gatewayd: mm, Mattermost's events and REST calls, typed
Implemented-By: OpenCode session (model recorded in docs/implementer-log.md)
This commit is contained in:
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//! Mattermost's REST calls, one connection per request, with the token in the `Authorization`
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//! header. A 429 waits as asked; a 5xx is tried twice more; a 401 or 403 is `Auth` at once.
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use std::time::{Duration, SystemTime};
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use serde::Deserialize;
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use crate::config::valid_id;
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use crate::http::{self, Response, rate_limit_wait};
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use crate::mm::{Me, MmError, Post, Since, json, since_list};
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use crate::net::Connector;
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use crate::secrets::Secret;
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use crate::ws::conn::host_header;
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/// The pause before trying a call again after a 5xx.
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pub const RETRY_5XX: Duration = Duration::from_millis(500);
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/// How many times a call is tried again after a 5xx, and waits after a 429.
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pub const RETRIES: u32 = 2;
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/// How much of an error body is kept for the message.
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const BODY_KEPT: usize = 200;
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pub struct Client {
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connector: Connector,
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token: Secret,
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timeout: Duration,
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}
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#[derive(Deserialize)]
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struct Channel {
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id: String,
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}
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impl Client {
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/// `timeout` bounds connecting and each read: no bytes for that long is an error.
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pub fn new(connector: Connector, token: Secret, timeout: Duration) -> Client {
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// Store the three.
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Client {
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connector,
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token,
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timeout,
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}
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}
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pub fn connector(&self) -> &Connector {
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// The Connector.
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&self.connector
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}
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pub fn token(&self) -> &Secret {
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// The Secret.
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&self.token
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}
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fn once(&self, method: &str, path: &str, body: Option<&[u8]>) -> Result<Response, MmError> {
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// 1. `self.connector.connect(self.timeout)`, then `set_read_timeout(Some(self.timeout))`.
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let mut stream = self
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.connector
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.connect(self.timeout)
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.map_err(|e| MmError::Net(format!("{method} {path}: {e}")))?;
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stream
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.set_read_timeout(Some(self.timeout))
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.map_err(|e| MmError::Net(format!("{method} {path}: {e}")))?;
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// 2. Headers: Authorization "Bearer <token>" (the only use of `expose`), Accept
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// "application/json", and Content-Type "application/json" when there is a body. Host is
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// `host_header(self.connector.server())`.
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let auth = format!("Bearer {}", self.token.expose());
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let mut headers: Vec<(&str, &str)> = vec![
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("Authorization", auth.as_str()),
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("Accept", "application/json"),
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];
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if body.is_some() {
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headers.push(("Content-Type", "application/json"));
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}
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// 3. `http::request`. Every error on the way is Net("<method> <path>: <error>").
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http::request(
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&mut stream,
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method,
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&host_header(self.connector.server()),
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path,
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&headers,
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body,
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)
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.map_err(|e| MmError::Net(format!("{method} {path}: {e}")))
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}
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/// One call, tried again as the module comment says; the body of a 2xx answer.
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fn call(&self, method: &str, path: &str, body: Option<&[u8]>) -> Result<Vec<u8>, MmError> {
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// Loop over `once`: 2xx -> the body. 401 or 403 -> Auth(status) at once. 429 -> after
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// RETRIES waits already, RateLimited(wait); else sleep `rate_limit_wait(&head,
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// SystemTime::now())` and try again. 5xx -> up to RETRIES more tries, sleeping RETRY_5XX
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// before each. Anything else -> Status(status, the first BODY_KEPT characters of the body,
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// lossy UTF-8).
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let mut tries: u32 = 0;
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loop {
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let answer = self.once(method, path, body)?;
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let status = answer.head.status;
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if (200..300).contains(&status) {
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return Ok(answer.body);
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}
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match status {
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401 | 403 => return Err(MmError::Auth(status)),
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429 => {
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let wait = rate_limit_wait(&answer.head, SystemTime::now());
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if tries < RETRIES {
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tries += 1;
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std::thread::sleep(wait);
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continue;
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}
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return Err(MmError::RateLimited(wait));
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}
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_ if status >= 500 => {
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if tries < RETRIES {
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tries += 1;
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std::thread::sleep(RETRY_5XX);
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continue;
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}
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return Err(status_error(status, &answer.body));
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}
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_ => return Err(status_error(status, &answer.body)),
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}
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}
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}
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/// `GET /api/v4/users/me`: who this token is.
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pub fn me(&self) -> Result<Me, MmError> {
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// GET /api/v4/users/me into Me; an id that is not `valid_id` or an empty username is Json.
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let body = self.call("GET", "/api/v4/users/me", None)?;
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let me: Me = json(&body)?;
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if !valid_id(&me.id) || me.username.is_empty() {
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return Err(MmError::Json(
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"the user me has no id or no username".to_string(),
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));
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}
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Ok(me)
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}
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/// `POST /api/v4/posts`: a post in `channel`, in the thread of `root` (empty: top level).
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pub fn create_post(&self, channel: &str, root: &str, message: &str) -> Result<Post, MmError> {
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// POST /api/v4/posts with {"channel_id", "root_id", "message"}; the answer is a Post,
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// `check`ed.
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let payload = serde_json::json!({
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"channel_id": channel,
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"root_id": root,
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"message": message
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})
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.to_string();
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let body = self.call("POST", "/api/v4/posts", Some(payload.as_bytes()))?;
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let post: Post = json(&body)?;
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post.check()
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}
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/// `GET /api/v4/channels/{channel}/posts?since=<ms>`: the posts created after `since`.
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pub fn posts_since(&self, channel: &str, since: i64) -> Result<Since, MmError> {
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// A channel that is not `valid_id` is Json, and nothing is sent. Otherwise GET
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// /api/v4/channels/<channel>/posts?since=<since>, through `since_list`.
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if !valid_id(channel) {
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return Err(MmError::Json(
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"a channel path must be a Mattermost id".to_string(),
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));
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}
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let body = self.call(
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"GET",
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&format!("/api/v4/channels/{channel}/posts?since={since}"),
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None,
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)?;
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since_list(&body, since)
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}
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/// `POST /api/v4/channels/direct`: the id of the direct channel between two users.
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pub fn direct_channel(&self, a: &str, b: &str) -> Result<String, MmError> {
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// POST /api/v4/channels/direct with the JSON array [a, b]; the answer has an "id", which
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// must be `valid_id` (else Json).
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let payload = serde_json::to_vec(&serde_json::json!([a, b]))
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.map_err(|e| MmError::Json(e.to_string()))?;
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let body = self.call("POST", "/api/v4/channels/direct", Some(payload.as_slice()))?;
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let channel: Channel = json(&body)?;
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if !valid_id(&channel.id) {
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return Err(MmError::Json("the direct channel has no id".to_string()));
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}
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Ok(channel.id)
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}
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}
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fn status_error(status: u16, body: &[u8]) -> MmError {
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// Any non-2xx, non-4xx-that-isn't-401/403/429/5xx: the status and the first `BODY_KEPT`
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// characters, lossy UTF-8.
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MmError::Status(
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status,
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String::from_utf8_lossy(body)
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.chars()
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.take(BODY_KEPT)
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.collect(),
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)
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}
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