<?php
/**
 * ambre-session-memory.php · AMBRE v1 · per-session memory store
 * Stores/retrieves last N messages per session_id in /var/tmp/wevia-sessions/
 */

class AmbreSessionMemory {
    const DIR = "/var/tmp/wevia-sessions";
    const MAX_TURNS = 20;
    const TTL_HOURS = 24;
    
    public static function init() {
        if (!is_dir(self::DIR)) @mkdir(self::DIR, 0777, true);
    }
    
    public static function path($sid) {
        self::init();
        $safe = preg_replace("/[^a-zA-Z0-9_-]/", "", $sid);
        if (!$safe) $safe = "default";
        return self::DIR . "/" . $safe . ".json";
    }
    
    public static function load($sid) {
        $p = self::path($sid);
        if (!file_exists($p)) return [];
        $content = @file_get_contents($p);
        if (!$content) return [];
        $data = @json_decode($content, true);
        if (!is_array($data)) return [];
        // TTL cleanup
        $now = time();
        $data = array_filter($data, function($m) use ($now) {
            return isset($m["ts"]) && ($now - $m["ts"]) < (self::TTL_HOURS * 3600);
        });
        return array_values($data);
    }
    
    public static function append($sid, $role, $content) {
        if (!$sid || !$role || !$content) return;
        $msgs = self::load($sid);
        $msgs[] = [
            "role" => $role,
            "content" => substr((string)$content, 0, 4000),
            "ts" => time(),
        ];
        // Keep only last N
        if (count($msgs) > self::MAX_TURNS) {
            $msgs = array_slice($msgs, -self::MAX_TURNS);
        }
        @file_put_contents(self::path($sid), json_encode($msgs, JSON_UNESCAPED_UNICODE), LOCK_EX);
    }
    
    public static function context_messages($sid, $max = 10) {
        $msgs = self::load($sid);
        $last = array_slice($msgs, -$max);
        $out = [];
        foreach ($last as $m) {
            $out[] = ["role" => $m["role"], "content" => $m["content"]];
        }
        return $out;
    }
    
    public static function summary($sid) {
        $msgs = self::load($sid);
        return [
            "session" => $sid,
            "turns" => count($msgs),
            "first_ts" => !empty($msgs) ? date("c", $msgs[0]["ts"]) : null,
            "last_ts" => !empty($msgs) ? date("c", end($msgs)["ts"]) : null,
        ];
    }
    
    public static function clear($sid) {
        $p = self::path($sid);
        if (file_exists($p)) @unlink($p);
    }
}

// Direct API usage
if (basename($_SERVER["SCRIPT_NAME"]) === "ambre-session-memory.php") {
    header("Content-Type: application/json");
    $sid = $_GET["sid"] ?? "";
    $action = $_GET["action"] ?? "summary";
    if ($action === "summary") echo json_encode(AmbreSessionMemory::summary($sid));
    elseif ($action === "load") echo json_encode(AmbreSessionMemory::load($sid));
    elseif ($action === "clear") { AmbreSessionMemory::clear($sid); echo json_encode(["cleared"=>true]); }
    else echo json_encode(["error"=>"unknown action"]);
}