# Copyright (c) 2012 Google Inc. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

import gyp
import gyp.common
import gyp.system_test
import gyp.xcode_emulation
import os.path
import re
import subprocess
import sys

import gyp.ninja_syntax as ninja_syntax

generator_default_variables = {
  'EXECUTABLE_PREFIX': '',
  'EXECUTABLE_SUFFIX': '',
  'STATIC_LIB_PREFIX': 'lib',
  'STATIC_LIB_SUFFIX': '.a',
  'SHARED_LIB_PREFIX': 'lib',

  # Gyp expects the following variables to be expandable by the build
  # system to the appropriate locations.  Ninja prefers paths to be
  # known at gyp time.  To resolve this, introduce special
  # variables starting with $! (which begin with a $ so gyp knows it
  # should be treated as a path, but is otherwise an invalid
  # ninja/shell variable) that are passed to gyp here but expanded
  # before writing out into the target .ninja files; see
  # ExpandSpecial.
  'INTERMEDIATE_DIR': '$!INTERMEDIATE_DIR',
  'SHARED_INTERMEDIATE_DIR': '$!PRODUCT_DIR/gen',
  'PRODUCT_DIR': '$!PRODUCT_DIR',

  # Special variables that may be used by gyp 'rule' targets.
  # We generate definitions for these variables on the fly when processing a
  # rule.
  'RULE_INPUT_ROOT': '${root}',
  'RULE_INPUT_DIRNAME': '${dirname}',
  'RULE_INPUT_PATH': '${source}',
  'RULE_INPUT_EXT': '${ext}',
  'RULE_INPUT_NAME': '${name}',
}

# TODO: enable cross compiling once we figure out:
# - how to not build extra host objects in the non-cross-compile case.
# - how to decide what the host compiler is (should not just be $cc).
# - need ld_host as well.
generator_supports_multiple_toolsets = False


def StripPrefix(arg, prefix):
  if arg.startswith(prefix):
    return arg[len(prefix):]
  return arg


def QuoteShellArgument(arg):
  """Quote a string such that it will be interpreted as a single argument
  by the shell."""
  # Rather than attempting to enumerate the bad shell characters, just
  # whitelist common OK ones and quote anything else.
  if re.match(r'^[a-zA-Z0-9_=-]+$', arg):
    return arg  # No quoting necessary.
  return "'" + arg.replace("'", "'" + '"\'"' + "'")  + "'"


def InvertRelativePath(path):
  """Given a relative path like foo/bar, return the inverse relative path:
  the path from the relative path back to the origin dir.

  E.g. os.path.normpath(os.path.join(path, InvertRelativePath(path)))
  should always produce the empty string."""

  if not path:
    return path
  # Only need to handle relative paths into subdirectories for now.
  assert '..' not in path, path
  depth = len(path.split('/'))
  return '/'.join(['..'] * depth)


class Target:
  """Target represents the paths used within a single gyp target.

  Conceptually, building a single target A is a series of steps:

  1) actions/rules/copies  generates source/resources/etc.
  2) compiles              generates .o files
  3) link                  generates a binary (library/executable)
  4) bundle                merges the above in a mac bundle

  (Any of these steps can be optional.)

  From a build ordering perspective, a dependent target B could just
  depend on the last output of this series of steps.

  But some dependent commands sometimes need to reach inside the box.
  For example, when linking B it needs to get the path to the static
  library generated by A.

  This object stores those paths.  To keep things simple, member
  variables only store concrete paths to single files, while methods
  compute derived values like "the last output of the target".
  """
  def __init__(self, type):
    # Gyp type ("static_library", etc.) of this target.
    self.type = type
    # File representing the completion of actions/rules/copies, if any.
    self.actions_stamp = None
    # Path to the output of the link step, if any.
    self.binary = None
    # Path to the file representing the completion of building the bundle,
    # if any.
    self.bundle = None

  def Linkable(self):
    """Return true if this is a target that can be linked against."""
    return self.type in ('static_library', 'shared_library')

  def PrecompileInput(self):
    """Return the path, if any, that should be used as a dependency of
    any dependent compile step."""
    return self.actions_stamp

  def FinalOutput(self):
    """Return the last output of the target, which depends on all prior
    steps."""
    return self.bundle or self.binary or self.actions_stamp


# A small discourse on paths as used within the Ninja build:
# All files we produce (both at gyp and at build time) appear in the
# build directory (e.g. out/Debug).
#
# Paths within a given .gyp file are always relative to the directory
# containing the .gyp file.  Call these "gyp paths".  This includes
# sources as well as the starting directory a given gyp rule/action
# expects to be run from.  We call the path from the source root to
# the gyp file the "base directory" within the per-.gyp-file
# NinjaWriter code.
#
# All paths as written into the .ninja files are relative to the build
# directory.  Call these paths "ninja paths".
#
# We translate between these two notions of paths with two helper
# functions:
#
# - GypPathToNinja translates a gyp path (i.e. relative to the .gyp file)
#   into the equivalent ninja path.
#
# - GypPathToUniqueOutput translates a gyp path into a ninja path to write
#   an output file; the result can be namespaced such that is unique
#   to the input file name as well as the output target name.

class NinjaWriter:
  def __init__(self, target_outputs, base_dir, build_dir, output_file, flavor,
               abs_build_dir=None):
    """
    base_dir: path from source root to directory containing this gyp file,
              by gyp semantics, all input paths are relative to this
    build_dir: path from source root to build output
    abs_build_dir: absolute path to the build directory
    """

    self.target_outputs = target_outputs
    self.base_dir = base_dir
    self.build_dir = build_dir
    self.ninja = ninja_syntax.Writer(output_file)
    self.flavor = flavor
    self.abs_build_dir = abs_build_dir

    # Relative path from build output dir to base dir.
    self.build_to_base = os.path.join(InvertRelativePath(build_dir), base_dir)
    # Relative path from base dir to build dir.
    self.base_to_build = os.path.join(InvertRelativePath(base_dir), build_dir)

  def ExpandSpecial(self, path, product_dir=None):
    """Expand specials like $!PRODUCT_DIR in |path|.

