Initial commit

src/ContextRequest.php

@@ -0,0 +1,102 @@
+<?php
+
+declare(strict_types=1);
+
+namespace ContextPaging;
+
+use GuzzleHttp\Psr7\ServerRequest;
+use Psr\Http\Message\ServerRequestInterface;
+
+/**
+ * Extended ServerRequest with context size tracking.
+ */
+class ContextRequest extends ServerRequest
+{
+    private ?TokenCounter $tokenCounter = null;
+
+    /**
+     * Create from a standard ServerRequestInterface.
+     */
+    public static function fromRequest(ServerRequestInterface $request): self
+    {
+        return new self(
+            method: $request->getMethod(),
+            uri: $request->getUri(),
+            headers: $request->getHeaders(),
+            body: $request->getBody(),
+            version: $request->getProtocolVersion(),
+            serverParams: $request->getServerParams()
+        );
+    }
+
+    /**
+     * Set the token counter instance.
+     */
+    public function withTokenCounter(TokenCounter $counter): self
+    {
+        $new = clone $this;
+        $new->tokenCounter = $counter;
+        return $new;
+    }
+
+    /**
+     * Get the token counter (lazy-load default if not set).
+     */
+    public function getTokenCounter(): TokenCounter
+    {
+        if ($this->tokenCounter === null) {
+            $this->tokenCounter = new TokenCounter();
+        }
+        return $this->tokenCounter;
+    }
+
+    /**
+     * Calculate and store context size for the given messages.
+     *
+     * @param array $messages Array of ['role' => '...', 'content' => '...']
+     * @param string $encoding Encoding name (cl100k_base or o200k_base).
+     * @param int $perMessage Overhead tokens per message.
+     * @param int $replyPrimer Tokens added after all messages.
+     * @return self New request instance with context_size attribute.
+     */
+    public function contextSize(
+        array $messages,
+        string $encoding = 'cl100k_base',
+        int $perMessage = 4,
+        int $replyPrimer = 3
+    ): self {
+        $count = $this->getTokenCounter()->contextSize(
+            $messages,
+            $encoding,
+            $perMessage,
+            $replyPrimer
+        );
+
+        return $this->withAttribute('context_size', [
+            'tokens' => $count,
+            'encoding' => $encoding,
+            'message_count' => count($messages),
+            'per_message' => $perMessage,
+            'reply_primer' => $replyPrimer,
+        ]);
+    }
+
+    /**
+     * Get the stored context size, if any.
+     *
+     * @return array|null ['tokens' => int, 'encoding' => string, ...]
+     */
+    public function getContextSize(): ?array
+    {
+        return $this->getAttribute('context_size');
+    }
+
+    /**
+     * Get just the token count from stored context size.
+     */
+    public function getContextTokenCount(): ?int
+    {
+        $ctx = $this->getContextSize();
+        return $ctx['tokens'] ?? null;
+    }
+}