# Copyright 2002, 2003 Dave Abrahams
# Copyright 2002, 2005, 2006 Rene Rivera
# Copyright 2002, 2003, 2004, 2005, 2006 Vladimir Prus
# Distributed under the Boost Software License, Version 1.0.
# (See accompanying file LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt)

# Implements project representation and loading. Each project is represented by:
#  - a module where all the Jamfile content live.
#  - an instance of 'project-attributes' class.
#    (given a module name, can be obtained using the 'attributes' rule)
#  - an instance of 'project-target' class (from targets.jam)
#    (given a module name, can be obtained using the 'target' rule)
#
# Typically, projects are created as result of loading a Jamfile, which is done
# by rules 'load' and 'initialize', below. First, module for Jamfile is loaded
# and new project-attributes instance is created. Some rules necessary for
# project are added to the module (see 'project-rules' module) at the bottom of
# this file. Default project attributes are set (inheriting attributes of parent
# project, if it exists). After that the Jamfile is read. It can declare its own
# attributes using the 'project' rule which will be combined with any already
# set attributes.
#
# The 'project' rule can also declare a project id which will be associated with
# the project module.
#
# There can also be 'standalone' projects. They are created by calling
# 'initialize' on an arbitrary module and not specifying their location. After
# the call, the module can call the 'project' rule, declare main targets and
# behave as a regular project except that, since it is not associated with any
# location, it should not declare targets that are not prebuilt.
#
# The list of all loaded Jamfile is stored in the .project-locations variable.
# It is possible to obtain a module name for a location using the 'module-name'
# rule. Standalone projects are not recorded and can only be referenced using
# their project id.

import "class" : new ;
import errors ;
import modules ;
import path ;
import print ;
import property-set ;
import sequence ;


# Loads the Jamfile at the given location. After loading, project global file
# and Jamfiles needed by the requested one will be loaded recursively. If the
# Jamfile at that location is loaded already, does nothing. Returns the project
# module for the Jamfile.
#
rule load ( jamfile-location )
{
    if --debug-loading in [ modules.peek : ARGV ]
    {
        ECHO "Loading Jamfile at" '$(jamfile-location)' ;
    }

    local module-name = [ module-name $(jamfile-location) ] ;
    # If Jamfile is already loaded, don't try again.
    if ! $(module-name) in $(.jamfile-modules)
    {
        load-jamfile $(jamfile-location) : $(module-name) ;

        # We want to make sure that child project are loaded only after parent
        # projects. In particular, because parent projects define attributes
        # which are inherited by children, and we don't want children to be
        # loaded before parent has defined everything.
        #
        # While "build-project" and "use-project" can potentially refer to child
        # projects from parent projects, we don't immediately load child
        # projects when seeing those attributes. Instead, we record the minimal
        # information to be used only later.
        load-used-projects $(module-name) ;
    }
    return $(module-name) ;
}


rule load-used-projects ( module-name )
{
    local used = [ modules.peek $(module-name) : .used-projects ] ;
    local location = [ attribute $(module-name) location ] ;
    import project ;
    while $(used)
    {
        local id = $(used[1]) ;
        local where = $(used[2]) ;

        project.use $(id) : [ path.root [ path.make $(where) ] $(location) ] ;
        used = $(used[3-]) ;
    }
}


# Note the use of character groups, as opposed to listing 'Jamroot' and
# 'jamroot'. With the latter, we would get duplicate matches on Windows and
# would have to eliminate duplicates.
JAMROOT ?= [ modules.peek : JAMROOT ] ;
JAMROOT ?= project-root.jam [Jj]amroot [Jj]amroot.jam ;


# Loads parent of Jamfile at 'location'. Issues an error if nothing is found.
#
rule load-parent ( location )
{
    local found = [ path.glob-in-parents $(location) : $(JAMROOT) $(JAMFILE) ] ;

    if ! $(found)
    {
        ECHO error: Could not find parent for project at '$(location)' ;
        EXIT error: Did not find Jamfile.jam or Jamroot.jam in any parent
            directory. ;
    }

    return [ load $(found[1]:D) ] ;
}


# Makes the specified 'module' act as if it were a regularly loaded Jamfile at
# 'location'. Reports an error if a Jamfile has already been loaded for that
# location.
#
rule act-as-jamfile ( module : location )
{
    if [ module-name $(location) ] in $(.jamfile-modules)
    {
        errors.error "Jamfile was already loaded for '$(location)'" ;
    }
    # Set up non-default mapping from location to module.
    .module.$(location) = $(module) ;