    If |product_dir| is None, assumes the cwd is already the product
    dir.  Otherwise, |product_dir| is the relative path to the product
    dir.
    """

    PRODUCT_DIR = '$!PRODUCT_DIR'
    if PRODUCT_DIR in path:
      if product_dir:
        path = path.replace(PRODUCT_DIR, product_dir)
      else:
        path = path.replace(PRODUCT_DIR + '/', '')
        path = path.replace(PRODUCT_DIR, '.')

    INTERMEDIATE_DIR = '$!INTERMEDIATE_DIR'
    if INTERMEDIATE_DIR in path:
      int_dir = self.GypPathToUniqueOutput('gen')
      # GypPathToUniqueOutput generates a path relative to the product dir,
      # so insert product_dir in front if it is provided.
      path = path.replace(INTERMEDIATE_DIR,
                          os.path.join(product_dir or '', int_dir))

    return path

  def ExpandRuleVariables(self, path, root, dirname, source, ext, name):
    path = path.replace(generator_default_variables['RULE_INPUT_ROOT'], root)
    path = path.replace(generator_default_variables['RULE_INPUT_DIRNAME'],
                        dirname)
    path = path.replace(generator_default_variables['RULE_INPUT_PATH'], source)
    path = path.replace(generator_default_variables['RULE_INPUT_EXT'], ext)
    path = path.replace(generator_default_variables['RULE_INPUT_NAME'], name)
    return path

  def GypPathToNinja(self, path, env=None):
    """Translate a gyp path to a ninja path, optionally expanding environment
    variable references in |path| with |env|.

    See the above discourse on path conversions."""
    if env:
      path = gyp.xcode_emulation.ExpandEnvVars(path, env)
    if path.startswith('$!'):
      return self.ExpandSpecial(path)
    assert '$' not in path, path
    return os.path.normpath(os.path.join(self.build_to_base, path))

  def GypPathToUniqueOutput(self, path, qualified=True):
    """Translate a gyp path to a ninja path for writing output.

    If qualified is True, qualify the resulting filename with the name
    of the target.  This is necessary when e.g. compiling the same
    path twice for two separate output targets.

    See the above discourse on path conversions."""

    path = self.ExpandSpecial(path)
    assert not path.startswith('$'), path

    # Translate the path following this scheme:
    #   Input: foo/bar.gyp, target targ, references baz/out.o
    #   Output: obj/foo/baz/targ.out.o (if qualified)
    #           obj/foo/baz/out.o (otherwise)
    #     (and obj.host instead of obj for cross-compiles)
    #
    # Why this scheme and not some other one?
    # 1) for a given input, you can compute all derived outputs by matching
    #    its path, even if the input is brought via a gyp file with '..'.
    # 2) simple files like libraries and stamps have a simple filename.

    obj = 'obj'
    if self.toolset != 'target':
      obj += '.' + self.toolset

    path_dir, path_basename = os.path.split(path)
    if qualified:
      path_basename = self.name + '.' + path_basename
    return os.path.normpath(os.path.join(obj, self.base_dir, path_dir,
                                         path_basename))

  def WriteCollapsedDependencies(self, name, targets):
    """Given a list of targets, return a path for a single file
    representing the result of building all the targets or None.

    Uses a stamp file if necessary."""

    assert targets == filter(None, targets), targets
    if len(targets) == 0:
      return None
    if len(targets) > 1:
      stamp = self.GypPathToUniqueOutput(name + '.stamp')
      targets = self.ninja.build(stamp, 'stamp', targets)
      self.ninja.newline()
    return targets[0]

  def WriteSpec(self, spec, config_name):
    """The main entry point for NinjaWriter: write the build rules for a spec.

    Returns a Target object, which represents the output paths for this spec.
    Returns None if there are no outputs (e.g. a settings-only 'none' type
    target)."""

    self.config_name = config_name
    self.name = spec['target_name']
    self.toolset = spec['toolset']
    config = spec['configurations'][config_name]
    self.target = Target(spec['type'])

    if spec['type'] == 'settings':
      # TODO: 'settings' is not actually part of gyp; it was
      # accidentally introduced somehow into just the Linux build files.
      # Remove this (or make it an error) once all the users are fixed.
      print ("WARNING: %s uses invalid type 'settings'.  " % self.name +
             "Please fix the source gyp file to use type 'none'.")
      print "See http://code.google.com/p/chromium/issues/detail?id=96629 ."
      spec['type'] = 'none'

    self.is_mac_bundle = gyp.xcode_emulation.IsMacBundle(self.flavor, spec)
    if self.flavor == 'mac':
      self.xcode_settings = gyp.xcode_emulation.XcodeSettings(spec)
    else:
      self.xcode_settings = None

