#!/usr/bin/env python3
# flake8: noqa: E501

import argparse
import json
import subprocess
import sys

from dataclasses import (
    dataclass,
)
from pathlib import Path

# Helper first so it is defined when other functions call it.
from typing import Any, Literal

SCHEMA_VERSION = "2025-06-18"
JSONRPC_VERSION = "2.0"

STANDARD_DERIVE = "#[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]\n"
STANDARD_HASHABLE_DERIVE = (
    "#[derive(Debug, Clone, PartialEq, Deserialize, Serialize, Hash, Eq)]\n"
)

# Will be populated with the schema's `definitions` map in `main()` so that
# helper functions (for example `define_any_of`) can perform look-ups while
# generating code.
DEFINITIONS: dict[str, Any] = {}
# Names of the concrete *Request types that make up the ClientRequest enum.
CLIENT_REQUEST_TYPE_NAMES: list[str] = []
# Concrete *Notification types that make up the ServerNotification enum.
SERVER_NOTIFICATION_TYPE_NAMES: list[str] = []
# Enum types that will need a `allow(clippy::large_enum_variant)` annotation in
# order to compile without warnings.
LARGE_ENUMS = {"ServerResult"}


def main() -> int:
    parser = argparse.ArgumentParser(
        description="Embed, cluster and analyse text prompts via the OpenAI API.",
    )

    default_schema_file = (
        Path(__file__).resolve().parent / "schema" / SCHEMA_VERSION / "schema.json"
    )
    parser.add_argument(
        "schema_file",
        nargs="?",
        default=default_schema_file,
        help="schema.json file to process",
    )
    args = parser.parse_args()
    schema_file = args.schema_file

    lib_rs = Path(__file__).resolve().parent / "src/lib.rs"

    global DEFINITIONS  # Allow helper functions to access the schema.

    with schema_file.open(encoding="utf-8") as f:
        schema_json = json.load(f)

    DEFINITIONS = schema_json["definitions"]

    out = [
        f"""
// @generated
// DO NOT EDIT THIS FILE DIRECTLY.
// Run the following in the crate root to regenerate this file:
//
// ```shell
// ./generate_mcp_types.py
// ```
use serde::Deserialize;
use serde::Serialize;
use serde::de::DeserializeOwned;
use std::convert::TryFrom;

pub const MCP_SCHEMA_VERSION: &str = "{SCHEMA_VERSION}";
pub const JSONRPC_VERSION: &str = "{JSONRPC_VERSION}";

/// Paired request/response types for the Model Context Protocol (MCP).
pub trait ModelContextProtocolRequest {{
    const METHOD: &'static str;
    type Params: DeserializeOwned + Serialize + Send + Sync + 'static;
    type Result: DeserializeOwned + Serialize + Send + Sync + 'static;
}}

/// One-way message in the Model Context Protocol (MCP).
pub trait ModelContextProtocolNotification {{
    const METHOD: &'static str;
    type Params: DeserializeOwned + Serialize + Send + Sync + 'static;
}}

fn default_jsonrpc() -> String {{ JSONRPC_VERSION.to_owned() }}

"""
    ]
    definitions = schema_json["definitions"]
    # Keep track of every *Request type so we can generate the TryFrom impl at
    # the end.
    # The concrete *Request types referenced by the ClientRequest enum will be
    # captured dynamically while we are processing that definition.
    for name, definition in definitions.items():
        add_definition(name, definition, out)
    # No-op: list collected via define_any_of("ClientRequest").

    # Generate TryFrom impl string and append to out before writing to file.
    try_from_impl_lines: list[str] = []
    try_from_impl_lines.append("impl TryFrom<JSONRPCRequest> for ClientRequest {\n")
    try_from_impl_lines.append("    type Error = serde_json::Error;\n")
    try_from_impl_lines.append(
        "    fn try_from(req: JSONRPCRequest) -> std::result::Result<Self, Self::Error> {\n"
    )
    try_from_impl_lines.append("        match req.method.as_str() {\n")

    for req_name in CLIENT_REQUEST_TYPE_NAMES:
        defn = definitions[req_name]
        method_const = (
            defn.get("properties", {}).get("method", {}).get("const", req_name)
        )
        payload_type = f"<{req_name} as ModelContextProtocolRequest>::Params"
        try_from_impl_lines.append(f'            "{method_const}" => {{\n')
        try_from_impl_lines.append(
            "                let params_json = req.params.unwrap_or(serde_json::Value::Null);\n"
        )
        try_from_impl_lines.append(
            f"                let params: {payload_type} = serde_json::from_value(params_json)?;\n"
        )
        try_from_impl_lines.append(
            f"                Ok(ClientRequest::{req_name}(params))\n"
        )
        try_from_impl_lines.append("            },\n")

