#!/usr/bin/env python3

# Copyright 2023 gRPC authors.
#
# 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.

from __future__ import print_function

import collections
import ctypes
import datetime
import json
import math
import os
import re
import sys

import yaml

with open('src/core/lib/config/config_vars.yaml') as f:
    attrs = yaml.load(f.read(), Loader=yaml.FullLoader)

error = False
today = datetime.date.today()
two_quarters_from_now = today + datetime.timedelta(days=180)
for attr in attrs:
    if 'name' not in attr:
        print("config has no name: %r" % attr)
        error = True
        continue
    if 'experiment' in attr['name'] and attr['name'] != 'experiments':
        print('use experiment system for experiments')
        error = True
    if 'description' not in attr:
        print("no description for %s" % attr['name'])
        error = True
    if 'default' not in attr:
        print("no default for %s" % attr['name'])
        error = True

if error:
    sys.exit(1)


def c_str(s, encoding='ascii'):
    if s is None:
        return '""'
    if isinstance(s, str):
        s = s.encode(encoding)
    result = ''
    for c in s:
        c = chr(c) if isinstance(c, int) else c
        if not (32 <= ord(c) < 127) or c in ('\\', '"'):
            result += '\\%03o' % ord(c)
        else:
            result += c
    return '"' + result + '"'


def snake_to_pascal(s):
    return ''.join(x.capitalize() for x in s.split('_'))


# utility: print a big comment block into a set of files
def put_banner(files, banner):
    for f in files:
        for line in banner:
            print('// %s' % line, file=f)
        print(file=f)


def put_copyright(file):
    # copy-paste copyright notice from this file
    with open(sys.argv[0]) as my_source:
        copyright = []
        for line in my_source:
            if line[0] != '#':
                break
        for line in my_source:
            if line[0] == '#':
                copyright.append(line)
                break
        for line in my_source:
            if line[0] != '#':
                break
            copyright.append(line)
        put_banner([file], [line[2:].rstrip() for line in copyright])


RETURN_TYPE = {
    "int": "int32_t",
    "string": "absl::string_view",
    "bool": "bool",
}

MEMBER_TYPE = {
    "int": "int32_t",
    "string": "std::string",
    "bool": "bool",
}

SORT_ORDER_FOR_PACKING = {"int": 0, "bool": 1, "string": 2}


def bool_default_value(x, name):
    if x == True:
        return "true"
    if x == False:
        return "false"
    if isinstance(x, str) and x.startswith("$"):
        return x[1:]
    return x


def int_default_value(x, name):
    if isinstance(x, str) and x.startswith("$"):
        return x[1:]
    return x


def string_default_value(x, name):
    if x is None:
        return "\"\""
    if x.startswith("$"):
        return x[1:]
    return c_str(x)


DEFAULT_VALUE = {
    "int": int_default_value,
    "bool": bool_default_value,
    "string": string_default_value,
}

TO_STRING = {
    "int": "$",
    "bool": "$?\"true\":\"false\"",
    "string": "\"\\\"\", absl::CEscape($), \"\\\"\"",
}

attrs_in_packing_order = sorted(attrs,
                                key=lambda a: SORT_ORDER_FOR_PACKING[a['type']])

with open('src/core/lib/config/config_vars.h', 'w') as H:
    put_copyright(H)

    put_banner([H], [
        "", "Automatically generated by tools/codegen/core/gen_config_vars.py",
        ""
    ])