    # Compute predepends for all rules.
    # actions_depends is the dependencies this target depends on before running
    # any of its action/rule/copy steps.
    # compile_depends is the dependencies this target depends on before running
    # any of its compile steps.
    actions_depends = []
    compile_depends = []
    if 'dependencies' in spec:
      actions_depends = []
      for dep in spec['dependencies']:
        if dep in self.target_outputs:
          target = self.target_outputs[dep]
          actions_depends.append(target.FinalOutput())
          compile_depends.append(target.PrecompileInput())
      actions_depends = filter(None, actions_depends)
      compile_depends = filter(None, compile_depends)
      actions_depends = self.WriteCollapsedDependencies('actions_depends',
                                                        actions_depends)

    # Write out actions, rules, and copies.  These must happen before we
    # compile any sources, so compute a list of predependencies for sources
    # while we do it.
    extra_sources = []
    mac_bundle_depends = []
    self.target.actions_stamp = self.WriteActionsRulesCopies(
        spec, extra_sources, actions_depends, mac_bundle_depends)

    # If we have actions/rules/copies, we depend directly on those, but
    # otherwise we depend on dependent target's actions/rules/copies etc.
    # We never need to explicitly depend on previous target's link steps,
    # because no compile ever depends on them.
    compile_depends_stamp = (self.target.actions_stamp or
        self.WriteCollapsedDependencies('compile_depends', compile_depends))

    # Write out the compilation steps, if any.
    link_deps = []
    sources = spec.get('sources', []) + extra_sources
    if sources:
      link_deps = self.WriteSources(
          config_name, config, sources, compile_depends_stamp,
          gyp.xcode_emulation.MacPrefixHeader(
              self.xcode_settings, self.GypPathToNinja,
              lambda path, lang: self.GypPathToUniqueOutput(path + '-' + lang)))
      # Some actions/rules output 'sources' that are already object files.
      link_deps += [self.GypPathToNinja(f) for f in sources if f.endswith('.o')]

    # Write out a link step, if needed.
    output = None
    if link_deps or self.target.actions_stamp or actions_depends:
      output = self.WriteTarget(spec, config_name, config, link_deps,
                                self.target.actions_stamp or actions_depends)
      if self.is_mac_bundle:
        mac_bundle_depends.append(output)

    # Bundle all of the above together, if needed.
    if self.is_mac_bundle:
      output = self.WriteMacBundle(spec, mac_bundle_depends)

    if not output:
      return None

    if self.name != output and self.toolset == 'target':
      # Write a short name to build this target.  This benefits both the
      # "build chrome" case as well as the gyp tests, which expect to be
      # able to run actions and build libraries by their short name.
      self.ninja.build(self.name, 'phony', output)

    assert self.target.FinalOutput(), output
    return self.target

  def WriteActionsRulesCopies(self, spec, extra_sources, prebuild,
                              mac_bundle_depends):
    """Write out the Actions, Rules, and Copies steps.  Return a path
    representing the outputs of these steps."""
    outputs = []
    extra_mac_bundle_resources = []

    if 'actions' in spec:
      outputs += self.WriteActions(spec['actions'], extra_sources, prebuild,
                                   extra_mac_bundle_resources)
    if 'rules' in spec:
      outputs += self.WriteRules(spec['rules'], extra_sources, prebuild,
                                 extra_mac_bundle_resources)
    if 'copies' in spec:
      outputs += self.WriteCopies(spec['copies'], prebuild)

    stamp = self.WriteCollapsedDependencies('actions_rules_copies', outputs)

    if self.is_mac_bundle:
      mac_bundle_resources = spec.get('mac_bundle_resources', []) + \
                             extra_mac_bundle_resources
      self.WriteMacBundleResources(mac_bundle_resources, mac_bundle_depends)
      self.WriteMacInfoPlist(mac_bundle_depends)

    return stamp

  def GenerateDescription(self, verb, message, fallback):
    """Generate and return a description of a build step.

    |verb| is the short summary, e.g. ACTION or RULE.
    |message| is a hand-written description, or None if not available.
    |fallback| is the gyp-level name of the step, usable as a fallback.
    """
    if self.toolset != 'target':
      verb += '(%s)' % self.toolset
    if message:
      return '%s %s' % (verb, self.ExpandSpecial(message))
    else:
      return '%s %s: %s' % (verb, self.name, fallback)

  def WriteActions(self, actions, extra_sources, prebuild,
                   extra_mac_bundle_resources):
    # Actions cd into the base directory.
    env = self.GetXcodeEnv()
    all_outputs = []
    for action in actions:
      # First write out a rule for the action.
      name = re.sub(r'[ {}$]', '_', action['action_name'])
      description = self.GenerateDescription('ACTION',
                                             action.get('message', None),
                                             name)
      rule_name = self.WriteNewNinjaRule(name, action['action'], description,
                                         env=env)

      inputs = [self.GypPathToNinja(i, env) for i in action['inputs']]
      if int(action.get('process_outputs_as_sources', False)):
        extra_sources += action['outputs']
      if int(action.get('process_outputs_as_mac_bundle_resources', False)):
        extra_mac_bundle_resources += action['outputs']
      outputs = [self.GypPathToNinja(o, env) for o in action['outputs']]

