4.6 overlap membership

lib/epochs/get-members.js

@@ -0,0 +1,117 @@
+// SPDX-FileCopyrightText: 2022 Mix Irving
+//
+// SPDX-License-Identifier: LGPL-3.0-only
+
+const { promisify: p } = require('util')
+const pull = require('pull-stream')
+const pullDefer = require('pull-defer')
+const clarify = require('clarify-error')
+const {
+  validator: {
+    group: { addMember: isAddMember, excludeMember: isExcludeMember },
+  },
+} = require('private-group-spec')
+const { fromMessageSigil } = require('ssb-uri2')
+
+const getTangleUpdates = require('../tangles/get-tangle-updates')
+
+function toMsgURI(id) {
+  return id.startsWith('%') ? fromMessageSigil(id) : id
+}
+
+module.exports = function GetMembers(ssb) {
+  function getMembers(epochRootId, cb) {
+    if (cb === undefined) return p(getMembers)(epochRootId)
+
+    epochRootId = toMsgURI(epochRootId)
+    const added = new Set()
+    const toExclude = new Set()
+
+    pull(
+      getTangleUpdates.stream(ssb, 'members', epochRootId),
+      pull.filter((msg) => isAddMember(msg) || isExcludeMember(msg)),
+      pull.through((msg) => {
+        const { type, recps, excludes } = msg.value.content
+        if (type === 'group/add-member')
+          recps.slice(1).forEach((feedId) => added.add(feedId))
+        else return excludes.forEach((feedId) => toExclude.add(feedId))
+      }),
+      pull.collect((err) => {
+        if (err) return cb(clarify(err, 'Failed to resolve epoch membership'))
+
+        cb(null, {
+          added: [...added],
+          toExclude: [...toExclude],
+        })
+      })
+    )
+  }
+  getMembers.stream = function getMembersStream(epochRootId, opts = {}) {
+    const { live } = opts
+
+    const deferredSource = pullDefer.source()
+
+    getMembers(epochRootId, (err, res) => {
+      // prettier-ignore
+      if (err) return deferredSource.abort(clarify(err, 'error getting members'))
+
+      if (!live) {
+        deferredSource.resolve(pull.once(res))
+        return
+      }
+
+      const added = new Set(res.added)
+      const toExclude = new Set(res.toExclude)
+
+      const source = pull(
+        // create a stream of "there is an update" events
+        pull.values([
+          // one event for current state
+          pull.once(true),
+
+          // run a live stream, only emiting "true" if there is new info in the
+          // message that comes in
+          pull(
+            getTangleUpdates.stream(ssb, 'members', epochRootId, { live }),
+            pull.map((msg) => {
+              if (isAddMember(msg)) {
+                const initialSize = added.size
+                msg.value.content.recps
+                  .slice(1)
+                  .forEach((feedId) => added.add(feedId))
+                return added.size > initialSize
+              }
+
+              if (isExcludeMember(msg)) {
+                const initialSize = toExclude.size
+                msg.value.content.excludes.forEach((feedId) =>
+                  toExclude.add(feedId)
+                )
+                return toExclude.size > initialSize
+              }
+
+              return false
+            }),
+            pull.filter(Boolean)
+          ),
+        ]),
+        pull.flatten(),
+
+        // for each "there is an update" event, map that to emitting the current
+        // membereship state of the epoch
+        pull.map(() => {
+          return {
+            added: [...added],
+            toExclude: [...toExclude],
+          }
+        })
+      )
+
+      return deferredSource.resolve(source)
+    })
+
+    return deferredSource
+  }
+
+  return getMembers
+}