    # Add the location to the list of project locations so that we don't try to
    # reload the same Jamfile in the future.
    .jamfile-modules += [ module-name $(location) ] ;

    initialize $(module) : $(location) ;
}


# Returns the project module corresponding to the given project-id or plain
# directory name. Returns nothing if such a project can not be found.
#
rule find ( name : current-location )
{
    local project-module ;

    # Try interpreting name as project id.
    if [ path.is-rooted $(name) ]
    {
        project-module = $($(name).jamfile-module) ;
    }

    if ! $(project-module)
    {
        local location = [ path.root [ path.make $(name) ] $(current-location) ]
            ;

        # If no project is registered for the given location, try to load it.
        # First see if we have a Jamfile. If not, then see if we might have a
        # project root willing to act as a Jamfile. In that case, project root
        # must be placed in the directory referred by id.

        project-module = [ module-name $(location) ] ;
        if ! $(project-module) in $(.jamfile-modules)
        {
            if [ path.glob $(location) : $(JAMROOT) $(JAMFILE) ]
            {
                project-module = [ load $(location) ] ;
            }
            else
            {
                project-module = ;
            }
        }
    }

    return $(project-module) ;
}


# Returns the name of the module corresponding to 'jamfile-location'. If no
# module corresponds to that location yet, associates the default module name
# with that location.
#
rule module-name ( jamfile-location )
{
    if ! $(.module.$(jamfile-location))
    {
        # Root the path, so that locations are always unambiguous. Without this,
        # we can't decide if '../../exe/program1' and '.' are the same paths.
        jamfile-location = [ path.root $(jamfile-location) [ path.pwd ] ] ;
        .module.$(jamfile-location) = Jamfile<$(jamfile-location)> ;
    }
    return $(.module.$(jamfile-location)) ;
}


# Default patterns to search for the Jamfiles to use for build declarations.
#
JAMFILE = [ modules.peek : JAMFILE ] ;
JAMFILE ?= [Bb]uild.jam [Jj]amfile.v2 [Jj]amfile [Jj]amfile.jam ;


# Find the Jamfile at the given location. This returns the exact names of all
# the Jamfiles in the given directory. The optional parent-root argument causes
# this to search not the given directory but the ones above it up to the
# directory given in it.
#
rule find-jamfile (
    dir # The directory(s) to look for a Jamfile.
    parent-root ? # Optional flag indicating to search for the parent Jamfile.
    : no-errors ?
    )
{
    # Glob for all the possible Jamfiles according to the match pattern.
    #
    local jamfile-glob = ;
    if $(parent-root)
    {
        if ! $(.parent-jamfile.$(dir))
        {
            .parent-jamfile.$(dir) = [ path.glob-in-parents $(dir) : $(JAMFILE)
                ] ;
        }
        jamfile-glob = $(.parent-jamfile.$(dir)) ;
    }
    else
    {
        if ! $(.jamfile.$(dir))
        {
            .jamfile.$(dir) = [ path.glob $(dir) : $(JAMFILE) ] ;
        }
        jamfile-glob = $(.jamfile.$(dir)) ;