      # Then write out an edge using the rule.
      self.ninja.build(outputs, rule_name, inputs,
                       order_only=prebuild)
      all_outputs += outputs

      self.ninja.newline()

    return all_outputs

  def WriteRules(self, rules, extra_sources, prebuild,
                 extra_mac_bundle_resources):
    all_outputs = []
    for rule in rules:
      # First write out a rule for the rule action.
      name = rule['rule_name']
      args = rule['action']
      description = self.GenerateDescription(
          'RULE',
          rule.get('message', None),
          ('%s ' + generator_default_variables['RULE_INPUT_PATH']) % name)
      rule_name = self.WriteNewNinjaRule(name, args, description)

      # TODO: if the command references the outputs directly, we should
      # simplify it to just use $out.

      # Rules can potentially make use of some special variables which
      # must vary per source file.
      # Compute the list of variables we'll need to provide.
      special_locals = ('source', 'root', 'dirname', 'ext', 'name')
      needed_variables = set(['source'])
      for argument in args:
        for var in special_locals:
          if ('${%s}' % var) in argument:
            needed_variables.add(var)

      # For each source file, write an edge that generates all the outputs.
      for source in rule.get('rule_sources', []):
        dirname, basename = os.path.split(source)
        root, ext = os.path.splitext(basename)

        # Gather the list of outputs, expanding $vars if possible.
        outputs = []
        for output in rule['outputs']:
          outputs.append(self.ExpandRuleVariables(output, root, dirname,
                                                  source, ext, basename))

        if int(rule.get('process_outputs_as_sources', False)):
          extra_sources += outputs
        if int(rule.get('process_outputs_as_mac_bundle_resources', False)):
          extra_mac_bundle_resources += outputs

        extra_bindings = []
        for var in needed_variables:
          if var == 'root':
            extra_bindings.append(('root', root))
          elif var == 'dirname':
            extra_bindings.append(('dirname', dirname))
          elif var == 'source':
            # '$source' is a parameter to the rule action, which means
            # it shouldn't be converted to a Ninja path.  But we don't
            # want $!PRODUCT_DIR in there either.
            source_expanded = self.ExpandSpecial(source, self.base_to_build)
            extra_bindings.append(('source', source_expanded))
          elif var == 'ext':
            extra_bindings.append(('ext', ext))
          elif var == 'name':
            extra_bindings.append(('name', basename))
          else:
            assert var == None, repr(var)

        inputs = map(self.GypPathToNinja, rule.get('inputs', []))
        outputs = map(self.GypPathToNinja, outputs)
        self.ninja.build(outputs, rule_name, self.GypPathToNinja(source),
                         implicit=inputs,
                         order_only=prebuild,
                         variables=extra_bindings)

        all_outputs.extend(outputs)

    return all_outputs

  def WriteCopies(self, copies, prebuild):
    outputs = []
    env = self.GetXcodeEnv()
    for copy in copies:
      for path in copy['files']:
        # Normalize the path so trailing slashes don't confuse us.
        path = os.path.normpath(path)
        basename = os.path.split(path)[1]
        src = self.GypPathToNinja(path, env)
        dst = self.GypPathToNinja(os.path.join(copy['destination'], basename),
                                  env)
        outputs += self.ninja.build(dst, 'copy', src, order_only=prebuild)

    return outputs

  def WriteMacBundleResources(self, resources, bundle_depends):
    """Writes ninja edges for 'mac_bundle_resources'."""
    for output, res in gyp.xcode_emulation.GetMacBundleResources(
        self.ExpandSpecial(generator_default_variables['PRODUCT_DIR']),
        self.xcode_settings, map(self.GypPathToNinja, resources)):
      self.ninja.build(output, 'mac_tool', res,
                       variables=[('mactool_cmd', 'copy-bundle-resource')])
      bundle_depends.append(output)

  def WriteMacInfoPlist(self, bundle_depends):
    """Write build rules for bundle Info.plist files."""
    info_plist, out, defines, extra_env = gyp.xcode_emulation.GetMacInfoPlist(
        self.ExpandSpecial(generator_default_variables['PRODUCT_DIR']),
        self.xcode_settings, self.GypPathToNinja)
    if not info_plist:
      return
    if defines:
      # Create an intermediate file to store preprocessed results.
      intermediate_plist = self.GypPathToUniqueOutput(
          os.path.basename(info_plist))
      defines = ' '.join(
          [QuoteShellArgument(ninja_syntax.escape('-D' + d)) for d in defines])
      info_plist = self.ninja.build(intermediate_plist, 'infoplist', info_plist,
                                    variables=[('defines',defines)])

    env = self.GetXcodeEnv(additional_settings=extra_env)
    env = self.ComputeExportEnvString(env)

    self.ninja.build(out, 'mac_tool', info_plist,
                     variables=[('mactool_cmd', 'copy-info-plist'),
                                ('env', env)])
    bundle_depends.append(out)

  def WriteSources(self, config_name, config, sources, predepends,
                   precompiled_header):
    """Write build rules to compile all of |sources|."""
    if self.toolset == 'host':
      self.ninja.variable('cc', '$cc_host')
      self.ninja.variable('cxx', '$cxx_host')

    if self.flavor == 'mac':
      cflags = self.xcode_settings.GetCflags(config_name)
      cflags_c = self.xcode_settings.GetCflagsC(config_name)
      cflags_cc = self.xcode_settings.GetCflagsCC(config_name)
      cflags_objc = ['$cflags_c'] + \
                    self.xcode_settings.GetCflagsObjC(config_name)
      cflags_objcc = ['$cflags_cc'] + \
                     self.xcode_settings.GetCflagsObjCC(config_name)
    else:
      cflags = config.get('cflags', [])
      cflags_c = config.get('cflags_c', [])
      cflags_cc = config.get('cflags_cc', [])

