[Session] Logging (#4476)

* Add session logging (console.log)

* Hook it up for real

* Send type separately

src/state/session/logging.ts

@@ -0,0 +1,137 @@
+import {AtpSessionData} from '@atproto/api'
+import {sha256} from 'js-sha256'
+import {Statsig} from 'statsig-react-native-expo'
+
+import {Schema} from '../persisted'
+import {Action, State} from './reducer'
+import {SessionAccount} from './types'
+
+type Reducer = (state: State, action: Action) => State
+
+type Log =
+  | {
+      type: 'reducer:init'
+      state: State
+    }
+  | {
+      type: 'reducer:call'
+      action: Action
+      prevState: State
+      nextState: State
+    }
+  | {
+      type: 'method:start'
+      method:
+        | 'createAccount'
+        | 'login'
+        | 'logout'
+        | 'resumeSession'
+        | 'removeAccount'
+      account?: SessionAccount
+    }
+  | {
+      type: 'method:end'
+      method:
+        | 'createAccount'
+        | 'login'
+        | 'logout'
+        | 'resumeSession'
+        | 'removeAccount'
+      account?: SessionAccount
+    }
+  | {
+      type: 'persisted:broadcast'
+      data: Schema['session']
+    }
+  | {
+      type: 'persisted:receive'
+      data: Schema['session']
+    }
+  | {
+      type: 'agent:switch'
+      prevAgent: object
+      nextAgent: object
+    }
+  | {
+      type: 'agent:patch'
+      agent: object
+      prevSession: AtpSessionData | undefined
+      nextSession: AtpSessionData
+    }
+
+export function wrapSessionReducerForLogging(reducer: Reducer): Reducer {
+  return function loggingWrapper(prevState: State, action: Action): State {
+    const nextState = reducer(prevState, action)
+    addSessionDebugLog({type: 'reducer:call', prevState, action, nextState})
+    return nextState
+  }
+}
+
+let nextMessageIndex = 0
+const MAX_SLICE_LENGTH = 1000
+
+export function addSessionDebugLog(log: Log) {
+  try {
+    if (!Statsig.initializeCalled() || !Statsig.getStableID()) {
+      // Drop these logs for now.
+      return
+    }
+    if (!Statsig.checkGate('debug_session')) {
+      return
+    }
+    const messageIndex = nextMessageIndex++
+    const {type, ...content} = log
+    let payload = JSON.stringify(content, replacer)
+
+    let nextSliceIndex = 0
+    while (payload.length > 0) {
+      const sliceIndex = nextSliceIndex++
+      const slice = payload.slice(0, MAX_SLICE_LENGTH)
+      payload = payload.slice(MAX_SLICE_LENGTH)
+      Statsig.logEvent('session:debug', null, {
+        realmId,
+        messageIndex: String(messageIndex),
+        messageType: type,
+        sliceIndex: String(sliceIndex),
+        slice,
+      })
+    }
+  } catch (e) {
+    console.error(e)
+  }
+}
+
+let agentIds = new WeakMap<object, string>()
+let realmId = Math.random().toString(36).slice(2)
+let nextAgentId = 1
+
+function getAgentId(agent: object) {
+  let id = agentIds.get(agent)
+  if (id === undefined) {
+    id = realmId + '::' + nextAgentId++
+    agentIds.set(agent, id)
+  }
+  return id
+}
+
+function replacer(key: string, value: unknown) {
+  if (typeof value === 'object' && value != null && 'api' in value) {
+    return getAgentId(value)
+  }
+  if (
+    key === 'service' ||
+    key === 'email' ||
+    key === 'emailConfirmed' ||
+    key === 'emailAuthFactor' ||
+    key === 'pdsUrl'
+  ) {
+    return undefined
+  }
+  if (
+    typeof value === 'string' &&
+    (key === 'refreshJwt' || key === 'accessJwt')
+  ) {
+    return sha256(value)
+  }
+  return value
+}