    }

    local jamfile-to-load = $(jamfile-glob) ;
    # Multiple Jamfiles found in the same place. Warn about this and ensure we
    # use only one of them. As a temporary convenience measure, if there is
    # Jamfile.v2 among found files, suppress the warning and use it.
    #
    if $(jamfile-to-load[2-])
    {
        local v2-jamfiles = [ MATCH (.*[Jj]amfile\\.v2)|(.*[Bb]uild\\.jam) : $(jamfile-to-load) ] ;

        if $(v2-jamfiles) && ! $(v2-jamfiles[2])
        {
            jamfile-to-load = $(v2-jamfiles) ;
        }
        else
        {
            local jamfile = [ path.basename $(jamfile-to-load[1]) ] ;
            ECHO "warning: Found multiple Jamfiles at '"$(dir)"'!"
                "Loading the first one: '$(jamfile)'." ;
        }

        jamfile-to-load = $(jamfile-to-load[1]) ;
    }

    # Could not find it, error.
    #
    if ! $(no-errors) && ! $(jamfile-to-load)
    {
        errors.error Unable to load Jamfile.
            : Could not find a Jamfile in directory '$(dir)'.
            : Attempted to find it with pattern '"$(JAMFILE:J=" ")"'.
            : Please consult the documentation at 'http://www.boost.org'. ;
    }

    return $(jamfile-to-load) ;
}


# Load a Jamfile at the given directory. Returns nothing. Will attempt to load
# the file as indicated by the JAMFILE patterns. Effect of calling this rule
# twice with the same 'dir' is undefined.
#
local rule load-jamfile (
    dir  # The directory of the project Jamfile.
    : jamfile-module
    )
{
    # See if the Jamfile is where it should be.
    #
    local jamfile-to-load = [ path.glob $(dir) : $(JAMROOT) ] ;
    if ! $(jamfile-to-load)
    {
        jamfile-to-load = [ find-jamfile $(dir) ] ;
    }
    
    if $(jamfile-to-load[2])
    {
        errors.error "Multiple Jamfiles found at '$(dir)'" 
          :  "Filenames are: " $(jamfile-to-load:D=) ;
    }
    
    # Now load the Jamfile in it's own context. 
    # The call to 'initialize' may load parent Jamfile, which might have
    # 'use-project' statement that causes a second attempt to load the
    # same project we're loading now.  Checking inside .jamfile-modules
    # prevents that second attempt from messing up.
    if ! $(jamfile-module) in $(.jamfile-modules)
    {
        .jamfile-modules += $(jamfile-module) ;

        # Initialize the Jamfile module before loading.
        #
        initialize $(jamfile-module) : [ path.parent $(jamfile-to-load) ]
            : $(jamfile-to-load:BS) ;

        local saved-project = $(.current-project) ;

        mark-as-user $(jamfile-module) ;
        modules.load $(jamfile-module) : [ path.native $(jamfile-to-load) ] : . ;
        if [ MATCH ($(JAMROOT)) : $(jamfile-to-load:BS) ]
        {
            jamfile = [ find-jamfile $(dir) : no-errors ] ;
            if $(jamfile)
            {
                load-aux $(jamfile-module) : [ path.native $(jamfile) ] ;
            }
        }

    # Now do some checks.
    if $(.current-project) != $(saved-project)
    {
        errors.error "The value of the .current-project variable has magically"
            : "changed after loading a Jamfile. This means some of the targets"
            : "might be defined in the wrong project."
            : "after loading" $(jamfile-module)
            : "expected value" $(saved-project)
            : "actual value" $(.current-project) ;
    }

    if $(.global-build-dir)
    {
        local id           = [ attribute $(jamfile-module) id           ] ;
        local project-root = [ attribute $(jamfile-module) project-root ] ;
        local location     = [ attribute $(jamfile-module) location     ] ;

        if $(location) && $(project-root) = $(dir)
        {
            # This is Jamroot.
            if ! $(id)
            {
                ECHO "warning: the --build-dir option was specified" ;
                ECHO "warning: but Jamroot at '$(dir)'" ;
                ECHO "warning: specified no project id" ;
                ECHO "warning: the --build-dir option will be ignored" ;
            }
        }
    }
    }
}


rule mark-as-user ( module-name )
{
    if USER_MODULE in [ RULENAMES ]
    {
        USER_MODULE $(module-name) ;
    }
}


rule load-aux ( module-name : file )
{
    mark-as-user $(module-name) ;

    module $(module-name)
    {
        include $(2) ;
        local rules = [ RULENAMES $(1) ] ;
        IMPORT $(1) : $(rules) : $(1) : $(1).$(rules) ;
    }
}