    try_from_impl_lines.append(
        '            _ => Err(serde_json::Error::io(std::io::Error::new(std::io::ErrorKind::InvalidData, format!("Unknown method: {}", req.method)))),\n'
    )
    try_from_impl_lines.append("        }\n")
    try_from_impl_lines.append("    }\n")
    try_from_impl_lines.append("}\n\n")

    out.extend(try_from_impl_lines)

    # Generate TryFrom for ServerNotification
    notif_impl_lines: list[str] = []
    notif_impl_lines.append(
        "impl TryFrom<JSONRPCNotification> for ServerNotification {\n"
    )
    notif_impl_lines.append("    type Error = serde_json::Error;\n")
    notif_impl_lines.append(
        "    fn try_from(n: JSONRPCNotification) -> std::result::Result<Self, Self::Error> {\n"
    )
    notif_impl_lines.append("        match n.method.as_str() {\n")

    for notif_name in SERVER_NOTIFICATION_TYPE_NAMES:
        n_def = definitions[notif_name]
        method_const = (
            n_def.get("properties", {}).get("method", {}).get("const", notif_name)
        )
        payload_type = f"<{notif_name} as ModelContextProtocolNotification>::Params"
        notif_impl_lines.append(f'            "{method_const}" => {{\n')
        # params may be optional
        notif_impl_lines.append(
            "                let params_json = n.params.unwrap_or(serde_json::Value::Null);\n"
        )
        notif_impl_lines.append(
            f"                let params: {payload_type} = serde_json::from_value(params_json)?;\n"
        )
        notif_impl_lines.append(
            f"                Ok(ServerNotification::{notif_name}(params))\n"
        )
        notif_impl_lines.append("            },\n")

    notif_impl_lines.append(
        '            _ => Err(serde_json::Error::io(std::io::Error::new(std::io::ErrorKind::InvalidData, format!("Unknown method: {}", n.method)))),\n'
    )
    notif_impl_lines.append("        }\n")
    notif_impl_lines.append("    }\n")
    notif_impl_lines.append("}\n")

    out.extend(notif_impl_lines)

    with open(lib_rs, "w", encoding="utf-8") as f:
        for chunk in out:
            f.write(chunk)

    subprocess.check_call(
        ["cargo", "fmt", "--", "--config", "imports_granularity=Item"],
        cwd=lib_rs.parent.parent,
        stderr=subprocess.DEVNULL,
    )

    return 0


def add_definition(name: str, definition: dict[str, Any], out: list[str]) -> None:
    if name == "Result":
        out.append("pub type Result = serde_json::Value;\n\n")
        return

    # Capture description
    description = definition.get("description")

    properties = definition.get("properties", {})
    if properties:
        required_props = set(definition.get("required", []))
        out.extend(define_struct(name, properties, required_props, description))

        # Special carve-out for Result types:
        if name.endswith("Result"):
            out.extend(f"impl From<{name}> for serde_json::Value {{\n")
            out.append(f"    fn from(value: {name}) -> Self {{\n")
            out.append("        // Leave this as it should never fail\n")
            out.append("        #[expect(clippy::unwrap_used)]\n")
            out.append("        serde_json::to_value(value).unwrap()\n")
            out.append("    }\n")
            out.append("}\n\n")
        return

    enum_values = definition.get("enum", [])
    if enum_values:
        assert definition.get("type") == "string"
        define_string_enum(name, enum_values, out, description)
        return

    any_of = definition.get("anyOf", [])
    if any_of:
        assert isinstance(any_of, list)
        out.extend(define_any_of(name, any_of, description))
        return

    type_prop = definition.get("type", None)
    if type_prop:
        if type_prop == "string":
            # Newtype pattern
            out.append(STANDARD_DERIVE)
            out.append(f"pub struct {name}(String);\n\n")
            return
        elif types := check_string_list(type_prop):
            define_untagged_enum(name, types, out)
            return
        elif type_prop == "array":
            item_name = name + "Item"
            out.extend(define_any_of(item_name, definition["items"]["anyOf"]))
            out.append(f"pub type {name} = Vec<{item_name}>;\n\n")
            return
        raise ValueError(f"Unknown type: {type_prop} in {name}")

    ref_prop = definition.get("$ref", None)
    if ref_prop:
        ref = type_from_ref(ref_prop)
        out.extend(f"pub type {name} = {ref};\n\n")
        return

    raise ValueError(f"Definition for {name} could not be processed.")


