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ammocpr/CLAUDE.md

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CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

Project Overview

Ammoprices is a Phoenix 1.8 web application that scrapes ammunition prices from multiple online retailers, tracks price history, and displays analytics. Built with Elixir ~> 1.15, LiveView, Ecto/PostgreSQL, Tailwind CSS v4, and daisyUI.

Common Commands

mix setup                  # Install deps, create DB, run migrations, build assets
mix phx.server             # Start dev server (localhost:4000)
iex -S mix phx.server      # Start dev server with IEx shell
mix test                   # Run all tests (auto-creates/migrates test DB)
mix test test/path_test.exs          # Run a single test file
mix test test/path_test.exs:42       # Run a specific test by line number
mix test --failed                    # Re-run previously failed tests
mix precommit              # Compile (warnings-as-errors) + unlock unused deps + format + credo --strict + test
mix format                 # Format code
mix ecto.gen.migration name          # Generate a new migration
mix ecto.migrate           # Run pending migrations
mix ecto.reset             # Drop and recreate database

mix precommit is the required pre-commit check — always run it before finishing changes.

Architecture

Domain Contexts

Catalog (lib/ammoprices/catalog/) — Retailers, calibers, and products.

  • Retailer: name, slug (unique), base_url, enabled flag, last_scraped_at
  • Caliber: name, slug (unique), category (handgun/rifle/rimfire/shotgun), aliases array
  • Product: belongs_to retailer & caliber. Fields: title, url (unique per retailer), brand, grain_weight, round_count, casing (brass/steel/aluminum/alloy/composite), subsonic, in_stock. Upserted on (retailer_id, url) conflict

Prices (lib/ammoprices/prices/) — Immutable price snapshots and analytics.

  • PriceSnapshot: price_cents, price_per_round_cents, in_stock, recorded_at. Append-only (no updated_at)
  • Queries: latest prices per product (with filters), daily averages, price stats (min/max/avg), cheapest per caliber

Scraping Pipeline (lib/ammoprices/scraping/)

ScrapeJob (Oban, every 4h) → Runner → Scraper (per retailer) → HttpClient → Floki/JSON parse
                                    ↓
                              Upsert products → Create snapshots → PubSub broadcast
  • Scraper behaviour: Required callbacks retailer_slug/0, category_url/1, parse_products/1. Optional fetch/2 for custom HTTP (e.g., GraphQL)
  • Runner: Checks function_exported? for fetch/2 — uses it if available, otherwise standard HTTP GET + parse flow
  • HttpClient: Req-based with realistic Chrome headers, retries. Has get/1 and post_json/3
  • TextDetector: Regex detection of subsonic and casing type from product titles
  • CaliberMatcher: Matches products to calibers via name/alias lookup
  • ScrapeJob: Oban worker, queue :scraping (concurrency 2), 5-15 min random delay between requests in prod, 0 in test

Retailers (7 scrapers in lib/ammoprices/scraping/retailers/):

Retailer Type Notes
Lucky Gunner HTML (Floki) Slug-to-URL mapping per caliber
SG Ammo HTML (Floki) Standard HTML parsing
Target Sports USA HTML (Floki) Standard HTML parsing
True Shot Ammo JSON API (Shopify) /collections/{handle}/products.json, parse_products accepts decoded map
Palmetto State Armory HTML (Magento) data-price-amount attrs, brand = first word of title
Bulk Ammo HTML (Magento) a.product-name, brand via regex from title
Natchez GraphQL Uses fetch/2 callback, HttpClient.post_json/3, requires Store: default header

Web Layer

Routes:

  • GET / → HomeLive — Calibers grouped by category with cheapest CPR per caliber
  • GET /calibers/:slug → CaliberLive.Show — Price table, Chart.js chart, filter bar, stats

CaliberLive.Show filters: in_stock (toggle), casing (mutually exclusive), grain_weight (mutually exclusive), subsonic (toggle, only shown when subsonic products exist). Chart range: 7d/30d/90d/1y/all.

Real-time: PubSub on "prices:updated" topic. CaliberLive.Show subscribes on connect; broadcasts trigger reload of filter options, product stream, chart, and stats.

Components:

  • PriceComponents: price_per_round/1 (formats cents as $0.38), stock_badge/1, retailer_link/1
  • CoreComponents: Standard Phoenix component library (daisyUI + Tailwind)

Assets

  • Tailwind CSS v4 — @import "tailwindcss" syntax in app.css, no tailwind.config.js
  • daisyUI — Custom light/dark themes defined in app.css
  • Chart.js — Vendored in assets/vendor/chart.js, used via colocated .PriceChart hook
  • esbuild — Bundles app.js only. @ alias maps to assets/vendor/ for imports
  • Colocated hook imports must use @/vendor/... alias, NOT relative paths (hooks compile to _build/)

Database

  • Binary UUIDs, UTC timestamps throughout
  • Products use on_conflict: {:replace, [fields...]} for upserts on (retailer_id, url)
  • Product filter indexes: (caliber_id, in_stock), (caliber_id, casing), (caliber_id, grain_weight), (caliber_id, subsonic)
  • Retailers and calibers seeded via database migration (not seeds.exs)

Test Infrastructure

  • Fixtures: test/support/fixtures.ex — factory functions (retailer_fixture, caliber_fixture, product_fixture, snapshot_fixture)
  • HTML/JSON fixtures: test/fixtures/{retailer_name}/ — scraped response samples for each retailer
  • HTTP stubbing: Req.Test with plug config in test.exs
  • Oban: :manual mode in test (jobs don't auto-run)
  • Scrape delay: {0, 0} in test config

Key Conventions

  • HTTP client: Use Req (already included). Never use HTTPoison, Tesla, or :httpc
  • Prices: Display in dollar format ($0.38/rd), stored as integer cents internally
  • LiveView templates: Always begin with <Layouts.app flash={@flash}> wrapper
  • Collections: Always use LiveView streams, never assign raw lists
  • Icons: Use <.icon name="hero-x-mark" /> component, never Heroicons modules
  • Forms: Always use to_form/2 assigned in LiveView, access via @form[:field] in templates
  • JS in templates: Use colocated hook <script :type={Phoenix.LiveView.ColocatedHook}> with . prefixed names, never raw <script> tags
  • No inline scripts: Import vendor deps into app.js/app.css, no external src/href in layouts
  • Tailwind classes: Use list syntax class={["base", condition && "extra"]} for conditional classes
  • Never use @apply in CSS