'''Generate header file for nanopb from a ProtoBuf FileDescriptorSet.'''

import google.protobuf.descriptor_pb2 as descriptor
import nanopb_pb2
import os.path

# Values are tuple (c type, pb ltype)
FieldD = descriptor.FieldDescriptorProto
datatypes = {
    FieldD.TYPE_BOOL: ('bool', 'PB_LTYPE_VARINT'),
    FieldD.TYPE_DOUBLE: ('double', 'PB_LTYPE_FIXED'),
    FieldD.TYPE_FIXED32: ('uint32_t', 'PB_LTYPE_FIXED'),
    FieldD.TYPE_FIXED64: ('uint64_t', 'PB_LTYPE_FIXED'),
    FieldD.TYPE_FLOAT: ('float', 'PB_LTYPE_FIXED'),
    FieldD.TYPE_INT32: ('int32_t', 'PB_LTYPE_VARINT'),
    FieldD.TYPE_INT64: ('int64_t', 'PB_LTYPE_VARINT'),
    FieldD.TYPE_SFIXED32: ('int32_t', 'PB_LTYPE_FIXED'),
    FieldD.TYPE_SFIXED64: ('int64_t', 'PB_LTYPE_FIXED'),
    FieldD.TYPE_SINT32: ('int32_t', 'PB_LTYPE_SVARINT'),
    FieldD.TYPE_SINT64: ('int64_t', 'PB_LTYPE_SVARINT'),
    FieldD.TYPE_UINT32: ('uint32_t', 'PB_LTYPE_VARINT'),
    FieldD.TYPE_UINT64: ('uint64_t', 'PB_LTYPE_VARINT')
}

class Names:
    '''Keeps a set of nested names and formats them to C identifier.
    You can subclass this with your own implementation.
    '''
    def __init__(self, parts = ()):
        if isinstance(parts, Names):
            parts = parts.parts
        self.parts = tuple(parts)
    
    def __str__(self):
        return '_'.join(self.parts)

    def __add__(self, other):
        if isinstance(other, (str, unicode)):
            return Names(self.parts + (other,))
        elif isinstance(other, tuple):
            return Names(self.parts + other)
        else:
            raise ValueError("Name parts should be of type str")
    
def names_from_type_name(type_name):
    '''Parse Names() from FieldDescriptorProto type_name'''
    if type_name[0] != '.':
        raise NotImplementedError("Lookup of non-absolute type names is not supported")
    return Names(type_name[1:].split('.'))

class Enum:
    def __init__(self, names, desc):
        '''desc is EnumDescriptorProto'''
        self.names = names + desc.name
        self.values = [(self.names + x.name, x.number) for x in desc.value]
    
    def __str__(self):
        result = 'typedef enum {\n'
        result += ',\n'.join(["    %s = %d" % x for x in self.values])
        result += '\n} %s;' % self.names
        return result

class Field:
    def __init__(self, struct_name, desc):
        '''desc is FieldDescriptorProto'''
        self.tag = desc.number
        self.struct_name = struct_name
        self.name = desc.name
        self.default = None
        self.max_size = None
        self.max_count = None
        self.array_decl = ""
        
        # Parse nanopb-specific field options
        if desc.options.HasExtension(nanopb_pb2.nanopb):
            ext = desc.options.Extensions[nanopb_pb2.nanopb]
            if ext.HasField("max_size"):
                self.max_size = ext.max_size
            if ext.HasField("max_count"):
                self.max_count = ext.max_count
        
        if desc.HasField('default_value'):
            self.default = desc.default_value
        
        # Decide HTYPE
        # HTYPE is the high-order nibble of nanopb field description,
        # defining whether value is required/optional/repeated.
        is_callback = False
        if desc.label == FieldD.LABEL_REQUIRED:
            self.htype = 'PB_HTYPE_REQUIRED'
        elif desc.label == FieldD.LABEL_OPTIONAL:
            self.htype = 'PB_HTYPE_OPTIONAL'
        elif desc.label == FieldD.LABEL_REPEATED:
            if self.max_count is None:
                is_callback = True
            else:
                self.htype = 'PB_HTYPE_ARRAY'
                self.array_decl = '[%d]' % self.max_count
        else:
            raise NotImplementedError(desc.label)
        