extra_defs = []


@dataclass
class StructField:
    viz: Literal["pub"] | Literal["const"]
    name: str
    type_name: str
    serde: str | None = None

    def append(self, out: list[str], supports_const: bool) -> None:
        if self.serde:
            out.append(f"    {self.serde}\n")
        if self.viz == "const":
            if supports_const:
                out.append(f"    const {self.name}: {self.type_name};\n")
            else:
                out.append(f"    pub {self.name}: String, // {self.type_name}\n")
        else:
            out.append(f"    pub {self.name}: {self.type_name},\n")


def define_struct(
    name: str,
    properties: dict[str, Any],
    required_props: set[str],
    description: str | None,
) -> list[str]:
    out: list[str] = []

    fields: list[StructField] = []
    for prop_name, prop in properties.items():
        if prop_name == "_meta":
            # TODO?
            continue
        elif prop_name == "jsonrpc":
            fields.append(
                StructField(
                    "pub",
                    "jsonrpc",
                    "String",  # cannot use `&'static str` because of Deserialize
                    '#[serde(rename = "jsonrpc", default = "default_jsonrpc")]',
                )
            )
            continue

        prop_type = map_type(prop, prop_name, name)
        is_optional = prop_name not in required_props
        if is_optional:
            prop_type = f"Option<{prop_type}>"
        rs_prop = rust_prop_name(prop_name, is_optional)
        if prop_type.startswith("&'static str"):
            fields.append(StructField("const", rs_prop.name, prop_type, rs_prop.serde))
        else:
            fields.append(StructField("pub", rs_prop.name, prop_type, rs_prop.serde))

    if implements_request_trait(name):
        add_trait_impl(name, "ModelContextProtocolRequest", fields, out)
    elif implements_notification_trait(name):
        add_trait_impl(name, "ModelContextProtocolNotification", fields, out)
    else:
        # Add doc comment if available.
        emit_doc_comment(description, out)
        out.append(STANDARD_DERIVE)
        out.append(f"pub struct {name} {{\n")
        for field in fields:
            field.append(out, supports_const=False)
        out.append("}\n\n")

    # Declare any extra structs after the main struct.
    if extra_defs:
        out.extend(extra_defs)
        # Clear the extra structs for the next definition.
        extra_defs.clear()
    return out


def infer_result_type(request_type_name: str) -> str:
    """Return the corresponding Result type name for a given *Request name."""
    if not request_type_name.endswith("Request"):
        return "Result"  # fallback
    candidate = request_type_name[:-7] + "Result"
    if candidate in DEFINITIONS:
        return candidate
    # Fallback to generic Result if specific one missing.
    return "Result"


def implements_request_trait(name: str) -> bool:
    return name.endswith("Request") and name not in (
        "Request",
        "JSONRPCRequest",
        "PaginatedRequest",
    )


def implements_notification_trait(name: str) -> bool:
    return name.endswith("Notification") and name not in (
        "Notification",
        "JSONRPCNotification",
    )


def add_trait_impl(
    type_name: str, trait_name: str, fields: list[StructField], out: list[str]
) -> None:
    out.append(STANDARD_DERIVE)
    out.append(f"pub enum {type_name} {{}}\n\n")

    out.append(f"impl {trait_name} for {type_name} {{\n")
    for field in fields:
        if field.name == "method":
            field.name = "METHOD"
            field.append(out, supports_const=True)
        elif field.name == "params":
            out.append(f"    type Params = {field.type_name};\n")
        else:
            print(f"Warning: {type_name} has unexpected field {field.name}.")
    if trait_name == "ModelContextProtocolRequest":
        result_type = infer_result_type(type_name)
        out.append(f"    type Result = {result_type};\n")
    out.append("}\n\n")


def define_string_enum(
    name: str, enum_values: Any, out: list[str], description: str | None
) -> None:
    emit_doc_comment(description, out)
    out.append(STANDARD_DERIVE)
    out.append(f"pub enum {name} {{\n")
    for value in enum_values:
        assert isinstance(value, str)
        out.append(f'    #[serde(rename = "{value}")]\n')
        out.append(f"    {capitalize(value)},\n")

