Add history support

README.md

@@ -14,6 +14,7 @@ Async, event-driven and UTF-8 aware standard console input & output (STDIN, STDO
     * [Echo](#echo)
     * [Input buffer](#input-buffer)
     * [Cursor](#cursor)
+    * [History](#history)
   * [Advanced](#advanced)
     * [Stdout](#stdout)
     * [Stdin](#stdin)
@@ -283,6 +284,99 @@ For example, to move the cursor one character to the left, simply call:
 $readline->moveCursorBy(-1);
 ```
 
+#### History
+
+By default, users can access the history of previous commands by using their
+UP and DOWN cursor keys on the keyboard.
+The history will start with an empty state, thus this feature is effectively
+disabled, as the UP and DOWN cursor keys have no function then.
+
+Note that the history is not maintained automatically.
+Any input the user submits by hitting enter will *not* be added to the history
+automatically.
+This may seem inconvenient at first, but it actually gives you more control over
+what (and when) lines should be added to the history.
+If you want to automatically add everything from the user input to the history,
+you may want to use something like this:
+
+```php
+$readline->on('data', function ($line) use ($readline) {
+    $all = $readline->listHistory();
+
+    // skip empty line and duplicate of previous line
+    if (trim($line) !== '' && $line !== end($all)) {
+        $readline->addHistory($line);
+    }
+});
+```
+
+The `listHistory(): string[]` method can be used to
+return an array with all lines in the history.
+This will be an empty array until you add new entries via `addHistory()`.
+
+```php
+$list = $readline->listHistory();
+
+assert(count($list) === 0);
+```
+
+The `addHistory(string $line): Readline` method can be used to
+add a new line to the (bottom position of the) history list.
+A following `listHistory()` call will return this line as the last element.
+
+```php
+$readline->addHistory('a');
+$readline->addHistory('b');
+
+$list = $readline->listHistory();
+assert($list === array('a', 'b'));
+```
+
+The `clearHistory(): Readline` method can be used to
+clear the complete history list.
+A following `listHistory()` call will return an empty array until you add new
+entries via `addHistory()` again.
+Note that the history feature will effectively be disabled if the history is
+empty, as the UP and DOWN cursor keys have no function then.
+
+```php
+$readline->clearHistory();
+
+$list = $readline->listHistory();
+assert(count($list) === 0);
+```
+
+The `limitHistory(?int $limit): Readline` method can be used to
+set a limit of history lines to keep in memory.
+By default, only the last 500 lines will be kept in memory and everything else
+will be discarded.
+You can use an integer value to limit this to the given number of entries or
+use `null` for an unlimited number (not recommended, because everything is
+kept in RAM).
+If you set the limit to `0` (int zero), the history will effectively be
+disabled, as no lines can be added to or returned from the history list.
+If you're building a CLI application, you may also want to use something like
+this to obey the `HISTSIZE` environment variable:
+
+```php
+$limit = getenv('HISTSIZE');
+if ($limit === '' || $limit < 0) {
+    // empty string or negative value means unlimited
+    $readline->limitHistory(null);
+} elseif ($limit !== false) {
+    // apply any other value if given
+    $readline->limitHistory($limit);
+}
+```
+
+There is no such thing as a `readHistory()` or `writeHistory()` method
+because filesystem operations are inherently blocking and thus beyond the scope
+of this library.
+Using your favorite filesystem API and an appropriate number of `addHistory()`
+or a single `listHistory()` call respectively should be fairly straight
+forward and is left up as an exercise for the reader of this documentation
+(i.e. *you*).
+
 ### Advanced
 
 #### Stdout

examples/periodic.php

@@ -7,8 +7,29 @@
 $loop = React\EventLoop\Factory::create();
 
 $stdio = new Stdio($loop);
-
-$stdio->getReadline()->setPrompt('> ');
+$readline = $stdio->getReadline();
+
+$readline->setPrompt('> ');
+
+// limit history to HISTSIZE env
+$limit = getenv('HISTSIZE');
+if ($limit === '' || $limit < 0) {
+    // empty string or negative value means unlimited
+    $readline->limitHistory(null);
+} elseif ($limit !== false) {
+    // apply any other value if given
+    $readline->limitHistory($limit);
+}
+
+// add all lines from input to history
+$readline->on('data', function ($line) use ($readline) {
+    $all = $readline->listHistory();
+
+    // skip empty line and duplicate of previous line
+    if (trim($line) !== '' && $line !== end($all)) {
+        $readline->addHistory($line);
+    }
+});
 
 $stdio->writeln('Will print periodic messages until you type "quit" or "exit"');
 

src/Readline.php

@@ -17,14 +17,18 @@ class Readline extends EventEmitter implements ReadableStreamInterface
     private $echo = true;
     private $autocomplete = null;
     private $move = true;
-    private $history = null;
     private $encoding = 'utf-8';
 
     private $input;
     private $output;
     private $sequencer;
     private $closed = false;
 
+    private $historyLines = array();
+    private $historyPosition = null;
+    private $historyUnsaved = null;
+    private $historyLimit = 500;
+
     public function __construct(ReadableStreamInterface $input, WritableStreamInterface $output)
     {
         $this->input = $input;
@@ -311,17 +315,73 @@ public function getInput()
     }
 
     /**
-     * set history handler to use (or none)
+     * Adds a new line to the (bottom position of the) history list
      *
-     * The history handler will be called whenever the user hits the UP or DOWN
-     * arrow keys.