    self.WriteVariableList('defines',
        [QuoteShellArgument(ninja_syntax.escape('-D' + d))
         for d in config.get('defines', [])])
    self.WriteVariableList('includes',
                           ['-I' + self.GypPathToNinja(i)
                            for i in config.get('include_dirs', [])])

    pch_commands = precompiled_header.GetGchBuildCommands()
    if self.flavor == 'mac':
      self.WriteVariableList('cflags_pch_c',
                             [precompiled_header.GetInclude('c')])
      self.WriteVariableList('cflags_pch_cc',
                             [precompiled_header.GetInclude('cc')])
      self.WriteVariableList('cflags_pch_objc',
                             [precompiled_header.GetInclude('m')])
      self.WriteVariableList('cflags_pch_objcc',
                             [precompiled_header.GetInclude('mm')])

    self.WriteVariableList('cflags', map(self.ExpandSpecial, cflags))
    self.WriteVariableList('cflags_c', map(self.ExpandSpecial, cflags_c))
    self.WriteVariableList('cflags_cc', map(self.ExpandSpecial, cflags_cc))
    if self.flavor == 'mac':
      self.WriteVariableList('cflags_objc', map(self.ExpandSpecial,
                                                cflags_objc))
      self.WriteVariableList('cflags_objcc', map(self.ExpandSpecial,
                                                 cflags_objcc))
    self.ninja.newline()
    outputs = []
    for source in sources:
      filename, ext = os.path.splitext(source)
      ext = ext[1:]
      if ext in ('cc', 'cpp', 'cxx'):
        command = 'cxx'
      elif ext in ('c', 's', 'S'):
        command = 'cc'
      elif self.flavor == 'mac' and ext == 'm':
        command = 'objc'
      elif self.flavor == 'mac' and ext == 'mm':
        command = 'objcxx'
      else:
        # TODO: should we assert here on unexpected extensions?
        continue
      input = self.GypPathToNinja(source)
      output = self.GypPathToUniqueOutput(filename + '.o')
      implicit = precompiled_header.GetObjDependencies([input], [output])
      self.ninja.build(output, command, input,
                       implicit=[gch for _, _, gch in implicit],
                       order_only=predepends)
      outputs.append(output)

    self.WritePchTargets(pch_commands)

    self.ninja.newline()
    return outputs

  def WritePchTargets(self, pch_commands):
    """Writes ninja rules to compile prefix headers."""
    if not pch_commands:
      return

    for gch, lang_flag, lang, input in pch_commands:
      var_name = {
        'c': 'cflags_pch_c',
        'cc': 'cflags_pch_cc',
        'm': 'cflags_pch_objc',
        'mm': 'cflags_pch_objcc',
      }[lang]

      cmd = { 'c': 'cc', 'cc': 'cxx', 'm': 'objc', 'mm': 'objcxx', }.get(lang)
      self.ninja.build(gch, cmd, input, variables=[(var_name, lang_flag)])


  def WriteLink(self, spec, config_name, config, link_deps):
    """Write out a link step.  Returns the path to the output."""

    command = {
      'executable':      'link',
      'loadable_module': 'solink_module',
      'shared_library':  'solink',
    }[spec['type']]

    implicit_deps = set()

    if 'dependencies' in spec:
      # Two kinds of dependencies:
      # - Linkable dependencies (like a .a or a .so): add them to the link line.
      # - Non-linkable dependencies (like a rule that generates a file
      #   and writes a stamp file): add them to implicit_deps
      extra_link_deps = set()
      for dep in spec['dependencies']:
        target = self.target_outputs.get(dep)
        if not target:
          continue
        linkable = target.Linkable()
        if linkable:
          extra_link_deps.add(target.binary)

        final_output = target.FinalOutput()
        if not linkable or final_output != target.binary:
          implicit_deps.add(final_output)

      link_deps.extend(list(extra_link_deps))

    if self.is_mac_bundle:
      output = self.ComputeMacBundleBinaryOutput()
    else:
      output = self.ComputeOutput(spec)

    if self.flavor == 'mac':
      ldflags = self.xcode_settings.GetLdflags(config_name,
          self.ExpandSpecial(generator_default_variables['PRODUCT_DIR']),
          self.GypPathToNinja)
    else:
      ldflags = config.get('ldflags', [])
    self.WriteVariableList('ldflags',
                           gyp.common.uniquer(map(self.ExpandSpecial,
                                                  ldflags)))

    libraries = gyp.common.uniquer(map(self.ExpandSpecial,
                                       spec.get('libraries', [])))
    if self.flavor == 'mac':
      libraries = self.xcode_settings.AdjustLibraries(libraries)
    self.WriteVariableList('libs', libraries)

    extra_bindings = []
    if command in ('solink', 'solink_module'):
      extra_bindings.append(('soname', os.path.split(output)[1]))

    self.ninja.build(output, command, link_deps,
                     implicit=list(implicit_deps),
                     variables=extra_bindings)
    return output