    out.append("}\n\n")
    return out


def define_untagged_enum(name: str, type_list: list[str], out: list[str]) -> None:
    out.append(STANDARD_HASHABLE_DERIVE)
    out.append("#[serde(untagged)]\n")
    out.append(f"pub enum {name} {{\n")
    for simple_type in type_list:
        match simple_type:
            case "string":
                out.append("    String(String),\n")
            case "integer":
                out.append("    Integer(i64),\n")
            case _:
                raise ValueError(
                    f"Unknown type in untagged enum: {simple_type} in {name}"
                )
    out.append("}\n\n")


def define_any_of(
    name: str, list_of_refs: list[Any], description: str | None = None
) -> list[str]:
    """Generate a Rust enum for a JSON-Schema `anyOf` union.

    For most types we simply map each `$ref` inside the `anyOf` list to a
    similarly named enum variant that holds the referenced type as its
    payload. For certain well-known composite types (currently only
    `ClientRequest`) we need a little bit of extra intelligence:

    * The JSON shape of a request is `{ "method": <string>, "params": <object?> }`.
    * We want to deserialize directly into `ClientRequest` using Serde's
      `#[serde(tag = "method", content = "params")]` representation so that
      the enum payload is **only** the request's `params` object.
    * Therefore each enum variant needs to carry the dedicated `…Params` type
      (wrapped in `Option<…>` if the `params` field is not required), not the
      full `…Request` struct from the schema definition.
    """

    # Verify each item in list_of_refs is a dict with a $ref key.
    refs = [item["$ref"] for item in list_of_refs if isinstance(item, dict)]

    out: list[str] = []
    if description:
        emit_doc_comment(description, out)
    out.append(STANDARD_DERIVE)

    if serde := get_serde_annotation_for_anyof_type(name):
        out.append(serde + "\n")

    if name in LARGE_ENUMS:
        out.append("#[allow(clippy::large_enum_variant)]\n")
    out.append(f"pub enum {name} {{\n")

    if name == "ClientRequest":
        # Record the set of request type names so we can later generate a
        # `TryFrom<JSONRPCRequest>` implementation.
        global CLIENT_REQUEST_TYPE_NAMES
        CLIENT_REQUEST_TYPE_NAMES = [type_from_ref(r) for r in refs]

    if name == "ServerNotification":
        global SERVER_NOTIFICATION_TYPE_NAMES
        SERVER_NOTIFICATION_TYPE_NAMES = [type_from_ref(r) for r in refs]

    for ref in refs:
        ref_name = type_from_ref(ref)

        # For JSONRPCMessage variants, drop the common "JSONRPC" prefix to
        # make the enum easier to read (e.g. `Request` instead of
        # `JSONRPCRequest`). The payload type remains unchanged.
        variant_name = (
            ref_name[len("JSONRPC") :]
            if name == "JSONRPCMessage" and ref_name.startswith("JSONRPC")
            else ref_name
        )

        # Special-case for `ClientRequest` and `ServerNotification` so the enum
        # variant's payload is the *Params type rather than the full *Request /
        # *Notification marker type.
        if name in ("ClientRequest", "ServerNotification"):
            # Rely on the trait implementation to tell us the exact Rust type
            # of the `params` payload. This guarantees we stay in sync with any
            # special-case logic used elsewhere (e.g. objects with
            # `additionalProperties` mapping to `serde_json::Value`).
            if name == "ClientRequest":
                payload_type = f"<{ref_name} as ModelContextProtocolRequest>::Params"
            else:
                payload_type = (
                    f"<{ref_name} as ModelContextProtocolNotification>::Params"
                )

            # Determine the wire value for `method` so we can annotate the
            # variant appropriately. If for some reason the schema does not
            # specify a constant we fall back to the type name, which will at
            # least compile (although deserialization will likely fail).
            request_def = DEFINITIONS.get(ref_name, {})
            method_const = (
                request_def.get("properties", {})
                .get("method", {})
                .get("const", ref_name)
            )

            out.append(f'    #[serde(rename = "{method_const}")]\n')
            out.append(f"    {variant_name}({payload_type}),\n")
        else:
            # The regular/straight-forward case.
            out.append(f"    {variant_name}({ref_name}),\n")

    out.append("}\n\n")
    return out


def get_serde_annotation_for_anyof_type(type_name: str) -> str | None:
    # TODO: Solve this in a more generic way.
    match type_name:
        case "ClientRequest":
            return '#[serde(tag = "method", content = "params")]'
        case "ServerNotification":
            return '#[serde(tag = "method", content = "params")]'
        case _:
            return "#[serde(untagged)]"