        # Decide LTYPE and CTYPE
        # LTYPE is the low-order nibble of nanopb field description,
        # defining how to decode an individual value.
        # CTYPE is the name of the c type to use in the struct.
        if datatypes.has_key(desc.type):
            self.ctype, self.ltype = datatypes[desc.type]
        elif desc.type == FieldD.TYPE_ENUM:
            self.ltype = 'PB_LTYPE_VARINT'
            self.ctype = names_from_type_name(desc.type_name)
            self.default = Names(self.ctype) + self.default
        elif desc.type == FieldD.TYPE_STRING:
            self.ltype = 'PB_LTYPE_STRING'
            if self.max_size is None:
                is_callback = True
            else:
                self.ctype = 'char'
                self.array_decl += '[%d]' % self.max_size
        elif desc.type == FieldD.TYPE_BYTES:
            self.ltype = 'PB_LTYPE_BYTES'
            if self.max_size is None:
                is_callback = True
            else:
                self.ctype = self.struct_name + self.name + 't'
        elif desc.type == FieldD.TYPE_MESSAGE:
            self.ltype = 'PB_LTYPE_SUBMESSAGE'
            self.ctype = names_from_type_name(desc.type_name)
        else:
            raise NotImplementedError(desc.type)
        
        if is_callback:
            self.htype = 'PB_HTYPE_CALLBACK'
            self.ctype = 'pb_callback_t'
            self.array_decl = ''
    
    def __cmp__(self, other):
        return cmp(self.tag, other.tag)
    
    def __str__(self):
        if self.htype == 'PB_HTYPE_OPTIONAL':
            result = '    bool has_' + self.name + ';\n'
        elif self.htype == 'PB_HTYPE_ARRAY':
            result = '    size_t ' + self.name + '_count;\n'
        else:
            result = ''
        result += '    %s %s%s;' % (self.ctype, self.name, self.array_decl)
        return result
    
    def types(self):
        '''Return definitions for any special types this field might need.'''
        if self.ltype == 'PB_LTYPE_BYTES' and self.max_size is not None:
            result = 'typedef struct {\n'
            result += '    size_t size;\n'
            result += '    uint8_t bytes[%d];\n' % self.max_size
            result += '} %s;\n' % self.ctype
        else:
            result = None
        return result
    
    def default_decl(self, declaration_only = False):
        '''Return definition for this field's default value.'''
        if self.default is None:
            return None
        
        if self.ltype == 'PB_LTYPE_STRING':
            ctype = 'char'
            if self.max_size is None:
                return None # Not implemented
            else:
                array_decl = '[%d]' % self.max_size
            default = self.default.encode('string_escape')
            default = default.replace('"', '\\"')
            default = '"' + default + '"'
        elif self.ltype == 'PB_LTYPE_BYTES':
            data = self.default.decode('string_escape')
            data = ['0x%02x' % ord(c) for c in data]
            
            if self.max_size is None:
                return None # Not implemented
            else:
                ctype = self.ctype
            
            default = '{%d, {%s}}' % (len(data), ','.join(data))
            array_decl = ''
        else:
            ctype, default = self.ctype, self.default
            array_decl = ''
        
        if declaration_only:
            return 'extern const %s %s_default%s;' % (ctype, self.struct_name + self.name, array_decl)
        else:
            return 'const %s %s_default%s = %s;' % (ctype, self.struct_name + self.name, array_decl, default)
    
    def pb_field_t(self, prev_field_name):
        '''Return the pb_field_t initializer to use in the constant array.
        prev_field_name is the name of the previous field or None.
        '''
        result = '    {%d, ' % self.tag
        result += self.htype
        if self.ltype is not None:
            result += ' | ' + self.ltype
        result += ',\n'
        
        if prev_field_name is None:
            result += '    offsetof(%s, %s),' % (self.struct_name, self.name)
        else:
            result += '    pb_delta(%s, %s, %s),' % (self.struct_name, self.name, prev_field_name)
        
        if self.htype == 'PB_HTYPE_OPTIONAL':
            result += '\n    pb_delta(%s, has_%s, %s),' % (self.struct_name, self.name, self.name)
        elif self.htype == 'PB_HTYPE_ARRAY':
            result += '\n    pb_delta(%s, %s_count, %s),' % (self.struct_name, self.name, self.name)
        else:
            result += ' 0,'
        
        
        if self.htype == 'PB_HTYPE_ARRAY':
            result += '\n    pb_membersize(%s, %s[0]),' % (self.struct_name, self.name)
            result += ('\n    pb_membersize(%s, %s) / pb_membersize(%s, %s[0]),'
                       % (self.struct_name, self.name, self.struct_name, self.name))
        else:
            result += '\n    pb_membersize(%s, %s),' % (self.struct_name, self.name)
            result += ' 0,'
        
        if self.ltype == 'PB_LTYPE_SUBMESSAGE':
            result += '\n    &%s_fields}' % self.ctype
        elif self.default is None or self.htype == 'PB_HTYPE_CALLBACK':
            result += ' 0}'
        else:
            result += '\n    &%s_default}' % (self.struct_name + self.name)
        
