costco-watch: ntfy alert when a Costco tire is back in stock

apps/costco-watch/build/README.md

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+# costco-watch image
+
+Dependency-free Node service (node:22-alpine + curl for the healthcheck).
+Source: https://git.alexzaw.dev/alexz/costco-watch (working copy:
+~/projects/costco-watch). Build + push with ./build.sh.
+
+Gotchas:
+- TARGET_URL must go through the costco-tire cloudflared proxy AND that
+  hostname needs a Cloudflare Transform Rule adding browser headers
+  (User-Agent, Accept, Accept-Language, Sec-Fetch-*). Without it Costco stalls
+  the request until timeout and the checker reports "error"/"blocked".
+- State (last stock value, transition history) lives in ${APP_DATA_DIR}/data;
+  wiping it means the next check can re-alert.

apps/costco-watch/build/build.sh

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+#!/bin/bash
+set -euo pipefail
+IMAGE_NAME="${IMAGE_NAME:-git.alexzaw.dev/alexz/costco-watch}"
+IMAGE_TAG="${IMAGE_TAG:-latest}"
+SRC="${SRC:-$HOME/projects/costco-watch}"
+docker build "$@" -t "${IMAGE_NAME}:${IMAGE_TAG}" "$SRC"
+docker push "${IMAGE_NAME}:${IMAGE_TAG}"

apps/costco-watch/config.json

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+{
+  "$schema": "../app-info-schema.json",
+  "name": "Costco Stock Watch",
+  "id": "costco-watch",
+  "available": true,
+  "port": 8592,
+  "exposable": false,
+  "dynamic_config": true,
+  "no_gui": true,
+  "tipi_version": 1,
+  "version": "1.0.0",
+  "categories": [
+    "automation",
+    "utilities"
+  ],
+  "description": "Polls a Costco tire product page on an interval and pushes an ntfy alert the moment it flips from out-of-stock to in-stock. Points at the costco-tire cloudflared proxy, which needs a Cloudflare Transform Rule attaching browser-like request headers - Costco stalls non-browser header sets.",
+  "short_desc": "Alerts when a Costco tire is back in stock",
+  "author": "alexz",
+  "source": "https://git.alexzaw.dev/alexz/costco-watch",
+  "form_fields": [
+    {
+      "type": "text",
+      "label": "Product URL",
+      "env_variable": "TARGET_URL",
+      "required": true,
+      "default": "https://costco-tire.alexzaw.dev/SearchResultsByItemOrPart?ItemNo=1273727",
+      "hint": "Full product page URL to watch, via the costco-tire proxy"
+    },
+    {
+      "type": "text",
+      "label": "Item Label",
+      "env_variable": "ITEM_LABEL",
+      "required": false,
+      "default": "Michelin Primacy Tour A/S 235/45R18",
+      "hint": "Friendly name used in the notification text"
+    },
+    {
+      "type": "text",
+      "label": "ntfy Topic",
+      "env_variable": "NTFY_TOPIC",
+      "required": true,
+      "hint": "Topic to publish to, e.g. costco-tire. Subscribe to it in the ntfy app."
+    },
+    {
+      "type": "text",
+      "label": "ntfy URL",
+      "env_variable": "NTFY_URL",
+      "required": false,
+      "default": "https://ntfy.alexzaw.dev",
+      "hint": "ntfy server base URL"
+    },
+    {
+      "type": "password",
+      "label": "ntfy Token",
+      "env_variable": "NTFY_TOKEN",
+      "required": false,
+      "hint": "Only needed if the topic requires auth. Leave blank for an open topic."
+    },
+    {
+      "type": "text",
+      "label": "Check Interval (minutes)",
+      "env_variable": "INTERVAL_MINUTES",
+      "required": false,
+      "default": "60",
+      "hint": "Keep at 60 or more - this is a courtesy check, not a scraper"
+    },
+    {
+      "type": "random",
+      "label": "API Key",
+      "env_variable": "API_KEY",
+      "required": true,
+      "min": 24,
+      "encoding": "hex",
+      "hint": "Guards /status and /check. Auto-generated."
+    }
+  ],
+  "supported_architectures": [
+    "amd64"
+  ],
+  "created_at": 1754995000000,
+  "updated_at": 1754995000000,
+  "deprecated": false,
+  "min_tipi_version": "4.5.0"
+}