.global-build-dir = [ MATCH --build-dir=(.*) : [ modules.peek : ARGV ] ] ;
if $(.global-build-dir)
{
    # If the option is specified several times, take the last value.
    .global-build-dir = [ path.make $(.global-build-dir[-1]) ] ;
}


# Initialize the module for a project.
#
rule initialize (
    module-name   # The name of the project module.
    : location ?  # The location (directory) of the project to initialize. If
                  # not specified, a standalone project will be initialized.
    : basename ?
    )
{
    if --debug-loading in [ modules.peek : ARGV ]
    {
        ECHO "Initializing project '$(module-name)'" ;
    }

    # TODO: need to consider if standalone projects can do anything but define
    # prebuilt targets. If so, we need to give it a more sensible "location", so
    # that source paths are correct.
    location ?= "" ;
    # Create the module for the Jamfile first.
    module $(module-name)
    {
    }
    $(module-name).attributes = [ new project-attributes $(location)
        $(module-name) ] ;
    local attributes = $($(module-name).attributes) ;

    if $(location)
    {
        $(attributes).set source-location : [ path.make $(location) ] : exact ;
    }
    else if ! $(module-name) in test-config site-config user-config project-config
    {
        # This is a standalone project with known location. Set source location
        # so that it can declare targets. This is intended so that you can put
        # a .jam file in your sources and use it via 'using'. Standard modules
        # (in 'tools' subdir) may not assume source dir is set.
        local s = [ modules.binding $(module-name) ] ;
        if ! $(s)
        {
            errors.error "Could not determine project location $(module-name)" ;
        }        
        $(attributes).set source-location : $(s:D) : exact ;
    }

    $(attributes).set requirements       : [ property-set.empty ] : exact ;
    $(attributes).set usage-requirements : [ property-set.empty ] : exact ;

    # Import rules common to all project modules from project-rules module,
    # defined at the end of this file.
    local rules = [ RULENAMES project-rules ] ;
    IMPORT project-rules : $(rules) : $(module-name) : $(rules) ;

    local jamroot ;

    local parent-module ;
    if $(module-name) = test-config
    {
        # No parent.
    }
    else if $(module-name) = site-config
    {
        parent-module = test-config ;
    }
    else if $(module-name) = user-config
    {
        parent-module = site-config ;
    }
    else if $(module-name) = project-config
    {
        parent-module = user-config ;
    }    
    else
    {
        # We search for parent/project-root only if Jamfile was specified, i.e.
        # if the project is not standalone.
        if $(location) && ! [ MATCH ($(JAMROOT)) : $(basename) ]
        {
            parent-module = [ load-parent $(location) ] ;
        }
        else
        {
            # It's either jamroot or standalone project. If it's jamroot,
            # inherit from user-config.
            if $(location)
            {
                # If project-config module exist, inherit from it.
                if $(project-config.attributes)
                {   
                    parent-module = project-config ;
                }
                else
                {                    
                    parent-module = user-config ;
                }                
                jamroot = true ;
            }
        }
    }

    if $(parent-module)
    {
        inherit-attributes $(module-name) : $(parent-module) ;
        $(attributes).set parent-module : $(parent-module) : exact ;
    }

    if $(jamroot)
    {
        $(attributes).set project-root : $(location) : exact ;
    }

    local parent ;
    if $(parent-module)
    {
        parent = [ target $(parent-module) ] ;
    }

    if ! $(.target.$(module-name))
    {
        .target.$(module-name) = [ new project-target $(module-name)
            : $(module-name) $(parent)
            : [ attribute $(module-name) requirements ] ] ;

        if --debug-loading in [ modules.peek : ARGV ]
        {
            ECHO "Assigned project target" $(.target.$(module-name))
                "to '$(module-name)'" ;
        }
    }

