# Copyright (c) Microsoft Corporation. All rights reserved.
# Licensed under the MIT License.

import collections
import copy
import itertools
import keyword
import pathlib
import re
from typing import Dict, List, Optional, OrderedDict, Sequence, Tuple, Union

import generator.model as model

METHOD_NAME_RE_1 = re.compile(r"(.)([A-Z][a-z]+)")
METHOD_NAME_RE_2 = re.compile(r"([a-z0-9])([A-Z])")
PACKAGE_NAME = "lsprotocol"

# These are special type aliases to preserve backward compatibility.
CUSTOM_REQUEST_PARAMS_ALIASES = []

# Special enums with duplicates
SPECIAL_ENUMS = ["LanguageKind", "ErrorCodes", "LSPErrorCodes"]


def customizations(spec: model.LSPModel) -> model.LSPModel:
    # https://github.com/microsoft/lsprotocol/issues/344
    # Allow CompletionItemKind to support custom values
    for enum in spec.enumerations:
        if enum.name == "CompletionItemKind":
            enum.supportsCustomValues = True
            break

    return spec


def generate_from_spec(spec: model.LSPModel, output_dir: str, test_dir: str) -> None:
    spec = customizations(spec)
    code = TypesCodeGenerator(spec).get_code()

    output_path = pathlib.Path(output_dir, PACKAGE_NAME)
    if not output_path.exists():
        output_path.mkdir(parents=True, exist_ok=True)

    for file_name in code:
        (output_path / file_name).write_text(code[file_name], encoding="utf-8")


def _generate_field_validator(
    type_def: model.LSP_TYPE_SPEC, optional: bool = False
) -> str:
    """Generates attrs.field validator for a given field base of type."""

    if type_def.kind == "base":
        if type_def.name == "integer":
            validator = "validators.integer_validator"
        elif type_def.name == "uinteger":
            validator = "validators.uinteger_validator"
        elif type_def.name in ["string", "DocumentUri", "URI", "Uri"]:
            validator = "attrs.validators.instance_of(str)"
        elif type_def.name == "boolean":
            validator = "attrs.validators.instance_of(bool)"
        elif type_def.name == "decimal":
            validator = "attrs.validators.instance_of(float)"
        else:
            validator = None
    elif type_def.kind == "stringLiteral":
        return f"attrs.field(validator=attrs.validators.in_(['{type_def.value}']), default='{type_def.value}')"
    else:
        validator = None

    if optional:
        if validator:
            return f"attrs.field(validator=attrs.validators.optional({validator}), default=None)"
        else:
            return "attrs.field(default=None)"
    else:
        if validator:
            return f"attrs.field(validator={validator})"
        else:
            return "attrs.field()"


def _to_class_name(lsp_method_name: str) -> str:
    """Convert from LSP method name (e.g., textDocument/didSave) to python class name
    (e.g., TextDocumentDidSave)"""
    name = lsp_method_name[2:] if lsp_method_name.startswith("$/") else lsp_method_name
    name = name.replace("/", "_")
    name = METHOD_NAME_RE_1.sub(r"\1_\2", name)
    name = METHOD_NAME_RE_2.sub(r"\1_\2", name)
    return "".join(part.title() for part in name.split("_"))


def _get_class_name(obj: Union[model.Request, model.Notification]) -> str:
    if obj.typeName:
        return obj.typeName
    return _to_class_name(obj.method)


def lines_to_str(lines: Union[Sequence[str], List[str]]) -> str:
    return "\n".join(lines)


def _sanitize_comment(text: str) -> str:
    """LSP spec comments can contain newlines or characters that should not be used or
    can cause issues with python code clean them up."""
    return " ".join(text.splitlines())


def _is_special_field(prop: model.Property) -> bool:
    """Detect if the field requires special handling when serialising."""
    return prop.type.kind == "stringLiteral" or _has_null_base_type(prop)


def _has_null_base_type(prop: model.Property) -> bool:
    """Detect if the type is indirectly optional."""
    if prop.type.kind == "or":
        # If one of the types in the item list is a `null` then that means the
        # field can be None. So we can treat that field as optional.
        return any(t.kind == "base" and t.name == "null" for t in prop.type.items)
    else:
        return False


def _to_snake_case(name: str) -> str:
    new_name = METHOD_NAME_RE_1.sub(r"\1_\2", name)
    new_name = METHOD_NAME_RE_2.sub(r"\1_\2", new_name)
    new_name = new_name.lower()
    return f"{new_name}_" if keyword.iskeyword(new_name) else new_name


def _snake_case_item_name(original: str) -> str:
    """Generate snake case names from LSP definition names.

    Example:
    * PlainText -> PLAIN_TEXT
    * $import -> IMPORT
    """
    new_name = original
    if new_name.startswith("$"):
        new_name = new_name[1:]
    if new_name.startswith("/"):
        new_name = new_name[1:]
    new_name = new_name.replace("/", "_")
    new_name = re.sub("(.)([A-Z][a-z]+)", r"\1_\2", new_name)
    new_name = re.sub("([a-z0-9])([A-Z])", r"\1_\2", new_name)
    return f"{new_name}_" if keyword.iskeyword(new_name) else new_name


def _capitalized_item_name(original: str) -> str:
    """Generate capitalized names from LSP definition names.

