<?php
/**
 * Module G1: DM Conversations List Aggregator
 * Target Path: htdocs/api/v1/direct_v2/inbox.php
 */

require_once __DIR__ . '/../../../config.php';

if ($_SERVER['REQUEST_METHOD'] !== 'GET') {
    http_response_code(405);
    die(json_encode(["status" => "fail", "message" => "Method not allowed."]));
}

$sessionCookie = $_COOKIE['sessionid'] ?? '';
if (empty($sessionCookie) || strpos($sessionCookie, 'nostolga_sess_') !== 0) {
    http_response_code(401);
    die(json_encode(["status" => "fail", "message" => "Unauthorized session context."]));
}
$userId = (int)str_replace('nostolga_sess_', '', $sessionCookie);

$db = getDB();

try {
    // Check for the most recent message exchanged by this user
    $stmt = $db->prepare("SELECT * FROM direct_messages 
                          WHERE sender_id = ? OR recipient_id = ? 
                          ORDER BY id DESC LIMIT 1");
    $stmt->execute([$userId, $userId]);
    $lastMsg = $stmt->fetch();

    $threads = [];

    if ($lastMsg) {
        // Active conversation exists -> Determine the opposing chatter's profile
        $otherUserId = ($lastMsg['sender_id'] == $userId) ? $lastMsg['recipient_id'] : $lastMsg['sender_id'];
        
        $userStmt = $db->prepare("SELECT id, username, full_name, profile_pic FROM users WHERE id = ?");
        $userStmt->execute([$otherUserId]);
        $otherUser = $userStmt->fetch();

        if ($otherUser) {
            $threads[] = [
                "thread_id" => "thread_" . $otherUser['id'],
                "users" => [[
                    "pk" => (int)$otherUser['id'],
                    "username" => $otherUser['username'],
                    "full_name" => $otherUser['full_name'],
                    "profile_pic_url" => $otherUser['profile_pic'] ?? 'https://picsum.photos/150/150'
                ]],
                "last_activity_at" => (int)$lastMsg['created_at'] * 1000000,
                "items" => [[
                    "item_id" => (string)$lastMsg['id'],
                    "user_id" => (int)$lastMsg['sender_id'],
                    "timestamp" => (int)$lastMsg['created_at'] * 1000000,
                    "item_type" => "text",
                    "text" => $lastMsg['message_text']
                ]],
                "canonical" => true,
                "named" => false
            ];
        }
    } else {
        // Fallback welcoming chat thread
        $threads[] = [
            "thread_id" => "thread_999",
            "users" => [[
                "pk" => 999,
                "username" => "nostolga_support",
                "full_name" => "System Direct Engine",
                "profile_pic_url" => "https://picsum.photos/150/150"
            ]],
            "last_activity_at" => time() * 1000000,
            "items" => [[
                "item_id" => "mock_msg_001",
                "user_id" => 999,
                "timestamp" => time() * 1000000,
                "item_type" => "text",
                "text" => "Welcome to Direct Messages! Your chat nodes are active. Broadcast a message to test."
            ]],
            "canonical" => true,
            "named" => false
        ];
    }

    http_response_code(200);
    echo json_encode([
        "inbox" => [
            "threads" => $threads,
            "unseen_count" => 0,
            "unseen_count_ts" => time() * 1000000
        ],
        "status" => "ok"
    ]);
    exit;

} catch (PDOException $e) {
    http_response_code(500);
    die(json_encode(["status" => "fail", "message" => "Inbox matrix retrieval failure."]));
}