+     * @param string $line
+     * @return self
+     * @uses self::limitHistory() to make sure list does not exceed limits
+     */
+    public function addHistory($line)
+    {
+        $this->historyLines []= $line;
+
+        return $this->limitHistory($this->historyLimit);
+    }
+
+    /**
+     * Clears the complete history list
      *
-     * @param HistoryInterface|null $history
      * @return self
      */
-    public function setHistory(HistoryInterface $history = null)
+    public function clearHistory()
+    {
+        $this->historyLines = array();
+        $this->historyPosition = null;
+
+        if ($this->historyUnsaved !== null) {
+            $this->setInput($this->historyUnsaved);
+            $this->historyUnsaved = null;
+        }
+
+        return $this;
+    }
+
+    /**
+     * Returns an array with all lines in the history
+     *
+     * @return string[]
+     */
+    public function listHistory()
     {
-        $this->history = $history;
+        return $this->historyLines;
+    }
+
+    /**
+     * Limits the history to a maximum of N entries and truncates the current history list accordingly
+     *
+     * @param int|null $limit
+     * @return self
+     */
+    public function limitHistory($limit)
+    {
+        $this->historyLimit = $limit === null ? null : (int)$limit;
+
+        // limit send and currently exceeded
+        if ($this->historyLimit !== null && isset($this->historyLines[$this->historyLimit])) {
+            // adjust position in history according to new position after applying limit
+            if ($this->historyPosition !== null) {
+                $this->historyPosition -= count($this->historyLines) - $this->historyLimit;
+
+                // current position will drop off from list => restore original
+                if ($this->historyPosition < 0) {
+                    $this->setInput($this->historyUnsaved);
+                    $this->historyPosition = null;
+                    $this->historyUnsaved = null;
+                }
+            }
+
+            $this->historyLines = array_slice($this->historyLines, -$this->historyLimit, $this->historyLimit);
+        }
 
         return $this;
     }
@@ -468,16 +528,40 @@ public function onKeyRight()
     /** @internal */
     public function onKeyUp()
     {
-        if ($this->history !== null) {
-            $this->history->up();
+        // ignore if already at top or history is empty
+        if ($this->historyPosition === 0 || !$this->historyLines) {
+            return;
+        }
+
+        if ($this->historyPosition === null) {
+            // first time up => move to last entry
+            $this->historyPosition = count($this->historyLines) - 1;
+            $this->historyUnsaved = $this->getInput();
+        } else {
+            // somewhere in the list => move by one
+            $this->historyPosition--;
         }
+
+        $this->setInput($this->historyLines[$this->historyPosition]);
     }
 
     /** @internal */
     public function onKeyDown()
     {
-        if ($this->history !== null) {
-            $this->history->down();
+        // ignore if not currently cycling through history
+        if ($this->historyPosition === null) {
+            return;
+        }
+
+        if (isset($this->historyLines[$this->historyPosition + 1])) {
+            // this is still a valid position => advance by one and apply
+            $this->historyPosition++;
+            $this->setInput($this->historyLines[$this->historyPosition]);
+        } else {
+            // moved beyond bottom => restore original unsaved input
+            $this->setInput($this->historyUnsaved);
+            $this->historyPosition = null;
+            $this->historyUnsaved = null;
         }
     }
 
@@ -537,6 +621,10 @@ public function deleteChar($n)
      */
     protected function processLine()
     {
+        // reset history cycle position
+        $this->historyPosition = null;
+        $this->historyUnsaved = null;
+
         // store and reset/clear/redraw current input
         $line = $this->linebuffer;
         if ($line !== '') {
@@ -548,9 +636,6 @@ protected function processLine()
         }
 
         // process stored input buffer
-        if ($this->history !== null) {
-            $this->history->addLine($line);
-        }
         $this->emit('data', array($line));
     }