    Example:
    * someClass -> SomeClass
    * some_class -> SomeClass
    """
    parts = _snake_case_item_name(original).split("_")
    new_name = "".join(x.title() for x in parts)
    return f"{new_name}_" if keyword.iskeyword(new_name) else new_name


def _get_indented_documentation(
    documentation: Optional[str], indent: str = ""
) -> Optional[str]:
    """Clean up doc string from LSP model and word wrap with correct indent level."""
    doc = (
        indent.join(documentation.splitlines(keepends=True)) if documentation else None
    )
    if doc:
        doc = doc.replace("**​/*", "**/*").replace("∕", "/")
        doc = doc[:-2] if doc.endswith("*/") else doc
        doc = doc.strip()
        doc = re.sub(r"\[(?P<class>[A-Za-z]*)\]\(\#(?P=class)\)", r"\1", doc)
        doc = re.sub(r"\[(?P<class>[\S]*)(\[\])\]\(\#(?P=class)\)", r"\1\2", doc)
        doc = re.sub(r"\[([\w\ ]+)\]\(\#[\w\.]+\)", r"\1", doc)
    return doc


def _get_since(
    spec: Union[
        model.Structure,
        model.Property,
        model.Enum,
        model.EnumItem,
        model.LiteralType,
        model.TypeAlias,
        model.Notification,
        model.Request,
    ],
    indent: str = "",
) -> List[str]:
    if spec.sinceTags:
        lines = [f"{indent}# Since:"]
        for tag in spec.sinceTags:
            lines.append(f"{indent}# {_sanitize_comment(tag)}")
        return lines
    if spec.since:
        return [f"{indent}# Since: {_sanitize_comment(spec.since)}"]
    return []


class TypesCodeGenerator:
    def __init__(self, lsp_model: model.LSPModel):
        self._lsp_model = lsp_model
        self._reset()

    def _reset(self):
        self._types: OrderedDict[str, List[str]] = collections.OrderedDict()
        self._imports: List[str] = [
            "import enum",
            "import functools",
            "from typing import Any, Dict, Mapping, Literal, Optional, Sequence, Tuple, Union",
            "import attrs",
            "from . import validators",
        ]
        self._keyword_classes: List[str] = []
        self._special_classes: List[str] = []
        self._special_properties: List[str] = []

    def _add_keyword_class(self, class_name) -> None:
        if class_name not in self._keyword_classes:
            self._keyword_classes.append(class_name)

    def _get_imports(self) -> List[str]:
        return self._imports

    def _get_header(self) -> List[str]:
        return [
            "# Copyright (c) Microsoft Corporation. All rights reserved.",
            "# Licensed under the MIT License.",
            "",
            "# ****** THIS IS A GENERATED FILE, DO NOT EDIT. ******",
            "# Steps to generate:",
            "# 1. Checkout https://github.com/microsoft/lsprotocol",
            "# 2. Install nox: `python -m pip install nox`",
            "# 3. Run command: `python -m nox --session build_lsp`",
            "",
        ]

    def get_code(self) -> Dict[str, str]:
        self._reset()
        self._generate_code(self._lsp_model)

        code_lines = (
            self._get_header()
            + self._get_imports()
            + self._get_meta_data(self._lsp_model)
            + self._get_types_code()
            + self._get_utility_code(self._lsp_model)
        )
        return {
            "types.py": lines_to_str(code_lines),
        }

    def _get_custom_value_type(self, ref_name: str) -> Optional[str]:
        """Returns the custom supported type."""
        try:
            enum_def = [e for e in self._lsp_model.enumerations if e.name == ref_name][
                0
            ]
        except IndexError:
            enum_def = None
        if enum_def and enum_def.supportsCustomValues:
            if enum_def.type.name == "string":
                return "str"
            if enum_def.type.name in ["integer", "uinteger"]:
                return "int"
        return None

    def _generate_type_name(
        self,
        type_def: model.LSP_TYPE_SPEC,
        class_name: Optional[str] = None,
        prefix: str = "",
    ) -> str:
        """Get typing wrapped type name based on LSP type definition."""

        if type_def.kind == "stringLiteral":
            # These are string constants used in some LSP types.
            # TODO: Use this with python >= 3.8
            # return f"Literal['{type_def.value}']"
            return "str"

        if type_def.kind == "literal":
            # A general type 'Any' has no properties
            if (
                isinstance(type_def.value, model.LiteralValue)
                and len(type_def.value.properties) == 0
            ):
                return "Any"

            # The literal kind is a dynamically generated type and the
            # name for it is generated as needed. It is expected that when
            # this function is called name is set.
            if type_def.name:
                return f"'{type_def.name}'"

