import { neventEncode, decode } from 'nostr-tools/nip19'
import {
  spec,
  sortBy,
  groupBy,
  displayList,
  secondsToDate,
} from '@welshman/lib'
import { parse, truncate, renderAsHtml } from '@welshman/content'
import {
  TrustedEvent,
  normalizeRelayUrl,
  getParentId,
  NOTE,
  COMMENT,
  REACTION,
  displayProfile,
  displayPubkey,
  getTagValue,
} from '@welshman/util'
import { displayDuration, createElement } from './util.js'
import type { Subscription } from './alert.js'
import { sendDigest } from './mailer.js'
import { EVENT_VIEWER_URL } from './env.js'
import {
  profilesByPubkey,
  loadProfile,
} from './repository.js'

type DigestData = {
  events: TrustedEvent[]
  context: TrustedEvent[]
  relayByEventId: Map<string, string>
}

export class Digest {
  since: number

  constructor(readonly sub: Subscription) {
    this.since = sub.last_digest_at || sub.created_at
  }

  loadHandler = async () => {
    // Default handler for building event links
    return `${EVENT_VIEWER_URL}/`
  }

  buildParameters = async (data: DigestData) => {
    const getEventVariables = (event: TrustedEvent) => {
      const parsed = truncate(parse(event), { minLength: 400, maxLength: 800, mediaLength: 50 })

      return {
        Link: buildLink(event, handler, data.relayByEventId.get(event.id)),
        Timestamp: formatter.format(secondsToDate(event.created_at)),
        Icon: profilesByPubkey.get().get(event.pubkey)?.picture,
        Name: displayProfileByPubkey(event.pubkey),
        Content: renderAsHtml(parsed, { createElement, renderEntity }).toString(),
        Replies:
          repliesByParentId.get(event.id)?.filter((e) => [COMMENT, NOTE].includes(e.kind))
            ?.length || 0,
        Reactions: repliesByParentId.get(event.id)?.filter(spec({ kind: REACTION }))?.length || 0,
      }
    }

    const { events, context } = data
    const formatter = getFormatter()
    const handler = await this.loadHandler()
    const repliesByParentId = groupBy(getParentId, context)
    const eventsByPubkey = groupBy((e) => e.pubkey, events)
    const userProfile = profilesByPubkey.get().get(this.sub.pubkey)
    const sorted = sortBy((e) => e.created_at, events).slice(0, 100)
    const topProfiles = sortBy(
      ([k, ev]) => -ev.length,
      Array.from(eventsByPubkey.entries()).filter(([k]) => profilesByPubkey.get().get(k))
    )

    return {
      Total: events.length,
      Duration: displayDuration(Math.floor(Date.now() / 1000) - this.since),
      Latest: sorted.map((e) => getEventVariables(e)),
      HasLatest: sorted.length > 0,
      UserName: displayProfile(userProfile, this.sub.email.split('@')[0]),
      TopProfiles: displayList(topProfiles.map(([pk]) => displayProfileByPubkey(pk))),
    }
  }

  sendFromStoredEvents = async (storedEvents: { id: string; event: TrustedEvent; relay: string }[]) => {
    const events = storedEvents.map(se => se.event)
    const context = [...events] // For now, context == events (no reply loading)
    const relayByEventId = new Map(storedEvents.map(se => [se.event.id, se.relay]))

    // Load profiles for event authors
    const pubkeys = new Set(events.map(e => e.pubkey))
    pubkeys.add(this.sub.pubkey)
    for (const pk of pubkeys) {
      try {
        await loadProfile(pk)
        await waitForProfile(pk)
      } catch {
        // pass
      }
    }

    const data = { events, context, relayByEventId } as DigestData

    if (data.events.length > 0) {
      await sendDigest(this.sub, await this.buildParameters(data))
    }
  }
}

// Utilities

const buildLink = (event: TrustedEvent, handler: string, storedRelay?: string) => {
  const relays = storedRelay ? [storedRelay] : []

  const groupId = getTagValue(["h"], event.tags)

  if (groupId && relays.length > 0) {
    const relay = encodeRelay(relays[0])
    const nevent = neventEncode({ id: event.id, relays })
    return `${handler}spaces/${relay}/${encodeURIComponent(groupId)}?at=${event.created_at}#${nevent}`
  }

  const nevent = neventEncode({ ...event, relays })

  if (handler.includes('<bech32>')) {
    return handler.replace('<bech32>', nevent)
  } else {
    return handler + nevent
  }
}

const encodeRelay = (url: string) =>
  encodeURIComponent(
    normalizeRelayUrl(url)
      .replace(/^wss:\/\//, '')
      .replace(/\/$/, ''),
  )

const displayProfileByPubkey = (pubkey: string) =>
  displayProfile(profilesByPubkey.get().get(pubkey), displayPubkey(pubkey))

const renderEntity = (entity: string) => {
  let display = entity.slice(0, 16) + '…'

  try {
    const { type, data } = decode(entity)

    if (type === 'npub') {
      display = '@' + displayProfileByPubkey(data)
    }

    if (type === 'nprofile') {
      display = '@' + displayProfileByPubkey(data.pubkey)
    }
  } catch (e) {
    // Pass
  }

  return display
}

const getFormatter = () => {
  return new Intl.DateTimeFormat('en-US', {
    dateStyle: 'short',
    timeStyle: 'short',
    timeZone: 'UTC',
  })
}

// Poll until the profile lands in the repository or hits a timeout. The load
// promise can resolve before sharedLoad writes the event to the store, so only
// the profile's presence here guarantees its avatar/name.
const waitForProfile = async (pubkey: string, timeoutMs = 5000) => {
  const deadline = Date.now() + timeoutMs

  while (Date.now() < deadline) {
    if (profilesByPubkey.get().get(pubkey)) {
      return
    }
    await new Promise(r => setTimeout(r, 200))
  }
}