#!/usr/bin/env python3
# Copyright (C) 2019 The Android Open Source Project
#
# Licensed 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.

# This tool uses a collection of BUILD.gn files and build targets to generate
# an "amalgamated" C++ header and source file pair which compiles to an
# equivalent program. The tool also outputs the necessary compiler and linker
# flags needed to compile the resulting source code.

from __future__ import print_function
import argparse
import os
import re
import shutil
import subprocess
import sys
import tempfile

import gn_utils

# Default targets to include in the result.
# TODO(primiano): change this script to recurse into target deps when generating
# headers, but only for proto targets. .pbzero.h files don't include each other
# and we need to list targets here individually, which is unmaintainable.
default_targets = [
    '//:libperfetto_client_experimental',
    '//include/perfetto/protozero:protozero',
    '//protos/perfetto/config:zero',
    '//protos/perfetto/trace:zero',
]

# Arguments for the GN output directory (unless overridden from the command
# line).
gn_args = ' '.join([
    'enable_perfetto_ipc=true',
    'enable_perfetto_zlib=false',
    'is_debug=false',
    'is_perfetto_build_generator=true',
    'is_perfetto_embedder=true',
    'perfetto_enable_git_rev_version_header=true',
    'use_custom_libcxx=false',
])

# By default, the amalgamated .h only recurses in #includes but not in the
# target deps. In the case of protos we want to follow deps even in lieu of
# direct #includes. This is because, by design, protozero headers don't
# include each other but rely on forward declarations. The alternative would
# be adding each proto sub-target individually (e.g. //proto/trace/gpu:zero),
# but doing that is unmaintainable. We also do this for cpp bindings since some
# tracing SDK functions depend on them (and the system tracing IPC mechanism
# does so too).
recurse_in_header_deps = '^//protos/.*(cpp|zero)$'

# Compiler flags which aren't filtered out.
cflag_allowlist = r'^-(W.*|fno-exceptions|fPIC|std.*|fvisibility.*)$'

# Linker flags which aren't filtered out.
ldflag_allowlist = r'^-()$'

# Libraries which are filtered out.
lib_denylist = r'^(c|gcc_eh)$'

# Macros which aren't filtered out.
define_allowlist = r'^(PERFETTO.*|GOOGLE_PROTOBUF.*)$'

# Includes which will be removed from the generated source.
includes_to_remove = r'^(gtest).*$'

# From //gn:default_config (since "gn desc" doesn't describe configs).
default_includes = [
  'include',
]

default_cflags = [
    # Since we're expanding header files into the generated source file, some
    # constant may remain unused.
    '-Wno-unused-const-variable'
]

# Build flags to satisfy a protobuf (lite or full) dependency.
protobuf_cflags = [
    # Note that these point to the local copy of protobuf in buildtools. In
    # reality the user of the amalgamated result will have to provide a path to
    # an installed copy of the exact same version of protobuf which was used to
    # generate the amalgamated build.
    '-isystembuildtools/protobuf/src',
    '-Lbuildtools/protobuf/src/.libs',
    # We also need to disable some warnings for protobuf.
    '-Wno-missing-prototypes',
    '-Wno-missing-variable-declarations',
    '-Wno-sign-conversion',
    '-Wno-unknown-pragmas',
    '-Wno-unused-macros',
]

# A mapping of dependencies to system libraries. Libraries in this map will not
# be built statically but instead added as dependencies of the amalgamated
# project.
system_library_map = {
    '//buildtools:protobuf_full': {
        'libs': ['protobuf'],
        'cflags': protobuf_cflags,
    },
    '//buildtools:protobuf_lite': {
        'libs': ['protobuf-lite'],
        'cflags': protobuf_cflags,
    },
    '//buildtools:protoc_lib': {
        'libs': ['protoc']
    },
}

# ----------------------------------------------------------------------------
# End of configuration.
# ----------------------------------------------------------------------------

tool_name = os.path.basename(__file__)
project_root = os.path.abspath(os.path.dirname(os.path.dirname(__file__)))
preamble = """// Copyright (C) 2019 The Android Open Source Project
//
// Licensed 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.
//
// This file is automatically generated by %s. Do not edit.
""" % tool_name


def apply_denylist(denylist, items):
  return [item for item in items if not re.match(denylist, item)]


def apply_allowlist(allowlist, items):
  return [item for item in items if re.match(allowlist, item)]


def normalize_path(path):
  path = os.path.relpath(path, project_root)
  path = re.sub(r'^out/[^/]+/', '', path)
  return path


class Error(Exception):
  pass


class DependencyNode(object):
  """A target in a GN build description along with its dependencies."""

