# Copyright 2005 Vladimir Prus.
# Distributed under the Boost Software License, Version 1.0. (See
# accompanying file LICENSE_1_0.txt or copy at
# http://www.boost.org/LICENSE_1_0.txt)

# Defines main target 'cast', used to change type for target. For example,
# in Qt library one wants two kinds of CPP files -- those that just compiled
# and those that are passed via the MOC tool.
#
# This is done with:
#
#    exe main : main.cpp [ cast _ moccable-cpp : widget.cpp ] ;
# 
# Boost.Build will assing target type CPP to both main.cpp and widget.cpp.
# Then, the cast rule will change target type of widget.cpp to
# MOCCABLE-CPP, and Qt support will run MOC tool as part of build process.
#
# At the moment, the 'cast' rule only works for non-derived (source) targets.
#
# Another solution would be to add separate main target 'moc-them' that
# will moc all the passed sources, not matter what's the type, but I prefer
# cast, as defining new target type + generator for that type is somewhat
# simpler then defining main target rule.

import project type targets ;
import "class" : new ;
import errors ;
import property-set ;

class cast-target-class : typed-target
{
    import type ;
    
    rule __init__ ( name : project : type 
    : sources * : requirements * : default-build * : usage-requirements * )
    {
        typed-target.__init__ $(name) : $(project) : $(type)
          : $(sources) : $(requirements) : $(default-build) : $(usage-requirements) ;
    }
       
    rule construct ( name : source-targets * : property-set )
    {
        local result ;
        for local s in $(source-targets)
        {
            if ! [ class.is-a $(s) : file-target ]
            {
                ECHO "error: source to the 'cast' rule is not a file!" ;
                EXIT ;
            }  
            if [ $(s).action ]
            {
                ECHO "error: only non-derived target are allowed for 'cast'." ;
                ECHO "error: when building " [ full-name ] ;
                EXIT ;
            }         
            local r = [ $(s).clone-with-different-type $(self.type) ] ;
            result += [ virtual-target.register $(r) ] ;
        }
                        
        return [ property-set.empty ] $(result) ;
    }            
        
}

rule cast ( name type : sources * : requirements * : default-build * 
    : usage-requirements * )
{
    local project = [ project.current ] ;
    
    local real-type = [ type.type-from-rule-name $(type) ] ;
    if ! $(real-type)
    {
        errors.user-error "No type corresponds to main target rule nam '$(type)'"
          : "Hint: try lowercase name" ;
    }
    
        
    # This is a circular module dependency, so it must be imported here
    import targets ;
    targets.main-target-alternative
      [ new cast-target-class $(name) : $(project) : $(real-type) 
        : [ targets.main-target-sources $(sources) : $(name) ] 
        : [ targets.main-target-requirements $(requirements) : $(project) ] 
        : [ targets.main-target-default-build $(default-build) : $(project) ]
        : [ targets.main-target-usage-requirements $(usage-requirements) : $(project) ]
      ] ;
}
IMPORT $(__name__) : cast : : cast ;