mirror of
https://github.com/MarekWo/mc-webui.git
synced 2026-08-10 10:42:54 +02:00
fix: prevent duplicate channels from concurrent add/join requests
Two near-simultaneous POSTs to /api/channels/join (observed 7 ms apart in demo-server logs) each found a different free slot and both succeeded, producing two entries for the same channel name on the device. This also shifted the sidebar so each channel rendered the next one's messages. - Wrap free-slot detection + set_channel in a module-level lock so concurrent requests serialize instead of racing. - Idempotency: if a channel with this name already exists, return the existing slot with already_existed=true instead of creating a duplicate. Applies to both POST /api/channels and /api/channels/join (skipped when caller targets an explicit index). - Disable submit buttons on create/join forms while a request is in flight, and guard against double-registration of the channel-link click delegate to stop a single click from firing N POSTs. Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
This commit is contained in:
MarekWo
+127
-75
@@ -9,6 +9,7 @@ import json
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import re
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import base64
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import struct
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import threading
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import time
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import requests
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from Crypto.Cipher import AES
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@@ -42,6 +43,11 @@ _channels_cache = None
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_channels_cache_timestamp = 0
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CHANNELS_CACHE_TTL = 30 # seconds
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# Serializes channel create/join to avoid duplicates from concurrent requests.
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# Without this, two near-simultaneous POSTs both find the same "first free"
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# slot (or adjacent slots) and each succeeds, producing duplicate entries.
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_channel_write_lock = threading.Lock()
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# Cache for contacts/detailed to reduce USB calls (4 calls per request!)
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# Contacts change infrequently, 60s cache is safe
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_contacts_detailed_cache = None
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@@ -1570,36 +1576,58 @@ def create_channel():
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'error': 'Channel name can only contain letters, numbers, _ and -'
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}), 400
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success, message, key = cli.add_channel(name)
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# Serialize create/join so concurrent requests can't both pick a free
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# slot for the same name and produce duplicates.
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with _channel_write_lock:
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# Idempotency: if a channel with this name already exists, return it
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# instead of creating a second slot. Compare case-insensitively.
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invalidate_channels_cache() # force fresh read from device
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success_ch, existing = get_channels_cached(force_refresh=True)
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if success_ch:
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for ch in existing:
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if ch.get('name', '').lower() == name.lower():
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logger.info(f"Channel '{name}' already exists at slot {ch['index']}, returning existing")
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return jsonify({
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'success': True,
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'message': f"Channel '{name}' already exists at slot {ch['index']}",
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'channel': {
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'index': ch['index'],
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'name': ch.get('name', name),
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'key': ch.get('key', ''),
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},
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'already_existed': True,
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}), 200
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if success:
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invalidate_channels_cache() # Clear cache to force refresh
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success, message, key = cli.add_channel(name)
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# Build response
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response = {
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'success': True,
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'message': message,
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'channel': {
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'name': name,
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'key': key
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if success:
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invalidate_channels_cache() # Clear cache to force refresh
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# Build response
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response = {
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'success': True,
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'message': message,
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'channel': {
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'name': name,
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'key': key
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}
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}
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}
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# Check channel count for soft limit warning
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success_ch, channels = get_channels_cached()
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if success_ch and len(channels) > 7:
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response['warning'] = (
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f'You now have {len(channels)} channels. '
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'Some devices may only support up to 8 channels. '
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'Check your device specifications if you experience issues.'
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)
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# Check channel count for soft limit warning
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success_ch, channels = get_channels_cached()
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if success_ch and len(channels) > 7:
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response['warning'] = (
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f'You now have {len(channels)} channels. '
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'Some devices may only support up to 8 channels. '
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'Check your device specifications if you experience issues.'