            # If name is missing, and there are properties then it is a dynamic
            # type. It should have already been generated.
            raise ValueError(str(type_def))

        if type_def.kind == "reference":
            # The reference kind is a named type which is part of LSP.
            if self._has_type(type_def.name):
                ref_type = f"{prefix}{type_def.name}"
            else:
                # We don't have this type yet. Make it a forward reference.
                ref_type = f"'{prefix}{type_def.name}'"
            custom_value_type = self._get_custom_value_type(type_def.name)
            if custom_value_type:
                return f"Union[{ref_type}, {custom_value_type}]"

            return ref_type

        if type_def.kind == "array":
            # This is a linear collection type, LSP does not specify if
            # this needs to be ordered. Also, usingList here because
            # cattrs does not work well withIterable for some reason.
            return f"Sequence[{self._generate_type_name(type_def.element, class_name, prefix)}]"

        if type_def.kind == "or":
            # This type means that you can have either of the types under `items`
            # as the value. So, from typing point of view this is a union. The `or`
            # type means it is going to be one of the types, never both (see `and`)
            # Example:
            # id :Union[str, int]
            #     * This means that id can either be string or integer, cannot be both.
            types = []
            for item in type_def.items:
                types.append(self._generate_type_name(item, class_name, prefix))
            return f"Union[{','.join(types)}]"

        if type_def.kind == "and":
            # This type means that the value has properties of all the types under
            # `items`. This type is equivalent of `class C(A, B)`. Where A and B are
            # defined in `items`. This type should be generated separately, here we
            # return the optionally provided class for this.
            if not class_name:
                raise ValueError(str(type_def))
            return class_name

        if type_def.kind == "base":
            # The `base` kind is used for primitive data types.
            if type_def.name == "decimal":
                return "float"
            elif type_def.name == "boolean":
                return "bool"
            elif type_def.name in ["integer", "uinteger"]:
                return "int"
            elif type_def.name in ["string", "DocumentUri", "URI"]:
                return "str"
            elif type_def.name == "null":
                return "None"
            else:
                # Unknown base kind.
                raise ValueError(str(type_def))

        if type_def.kind == "map":
            # This kind defines a dictionary like object.
            return f"Mapping[{self._generate_type_name(type_def.key, class_name, prefix)}, {self._generate_type_name(type_def.value, class_name, prefix)}]"

        if type_def.kind == "tuple":
            # This kind defined a tuple like object.
            types = []
            for item in type_def.items:
                types.append(self._generate_type_name(item, class_name, prefix))
            return f"Tuple[{','.join(types)}]"

        raise ValueError(str(type_def))

    def _add_special(self, class_name: str, properties: List[str]) -> None:
        if properties:
            self._special_classes.append(class_name)
            self._special_properties.extend([f"'{class_name}.{p}'" for p in properties])

    def _get_types_code(self) -> List[str]:
        code_lines = []
        for v in self._types.values():
            code_lines.extend(v)
            # Add blank lines between types
            code_lines.extend(["", ""])

        return code_lines

    def _add_import(self, import_line: str) -> None:
        if import_line not in self._imports:
            self._imports.append(import_line)

    def _has_type(self, type_name: str) -> bool:
        if type_name.startswith(('"', "'")):
            type_name = type_name[1:-1]
        return type_name in self._types

    def _get_additional_methods(self, class_name: str) -> List[str]:
        indent = " " * 4
        if class_name == "Position":
            return [
                "def __eq__(self, o: object) -> bool:",
                f"{indent}if not isinstance(o, Position):",
                f"{indent}{indent}return NotImplemented",
                f"{indent}return (self.line, self.character) == (o.line, o.character)",
                "def __gt__(self, o: 'Position') -> bool:",
                f"{indent}if not isinstance(o, Position):",
                f"{indent}{indent}return NotImplemented",
                f"{indent}return (self.line, self.character) > (o.line, o.character)",
                "def __repr__(self) -> str:",
                f"{indent}" + "return f'{self.line}:{self.character}'",
            ]
        if class_name == "Range":
            return [
                "def __eq__(self, o: object) -> bool:",
                f"{indent}if not isinstance(o, Range):",
                f"{indent}{indent}return NotImplemented",
                f"{indent}return (self.start == o.start) and (self.end == o.end)",
                "def __repr__(self) -> str:",
                f"{indent}" + "return f'{self.start!r}-{self.end!r}'",
            ]
        if class_name == "Location":
            return [
                "def __eq__(self, o: object) -> bool:",
                f"{indent}if not isinstance(o, Location):",
                f"{indent}{indent}return NotImplemented",
                f"{indent}return (self.uri == o.uri) and (self.range == o.range)",
                "def __repr__(self) -> str:",
                f"{indent}" + "return f'{self.uri}:{self.range!r}'",
            ]
        return None

    def _add_type_code(self, type_name: str, code: List[str]) -> None:
        if not self._has_type(type_name):
            self._types[type_name] = code
            self._types.move_to_end(type_name)

    def _add_enum(self, enum_def: model.Enum) -> None:
        code_lines = [
            "" if enum_def.name in SPECIAL_ENUMS else "@enum.unique",
        ]
        if enum_def.type.name == "string":
            code_lines += [f"class {enum_def.name}(str, enum.Enum):"]
        elif enum_def.type.name in ["integer", "uinteger"]:
            code_lines += [f"class {enum_def.name}(int, enum.Enum):"]
        else:
            code_lines += [f"class {enum_def.name}(enum.Enum):"]

        indent = " " * 4
        doc = _get_indented_documentation(enum_def.documentation, indent)
        code_lines += [f'{indent}"""{doc}"""' if enum_def.documentation else ""]
        code_lines += _get_since(enum_def, indent)
        code_lines += [f"{indent}# Proposed" if enum_def.proposed else ""]

