export type SessionState = 'idle' | 'listening' | 'thinking' | 'speaking';

export type MessageEnvelope<TType extends string, TPayload> = {
	type: TType;
	payload: TPayload;
};

export type ClientEventPayloads = {
	'session.start': Record<string, never>;
	'input_audio.append': {
		chunk: string;
	};
	'input_audio.commit': Record<string, never>;
	'response.cancel': Record<string, never>;
};

export type ServerEventPayloads = {
	'session.ready': {
		sessionId: string;
	};
	'session.state': {
		value: SessionState;
	};
	'transcript.partial': {
		text: string;
	};
	'transcript.final': {
		text: string;
	};
	'response.text.delta': {
		text: string;
	};
	'response.completed': Record<string, never>;
	'error': {
		code: string;
		message: string;
		retryable?: boolean;
	};
};

export type ClientEventType = keyof ClientEventPayloads;
export type ServerEventType = keyof ServerEventPayloads;

export type ClientEvent = {
	[Type in ClientEventType]: MessageEnvelope<Type, ClientEventPayloads[Type]>;
}[ClientEventType];

export type ServerEvent = {
	[Type in ServerEventType]: MessageEnvelope<Type, ServerEventPayloads[Type]>;
}[ServerEventType];

export const PROTOCOL_PACKAGE_NAME: '@vela/protocol';
export const SESSION_STATES: readonly SessionState[];
export const CLIENT_EVENT_TYPES: readonly ClientEventType[];
export const SERVER_EVENT_TYPES: readonly ServerEventType[];

export function createMessageEnvelope<TType extends ClientEventType>(
	type: TType,
	payload: ClientEventPayloads[TType]
): MessageEnvelope<TType, ClientEventPayloads[TType]>;
export function createMessageEnvelope<TType extends ServerEventType>(
	type: TType,
	payload: ServerEventPayloads[TType]
): MessageEnvelope<TType, ServerEventPayloads[TType]>;

export function isMessageEnvelope(value: unknown): value is MessageEnvelope<string, unknown>;
export function isClientEventType(type: string): type is ClientEventType;
export function isServerEventType(type: string): type is ServerEventType;