# Copyright (c) Microsoft. All rights reserved.

from __future__ import annotations

import gzip
import logging
from typing import Any, Awaitable, Callable, Dict, List, Mapping, Optional, Sequence, Tuple, Type, TypeVar

from fastapi import Request, Response
from google.protobuf import json_format
from google.rpc.status_pb2 import Status
from opentelemetry.exporter.otlp.proto.http.trace_exporter import OTLPSpanExporter
from opentelemetry.proto.collector.logs.v1.logs_service_pb2 import (
    ExportLogsServiceRequest,
    ExportLogsServiceResponse,
)
from opentelemetry.proto.collector.metrics.v1.metrics_service_pb2 import (
    ExportMetricsServiceRequest,
    ExportMetricsServiceResponse,
)
from opentelemetry.proto.collector.trace.v1.trace_service_pb2 import (
    ExportTraceServiceRequest,
    ExportTraceServiceResponse,
)
from opentelemetry.proto.common.v1.common_pb2 import AnyValue, KeyValue
from opentelemetry.proto.resource.v1.resource_pb2 import Resource as ProtoResource
from opentelemetry.proto.trace.v1.trace_pb2 import Span as ProtoSpan
from opentelemetry.proto.trace.v1.trace_pb2 import Status as ProtoStatus
from opentelemetry.sdk.resources import Resource
from opentelemetry.sdk.trace import ReadableSpan
from opentelemetry.sdk.trace.export import SpanExportResult
from opentelemetry.util.types import AttributeValue

from agentlightning.semconv import LightningResourceAttributes
from agentlightning.types.tracer import (
    Attributes,
    Event,
    Link,
    OtelResource,
    Span,
    SpanContext,
    StatusCode,
    TraceStatus,
    convert_timestamp,
)

PROTOBUF_CT = "application/x-protobuf"

logger = logging.getLogger(__name__)


T_request = TypeVar("T_request", ExportLogsServiceRequest, ExportMetricsServiceRequest, ExportTraceServiceRequest)
T_response = TypeVar("T_response", ExportLogsServiceResponse, ExportMetricsServiceResponse, ExportTraceServiceResponse)


async def handle_otlp_export(
    request: Request,
    request_message_cls: Type[T_request],
    response_message_cls: Type[T_response],
    message_callback: Optional[Callable[[T_request], Awaitable[None]]],
    signal_name: str,
) -> Response:
    """
    Generic handler for /v1/traces, /v1/metrics, /v1/logs.

    Convert the OTLP Protobuf request to a JSON-like object.
    """
    content_type = request.headers.get("Content-Type", "").split(";")[0].strip()

    if content_type != PROTOBUF_CT:
        # For brevity we only support binary protobuf here.
        return _bad_request_response(
            request,
            f"Unsupported Content-Type '{content_type}', expected '{PROTOBUF_CT}'",
            content_type=PROTOBUF_CT,
        )

    raw_body = await request.body()
    body = _read_body_maybe_gzip(request, raw_body)

    # Empty request is allowed and should still succeed.
    if not body:
        req_msg = request_message_cls()
    else:
        req_msg = request_message_cls()
        try:
            req_msg.ParseFromString(body)
        except Exception as exc:
            return _bad_request_response(request, f"Unable to parse OTLP {signal_name} payload: {exc}")

    if message_callback is not None:
        await message_callback(req_msg)

    # Build success response. Partial success field is left unset.
    resp_msg = response_message_cls()

    # Encode response in the same Content-Type as request.
    if content_type == PROTOBUF_CT:
        resp_bytes = resp_msg.SerializeToString()
    else:
        resp_bytes = json_format.MessageToJson(resp_msg).encode("utf-8")

    resp_bytes, headers = _maybe_gzip_response(request, resp_bytes)

    return Response(
        content=resp_bytes,
        media_type=content_type,
        status_code=200,
        headers=headers,
    )


async def spans_from_proto(
    request: ExportTraceServiceRequest,
    sequence_id_bulk_issuer: Callable[[Sequence[Tuple[str, str]]], Awaitable[Sequence[int]]],
) -> List[Span]:
    """Parse an OTLP proto payload into List[Span].

