require 'requirement'

# We support Python 2.x and 3.x, either brewed or external.
# This requirement locates the correct CPython binary (no PyPy), provides
# support methods like `site_packages`, and writes our sitecustomize.py file.
# In `dependency_collector.rb`, special `:python` and `:python3` shortcuts are
# defined. You can specify a minimum version of the Python that needs to be
# present, but since not every package is ported to 3.x yet,
# `PythonInstalled("2")` is not satisfied by 3.x.
# In a formula that shall provide support for 2.x and 3.x, the idiom is:
# depends_on :python
# depends_on :python3 => :optional # or :recommended
#
# Todo:
# - Allow further options that choose: universal, framework?, brewed?...
class PythonInstalled < Requirement
  attr_reader :min_version
  attr_reader :if3then3
  attr_reader :site_packages
  attr_accessor :site_packages

  fatal true  # you can still make Python optional by `depends_on :python => :optional`

  class PythonVersion < Version
    def major
      to_a[0].to_s.to_i  # Python's major.minor are always ints.
    end
    def minor
      to_a[1].to_s.to_i
    end
  end

  def initialize(*tags)
    # Extract the min_version if given. Default to python 2.X else
    tags.flatten!
    if /(\d+\.)*\d+/ === tags.first
      @min_version = PythonVersion.new(tags.shift)
    else
      @min_version = PythonVersion.new("2.6")  # default
    end

    # often used idiom: e.g. sipdir = "share/sip" + python.if3then3
    if @min_version.major == 3
      @if3then3 = "3"
    else
      @if3then3 = ""
    end

    # Set name according to the major version.
    # The name is used to generate the options like --without-python3
    @name = "python" + @if3then3

    # will be set later by the python_helper, because it needs the
    # formula prefix to set site_packages
    @site_packages = nil

    super tags
  end

  # Note that during `satisfy` we still have the PATH as the user has set.
  # We look for a brewed python or an external Python and store the loc of
  # that binary for later usage. (See Formula#python)
  satisfy :build_env => false do
    @unsatisfied_because = "This formula needs #{@name}.\n"
    if binary.nil?
      @unsatisfied_because += "But no `#{@name}` found in your PATH! Consider to `brew install #{@name}`."
      false
    elsif pypy?
      @unsatisfied_because += "Your #{@name} executable appears to be a PyPy, which is not supported."
      false
    elsif version.major != @min_version.major
      @unsatisfied_because += "No Python #{@min_version.major}.x found!"
      false
    elsif version < @min_version
      @unsatisfied_because += "Python version #{version} is too old (need at least #{@min_version})."
      false
    elsif @min_version.major == 2 && `python -c "import sys; print(sys.version_info.major)"`.strip == "3"
      @unsatisfied_because += "Your `python` points to a Python 3.x. This is not supported."
      false
    else
      true
    end
  end

  # The full path to the python or python3 executable, depending on `version`.
  def binary
    if brewed?
      # If the python is brewed we always prefer it!
      # Note, we don't support homebrew/versions/pythonXX.rb, though.
      Formula.factory(@name).opt_prefix/"bin/python#{@min_version.major}"
    else
      p = which(@name)
      raise "PythonInstalled: #{p} is not executable" if !p.nil? && !p.executable?
      p
    end
  end

  # The python prefix (special cased for a brewed python to point into the opt_prefix)
  def prefix
    if brewed?
      # Homebrew since a long while only supports frameworked python
      HOMEBREW_PREFIX/"opt/#{name}/Frameworks/Python.framework/Versions/#{version.major}.#{version.minor}"
    elsif from_osx?
      # Python on OS X has been stripped off its includes (unless you install the CLT), therefore we use the MacOS.sdk.
      Pathname.new("#{MacOS.sdk_path}/System/Library/Frameworks/Python.framework/Versions/#{version.major}.#{version.minor}")
    else
      # What Python knows about itself
      Pathname.new(`#{binary} -c 'import sys;print(sys.prefix)'`.strip)
    end
  end

  # Get the actual x.y.z version by asking python (or python3 if @min_version>=3)
  def version
    @version ||= PythonVersion.new(`#{binary} -c 'import sys;print(sys.version[:5])'`.strip)
  end

  # python.xy => "python2.7" is often used (and many formulae had this as `which_python`).
  def xy
    "python#{version.major}.#{version.minor}"
  end

  # Homebrew's global site-packages. The local ones are populated by the
  # python_helper method when the `prefix` of a formula is known.
  def global_site_packages
    HOMEBREW_PREFIX/"lib/#{xy}/site-packages"
  end

  # Dir containing Python.h and others.
  def incdir
    if (from_osx? || brewed?) && framework?
      prefix/"Headers"
    else
      # For all other we use Python's own standard method (works with a non-framework version, too)
      Pathname.new(`#{binary} -c 'from distutils import sysconfig; print(sysconfig.get_python_inc())'`.strip)
    end
  end

  # Dir containing e.g. libpython2.7.dylib
  def libdir
    if brewed? || from_osx?
      prefix/"lib/#{xy}/config"
    else
      Pathname.new(`#{binary} -c "from distutils import sysconfig; print(sysconfig.get_config_var('LIBPL'))"`.strip)
    end
  end

  # Pkgconfig (pc) files of python
  def pkg_config_path
    if from_osx?
      # No matter if CLT-only or Xcode-only, the pc file is always here on OS X:
      path = Pathname.new("/System/Library/Frameworks/Python.framework/Versions/#{version.major}.#{version.minor}/lib/pkgconfig")
      path if path.exist?
    else
      prefix/"lib/pkgconfig"
    end
  end

