// Package event defines the Event type and canonical kinds/actors for the
// task observability stream. Events are immutable, per-task, monotonically
// sequenced records persisted by internal/storage.
package event

import (
	"encoding/json"
	"time"
)

// Kind enumerates the canonical event types.
type Kind string

const (
	KindStateChange          Kind = "state_change"
	KindAgentMessage         Kind = "agent_message"
	KindClarificationRequest Kind = "clarification_request"
	KindClarificationAnswer  Kind = "clarification_answer"
	KindHumanMessage         Kind = "human_message"
	KindSummary              Kind = "summary"
	KindCommitMade           Kind = "commit_made"
	KindSubtaskSpawned       Kind = "subtask_spawned"
	KindCostReport           Kind = "cost_report"
	KindExecutionStarted     Kind = "execution_started"
	KindExecutionEnded       Kind = "execution_ended"
	// KindEscalated records a scheduler decision on a role-typed task's
	// escalation ladder (internal/scheduler): either bumping it to the next
	// tier, or declining to (budget denied or ladder exhausted, payload
	// includes "final": true — the task stays FAILED for human attention).
	// Payload shape: from_rung, to_rung, from_provider, to_provider, final.
	KindEscalated Kind = "escalated"
)

// Actor identifies the originator of an event.
type Actor string

const (
	ActorAgent   Actor = "agent"
	ActorUser    Actor = "user"
	ActorChatbot Actor = "chatbot"
	ActorSystem  Actor = "system"
	ActorWebhook Actor = "webhook"
)

// Event is a single timestamped record on a task's audit/observability stream.
// Once written, events are append-only — the seq column is per-task monotonic
// and assigned by the storage layer on insert.
type Event struct {
	ID        string          `json:"id"`
	TaskID    string          `json:"task_id"`
	Seq       int64           `json:"seq"`
	Timestamp time.Time       `json:"timestamp"`
	Kind      Kind            `json:"kind"`
	Actor     Actor           `json:"actor"`
	Payload   json.RawMessage `json:"payload"`
}