    A store is needed here for generating a sequence ID for each span.
    """
    output_spans: List[Span] = []

    for resource_spans in request.resource_spans:
        # Resource-level attributes & IDs
        resource_attrs = _kv_list_to_dict(resource_spans.resource.attributes)
        # rollout_id, attempt_id from resource attributes when present.
        rollout_id_resource = resource_attrs.get(LightningResourceAttributes.ROLLOUT_ID.value)
        attempt_id_resource = resource_attrs.get(LightningResourceAttributes.ATTEMPT_ID.value)
        # If sequence id is provided, all the spans will share the same sequence ID.
        # unless otherwise overridden by span-level attributes.
        sequence_id_resource = resource_attrs.get(LightningResourceAttributes.SPAN_SEQUENCE_ID.value)

        otel_resource = _resource_from_proto(resource_spans.resource, getattr(resource_spans, "schema_url", ""))

        # Each ScopeSpans contains multiple spans
        for scope_spans in resource_spans.scope_spans:
            for proto_span in scope_spans.spans:
                trace_id_hex = _bytes_to_trace_id_hex(proto_span.trace_id)
                span_id_hex = _bytes_to_span_id_hex(proto_span.span_id)
                parent_id_hex = _bytes_to_span_id_hex(proto_span.parent_span_id) if proto_span.parent_span_id else None

                # Status
                status_code_str = _STATUS_CODE_MAP.get(proto_span.status.code, "UNSET")
                status = TraceStatus(
                    status_code=status_code_str,
                    description=proto_span.status.message or None,
                )

                # Attributes
                span_attrs = _kv_list_to_dict(proto_span.attributes)

                # Context
                context = SpanContext(
                    trace_id=trace_id_hex,
                    span_id=span_id_hex,
                    is_remote=False,
                    trace_state={},
                )

                # Try to get if span attributes contain something like rollout_id or attempt_id
                # Override the resource-level attributes with the span-level attributes if present.
                rollout_id_span = span_attrs.get(LightningResourceAttributes.ROLLOUT_ID.value)
                attempt_id_span = span_attrs.get(LightningResourceAttributes.ATTEMPT_ID.value)
                sequence_id_span = span_attrs.get(LightningResourceAttributes.SPAN_SEQUENCE_ID.value)

                # Normalize to regular strings and ints
                rollout_id_raw = rollout_id_span if rollout_id_span is not None else rollout_id_resource
                attempt_id_raw = attempt_id_span if attempt_id_span is not None else attempt_id_resource
                sequence_id_raw = sequence_id_span if sequence_id_span is not None else sequence_id_resource

                rollout_id, attempt_id = _normalize_rollout_attempt_id(rollout_id_raw, attempt_id_raw)
                sequence_id = _normalize_sequence_id(sequence_id_raw)

                if rollout_id is None or attempt_id is None:
                    logger.warning(
                        "Both rollout_id and attempt_id must be present in resource attributes. "
                        "Spans will not be able to log to the store because of missing IDs: rollout_id=%s, attempt_id=%s, sequence_id=%s",
                        rollout_id,
                        attempt_id,
                        sequence_id,
                    )
                    continue

                # Generate a new sequence ID if not provided
                if sequence_id is None:
                    current_sequence_id = -1
                elif sequence_id < 0:
                    logger.error(
                        "Invalid sequence_id value in resource attributes: %r. Must be a positive integer. Regenerating one.",
                        sequence_id,
                    )
                    current_sequence_id = -1
                else:
                    current_sequence_id = sequence_id

                # Build Span
                span = Span(
                    rollout_id=rollout_id,
                    attempt_id=attempt_id,
                    sequence_id=current_sequence_id,
                    trace_id=trace_id_hex,
                    span_id=span_id_hex,
                    parent_id=parent_id_hex,
                    name=proto_span.name,
                    status=status,
                    attributes=span_attrs,
                    events=_events_from_proto(proto_span),
                    links=_links_from_proto(proto_span),
                    start_time=convert_timestamp(proto_span.start_time_unix_nano),
                    end_time=convert_timestamp(proto_span.end_time_unix_nano),
                    context=context,
                    parent=None,  # OTLP only has parent_span_id; we don't have full SpanContext
                    resource=otel_resource,
                )

                output_spans.append(span)

    # Finalize the sequence IDs
    bulk_issue_requests = [(span.rollout_id, span.attempt_id) for span in output_spans if span.sequence_id < 0]
    bulk_sequence_ids = await sequence_id_bulk_issuer(bulk_issue_requests)
    for span, sequence_id in zip(
        [span for span in output_spans if span.sequence_id < 0], bulk_sequence_ids, strict=True
    ):
        span.sequence_id = sequence_id

    return output_spans


class LightningStoreOTLPExporter(OTLPSpanExporter):
    """OTLP Exporter that write to a LightningStore-compatible backend.

