add history to shop search

src/Context/ContextService.php

@@ -72,12 +72,69 @@ final class ContextService
             return '';
         }
 
-        $maxLines = $full ? ContextServiceConfig::MAX_FULL_LINES : ContextServiceConfig::MAX_VISIBLE_REGULAR_LINES;
+        $maxLines = $full
+            ? ContextServiceConfig::MAX_FULL_LINES
+            : ContextServiceConfig::MAX_VISIBLE_REGULAR_LINES;
+
         $selected = array_slice($lines, -$maxLines);
 
         return implode("\n", $selected);
     }
 
+    /**
+     * Returns as much recent history as possible within a character budget.
+     *
+     * Strategy:
+     * - Preserve complete conversation turns whenever possible
+     * - Prioritize the newest turns
+     * - Only truncate when even the newest single turn is larger than the budget
+     *
+     * A turn starts with "Question: " and includes the corresponding assistant answer.
+     */
+    public function buildUserContextWithinBudget(string $userId, int $maxChars): string
+    {
+        if ($maxChars <= 0) {
+            return '';
+        }
+
+        $history = $this->readHistoryFile($userId);
+        if ($history === '') {
+            return '';
+        }
+
+        $turns = $this->splitHistoryIntoTurns($history);
+        if ($turns === []) {
+            return $this->truncateTurnToBudget($history, $maxChars);
+        }
+
+        $selected = [];
+        $currentLength = 0;
+
+        for ($i = count($turns) - 1; $i >= 0; $i--) {
+            $turn = $turns[$i];
+            $turnLength = mb_strlen($turn);
+            $separatorLength = $selected === [] ? 0 : 2; // "\n\n"
+
+            if (($currentLength + $separatorLength + $turnLength) <= $maxChars) {
+                array_unshift($selected, $turn);
+                $currentLength += $separatorLength + $turnLength;
+                continue;
+            }
+
+            // If nothing fits yet, keep at least the newest turn in truncated form.
+            if ($selected === []) {
+                $truncatedTurn = $this->truncateTurnToBudget($turn, $maxChars);
+                if ($truncatedTurn !== '') {
+                    $selected[] = $truncatedTurn;
+                }
+            }
+
+            break;
+        }
+
+        return implode("\n\n", $selected);
+    }
+
     /**
      * Appends a completed interaction to the user's history.
      *
@@ -105,6 +162,82 @@ final class ContextService
         }
     }
 
+    /**
+     * Reads the raw history file contents for a user.
+     */
+    private function readHistoryFile(string $userId): string
+    {
+        $path = $this->getHistoryPath($userId);
+
+        if (!is_file($path)) {
+            return '';
+        }
+
+        $content = file_get_contents($path);
+
+        if ($content === false) {
+            return '';
+        }
+
+        return trim($content);
+    }
+
+    /**
+     * Splits append-only history into complete turns.
+     *
+     * Each turn starts with "Question: ".
+     */
+    private function splitHistoryIntoTurns(string $history): array
+    {
+        $history = trim($history);
+        if ($history === '') {
+            return [];
+        }
+
+        $parts = preg_split('/(?=^Question:\s)/m', $history);
+        if ($parts === false) {
+            return [];
+        }
+
+        $turns = [];
+
+        foreach ($parts as $part) {
+            $part = trim($part);
+
+            if ($part === '') {
+                continue;
+            }
+
+            $turns[] = $part;
+        }
+
+        return $turns;
+    }
+
+    /**
+     * Truncates a single turn to fit into the available budget.
+     *
+     * The start of the turn is preserved so the "Question: ..." marker remains intact.
+     */
+    private function truncateTurnToBudget(string $turn, int $maxChars): string
+    {
+        $turn = trim($turn);
+
+        if ($turn === '' || $maxChars <= 0) {
+            return '';
+        }
+
+        if (mb_strlen($turn) <= $maxChars) {
+            return $turn;
+        }
+
+        if ($maxChars <= 3) {
+            return mb_substr($turn, 0, $maxChars);
+        }
+
+        return rtrim(mb_substr($turn, 0, $maxChars - 3)) . '...';
+    }
+
     /**
      * Resolves the absolute history file path for a user.
      */
@@ -114,4 +247,4 @@ final class ContextService
 
         return $this->historyDir . '/' . $safeUserId . '.txt';
     }
-}
+}