# ZAP Framework Guide

This document explains the internal architecture of ZapMachine and provides step‑by‑step instructions for extending it with new handlers, templates, and interactive elements.

## Architecture Overview

### Front-Controller Routing (`?mode=X` → `ZAPController` → `ZAP{Mode}`)

All HTTP requests enter through `www/index.php`. The front controller reads the `mode` query parameter and dispatches to a class whose name is formed as `ZAP` + the ucfirst'd mode value.

```php
// www/index.php (simplified)
$mode = isset($_GET['mode']) ? $_GET['mode'] : 'home';
require_once '..' . DIRECTORY_SEPARATOR . 'conf' . DIRECTORY_SEPARATOR . 'init.php';
$config = Config::getInstance();
$config->register('engines', $search_engines);
$frontcontroller = new ZAPController($mode);
$output = $frontcontroller->fetch();
print($output);
```

`ZAPController` (in `lib/ZAPController.class.php`) constructs the class name from a prefix (`ZAP`) and the mode, verifies it exists via the autoloader, instantiates it, and calls `getContent()`:

```php
class ZAPController {
    private $prefix = 'ZAP';

    public function __construct($mode = 'home') {
        $mode = trim(strip_tags($mode));
        $this->mode = ucfirst($mode);
        $clazz = $this->prefix . $this->mode;
        if (!class_exists($clazz)) {
            die('Wrong parameter');
        }
        $this->action = new $clazz();
    }

    public function fetch() {
        return $this->action->getContent();
    }
}
```

**Registered modes and their handlers:**

| `?mode=` | Class | Template | Purpose |
|----------|-------|----------|---------|
| `home` (default) | `ZAPHome` | `tpl/index.tpl` | Word-input form |
| `display` | `ZAPDisplay` | `tpl/display.tpl` | Collage-generation progress screen |
| `zap` | `ZAPZap` | *(raw image output)* | Downloads images & processes collages, returns image blobs |

---

### Autoloader

`conf/init.php` registers an `spl_autoload_register` callback that searches every directory on the include path for both `{ClassName}.class.php` and `{ClassName}.interface.php`:

```php
spl_autoload_register(function ($class_name) {
    $include_path_tokens = explode(PATH_SEPARATOR, get_include_path());
    foreach ($include_path_tokens as $prefix) {
        $path[0] = $prefix . DIRECTORY_SEPARATOR . $class_name . '.interface.php';
        $path[1] = $prefix . DIRECTORY_SEPARATOR . $class_name . '.class.php';
        foreach ($path as $thisPath) {
            if (file_exists($thisPath)) {
                require_once $thisPath;
                return;
            }
        }
    }
});
```

The include path is built from these directories (relative to the project root):

| Constant | Directory |
|----------|-----------|
| `ZAP_RESOURCE_DIR` | `resource/` — search-engine implementations |
| `ZAP_UTILS_DIR` | `utils/` — utility classes (Session, ZAPCurl, Log) |
| `ZAP_SESSIONS_DIR` | `sessions/` |
| `ZAP_LIB_DIR` | `lib/` — core handlers and image processing |
| `ZAP_TPL_DIR` | `tpl/` — templates |
| `ZAP_CONF_DIR` | `conf/` — configuration |

This means any `.class.php` or `.interface.php` file placed in one of those directories is automatically found — no manual `require_once` calls needed for library classes.

---

### Config Singleton

Configuration values that must be accessible from any class are managed through `Config` (`conf/Config.class.php`), a classic singleton:

```php
$config = Config::getInstance();
$config->register('engines', $search_engines);    // store
$engines = $config->retrieve('engines');           // retrieve — returns false if not found
```

The singleton is wired in `www/index.php` immediately after `init.php` is loaded.