    The backend requires two special attributes on each span:

    - `agentlightning.rollout_id`: The rollout ID to associate the span with.
    - `agentlightning.attempt_id`: The attempt ID to associate the span with.

    It can optionally use the following attribute to sequence spans:

    - `agentlightning.span_sequence_id`: A decimal string representing the sequence ID of the span.
    """

    _default_endpoint: Optional[str] = None
    _rollout_id: Optional[str] = None
    _attempt_id: Optional[str] = None

    def __repr__(self) -> str:
        return (
            f"{self.__class__.__name__}("
            + f"endpoint={self.endpoint!r}, "
            + f"rollout_id={self.rollout_id!r}, "
            + f"attempt_id={self.attempt_id!r}, "
            + f"should_bypass={self.should_bypass()!r})"
        )

    @property
    def endpoint(self) -> Optional[str]:
        """The endpoint to submit the spans to."""
        if hasattr(self, "_endpoint"):
            return self._endpoint
        return None

    @property
    def rollout_id(self) -> Optional[str]:
        """The rollout ID to submit the spans to."""
        if hasattr(self, "_rollout_id"):
            return self._rollout_id
        return None

    @property
    def attempt_id(self) -> Optional[str]:
        """The attempt ID to submit the spans to."""
        if hasattr(self, "_attempt_id"):
            return self._attempt_id
        return None

    def enable_store_otlp(self, endpoint: str, rollout_id: str, attempt_id: str) -> None:
        """Enable storing OTLP data to a specific LightningStore rollout/attempt."""
        self._rollout_id = rollout_id
        self._attempt_id = attempt_id

        self._default_endpoint = self._endpoint
        self._endpoint = endpoint

    def disable_store_otlp(self) -> None:
        """Disable storing OTLP data to LightningStore."""
        self._rollout_id = None
        self._attempt_id = None
        if self._default_endpoint is not None:
            self._endpoint = self._default_endpoint

    def should_bypass(self) -> bool:
        """Check if the exporter should bypass the default export if rollout_id and attempt_id are not set."""
        return True

    def export(self, spans: Sequence[ReadableSpan]) -> SpanExportResult:
        if self._rollout_id is not None and self._attempt_id is not None:
            # rollout_id and attempt_id are present in resource attributes
            # It means that the server supports OTLP endpoint.
            for span in spans:
                # Override the resources so that the server knows where the request comes from.
                span._resource = span._resource.merge(  # pyright: ignore[reportPrivateUsage]
                    Resource.create(
                        {
                            LightningResourceAttributes.ROLLOUT_ID.value: self._rollout_id,
                            LightningResourceAttributes.ATTEMPT_ID.value: self._attempt_id,
                        }
                    )
                )
            return super().export(spans)
        elif not self.should_bypass():
            logger.debug("Rollout ID and Attempt ID not set; using default OTLP exporter behavior.")
            return super().export(spans)
        else:
            logger.debug("Rollout ID and Attempt ID not set; bypassing export.")
            return SpanExportResult.SUCCESS


def _read_body_maybe_gzip(request: Request, raw_body: bytes) -> bytes:
    """
    Decompress body if Content-Encoding: gzip; otherwise return as is.
    """
    encoding = request.headers.get("Content-Encoding", "").lower()
    if encoding == "gzip":
        return gzip.decompress(raw_body)
    return raw_body


def _maybe_gzip_response(request: Request, payload: bytes) -> Tuple[bytes, Dict[str, str]]:
    """
    If Accept-Encoding includes gzip, gzip the payload and set Content-Encoding header.
    """
    ae = request.headers.get("Accept-Encoding", "")
    tokens = [token.split(";")[0].strip().lower() for token in ae.split(",") if token.strip()]
    headers: Dict[str, str] = {}
    if "gzip" in tokens:
        payload = gzip.compress(payload)
        headers["Content-Encoding"] = "gzip"
    return payload, headers


def _bad_request_response(request: Request, message: str, content_type: str = PROTOBUF_CT) -> Response:
    """
    Build a 400 response whose body is a protobuf Status message, encoded
    in the same Content-Type as the request (OTLP/HTTP requirement).
    """
    status_msg = Status(message=message)