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)
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return jsonify(response), 201
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else:
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return jsonify({
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'success': False,
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'error': message
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}), 500
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return jsonify(response), 201
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else:
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return jsonify({
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'success': False,
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'error': message
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}), 500
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except Exception as e:
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logger.error(f"Error creating channel: {e}")
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@@ -1641,65 +1669,89 @@ def join_channel():
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'error': 'Key is required for channels not starting with #'
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}), 400
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# Auto-detect free slot if not provided
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if 'index' in data:
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index = int(data['index'])
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else:
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# Find first free slot (1-40, skip 0 which is Public)
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# Hard limit: 40 channels (most LoRa devices support up to 40)
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# Soft limit: 7 channels (some devices may have lower limits)
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success_ch, channels = get_channels_cached()
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# Serialize create/join so concurrent requests can't both pick a free
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# slot for the same name and produce duplicates.
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with _channel_write_lock:
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# Fresh read from device before picking slot or checking duplicates.
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invalidate_channels_cache()
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success_ch, channels = get_channels_cached(force_refresh=True)
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if not success_ch:
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return jsonify({
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'success': False,
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'error': 'Failed to get current channels'
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}), 500
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used_indices = {ch['index'] for ch in channels}
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index = None
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for i in range(1, 41): # Max 40 channels (hard limit)
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if i not in used_indices:
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index = i
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break
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# Idempotency: if a channel with this name already exists, return
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# the existing slot instead of creating a duplicate. Skip this check
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# only when caller explicitly targets an index (explicit overwrite).
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if 'index' not in data:
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for ch in channels:
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if ch.get('name', '').lower() == name.lower():
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logger.info(f"Channel '{name}' already exists at slot {ch['index']}, returning existing")
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return jsonify({
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'success': True,
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'message': f"Already joined channel \"{name}\" at slot {ch['index']}",
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'channel': {
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'index': ch['index'],
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'name': ch.get('name', name),
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'key': ch.get('key', '') or 'auto-generated',
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},
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'already_existed': True,
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}), 200
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if index is None:
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# Auto-detect free slot if not provided
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if 'index' in data:
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index = int(data['index'])
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used_indices = {ch['index'] for ch in channels}
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else:
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# Find first free slot (1-40, skip 0 which is Public)
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# Hard limit: 40 channels (most LoRa devices support up to 40)
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# Soft limit: 7 channels (some devices may have lower limits)
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used_indices = {ch['index'] for ch in channels}
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index = None
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for i in range(1, 41): # Max 40 channels (hard limit)
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if i not in used_indices:
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index = i
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break
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if index is None:
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return jsonify({
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'success': False,
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'error': 'No free channel slots available (max 40 channels)'
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}), 400
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success, message = cli.set_channel(index, name, key)
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if success:
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invalidate_channels_cache() # Clear cache to force refresh
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# Build response
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response = {
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'success': True,
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'message': f'Joined channel "{name}" at slot {index}',
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'channel': {
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'index': index,
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'name': name,
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'key': key if key else 'auto-generated'
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}
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}
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# Add warning if exceeding soft limit (7 channels)
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# Some older/smaller devices may only support 8 channels total
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channel_count = len(used_indices) + 1 # +1 for newly added channel
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if channel_count > 7:
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response['warning'] = (
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f'You now have {channel_count} channels. '
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'Some devices may only support up to 8 channels. '
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'Check your device specifications if you experience issues.'
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)
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return jsonify(response), 200
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else:
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return jsonify({
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'success': False,
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'error': 'No free channel slots available (max 40 channels)'
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}), 400
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success, message = cli.set_channel(index, name, key)
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if success:
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invalidate_channels_cache() # Clear cache to force refresh
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# Build response
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response = {
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'success': True,
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'message': f'Joined channel "{name}" at slot {index}',
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'channel': {
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'index': index,
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'name': name,
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'key': key if key else 'auto-generated'
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}
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}
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# Add warning if exceeding soft limit (7 channels)
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# Some older/smaller devices may only support 8 channels total
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channel_count = len(used_indices) + 1 # +1 for newly added channel
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if channel_count > 7:
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response['warning'] = (
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f'You now have {channel_count} channels. '
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'Some devices may only support up to 8 channels. '
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'Check your device specifications if you experience issues.'
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)
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return jsonify(response), 200
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else:
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return jsonify({
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'success': False,
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'error': message
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}), 500
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'error': message
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}), 500
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except Exception as e:
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logger.error(f"Error joining channel: {e}")
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