---

### Session Management

The `Session` class (`utils/Session.class.php`) wraps PHP's native sessions:

```php
Session::start('ZAP');                    // Begin session (sessions named 'ZAP')
Session::reset();                         // Clear $_SESSION array
Session::deleteCookie();                  // Remove client-side session cookie
Session::destroy();                       // Reset + delete cookie + session_destroy()
```

Session data is stored verbatim in `$_SESSION` and uses these keys:

| Key | Type | Set by | Purpose |
|-----|------|--------|---------|
| `words` | `string[]` | `ZAPDisplay` | Keyword list for image search |
| `folder` | `string` | `ZAPDisplay` | Absolute path to session folder |
| `collages` | `int` | `ZAPDisplay` | Number of collages to generate |
| `width` | `int` | `ZAPDisplay` | Collage width in pixels |
| `height` | `int` | `ZAPDisplay` | Collage height in pixels |
| `images` | `string[]` | `ZAPZap` | Queue of source image paths for current collage |
| `imgOriginal` | `string[]` | `ZAPZap` | Immutable copy of the original image list |
| `collageNr` | `int` | `ZAPZap` | Current collage sequence number |

**CLI note:** Session is only started automatically in web mode. See [CLI Bootstrap](#cli-bootstrap) below.

---

### Plugin-Based Search Engines

Search engines implement the `Search` interface (`resource/Search.interface.php`):

```php
interface Search {
    public function setQuery($word);
    public function setParam($key, $value);
    public function getData();
}
```

Each engine class lives in `resource/` and returns data in a universal array format:

```php
$data['result'] = true;                    // Boolean: success / failure
$data['engine'] = __CLASS__;               // Engine name, e.g. 'Brave'
$data['results'][0]['clickurl'] = '...';   // Image URL to download
$data['results'][0]['referer'] = '...';    // Source page URL
$data['results'][0]['thumb'] = '...';      // Thumbnail URL
```

Available engines are registered as an array of names in `conf/conf.php` and wired through the Config singleton at runtime. `ImgSearch` randomly selects an engine from the registered list each time it runs:

```php
$config = Config::getInstance();
$engines = $config->retrieve('engines');
$this->engine = $engines[array_rand($engines)];
```

**Current engine:** `Brave` (`resource/Brave.class.php`) — uses the Brave Search API.

To add a new engine:
1. Create `resource/YourEngine.class.php` implementing `Search`.
2. Add `'yourengine'` to the `$search_engines` array in `conf/conf.php`.

---

### Image Processing Pipeline

The image pipeline runs entirely server-side through three classes in `lib/`:

1. **`ImgSearch`** (`lib/ImgSearch.class.php`) — searches for an image URL via a registered engine, downloads the file, validates its MIME type (`image/jpeg`, `image/gif`, `image/png`), and saves it to the session folder.

2. **`ImgProcess`** (`lib/ImgProcess.class.php`) — constructs collages using ImageMagick. Each collage starts with `createBasicCanvas()` (zoom-crops the first source image) then layers additional images via `addToCanvas()` (random transparency + composite).

3. **`ImgIOTools`** (`lib/ImgIOTools.class.php`) — handles output: `onScreen()` streams an Imagick object as an HTTP image response; `urlOnScreen()` loads a file path first; `saveImg()` writes to disk.

4. **`ImgTools`** (`lib/ImgTools.class.php`) — utility functions: `zoomCrop()`, `transparantRandom()`, `randomRotate()`, `resize()`, `recolor()`, `convertGifsToPng()`.

---

### CLI Bootstrap

CLI scripts (in `cli_scripts/`) bootstrap the application differently from web requests. Because `init.php` skips `Session::start()` when `php_sapi_name() === 'cli'`, CLI scripts must handle sessions manually if needed.

