common, cal: rework debug printers

* prefix messages to indicate the debug level
* colorize when printing to terminal

This introduces a dependency on luaposix.

1 files changed, 39 insertions, 6 deletions

diff --git a/common.lua b/common.lua
index 2c68aee..89153d8 100644
--- a/common.lua
+++ b/common.lua
@@ -1,18 +1,51 @@
-local lpeg = require "lpeg"
+local lpeg          = require "lpeg"
 
 local string        = require "string"
 local stringformat  = string.format
 
 local verboselvl    = 0
+local colorize      = false
 
-local mk_out = function (stream, threshold, newlinep)
+--- check if stderr is pipe; use color otherwise
+local ok, unistd    = pcall (require, "posix.unistd")
+if ok then
+  local stderr_fd = unistd.STDERR_FILENO
+  colorize = unistd.isatty (unistd.STDERR_FILENO) == 1
+end
+
+local esc = '\27['
+
+local colors =
+  { black  = esc .. "0;30m"
+  , red    = esc .. "0;31m"
+  , green  = esc .. "0;32m"
+  , yellow = esc .. "0;33m"
+  , blue   = esc .. "0;34m"
+  , purple = esc .. "0;35m"
+  , cyan   = esc .. "0;36m"
+  , white  = esc .. "0;37m"
+  , reset  = esc .. "m"
+  }
+
+local mk_out = function (stream, threshold, newlinep, pfx, color)
+  if pfx == nil then
+    pfx = ""
+  else
+    if colorize and color ~= nil then
+      local col = colors [color]
+      if col ~= nil then
+        pfx = col .. pfx .. colors.reset end
+      end
+    pfx = "["..pfx.."] "
+  end
   local out = io.stdout
   if stream == "err" or stream == "stderr" then out = io.stderr end
   return function (...)
     if verboselvl >= threshold then
       local ok, msg = pcall (stringformat, ...)
       if ok then
-        out:write (msg)
+        out.write (out, pfx)
+        out.write (out, msg)
         if newlinep == true then out:write "\n" end
       ---else silently ignore
       end
@@ -62,9 +95,9 @@ end
 
 return
   { println               = mk_out ("stdout", 0, true)
-  , errorln               = mk_out ("stderr", 0, true)
-  , noiseln               = mk_out ("stderr", 1, true)
-  , debugln               = mk_out ("stderr", 2, true)
+  , errorln               = mk_out ("stderr", 0, true, "error", "red")
+  , noiseln               = mk_out ("stderr", 1, true, "info" , "yellow")
+  , debugln               = mk_out ("stderr", 2, true, "debug", "purple")
   , set_verbosity         = set_verbosity
   , trim_whitespace       = trim_whitespace
   , unescape_string       = unescape_string