/**
 * Tiny client-side SDK for canvas renderers. Import this directly (it's bundled into
 * your canvas by esbuild, not shared at runtime). It's the only thing a canvas needs
 * to talk to the host. No Node, no fs, no DOM access outside your own iframe.
 */
import {
  BRIDGE_CHANNEL,
  type BridgeEventMessage,
  type BridgeEventName,
  type BridgeEventPayloadMap,
  type BridgeMethod,
  type BridgeMethodMap,
  type BridgeRequestMessage,
  type BridgeResponseMessage
} from './types'

let counter = 0
function nextId(): string {
  counter += 1
  return `${Date.now()}-${counter}`
}

const pending = new Map<string, { resolve: (v: unknown) => void; reject: (e: Error) => void }>()
const eventListeners = new Map<BridgeEventName, Set<(payload: unknown) => void>>()

window.addEventListener('message', (e: MessageEvent) => {
  const data = e.data as Partial<BridgeResponseMessage | BridgeEventMessage>
  if (!data || data.channel !== BRIDGE_CHANNEL) return

  if (data.type === 'response') {
    const msg = data as BridgeResponseMessage
    const waiter = pending.get(msg.id)
    if (!waiter) return
    pending.delete(msg.id)
    if (msg.ok) waiter.resolve(msg.result)
    else waiter.reject(new Error(msg.error ?? 'Bridge call failed'))
  } else if (data.type === 'event') {
    const msg = data as BridgeEventMessage
    for (const cb of eventListeners.get(msg.event) ?? []) cb(msg.payload)
  }
})

/** Call a bridge method. Rejects if the host denies it (missing capability, ownership, etc). */
export function callBridge<M extends BridgeMethod>(
  method: M,
  params: BridgeMethodMap[M]['params']
): Promise<BridgeMethodMap[M]['result']> {
  const id = nextId()
  const message: BridgeRequestMessage<M> = { channel: BRIDGE_CHANNEL, type: 'request', id, method, params }
  return new Promise((resolve, reject) => {
    pending.set(id, { resolve: resolve as (v: unknown) => void, reject })
    window.parent.postMessage(message, '*')
  })
}

/** Subscribe to a host-pushed event (e.g. `note.changed`). Returns an unsubscribe fn. */
export function onBridgeEvent<E extends BridgeEventName>(
  event: E,
  cb: (payload: BridgeEventPayloadMap[E]) => void
): () => void {
  if (!eventListeners.has(event)) eventListeners.set(event, new Set())
  const set = eventListeners.get(event)!
  set.add(cb as (payload: unknown) => void)
  return () => set.delete(cb as (payload: unknown) => void)
}