#!/usr/bin/python2.4
# Copyright 2008, Google Inc.
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"""Main setup for software construction toolkit.

This module is a SCons tool which should be include in all environments.
It is used as follows:
  env = Environment(tools = ['component_setup'])
and should be the first tool from this toolkit referenced by any environment.
"""

import os
import sys
import SCons


#------------------------------------------------------------------------------


def InstallUsingLink(target, source, env):
  """Install function for environment which uses link in preference to copy.

  Args:
    target: Destintion filename
    source: Source filename
    env: Environment

  Returns:
    Return code from SCons Node link function.
  """

  # Use link function for Install() and InstallAs(), since it's much much
  # faster than copying.  This is ok for the way we build clients, where we're
  # installing to a build output directory and not to a permanent location such
  # as /usr/bin.
  # Need to force the target and source to be lists of nodes
  return SCons.Node.FS.LinkFunc([env.Entry(target)], [env.Entry(source)], env)


def PreEvaluateVariables(env):
  """Deferred function to pre-evaluate SCons varables for each build mode.

  Args:
    env: Environment for the current build mode.
  """
  # Convert directory variables to strings.  Must use .abspath not str(), since
  # otherwise $OBJ_ROOT is converted to a relative path, which evaluates
  # improperly in SConscripts not in $MAIN_DIR.
  for var in env.SubstList2('$PRE_EVALUATE_DIRS'):
    env[var] = env.Dir('$' + var).abspath


#------------------------------------------------------------------------------


def generate(env):
  # NOTE: SCons requires the use of this name, which fails gpylint.
  """SCons entry point for this tool."""

  # Use MD5 to tell when files differ, if the timestamps differ.  This is
  # better than pure MD5 (since if the timestamps are the same, we don't need
  # to rescan the file), and also better than pure timestamp (since if a file
  # is rebuilt to the same contents, we don't need to trigger the build steps
  # which depend on it).
  env.Decider('MD5-timestamp')

  # Use implicit-cache by default.  This means that SCons doesn't scan all the
  # directories looking for include files found in an earlier directory in the
  # include path.  For continuous builds, this is not an issue because they're
  # usually clean builds (so there wouldn't be a cache to load anyway).
  #
  # If you're doing a continuous incremental build, just use the
  # --implicit-deps-changed option to force SCons to ignore its implicit cache.
  #
  # Use SCons.Script.SetOption() rather than env.SetOption() to make it clear
  # this is a global setting, not just a setting for the current environment.
  SCons.Script.SetOption('implicit_cache', 1)

  # For duplication order, use hard links then fall back to copying.  Don't use
  # soft links, since those won't do the right thing if the output directory
  # is tar'd up and moved elsewhere.
  SCons.Script.SetOption('duplicate', 'hard-copy')

  # Remove the alias namespace lookup function from the list which SCons uses
  # when coercing strings into nodes.  This prevents SCons from looking up
  # aliases in input/output lists if they're not explicitly coerced via
  # Alias(), and removes a conflict where a program has the same shorthand
  # alias as the program name itself.  This conflict manifests itself as a
  # python exception if you try to build a program in multiple modes on linux,
  # for example:
  #      hammer --mode=dbg,opt port_test
  new_lookup_list = []
  for func in env.lookup_list:
    if func.im_class != SCons.Node.Alias.AliasNameSpace:
      new_lookup_list.append(func)
  env.lookup_list = new_lookup_list

  # Cover part of the environment
  env.Replace(
      # Add a reference to our python executable, so subprocesses can find and
      # invoke python.
      PYTHON = env.File(sys.executable),

      # Get the absolute path to the directory containing main.scons (or
      # SConstruct).  This should be used in place of the SCons variable '#',
      # since '#' is not always replaced (for example, when being used to set
      # an environment variable).
      MAIN_DIR = env.Dir('#').abspath,
      # Supply deprecated SCONSTRUCT_DIR for legacy suport
      # TODO(rspangler): remove legacy support once everyone has switched over.
      SCONSTRUCT_DIR = env.Dir('#').abspath,

      # Use install function above, which uses links in preference to copying.
      INSTALL = InstallUsingLink,
  )

  # Specify defaults for variables where we don't need to force replacement
  env.SetDefault(
      # Environments are in the 'all' group by default
      BUILD_GROUPS=['all'],

      # Directories
      DESTINATION_ROOT='$MAIN_DIR/scons-out$HOST_PLATFORM_SUFFIX',
      TARGET_ROOT='$DESTINATION_ROOT/$BUILD_TYPE',
      OBJ_ROOT='$TARGET_ROOT/obj',
      ARTIFACTS_DIR='$TARGET_ROOT/artifacts',
  )

  # Add default list of variables we should pre-evaluate for each build mode
  env.Append(PRE_EVALUATE_DIRS = [
      'ARTIFACTS_DIR',
      'DESTINATION_ROOT',
      'OBJ_ROOT',
      'SOURCE_ROOT',
      'TARGET_ROOT',
      'TOOL_ROOT',
  ])

