epson-exporter

Imported from woodleighschool/epson-exporter (AGENTS.md). Install upstream with npx skills add woodleighschool/epson-exporter. Copyright stays with the author.

AGENTS.md

Guidance for agents and humans working in this repository. This file is self-contained. Check the repository's source, Mise configuration, Lefthook configuration, and workflows for facts that can vary instead of copying versions or commands from another project.

Working here

• Read the relevant code, configuration, tests, and nearby examples before editing. Existing code and reference implementations are evidence; understand the invariant and ownership boundary before choosing a solution.
• Target current supported behaviour. Prefer the simplest design that reduces state and machinery, and bring the affected path into conformance when existing code disagrees with this baseline.
• Preserve unrelated work. Keep changes focused, remove artifacts orphaned by the change, and keep generated outputs with their source change.
• Verify dependency APIs, flags, and defaults from the pinned source or primary documentation.
• Keep secrets, credentials, real identities, production data, and local environment files out of source, fixtures, logs, and commits.

Baseline

• Write idiomatic, modern code for the versions pinned by this repository.
• Keep operations idempotent. Re-running a command, generator, reconciler, or migration with identical input shouldn't accumulate side effects.
• Stay DRY and minimal without premature abstraction. Three similar call sites are fine; add a helper, interface, options type, or generic abstraction when real callers need the variance it provides.
• Comments explain non-obvious constraints, invariants, and external requirements. Names and structure carry the ordinary narrative.
• Do not add file banners, author or date headers, or comment-based change logs. Git owns provenance and history.
• Write prose from the repository's point of view. Use we and our for the organisation, and the app, the service, the command, or direct wording for this repository. Omit organisation and product names when context already identifies them; keep names that are identifiers or distinguish an external system.
• Keep tracked documentation durable and present-tense. READMEs use a terse introduction and the relevant established emoji-led sections; omit migration history, temporary setup state, and inventories of absent features.
• Keep one-time local and external-service setup notes out of tracked files. If asked to preserve them locally, leave them untracked without adding ignore or exclude rules.
• Tests protect behaviour and contracts at the lowest useful boundary. Use realistic synthetic inputs and add regression coverage for plausible failures rather than implementation shape.

Repository tooling

• Mise owns tools and commands. Run mise tasks and read .mise/config.toml before choosing task names or invoking bare tools.
• Lefthook extends the shared organisation configuration. Read .lefthook.toml and use lefthook dump when merged hook behaviour matters; local hooks contain only repository-specific additions.
• Run focused checks while working, then the relevant repository format, lint, test, build, generation, workflow, packaging, and security tasks before calling the work complete.
• Treat generated files, schemas, lockfiles, release metadata, and package assets as part of the contract that produces them.

Go

• Follow Effective Go and Go Code Review Comments. Let gofmt -s own formatting.
• go.mod declares the language floor; Mise pins the toolchain used by local tasks and CI. Use modern standard-library constructs supported by the declared version.
• Put executable composition in cmd/<app>/main.go and owned behaviour under internal. Keep main to configuration, logging, dependency construction, lifecycle, and exit status.
• Use github.com/caarlos0/env/v11 for application-owned environment configuration. Parse into one config type, derive and validate in one load boundary, and fail at startup. Document config fields with their purpose and meaningful defaults.
• Use github.com/spf13/pflag for application-owned flags and Cobra when the CLI has commands or more than a small flag surface. Structured files suit user-authored domain configuration; all sources converge on one validation path.
• Use log/slog and structured stdout logging. Configure logging once at composition; use package-level logging or inject *slog.Logger at a genuine reusable boundary.
• Wrap errors with fmt.Errorf("<component>: %w", err). Use sentinel errors for conditions callers branch on and classify errors once at the HTTP, CLI, job, or protocol boundary.
• Functions that perform I/O take context.Context first and propagate cancellation. Long-running processes use signal-aware root contexts and bounded shutdown; use errgroup for related goroutines that can fail.
• Prefer standard-library tests and table-driven subtests when a table makes cases clearer. Keep the package's established test framework, use local servers or fakes at real boundaries, and run race-enabled tests for concurrent code.
• Containerized Go services default to static, trimmed binaries and a non-root minimal runtime. Run the repository's vulnerability task for dependency and release work.

Git and completion

• Use focused Conventional Commits; Release Please derives versions from them where configured.
• Commit, push, publish, deploy, contact live systems, or perform destructive operations only when explicitly requested.
• Report the checks run, behaviour changed, generated outputs refreshed, and any verification that couldn't be completed.

Repository contract

• Prometheus exporter-toolkit, Kingpin, and promslog own the conventional exporter CLI, web listener, and logging surface.
• Keep Epson transport and parsing separate from metric collection. Metric names, labels, and meanings are public scrape contracts.
• Tests use captured responses and local servers. Configuration modules carry scrape policy and HTTP client behaviour through one validation path.