    if content_type == PROTOBUF_CT:
        body = status_msg.SerializeToString()
    else:
        # Fallback: JSON representation of Status.
        body = json_format.MessageToJson(status_msg).encode("utf-8")

    body, headers = _maybe_gzip_response(request, body)

    return Response(
        content=body,
        status_code=400,
        media_type=content_type,
        headers=headers,
    )


def _normalize_rollout_attempt_id(
    rollout_id: Optional[AttributeValue], attempt_id: Optional[AttributeValue]
) -> Tuple[Optional[str], Optional[str]]:
    """Normalize a rollout or attempt ID to a string."""
    rollout_id_str = str(rollout_id) if rollout_id is not None else None
    attempt_id_str = str(attempt_id) if attempt_id is not None else None
    return rollout_id_str, attempt_id_str


def _normalize_sequence_id(sequence_id: Optional[AttributeValue]) -> Optional[int]:
    """Normalize a sequence ID to an integer."""
    if sequence_id is None:
        return None
    try:
        sequence_id_int = int(str(sequence_id))
    except (ValueError, TypeError):
        logger.warning(
            "Invalid sequence_id value in resource attributes: %r. Must be an integer or string representing an integer. Assuming None.",
            sequence_id,
        )
        sequence_id_int = None
    return sequence_id_int


def _any_value_to_python(value: AnyValue) -> Any:
    """Convert OTLP AnyValue -> plain Python value."""
    kind = value.WhichOneof("value")
    if kind is None:
        return None
    if kind == "string_value":
        return value.string_value
    if kind == "bool_value":
        return value.bool_value
    if kind == "int_value":
        return int(value.int_value)
    if kind == "double_value":
        return float(value.double_value)
    if kind == "array_value":
        return [_any_value_to_python(v) for v in value.array_value.values]
    if kind == "kvlist_value":
        # Map<string, AnyValue> -> dict
        return {kv.key: _any_value_to_python(kv.value) for kv in value.kvlist_value.values}
    if kind == "bytes_value":
        # Serialize bytes as hex string to stay JSON-friendly
        return value.bytes_value.hex()
    return None


def _kv_list_to_dict(kvs: Sequence[KeyValue]) -> Attributes:
    """Convert repeated KeyValue -> Attributes dict."""
    return {kv.key: _any_value_to_python(kv.value) for kv in kvs}


_STATUS_CODE_MAP: Mapping[ProtoStatus.StatusCode.ValueType, StatusCode] = {
    ProtoStatus.STATUS_CODE_UNSET: "UNSET",
    ProtoStatus.STATUS_CODE_OK: "OK",
    ProtoStatus.STATUS_CODE_ERROR: "ERROR",
}


def _bytes_to_trace_id_hex(b: bytes) -> str:
    # OTLP uses 16-byte trace IDs; format as 32-char hex
    if not b:
        return "0" * 32
    return b.hex().rjust(32, "0")


def _bytes_to_span_id_hex(b: bytes) -> str:
    # OTLP uses 8-byte span IDs; format as 16-char hex
    if not b:
        return "0" * 16
    return b.hex().rjust(16, "0")


def _events_from_proto(span: ProtoSpan) -> List[Event]:
    """Event converter from OTLP ProtoSpan to List[Event]."""
    return [
        Event(
            name=e.name,
            attributes=_kv_list_to_dict(e.attributes),
            timestamp=convert_timestamp(e.time_unix_nano),
        )
        for e in span.events
    ]


def _links_from_proto(span: ProtoSpan) -> List[Link]:
    """Link converter from OTLP ProtoSpan to List[Link]."""
    links: List[Link] = []
    for link in span.links:
        trace_id_hex = _bytes_to_trace_id_hex(link.trace_id)
        span_id_hex = _bytes_to_span_id_hex(link.span_id)
        ctx = SpanContext(
            trace_id=trace_id_hex,
            span_id=span_id_hex,
            is_remote=False,
            trace_state={},  # OTLP trace_state is currently a string; you can parse if needed
        )
        links.append(
            Link(
                context=ctx,
                attributes=_kv_list_to_dict(link.attributes) or None,
            )
        )
    return links


def _resource_from_proto(resource: ProtoResource, schema_url: str = "") -> OtelResource:
    return OtelResource(
        attributes=_kv_list_to_dict(resource.attributes),
        schema_url=schema_url or "",
    )
