vik 0.1.0

use chrono::{DateTime, Utc};
use serde::{Deserialize, Serialize};

/// Provider-agnostic event vocabulary.
///
/// Adapters translate provider-specific JSONL into this enum; the
/// session JSONL on disk is a record of these decoded events, not the
/// raw provider bytes. A run yields at most one [`AgentEvent::SessionStarted`],
/// any number of `Message`/`TokenUsage`/`RateLimit` interleaved, and
/// terminates with one [`AgentEvent::Completed`] (or trailing `Error`).
/// Parse errors on a single JSONL line surface as [`AgentEvent::Error`]
/// rather than tearing the subprocess down — forward-compat beats hard
/// fail on a new provider event shape.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
#[serde(tag = "kind", rename_all = "snake_case")]
pub enum AgentEvent {
  /// Emitted as early as the provider allows so the session layer can
  /// stamp the JSONL filename or tracing span without buffering events.
  SessionStarted {
    session_id: String,
  },

  Message {
    text: String,
  },

  /// Adapters may emit this multiple times per run; the session
  /// accumulates with `saturating_add` to absorb retries.
  TokenUsage {
    input: u64,
    output: u64,
    cache_read: u64,
  },

  /// `scope` is provider-qualified (e.g. `codex:tokens_per_min`) so
  /// observations from different runtimes never collide in the session
  /// snapshot.
  RateLimit {
    scope: String,
    remaining: u64,
    reset_at: DateTime<Utc>,
    observed_at: DateTime<Utc>,
  },

  Completed,

  /// Either a JSONL parse failure on one line or a provider-side error.
  /// The stream keeps going; the session decides whether to mark the
  /// run as Failed.
  Error {
    detail: String,
  },
}