/*---------------------------------------------------------------------------------------------
 *  Copyright (c) Microsoft Corporation. All rights reserved.
 *--------------------------------------------------------------------------------------------*/

/**
 * Python code generator for session-events and RPC types.
 */

import fs from "fs/promises";
import type { JSONSchema7 } from "json-schema";
import { FetchingJSONSchemaStore, InputData, JSONSchemaInput, quicktype } from "quicktype-core";
import {
    cloneSchemaForCodegen,
    getApiSchemaPath,
    getRpcSchemaTypeName,
    getSessionEventsSchemaPath,
    hoistTitledSchemas,
    isObjectSchema,
    isVoidSchema,
    isRpcMethod,
    postProcessSchema,
    writeGeneratedFile,
    isNodeFullyExperimental,
    type ApiSchema,
    type RpcMethod,
} from "./utils.js";

// ── Utilities ───────────────────────────────────────────────────────────────

/**
 * Modernize quicktype's Python 3.7 output to Python 3.11+ syntax:
 * - Optional[T] → T | None
 * - List[T] → list[T]
 * - Dict[K, V] → dict[K, V]
 * - Type[T] → type[T]
 * - Callable from collections.abc instead of typing
 * - Clean up unused typing imports
 */
function replaceBalancedBrackets(code: string, prefix: string, replacer: (inner: string) => string): string {
    let result = "";
    let i = 0;
    while (i < code.length) {
        const idx = code.indexOf(prefix + "[", i);
        if (idx === -1) {
            result += code.slice(i);
            break;
        }
        result += code.slice(i, idx);
        const start = idx + prefix.length + 1; // after '['
        let depth = 1;
        let j = start;
        while (j < code.length && depth > 0) {
            if (code[j] === "[") depth++;
            else if (code[j] === "]") depth--;
            j++;
        }
        const inner = code.slice(start, j - 1);
        result += replacer(inner);
        i = j;
    }
    return result;
}

/** Split a string by commas, but only at the top bracket depth (ignores commas inside [...]) */
function splitTopLevelCommas(s: string): string[] {
    const parts: string[] = [];
    let depth = 0;
    let start = 0;
    for (let i = 0; i < s.length; i++) {
        if (s[i] === "[") depth++;
        else if (s[i] === "]") depth--;
        else if (s[i] === "," && depth === 0) {
            parts.push(s.slice(start, i));
            start = i + 1;
        }
    }
    parts.push(s.slice(start));
    return parts;
}

function modernizePython(code: string): string {
    // Replace Optional[X] with X | None (handles arbitrarily nested brackets)
    code = replaceBalancedBrackets(code, "Optional", (inner) => `${inner} | None`);

    // Replace Union[X, Y] with X | Y (split only at top-level commas, not inside brackets)
    // Run iteratively to handle nested Union inside Dict/List
    let prev = "";
    while (prev !== code) {
        prev = code;
        code = replaceBalancedBrackets(code, "Union", (inner) => {
            return splitTopLevelCommas(inner).map((s: string) => s.trim()).join(" | ");
        });
    }

    // Replace List[X] with list[X]
    code = code.replace(/\bList\[/g, "list[");

    // Replace Dict[K, V] with dict[K, V]
    code = code.replace(/\bDict\[/g, "dict[");

    // Replace Type[T] with type[T]
    code = code.replace(/\bType\[/g, "type[");

    // Move Callable from typing to collections.abc
    code = code.replace(
        /from typing import (.*), Callable$/m,
        "from typing import $1\nfrom collections.abc import Callable"
    );
    code = code.replace(
        /from typing import Callable, (.*)$/m,
        "from typing import $1\nfrom collections.abc import Callable"
    );

    // Remove now-unused imports from typing (Optional, List, Dict, Type)
    code = code.replace(/from typing import (.+)$/m, (_match, imports: string) => {
        const items = imports.split(",").map((s: string) => s.trim());
        const remove = new Set(["Optional", "List", "Dict", "Type", "Union"]);
        const kept = items.filter((i: string) => !remove.has(i));
        return `from typing import ${kept.join(", ")}`;
    });

    return code;
}

function collapsePlaceholderPythonDataclasses(code: string): string {
    const classBlockRe = /(@dataclass\r?\nclass\s+(\w+):[\s\S]*?)(?=^@dataclass|^class\s+\w+|^def\s+\w+|\Z)/gm;
    const matches = [...code.matchAll(classBlockRe)].map((match) => ({
        fullBlock: match[1],
        name: match[2],
        normalizedBody: normalizePythonDataclassBlock(match[1], match[2]),
    }));
    const groups = new Map<string, typeof matches>();