apps/costco-watch/docker-compose.json

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+{
+  "schemaVersion": 2,
+  "$schema": "https://schemas.runtipi.io/dynamic-compose.json",
+  "services": [
+    {
+      "name": "costco-watch",
+      "image": "git.alexzaw.dev/alexz/costco-watch:latest",
+      "isMain": true,
+      "internalPort": 8080,
+      "environment": [
+        { "key": "PORT", "value": "8080" },
+        { "key": "DATA_DIR", "value": "/data" },
+        { "key": "TARGET_URL", "value": "${TARGET_URL}" },
+        { "key": "ITEM_LABEL", "value": "${ITEM_LABEL:-Costco item}" },
+        { "key": "NTFY_URL", "value": "${NTFY_URL:-https://ntfy.alexzaw.dev}" },
+        { "key": "NTFY_TOPIC", "value": "${NTFY_TOPIC}" },
+        { "key": "NTFY_TOKEN", "value": "${NTFY_TOKEN:-}" },
+        { "key": "INTERVAL_MINUTES", "value": "${INTERVAL_MINUTES:-60}" },
+        { "key": "API_KEY", "value": "${API_KEY}" }
+      ],
+      "volumes": [
+        {
+          "hostPath": "${APP_DATA_DIR}/data",
+          "containerPath": "/data",
+          "readOnly": false
+        }
+      ],
+      "healthCheck": {
+        "test": "curl -f http://127.0.0.1:8080/health || exit 1",
+        "interval": "60s",
+        "timeout": "5s",
+        "retries": 3,
+        "startPeriod": "10s"
+      }
+    }
+  ]
+}

apps/costco-watch/metadata/description.md

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+# costco-watch
+
+Polls a Costco tire product page on an interval and pushes an ntfy alert when
+the item flips from out-of-stock to in-stock.
+
+## Why it points at a proxy, not costco.com
+
+Costco's bot mitigation silently stalls requests carrying a non-browser header
+set (the connection completes TLS, then nothing comes back - no 403, just a
+hang). The page loads fine through `costco-tire.alexzaw.dev`, a cloudflared
+ingress rule with `httpHostHeader: tires.costco.com`, **provided** a Cloudflare
+Transform Rule attaches browser-like request headers (`User-Agent`, `Accept`,
+`Accept-Language`, `Sec-Fetch-*`, `Upgrade-Insecure-Requests`) for that
+hostname. cloudflared itself cannot add headers - its `originRequest` block has
+no such option - which is why the rule lives at the edge.
+
+If the checker starts reporting `blocked`, that Transform Rule is the first
+thing to verify.
+
+## Config
+
+| Env | Purpose |
+|-----|---------|
+| `TARGET_URL` | Product page to watch (required) |
+| `ITEM_LABEL` | Friendly name used in notifications |
+| `NTFY_URL` / `NTFY_TOPIC` | ntfy server and topic (topic required) |
+| `NTFY_TOKEN` | Bearer token, if the topic is protected |
+| `INTERVAL_MINUTES` | Poll interval, default 60 |
+| `API_KEY` | Guards `/status` and `/check` |
+
+## Endpoints
+
+- `GET /health` - liveness
+- `GET /status` - current stock state, last check, transition history
+- `POST /check` - force a check now
+
+## Etiquette
+
+`tires.costco.com/robots.txt` allows `User-agent: *` on all paths, so a personal
+low-frequency check is within its terms. Keep the interval at an hour or more.