# `simple.py` — Site Reachability Checker

## What it does

Reads a plain-text list of URLs, issues an HTTP GET to each one, and reports
whether the site responded and how long it took (full wall-clock time including
body download). This is the simplest possible latency check — one line of
output per site, nothing more.

## Flags / arguments

```
python simple.py [sites.txt]
```

| Argument | Default | Meaning |
|----------|---------|---------|
| `sites.txt` | `sites.txt` in the current directory | Path to the plain-text config file |

**Config file format:**
- One URL per line.
- Lines starting with `#` are comments and are ignored.
- Blank lines are ignored.
- Future `key=value` tokens after the URL (e.g. `https://x.com  budget=200ms`)
  are silently ignored, so the file format is forward-compatible.

**Exit codes:**

| Code | Meaning |
|------|---------|
| 0 | All sites responded |
| 1 | One or more sites failed, or a usage/config error |

## Example

**Config (`sites.txt`):**
```
https://example.com
https://www.google.com
# https://httpbin.org/get   # uncomment to include
```

**Run:**
```sh
python simple.py sites.txt
```

**Expected output (latencies vary):**
```
OK        147.11 ms  https://example.com
OK         83.42 ms  https://www.google.com
```

**With an unreachable host:**
```
OK        147.11 ms  https://example.com
FAIL   (nodename nor servname provided, or not known)  https://nonexistent.invalid
```
Exit code: `1`

## Example config files

`python/configs/` contains purpose-built config files targeting every distinct
failure class (DNS, connection-refused, timeout, TLS-cert errors, HTTP 4xx/5xx,
and a mixed scenario). Each file includes a comment explaining what it exercises.

See [`python/configs/usage-simple.md`](../../python/configs/usage-simple.md) for the runnable
shell commands and expected output for each file.

## Limitations

- Measures total wall-clock time (DNS + TCP + TLS + server + transfer) as a
  single number. Use `phases.py` for a per-phase breakdown.
- Always uses GET; no auth, no custom headers, no redirect control.
- Timeout is hard-coded at 10 s. Use `phases.py` or `latprobe/` for a `--timeout`
  flag.
- HTTP error statuses (4xx, 5xx) are reported as `FAIL` — `urllib.request.urlopen`
  raises `HTTPError` for non-2xx responses, so a 404 is treated as a failure,
  not a success.