import contextlib
import dataclasses
from typing import Dict, Any, Optional, List, Iterator

from haystack.tracing import Span, Tracer


@dataclasses.dataclass
class SpyingSpan(Span):
    operation_name: str
    tags: Dict[str, Any] = dataclasses.field(default_factory=dict)

    def set_tag(self, key: str, value: Any) -> None:
        self.tags[key] = value


class SpyingTracer(Tracer):
    def current_span(self) -> Optional[Span]:
        return self.spans[-1] if self.spans else None

    def __init__(self) -> None:
        self.spans: List[SpyingSpan] = []

    @contextlib.contextmanager
    def trace(self, operation_name: str, tags: Optional[Dict[str, Any]] = None) -> Iterator[Span]:
        new_span = SpyingSpan(operation_name)

        for key, value in (tags or {}).items():
            new_span.set_tag(key, value)

        self.spans.append(new_span)

        yield new_span