    .current-project = [ target $(module-name) ] ;
}


# Make 'project-module' inherit attributes of project root and parent module.
#
rule inherit-attributes ( project-module : parent-module )
{
    local attributes = $($(project-module).attributes) ;
    local pattributes = [ attributes $(parent-module) ] ;
    # Parent module might be locationless configuration module.
    if [ modules.binding $(parent-module) ]
    {
        $(attributes).set parent : [ path.parent
            [ path.make [ modules.binding $(parent-module) ] ] ] ;
    }
    local v = [ $(pattributes).get project-root ] ;
    $(attributes).set project-root : $(v) : exact ;
    $(attributes).set default-build
        : [ $(pattributes).get default-build ] ;
    $(attributes).set requirements
        : [ $(pattributes).get requirements ] : exact ;
    $(attributes).set usage-requirements
        : [ $(pattributes).get usage-requirements ] : exact ;

    local parent-build-dir = [ $(pattributes).get build-dir ] ;
    if $(parent-build-dir)
    {
        # Have to compute relative path from parent dir to our dir. Convert both
        # paths to absolute, since we cannot find relative path from ".." to
        # ".".

        local location = [ attribute $(project-module) location ] ;
        local parent-location = [ attribute $(parent-module) location ] ;

        local pwd = [ path.pwd ] ;
        local parent-dir = [ path.root $(parent-location) $(pwd) ] ;
        local our-dir = [ path.root $(location) $(pwd) ] ;
        $(attributes).set build-dir : [ path.join $(parent-build-dir)
            [ path.relative $(our-dir) $(parent-dir) ] ] : exact ;
    }
}


# Associate the given id with the given project module.
#
rule register-id ( id : module )
{
    $(id).jamfile-module = $(module) ;
}


# Class keeping all the attributes of a project.
#
# The standard attributes are "id", "location", "project-root", "parent"
# "requirements", "default-build", "source-location" and "projects-to-build".
#
class project-attributes
{
    import property ;
    import property-set ;
    import errors ;
    import path ;
    import print ;
    import sequence ;
    import project ;

    rule __init__ ( location project-module )
    {
        self.location = $(location) ;
        self.project-module = $(project-module) ;
    }

    # Set the named attribute from the specification given by the user. The
    # value actually set may be different.
    #
    rule set ( attribute : specification *
        : exact ?  # Sets value from 'specification' without any processing.
        )
    {
        if $(exact)
        {
            self.$(attribute) = $(specification) ;
        }
        else if $(attribute) = "requirements"
        {
            local result = [ property-set.refine-from-user-input
                $(self.requirements) : $(specification)
                : $(self.project-module) : $(self.location) ] ;

            if $(result[1]) = "@error"
            {
                errors.error Requirements for project at '$(self.location)'
                    conflict with parent's. : Explanation: $(result[2-]) ;
            }
            else
            {
                self.requirements = $(result) ;
            }
        }
        else if $(attribute) = "usage-requirements"
        {
            local unconditional ;
            for local p in $(specification)
            {
                local split = [ property.split-conditional $(p) ] ;
                split ?= nothing $(p) ;
                unconditional += $(split[2]) ;
            }

            local non-free = [ property.remove free : $(unconditional) ] ;
            if $(non-free)
            {
                errors.error usage-requirements $(specification) have non-free
                    properties $(non-free) ;
            }
            local t = [ property.translate-paths $(specification)
                                      : $(self.location) ] ;
            if $(self.usage-requirements)
            {
                self.usage-requirements = [ property-set.create
                    [ $(self.usage-requirements).raw ] $(t) ] ;
            }
            else
            {
                self.usage-requirements = [ property-set.create $(t) ] ;
            }
        }
        else if $(attribute) = "default-build"
        {
            self.default-build = [ property.make $(specification) ] ;
        }
        else if $(attribute) = "source-location"
        {
            self.source-location = ;
            for local src-path in $(specification)
            {
                self.source-location += [ path.root [ path.make $(src-path) ]
                    $(self.location) ] ;
            }
        }
        else if $(attribute) = "build-dir"
        {
            self.build-dir = [ path.root
                [ path.make $(specification) ] $(self.location) ] ;
        }
        else if $(attribute) = "id"
        {
            id = [ path.root $(specification) / ] ;
            project.register-id $(id) : $(self.project-module) ;
            self.id = $(id) ;
        }
        else if ! $(attribute) in "default-build" "location" "parent"
            "projects-to-build" "project-root" "source-location"
        {
            errors.error Invalid project attribute '$(attribute)' specified for
                project at '$(self.location)' ;
        }
        else
        {
            self.$(attribute) = $(specification) ;
        }
    }

