import { SimplePool } from 'nostr-tools'
import type { Filter } from 'nostr-tools'
import type { Event } from 'nostr-tools'

/**
 * Subscription interface matching nostr-tools 2.x API
 */
export interface Subscription {
  on(event: 'event', callback: (event: Event) => void): void
  on(event: 'eose', callback: () => void): void
  unsub(): void
}

/**
 * Type for SimplePool with subscribe method (for backward compatibility)
 * Note: SimplePool already has subscribe method, this is just for type compatibility
 */
export type SimplePoolWithSub = SimplePool

/**
 * Helper to create a subscription compatible with the old API
 */
export function createSubscription(
  pool: SimplePool,
  relays: string[],
  filters: Filter[]
): Subscription {
  const state = createSubscriptionState()
  const subscription = pool.subscribe(relays, filters[0] ?? {}, {
    onevent: (event: Event) => onSubscriptionEvent({ state, event }),
    oneose: () => onSubscriptionEose({ state }),
  })
  return buildSubscriptionWrapper({ state, subscription })
}

function createSubscriptionState(): {
  events: Event[]
  eoseReceived: boolean
  eventCallbacks: Array<(event: Event) => void>
  eoseCallbacks: Array<() => void>
} {
  return { events: [], eoseReceived: false, eventCallbacks: [], eoseCallbacks: [] }
}

function onSubscriptionEvent(params: { state: ReturnType<typeof createSubscriptionState>; event: Event }): void {
  params.state.events.push(params.event)
  params.state.eventCallbacks.forEach((cb) => cb(params.event))
}

function onSubscriptionEose(params: { state: ReturnType<typeof createSubscriptionState> }): void {
  const { state } = params
  state.eoseReceived = true
  state.eoseCallbacks.forEach((cb) => cb())
}

function buildSubscriptionWrapper(params: {
  state: ReturnType<typeof createSubscriptionState>
  subscription: { close: () => void }
}): Subscription {
  return {
    on(event: 'event' | 'eose', callback: ((event: Event) => void) | (() => void)): void {
      handleSubscriptionOn({ state: params.state, event, callback })
    },
    unsub(): void {
      params.subscription.close()
    },
  }
}

function handleSubscriptionOn(params: {
  state: ReturnType<typeof createSubscriptionState>
  event: 'event' | 'eose'
  callback: ((event: Event) => void) | (() => void)
}): void {
  if (params.event === 'event') {
    const eventCb = params.callback as (event: Event) => void
    params.state.eventCallbacks.push(eventCb)
    params.state.events.forEach((e) => eventCb(e))
    return
  }
  const eoseCb = params.callback as () => void
  if (params.state.eoseReceived) {
    eoseCb()
    return
  }
  params.state.eoseCallbacks.push(eoseCb)
}