local alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
local function base64(text)
   local out = {}
   for i = 1, #text, 3 do
      local a, b, c = text:byte(i, i + 2)
      local n = a * 65536 + (b or 0) * 256 + (c or 0)
      local function digit(shift)
         local index = math.floor(n / 2 ^ shift) % 64 + 1
         return alphabet:sub(index, index)
      end
      out[#out + 1] = digit(18) .. digit(12) .. (b and digit(6) or "=") .. (c and digit(0) or "=")
   end
   return table.concat(out)
end

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

local function command_status(name)
   name = name or "?"
   if name == "compact" then return "compacting" end
   if name == "!" or name == "!!" then return "shell" end
   return "cmd:" .. name:sub(1, 28)
end

return {
   name = "report-status",
   activate = function()
      local uv = require("luv")
      local function terminal_key()
         if uv.guess_handle(1) ~= "tty" then return end
         local stat = uv.fs_fstat(1)
         if stat then return table.concat({ stat.dev, stat.ino, stat.rdev }, ":") end
      end
      local terminal = terminal_key()
      if not terminal then return end
      -- Preserve ownership across /new, but don't let a nested panto overwrite
      -- or clear its parent's status. A different terminal may report normally.
      local owner = terminal .. "@" .. string.format("%.0f", uv.os_getpid())
      local inherited = os.getenv("PANTO_REPORT_STATUS_OWNER")
      if inherited ~= owner and (inherited or ""):match("^(.*)@") == terminal then return end
      uv.os_setenv("PANTO_REPORT_STATUS_OWNER", owner)

      local panto = require("panto")
      local last_state, last_status
      local foreground_working, foreground_status = false, nil
      local background_work = 0
      local settled_state = "idle"
      local ended = false

      local function report(state, status)
         if state == last_state and status == last_status then return end
         -- Print mode can restore a redirected stdout after activation. Never
         -- put control sequences in a pipe, file, or a different terminal.
         if terminal_key() ~= terminal then return end
         local sequence = "\27]7501;state=" .. state .. ":app=panto"
         if status then
            -- Preserve Herdr's label selection/truncation; sanitize only at
            -- the OSC boundary, whose free-text fields forbid controls.
            sequence = sequence .. ":msg=" .. base64((status:gsub("[^ -~]", "?")))
         end
         sequence = sequence .. "\27\\"
         local offset = 0
         while offset < #sequence do
            local written, err = uv.fs_write(1, sequence:sub(offset + 1), -1)
            if not written or written == 0 then
               error("panto-report-status: terminal write failed: " .. tostring(err or "short write"))
            end
            offset = offset + written
         end
         last_state, last_status = state, status
      end

      local function update()
         if ended then return end
         if foreground_working or background_work > 0 then
            report("working", foreground_working and foreground_status or "background")
         else
            report(settled_state)
         end
      end

      local function foreground(status)
         foreground_working, foreground_status, settled_state = true, status, "done"
         update()
      end

      local function finish(event)
         if foreground_working then
            local reason = event and event.reason
            settled_state = reason == "failed" and "error"
               or ((reason == "interrupted" or reason == "exit_requested") and "idle" or "done")
         end
         foreground_working, foreground_status = false, nil
         update()
      end

      panto.ext.on("session_ready", function()
         foreground_working, foreground_status, background_work, settled_state = false, nil, 0, "idle"
         update()
      end)
      panto.ext.on("turn_start", function() foreground("thinking") end)
      panto.ext.on("agent_submission", function() foreground("thinking") end)
      panto.ext.on("render_thinking", function() foreground("thinking") end)
      panto.ext.on("command_start", function(event) foreground(command_status(event.command_name)) end)
      panto.ext.on("command_end", finish)
      panto.ext.on("render_compaction", function()
         if foreground_working then foreground("compacting") end
      end)
      panto.ext.on("render_tool_details", function(event) foreground(tool_status(event.tool_name)) end)
      panto.ext.on("render_assistant_text", function() foreground("responding") end)
      panto.ext.on("turn_end", finish)
      panto.ext.on("background_work_start", function()
         if not foreground_working and background_work == 0 then settled_state = "done" end
         background_work = background_work + 1
         update()
      end)
      panto.ext.on("background_work_end", function()
         background_work = math.max(0, background_work - 1)
         update()
      end)
      panto.ext.on("session_end", function()
         ended = true
         report("clear")
      end)
   end,
}