    # Returns the value of the given attribute.
    #
    rule get ( attribute )
    {
        return $(self.$(attribute)) ;
    }

    # Prints the project attributes.
    #
    rule print ( )
    {
        local id = $(self.id) ; id ?= (none) ;
        local parent = $(self.parent) ; parent ?= (none) ;
        print.section "'"$(id)"'" ;
        print.list-start ;
        print.list-item "Parent project:" $(parent) ;
        print.list-item "Requirements:" [ $(self.requirements).raw ] ;
        print.list-item "Default build:" $(self.default-build) ;
        print.list-item "Source location:" $(self.source-location) ;
        print.list-item "Projects to build:"
                        [ sequence.insertion-sort $(self.projects-to-build) ] ;
        print.list-end ;
    }
}


# Returns the project which is currently being loaded.
#
rule current ( )
{
    return $(.current-project) ;
}


# Temporarily changes the current project to 'project'. Should be followed by
# 'pop-current'.
#
rule push-current ( project )
{
    .saved-current-project += $(.current-project) ;
    .current-project = $(project) ;
}


rule pop-current ( )
{
    .current-project = $(.saved-current-project[-1]) ;
    .saved-current-project = $(.saved-current-project[1--2]) ;
}


# Returns the project-attribute instance for the specified Jamfile module.
#
rule attributes ( project )
{
    return $($(project).attributes) ;
}


# Returns the value of the specified attribute in the specified Jamfile module.
#
rule attribute ( project attribute )
{
    return [ $($(project).attributes).get $(attribute) ] ;
}


# Returns the project target corresponding to the 'project-module'.
#
rule target ( project-module )
{
    if ! $(.target.$(project-module))
    {
        .target.$(project-module) = [ new project-target $(project-module)
            : $(project-module)
            : [ attribute $(project-module) requirements ] ] ;
    }
    return $(.target.$(project-module)) ;
}


# Use/load a project.
#
rule use ( id : location )
{
    local saved-project = $(.current-project) ;
    local project-module = [ project.load $(location) ] ;
    local declared-id = [ project.attribute $(project-module) id ] ;

    if ! $(declared-id) || $(declared-id) != $(id)
    {
        # The project at 'location' either has no id or that id is not equal to
        # the 'id' parameter.
        if $($(id).jamfile-module) && ( $($(id).jamfile-module) !=
            $(project-module) )
        {
            errors.user-error Attempt to redeclare already existing project id
                '$(id)' 
                location '$(location)' ;
        }
        $(id).jamfile-module = $(project-module) ;
    }
    .current-project = $(saved-project) ;
}


# Defines a Boost.Build extension project. Such extensions usually contain
# library targets and features that can be used by many people. Even though
# extensions are really projects, they can be initialized as a module would be
# with the "using" (project.project-rules.using) mechanism.
#
rule extension ( id : options * : * )
{
    # The caller is a standalone module for the extension.
    local mod = [ CALLER_MODULE ] ;

    # We need to do the rest within the extension module.
    module $(mod)
    {
        import path ;

        # Find the root project.
        local root-project = [ project.current ] ;
        root-project = [ $(root-project).project-module ] ;
        while
            [ project.attribute $(root-project) parent-module ] &&
            [ project.attribute $(root-project) parent-module ] != user-config
        {
            root-project = [ project.attribute $(root-project) parent-module ] ;
        }

        # Create the project data, and bring in the project rules into the
        # module.
        project.initialize $(__name__) : [ path.join [ project.attribute
            $(root-project) location ] ext $(1:L) ] ;

        # Create the project itself, i.e. the attributes. All extensions are
        # created in the "/ext" project space.
        project /ext/$(1) : $(2) : $(3) : $(4) : $(5) : $(6) : $(7) : $(8) :
            $(9) ;
        local attributes = [ project.attributes $(__name__) ] ;

