untis_telegram_bot

A service Telegram bot that periodically fetches schedules from Untis and posts status/notifications to a target chat. The workspace is split into three crates for clean layering:

• Root crate (src/) — orchestration: observers, worker lifecycle, message formatting (src/main.rs).
• db/ — PostgreSQL access with Diesel using an Active Record style API (db/src/models.rs).
• untis/ — Untis JSON‑RPC + REST client (untis/src/client.rs, untis/src/jsonrpc.rs).

Techniques used

• Active Record pattern on Diesel models: instance methods like insert(), update(), reload(), delete() in db/src/models.rs simplify data lifecycle and keep call sites clean.
• Optimistic concurrency: update_optimistic(expected_updated_at, changeset) gates updates on a version check (updated_at), reducing contention while preserving correctness.
• Lazy, global connection pool via OnceCell + r2d2 in db/src/diesel_impl.rs, providing a single thread‑safe pool for the process.
• Hybrid transport: JSON‑RPC for most methods, but direct REST for homeworks in untis/src/client.rs, extending beyond the public RPC surface.
• Structured async logging with environment‑driven filters (tracing + tracing-subscriber) and different production/debug formatters in src/main.rs.
• Worker orchestration with Tokio JoinSet: observer loop starts/stops workers based on DB state; crashed workers are restarted in the next tick.
• Periodic data hygiene: a daily cleanup task removes outdated lessons to keep tables lean.
• JSON encoding/decoding via serde with hand‑rolled JSON‑RPC envelopes in untis/src/jsonrpc.rs. For general JSON concepts see MDN JSON docs.
• Cookie handling and DNS options with reqwest (cookies, hickory‑dns). MDN reference for HTTP cookies: MDN HTTP cookies. For date/time concepts in client platforms, see MDN Intl.DateTimeFormat.

Notable libraries and tech

• Diesel (ORM) — diesel.rs
• r2d2 (pool) — crates.io/crates/r2d2
• Teloxide (Telegram bot framework) — github.com/teloxide/teloxide
• reqwest (HTTP client) — crates.io/crates/reqwest
• tracing — crates.io/crates/tracing
• serde / serde_json — serde.rs
• strum (derive for enums) — crates.io/crates/strum
• impl-tools (macro utilities) — crates.io/crates/impl-tools
• restructed (derive models/views/patches) — crates.io/crates/restructed

Source links referenced

• Observer & workers: src/main.rs
• Models and Active Record API: db/src/models.rs
• Connection pool and migrations bootstrap: db/src/diesel_impl.rs
• Untis high‑level client: untis/src/client.rs
• JSON‑RPC low‑level transport: untis/src/jsonrpc.rs