  def WriteTarget(self, spec, config_name, config, link_deps, compile_deps):
    if spec['type'] == 'none':
      # TODO(evan): don't call this function for 'none' target types, as
      # it doesn't do anything, and we fake out a 'binary' with a stamp file.
      self.target.binary = compile_deps
    elif spec['type'] == 'static_library':
      self.target.binary = self.ComputeOutput(spec)
      self.ninja.build(self.target.binary, 'alink', link_deps,
                       order_only=compile_deps)
    else:
      self.target.binary = self.WriteLink(spec, config_name, config, link_deps)
    return self.target.binary

  def WriteMacBundle(self, spec, mac_bundle_depends):
    assert self.is_mac_bundle
    output = self.ComputeMacBundleOutput()
    if spec['type'] in ('shared_library', 'loadable_module'):
      variables = [('version', self.xcode_settings.GetFrameworkVersion())]
      self.ninja.build(output, 'package_framework', mac_bundle_depends,
                       variables=variables)
    else:
      self.ninja.build(output, 'stamp', mac_bundle_depends)
    self.target.bundle = output
    return output

  def GetXcodeEnv(self, additional_settings=None):
    """Returns the variables Xcode would set for build steps."""
    assert self.abs_build_dir
    abs_build_dir = self.abs_build_dir
    return gyp.xcode_emulation.GetXcodeEnv(
        self.xcode_settings, abs_build_dir,
        os.path.join(abs_build_dir, self.build_to_base), self.config_name,
        additional_settings)

  def ComputeExportEnvString(self, env):
    """Given an environment, returns a string looking like
        'export FOO=foo; export BAR="${FOO} bar;'
    that exports |env| to the shell."""
    export_str = []
    for k in gyp.xcode_emulation.TopologicallySortedEnvVarKeys(env):
      export_str.append('export %s=%s;' %
          (k, ninja_syntax.escape(gyp.common.EncodePOSIXShellArgument(env[k]))))
    return ' '.join(export_str)

  def ComputeMacBundleOutput(self):
    """Return the 'output' (full output path) to a bundle output directory."""
    assert self.is_mac_bundle
    path = self.ExpandSpecial(generator_default_variables['PRODUCT_DIR'])
    return os.path.join(path, self.xcode_settings.GetWrapperName())

  def ComputeMacBundleBinaryOutput(self):
    """Return the 'output' (full output path) to the binary in a bundle."""
    assert self.is_mac_bundle
    path = self.ExpandSpecial(generator_default_variables['PRODUCT_DIR'])
    return os.path.join(path, self.xcode_settings.GetExecutablePath())

  def ComputeOutputFileName(self, spec, type=None):
    """Compute the filename of the final output for the current target."""
    if not type:
      type = spec['type']

    # Compute filename prefix: the product prefix, or a default for
    # the product type.
    DEFAULT_PREFIX = {
      'loadable_module': 'lib',
      'shared_library': 'lib',
      'static_library': 'lib',
      }
    prefix = spec.get('product_prefix', DEFAULT_PREFIX.get(type, ''))

    # Compute filename extension: the product extension, or a default
    # for the product type.
    DEFAULT_EXTENSION = {
      'static_library': 'a',
      'loadable_module': 'so',
      'shared_library': 'so',
      }
    extension = spec.get('product_extension',
                         DEFAULT_EXTENSION.get(type, ''))
    if extension:
      extension = '.' + extension

    if 'product_name' in spec:
      # If we were given an explicit name, use that.
      target = spec['product_name']
    else:
      # Otherwise, derive a name from the target name.
      target = spec['target_name']
      if prefix == 'lib':
        # Snip out an extra 'lib' from libs if appropriate.
        target = StripPrefix(target, 'lib')

    if type in ('static_library', 'loadable_module', 'shared_library',
                        'executable'):
      return '%s%s%s' % (prefix, target, extension)
    elif type == 'none':
      return '%s.stamp' % target
    else:
      raise 'Unhandled output type', type

  def ComputeOutput(self, spec, type=None):
    """Compute the path for the final output of the spec."""
    assert not self.is_mac_bundle or type

    if not type:
      type = spec['type']

    if self.flavor == 'mac' and type in (
        'static_library', 'executable', 'shared_library', 'loadable_module'):
      filename = self.xcode_settings.GetExecutablePath()
    else:
      filename = self.ComputeOutputFileName(spec, type)

    if 'product_dir' in spec:
      path = os.path.join(spec['product_dir'], filename)
      return self.ExpandSpecial(path)

    # Some products go into the output root, libraries go into shared library
    # dir, and everything else goes into the normal place.
    type_in_output_root = ['executable', 'loadable_module']
    if self.flavor == 'mac' and self.toolset == 'target':
      type_in_output_root += ['shared_library', 'static_library']

    if type in type_in_output_root:
      return filename
    elif type == 'shared_library':
      libdir = 'lib'
      if self.toolset != 'target':
        libdir = 'lib/%s' % self.toolset
      return os.path.join(libdir, filename)
    else:
      return self.GypPathToUniqueOutput(filename, qualified=False)

  def WriteVariableList(self, var, values):
    if values is None:
      values = []
    self.ninja.variable(var, ' '.join(values))

  def WriteNewNinjaRule(self, name, args, description, env={}):
    """Write out a new ninja "rule" statement for a given command.

    Returns the name of the new rule."""