        # Inherit from the root project of whomever is defining us.
        project.inherit-attributes $(__name__) : $(root-project) ;
        $(attributes).set parent-module : $(root-project) : exact ;
    }
}


rule glob-internal ( project : wildcards + : excludes * : rule-name )
{
    local location = [ $(project).get source-location ] ;

    local result ;
    local paths = [ path.$(rule-name) $(location) :
        [ sequence.transform path.make : $(wildcards) ] :
        [ sequence.transform path.make : $(excludes) ] ] ;
    if $(wildcards:D) || $(rule-name) != glob
    {
        # The paths we have found are relative to the current directory, but the
        # names specified in the sources list are assumed to be relative to the
        # source directory of the corresponding project. So, just make the names
        # absolute.
        for local p in $(paths)
        {
            # If the path is below source location, use relative path.
            # Otherwise, use full path just to avoid any ambiguities.
            local rel = [ path.relative $(p) $(location) : no-error ] ;
            if $(rel) = not-a-child
            {                   
                result += [ path.root $(p) [ path.pwd ] ] ;
            }
            else
            {
                result += $(rel) ;
            }                
        }
    }
    else
    {
        # There were no wildcards in the directory path, so the files are all in
        # the source directory of the project. Just drop the directory, instead
        # of making paths absolute.
        result = $(paths:D="") ;
    }

    return $(result) ;
}


# This module defines rules common to all projects.
#
module project-rules
{
    rule using ( toolset-module : * )
    {
        import toolset ;
        import modules ;
        import project ;

        # Temporarily change the search path so the module referred to by
        # 'using' can be placed in the same directory as Jamfile. User will
        # expect the module to be found even though the directory is not in
        # BOOST_BUILD_PATH.
        local x = [ modules.peek : BOOST_BUILD_PATH ] ;
        local caller = [ CALLER_MODULE ] ;
        local caller-location = [ modules.binding $(caller) ] ;
        modules.poke : BOOST_BUILD_PATH : $(caller-location:D) $(x) ;
        toolset.using $(1) : $(2) : $(3) : $(4) : $(5) : $(6) : $(7) : $(8) : $(9) ;
        modules.poke : BOOST_BUILD_PATH : $(x) ;

        # The above might have clobbered .current-project. Restore the correct
        # value.
        modules.poke project : .current-project
            : [ project.target $(caller) ] ;
    }

    import modules ;

    rule import ( * : * : * )
    {
        modules.import project ;

        local caller = [ CALLER_MODULE ] ;
        local saved = [ modules.peek project : .current-project ] ;
        module $(caller)
        {
            modules.import $(1) : $(2) : $(3) ;
        }
        modules.poke project : .current-project : $(saved) ;
    }

    rule project ( id ? : options * : * )
    {
        import errors ;
        import path ;
        import project ;

        local caller = [ CALLER_MODULE ] ;
        local attributes = [ project.attributes $(caller) ] ;
        if $(id)
        {
           $(attributes).set id : $(id) ;
        }

        local explicit-build-dir ;

        for n in 2 3 4 5 6 7 8 9
        {
            local option = $($(n)) ;
            if $(option)
            {
                $(attributes).set $(option[1]) : $(option[2-]) ;
            }
            if $(option[1]) = "build-dir"
            {
                explicit-build-dir = [ path.make $(option[2-]) ] ;
            }
        }

        # If '--build-dir' is specified, change the build dir for the project.
        local global-build-dir =
            [ modules.peek project : .global-build-dir ] ;

        if $(global-build-dir)
        {
            local location = [ $(attributes).get location ] ;
            # Project with an empty location is a 'standalone' project such as
            # user-config or qt. It has no build dir. If we try to set build dir
            # for user-config, we shall then try to inherit it, with either
            # weird or wrong consequences.
            if $(location) && $(location) = [ $(attributes).get project-root ]
            {
                # Re-read the project id, since it might have been changed in
                # the project's attributes.
                id = [ $(attributes).get id ] ;
                # This is Jamroot.
                if $(id)
                {
                    if $(explicit-build-dir) &&
                        [ path.is-rooted $(explicit-build-dir) ]
                    {
                        errors.user-error Absolute directory specified via
                            'build-dir' project attribute : Do not know how to
                            combine that with the --build-dir option. ;
                    }
                    # Strip the leading slash from id.
                    local rid = [ MATCH /(.*) : $(id) ] ;
                    local p = [ path.join
                        $(global-build-dir) $(rid) $(explicit-build-dir) ] ;

