Analyze a file format of a song.

## Spec

File: ./Test.pro (file ext are always .pro)

- every song contains parts (name group here) (here: Verse 1, Verse 2, Chorus, ...) but could be any name
- every group contains 1-x slides
- every song contains different arrangements (here normal and test2) that defines the existence and the order of the groups
- every slide CAN have another textbox which contains a translated version of the first textbox

## Status

1. [x] Analyse the file structure and find all of the described specs.
2. [x] Test and verify if the definition is correct - there is a `all-songs` directory with lot of examples.
3. [x] Describe the structure for future AI prompts to use these files in `spec/pp_song_spec.md` and describe the usage in the `AGENTS.md` (replace obsolete commands)
4. [x] Write a PHP module (is later used in laravel) in `./php` which can parse a song and let get/set every aspect of structure. Use Objects here (Song, Group, Slide, Arrangement, etc)
5. [x] Create a simple PHP cli tool, which receive a param with a song file and show the structure of the song.

## PHP Module Usage

The ProPresenter song parser is available as a PHP module in `./php`. Use it to read, parse, and modify .pro song files.

### Reading a Song

```php
use ProPresenter\Parser\ProFileReader;
use ProPresenter\Parser\ProFileWriter;

$song = ProFileReader::read('path/to/song.pro');
```

### Accessing Song Structure

```php
// Basic song info
echo $song->getName();        // Song name
echo $song->getUuid();        // Song UUID

// Groups (song parts like Verse 1, Chorus, etc.)
foreach ($song->getGroups() as $group) {
    echo $group->getName();   // "Verse 1", "Chorus", etc.
    $slides = $song->getSlidesForGroup($group);
    foreach ($slides as $slide) {
        echo $slide->getPlainText();
        if ($slide->hasTranslation()) {
            echo $slide->getTranslation()->getPlainText();
        }
    }
}

// Arrangements (different song orderings)
foreach ($song->getArrangements() as $arr) {
    $groups = $song->getGroupsForArrangement($arr);
    // Groups in arrangement order
}
```

### Modifying and Writing

```php
$song->setName("New Name");
ProFileWriter::write($song, 'output.pro');
```

## CLI Tool

Parse and display song structure from the command line:

```bash
php php/bin/parse-song.php path/to/song.pro
```

## Format Specification

For detailed information about the .pro file format, see `spec/pp_song_spec.md`.

## Key Files

- `php/src/Song.php` — Top-level song wrapper
- `php/src/Group.php` — Group (song part) wrapper
- `php/src/Slide.php` — Slide wrapper with text access
- `php/src/TextElement.php` — Text element with label + plain text
- `php/src/Arrangement.php` — Arrangement wrapper
- `php/src/RtfExtractor.php` — RTF to plain text converter
- `php/src/ProFileReader.php` — Reads .pro files
- `php/src/ProFileWriter.php` — Writes .pro files
- `php/bin/parse-song.php` — CLI tool
- `spec/pp_song_spec.md` — Format specification