# Copyright The OpenTelemetry Authors
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import gzip
import logging
import random
import threading
import zlib
from io import BytesIO
from os import environ
from time import time
from typing import Dict, Optional, Sequence

import requests
from requests.exceptions import ConnectionError

from opentelemetry.exporter.otlp.proto.common.trace_encoder import (
    encode_spans,
)
from opentelemetry.exporter.otlp.proto.http import (
    _OTLP_HTTP_HEADERS,
    Compression,
)
from opentelemetry.exporter.otlp.proto.http._common import (
    _is_retryable,
    _load_session_from_envvar,
)
from opentelemetry.sdk.environment_variables import (
    _OTEL_PYTHON_EXPORTER_OTLP_HTTP_TRACES_CREDENTIAL_PROVIDER,
    OTEL_EXPORTER_OTLP_CERTIFICATE,
    OTEL_EXPORTER_OTLP_CLIENT_CERTIFICATE,
    OTEL_EXPORTER_OTLP_CLIENT_KEY,
    OTEL_EXPORTER_OTLP_COMPRESSION,
    OTEL_EXPORTER_OTLP_ENDPOINT,
    OTEL_EXPORTER_OTLP_HEADERS,
    OTEL_EXPORTER_OTLP_TIMEOUT,
    OTEL_EXPORTER_OTLP_TRACES_CERTIFICATE,
    OTEL_EXPORTER_OTLP_TRACES_CLIENT_CERTIFICATE,
    OTEL_EXPORTER_OTLP_TRACES_CLIENT_KEY,
    OTEL_EXPORTER_OTLP_TRACES_COMPRESSION,
    OTEL_EXPORTER_OTLP_TRACES_ENDPOINT,
    OTEL_EXPORTER_OTLP_TRACES_HEADERS,
    OTEL_EXPORTER_OTLP_TRACES_TIMEOUT,
)
from opentelemetry.sdk.trace import ReadableSpan
from opentelemetry.sdk.trace.export import SpanExporter, SpanExportResult
from opentelemetry.util.re import parse_env_headers

_logger = logging.getLogger(__name__)


DEFAULT_COMPRESSION = Compression.NoCompression
DEFAULT_ENDPOINT = "http://localhost:4318/"
DEFAULT_TRACES_EXPORT_PATH = "v1/traces"
DEFAULT_TIMEOUT = 10  # in seconds
_MAX_RETRYS = 6


class OTLPSpanExporter(SpanExporter):
    def __init__(
        self,
        endpoint: Optional[str] = None,
        certificate_file: Optional[str] = None,
        client_key_file: Optional[str] = None,
        client_certificate_file: Optional[str] = None,
        headers: Optional[Dict[str, str]] = None,
        timeout: Optional[float] = None,
        compression: Optional[Compression] = None,
        session: Optional[requests.Session] = None,
    ):
        self._shutdown_in_progress = threading.Event()
        self._endpoint = endpoint or environ.get(
            OTEL_EXPORTER_OTLP_TRACES_ENDPOINT,
            _append_trace_path(
                environ.get(OTEL_EXPORTER_OTLP_ENDPOINT, DEFAULT_ENDPOINT)
            ),
        )
        self._certificate_file = certificate_file or environ.get(
            OTEL_EXPORTER_OTLP_TRACES_CERTIFICATE,
            environ.get(OTEL_EXPORTER_OTLP_CERTIFICATE, True),
        )
        self._client_key_file = client_key_file or environ.get(
            OTEL_EXPORTER_OTLP_TRACES_CLIENT_KEY,
            environ.get(OTEL_EXPORTER_OTLP_CLIENT_KEY, None),
        )
        self._client_certificate_file = client_certificate_file or environ.get(
            OTEL_EXPORTER_OTLP_TRACES_CLIENT_CERTIFICATE,
            environ.get(OTEL_EXPORTER_OTLP_CLIENT_CERTIFICATE, None),
        )
        self._client_cert = (
            (self._client_certificate_file, self._client_key_file)
            if self._client_certificate_file and self._client_key_file
            else self._client_certificate_file
        )
        headers_string = environ.get(
            OTEL_EXPORTER_OTLP_TRACES_HEADERS,
            environ.get(OTEL_EXPORTER_OTLP_HEADERS, ""),
        )
        self._headers = headers or parse_env_headers(
            headers_string, liberal=True
        )
        self._timeout = timeout or float(
            environ.get(
                OTEL_EXPORTER_OTLP_TRACES_TIMEOUT,
                environ.get(OTEL_EXPORTER_OTLP_TIMEOUT, DEFAULT_TIMEOUT),
            )
        )
        self._compression = compression or _compression_from_env()
        self._session = (
            session
            or _load_session_from_envvar(
                _OTEL_PYTHON_EXPORTER_OTLP_HTTP_TRACES_CREDENTIAL_PROVIDER
            )
            or requests.Session()
        )
        self._session.headers.update(self._headers)
        self._session.headers.update(_OTLP_HTTP_HEADERS)
        # let users override our defaults
        self._session.headers.update(self._headers)
        if self._compression is not Compression.NoCompression:
            self._session.headers.update(
                {"Content-Encoding": self._compression.value}
            )
        self._shutdown = False

