# Licensed to the Apache Software Foundation (ASF) under one or more
# contributor license agreements.  See the NOTICE file distributed with this
# work for additional information regarding copyright ownership.  The ASF
# licenses this file to you under the Apache License, Version 2.0 (the
# "License"); you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
# License for the specific language governing permissions and limitations under
# the License.


require 'java'
require 'jruby'


# Buildr runs along side a JVM, using either RJB or JRuby.  The Java module allows
# you to access Java classes and create Java objects.
#
# Java classes are accessed as static methods on the Java module, for example:
#   str = Java.java.lang.String.new('hai!')
#   str.toUpperCase
#   => 'HAI!'
#   Java.java.lang.String.isInstance(str)
#   => true
#   Java.com.sun.tools.javac.Main.compile(args)
#
# The classpath attribute allows Buildr to add JARs and directories to the classpath,
# for example, we use it to load Ant and various Ant tasks, code generators, test
# frameworks, and so forth.
#
# When using an artifact specification, Buildr will automatically download and
# install the artifact before adding it to the classpath.
#
# For example, Ant is loaded as follows:
#   Java.classpath << 'org.apache.ant:ant:jar:1.7.0'
#
# Artifacts can only be downloaded after the Buildfile has loaded, giving it
# a chance to specify which remote repositories to use, so adding to classpath
# does not by itself load any libraries.  You must call Java.load before accessing
# any Java classes to give Buildr a chance to load the libraries specified in the
# classpath.
#
# When building an extension, make sure to follow these rules:
# 1. Add to the classpath when the extension is loaded (i.e. in module or class
#    definition), so the first call to Java.load anywhere in the code will include
#    the libraries you specify.
# 2. Call Java.load once before accessing any Java classes, allowing Buildr to
#    set up the classpath.
# 3. Only call Java.load when invoked, otherwise you may end up loading the JVM
#    with a partial classpath, or before all remote repositories are listed.
# 4. Check on a clean build with empty local repository.
module Java

  class << self

    # Returns the classpath, an array listing directories, JAR files and
    # artifacts.  Use when loading the extension to add any additional
    # libraries used by that extension.
    #
    # For example, Ant is loaded as follows:
    #   Java.classpath << 'org.apache.ant:ant:jar:1.7.0'
    def classpath
      @classpath ||= []
    end

    # Loads the JVM and all the libraries listed on the classpath.  Call this
    # method before accessing any Java class, but only call it from methods
    # used in the build, giving the Buildfile a chance to load all extensions
    # that append to the classpath and specify which remote repositories to use.
    def load
      return self if @loaded
      cp = Buildr.artifacts(classpath).map(&:to_s).each { |path| file(path).invoke }
      #cp ||= java.lang.System.getProperty('java.class.path').split(':').compact
      # Use system ClassLoader to add classpath.
      sysloader = java.lang.ClassLoader.getSystemClassLoader
      add_url_method = java.lang.Class.forName('java.net.URLClassLoader').
        getDeclaredMethod('addURL', [java.net.URL].to_java(java.lang.Class))
      add_url_method.setAccessible(true)
      add_path = lambda { |path| add_url_method.invoke(sysloader, [java.io.File.new(path).toURI.toURL].to_java(java.net.URL)) }
      # Include tools (compiler, Javadoc, etc) for all platforms except OS/X.
      unless Config::CONFIG['host_os'] =~ /darwin/i
        home = ENV['JAVA_HOME'] or fail 'Are we forgetting something? JAVA_HOME not set.'
        tools = File.expand_path('lib/tools.jar', home)
        raise "Missing #{tools}, perhaps your JAVA_HOME is not correclty set" unless File.file?(tools)
        add_path[tools]
      end
      cp.each { |path| add_path[path] }
      @loaded = true
      self
    end

  end

end