  def __init__(self, target_name):
    self.target_name = target_name
    self.dependencies = set()

  def add_dependency(self, target_node):
    if target_node in self.dependencies:
      return
    self.dependencies.add(target_node)

  def iterate_depth_first(self):
    for node in sorted(self.dependencies, key=lambda n: n.target_name):
      for node in node.iterate_depth_first():
        yield node
    if self.target_name:
      yield self


class DependencyTree(object):
  """A tree of GN build target dependencies."""

  def __init__(self):
    self.target_to_node_map = {}
    self.root = self._get_or_create_node(None)

  def _get_or_create_node(self, target_name):
    if target_name in self.target_to_node_map:
      return self.target_to_node_map[target_name]
    node = DependencyNode(target_name)
    self.target_to_node_map[target_name] = node
    return node

  def add_dependency(self, from_target, to_target):
    from_node = self._get_or_create_node(from_target)
    to_node = self._get_or_create_node(to_target)
    assert from_node is not to_node
    from_node.add_dependency(to_node)

  def iterate_depth_first(self):
    for node in self.root.iterate_depth_first():
      yield node


class AmalgamatedProject(object):
  """In-memory representation of an amalgamated source/header pair."""

  def __init__(self, desc, source_deps, compute_deps_only=False):
    """Constructor.

        Args:
            desc: JSON build description.
            source_deps: A map of (source file, [dependency header]) which is
                to detect which header files are included by each source file.
            compute_deps_only: If True, the project will only be used to compute
                dependency information. Use |get_source_files()| to retrieve
                the result.
        """
    self.desc = desc
    self.source_deps = source_deps
    self.header = []
    self.source = []
    self.source_defines = []
    # Note that we don't support multi-arg flags.
    self.cflags = set(default_cflags)
    self.ldflags = set()
    self.defines = set()
    self.libs = set()
    self._dependency_tree = DependencyTree()
    self._processed_sources = set()
    self._processed_headers = set()
    self._processed_header_deps = set()
    self._processed_source_headers = set()  # Header files included from .cc
    self._include_re = re.compile(r'#include "(.*)"')
    self._compute_deps_only = compute_deps_only

  def add_target(self, target_name):
    """Include |target_name| in the amalgamated result."""
    self._dependency_tree.add_dependency(None, target_name)
    self._add_target_dependencies(target_name)
    self._add_target_flags(target_name)
    self._add_target_headers(target_name)

    # Recurse into target deps, but only for protos. This generates headers
    # for all the .{pbzero,gen}.h files, even if they don't #include each other.
    for _, dep in self._iterate_dep_edges(target_name):
      if (dep not in self._processed_header_deps and
          re.match(recurse_in_header_deps, dep)):
        self._processed_header_deps.add(dep)
        self.add_target(dep)

  def _iterate_dep_edges(self, target_name):
    target = self.desc[target_name]
    for dep in target.get('deps', []):
      # Ignore system libraries since they will be added as build-time
      # dependencies.
      if dep in system_library_map:
        continue
      # Don't descend into build action dependencies.
      if self.desc[dep]['type'] == 'action':
        continue
      for sub_target, sub_dep in self._iterate_dep_edges(dep):
        yield sub_target, sub_dep
      yield target_name, dep

  def _iterate_target_and_deps(self, target_name):
    yield target_name
    for _, dep in self._iterate_dep_edges(target_name):
      yield dep

  def _add_target_dependencies(self, target_name):
    for target, dep in self._iterate_dep_edges(target_name):
      self._dependency_tree.add_dependency(target, dep)

    def process_dep(dep):
      if dep in system_library_map:
        self.libs.update(system_library_map[dep].get('libs', []))
        self.cflags.update(system_library_map[dep].get('cflags', []))
        self.defines.update(system_library_map[dep].get('defines', []))
        return True

    def walk_all_deps(target_name):
      target = self.desc[target_name]
      for dep in target.get('deps', []):
        if process_dep(dep):
          return
        walk_all_deps(dep)

