solution by josef.sabl@gmail.com

reader/FileIterator.php

@@ -0,0 +1,83 @@
+<?php
+
+namespace Reader;
+
+
+final class FileIterator implements \Iterator
+{
+
+	/** @var string */
+	private $filePath;
+
+	/** File handle */
+	private $f;
+
+	/** @var string */
+	private $current;
+
+	/** @var int */
+	private $key = -1;
+
+
+	public function __construct(string $filePath)
+	{
+		$this->filePath = $filePath;
+	}
+
+
+	public function __destruct()
+	{
+		if ($this->f) {
+			fclose($this->f);
+		}
+	}
+
+
+	public function current()
+	{
+		return $this->current;
+	}
+
+
+	public function key()
+	{
+		return $this->key;
+	}
+
+
+	public function next()
+	{
+		$this->current = trim(fgets($this->f), PHP_EOL);
+		$this->key++;
+	}
+
+
+	public function rewind()
+	{
+		$this->openFile();
+	}
+
+
+	public function valid(): bool
+	{
+		return !feof($this->getFileHandle());
+	}
+
+
+	private function getFileHandle()
+	{
+		return $this->f ?? $this->openFile();
+	}
+
+
+	private function openFile()
+	{
+		if ($this->f) {
+			fclose($this->f);
+		}
+		$this->f = fopen($this->filePath, 'r');
+		$this->key = -1;
+		$this->next();
+		return $this->f;
+	}
+}

reader/Filter.php

@@ -0,0 +1,69 @@
+<?php
+
+namespace Reader;
+
+
+abstract class Filter implements \Iterator
+{
+
+	/** @var \Iterator */
+	protected $delegate;
+
+	/** @var int */
+	private $key = 0;
+
+	/** @var array */
+	private $buffer = [];
+
+
+	public function __construct(\Iterator $delegate)
+	{
+		$this->delegate = $delegate;
+	}
+
+
+	abstract function bufferCurrent(): array;
+
+
+	public function current()
+	{
+		if (empty($this->buffer)) {
+			$this->buffer = $this->bufferCurrent();
+		}
+		return $this->buffer[0];
+	}
+
+
+	public function key()
+	{
+		return $this->key;
+	}
+
+
+	public function next()
+	{
+		array_shift($this->buffer);
+		$this->key++;
+		if (empty($this->buffer)) {
+			$this->delegate->next();
+		}
+	}
+
+
+	public function rewind()
+	{
+		$this->key = 0;
+		$this->buffer = [];
+		$this->delegate->rewind();
+	}
+
+
+	public function valid(): bool
+	{
+		if (empty($this->buffer)) {
+			return $this->delegate->valid();
+		} else {
+			return TRUE;
+		}
+	}
+}

reader/Filter/MinLengthJoiner.php

@@ -0,0 +1,25 @@
+<?php
+
+namespace Reader\Filter;
+
+
+final class MinLengthJoiner extends \Reader\Filter
+{
+
+	const MIN_LENGTH = 5;
+
+
+	public function bufferCurrent(): array
+	{
+		$current = $this->delegate->current();
+
+		while (strlen($current) < static::MIN_LENGTH && $this->delegate->valid()) {
+			$this->delegate->next();
+			if ($this->delegate->valid()) {
+				$current .= '|' . $this->delegate->current();
+			}
+		}
+
+		return [$current];
+	}
+}

reader/Filter/SemicolonSplitter.php

@@ -0,0 +1,15 @@
+<?php
+
+namespace Reader\Filter;
+
+
+final class SemicolonSplitter extends \Reader\Filter
+{
+
+
+	public function bufferCurrent(): array
+	{
+		$current = $this->delegate->current();
+		return explode(';', $current);
+	}
+}

reader/Filter/StopwordsOmitter.php

@@ -0,0 +1,37 @@
+<?php
+
+namespace Reader\Filter;
+
+
+final class StopwordsOmitter extends \Reader\Filter
+{
+
+	/** @var string */
+	private $stopword;
+
+
+	public function __construct(\Iterator $delegate, string $stopword)
+	{
+		parent::__construct($delegate);
+		$this->stopword = $stopword;
+	}
+
+
+	public function bufferCurrent(): array
+	{
+		return [$this->delegate->current()];
+	}
+
+
+	public function valid(): bool
+	{
+		if ($this->delegate->valid()) {
+			if (\strpos($this->delegate->current(), $this->stopword) !== FALSE) {
+				$this->delegate->next();
+				return $this->valid();
+			}
+			return TRUE;
+		}
+		return FALSE;
+	}
+}

reader/IPresenter.php

@@ -0,0 +1,11 @@
+<?php
+
+namespace Reader;
+
+
+interface IPresenter
+{
+
+
+	public function apply(string $inputLine): string;
+}

reader/Presenter/SimplePrinter.php

@@ -0,0 +1,14 @@
+<?php
+
+namespace Reader\Presenter;
+
+
+final class SimplePrinter implements \Reader\IPresenter
+{
+
+
+	public function apply(string $inputLine): string
+	{
+		return $inputLine;
+	}
+}

reader/Presenter/WordsCounter.php

@@ -0,0 +1,42 @@
+<?php
+
+namespace Reader\Presenter;
+
+
+final class WordsCounter implements \Reader\IPresenter
+{
+
+	/** @var array */
+	private $words = [];
+
+	/** @var counts */
+	private $counts = [];
+
+
+	public function __construct(array $words)
+	{
+		$this->words = $words;
+	}
+
+
+	public function apply(string $inputLine): string
+	{
+		foreach ($this->words as $word) {
+			if (strpos($inputLine, $word) !== FALSE) {
+				$this->counts[$word] = ($this->counts[$word] ?? 0) + 1;
+			}
+		}
+
+		return $this->output();
+	}
+
+
+	private function output(): string
+	{
+		$output = "----------------------------\n";
+		foreach ($this->counts as $word => $count) {
+			$output .= "$word\t$count\n";
+		}
+		return $output;
+	}
+}

reader/Processor.php

@@ -0,0 +1,35 @@
+<?php
+
+namespace Reader;
+
+
+final class Processor
+{
+
+	/** @var \Iterator */
+	private $inputStream;
+
+	/** @var Presenter */
+	private $presenter;
+
+
+	public function __construct(\Iterator $inputStream, IPresenter $presenter)
+	{
+		$this->inputStream = $inputStream;
+		$this->presenter = $presenter;
+	}
+
+
+	public function output($rolling = FALSE)
+	{
+		foreach ($this->inputStream as $inputLine) {
+			$output = $this->presenter->apply($inputLine);
+			if ($rolling) {
+				yield $output;
+			}
+		}
+		if (!$rolling) {
+			yield $output;
+		}
+	}
+}

reader/data.txt

@@ -0,0 +1,10 @@
+[2018-03-13 12:16:10] test.DEBUG: Test message [] []
+[2018-03-13 12:16:10] test.ERROR: Test message [] []
+[2018-03-13 12:16:10] test.WARNING: Test message [] []
+[2018-03-13 12:16:10] test.WARNING: Test message [] []
+[2018-03-13 12:16:10] test.INFO: Test message [] []
+[2018-03-13 12:16:10] test.NOTICE: Test message [] []
+[2018-03-13 12:16:10] test.EMERGENCY: Test message [] []
+[2018-03-13 12:16:10] test.ALERT: Test message [] []
+[2018-03-13 12:16:10] test.ERROR: Test message [] []
+[2018-03-13 12:16:10] test.NOTICE: Test message [] []