#! /usr/bin/env python

# encoding: utf-8

# Thomas Nagy, 2010 (ita)

"""

This tool modifies the task signature scheme to store and obtain

information about the task execution (why it must run, etc)::

	def configure(conf):

		conf.load('why')

After adding the tool, a full rebuild is necessary:

waf clean build --zones=task

"""

from waflib import Task, Utils, Logs, Errors

def signature(self):

	# compute the result one time, and suppose the scan_signature will give the good result

	try:

		return self.cache_sig

	except AttributeError:

		pass

	self.m = Utils.md5()

	self.m.update(self.hcode)

	id_sig = self.m.digest()

	# explicit deps

	self.m = Utils.md5()

	self.sig_explicit_deps()

	exp_sig = self.m.digest()

	# env vars

	self.m = Utils.md5()

	self.sig_vars()

	var_sig = self.m.digest()

	# implicit deps / scanner results

	self.m = Utils.md5()

	if self.scan:

		try:

			self.sig_implicit_deps()

		except Errors.TaskRescan:

			return self.signature()

	impl_sig = self.m.digest()

	ret = self.cache_sig = impl_sig + id_sig + exp_sig + var_sig

	return ret

Task.Task.signature = signature

old = Task.Task.runnable_status

def runnable_status(self):

	ret = old(self)

	if ret == Task.RUN_ME:

		try:

			old_sigs = self.generator.bld.task_sigs[self.uid()]

		except (KeyError, AttributeError):

			Logs.debug("task: task must run as no previous signature exists")

		else:

			new_sigs = self.cache_sig

			def v(x):

				return Utils.to_hex(x)

			Logs.debug('Task %r', self)

			msgs = ['* Implicit or scanner dependency', '* Task code', '* Source file, explicit or manual dependency', '* Configuration data variable']

			tmp = 'task: -> %s: %s %s'

			for x in range(len(msgs)):

				l = len(Utils.SIG_NIL)

				a = new_sigs[x*l : (x+1)*l]

				b = old_sigs[x*l : (x+1)*l]

				if (a != b):

					Logs.debug(tmp, msgs[x].ljust(35), v(a), v(b))

	return ret

Task.Task.runnable_status = runnable_status