    for (const match of matches) {
        const group = groups.get(match.normalizedBody) ?? [];
        group.push(match);
        groups.set(match.normalizedBody, group);
    }

    for (const group of groups.values()) {
        if (group.length < 2) continue;

        const canonical = chooseCanonicalPlaceholderDuplicate(group.map(({ name }) => name));
        if (!canonical) continue;

        for (const duplicate of group) {
            if (duplicate.name === canonical) continue;
            if (!isPlaceholderTypeName(duplicate.name)) continue;

            code = code.replace(duplicate.fullBlock, "");
            code = code.replace(new RegExp(`\\b${duplicate.name}\\b`, "g"), canonical);
        }
    }

    return code.replace(/\n{3,}/g, "\n\n");
}

function normalizePythonDataclassBlock(block: string, name: string): string {
    return block
        .replace(/^@dataclass\r?\nclass\s+\w+:/, "@dataclass\nclass:")
        .replace(new RegExp(`\\b${name}\\b`, "g"), "SelfType")
        .split(/\r?\n/)
        .map((line) => line.trim())
        .filter((line) => line.length > 0)
        .join("\n");
}

function chooseCanonicalPlaceholderDuplicate(names: string[]): string | undefined {
    const specificNames = names.filter((name) => !isPlaceholderTypeName(name));
    if (specificNames.length === 0) return undefined;
    return specificNames.sort((left, right) => right.length - left.length || left.localeCompare(right))[0];
}

function isPlaceholderTypeName(name: string): boolean {
    return name.endsWith("Class");
}

function toSnakeCase(s: string): string {
    return s
        .replace(/([a-z])([A-Z])/g, "$1_$2")
        .replace(/[._]/g, "_")
        .toLowerCase();
}

function toPascalCase(s: string): string {
    return s
        .split(/[._]/)
        .map((w) => w.charAt(0).toUpperCase() + w.slice(1))
        .join("");
}

function collectRpcMethods(node: Record<string, unknown>): RpcMethod[] {
    const results: RpcMethod[] = [];
    for (const value of Object.values(node)) {
        if (isRpcMethod(value)) {
            results.push(value);
        } else if (typeof value === "object" && value !== null) {
            results.push(...collectRpcMethods(value as Record<string, unknown>));
        }
    }
    return results;
}

function pythonResultTypeName(method: RpcMethod): string {
    return getRpcSchemaTypeName(method.result, toPascalCase(method.rpcMethod) + "Result");
}

function pythonParamsTypeName(method: RpcMethod): string {
    return getRpcSchemaTypeName(method.params, toPascalCase(method.rpcMethod) + "Request");
}

// ── Session Events ──────────────────────────────────────────────────────────

async function generateSessionEvents(schemaPath?: string): Promise<void> {
    console.log("Python: generating session-events...");

    const resolvedPath = schemaPath ?? (await getSessionEventsSchemaPath());
    const schema = cloneSchemaForCodegen(JSON.parse(await fs.readFile(resolvedPath, "utf-8")) as JSONSchema7);
    const resolvedSchema = (schema.definitions?.SessionEvent as JSONSchema7) || schema;
    const processed = postProcessSchema(resolvedSchema);

    // Hoist titled inline schemas (enums etc.) to definitions so quicktype
    // uses the schema-defined names instead of its own structural heuristics.
    const { rootDefinitions: hoistedRoots, sharedDefinitions } = hoistTitledSchemas({ SessionEvent: processed });
    const hoisted = hoistedRoots.SessionEvent;
    if (Object.keys(sharedDefinitions).length > 0) {
        hoisted.definitions = { ...hoisted.definitions, ...sharedDefinitions };
    }

    const schemaInput = new JSONSchemaInput(new FetchingJSONSchemaStore());
    await schemaInput.addSource({ name: "SessionEvent", schema: JSON.stringify(hoisted) });

    const inputData = new InputData();
    inputData.addInput(schemaInput);

    const result = await quicktype({
        inputData,
        lang: "python",
        rendererOptions: { "python-version": "3.7" },
    });

    let code = result.lines.join("\n");

    // Fix dataclass field ordering (Any fields need defaults)
    code = code.replace(/: Any$/gm, ": Any = None");
    // Fix bare except: to use Exception (required by ruff/pylint)
    code = code.replace(/except:/g, "except Exception:");
    // Modernize to Python 3.11+ syntax
    code = modernizePython(code);