        # Remove unnecessary empty lines
        code_lines = [code for code in code_lines if len(code) > 0]

        for item in enum_def.values:
            name = _capitalized_item_name(item.name)
            value = (
                f'"{item.value}"' if enum_def.type.name == "string" else f"{item.value}"
            )
            doc = _get_indented_documentation(item.documentation, indent)
            item_lines = [
                f"{indent}{name} = {value}",
                f'{indent}"""{doc}"""' if item.documentation else "",
            ]
            item_lines += _get_since(item, indent)
            item_lines += [f"{indent}# Proposed" if item.proposed else ""]

            # Remove unnecessary empty lines.
            code_lines += [code for code in item_lines if len(code) > 0]

        self._add_type_code(enum_def.name, code_lines)

    def _add_enums(self, lsp_model: model.LSPModel) -> None:
        for enum_def in lsp_model.enumerations:
            self._add_enum(enum_def)

    def _process_literal_types(
        self, class_name: str, type_def: model.LSP_TYPE_SPEC
    ) -> None:
        if type_def.kind == "literal" and len(type_def.value.properties) > 0:
            type_def.name = type_def.name or _to_class_name(f"{class_name}_Type")
            self._add_literal_type(type_def)
        elif type_def.kind == "or":
            count = itertools.count(1)
            for sub_type in type_def.items or []:
                try:
                    # Anonymous types have no name so generate a name. We append `_Type#`
                    # to generate the name, where `#` is a number.
                    sub_type.name = sub_type.name or _to_class_name(
                        f"{class_name}_Type{next(count)}"
                    )
                except AttributeError:
                    pass
                self._process_literal_types(class_name, sub_type)
        elif type_def.kind == "array":
            try:
                type_def.element.name = type_def.element.name or _to_class_name(
                    f"{class_name}_Type"
                )
            except AttributeError:
                pass
            self._process_literal_types(class_name, type_def.element)
        elif type_def.kind == "and":
            raise ValueError(str(type_def))
        else:
            pass

    def _generate_properties(
        self, class_name: str, properties: List[model.Property], indent: str
    ) -> List[str]:
        code_lines = []

        # Ensure that we mark any property as optional if it supports None type.
        # We only need to do this for properties not explicitly marked as optional.
        for p in properties:
            if not p.optional:
                p.optional = _has_null_base_type(p)

        # sort properties so that you have non-optional properties first then optional properties
        properties = [
            p for p in properties if not (p.optional or p.type.kind == "stringLiteral")
        ] + [p for p in properties if p.optional or p.type.kind == "stringLiteral"]

        for property_def in properties:
            self._process_literal_types(
                f"{class_name}/{property_def.name}", property_def.type
            )

            doc = _get_indented_documentation(property_def.documentation, indent)
            type_validator = _generate_field_validator(
                property_def.type, property_def.optional
            )

            type_name = self._generate_type_name(property_def.type)
            if property_def.optional:
                type_name = f"Optional[{type_name}]"

            # make sure that property name is not a python keyword and snake cased.
            name = _to_snake_case(property_def.name)

            prop_lines = [f"{indent}{name}: {type_name} = {type_validator}"]
            prop_lines += [f'{indent}"""{doc}"""' if property_def.documentation else ""]
            prop_lines += _get_since(property_def, indent)
            prop_lines += [f"{indent}# Proposed" if property_def.proposed else ""]

            # Remove unnecessary empty lines and add a single empty line
            code_lines += [code for code in prop_lines if len(code) > 0] + [""]

        return code_lines

    def _add_literal_type(self, literal_def: model.LiteralType) -> None:
        if self._has_type(literal_def.name):
            return

        # indent level for use with fields, doc string, and comments.
        indent = " " * 4

        # clean up the docstring for the class itself.
        doc = _get_indented_documentation(literal_def.documentation, indent)

        # Code here should include class, its doc string, and any comments.
        code_lines = [
            "@attrs.define",
            f"class {literal_def.name}:",
            f'{indent}"""{doc}"""' if literal_def.documentation else "",
        ]
        code_lines += _get_since(literal_def, indent)
        code_lines += [f"{indent}# Proposed" if literal_def.proposed else ""]