    # TODO: we shouldn't need to qualify names; we do it because
    # currently the ninja rule namespace is global, but it really
    # should be scoped to the subninja.
    rule_name = self.name
    if self.toolset == 'target':
      rule_name += '.' + self.toolset
    rule_name += '.' + name
    rule_name = rule_name.replace(' ', '_')

    args = args[:]

    # gyp dictates that commands are run from the base directory.
    # cd into the directory before running, and adjust paths in
    # the arguments to point to the proper locations.
    cd = 'cd %s; ' % self.build_to_base
    args = [self.ExpandSpecial(arg, self.base_to_build) for arg in args]
    env = self.ComputeExportEnvString(env)
    command = gyp.common.EncodePOSIXShellList(args)
    if env:
      # If an environment is passed in, variables in the command should be
      # read from it, instead of from ninja's internal variables.
      command = ninja_syntax.escape(command)

    command = cd + env + command
    # GYP rules/actions express being no-ops by not touching their outputs.
    # Avoid executing downstream dependencies in this case by specifying
    # restat=1 to ninja.
    self.ninja.rule(rule_name, command, description, restat=True)
    self.ninja.newline()

    return rule_name


def CalculateVariables(default_variables, params):
  """Calculate additional variables for use in the build (called by gyp)."""
  cc_target = os.environ.get('CC.target', os.environ.get('CC', 'cc'))
  default_variables['LINKER_SUPPORTS_ICF'] = \
      gyp.system_test.TestLinkerSupportsICF(cc_command=cc_target)

  flavor = gyp.common.GetFlavor(params)
  if flavor == 'mac':
    default_variables.setdefault('OS', 'mac')
    default_variables.setdefault('SHARED_LIB_SUFFIX', '.dylib')
    default_variables.setdefault('SHARED_LIB_DIR',
                                 generator_default_variables['PRODUCT_DIR'])
    default_variables.setdefault('LIB_DIR',
                                 generator_default_variables['PRODUCT_DIR'])

    # Copy additional generator configuration data from Xcode, which is shared
    # by the Mac Ninja generator.
    import gyp.generator.xcode as xcode_generator
    global generator_additional_non_configuration_keys
    generator_additional_non_configuration_keys = getattr(xcode_generator,
        'generator_additional_non_configuration_keys', [])
    global generator_additional_path_sections
    generator_additional_path_sections = getattr(xcode_generator,
        'generator_additional_path_sections', [])
    global generator_extra_sources_for_rules
    generator_extra_sources_for_rules = getattr(xcode_generator,
        'generator_extra_sources_for_rules', [])
  else:
    operating_system = flavor
    if flavor == 'android':
      operating_system = 'linux'  # Keep this legacy behavior for now.
    default_variables.setdefault('OS', operating_system)
    default_variables.setdefault('SHARED_LIB_SUFFIX', '.so')
    default_variables.setdefault('SHARED_LIB_DIR', '$!PRODUCT_DIR/lib')
    default_variables.setdefault('LIB_DIR', '')


def OpenOutput(path):
  """Open |path| for writing, creating directories if necessary."""
  try:
    os.makedirs(os.path.dirname(path))
  except OSError:
    pass
  return open(path, 'w')


def GenerateOutputForConfig(target_list, target_dicts, data, params,
                            config_name):
  options = params['options']
  flavor = gyp.common.GetFlavor(params)
  generator_flags = params.get('generator_flags', {})

  # build_dir: relative path from source root to our output files.
  # e.g. "out/Debug"
  build_dir = os.path.join(generator_flags.get('output_dir', 'out'),
                           config_name)

  master_ninja = ninja_syntax.Writer(
      OpenOutput(os.path.join(options.toplevel_dir, build_dir, 'build.ninja')),
      width=120)

  # Put build-time support tools in out/{config_name}.
  gyp.common.CopyTool(flavor, os.path.join(options.toplevel_dir, build_dir))

  # Grab make settings for CC/CXX.
  cc, cxx = 'gcc', 'g++'
  build_file, _, _ = gyp.common.ParseQualifiedTarget(target_list[0])
  make_global_settings = data[build_file].get('make_global_settings', [])
  build_to_root = InvertRelativePath(build_dir)
  for key, value in make_global_settings:
    if key == 'CC': cc = os.path.join(build_to_root, value)
    if key == 'CXX': cxx = os.path.join(build_to_root, value)

  # TODO: compute cc/cxx/ld/etc. by command-line arguments and system tests.
  master_ninja.variable('cc', os.environ.get('CC', cc))
  master_ninja.variable('cxx', os.environ.get('CXX', cxx))
  # TODO(bradnelson): remove NOGOLD when this is resolved:
  #     http://code.google.com/p/chromium/issues/detail?id=108251
  if flavor != 'mac' and not os.environ.get('NOGOLD'):
    master_ninja.variable('ld', '$cxx -Wl,--threads -Wl,--thread-count=4')
  else:
    # TODO(jeremya/thakis): flock
    master_ninja.variable('ld', '$cxx')
  master_ninja.variable('cc_host', '$cc')
  master_ninja.variable('cxx_host', '$cxx')
  if flavor == 'mac':
    master_ninja.variable('mac_tool', os.path.join('.', 'gyp-mac-tool'))
  master_ninja.newline()

