brewlog/CLAUDE.md

Claude Code Guidelines for Brewlog

Project Overview

Brewlog is a self-hosted coffee logging platform built in Rust. It provides:

• HTTP server with web UI (Axum + Askama templates + Datastar)
• REST API for programmatic access
• CLI client for command-line operations
• SQLite/PostgreSQL database support (feature-flagged)

Build & Test Commands

cargo build                    # Build the project
cargo test                     # Run all tests
cargo clippy --allow-dirty --fix  # Lint and auto-fix
cargo fmt                      # Format code

Before committing: Always run cargo clippy --allow-dirty --fix && cargo fmt and fix any issues.

Architecture

The codebase follows Clean Architecture / Domain-Driven Design with four layers:

src/
├── domain/           # Pure business logic, no external dependencies
│   ├── errors.rs     # RepositoryError enum
│   ├── ids.rs        # Typed ID wrappers (RoasterId, RoastId, BagId)
│   ├── repositories.rs  # Repository traits
│   └── {entity}.rs   # Entity definitions (roasters, roasts, bags, etc.)
│
├── infrastructure/   # External integrations (database, HTTP client)
│   ├── repositories/ # SQL implementations of repository traits
│   ├── client/       # HTTP client for CLI
│   └── database.rs   # Database pool abstraction
│
├── application/      # HTTP server, routes, middleware
│   ├── routes/       # Axum route handlers
│   └── errors.rs     # HTTP error mapping
│
└── presentation/     # User interfaces
    ├── cli/          # CLI commands and argument parsing
    └── web/          # View models for templates

Dependency flow: presentation → application → domain ← infrastructure

Code Patterns

Repository Pattern

All data access goes through trait-based repositories defined in domain/repositories.rs:

#[async_trait]
pub trait RoasterRepository {
    async fn insert(&self, roaster: NewRoaster) -> Result<Roaster, RepositoryError>;
    async fn get(&self, id: RoasterId) -> Result<Roaster, RepositoryError>;
    // ...
}

SQL implementations live in infrastructure/repositories/.

Typed IDs

Use the typed ID wrappers from domain/ids.rs to prevent mixing up IDs:

// Good
fn get_roast(&self, id: RoastId) -> Result<Roast, RepositoryError>

// Bad - raw i64 could be any ID type
fn get_roast(&self, id: i64) -> Result<Roast, RepositoryError>

SQL Query Construction

Use QueryBuilder for dynamic queries. For UPDATE queries, use the push_update_field! macro:

use super::macros::push_update_field;

let mut builder = QueryBuilder::new("UPDATE roasters SET ");
let mut sep = false;

push_update_field!(builder, sep, "name", changes.name);
push_update_field!(builder, sep, "country", changes.country);
// ... more fields

if !sep {
    return Err(RepositoryError::unexpected("No fields provided for update"));
}

builder.push(" WHERE id = ");
builder.push_bind(i64::from(id));

Sorting/Ordering

Each repository has an order_clause() method for consistent sort query generation:

fn order_clause(request: &ListRequest<RoasterSortKey>) -> String {
    let dir_sql = match request.sort_direction() {
        SortDirection::Asc => "ASC",
        SortDirection::Desc => "DESC",
    };
    match request.sort_key() {
        RoasterSortKey::Name => format!("LOWER(name) {dir_sql}, created_at DESC"),
        // ...
    }
}

CLI Commands

For simple get/delete commands, use the macros in presentation/cli/macros.rs:

use super::macros::{define_get_command, define_delete_command};

define_get_command!(GetRoasterCommand, get_roaster, RoasterId, roasters);
define_delete_command!(DeleteRoasterCommand, delete_roaster, RoasterId, roasters, "roaster");

Datastar Integration

The web UI uses Datastar for reactive updates without full page reloads. This provides HTMX-style interactions with a declarative API.

