# AvParser image test service

A tiny, dependency-free web service that serves a deterministic image for any id matching a
configured pattern. It exists as a **target** for the app's pattern sources: point a source at one of
its endpoints and let the collector generate ids.

Each valid id returns a unique identicon PNG (derived from `SHA-256(id)`), so fetching the same id
twice yields the same bytes — which is what makes the collector's duplicate detection observable.

## Endpoints

Endpoints are declared in [`appsettings.json`](appsettings.json) under `ImgTest:Endpoints`. The
defaults:

| Path            | Id length | Characters        | Extension |
| --------------- | --------- | ----------------- | --------- |
| `/test1/{id}`   | 6–8       | letters + digits  | `.jpg`    |
| `/test2/{id}`   | 8–12      | digits only       | none      |
| `/test3/{id}`   | 8         | hex (`0-9a-f`)    | `.png`    |

Anything not matching a pattern (`/test1/xx`, `/test2/abcd1234`) returns `404`. `GET /` lists the
endpoints; `GET /healthz` returns `ok`.

Example: `GET /test1/2dfhyuj.jpg` → `200 image/png`.

### Adding an endpoint

Add an object to `ImgTest:Endpoints`:

```json
{ "Path": "test4", "MinLength": 4, "MaxLength": 6, "Alphabet": "Custom", "Chars": "abcdef012", "Extensions": [".png"] }
```

`Alphabet` is one of `LettersLower`, `LettersUpper`, `Letters`, `Digits`, `Alphanumeric`, `HexLower`,
or `Custom` (which uses `Chars`).

## Miss rate

Set `ImgTest:MissRate` (0..1) to make a deterministic fraction of otherwise-valid ids answer `404`,
emulating a site where most guessed ids do not exist. It is stable per id, so a run is repeatable.
Override at deploy time with the `ImgTest__MissRate` environment variable.

## Run

```bash
docker compose up --build
```

The container listens on `http://localhost:8080`. It speaks plain HTTP — **TLS for a public domain
such as `https://imgtest.example` is terminated by your own reverse proxy**, which forwards to this
container. A Caddy example:

```
imgtest.example {
    reverse_proxy localhost:8080
}
```

Or run it directly without Docker:

```bash
dotnet run
```

> This service is intentionally **not** part of `AvParser.slnx` and is not built by `./build.ps1`.
> It is a standalone support tool with its own Docker context.