  master_ninja.rule(
    'cc',
    description='CC $out',
    command=('$cc -MMD -MF $out.d $defines $includes $cflags $cflags_c '
             '$cflags_pch_c -c $in -o $out'),
    depfile='$out.d')
  master_ninja.rule(
    'cxx',
    description='CXX $out',
    command=('$cxx -MMD -MF $out.d $defines $includes $cflags $cflags_cc '
             '$cflags_pch_cc -c $in -o $out'),
    depfile='$out.d')
  if flavor != 'mac':
    master_ninja.rule(
      'alink',
      description='AR $out',
      command='rm -f $out && ar rcsT $out $in')
    master_ninja.rule(
      'solink',
      description='SOLINK $out',
      command=('$ld -shared $ldflags -o $out -Wl,-soname=$soname '
               '-Wl,--whole-archive $in -Wl,--no-whole-archive $libs'))
    master_ninja.rule(
      'solink_module',
      description='SOLINK(module) $out',
      command=('$ld -shared $ldflags -o $out -Wl,-soname=$soname '
               '-Wl,--start-group $in -Wl,--end-group $libs'))
    master_ninja.rule(
      'link',
      description='LINK $out',
      command=('$ld $ldflags -o $out -Wl,-rpath=\$$ORIGIN/lib '
               '-Wl,--start-group $in -Wl,--end-group $libs'))
  else:
    master_ninja.rule(
      'objc',
      description='OBJC $out',
      command=('$cc -MMD -MF $out.d $defines $includes $cflags $cflags_objc '
               '$cflags_pch_objc -c $in -o $out'),
      depfile='$out.d')
    master_ninja.rule(
      'objcxx',
      description='OBJCXX $out',
      command=('$cxx -MMD -MF $out.d $defines $includes $cflags $cflags_objcc '
               '$cflags_pch_objcc -c $in -o $out'),
      depfile='$out.d')
    master_ninja.rule(
      'alink',
      description='LIBTOOL-STATIC $out',
      command='rm -f $out && libtool -static -o $out $in')
    # TODO(thakis): The solink_module rule is likely wrong. Xcode seems to pass
    # -bundle -single_module here (for osmesa.so).
    master_ninja.rule(
      'solink',
      description='SOLINK $out',
      command=('$ld -shared $ldflags -o $out '
               '$in $libs'))
    master_ninja.rule(
      'solink_module',
      description='SOLINK(module) $out',
      command=('$ld -shared $ldflags -o $out '
               '$in $libs'))
    master_ninja.rule(
      'link',
      description='LINK $out',
      command=('$ld $ldflags -o $out '
               '$in $libs'))
    master_ninja.rule(
      'infoplist',
      description='INFOPLIST $out',
      command=('$cc -E -P -Wno-trigraphs -x c $defines $in -o $out && '
               'plutil -convert xml1 $out $out'))
    master_ninja.rule(
      'mac_tool',
      description='MACTOOL $mactool_cmd $in',
      command='$env $mac_tool $mactool_cmd $in $out')
    master_ninja.rule(
      'package_framework',
      description='PACKAGE FRAMEWORK $out',
      command='$mac_tool package-framework $out $version; touch $out')
  master_ninja.rule(
    'stamp',
    description='STAMP $out',
    command='touch $out')
  master_ninja.rule(
    'copy',
    description='COPY $in $out',
    command='ln -f $in $out 2>/dev/null || (rm -rf $out && cp -af $in $out)')
  master_ninja.newline()

  all_targets = set()
  for build_file in params['build_files']:
    for target in gyp.common.AllTargets(target_list, target_dicts, build_file):
      all_targets.add(target)
  all_outputs = set()

  # target_outputs is a map from qualified target name to a Target object.
  target_outputs = {}
  for qualified_target in target_list:
    # qualified_target is like: third_party/icu/icu.gyp:icui18n#target
    build_file, name, toolset = \
        gyp.common.ParseQualifiedTarget(qualified_target)

    this_make_global_settings = data[build_file].get('make_global_settings', [])
    assert make_global_settings == this_make_global_settings, (
        "make_global_settings needs to be the same for all targets.")

    spec = target_dicts[qualified_target]
    if flavor == 'mac':
      gyp.xcode_emulation.MergeGlobalXcodeSettingsToSpec(data[build_file], spec)

    # TODO: what is options.depth and how is it different than
    # options.toplevel_dir?
    build_file = gyp.common.RelativePath(build_file, options.depth)

    base_path = os.path.dirname(build_file)
    obj = 'obj'
    if toolset != 'target':
      obj += '.' + toolset
    output_file = os.path.join(obj, base_path, name + '.ninja')

    abs_build_dir=os.path.abspath(os.path.join(options.toplevel_dir, build_dir))
    writer = NinjaWriter(target_outputs, base_path, build_dir,
                         OpenOutput(os.path.join(options.toplevel_dir,
                                                 build_dir,
                                                 output_file)),
                         flavor, abs_build_dir=abs_build_dir)
    master_ninja.subninja(output_file)

    target = writer.WriteSpec(spec, config_name)
    if target:
      target_outputs[qualified_target] = target
      if qualified_target in all_targets:
        all_outputs.add(target.FinalOutput())

  if all_outputs:
    master_ninja.build('all', 'phony', list(all_outputs))


def GenerateOutput(target_list, target_dicts, data, params):
  if params['options'].generator_output:
    raise NotImplementedError, "--generator_output not implemented for ninja"

  user_config = params.get('generator_flags', {}).get('config', None)
  if user_config:
    GenerateOutputForConfig(target_list, target_dicts, data, params,
                            user_config)
  else:
    config_names = target_dicts[target_list[0]]['configurations'].keys()
    for config_name in config_names:
      GenerateOutputForConfig(target_list, target_dicts, data, params,
                              config_name)
