snsh.lua

-- Use of this source code is governed by the Apache 2.0 license; see COPYING.

module(..., package.seeall)

local lib = require("core.lib")
local usage = require("program.snsh.README_inc")

local long_opts = {
   ["package-path"] = "P",
   eval = "e",
   load = "l",
   program = "p",
   test = "t",
   interactive = "i",
   debug = "d",
   sigquit = "q",
   help = "h",
}

function run (parameters)
   local start_repl = false
   local noop = true -- are we doing nothing?
   local program -- should we run a different program?
   -- Table of functions implementing command-line arguments
   local opt = {}
   function opt.h (arg) print(usage) main.exit(0)            end
   function opt.l (arg) require(arg)            noop = false end
   function opt.t (arg) require(arg).selftest() noop = false end
   function opt.q (arg) hook_sigquit(arg)                    end
   function opt.d (arg) _G.developer_debug = true            end
   function opt.p (arg) program = arg                        end
   function opt.i (arg) start_repl = true       noop = false end
   function opt.e (arg)
      local thunk, error = loadstring(arg)
      if thunk then thunk() else print(error) end
      noop = false
   end
   function opt.P (arg)
      package.path = arg
   end

   -- Execute command line arguments
   parameters = lib.dogetopt(parameters, opt, "hl:p:t:die:P:q:", long_opts)

   if program then
      local mod = (("program.%s.%s"):format(program, program))
      require(mod).run(parameters)
   elseif #parameters > 0 then
      run_script(parameters)
   elseif noop then
      print(usage)
      main.exit(1)
   end

   if start_repl then repl() end
end

function run_script (parameters)
   local command = table.remove(parameters, 1)
   main.parameters = parameters -- make remaining args available to script
   dofile(command)
end

-- This is a simple REPL similar to LuaJIT's built-in REPL. It can only
-- read single-line statements but does support the `=<expr>' syntax.
function repl ()
   local line = nil
   local function eval_line ()
      if line:sub(0,1) == "=" then
         -- Evaluate line as expression.
         print(loadstring("return "..line:sub(2))())
      else
         -- Evaluate line as statement
         local load = loadstring(line)
         if load then load() end
      end
   end
   repeat
      io.stdout:write("Snabb> ")
      io.stdout:flush()
      line = io.stdin:read("*l")
      if line then
         local status, err = pcall(eval_line)
         if not status then
            io.stdout:write(("Error in %s\n"):format(err))
         end
         io.stdout:flush()
      end
   until not line
end

-- Cause SIGQUIT to enter the REPL.
-- SIGQUIT can be triggered interactively with `Control \' in a terminal.
function hook_sigquit (action)
   if action ~= 'repl' then
      print("ignoring unrecognized SIGQUIT action: " .. action)
      os.exit(1)
   end
   local S = require("syscall")
   local fd = S.signalfd("quit", "nonblock") -- handle SIGQUIT via fd
   S.sigprocmask("block", "quit")            -- block traditional handler
   local timer = require("core.timer")
   timer.activate(timer.new("sigquit-repl",
                            function ()
                               if (#S.util.signalfd_read(fd) > 0) then
                                  print("[snsh: SIGQUIT caught - entering REPL]")
                                  repl()
                               end
                            end,
                            1e4,
                            'repeating'))
end