    walk_all_deps(target_name)

  def _filter_cflags(self, cflags):
    # Since we want to deduplicate flags, combine two-part switches (e.g.,
    # "-foo bar") into one value ("-foobar") so we can store the result as
    # a set.
    result = []
    for flag in cflags:
      if flag.startswith('-'):
        result.append(flag)
      else:
        result[-1] += flag
    return apply_allowlist(cflag_allowlist, result)

  def _add_target_flags(self, target_name):
    for target_name in self._iterate_target_and_deps(target_name):
      target = self.desc[target_name]
      self.cflags.update(self._filter_cflags(target.get('cflags', [])))
      self.cflags.update(self._filter_cflags(target.get('cflags_cc', [])))
      self.ldflags.update(
          apply_allowlist(ldflag_allowlist, target.get('ldflags', [])))
      self.libs.update(apply_denylist(lib_denylist, target.get('libs', [])))
      self.defines.update(
          apply_allowlist(define_allowlist, target.get('defines', [])))

  def _add_target_headers(self, target_name):
    target = self.desc[target_name]
    if not 'sources' in target:
      return
    headers = [
        gn_utils.label_to_path(s) for s in target['sources'] if s.endswith('.h')
    ]
    for header in headers:
      self._add_header(target_name, header)

  def _get_include_dirs(self, target_name):
    include_dirs = set(default_includes)
    for target_name in self._iterate_target_and_deps(target_name):
      target = self.desc[target_name]
      if 'include_dirs' in target:
        include_dirs.update(
            [gn_utils.label_to_path(d) for d in target['include_dirs']])
    return include_dirs

  def _add_source_included_header(self, include_dirs, allowed_files,
                                  header_name):
    for include_dir in include_dirs:
      rel_path = os.path.join(include_dir, header_name)
      full_path = os.path.join(gn_utils.repo_root(), rel_path)
      if os.path.exists(full_path):
        if not rel_path in allowed_files:
          return
        if full_path in self._processed_headers:
          return
        if full_path in self._processed_source_headers:
          return
        self._processed_source_headers.add(full_path)
        with open(full_path) as f:
          self.source.append('// %s begin header: %s' %
                             (tool_name, normalize_path(full_path)))
          self.source.extend(
              self._process_source_includes(include_dirs, allowed_files, f))
        return
    if self._compute_deps_only:
      return
    msg = 'Looked in %s' % ', '.join('"%s"' % d for d in include_dirs)
    raise Error('Header file %s not found. %s' % (header_name, msg))

  def _add_source(self, target_name, source_name):
    if source_name in self._processed_sources:
      return
    self._processed_sources.add(source_name)
    include_dirs = self._get_include_dirs(target_name)
    deps = self.source_deps[source_name]
    full_path = os.path.join(gn_utils.repo_root(), source_name)
    if not os.path.exists(full_path):
      raise Error('Source file %s not found' % source_name)
    with open(full_path) as f:
      self.source.append('// %s begin source: %s' %
                         (tool_name, normalize_path(full_path)))
      try:
        self.source.extend(
            self._patch_source(
                source_name,
                self._process_source_includes(include_dirs, deps, f)))
      except Error as e:
        raise Error('Failed adding source %s: %s' % (source_name, e))

  def _add_header_included_header(self, include_dirs, header_name):
    for include_dir in include_dirs:
      full_path = os.path.join(gn_utils.repo_root(), include_dir, header_name)
      if os.path.exists(full_path):
        if full_path in self._processed_headers:
          return
        self._processed_headers.add(full_path)
        with open(full_path) as f:
          self.header.append('// %s begin header: %s' %
                             (tool_name, normalize_path(full_path)))
          self.header.extend(self._process_header_includes(include_dirs, f))
        return
    if self._compute_deps_only:
      return
    msg = 'Looked in %s' % ', '.join('"%s"' % d for d in include_dirs)
    raise Error('Header file %s not found. %s' % (header_name, msg))

