small helper to aid in debugging

libp2p/debug.nim

@@ -0,0 +1,68 @@
+## Nim-LibP2P
+## Copyright (c) 2018 Status Research & Development GmbH
+## Licensed under either of
+##  * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE))
+##  * MIT license ([LICENSE-MIT](LICENSE-MIT))
+## at your option.
+## This file may not be copied, modified, or distributed except according to
+## those terms.
+
+## Small debug module that's enabled through a ``-d:debugout``
+## flag. It's inspired by the Nodejs ``debug`` module that
+## allows printing colorized output based on patterns. This 
+## module is powered by the standard ``nre`` module and as such
+## it supports the same set of regexp expressions.
+##
+## To enable debug output, pass the ``debugout`` flag during build
+## time with ``-d`` flag. In addition, the debugout flag takes a comma
+## separated list of patters that will narow the debug output to
+## only those matched by the patterns. By default however, all
+## debug statements are outputed to the stderr.
+
+when defined(debugout) and not defined(release):
+  import random, 
+         tables, 
+         nre, 
+         strutils, 
+         times, 
+         terminal, 
+         sequtils
+
+  const debugout {.strdefine.}: string = ".*"
+
+  type
+    Match = object
+      pattern: Regex
+      color: string
+    
+  var matches: OrderedTable[string, Match] = initOrderedTable[string, Match]()
+  var patrns = @[".*"]
+  if debugout != "true":
+    patrns = debugout.split(re"[,\s]").filterIt(it.len > 0)
+
+  randomize()
+  for p in patrns:
+    matches[p] = Match(pattern: re(p), color: $rand(0..272)) # 256 ansi colors
+  # matches["*"] = Match(pattern: re(".*"), color: $rand(0..272)) # 256 ansi colors
+
+  if isTrueColorSupported():
+    system.addQuitProc(resetAttributes)
+    enableTrueColors()
+
+  proc doDebug(data: string): void {.gcsafe.} = 
+    for m in matches.values:
+      if data.match(m.pattern).isSome:
+        stderr.writeLine("\u001b[38;5;" & m.color & "m " & alignLeft(data, 4) & "\e[0m")
+        return
+
+  template debug*(data: string) = 
+    let module = instantiationInfo()
+    let line = "$# $#:$# - $#" % 
+                  [now().format("yyyy-MM-dd HH:mm:ss:fffffffff"), 
+                  module.filename[0 .. ^5], 
+                  $module.line,
+                  data]
+    doDebug(line)
+
+else:
+  template debug*(data: string) = discard