                    $(attributes).set build-dir : $(p) : exact ;
                }
            }
            else
            {
                # Not Jamroot.
                if $(explicit-build-dir)
                {
                    errors.user-error When --build-dir is specified, the
                        'build-dir' project : attribute is allowed only for
                        top-level 'project' invocations ;
                }
            }
        }
    }

    # Declare and set a project global constant. Project global constants are
    # normal variables but should not be changed. They are applied to every
    # child Jamfile.
    #
    rule constant (
        name  # Variable name of the constant.
        : value +  # Value of the constant.
    )
    {
        import project ;
        local caller = [ CALLER_MODULE ] ;
        local p = [ project.target $(caller) ] ;
        $(p).add-constant $(name) : $(value) ;
    }

    # Declare and set a project global constant, whose value is a path. The path
    # is adjusted to be relative to the invocation directory. The given value
    # path is taken to be either absolute, or relative to this project root.
    #
    rule path-constant (
        name  # Variable name of the constant.
        : value +  # Value of the constant.
        )
    {
        import project ;
        local caller = [ CALLER_MODULE ] ;
        local p = [ project.target $(caller) ] ;
        $(p).add-constant $(name) : $(value) : path ;
    }

    rule use-project ( id : where )
    {
        import modules ;
        # See comment in 'load' for explanation.
        local caller = [ CALLER_MODULE ] ;
        modules.poke $(caller) : .used-projects :
            [ modules.peek $(caller) : .used-projects ]
            $(id) $(where) ;
    }

    rule build-project ( dir )
    {
        import project ;
        local caller = [ CALLER_MODULE ] ;
        local attributes = [ project.attributes $(caller) ] ;

        local now = [ $(attributes).get projects-to-build ] ;
        $(attributes).set projects-to-build : $(now) $(dir) ;
    }

    rule explicit ( target-names * )
    {
        import project ;
        # If 'explicit' is used in a helper rule defined in Jamroot and
        # inherited by children, then most of the time we want 'explicit' to
        # operate on the Jamfile where the helper rule is invoked.
        local t = [ project.current ] ;
        for local n in $(target-names)
        {
            $(t).mark-target-as-explicit $(n) ;
        }
    }

    rule always ( target-names * )
    {
        import project ;
        local t = [ project.current ] ;
        for local n in $(target-names)
        {
            $(t).mark-target-as-always $(n) ;
        }        
    }
    
    rule glob ( wildcards + : excludes * )
    {
        import project ;
        return [ project.glob-internal [ project.current ] : $(wildcards) :
            $(excludes) : glob ] ;
    }

    rule glob-tree ( wildcards + : excludes * )
    {
        import project ;

        if $(wildcards:D) || $(excludes:D)
        {
            errors.user-error The patterns to 'glob-tree' may not include
                directory ;
        }
        return [ project.glob-internal [ project.current ] : $(wildcards) :
            $(excludes) : glob-tree ] ;
    }

    # Calculates conditional requirements for multiple requirements at once.
    # This is a shorthand to reduce duplication and to keep an inline
    # declarative syntax. For example:
    #
    #   lib x : x.cpp : [ conditional <toolset>gcc <variant>debug :
    #       <define>DEBUG_EXCEPTION <define>DEBUG_TRACE ] ;
    #
    rule conditional ( condition + : requirements * )
    {
        local condition = $(condition:J=,) ;
        if [ MATCH (:) : $(condition) ]
        {
            return $(condition)$(requirements) ;
        }
        else
        {
            return $(condition):$(requirements) ;
        }
    }
    
    rule option ( name : value )
    {
        if $(__name__) != site-config && $(__name__) != user-config && $(__name__) != project-config
        {
            import errors ;
            errors.error "The 'option' rule may be used only in site-config or user-config" ;
        }        
        import option ;
        option.set $(name) : $(value) ;
    }    
}