  def _add_header(self, target_name, header_name):
    include_dirs = self._get_include_dirs(target_name)
    full_path = os.path.join(gn_utils.repo_root(), header_name)
    if full_path in self._processed_headers:
      return
    self._processed_headers.add(full_path)
    if not os.path.exists(full_path):
      if self._compute_deps_only:
        return
      raise Error('Header file %s not found' % header_name)
    with open(full_path) as f:
      self.header.append('// %s begin header: %s' %
                         (tool_name, normalize_path(full_path)))
      try:
        self.header.extend(self._process_header_includes(include_dirs, f))
      except Error as e:
        raise Error('Failed adding header %s: %s' % (header_name, e))

  def _patch_source(self, source_name, lines):
    result = []
    namespace = re.sub(r'[^a-z]', '_',
                       os.path.splitext(os.path.basename(source_name))[0])
    for line in lines:
      # Protobuf generates an identical anonymous function into each
      # message description. Rename all but the first occurrence to avoid
      # duplicate symbol definitions.
      line = line.replace('MergeFromFail', '%s_MergeFromFail' % namespace)
      result.append(line)
    return result

  def _process_source_includes(self, include_dirs, allowed_files, file):
    result = []
    for line in file:
      line = line.rstrip('\n')
      m = self._include_re.match(line)
      if not m:
        result.append(line)
        continue
      elif re.match(includes_to_remove, m.group(1)):
        result.append('// %s removed: %s' % (tool_name, line))
      else:
        result.append('// %s expanded: %s' % (tool_name, line))
        self._add_source_included_header(include_dirs, allowed_files,
                                         m.group(1))
    return result

  def _process_header_includes(self, include_dirs, file):
    result = []
    for line in file:
      line = line.rstrip('\n')
      m = self._include_re.match(line)
      if not m:
        result.append(line)
        continue
      elif re.match(includes_to_remove, m.group(1)):
        result.append('// %s removed: %s' % (tool_name, line))
      else:
        result.append('// %s expanded: %s' % (tool_name, line))
        self._add_header_included_header(include_dirs, m.group(1))
    return result

  def generate(self):
    """Prepares the output for this amalgamated project.

        Call save() to persist the result.
        """
    assert not self._compute_deps_only
    self.source_defines.append('// %s: predefined macros' % tool_name)

    def add_define(name):
      # Valued macros aren't supported for now.
      assert '=' not in name
      self.source_defines.append('#if !defined(%s)' % name)
      self.source_defines.append('#define %s' % name)
      self.source_defines.append('#endif')

    for name in self.defines:
      add_define(name)
    for target_name, source_name in self.get_source_files():
      self._add_source(target_name, source_name)

  def get_source_files(self):
    """Return a list of (target, [source file]) that describes the source
           files pulled in by each target which is a dependency of this project.
        """
    source_files = []
    for node in self._dependency_tree.iterate_depth_first():
      target = self.desc[node.target_name]
      if not 'sources' in target:
        continue
      sources = [(node.target_name, gn_utils.label_to_path(s))
                 for s in target['sources']
                 if s.endswith('.cc')]
      source_files.extend(sources)
    return source_files

  def _get_nice_path(self, prefix, format):
    basename = os.path.basename(prefix)
    return os.path.join(
        os.path.relpath(os.path.dirname(prefix)), format % basename)

  def _make_directories(self, directory):
    if not os.path.isdir(directory):
      os.makedirs(directory)

  def save(self, output_prefix, system_buildtools=False):
    """Save the generated header and source file pair.

        Returns a message describing the output with build instructions.
        """
    header_file = self._get_nice_path(output_prefix, '%s.h')
    source_file = self._get_nice_path(output_prefix, '%s.cc')
    self._make_directories(os.path.dirname(header_file))
    self._make_directories(os.path.dirname(source_file))
    with open(header_file, 'w') as f:
      f.write('\n'.join([preamble] + self.header + ['\n']))
    with open(source_file, 'w') as f:
      include_stmt = '#include "%s"' % os.path.basename(header_file)
      f.write('\n'.join([preamble] + self.source_defines + [include_stmt] +
                        self.source + ['\n']))
    build_cmd = self.get_build_command(output_prefix, system_buildtools)
    return """Amalgamated project written to %s and %s.