  # Is the Python brewed (and linked)?
  def brewed?
    @brewed ||= begin
      require 'formula'
      f = Formula.factory(@name)
      f.installed? && f.linked_keg.exist?
    end
  end

  # Is the python the one from OS X?
  def from_osx?
    @from_osx ||= begin
      p = `#{binary} -c "import sys; print(sys.prefix)"`.strip
      p.start_with?("/System/Library/Frameworks/Python.framework")
    end
  end

  # Is the `python` a PyPy?
  def pypy?
    @pypy ||= !(`#{binary} -c "import sys; print(sys.version)"`.downcase =~ /.*pypy.*/).nil?
  end

  # Is this python a framework-style install (OS X only)?
  def framework?
    @framework ||= /Python[0-9]*\.framework/ === prefix.to_s
  end

  def universal?
    @universal ||= archs_for_command(binary).universal?
  end

  def standard_caveats
    if brewed?
      ""  # empty string, so we can concat this
    else
      <<-EOS.undent
        For non-homebrew #{@name} (#{@min_version.major}.x), you need to amend your PYTHONPATH like so:
          export PYTHONPATH=#{global_site_packages}:$PYTHONPATH
      EOS
    end
  end

  def modify_build_environment
    # Write our sitecustomize.py
    file = global_site_packages/"sitecustomize.py"
    ohai "Writing #{file}" if ARGV.verbose? || ARGV.homebrew_developer?
    [".pyc", ".pyo", ".py"].map{ |f|
      global_site_packages/"sitecustomize#{f}"
    }.each{ |f| f.delete if f.exist? }
    file.write(sitecustomize)

    # For non-system python's we add the opt_prefix/bin of python to the path.
    ENV.prepend 'PATH', binary.dirname, ':' unless from_osx?

    ENV['PYTHONHOME'] = nil  # to avoid fuck-ups.
    ENV['PYTHONNOUSERSITE'] = '1'
    # Python respects the ARCHFLAGS var if set. Shall we set them here?
    # ENV['ARCHFLAGS'] = ??? # FIXME
    ENV.append 'CMAKE_INCLUDE_PATH', incdir, ':'
    ENV.append 'PKG_CONFIG_PATH', pkg_config_path, ':' if pkg_config_path

    # Udpate distutils.cfg (later we can remove this, but people still have
    # their old brewed pythons and we have to update it here)
    # Todo: If Jack's formula revisions arrive, we can get rid of this here!
    if brewed?
      require 'formula'
      file = Formula.factory(@name).prefix/"Frameworks/Python.framework/Versions/#{version.major}.#{version.minor}/lib/#{xy}/distutils/distutils.cfg"
      ohai "Writing #{file}" if ARGV.verbose? || ARGV.homebrew_developer?
      file.delete if file.exist?
      file.write <<-EOF.undent
        [global]
        verbose=1
        [install]
        force=1
        prefix=#{HOMEBREW_PREFIX}
      EOF
    end
  end

  def sitecustomize
    <<-EOF.undent
      # This file is created by Homebrew and is executed on each python startup.
      # Don't print from here, or else universe will collapse.
      import sys

      if sys.version_info.major == #{version.major} and sys.version_info.minor == #{version.minor}:
          if sys.executable.startswith('#{HOMEBREW_PREFIX}'):
              # Fix 1)
              #   A setuptools.pth and/or easy-install.pth sitting either in
              #   /Library/Python/2.7/site-packages or in
              #   ~/Library/Python/2.7/site-packages can inject the
              #   /System's Python site-packages. People then report
              #   "OSError: [Errno 13] Permission denied" because pip/easy_install
              #   attempts to install into
              #   /System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python
              #   See: https://github.com/mxcl/homebrew/issues/14712
              # Fix 2)
              #   Remove brewed Python's hard-coded Cellar-site-packages
              sys.path = [ p for p in sys.path
                           if not (p.startswith('/System') or
                                   p.startswith('#{HOMEBREW_PREFIX}/Cellar/python') and p.endswith('site-packages')) ]
              # Fix 3)
              # Set the sys.executable to use the opt_prefix
              sys.executable = '#{HOMEBREW_PREFIX}/opt/#{name}/bin/python#{version.major}.#{version.minor}'
              # Fix 4)
              # Make LINKFORSHARED (and python-confing --ldflags) return the
              # full path to the lib (yes, "Python" is actually the lib, not a
              # dir) so that third-party software does not need to add the
              # -F/#{HOMEBREW_PREFIX}/Frameworks switch.
              # Assume Framework style build (default since months in brew)
              try:
                  from _sysconfigdata import build_time_vars
                  build_time_vars['LINKFORSHARED'] = '-u _PyMac_Error #{HOMEBREW_PREFIX}/opt/#{name}/Frameworks/Python.framework/Versions/#{version.major}.#{version.minor}/Python'
              except:
                  pass  # remember: don't print here. Better to fail silent.
          # Fix 5)
          #   For all Pythons of the right major.minor version: Tell about homebrew's
          #   site-packages location. This is needed for Python to parse *.pth.
          import site
          site.addsitedir('#{global_site_packages}')
    EOF
  end

  def message
    @unsatisfied_because
  end

  def <=> other
    version <=> other.version
  end

  def to_s
    binary.to_s
  end

  def hash
    to_s.hash
  end
end