flotilla/src/app/social.ts

import {derived} from "svelte/store"
import {pushToMapKey, removeUndefined, shuffle, sortBy, uniqBy} from "@welshman/lib"
import {
  COMMENT,
  addressTags,
  getAddress,
  getIdAndAddress,
  hexTags,
  tagSpec,
  tagValues,
  topicTags,
} from "@welshman/util"
import type {TrustedEvent} from "@welshman/util"
import {withGetter} from "@welshman/store"
import {getCommentTagValues, getReplyTagValues} from "@welshman/domain"
import {FollowLists, MuteLists} from "@welshman/app"
import {deriveUserItem, profiles, user} from "@app/core"
import {DEFAULT_PUBKEYS} from "@app/env"

// The display names for a group of people, as a store rather than a snapshot. A display starts
// out as the author's npub and only becomes their name once the profile loads, so reading it once
// leaves a name frozen as bech32 — and reading it that way never asks for the profile at all.
export const deriveDisplaysByPubkey = (pubkeys: string[], url?: string) =>
  derived(
    pubkeys.map(pubkey => profiles.get().display(pubkey, removeUndefined([url])).$),
    displays => new Map(pubkeys.map((pubkey, i) => [pubkey, displays[i]])),
    new Map<string, string>(),
  )

export const bootstrapPubkeys = derived(deriveUserItem(FollowLists), $userFollowList => {
  const appPubkeys = DEFAULT_PUBKEYS.split(",")
  const userPubkeys = shuffle($userFollowList?.pubkeys() ?? [])

  return userPubkeys.length > 5 ? userPubkeys : [...userPubkeys, ...appPubkeys]
})

// Ids and addresses of an event's immediate parents, falling back to its thread roots.
const getParents = ({kind, tags}: TrustedEvent) => {
  const {roots, replies} = kind === COMMENT ? getCommentTagValues(tags) : getReplyTagValues(tags)

  return replies.length > 0 ? replies : roots
}

export type CommentNode = {
  comment: TrustedEvent
  children: CommentNode[]
}

export const buildCommentTree = (root: TrustedEvent, comments: TrustedEvent[]) => {
  const byParent = new Map<string, TrustedEvent[]>()

  // A comment names its parent by id, and by address too when the parent is addressable, so
  // index it under every value it gives and dedupe on the way back out.
  for (const comment of comments) {
    for (const parent of getParents(comment)) {
      pushToMapKey(byParent, parent, comment)
    }
  }

  // Nothing stops a comment from naming several parents, which would let the tree cycle, so
  // walk down from the root and keep each comment at the first place it turns up.
  const seen = new Set<string>()

  const build = (parent: TrustedEvent): CommentNode[] => {
    const children = uniqBy(
      e => e.id,
      getIdAndAddress(parent).flatMap(value => byParent.get(value) ?? []),
    ).filter(e => !seen.has(e.id))

    for (const child of children) {
      seen.add(child.id)
    }

    return children.map(comment => ({comment, children: build(comment)}))
  }

  const nodes = build(root)

  // A comment can name a parent we don't have — a superseded version of an addressable root,
  // or a parent that failed to load — so adopt whatever's left rather than dropping it.
  // `comments` is oldest first, so a parent is always adopted before its own children.
  for (const comment of comments) {
    if (!seen.has(comment.id)) {
      seen.add(comment.id)
      nodes.push({comment, children: build(comment)})
    }
  }

  return sortBy(node => node.comment.created_at, nodes)
}

export const isEventMuted = withGetter(
  derived([user, deriveUserItem(MuteLists)], ([$user, $muteList]) => {
    const tags = $muteList?.tags() ?? []
    const mutedEvents = new Set(tagValues(hexTags("e"), tags))
    const mutedPubkeys = new Set(tagValues(hexTags("p"), tags))
    const mutedAddresses = new Set(tagValues(addressTags("a"), tags))
    const mutedTopics = new Set(tagValues(topicTags("t"), tags))
    const mutedWords = tagValues(tagSpec("word"), tags)
    const regex =
      mutedWords.length > 0
        ? new RegExp(`\\b(${mutedWords.map(w => w.toLowerCase().trim()).join("|")})\\b`)
        : undefined

    return (e: TrustedEvent) => {
      if (!$muteList) return false
      if ($user.pubkey === e.pubkey) return false
      if (mutedPubkeys.has(e.pubkey)) return true
      if (mutedEvents.has(e.id)) return true
      if (mutedAddresses.has(getAddress(e))) return true
      if (getParents(e).some(v => mutedEvents.has(v) || mutedAddresses.has(v))) return true
      if (tagValues(topicTags("t"), e.tags).some(t => mutedTopics.has(t))) return true

      if (regex) {
        const profile = profiles.get().get(e.pubkey)

        if (profile?.display().toLowerCase().match(regex)) return true
        if (profile?.nip05()?.match(regex)) return true
      }

      return false
    }
  }),
)