**Example — `cli_scripts/test.php`:**

```php
#!/usr/bin/env php
<?php
// Make sure relative paths in init.php resolve against this script's directory
chdir(__DIR__);

// Bootstrap the application (autoloader, constants, Config, but NOT session)
require_once __DIR__ . '/../conf/init.php';

// If you need sessions in CLI, call Session::start() manually:
// Session::start('ZAP');

// Now all classes, the autoloader, and Config singleton are available
$config = Config::getInstance();
$config->register('engines', $search_engines);
```

Key differences from the web entry point:
- `chdir(__DIR__)` is **required** before `require_once 'init.php'` because `init.php` uses `realpath('.')` to define `ZAP_APP_BASE_DIR`.
- `Session::start()` is **not called** — the `init.php` condition `php_sapi_name() !== 'cli'` guards against it.
- You must explicitly register engines with `Config::getInstance()->register('engines', …)` because `www/index.php` normally does this.

---

### Logging

The `Log` class (`utils/Log.class.php`) writes timestamped messages to a session folder. It is used by `ImgSearch` (controlled by the `ZAP_LOG` constant in `conf/conf.php`). Each log call appends to both `log.txt` (plain text) and `log.xml` (XML-friendly) in the session's output directory.

```php
if (ZAP_LOG == true) {
    $log = new Log($this->folder);
    $log->addToLog('ok', 'Search: ', "downloaded to $imageName");
    $log->addToLog('error', 'Search: ', 'bad search data received');
}
```

---

## Template Rendering Pipeline

The template system is a minimal PHP-native pattern built around `ob_start()` / `include` / `extract()` / `ob_get_clean()`. There is no template engine — templates are plain PHP files that receive variables via the symbol table.

### How Templates Work

Every `ZAP{Mode}` handler follows the same rendering pattern:

```php
class ZAPHome {
    private $template = 'index';       // corresponds to tpl/index.tpl
    private $tpl = '';

    public function __construct() {
        $this->ver = ZAP_VERSION;
        extract(get_object_vars($this));      // ← makes all private properties available as $variables

        ob_start();                            // ← start output buffer
        include getZAPTemplate($this->template); // ← include the .tpl file
        $this->tpl .= ob_get_clean();          // ← capture buffer content, clean buffer
    }

    public function getContent() {
        return $this->tpl;
    }
}
```

**Step by step:**

1. Properties are set in the constructor (often from `$_POST`, `$_SESSION`, or constants like `ZAP_VERSION`).
2. `extract(get_object_vars($this))` promotes every private property to a local variable in the current symbol table. A property `$this->template = 'index'` becomes `$template = 'index'`.
3. `ob_start()` begins capturing all output.
4. `include getZAPTemplate($this->template)` includes the file `tpl/{name}.tpl`. The included file inherits the current symbol table, so it can use `$ver`, `$folder`, `$words`, etc. directly.
5. `ob_get_clean()` retrieves the captured HTML and closes the buffer.
6. `getContent()` returns the accumulated output string, which `ZAPController::fetch()` returns to `index.php` for `print()`.

### The `getZAPTemplate()` Helper

```php
function getZAPTemplate($tplname) {
    $tplfile = $tplname . '.tpl';
    $tplfilepath = ZAP_APP_BASE_DIR . DIRECTORY_SEPARATOR
                 . ZAP_TPL_DIR . DIRECTORY_SEPARATOR . $tplfile;
    if (file_exists($tplfilepath)) {
        return $tplfilepath;
    } else {
        return ERROR_PREFIX . 'No template';
    }
}
```

All templates live in the `tpl/` directory and have the `.tpl` extension. The helper resolves the absolute path so the `include` call works from any working directory.

### Adding a New Template

To add a new page/view:

1. **Create the `ZAP{Mode}` handler** in `lib/`. The class must be named `ZAP{Mode}` (case-sensitive, PascalCase after the prefix) and must implement a `getContent()` method that returns a string:

   ```php
   <?php
   // lib/ZAPExample.class.php
   class ZAPExample {
       private $template = 'example';
       private $tpl = '';

       public function __construct() {
           $this->pageTitle = 'My Example Page';
           extract(get_object_vars($this));

           ob_start();
           include getZAPTemplate($this->template);
           $this->tpl .= ob_get_clean();
       }

       public function getContent() {
           return $this->tpl;
       }
   }
   ```