    print("#ifndef GRPC_SRC_CORE_LIB_CONFIG_CONFIG_VARS_H", file=H)
    print("#define GRPC_SRC_CORE_LIB_CONFIG_CONFIG_VARS_H", file=H)
    print(file=H)
    print("#include <grpc/support/port_platform.h>", file=H)
    print(file=H)
    print("#include <string>", file=H)
    print("#include <atomic>", file=H)
    print("#include <stdint.h>", file=H)
    print("#include \"absl/strings/string_view.h\"", file=H)
    print("#include \"absl/types/optional.h\"", file=H)
    print(file=H)
    print("namespace grpc_core {", file=H)
    print(file=H)
    print("class ConfigVars {", file=H)
    print(" public:", file=H)
    print("  struct Overrides {", file=H)
    for attr in attrs_in_packing_order:
        print("    absl::optional<%s> %s;" %
              (MEMBER_TYPE[attr['type']], attr['name']),
              file=H)
    print("  };", file=H)
    print("  ConfigVars(const ConfigVars&) = delete;", file=H)
    print("  ConfigVars& operator=(const ConfigVars&) = delete;", file=H)
    print("  // Get the core configuration; if it does not exist, create it.",
          file=H)
    print("  static const ConfigVars& Get() {", file=H)
    print("    auto* p = config_vars_.load(std::memory_order_acquire);", file=H)
    print("    if (p != nullptr) return *p;", file=H)
    print("    return Load();", file=H)
    print("  }", file=H)
    print("  static void SetOverrides(const Overrides& overrides);", file=H)
    print("  // Drop the config vars. Users must ensure no other threads are",
          file=H)
    print("  // accessing the configuration.", file=H)
    print("  static void Reset();", file=H)
    print("  std::string ToString() const;", file=H)
    for attr in attrs:
        for line in attr['description'].splitlines():
            print("  // %s" % line, file=H)
        if attr.get('force-load-on-access', False):
            print("  %s %s() const;" %
                  (MEMBER_TYPE[attr['type']], snake_to_pascal(attr['name'])),
                  file=H)
        else:
            print("  %s %s() const { return %s_; }" %
                  (RETURN_TYPE[attr['type']], snake_to_pascal(
                      attr['name']), attr['name']),
                  file=H)
    print(" private:", file=H)
    print("  explicit ConfigVars(const Overrides& overrides);", file=H)
    print("  static const ConfigVars& Load();", file=H)
    print("  static std::atomic<ConfigVars*> config_vars_;", file=H)
    for attr in attrs_in_packing_order:
        if attr.get('force-load-on-access', False):
            continue
        print("  %s %s_;" % (MEMBER_TYPE[attr['type']], attr['name']), file=H)
    for attr in attrs_in_packing_order:
        if attr.get('force-load-on-access', False) == False:
            continue
        print("  absl::optional<%s> override_%s_;" %
              (MEMBER_TYPE[attr['type']], attr['name']),
              file=H)
    print("};", file=H)
    print(file=H)
    print("}  // namespace grpc_core", file=H)
    print(file=H)
    print("#endif  // GRPC_SRC_CORE_LIB_CONFIG_CONFIG_VARS_H", file=H)

with open('src/core/lib/config/config_vars.cc', 'w') as C:
    put_copyright(C)

    put_banner([C], [
        "", "Automatically generated by tools/codegen/core/gen_config_vars.py",
        ""
    ])

    print("#include <grpc/support/port_platform.h>", file=C)
    print("#include \"src/core/lib/config/config_vars.h\"", file=C)
    print("#include \"src/core/lib/config/load_config.h\"", file=C)
    print("#include \"absl/strings/escaping.h\"", file=C)
    print("#include \"absl/flags/flag.h\"", file=C)
    print(file=C)

    for attr in attrs:
        if 'prelude' in attr:
            print(attr['prelude'], file=C)

    for attr in attrs:
        print("ABSL_FLAG(absl::optional<%s>, %s, absl::nullopt, %s);" %
              (MEMBER_TYPE[attr["type"]], 'grpc_' + attr['name'],
               c_str(attr['description'])),
              file=C)
    print(file=C)
    print("namespace grpc_core {", file=C)
    print(file=C)
    print("ConfigVars::ConfigVars(const Overrides& overrides) :", file=C)
    initializers = [
        "%s_(LoadConfig(FLAGS_grpc_%s, \"GRPC_%s\", overrides.%s, %s))" %
        (attr['name'], attr['name'], attr['name'].upper(), attr['name'],
         DEFAULT_VALUE[attr['type']](attr['default'], attr['name']))
        for attr in attrs_in_packing_order
        if attr.get('force-load-on-access', False) == False
    ]
    initializers += [
        "override_%s_(overrides.%s)" % (attr['name'], attr['name'])
        for attr in attrs_in_packing_order
        if attr.get('force-load-on-access', False)
    ]
    print(",".join(initializers), file=C)
    print("{}", file=C)
    print(file=C)
    for attr in attrs:
        if attr.get('force-load-on-access', False):
            print(
                "%s ConfigVars::%s() const { return LoadConfig(FLAGS_grpc_%s, \"GRPC_%s\", override_%s_, %s); }"
                % (MEMBER_TYPE[attr['type']], snake_to_pascal(attr['name']),
                   attr['name'], attr['name'].upper(), attr['name'],
                   DEFAULT_VALUE[attr['type']](attr['default'], attr['name'])),
                file=C)
            print(file=C)
    print("std::string ConfigVars::ToString() const {", file=C)
    print("  return absl::StrCat(", file=C)
    for i, attr in enumerate(attrs):
        if i:
            print(",", file=C)
            print(c_str(", " + attr['name'] + ": "), file=C)
        else:
            print(c_str(attr['name'] + ": "), file=C)
        print(",",
              TO_STRING[attr['type']].replace(
                  "$",
                  snake_to_pascal(attr['name']) + "()"),
              file=C)
    print(");}", file=C)
    print(file=C)
    print("}", file=C)
