#!/usr/bin/env python3
# Copyright 2015 The Chromium Authors
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

# This writes headers for build flags. See buildflag_header.gni for usage of
# this system as a whole.
#
# The parameters are passed in a response file so we don't have to worry
# about command line lengths. The name of the response file is passed on the
# command line.
#
# The format of the response file is:
#    [--flags <list of one or more flag values>]

import optparse
import os
import re
import shlex


class Options:
    def __init__(self, output, rulename, header_guard, flags):
        self.output = output
        self.rulename = rulename
        self.header_guard = header_guard
        self.flags = flags


def GetOptions():
    parser = optparse.OptionParser()
    parser.add_option('--output', help="Output header name inside --gen-dir.")
    parser.add_option(
        '--rulename',
        help="Helpful name of build rule for including in the "
        + "comment at the top of the file.",
    )
    parser.add_option(
        '--gen-dir', help="Path to root of generated file directory tree."
    )
    parser.add_option(
        '--definitions', help="Name of the response file containing the flags."
    )
    cmdline_options, cmdline_flags = parser.parse_args()

    # Compute a valid C++ header guard by replacing non valid chars with '_',
    # upper-casing everything and prepending '_' if first symbol is digit.
    header_guard = cmdline_options.output.upper()
    if header_guard[0].isdigit():
        header_guard = '_' + header_guard
    header_guard = re.sub(r'[^\w]', '_', header_guard)
    header_guard += '_'

    # The actual output file is inside the gen dir.
    output = os.path.join(cmdline_options.gen_dir, cmdline_options.output)

    # Definition file in GYP is newline separated, in GN they are shell formatted.
    # shlex can parse both of these.
    with open(cmdline_options.definitions, 'r') as def_file:
        defs = shlex.split(def_file.read())
    flags_index = defs.index('--flags')

    # Everything after --flags are flags. true/false are remapped to 1/0,
    # everything else is passed through.
    flags = []
    for flag in defs[flags_index + 1 :]:
        equals_index = flag.index('=')
        key = flag[:equals_index]
        value = flag[equals_index + 1 :]

        # Canonicalize and validate the value.
        if value == 'true':
            value = '1'
        elif value == 'false':
            value = '0'
        flags.append((key, str(value)))

    return Options(
        output=output,
        rulename=cmdline_options.rulename,
        header_guard=header_guard,
        flags=flags,
    )


def WriteHeader(options):
    with open(options.output, 'w') as output_file:
        output_file.write("// Generated by build/write_buildflag_header.py\n")
        if options.rulename:
            output_file.write('// From "' + options.rulename + '"\n')

        output_file.write('\n#ifndef %s\n' % options.header_guard)
        output_file.write('#define %s\n\n' % options.header_guard)
        output_file.write(
            '#include "build/buildflag.h" // IWYU pragma: export\n\n'
        )
        # Clangd does not detect BUILDFLAG_INTERNAL_* indirect usage, so mark the
        # header as "always_keep" to avoid "unused include" warning.
        output_file.write('// IWYU pragma: always_keep\n\n')

        for pair in options.flags:
            output_file.write('#define BUILDFLAG_INTERNAL_%s() (%s)\n' % pair)

        output_file.write('\n#endif  // %s\n' % options.header_guard)


options = GetOptions()
WriteHeader(options)