2. **Create the template** at `tpl/example.tpl`:

   ```php
   <!DOCTYPE html>
   <html lang="en">
   <head><title>Example — <?php echo $pageTitle; ?></title></head>
   <body>
       <h1><?php echo $pageTitle; ?></h1>
       <p>ZAP version <?php echo $ver; ?></p>
   </body>
   </html>
   ```

3. **Use the route:** Navigate to `index.php?mode=example`. The autoloader finds `ZAPExample` in `lib/`, the front controller instantiates it, and `getZAPTemplate()` loads `tpl/example.tpl`.

No registration step is required — the front controller's naming convention (`ZAP` + ucfirst(mode)) and the autoloader handle discovery automatically.

---

## Adding Interactive Elements

This section documents the two interactive-element patterns used in the application. Each pattern pairs a server-side template with a client-side JavaScript file.

### Pattern 1: Form with Client-Side Validation (`index.tpl` + `js/main.js`)

Used by `ZAPHome` to collect word inputs, validate them in the browser, and POST to the `display` mode.

**Server side (`ZAPHome` in `lib/ZAPHome.class.php`):**

The handler passes two template variables into `tpl/index.tpl`:
- `$ver` — the ZAP version string.
- `$status` — an optional status message from the query string (`?stat=...`).

The template renders a `<form id="form1">` that POSTs to `index.php?mode=display`. Each input is named `word01`, `word02`, … `word{MAX_WORDS}` (zeropadded to two digits). A `<select name="collages">` controls the number of collages, and width/height text inputs control dimensions.

**Client side (`js/main.js`):**

The `form1Submit()` function performs validation before the form is submitted:

```javascript
function form1Submit() {
    // Minimum of two words required
    var word1 = document.getElementById('word01').value;
    var word2 = document.getElementById('word02').value;
    var width = document.getElementById('width').value;
    var height = document.getElementById('height').value;

    if (word1.length <= 0) {
        document.getElementById('status').innerHTML = 'Minimum of two words required';
        return;
    }
    if (word2.length <= 0) {
        document.getElementById('status').innerHTML = 'Minimum of two words required';
        return;
    }
    if (width.length <= 0) {
        document.getElementById('status').innerHTML = 'Value <b>width</b> required';
        return;
    }
    if (height.length <= 0) {
        document.getElementById('status').innerHTML = 'Value <b>height</b> required';
        return;
    }
    if (!IsNumeric(width)) {
        document.getElementById('status').innerHTML = 'Value <b>width</b> needs numeric input';
        return;
    }
    if (!IsNumeric(height)) {
        document.getElementById('status').innerHTML = 'Value <b>height</b> needs numeric input';
        return;
    }

    // Hide form, show loading indicator, then submit
    document.getElementById('status').innerHTML = ' ';
    document.getElementById('loading').style.visibility = 'visible';
    document.getElementById('form1').style.visibility = 'hidden';
    document.getElementById('form1').submit();
}
```

**To reproduce this pattern in a new handler:**

1. Create a form in your `.tpl` that POSTs to `index.php?mode=yourmode`.
2. Create a `ZAPYourMode` handler in `lib/` that reads `$_POST` values in its constructor and stores them in `$_SESSION`.
3. Write a `js/your.js` file with a validation function, and include `<script src="js/your.js"></script>` in the template's `<head>`.
4. Use a `<div id="status">` element in the template to display validation errors.

---

### Pattern 2: Polling Image Display (`display.tpl` + `js/display.js`)

Used by the `display` and `zap` modes to show collage progress. The server streams individual image responses, and the client alternates between two `<img>` tags to give the appearance of continuous updating.

**Server side:**

`ZAPDisplay` (in `lib/ZAPDisplay.class.php`) sets session variables from `$_POST` and renders `tpl/display.tpl`. The template declares `onload="go(this,['img1','img2'],5000);"` on the `<body>` tag, which kicks off the polling loop.

