AGENTS.md

Scope

This file applies to the Rust workspace at digitemp-rrdgraph/.

The binary provides three operational subcommands: update, check-alert, and send-info.
The repository is a Cargo workspace with a CLI crate at the repository root and an internal library crate at crates/core/ named digitemp_rrdgraph_core.
The system depends on external commands and resources: digitemp, rrdtool, SMTP, JSON config files under etc/, Tera templates under templates/, generated graphs under html/images/, and RRD files under db/.

Treat this Rust repository as the sole implementation and documentation target.
Preserve the CLI contract exposed by src/main.rs, the command modules under src/commands/, and the public interfaces exposed by crates/core/src/lib.rs unless the user explicitly requests a behavior change.
Preserve the configuration schema in etc/config.sample.json unless the user explicitly asks for a breaking change.
Preserve template variable names expected by templates/*.tera unless the templates are updated in the same change.

Write repository documentation such as AGENTS.md, README.md, and other project documents in English by default.
When adding comments to source code, configuration files, templates, or scripts, write those comments in English.
Keep user-facing configuration keys, template names, and command names stable unless the task explicitly requires a change.

Prefer fixes at the behavior or interface boundary, not cosmetic refactors.
Keep CLI behavior and config keys stable.
Keep changes small and local to the affected command or library module.
Avoid introducing new crates unless the standard library or existing dependencies are clearly insufficient.
Prefer explicit error propagation with Result over unwrap or expect in runtime paths.

Do not edit generated or runtime data under target/, db/, or html/images/ unless the task explicitly requires it.
Do not overwrite etc/digitemp-rrdgraph.conf for convenience; use etc/config.sample.json as the editable reference.
Be careful with commands that can talk to real hardware, modify RRD files, or send email.
When validation would invoke external systems, prefer build-only or isolated checks unless the user explicitly wants end-to-end execution.

After Rust code changes, run cargo build in this repository at minimum. Prefer cargo build --workspace when changes affect crates/core/ or workspace wiring.
If you add or refactor logic that can be unit tested without hardware or SMTP, add focused tests and run them.
Prefer tests around pure logic such as config parsing, digitemp config parsing, template rendering, and any command-argument construction helpers.
If a change depends on hardware access or local services, state clearly what could not be verified.

Keep path handling relative to the repository root unless a config field explicitly stores an absolute path.
Encapsulate shell command construction so it can be inspected or tested without executing the command.
Match existing naming and module boundaries under src/commands/ and crates/core/src/.
Keep CLI-only orchestration in the root crate and reusable logic in digitemp_rrdgraph_core.
Prefer direct, maintainable implementations over compatibility layers or unnecessary abstraction.