import axios from 'axios'
import { Event, Filter } from 'nostr-tools'
import { RelayList } from 'nostr-tools/kinds'
import { relayController } from '../controllers/RelayController.ts'
import { localCache } from '../services'
import { setMostPopularRelaysAction } from '../store/actions'
import store from '../store/store'
import { RelayMap, RelayReadStats, RelaySet, RelayStats } from '../types'
import { ONE_WEEK_IN_MS, SIGIT_RELAY } from './const.ts'

const READ_MARKER = 'read'
const WRITE_MARKER = 'write'

/**
 * Attempts to find a relay list from the provided lookUpRelays.
 * If the relay list is found, it will be added to the user relay list metadata.
 * @param lookUpRelays
 * @param hexKey
 * @return found relay list or null
 */
const findRelayListAndUpdateCache = async (
  lookUpRelays: string[],
  hexKey: string
): Promise<Event | null> => {
  try {
    const eventFilter: Filter = {
      kinds: [RelayList],
      authors: [hexKey]
    }

    const event = await relayController.fetchEvent(eventFilter, lookUpRelays)
    if (event) {
      await localCache.addUserRelayListMetadata(event)
    }
    return event
  } catch (error) {
    console.error(error)
    return null
  }
}

/**
 * Attempts to find a relay list in cache. If it is present, it will check that the cached event is not
 * older than one week.
 * @param hexKey
 * @return RelayList event if it's not older than a week; otherwise null
 */
const findRelayListInCache = async (hexKey: string): Promise<Event | null> => {
  try {
    // Attempt to retrieve the metadata event from the local cache
    const cachedRelayListMetadataEvent =
      await localCache.getUserRelayListMetadata(hexKey)

    // Check if the cached event is not older than one week
    if (
      cachedRelayListMetadataEvent &&
      isOlderThanOneWeek(cachedRelayListMetadataEvent.cachedAt)
    ) {
      return cachedRelayListMetadataEvent.event
    }

    return null
  } catch (error) {
    console.error(error)
    return null
  }
}

/**
 * Transforms a list of relay tags from a Nostr Event to a RelaySet.
 * @param tags
 */
const getUserRelaySet = (tags: string[][]): RelaySet => {
  return tags
    .filter(isRelayTag)
    .reduce<RelaySet>(toRelaySet, getDefaultRelaySet())
}

const getDefaultRelaySet = (): RelaySet => ({
  read: [SIGIT_RELAY],
  write: [SIGIT_RELAY]
})

const getDefaultRelayMap = (): RelayMap => ({
  [SIGIT_RELAY]: { write: true, read: true }
})

const isOlderThanOneWeek = (cachedAt: number) => {
  return Date.now() - cachedAt < ONE_WEEK_IN_MS
}

const isRelayTag = (tag: string[]): boolean => tag[0] === 'r'

const toRelaySet = (obj: RelaySet, tag: string[]): RelaySet => {
  if (tag.length >= 3) {
    const marker = tag[2]

    if (marker === READ_MARKER) {
      obj.read.push(tag[1])
    } else if (marker === WRITE_MARKER) {
      obj.write.push(tag[1])
    }
  }
  if (tag.length === 2) {
    obj.read.push(tag[1])
    obj.write.push(tag[1])
  }

  return obj
}

/**
 * Provides most popular relays.
 * @param numberOfTopRelays - number representing how many most popular relays to provide
 * @returns - promise that resolves into an array of most popular relays
 */
const getMostPopularRelays = async (
  numberOfTopRelays: number = 30
): Promise<string[]> => {
  const mostPopularRelaysState = store.getState().relays?.mostPopular

  // return most popular relays from app state if present
  if (mostPopularRelaysState) return mostPopularRelaysState

  // relays in env
  const { VITE_MOST_POPULAR_RELAYS } = import.meta.env
  const hardcodedPopularRelays = (VITE_MOST_POPULAR_RELAYS || '').split(' ')
  const url = `https://stats.nostr.band/stats_api?method=stats`

  const response = await axios.get<RelayStats>(url).catch(() => undefined)

  if (!response) {
    return hardcodedPopularRelays //return hardcoded relay list
  }

  const data = response.data

  if (!data) {
    return hardcodedPopularRelays //return hardcoded relay list
  }

  const apiTopRelays = data.relay_stats.user_picks.read_relays
    .slice(0, numberOfTopRelays)
    .map((relay: RelayReadStats) => relay.d)

  if (!apiTopRelays.length) {
    return Promise.reject(`Couldn't fetch popular relays.`)
  }

  if (store.getState().auth?.loggedIn) {
    store.dispatch(setMostPopularRelaysAction(apiTopRelays))
  }

  return apiTopRelays
}

export {
  findRelayListAndUpdateCache,
  findRelayListInCache,
  getDefaultRelayMap,
  getDefaultRelaySet,
  getMostPopularRelays,
  getUserRelaySet,
  isOlderThanOneWeek
}