Request Detection

Datastar requests are identified by the datastar-request: true header:

// application/routes/support.rs
pub fn is_datastar_request(headers: &HeaderMap) -> bool {
    headers
        .get("datastar-request")
        .and_then(|value| value.to_str().ok())
        .map(|value| value.eq_ignore_ascii_case("true"))
        .unwrap_or(false)
}

Fragment Rendering

When a Datastar request is detected, return a fragment instead of a full page:

pub(crate) async fn roasters_page(...) -> Result<Response, StatusCode> {
    let request = query.into_request::<RoasterSortKey>();

    if is_datastar_request(&headers) {
        // Datastar request → return fragment only
        return render_roaster_list_fragment(state, request, is_authenticated).await;
    }

    // Traditional request → return full page with layout
    let template = RoastersTemplate { ... };
    render_html(template).map(IntoResponse::into_response)
}

Fragments are rendered with special headers that tell Datastar where to patch the DOM:

// application/routes/support.rs
pub fn render_fragment<T: Template>(template: T, selector: &'static str) -> Result<Response, AppError> {
    let html = render_template(template)?;
    let mut response = Html(html).into_response();
    response.headers_mut().insert("datastar-selector", HeaderValue::from_static(selector));
    response.headers_mut().insert("datastar-mode", HeaderValue::from_static("replace"));
    Ok(response)
}

Frontend Attributes

Templates use Datastar attributes for interactivity:

<!-- Reactive state -->
<section data-signals:show-form="false" data-signals:is-submitting="false">

  <!-- Visibility binding -->
  <div data-show="$showForm" style="display: none">
    <!-- Form content -->
  </div>

  <!-- Event handlers with HTTP actions -->
  <form data-on:submit="@post('/api/v1/roasters', {
    contentType: 'form',
    responseOverrides: {selector: '#roaster-list', mode: 'replace'}
  })">
    <!-- Form fields -->
  </form>

  <!-- Reset form on completion -->
  <form data-ref="form"
        data-on:datastar-fetch="evt.detail.type === 'finished' && ($showForm = false, $form.reset())">
</section>

Key attributes:

• data-signals:name="value" - Reactive state signals
• data-show="$signal" - Conditional visibility
• data-on:event="expression" - Event handlers
• data-ref="name" - DOM element references
• @get/@post/@put/@delete(url, options) - HTTP actions with automatic Datastar headers

URL Generation

ListNavigator generates URLs for pagination and sorting:

// presentation/web/views.rs
navigator.page_href(2)          // "/roasters?page=2&..." (full page)
navigator.fragment_page_href(2) // "/roasters?page=2&...#roaster-list" (fragment)
navigator.sort_href(key)        // "/roasters?sort=name&dir=..."

Flexible Payload Handling

Handlers accept both JSON and form data via FlexiblePayload<T>:

pub(crate) async fn create_roaster(
    payload: FlexiblePayload<NewRoaster>,
) -> Result<Response, ApiError> {
    let (new_roaster, source) = payload.into_parts();

    if is_datastar_request(&headers) {
        render_fragment(state, request, true).await  // Return updated fragment
    } else if matches!(source, PayloadSource::Form) {
        Ok(Redirect::to(&target).into_response())    // Traditional form redirect
    } else {
        Ok((StatusCode::CREATED, Json(roaster)).into_response())  // JSON API
    }
}

Route Handler Macros

For simple get/delete API handlers, use the macros in application/routes/macros.rs:

use super::macros::{define_get_handler, define_delete_handler};

// GET /api/v1/roasters/:id → returns JSON
define_get_handler!(get_roaster, RoasterId, Roaster, roaster_repo);

// DELETE /api/v1/roasters/:id → returns fragment for Datastar or 204 for API
define_delete_handler!(
    delete_roaster,
    RoasterId,
    RoasterSortKey,
    roaster_repo,
    render_roaster_list_fragment
);

Error Handling

• Domain errors: RepositoryError in domain/errors.rs
• HTTP errors: AppError in application/errors.rs with proper status code mapping
• CLI errors: Use anyhow::Result for simplicity

Domain Conversion

Records from the database should have an into_domain() method or equivalent:

impl BagRecord {
    fn into_domain(self) -> Bag { ... }
}

Conventions

1. Method naming: Use order_clause() for sort query builders (not sort_clause)
2. Imports: Group by super::, then crate::, with macros imported explicitly
3. SQL strings: Use raw strings r#"..."# for multi-line queries
4. Tests: Integration tests in tests/cli/ and tests/server/
5. Commits: Use Conventional Commit format (feat:, fix:, refactor:, etc.)

Communication Style

• Be direct and factual
• Analyse root causes before proposing solutions
• Prefer simple solutions over complex ones
• When proposing changes, explain the trade-offs