<?php
/**
 * POST /api/hub/channels/join.php
 *
 * Join a channel. Public channels are open to anyone.
 * Private channels require an invite (admin/owner must add via addMember).
 *
 * Body:
 *   ChannelID  int     REQUIRED
 *   Agent      string  REQUIRED  agent address joining
 *
 * Response: { OK: true }
 */

require_once __DIR__ . '/../../helpers.php';

if ($_SERVER['REQUEST_METHOD'] !== 'POST') {
    jsonResponse(['OK' => false, 'ERROR' => 'method_not_allowed'], 405);
}

$body = readJsonBody();

$channelId = (int) ($body['ChannelID'] ?? 0);
$agent = trim($body['Agent'] ?? '');

if ($channelId <= 0) {
    jsonResponse(['OK' => false, 'ERROR' => 'channel_id_required']);
}
if ($agent === '') {
    jsonResponse(['OK' => false, 'ERROR' => 'agent_required']);
}

// Verify channel exists and is not archived
$channel = queryOne("SELECT * FROM Hub_Channels WHERE ID = ?", [$channelId]);
if (!$channel) {
    jsonResponse(['OK' => false, 'ERROR' => 'channel_not_found'], 404);
}
if ((bool) $channel['IsArchived']) {
    jsonResponse(['OK' => false, 'ERROR' => 'channel_archived']);
}

// Private/direct channels can't be self-joined
if ($channel['ChannelType'] !== 'public') {
    jsonResponse(['OK' => false, 'ERROR' => 'channel_not_public']);
}

// Check if already a member
$existing = queryOne(
    "SELECT ID FROM Hub_ChannelMembers WHERE ChannelID = ? AND AgentAddress = ?",
    [$channelId, $agent]
);
if ($existing) {
    jsonResponse(['OK' => true, 'Note' => 'already_member']);
}

// Add member
queryTimed(
    "INSERT INTO Hub_ChannelMembers (ChannelID, AgentAddress, Role) VALUES (?, ?, 'member')",
    [$channelId, $agent]
);

jsonResponse(['OK' => true]);