add notification for new post in thread

lib/sse.lua

@@ -0,0 +1,59 @@
+---@class SSE
+---@field active boolean if the stream is not active, you should stop the loop.
+---@field private _queue table
+local sse = {}
+
+---Construct a new SSE object
+---@return SSE
+function sse:new()
+  ngx.header.content_type = "text/event-stream"
+  ngx.header.cache_control = "no-cache"
+  ngx.header.connection = "keep-alive"
+  ngx.status = ngx.HTTP_OK
+  ngx.flush(true)
+
+  local obj = {
+    active = true,
+    _queue = {},
+  }
+
+  ngx.on_abort(function()
+    obj.active = false
+  end)
+
+  return setmetatable(obj, {__index = sse})
+end
+
+---add data to the stream, writing on the next dispatch.
+---if `event` is given, it will be the key.
+---@param data string
+---@param event? string
+---@return boolean status
+function sse:enqueue(data, event)
+  if not self.active then return false end
+  table.insert(self._queue, {
+    data = data,
+    event = event,
+  })
+  return true
+end
+
+---send all events since the last dispatch and flush the queue.
+---call this every iteration of the loop.
+function sse:dispatch()
+  while #self._queue > 0 do
+    local msg = table.remove(self._queue, 1)
+    if msg.event then
+      ngx.print("event: " .. msg.event .. "\n")
+    end
+    ngx.print("data: " .. msg.data .. "\n\n")
+  end
+  ngx.flush(true)
+end
+
+---close the stream.
+function sse:close()
+  self.active = false
+end
+
+return sse