        # Remove unnecessary empty lines. This can happen if doc string or comments are missing.
        code_lines = [code for code in code_lines if len(code) > 0]

        code_lines += self._generate_properties(
            literal_def.name, literal_def.value.properties, indent
        )

        self._add_type_code(literal_def.name, code_lines)

        if any(keyword.iskeyword(p.name) for p in literal_def.value.properties):
            self._add_keyword_class(literal_def.name)

        self._add_special(
            literal_def.name,
            [
                _to_snake_case(p.name)
                for p in literal_def.value.properties
                if _is_special_field(p)
            ],
        )

    def _add_type_alias(self, type_alias: model.TypeAlias) -> None:
        # TypeAlias definition can contain anonymous types as a part of its
        # definition. We generate them here first before we get to defile the
        # TypeAlias.
        indent = " " * 4
        count = itertools.count(1)
        if type_alias.type.kind == "or":
            for sub_type in type_alias.type.items or []:
                if sub_type.kind == "literal":
                    # Anonymous types have no name so generate a name. We append `_Type#`
                    # to generate the name, where `#` is a number.
                    sub_type.name = (
                        sub_type.name or f"{type_alias.name}_Type{next(count)}"
                    )
                    self._add_literal_type(sub_type)

        if type_alias.name == "LSPAny":
            type_name = "Union[Any, None]"
        elif type_alias.name == "LSPObject":
            type_name = None
        else:
            type_name = self._generate_type_name(type_alias.type)
        if type_alias.type.kind == "reference" and not self._has_type(
            type_alias.type.name
        ):
            # TODO: remove workaround for lack of TypeAlias
            type_name = f"Union[{type_name}, {type_name}]"

        if type_name:
            # clean up the docstring for the class itself.
            doc = _get_indented_documentation(type_alias.documentation)
            code_lines = [
                f"{type_alias.name} = {type_name}",
                f'"""{doc}"""' if type_alias.documentation else "",
            ]
            code_lines += _get_since(type_alias, indent)
            code_lines += ["# Proposed" if type_alias.proposed else ""]
        else:
            doc = _get_indented_documentation(type_alias.documentation, indent)
            code_lines = [
                f"class {type_alias.name}:",
                f'{indent}"""{doc}"""' if type_alias.documentation else "",
            ]
            code_lines += _get_since(type_alias, indent)
            code_lines += [
                f"{indent}# Proposed" if type_alias.proposed else "",
                f"{indent}pass",
            ]
        code_lines = [code for code in code_lines if len(code) > 0]

        self._add_type_code(type_alias.name, code_lines)

    def _add_type_aliases(self, lsp_model: model.LSPModel) -> None:
        for type_def in lsp_model.typeAliases:
            self._add_type_alias(type_def)

    def _get_dependent_types(
        self,
        struct_def: model.Structure,
        lsp_model: model.LSPModel,
    ) -> List[model.Structure]:
        # `extends` and `mixins` both are used as classes from which the
        # current class to derive from.
        extends = struct_def.extends or []
        mixins = struct_def.mixins or []

        definitions: List[model.Structure] = []
        for s in extends + mixins:
            for t in lsp_model.structures:
                if t.name == s.name and s.kind == "reference":
                    definitions.append(t)
                    definitions.extend(self._get_dependent_types(t, lsp_model))

        result: List[model.Structure] = []
        for d in definitions:
            if d.name in [r.name for r in result]:
                pass
            else:
                result.append(d)
        return result

    def _add_structure(
        self,
        struct_def: model.Structure,
        lsp_model: model.LSPModel,
    ) -> None:
        if self._has_type(struct_def.name):
            return

        definitions = self._get_dependent_types(struct_def, lsp_model)
        for d in definitions:
            self._add_structure(d, lsp_model)

        indent = "" if struct_def.name == "LSPObject" else " " * 4
        doc = _get_indented_documentation(struct_def.documentation, indent)
        class_name = struct_def.name

        class_lines = [
            "" if class_name == "LSPObject" else "@attrs.define",
            "@functools.total_ordering" if class_name == "Position" else "",
            f"{class_name} = object"
            if class_name == "LSPObject"
            else f"class {class_name}:",
            f'{indent}"""{doc}"""' if struct_def.documentation else "",
        ]
        class_lines += _get_since(struct_def, indent)
        class_lines += [
            f"{indent}# Proposed" if struct_def.proposed else "",
        ]

        # Remove unnecessary empty lines and add a single empty line
        code_lines = [code for code in class_lines if len(code) > 0] + [""]

        # Inheriting from multiple classes can cause problems especially when using
        # `attrs.define`.
        properties = copy.deepcopy(struct_def.properties)
        extra_properties = []
        for d in definitions:
            extra_properties += copy.deepcopy(d.properties)

        for p in extra_properties:
            prop_names = [prop.name for prop in properties]
            if p.name not in prop_names:
                properties += [copy.deepcopy(p)]

        code_lines += self._generate_properties(class_name, properties, indent)
        methods = self._get_additional_methods(class_name)

        # If the class has no properties then add `pass`
        if len(properties) == 0 and not methods and class_name != "LSPObject":
            code_lines += [f"{indent}pass"]

        if methods:
            code_lines += [f"{indent}{method}" for method in methods]

        # Detect if the class has properties that might be keywords.
        self._add_type_code(class_name, code_lines)

        if any(keyword.iskeyword(p.name) for p in properties):
            self._add_keyword_class(class_name)

        self._add_special(
            class_name,
            [_to_snake_case(p.name) for p in properties if _is_special_field(p)],
        )

    def _add_structures(self, lsp_model: model.LSPModel) -> None:
        for struct_def in lsp_model.structures:
            self._add_structure(struct_def, lsp_model)

    def _add_and_type(
        self,
        type_def: model.LSP_TYPE_SPEC,
        class_name: str,
        structures: List[model.Structure],
    ) -> Tuple[List[str], List[str]]:
        if type_def.kind != "and":
            raise ValueError("Only `and` type code generation is supported.")