def map_type(
    typedef: dict[str, any],
    prop_name: str | None = None,
    struct_name: str | None = None,
) -> str:
    """typedef must have a `type` key, but may also have an `items`key."""
    ref_prop = typedef.get("$ref", None)
    if ref_prop:
        return type_from_ref(ref_prop)

    any_of = typedef.get("anyOf", None)
    if any_of:
        assert prop_name is not None
        assert struct_name is not None
        custom_type = struct_name + capitalize(prop_name)
        extra_defs.extend(define_any_of(custom_type, any_of))
        return custom_type

    type_prop = typedef.get("type", None)
    if type_prop is None:
        # Likely `unknown` in TypeScript, like the JSONRPCError.data property.
        return "serde_json::Value"

    if type_prop == "string":
        if const_prop := typedef.get("const", None):
            assert isinstance(const_prop, str)
            return f'&\'static str = "{const_prop    }"'
        else:
            return "String"
    elif type_prop == "integer":
        return "i64"
    elif type_prop == "number":
        return "f64"
    elif type_prop == "boolean":
        return "bool"
    elif type_prop == "array":
        item_type = typedef.get("items", None)
        if item_type:
            item_type = map_type(item_type, prop_name, struct_name)
            assert isinstance(item_type, str)
            return f"Vec<{item_type}>"
        else:
            raise ValueError("Array type without items.")
    elif type_prop == "object":
        # If the schema says `additionalProperties: {}` this is effectively an
        # open-ended map, so deserialize into `serde_json::Value` for maximum
        # flexibility.
        if typedef.get("additionalProperties") is not None:
            return "serde_json::Value"

        # If there are *no* properties declared treat it similarly.
        if not typedef.get("properties"):
            return "serde_json::Value"

        # Otherwise, synthesize a nested struct for the inline object.
        assert prop_name is not None
        assert struct_name is not None
        custom_type = struct_name + capitalize(prop_name)
        extra_defs.extend(
            define_struct(
                custom_type,
                typedef["properties"],
                set(typedef.get("required", [])),
                typedef.get("description"),
            )
        )
        return custom_type
    else:
        raise ValueError(f"Unknown type: {type_prop} in {typedef}")


@dataclass
class RustProp:
    name: str
    # serde annotation, if necessary
    serde: str | None = None


def rust_prop_name(name: str, is_optional: bool) -> RustProp:
    """Convert a JSON property name to a Rust property name."""
    prop_name: str
    is_rename = False
    if name == "type":
        prop_name = "r#type"
    elif name == "ref":
        prop_name = "r#ref"
    elif name == "enum":
        prop_name = "r#enum"
    elif snake_case := to_snake_case(name):
        prop_name = snake_case
        is_rename = True
    else:
        prop_name = name

    serde_annotations = []
    if is_rename:
        serde_annotations.append(f'rename = "{name}"')
    if is_optional:
        serde_annotations.append("default")
        serde_annotations.append('skip_serializing_if = "Option::is_none"')

    if serde_annotations:
        serde_str = f'#[serde({", ".join(serde_annotations)})]'
    else:
        serde_str = None
    return RustProp(prop_name, serde_str)


def to_snake_case(name: str) -> str:
    """Convert a camelCase or PascalCase name to snake_case."""
    snake_case = name[0].lower() + "".join(
        "_" + c.lower() if c.isupper() else c for c in name[1:]
    )
    if snake_case != name:
        return snake_case
    else:
        return None


def capitalize(name: str) -> str:
    """Capitalize the first letter of a name."""
    return name[0].upper() + name[1:]


def check_string_list(value: Any) -> list[str] | None:
    """If the value is a list of strings, return it. Otherwise, return None."""
    if not isinstance(value, list):
        return None
    for item in value:
        if not isinstance(item, str):
            return None
    return value


def type_from_ref(ref: str) -> str:
    """Convert a JSON reference to a Rust type."""
    assert ref.startswith("#/definitions/")
    return ref.split("/")[-1]


def emit_doc_comment(text: str | None, out: list[str]) -> None:
    """Append Rust doc comments derived from the JSON-schema description."""
    if not text:
        return
    for line in text.strip().split("\n"):
        out.append(f"/// {line.rstrip()}\n")


if __name__ == "__main__":
    sys.exit(main())
