"""Application-owned events emitted by the recommendation pipeline."""

from dataclasses import dataclass, field
from typing import Literal

from app.domain.models import Track


@dataclass(frozen=True)
class PipelineMetadataEvent:
    """Describe the interpreted request before track results."""

    request_id: str
    intent_summary: str
    candidate_count: int
    type: Literal["metadata"] = field(default="metadata", init=False)


@dataclass(frozen=True)
class PipelineTrackEvent:
    """Carry one ranked, grounded recommendation."""

    rank: int
    track: Track
    justification: str
    type: Literal["track"] = field(default="track", init=False)


@dataclass(frozen=True)
class PipelineWarningEvent:
    """Report a non-terminal degradation."""

    code: str
    message: str
    type: Literal["warning"] = field(default="warning", init=False)


@dataclass(frozen=True)
class PipelineErrorEvent:
    """Report a terminal recommendation failure."""

    code: str
    message: str
    type: Literal["error"] = field(default="error", init=False)


@dataclass(frozen=True)
class PipelineDoneEvent:
    """Report final track count and elapsed time."""

    track_count: int
    total_ms: int
    type: Literal["done"] = field(default="done", init=False)


type PipelineEvent = (
    PipelineMetadataEvent
    | PipelineTrackEvent
    | PipelineWarningEvent
    | PipelineErrorEvent
    | PipelineDoneEvent
)