        indent = " " * 4
        code_lines = [
            "@attrs.define",
            f"class {class_name}:",
        ]

        properties = []
        for item in type_def.items:
            if item.kind == "reference":
                for structure in structures:
                    if structure.name == item.name:
                        properties += copy.deepcopy(structure.properties)
            else:
                raise ValueError(
                    "Only `reference` types are supported for `and` type generation."
                )

        code_lines += self._generate_properties(class_name, properties, indent)

        self._add_type_code(class_name, code_lines)
        if any(keyword.iskeyword(p.name) for p in properties):
            self._add_keyword_class(class_name)

        self._add_special(
            class_name,
            [_to_snake_case(p.name) for p in properties if _is_special_field(p)],
        )

    def _add_and_types(self, lsp_model: model.LSPModel) -> None:
        # Collect all and types in the model from known locations
        and_types = []
        for request in lsp_model.requests:
            if request.params:
                if request.params.kind == "and":
                    class_name = f"{_get_class_name(request)}Params"
                    and_types.append((f"{class_name}", request.params))

            if request.registrationOptions:
                if request.registrationOptions.kind == "and":
                    class_name = f"{_get_class_name(request)}Options"
                    and_types.append((f"{class_name}", request.registrationOptions))

        for notification in lsp_model.notifications:
            if notification.params:
                if notification.params.kind == "and":
                    class_name = f"{_get_class_name(notification)}Params"
                    and_types.append((f"{class_name}", notification.params))

            if notification.registrationOptions:
                if notification.registrationOptions.kind == "and":
                    class_name = f"{_get_class_name(notification)}Options"
                    and_types.append(
                        (f"{class_name}", notification.registrationOptions)
                    )

        for name, type_def in and_types:
            self._add_and_type(type_def, name, lsp_model.structures)

    def _add_requests(self, lsp_mode: model.LSPModel) -> None:
        indent = " " * 4

        self._add_type_code(
            "ResponseError",
            [
                "@attrs.define",
                "class ResponseError:",
                f"{indent}code: int = attrs.field(validator=validators.integer_validator)",
                f'{indent}"""A number indicating the error type that occurred."""',
                f"{indent}message: str = attrs.field(validator=attrs.validators.instance_of(str))",
                f'{indent}"""A string providing a short description of the error."""',
                f"{indent}data:Optional[LSPAny] = attrs.field(default=None)",
                f'{indent}"""A primitive or structured value that contains additional information',
                f'{indent}about the error. Can be omitted."""',
            ],
        )

        self._add_type_code(
            "ResponseErrorMessage",
            [
                "@attrs.define",
                "class ResponseErrorMessage:",
                f"{indent}id:Optional[Union[int, str]] = attrs.field(default=None)",
                f'{indent}"""The request id where the error occurred."""',
                f"{indent}error:Optional[ResponseError] = attrs.field(default=None)",
                f'{indent}"""The error object in case a request fails."""',
                f'{indent}jsonrpc: str = attrs.field(default="2.0")',
            ],
        )

        self._add_special("ResponseErrorMessage", ["error", "jsonrpc"])

        for request in lsp_mode.requests:
            class_name = _get_class_name(request)
            if not class_name.endswith("Request"):
                class_name += "Request"
            class_name_part = class_name.replace("Request", "")

            doc = _get_indented_documentation(request.documentation, indent)

            params_class_name = f"{class_name_part}Params"
            if request.params:
                if (
                    request.params.kind == "reference"
                    and {params_class_name} in CUSTOM_REQUEST_PARAMS_ALIASES
                ):
                    params_type = params_class_name

                    self._add_type_alias(
                        model.TypeAlias(
                            name=params_type,
                            type={"kind": "reference", "name": request.params.name},
                        )
                    )
                else:
                    params_type = self._generate_type_name(
                        request.params, params_class_name
                    )
                if not self._has_type(params_type):
                    raise ValueError(f"{params_class_name} type definition is missing.")
                params_field = "attrs.field()"
            else:
                params_type = "Optional[None]"
                params_field = "attrs.field(default=None)"

            result_type = None
            result_class_name = f"{class_name_part}Result"
            if request.result:
                if request.result.kind == "reference" or (
                    request.result.kind == "base" and request.result.name == "null"
                ):
                    result_type = self._generate_type_name(request.result)
                else:
                    is_optional = request.result.kind == "or" and any(
                        t.kind == "base" and t.name == "null"
                        for t in request.result.items
                    )
                    result_type = (
                        f"Optional[{result_class_name}]"
                        if is_optional
                        else result_class_name
                    )
                    self._add_type_alias(
                        model.TypeAlias(
                            name=result_class_name,
                            type=request.result,
                        )
                    )

                result_field = "attrs.field(default=None)"
            else:
                result_type = "Optional[None]"
                result_field = "attrs.field(default=None)"

