}'.")

            body = message.get("body", b"")
            more_body = message.get("more_body", False)

            # Write response body
            if self.scope["method"] == "HEAD":
                self.expected_content_length = 0
            elif self.chunked_encoding:
                if body:
                    content = [b"%x\r\n" % len(body), body, b"\r\n"]
                else:
                    content = []
                if not more_body:
                    content.append(b"0\r\n\r\n")
                self.transport.write(b"".join(content))
            else:
                num_bytes = len(body)
                if num_bytes > self.expected_content_length:
                    raise RuntimeError("Response content longer than Content-Length")
                else:
                    self.expected_content_length -= num_bytes
                self.transport.write(body)

            # Handle response completion
            if not more_body:
                if self.expected_content_length != 0:
                    raise RuntimeError("Response content shorter than Content-Length")
                self.response_complete = True
                self.message_event.set()
                if not self.keep_alive:
                    self.transport.close()
                self.on_response()

        else:
            # Response already sent
            raise RuntimeError(f"Unexpected ASGI message '{message['type']}' sent, after response already completed.")

    async def receive(self) -> ASGIReceiveEvent:
        if self.waiting_for_100_continue and not self.transport.is_closing():
            self.transport.write(b"HTTP/1.1 100 Continue\r\n\r\n")
            self.waiting_for_100_continue = False

        if not self.disconnected and not self.response_complete:
            self.flow.resume_reading()
            await self.message_event.wait()
            self.message_event.clear()

        if self.disconnected or self.response_complete:
            return {"type": "http.disconnect"}
        message: HTTPRequestEvent = {"type": "http.request", "body": bytes(self.body), "more_body": self.more_body}
        self.body = bytearray()
        return message
