local function tool_status(name)
   name = name or "?"
   return "tool:" .. name:sub(1, 27)
end

return {
   name = "herdr",
   activate = function()
      local pane_id = os.getenv("HERDR_PANE_ID")
      if not pane_id or pane_id == "" then return end

      local panto = require("panto")
      local uv = require("luv")
      -- Herdr orders reports by source and sequence. Seed each process from
      -- wall time so a restarted panto cannot be shadowed by the prior
      -- process's larger sequence numbers.
      local seq = os.time() * 1000000
      local last_state
      local last_status

      local function spawn(args)
         local handle
         pcall(function()
            handle = uv.spawn("herdr", { args = args, stdio = { nil, nil, nil } }, function()
               if handle then handle:close() end
            end)
         end)
      end

      local function report(state, status)
         if state == last_state and status == last_status then return end
         last_state, last_status = state, status
         seq = seq + 1

         local args = {
            "pane", "report-agent", pane_id,
            "--source", "panto:extension",
            "--agent", "panto",
            "--state", state,
            "--seq", tostring(seq),
         }
         if status then
            args[#args + 1] = "--message"
            args[#args + 1] = status
         end

         spawn(args)
      end

      local function release()
         seq = seq + 1
         spawn({
            "pane", "release-agent", pane_id,
            "--source", "panto:extension",
            "--agent", "panto",
            "--seq", tostring(seq),
         })
      end

      panto.ext.on("session_start", function() report("idle") end)
      panto.ext.on("session_ready", function() report("idle") end)
      panto.ext.on("user_message", function() report("working", "thinking") end)
      panto.ext.on("thinking", function() report("working", "thinking") end)
      panto.ext.on("compaction", function() report("working", "compacting") end)
      panto.ext.on("tool_details", function(event)
         report("working", tool_status(event.tool_name))
      end)
      panto.ext.on("assistant_text", function() report("working", "responding") end)
      panto.ext.on("assistant_text_complete", function() report("idle") end)
      panto.ext.on("session_end", release)
   end,
}