            self._add_type_code(
                class_name,
                [
                    "@attrs.define",
                    f"class {class_name}:",
                    f'{indent}"""{doc}"""' if request.documentation else "",
                    f"{indent}id:Union[int, str] = attrs.field()",
                    f'{indent}"""The request id."""',
                    f"{indent}params: {params_type} ={params_field}",
                    f'{indent}method: Literal["{request.method}"] = "{request.method}"',
                    f'{indent}"""The method to be invoked."""',
                    f'{indent}jsonrpc: str = attrs.field(default="2.0")',
                ],
            )
            self._add_special(class_name, ["method", "jsonrpc"])

            response_class_name = f"{class_name_part}Response"
            self._add_type_code(
                response_class_name,
                [
                    "@attrs.define",
                    f"class {response_class_name}:",
                    f"{indent}id:Optional[Union[int, str]] = attrs.field()",
                    f'{indent}"""The request id."""',
                    f"{indent}result: {result_type} = {result_field}",
                    f'{indent}jsonrpc: str = attrs.field(default="2.0")',
                ],
            )
            self._add_special(response_class_name, ["result", "jsonrpc"])

    def _add_notifications(self, lsp_mode: model.LSPModel) -> None:
        indent = " " * 4

        for notification in lsp_mode.notifications:
            class_name = _get_class_name(notification)
            if not class_name.endswith("Notification"):
                class_name += "Notification"

            doc = _get_indented_documentation(notification.documentation, indent)

            if notification.params:
                params_type = self._generate_type_name(
                    notification.params, f"{class_name}Params"
                )
                if not self._has_type(params_type):
                    raise ValueError(f"{class_name}Params type definition is missing.")
                params_field = "attrs.field()"
            else:
                params_type = "Optional[None]"
                params_field = "attrs.field(default=None)"

            self._add_type_code(
                class_name,
                [
                    "@attrs.define",
                    f"class {class_name}:",
                    f'{indent}"""{doc}"""' if notification.documentation else "",
                    f"{indent}params: {params_type} = {params_field}",
                    f'{indent}method: Literal["{notification.method}"] = attrs.field(',
                    f'validator=attrs.validators.in_(["{notification.method}"]),',
                    f'default="{notification.method}",',
                    ")",
                    f'{indent}"""The method to be invoked."""',
                    f'{indent}jsonrpc: str = attrs.field(default="2.0")',
                ],
            )
            self._add_special(class_name, ["method", "jsonrpc"])

    def _add_lsp_method_type(self, lsp_model: model.LSPModel) -> None:
        indent = " " * 4
        directions = set(
            [x.messageDirection for x in (lsp_model.requests + lsp_model.notifications)]
        )
        code_lines = [
            "@enum.unique",
            "class MessageDirection(enum.Enum):",
        ]
        code_lines += sorted(
            [f"{indent}{_capitalized_item_name(m)} = '{m}'" for m in directions]
        )
        self._add_type_code("MessageDirection", code_lines)

    def _add_special_types(self, lsp_model: model.LSPModel) -> None:
        # Ensure LSPObject gets added first.
        # Try and find it in the type aliases
        lsp_object = list(
            filter(
                lambda s: s.name == "LSPObject",
                [*lsp_model.typeAliases, *lsp_model.structures],
            )
        )

        if len(lsp_object) == 0:
            raise ValueError("LSPObject type definition is missing.")
        elif len(lsp_object) > 1:
            raise ValueError("LSPObject type definition is duplicated.")
        else:
            if isinstance(lsp_object[0], model.TypeAlias):
                self._add_type_alias(lsp_object[0])
            elif isinstance(lsp_object[0], model.Structure):
                self._add_structure(lsp_object[0], lsp_model)
            else:
                raise ValueError("LSPObject type definition is invalid.")

    def _generate_code(self, lsp_model: model.LSPModel) -> None:
        self._add_enums(lsp_model)
        self._add_special_types(lsp_model)
        self._add_type_aliases(lsp_model)
        self._add_structures(lsp_model)
        self._add_and_types(lsp_model)
        self._add_requests(lsp_model)
        self._add_notifications(lsp_model)
        self._add_lsp_method_type(lsp_model)

    def _get_utility_code(self, lsp_model: model.LSPModel) -> List[str]:
        request_classes = []
        response_classes = []
        notification_classes = []

        methods = set(
            [x.method for x in (lsp_model.requests + lsp_model.notifications)]
        )
        code_lines = (
            [""]
            + sorted([f"{_snake_case_item_name(m).upper()} = '{m}'" for m in methods])
            + [""]
        )

        code_lines += ["METHOD_TO_TYPES = {", "    # Requests"]

        request_types = []
        for request in lsp_model.requests:
            class_name = _get_class_name(request)
            if not class_name.endswith("Request"):
                class_name += "Request"
            class_name_part = class_name.replace("Request", "")
            request_class = f"{class_name_part}Request"
            response_class = f"{class_name_part}Response"

            request_classes.append(request_class)
            response_classes.append(response_class)

            params_type = None
            if request.params:
                params_type = self._generate_type_name(
                    request.params, f"{class_name}Params"
                ).strip("\"'")

            registration_type = None
            if request.registrationOptions:
                registration_type = self._generate_type_name(
                    request.registrationOptions, f"{class_name}Options"
                ).strip("\"'")

