gatewayd: mm, Mattermost's events and REST calls, typed
Implemented-By: OpenCode session (model recorded in docs/implementer-log.md)
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//! Mattermost's JSON, typed: the posts and users we read, the events that arrive over the
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//! WebSocket, and the requests we send over it. Mattermost's JSON is not ours: unknown fields are
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//! ignored, but every id we keep must be a valid id.
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pub mod rest;
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use std::time::Duration;
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use serde::Deserialize;
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use crate::config::valid_id;
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/// At most this many changed posts come back from one `posts?since` call (Mattermost v11.11.0,
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/// `SqlPostStore::GetPostsSince`); a full answer may have left some out.
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pub const SINCE_LIMIT: usize = 1000;
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#[derive(Debug)]
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pub enum MmError {
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/// No answer: connecting, TLS, or the HTTP exchange failed.
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Net(String),
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/// 401 or 403: the token is refused.
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Auth(u16),
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/// 429, still, after waiting as asked.
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RateLimited(Duration),
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/// Any other status that is not 2xx, with the start of the body.
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Status(u16, String),
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/// The answer is not the JSON we expect.
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Json(String),
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}
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impl std::fmt::Display for MmError {
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fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
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match self {
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MmError::Net(why) => write!(f, "{why}"),
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MmError::Auth(status) => write!(f, "Mattermost refused the token ({status})"),
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MmError::RateLimited(wait) => {
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write!(f, "rate limited; asked to wait {} s", wait.as_secs())
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}
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// Quoted: the body is the server's text, and must not forge a log line.
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MmError::Status(status, body) => write!(f, "status {status}: {body:?}"),
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MmError::Json(why) => write!(f, "unexpected JSON: {why}"),
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}
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}
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}
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impl std::error::Error for MmError {}
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/// This bot, from `GET /users/me`.
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#[derive(Debug, Clone, PartialEq, Eq, Deserialize)]
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pub struct Me {
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pub id: String,
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pub username: String,
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}
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/// The fields of a post that `gatewayd` uses.
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#[derive(Debug, Clone, PartialEq, Eq, Deserialize)]
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pub struct Post {
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pub id: String,
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pub user_id: String,
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pub channel_id: String,
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#[serde(default)]
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pub root_id: String,
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#[serde(default)]
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pub message: String,
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pub create_at: i64,
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#[serde(default)]
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pub delete_at: i64,
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/// Empty for a message a user wrote; anything else is a system message.
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#[serde(default, rename = "type")]
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pub kind: String,
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}
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impl Post {
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/// Every id is a Mattermost id (the root may be empty): they end up in session ids and paths.
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pub(crate) fn check(self) -> Result<Post, MmError> {
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// id, user_id and channel_id must be `valid_id`, and root_id empty or `valid_id`; otherwise
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// Json("a post with an invalid id: <id quoted with {:?}>").
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if !valid_id(&self.id) || !valid_id(&self.user_id) || !valid_id(&self.channel_id) {
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return Err(MmError::Json(format!(
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"a post with an invalid id: {:?}",
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self.id
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)));
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}
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if !self.root_id.is_empty() && !valid_id(&self.root_id) {
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return Err(MmError::Json(format!(
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"a post with an invalid id: {:?}",
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self.root_id
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)));
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}
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Ok(self)
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}
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}
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/// An event from the WebSocket.
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#[derive(Debug, Clone, PartialEq, Eq)]
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pub enum Event {
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Hello,
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/// A new post, and the type of its channel: `D` direct, `G` group, `O` open, `P` private.
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Posted {
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post: Post,
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channel_type: String,
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},
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/// Any other event, or a reply to one of our requests, by its name (empty for a reply).
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Other(String),
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}
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#[derive(Deserialize)]
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struct RawEvent {
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#[serde(default)]
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event: String,
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#[serde(default)]
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data: serde_json::Map<String, serde_json::Value>,
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}
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pub(crate) fn json<T: serde::de::DeserializeOwned>(bytes: &[u8]) -> Result<T, MmError> {
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// `serde_json::from_slice`; its error becomes Json(e.to_string()).
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serde_json::from_slice(bytes).map_err(|e| MmError::Json(e.to_string()))
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}
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/// One WebSocket text message as an event. `posted` carries the post as a JSON **string**.
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pub fn parse_event(text: &str) -> Result<Event, MmError> {
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// Parse into RawEvent. "hello" -> Hello. "posted" -> data.post must be a JSON *string*; parse
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// that string as a Post and `check` it (a missing or non-string post is Json). channel_type is
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// data.channel_type when it is a string, else "". Any other event name -> Other(name) (a reply
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// has no event: Other("")).
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let raw: RawEvent = json(text.as_bytes())?;
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match raw.event.as_str() {
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"hello" => Ok(Event::Hello),
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"posted" => {
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let post = raw
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.data
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.get("post")
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.and_then(|p| p.as_str())
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.ok_or_else(|| {
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MmError::Json("a posted event carries no post string".to_string())
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})?;
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let post: Post = json(post.as_bytes())?;
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let channel_type = raw
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.data
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.get("channel_type")
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.and_then(|c| c.as_str())
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.unwrap_or("")
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.to_string();
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Ok(Event::Posted {
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post: post.check()?,
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channel_type,
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})
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}
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other => Ok(Event::Other(other.to_string())),
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}
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}
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/// The WebSocket request that shows this bot as typing in a thread (`parent` is the root).
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pub fn typing(seq: u64, channel: &str, parent: &str) -> String {
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// serde_json::json!({"action": "user_typing", "seq": seq, "data": {"channel_id": channel,
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// "parent_id": parent}}) as a string.
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serde_json::json!({
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"action": "user_typing",
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"seq": seq,
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"data": {"channel_id": channel, "parent_id": parent}
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})
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.to_string()
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}
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/// What a `posts?since` call gave back.
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#[derive(Debug, Clone, PartialEq, Eq)]
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pub struct Since {
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/// Posts created after the time, not deleted, oldest first.
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pub posts: Vec<Post>,
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/// Mattermost's limit was reached: some posts may be missing.
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pub full: bool,
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}
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#[derive(Deserialize)]
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struct PostList {
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#[serde(default)]
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order: Vec<String>,
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#[serde(default)]
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posts: std::collections::HashMap<String, Post>,
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}
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/// The body of `GET /channels/{id}/posts?since=<since>`. Only ids in `order` changed after
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/// `since`; `posts` also holds the roots of their threads, which may be older. Edited and deleted
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/// posts come back too: only new posts count.
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pub fn since_list(body: &[u8], since: i64) -> Result<Since, MmError> {
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// Parse a PostList. full = order.len() >= SINCE_LIMIT. For each id in `order` (never the keys
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// of `posts`), skip it if it is not in `posts`; keep the post if create_at > since and
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// delete_at == 0, after `check`. Sort by (create_at, id), remove repeated ids.
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let list: PostList = json(body)?;
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let full = list.order.len() >= SINCE_LIMIT;
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let mut seen = std::collections::HashSet::new();
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let mut posts = Vec::new();
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for id in &list.order {
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let post = match list.posts.get(id) {
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Some(p) => p.clone(),
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None => continue,
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};
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let post = post.check()?;
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if post.create_at <= since || post.delete_at != 0 {
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continue;
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}
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if seen.insert(post.id.clone()) {
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posts.push(post);
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}
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}
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posts.sort_by(|a, b| a.create_at.cmp(&b.create_at).then_with(|| a.id.cmp(&b.id)));
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Ok(Since { posts, full })
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}
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