my-nvim-lua/lua/telescope/_extensions/terms.lua

-- This file can be loaded as a telescope extension
local M = {}

-- Custom theme picker
-- Most of the code is copied from telescope buffer builtin
-- Src: https://github.com/nvim-telescope/telescope.nvim/blob/master/lua/telescope/builtin/internal.lua
M.term_picker = function(opts)
   local pickers, finders, previewers, make_entry, actions, action_state, utils, conf
   if pcall(require, "telescope") then
      pickers = require "telescope.pickers"
      finders = require "telescope.finders"
      previewers = require "telescope.previewers"

      make_entry = require "telescope.make_entry"
      actions = require "telescope.actions"
      action_state = require "telescope.actions.state"
      utils = require "telescope.utils"
      conf = require("telescope.config").values
   else
      error "Cannot find telescope!"
   end

   local filter = vim.tbl_filter

   local local_utils = require "utils"

   -- buffer number and name
   local bufnr = vim.api.nvim_get_current_buf()
   local bufname = vim.api.nvim_buf_get_name(bufnr)

   local bufnrs = filter(function(b)
      local present_type, type = pcall(function()
         return vim.api.nvim_buf_get_var(b, "term_type")
      end)

      if not present_type then
         -- let's only terms that we created
         return false
      end

      -- if 1 ~= vim.fn.buflisted(b) then
      --    return false
      -- end
      -- only hide unloaded buffers if opts.show_all_buffers is false, keep them listed if true or nil
      if opts.show_all_buffers == false and not vim.api.nvim_buf_is_loaded(b) then
         return false
      end
      if opts.ignore_current_buffer and b == vim.api.nvim_get_current_buf() then
         return false
      end
      return true
   end, vim.api.nvim_list_bufs())
   if not next(bufnrs) then
      return
   end
   if opts.sort_mru then
      table.sort(bufnrs, function(a, b)
         return vim.fn.getbufinfo(a)[1].lastused > vim.fn.getbufinfo(b)[1].lastused
      end)
   end

   local buffers = {}
   local default_selection_idx = 1
   for _, bufnr in ipairs(bufnrs) do
      local flag = bufnr == vim.fn.bufnr "" and "%" or (bufnr == vim.fn.bufnr "#" and "#" or " ")

      if opts.sort_lastused and not opts.ignore_current_buffer and flag == "#" then
         default_selection_idx = 2
      end

      local element = {
         bufnr = bufnr,
         flag = flag,
         info = vim.fn.getbufinfo(bufnr)[1],
      }

      if opts.sort_lastused and (flag == "#" or flag == "%") then
         local idx = ((buffers[1] ~= nil and buffers[1].flag == "%") and 2 or 1)
         table.insert(buffers, idx, element)
      else
         table.insert(buffers, element)
      end
   end

   if not opts.bufnr_width then
      local max_bufnr = math.max(unpack(bufnrs))
      opts.bufnr_width = #tostring(max_bufnr)
   end

   pickers.new(opts, {
      prompt_title = "Terminal buffers",
      finder = finders.new_table {
         results = buffers,
         entry_maker = opts.entry_maker or make_entry.gen_from_buffer(opts),
      },
      previewer = conf.grep_previewer(opts),
      sorter = conf.generic_sorter(opts),
      default_selection_index = default_selection_idx,
      attach_mappings = function(prompt_bufnr)
         actions.select_default:replace(function()
            local entry = action_state.get_selected_entry()
            actions.close(prompt_bufnr)

            local buf = entry.bufnr

            local chad_term, type = pcall(function()
               return vim.api.nvim_buf_get_var(buf, "term_type")
            end)

            -- TODO buffer checks/error detection (make sure we do get a buf)

            if chad_term then
               if type == "wind" then
                  -- swtich to term buff & show in bufferline
                  vim.cmd(string.format("b %d | setlocal bl", buf))
                  -- vim.cmd('startinsert') TODO fix this
               elseif type == "vert" then
                  vim.cmd(string.format("vsp #%d", buf))
                  -- vim.cmd('startinsert') TODO fix this
               elseif type == "hori" then
                  -- TODO change 15 to a chad config var number
                  vim.cmd(string.format("15 sp #%d ", buf))
                  -- vim.cmd('startinsert') TODO fix this
               end
            end
         end)

         return true
      end,
   }):find()
end

-- register term picker as terms to telescope
local present, telescope = pcall(require, "telescope")
if present then
   return telescope.register_extension {
      exports = {
         terms = M.term_picker,
      },
   }
else
   error "Cannot find telescope!"
end