            key = f"{_snake_case_item_name(request.method).upper()}"
            request_types += [
                f"{key}: ({request_class}, {response_class}, {params_type}, {registration_type}),"
            ]

        code_lines += sorted(request_types)
        code_lines += ["    # Notifications"]

        notify_types = []
        for notification in lsp_model.notifications:
            class_name = _get_class_name(notification)
            if not class_name.endswith("Notification"):
                class_name += "Notification"
            notification_class = class_name
            notification_classes.append(notification_class)

            params_type = None
            if notification.params:
                params_type = self._generate_type_name(
                    notification.params, f"{class_name}Params"
                ).strip("\"'")

            registration_type = None
            if notification.registrationOptions:
                registration_type = self._generate_type_name(
                    notification.registrationOptions, f"{class_name}Options"
                ).strip("\"'")

            key = f"{_snake_case_item_name(notification.method).upper()}"
            notify_types += [
                f"{key}: ({notification_class}, None, {params_type}, {registration_type}),"
            ]

        code_lines += sorted(notify_types)
        code_lines += ["}"]

        code_lines += [
            f"REQUESTS = Union[{', '.join(sorted(request_classes))}]",
            f"RESPONSES = Union[{', '.join(sorted(response_classes))}]",
            f"NOTIFICATIONS = Union[{', '.join(sorted(notification_classes))}]",
            "MESSAGE_TYPES = Union[REQUESTS, RESPONSES, NOTIFICATIONS, ResponseErrorMessage]",
            "",
        ]

        # These classes have properties that may be python keywords.
        code_lines += [
            f"_KEYWORD_CLASSES = [{', '.join(sorted(set(self._keyword_classes)))}]"
        ]
        code_lines += [
            "def is_keyword_class(cls: type) -> bool:",
            '    """Returns true if the class has a property that may be python keyword."""',
            "    return any(cls is c for c in _KEYWORD_CLASSES)",
            "",
        ]

        # These are classes that have properties that need special handling
        # during serialization of the class based on LSP.
        # See: https://github.com/microsoft/vscode-languageserver-node/issues/967
        code_lines += [
            f"_SPECIAL_CLASSES = [{', '.join(sorted(set(self._special_classes)))}]"
        ]
        code_lines += [
            "def is_special_class(cls: type) -> bool:",
            '    """Returns true if the class or its properties require special handling."""',
            "    return any(cls is c for c in _SPECIAL_CLASSES)",
            "",
        ]

        # This is a collection of `class_name.property` as string. These properties
        # need special handling as described by LSP>
        # See: https://github.com/microsoft/vscode-languageserver-node/issues/967
        #
        # Example:
        #   Consider RenameRegistrationOptions
        #     * document_selector property:
        #         When you set `document_selector` to None in python it has to be preserved when
        #         serializing it. Since the serialized JSON value `{"document_selector": null}`
        #         means use the Clients document selector. Omitting it might throw error.
        #     * prepare_provider property
        #         This property does NOT need special handling, since omitting it or using
        #         `{"prepare_provider": null}` has the same meaning.
        code_lines += [
            f"_SPECIAL_PROPERTIES = [{', '.join(sorted(set(self._special_properties)))}]"
        ]
        code_lines += [
            "def is_special_property(cls: type, property_name:str) -> bool:",
            '    """Returns true if the class or its properties require special handling.',
            "    Example:",
            "      Consider RenameRegistrationOptions",
            "        * document_selector property:",
            "            When you set `document_selector` to None in python it has to be preserved when",
            '            serializing it. Since the serialized JSON value `{"document_selector": null}`',
            "            means use the Clients document selector. Omitting it might throw error. ",
            "        * prepare_provider property",
            "            This property does NOT need special handling, since omitting it or using",
            '            `{"prepare_provider": null}` in JSON has the same meaning.',
            '    """',
            '    qualified_name = f"{cls.__name__}.{property_name}"',
            "    return qualified_name in _SPECIAL_PROPERTIES",
            "",
        ]

        code_lines += ["", "ALL_TYPES_MAP: Dict[str, Union[type, object]] = {"]
        code_lines += sorted([f"'{name}': {name}," for name in set(self._types.keys())])
        code_lines += ["}", ""]

        code_lines += ["_MESSAGE_DIRECTION: Dict[str, str] = {"]

        code_lines += ["# Request methods"]
        code_lines += sorted(
            [
                f'{_snake_case_item_name(r.method).upper()}:"{r.messageDirection}",'
                for r in lsp_model.requests
            ]
        )
        code_lines += ["# Notification methods"]
        code_lines += sorted(
            [
                f'{_snake_case_item_name(n.method).upper()}:"{n.messageDirection}",'
                for n in lsp_model.notifications
            ]
        )

        code_lines += ["}", ""]

        code_lines += [
            "def message_direction(method:str) -> str:",
            '    """Returns message direction clientToServer, serverToClient or both."""',
            "    return _MESSAGE_DIRECTION[method]",
            "",
        ]

        return code_lines

    def _get_meta_data(self, lsp_model: model.LSPModel) -> List[str]:
        return [f"__lsp_version__ = '{lsp_model.metaData.version}'"]