        return result

class Message:
    def __init__(self, names, desc):
        self.name = names
        self.fields = [Field(self.name, f) for f in desc.field]
        self.ordered_fields = self.fields[:]
        self.ordered_fields.sort()
    
    def __cmp__(self, other):
        '''Sort messages so that submessages are declared before the message
        that uses them.
        '''
        if self.refers_to(other.name):
            return 1
        elif other.refers_to(self.name):
            return -1
        else:
            return 0
    
    def refers_to(self, name):
        '''Returns True if this message uses the specified type as field type.'''
        for field in self.fields:
            if str(field.ctype) == str(name):
                return True
        return False
    
    def __str__(self):
        result = 'typedef struct {\n'
        result += '\n'.join([str(f) for f in self.ordered_fields])
        result += '\n} %s;' % self.name
        return result
    
    def types(self):
        result = ""
        for field in self.fields:
            types = field.types()
            if types is not None:
                result += types + '\n'
        return result
    
    def default_decl(self, declaration_only = False):
        result = ""
        for field in self.fields:
            default = field.default_decl(declaration_only)
            if default is not None:
                result += default + '\n'
        return result

    def fields_declaration(self):
        result = 'extern const pb_field_t %s_fields[%d];' % (self.name, len(self.fields))
        return result

    def fields_definition(self):
        result = 'const pb_field_t %s_fields[%d] = {\n' % (self.name, len(self.fields))
        
        prev = None
        for field in self.ordered_fields:
            result += field.pb_field_t(prev)
            result += ',\n\n'
            prev = field.name
        
        result = result[:-3] + '\n};'
        return result

def iterate_messages(desc, names = Names()):
    '''Recursively find all messages. For each, yield name, DescriptorProto.'''
    if hasattr(desc, 'message_type'):
        submsgs = desc.message_type
    else:
        submsgs = desc.nested_type
    
    for submsg in submsgs:
        sub_names = names + submsg.name
        yield sub_names, submsg
        
        for x in iterate_messages(submsg, sub_names):
            yield x

def parse_file(fdesc):
    '''Takes a FileDescriptorProto and returns tuple (enum, messages).'''
    
    enums = []
    messages = []
    
    for enum in fdesc.enum_type:
        enums.append(Enum(Names(), enum))
    
    for names, message in iterate_messages(fdesc):
        messages.append(Message(names, message))
        for enum in message.enum_type:
            enums.append(Enum(names, enum))
    
    return enums, messages

def generate_header(headername, enums, messages):
    '''Generate content for a header file.
    Generates strings, which should be concatenated and stored to file.
    '''
    
    yield '/* Automatically generated nanopb header */\n'
    
    symbol = headername.replace('.', '_').upper()
    yield '#ifndef _PB_%s_\n' % symbol
    yield '#define _PB_%s_\n' % symbol
    yield '#include <pb.h>\n\n'
    
    yield '/* Enum definitions */\n'
    for enum in enums:
        yield str(enum) + '\n\n'
    
    yield '/* Struct definitions */\n'
    messages.sort()
    for msg in messages:
        yield msg.types()
        yield str(msg) + '\n\n'
        
    yield '/* Default values for struct fields */\n'
    for msg in messages:
        yield msg.default_decl(True)
    yield '\n'
    
    yield '/* Struct field encoding specification for nanopb */\n'
    for msg in messages:
        yield msg.fields_declaration() + '\n'
    
    yield '\n#endif\n'

def generate_source(headername, enums, messages):
    '''Generate content for a source file.'''
    
    yield '/* Automatically generated nanopb constant definitions */\n'
    yield '#include "%s"\n\n' % headername
    
    for msg in messages:
        yield msg.default_decl(False)
    
    yield '\n\n'
    
    for msg in messages:
        yield msg.fields_definition() + '\n\n'

if __name__ == '__main__':
    import sys
    import os.path
    
    if len(sys.argv) != 2:
        print "Usage: " + sys.argv[0] + " file.pb"
        print "where file.pb has been compiled from .proto by:"
        print "protoc -ofile.pb file.proto"
        print "Output fill be written to file.h and file.c"
        sys.exit(1)
    
    data = open(sys.argv[1]).read()
    fdesc = descriptor.FileDescriptorSet.FromString(data)
    enums, messages = parse_file(fdesc.file[0])
    
    noext = os.path.splitext(sys.argv[1])[0]
    headername = noext + '.h'
    sourcename = noext + '.c'
    headerbasename = os.path.basename(headername)
    
    print "Writing to " + headername + " and " + sourcename
    
    header = open(headername, 'w')
    for part in generate_header(headerbasename, enums, messages):
        header.write(part)

    source = open(sourcename, 'w')
    for part in generate_source(headerbasename, enums, messages):
        source.write(part)