  # If a host platform was specified, need to put the SCons output in its own
  # destination directory.  Different host platforms compile the same files
  # different ways, so need their own .sconsign files.
  force_host_platform = SCons.Script.GetOption('host_platform')
  if force_host_platform:
    env['HOST_PLATFORM_SUFFIX'] = '-' + force_host_platform

  # Put the .sconsign.dblite file in our destination root directory, so that we
  # don't pollute the source tree. Use the '_' + sys.platform suffix to prevent
  # the .sconsign.dblite from being shared between host platforms, even in the
  # case where the --host_platform option is not used (for instance when the
  # project has platform suffixes on all the build types).
  # This will prevent host platforms from mistakenly using each others .sconsign
  # databases and will allow two host platform builds to occur in the same
  # shared tree simulataneously.
  sconsign_dir = env.Dir('$DESTINATION_ROOT').abspath
  sconsign_filename = '$DESTINATION_ROOT/.sconsign_%s' % sys.platform
  sconsign_file = env.File(sconsign_filename).abspath
  # TODO(sgk): SConsignFile() doesn't seem to like it if the destination
  # directory doesn't already exists, so make sure it exists.
  if not os.path.isdir(sconsign_dir):
    os.makedirs(sconsign_dir)
  SCons.Script.SConsignFile(sconsign_file)

  # Build all by default
  # TODO(rspangler): This would be more nicely done by creating an 'all'
  # alias and mapping that to $DESTINATION_ROOT (or the accumulation of all
  # $TARGET_ROOT's for the environments which apply to the current host
  # platform).  Ideally, that would be done in site_init.py and not here.  But
  # since we can't do that, just set the default to be DESTINATION_ROOT here.
  # Note that this currently forces projects which want to override the
  # default to do so after including the component_setup tool.
  env.Default('$DESTINATION_ROOT')

  # Use brief command line strings if necessary
  SCons.Script.Help("""\
  --verbose                   Print verbose output while building, including
                              the full command lines for all commands.
  --brief                     Print brief output while building (the default).
                              This and --verbose are opposites.  Use --silent
                              to turn off all output.
""")
  SCons.Script.AddOption(
      '--brief',
      dest='brief_comstr',
      default=True,
      action='store_true',
      help='brief command line output')
  SCons.Script.AddOption(
      '--verbose',
      dest='brief_comstr',
      default=True,
      action='store_false',
      help='verbose command line output')
  if env.GetOption('brief_comstr'):
    env.SetDefault(
        ARCOMSTR='________Creating library $TARGET',
        ASCOMSTR='________Assembling $TARGET',
        CCCOMSTR='________Compiling $TARGET',
        CONCAT_SOURCE_COMSTR='________ConcatSource $TARGET',
        CXXCOMSTR='________Compiling $TARGET',
        LDMODULECOMSTR='________Building loadable module $TARGET',
        LINKCOMSTR='________Linking $TARGET',
        MANIFEST_COMSTR='________Updating manifest for $TARGET',
        MIDLCOMSTR='________Compiling IDL $TARGET',
        PCHCOMSTR='________Precompiling $TARGET',
        RANLIBCOMSTR='________Indexing $TARGET',
        RCCOMSTR='________Compiling resource $TARGET',
        SHCCCOMSTR='________Compiling $TARGET',
        SHCXXCOMSTR='________Compiling $TARGET',
        SHLINKCOMSTR='________Linking $TARGET',
        SHMANIFEST_COMSTR='________Updating manifest for $TARGET',
    )

  # Add other default tools from our toolkit
  # TODO(rspangler): Currently this needs to be before SOURCE_ROOT in case a
  # tool needs to redefine it.  Need a better way to handle order-dependency
  # in tool setup.
  for t in component_setup_tools:
    env.Tool(t)

  # The following environment replacements use env.Dir() to force immediate
  # evaluation/substitution of SCons variables.  They can't be part of the
  # preceding env.Replace() since they they may rely indirectly on variables
  # defined there, and the env.Dir() calls would be evaluated before the
  # env.Replace().

  # Set default SOURCE_ROOT if there is none, assuming we're in a local
  # site_scons directory for the project.
  source_root_relative = os.path.normpath(
      os.path.join(os.path.dirname(__file__), '../..'))
  source_root = env.get('SOURCE_ROOT', source_root_relative)
  env['SOURCE_ROOT'] = env.Dir(source_root).abspath

  # Make tool root separate from source root so it can be overridden when we
  # have a common location for tools outside of the current clientspec.  Need
  # to check if it's defined already, so it can be set prior to this tool
  # being included.
  tool_root = env.get('TOOL_ROOT', '$SOURCE_ROOT')
  env['TOOL_ROOT'] = env.Dir(tool_root).abspath

  # Defer pre-evaluating some environment variables, but do before building
  # SConscripts.
  env.Defer(PreEvaluateVariables)
  env.Defer('BuildEnvironmentSConscripts', after=PreEvaluateVariables)