`ZAPZap` (in `lib/ZAPZap.class.php`) handles each individual poll request. On each invocation it either:
- Downloads the next source image (if `$_SESSION['words']` is not empty) and streams it via `ImgIOTools::onScreen()`.
- Starts the next collage (if `$_SESSION['words']` is empty but `$_SESSION['collages'] > 0`).
- Adds the next source image to the current collage via `ImgProcess::addToCanvas()`.
- Signals completion by destroying the session and returning an error string (which triggers the `onerror` handler in JavaScript).

**Client side (`js/display.js`):**

```javascript
var go = function(b, img_id, interval) {
    var i = 0;
    var img0 = document.getElementById(img_id[0]);
    var img1 = document.getElementById(img_id[1]);
    var img = [img0, img1];
    var activeImage = 1; // index of visible image
    var url = 'index.php?mode=zap';

    if (isNaN(interval)) {
        interval = 5000;
    }

    // Trigger the next image fetch after the current one has loaded.
    img[0].onload = img[1].onload = function() {
        var inactiveImage = activeImage === 0 ? 1 : 0;
        img[activeImage].style.display = 'none';
        img[inactiveImage].style.display = '';
        activeImage = inactiveImage;

        setTimeout(function() {
            img[inactiveImage].src = url + '&i=' + (i++);
        }, interval);
    };

    // When the backend signals completion it returns a small HTML page.
    // Show the ready link and stop fetching new images.
    img[0].onerror = img[1].onerror = function() {
        document.getElementById('ready').innerHTML = '<a href="/">Ready</a>';
    };

    // Kick off the first request.
    img[activeImage].src = url + '&i=' + (i++);
};
```

**How the polling cadence works:**

1. `body onload="go(this,['img1','img2'],5000)"` starts the loop with a 5 s interval between successive fetches.
2. Two `<img>` tags (`#img1` and `#img2`) are used — one is visible, the other hidden.
3. When the visible image finishes loading (`img.onload`), the pair swaps: the loaded image is hidden, and the previously hidden one is shown. After a 5 s delay (`setTimeout`), the newly hidden image's `src` is set to `index.php?mode=zap&i={counter}`.
4. Each request to `mode=zap` returns raw image data (a `Content-Type: image/jpeg` response). The browser renders it into the `<img>` tag, triggering `onload` again and continuing the cycle.
5. When `ZAPZap` finishes all collages, it destroys the session and returns an HTML error string instead of image data. The `<img>` tag fails to load an image, triggering `onerror`, which replaces the image area with a "Ready" link.

**To reproduce this pattern in a new handler:**

1. Create a template with two `<img>` elements and `<body onload="go(this,['id1','id2'],intervalMs)">`.
2. Include `js/display.js` (or copy the pattern into your own JS file).
3. Create a `ZAP{Mode}` handler that returns raw image data (set `Content-Type` headers and use `echo` with `readfile()` or Imagick's `getImageBlob()`).
4. Signal completion by returning a non-image response that will trigger `onerror` on the `<img>` tag.

---

## Summary: Creating a New Feature End-to-End

To add a completely new feature to ZapMachine, follow these steps:

1. **Add configuration** in `conf/conf.php` (constants, engine names) if needed.
2. **Create the handler** `lib/ZAP{Mode}.class.php` with `getContent()` returning a string.
3. **Create the template** `tpl/{mode}.tpl` using the `ob_start`/`include`/`extract`/`ob_get_clean` pattern.
4. **Choose an interactive pattern:**
   - For form input with validation: add a form in the template, write a JS validation function, and include the script.
   - For polling/image updates: use the two-`<img>` swap with `onload`/`onerror`.
5. **Create a JS file** in `www/js/` and reference it from the template's `<head>`.
6. **Test the route** at `index.php?mode={ModeName}`.
7. **Test from CLI** using the bootstrap pattern in `cli_scripts/test.php` (remember `chdir(__DIR__)` + manual `Session::start()` if needed).