Build settings:
 - cflags:    %s
 - ldflags:   %s
 - libs:      %s

Example build command:

%s
""" % (header_file, source_file, ' '.join(self.cflags), ' '.join(
        self.ldflags), ' '.join(self.libs), ' '.join(build_cmd))

  def get_build_command(self, output_prefix, system_buildtools=False):
    """Returns an example command line for building the output source."""
    source = self._get_nice_path(output_prefix, '%s.cc')
    library = self._get_nice_path(output_prefix, 'lib%s.so')

    if sys.platform.startswith('linux') and not system_buildtools:
      llvm_script = os.path.join(gn_utils.repo_root(), 'gn', 'standalone',
                                 'toolchain', 'linux_find_llvm.py')
      cxx = subprocess.check_output([llvm_script]).splitlines()[2].decode()
    else:
      cxx = 'clang++'

    build_cmd = [cxx, source, '-o', library, '-shared'] + \
        sorted(self.cflags) + sorted(self.ldflags)
    for lib in sorted(self.libs):
      build_cmd.append('-l%s' % lib)
    return build_cmd


def main():
  parser = argparse.ArgumentParser(
      description='Generate an amalgamated header/source pair from a GN '
      'build description.')
  parser.add_argument(
      '--out',
      help='The name of the temporary build folder in \'out\'',
      default='tmp.gen_amalgamated.%u' % os.getpid())
  parser.add_argument(
      '--output',
      help='Base name of files to create. A .cc/.h extension will be added',
      default=os.path.join(gn_utils.repo_root(), 'out/amalgamated/perfetto'))
  parser.add_argument(
      '--gn_args',
      help='GN arguments used to prepare the output directory',
      default=gn_args)
  parser.add_argument(
      '--keep',
      help='Don\'t delete the GN output directory at exit',
      action='store_true')
  parser.add_argument(
      '--build', help='Also compile the generated files', action='store_true')
  parser.add_argument(
      '--check', help='Don\'t keep the generated files', action='store_true')
  parser.add_argument('--quiet', help='Only report errors', action='store_true')
  parser.add_argument(
      '--dump-deps',
      help='List all source files that the amalgamated output depends on',
      action='store_true')
  parser.add_argument(
      '--system_buildtools',
      help='Use the buildtools (e.g. gn) preinstalled in the system instead '
      'of the hermetic ones',
      action='store_true')
  parser.add_argument(
      'targets',
      nargs=argparse.REMAINDER,
      help='Targets to include in the output (e.g., "//:libperfetto")')
  args = parser.parse_args()
  targets = args.targets or default_targets

  # The CHANGELOG mtime triggers the perfetto_version.gen.h genrule. This is
  # to avoid emitting a stale version information in the remote case of somebody
  # running gen_amalgamated incrementally after having moved to another commit.
  changelog_path = os.path.join(project_root, 'CHANGELOG')
  assert (os.path.exists(changelog_path))
  subprocess.check_call(['touch', '-c', changelog_path])

  output = args.output
  if args.check:
    output = os.path.join(tempfile.mkdtemp(), 'perfetto_amalgamated')

  out = gn_utils.prepare_out_directory(args.gn_args,
                                       args.out,
                                       system_buildtools=args.system_buildtools)
  if not args.quiet:
    print('Building project...')
  try:
    desc = gn_utils.load_build_description(out, args.system_buildtools)

    # We need to build everything first so that the necessary header
    # dependencies get generated. However if we are just dumping dependency
    # information this can be skipped, allowing cross-platform operation.
    if not args.dump_deps:
      gn_utils.build_targets(out, targets,
                             system_buildtools=args.system_buildtools)
    source_deps = gn_utils.compute_source_dependencies(out,
                                                       args.system_buildtools)
    project = AmalgamatedProject(
        desc, source_deps, compute_deps_only=args.dump_deps)

    for target in targets:
      project.add_target(target)

    if args.dump_deps:
      source_files = [
          source_file for _, source_file in project.get_source_files()
      ]
      print('\n'.join(sorted(set(source_files))))
      return

    project.generate()
    result = project.save(output, args.system_buildtools)
    if not args.quiet:
      print(result)
    if args.build:
      if not args.quiet:
        sys.stdout.write('Building amalgamated project...')
        sys.stdout.flush()
      subprocess.check_call(project.get_build_command(output,
                                                      args.system_buildtools))
      if not args.quiet:
        print('done')
  finally:
    if not args.keep:
      shutil.rmtree(out)
    if args.check:
      shutil.rmtree(os.path.dirname(output))


if __name__ == '__main__':
  sys.exit(main())