    def _export(
        self, serialized_data: bytes, timeout_sec: Optional[float] = None
    ):
        data = serialized_data
        if self._compression == Compression.Gzip:
            gzip_data = BytesIO()
            with gzip.GzipFile(fileobj=gzip_data, mode="w") as gzip_stream:
                gzip_stream.write(serialized_data)
            data = gzip_data.getvalue()
        elif self._compression == Compression.Deflate:
            data = zlib.compress(serialized_data)

        if timeout_sec is None:
            timeout_sec = self._timeout

        # By default, keep-alive is enabled in Session's request
        # headers. Backends may choose to close the connection
        # while a post happens which causes an unhandled
        # exception. This try/except will retry the post on such exceptions
        try:
            resp = self._session.post(
                url=self._endpoint,
                data=data,
                verify=self._certificate_file,
                timeout=timeout_sec,
                cert=self._client_cert,
            )
        except ConnectionError:
            resp = self._session.post(
                url=self._endpoint,
                data=data,
                verify=self._certificate_file,
                timeout=timeout_sec,
                cert=self._client_cert,
            )
        return resp

    def export(self, spans: Sequence[ReadableSpan]) -> SpanExportResult:
        if self._shutdown:
            _logger.warning("Exporter already shutdown, ignoring batch")
            return SpanExportResult.FAILURE

        serialized_data = encode_spans(spans).SerializePartialToString()
        deadline_sec = time() + self._timeout
        for retry_num in range(_MAX_RETRYS):
            # multiplying by a random number between .8 and 1.2 introduces a +/20% jitter to each backoff.
            backoff_seconds = 2**retry_num * random.uniform(0.8, 1.2)
            try:
                resp = self._export(serialized_data, deadline_sec - time())
                if resp.ok:
                    return SpanExportResult.SUCCESS
            except requests.exceptions.RequestException as error:
                reason = error
                retryable = isinstance(error, ConnectionError)
                status_code = None
            else:
                reason = resp.reason
                retryable = _is_retryable(resp)
                status_code = resp.status_code

            if not retryable:
                _logger.error(
                    "Failed to export span batch code: %s, reason: %s",
                    status_code,
                    reason,
                )
                return SpanExportResult.FAILURE

            if (
                retry_num + 1 == _MAX_RETRYS
                or backoff_seconds > (deadline_sec - time())
                or self._shutdown
            ):
                _logger.error(
                    "Failed to export span batch due to timeout, "
                    "max retries or shutdown."
                )
                return SpanExportResult.FAILURE
            _logger.warning(
                "Transient error %s encountered while exporting span batch, retrying in %.2fs.",
                reason,
                backoff_seconds,
            )
            shutdown = self._shutdown_in_progress.wait(backoff_seconds)
            if shutdown:
                _logger.warning("Shutdown in progress, aborting retry.")
                break
        return SpanExportResult.FAILURE

    def shutdown(self):
        if self._shutdown:
            _logger.warning("Exporter already shutdown, ignoring call")
            return
        self._shutdown = True
        self._shutdown_in_progress.set()
        self._session.close()

    def force_flush(self, timeout_millis: int = 30000) -> bool:
        """Nothing is buffered in this exporter, so this method does nothing."""
        return True


def _compression_from_env() -> Compression:
    compression = (
        environ.get(
            OTEL_EXPORTER_OTLP_TRACES_COMPRESSION,
            environ.get(OTEL_EXPORTER_OTLP_COMPRESSION, "none"),
        )
        .lower()
        .strip()
    )
    return Compression(compression)


def _append_trace_path(endpoint: str) -> str:
    if endpoint.endswith("/"):
        return endpoint + DEFAULT_TRACES_EXPORT_PATH
    return endpoint + f"/{DEFAULT_TRACES_EXPORT_PATH}"
