FeatherMC/src/protocol/generate_protocol.py

import hjson
import sys

text = ''

def add_text(fmt, *args):
    global text
    text += (fmt + '\n').format(*args)

def resolve_type(aliases, type):
    if type in aliases:
        return aliases[type]
    return type

def print_states(states):
    add_text('    enum class ProtocolState : int32_t')
    add_text('    {{')
    for state, value in states.items():
        add_text('        {} = {},', state, value)
    add_text('    }};')

def get_rw_func(primitiveType, aliasedType, read):
    prefix = 'Read' if read else 'Write'
    if aliasedType == 'varint':
        if primitiveType == 'int32_t':
            return '{}VarInt'.format(prefix)    
        else:
            return '{}VarInt<{}>'.format(prefix, primitiveType)
    elif aliasedType == 'string':
        return '{}String'.format(prefix)
    else:
        return 'Read<{}>'.format(aliasedType)

def print_messages(list, aliases, primitives, serverbound):
    global text
    for message_name, message in list.items():
        add_text('    struct {}Message', message_name)
        add_text('    {{')
        add_text('        static constexpr int32_t PacketId = {};', message['id'])
        add_text('        static constexpr bool ServerBound = {};', 'true' if serverbound else 'false')
        add_text('        static constexpr ProtocolState PacketState = ProtocolState::{};', message['state'])
        add_text('')
        if serverbound:
            add_text('        {}Message(PacketReader& reader)', message_name)
            add_text('        {{')
            for name, type in message['vars'].items():
                add_text('            {} = reader.{}();', name, get_rw_func(resolve_type(primitives, type), resolve_type(aliases, type), True))
            add_text('        }}')
            add_text('')

        for name, type in message['vars'].items():
            add_text('        {} {};', resolve_type(primitives, type), name)
        
        add_text('    }};')
        add_text('')

def print_protocol():
    with open(sys.argv[1]) as message_file:
        message_scheme = hjson.load(message_file)

        print_states(message_scheme['states'])

        add_text('')

        print_messages(
            message_scheme['messages']['serverbound'],
            message_scheme['types']['aliases'],
            message_scheme['types']['primitives'],
            True)

def main():
    if len(sys.argv) != 3:
        print('Usage: generate_protocol.py <input: protocol.hjson> <output: ProtocolDefinitions.h>')
        return

    add_text('#pragma once')
    add_text('')
    add_text('#include <cstdint>')
    add_text('#include "PacketReader.h"')
    add_text('')
    add_text('namespace Feather')
    add_text('{{')
    print_protocol()
    add_text('}}')
    add_text('')

    with open(sys.argv[2], 'w') as out_file:
        out_file.write(text)
        out_file.close()

main()