#!/usr/bin/env python3
# -*- coding: utf-8 -*-
# Copyright 2019 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

"""Print errno table as markdown."""

from __future__ import print_function

import argparse
import os
import subprocess
import sys

import constants


# The C library header to find symbols.
HEADER = 'errno.h'

# The markdown file where we store this table.
MARKDOWN = 'errnos.md'

# The string we use to start the table header.
START_OF_TABLE = '| number |'


def find_symbols(target):
    """Find all the symbols using |target|."""
    cc = '%s-clang' % (target,)
    ret = subprocess.run([cc, '-E', '-dD', '-P', '-'],
                         input='#include <%s>\n' % (HEADER,),
                         stdout=subprocess.PIPE,
                         encoding='utf-8')
    table = {}
    for line in ret.stdout.splitlines():
        # If we need to make this smarter, signals.py handles things.
        assert not line.startswith('#undef E'), '#undef not handled'
        if line.startswith('#define E'):
            sym, val = line.strip().split()[1:3]
            assert sym not in table, 'sym %s already found' % (sym,)
            table[sym] = val
    return table


def load_table():
    """Return a table of all the symbol values (and aliases)."""
    all_tables = {}
    for target in constants.TARGETS:
        all_tables[target] = find_symbols(target)

    # Sanity check that all the tables are the same.
    basetarget = constants.TARGETS[0]
    baseline = all_tables[basetarget]
    for target, table in all_tables.items():
        assert baseline == table

    # Sometimes values have multiple names.
    aliases = {}
    for sym, val in baseline.items():
        try:
            int(val)
        except ValueError:
            aliases.setdefault(val, []).append(sym)

    return (baseline, aliases)


def sort_table(table):
    """Return a sorted table."""
    def sorter(element):
        try:
            num = int(element[1])
        except ValueError:
            num = 0
        return (num, element[0])
    return sorted(table.items(), key=sorter)


def get_md_table(table, aliases):
    """Return the table in markdown format."""
    ret = []
    last_num = 0
    for sym, val in sort_table(table):
        try:
            num = int(val)
        except ValueError:
            continue

        # Fill in holes in the table so it's obvious to the user when searching.
        for stub in range(last_num + 1, num):
            ret.append('| %i | 0x%02x | | *not implemented* ||' % (stub, stub))
        last_num = num

        desc = os.strerror(num)
        ret.append('| %i | 0x%02x | %s | %s |' % (num, num, sym, desc))
        for alias in aliases.get(sym, []):
            ret.append('| %i | 0x%02x | %s | *(Same value as %s)* %s |' %
                       (num, num, alias, sym, desc))
    return ret


def get_parser():
    """Return a command line parser."""
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument('-i', '--inplace', action='store_true',
                        help='Update the markdown file directly.')
    return parser


def main(argv):
    """The main func!"""
    parser = get_parser()
    opts = parser.parse_args(argv)

    baseline, aliases = load_table()
    md_data = get_md_table(baseline, aliases)

    if opts.inplace:
        md_file = os.path.join(os.path.dirname(os.path.abspath(__file__)),
                               MARKDOWN)
        with open(md_file) as fp:
            old_data = fp.readlines()

        i = None
        for i, line in enumerate(old_data):
            if line.startswith(START_OF_TABLE):
                break
        else:
            print('ERROR: could not find table in %s' % (md_file,),
                  file=sys.stderr)
            sys.exit(1)

        old_data = old_data[0:i + 2]
        with open(md_file, 'w') as fp:
            fp.writelines(old_data)
            fp.write('\n'.join(md_data) + '\n')
    else:
        print('\n'.join(md_data))


if __name__ == '__main__':
    sys.exit(main(sys.argv[1:]))