    // Add UNKNOWN enum value for forward compatibility
    code = code.replace(
        /^(class SessionEventType\(Enum\):.*?)(^\s*\n@dataclass)/ms,
        `$1    # UNKNOWN is used for forward compatibility
    UNKNOWN = "unknown"

    @classmethod
    def _missing_(cls, value: object) -> "SessionEventType":
        """Handle unknown event types gracefully for forward compatibility."""
        return cls.UNKNOWN

$2`
    );

    const banner = `"""
AUTO-GENERATED FILE - DO NOT EDIT
Generated from: session-events.schema.json
"""

`;

    const outPath = await writeGeneratedFile("python/copilot/generated/session_events.py", banner + code);
    console.log(`  ✓ ${outPath}`);
}

// ── RPC Types ───────────────────────────────────────────────────────────────

async function generateRpc(schemaPath?: string): Promise<void> {
    console.log("Python: generating RPC types...");

    const resolvedPath = schemaPath ?? (await getApiSchemaPath());
    const schema = cloneSchemaForCodegen(JSON.parse(await fs.readFile(resolvedPath, "utf-8")) as ApiSchema);

    const allMethods = [
        ...collectRpcMethods(schema.server || {}),
        ...collectRpcMethods(schema.session || {}),
        ...collectRpcMethods(schema.clientSession || {}),
    ];

    // Build a combined schema for quicktype
    const combinedSchema: JSONSchema7 = {
        $schema: "http://json-schema.org/draft-07/schema#",
        definitions: {},
    };

    for (const method of allMethods) {
        if (!isVoidSchema(method.result)) {
            combinedSchema.definitions![pythonResultTypeName(method)] = method.result;
        }
        if (method.params?.properties && Object.keys(method.params.properties).length > 0) {
            if (method.rpcMethod.startsWith("session.")) {
                const filtered: JSONSchema7 = {
                    ...method.params,
                    properties: Object.fromEntries(
                        Object.entries(method.params.properties).filter(([k]) => k !== "sessionId")
                    ),
                    required: method.params.required?.filter((r) => r !== "sessionId"),
                };
                if (Object.keys(filtered.properties!).length > 0) {
                    combinedSchema.definitions![pythonParamsTypeName(method)] = filtered;
                }
            } else {
                combinedSchema.definitions![pythonParamsTypeName(method)] = method.params;
            }
        }
    }

    const { rootDefinitions, sharedDefinitions } = hoistTitledSchemas(combinedSchema.definitions! as Record<string, JSONSchema7>);

    // Generate types via quicktype
    const schemaInput = new JSONSchemaInput(new FetchingJSONSchemaStore());
    for (const [name, def] of Object.entries(rootDefinitions)) {
        await schemaInput.addSource({
            name,
            schema: JSON.stringify({
                ...def,
                definitions: sharedDefinitions,
            }),
        });
    }

    const inputData = new InputData();
    inputData.addInput(schemaInput);

    const qtResult = await quicktype({
        inputData,
        lang: "python",
        rendererOptions: { "python-version": "3.7" },
    });

    let typesCode = qtResult.lines.join("\n");
    // Fix dataclass field ordering
    typesCode = typesCode.replace(/: Any$/gm, ": Any = None");
    // Fix bare except: to use Exception (required by ruff/pylint)
    typesCode = typesCode.replace(/except:/g, "except Exception:");
    // Remove unnecessary pass when class has methods (quicktype generates pass for empty schemas)
    typesCode = typesCode.replace(/^(\s*)pass\n\n(\s*@staticmethod)/gm, "$2");
    // Modernize to Python 3.11+ syntax
    typesCode = modernizePython(typesCode);
    typesCode = collapsePlaceholderPythonDataclasses(typesCode);

    // Annotate experimental data types
    const experimentalTypeNames = new Set<string>();
    for (const method of allMethods) {
        if (method.stability !== "experimental") continue;
        experimentalTypeNames.add(pythonResultTypeName(method));
        const paramsTypeName = pythonParamsTypeName(method);
        if (rootDefinitions[paramsTypeName]) {
            experimentalTypeNames.add(paramsTypeName);
        }
    }
    for (const typeName of experimentalTypeNames) {
        typesCode = typesCode.replace(
            new RegExp(`^(@dataclass\\n)?class ${typeName}[:(]`, "m"),
            (match) => `# Experimental: this type is part of an experimental API and may change or be removed.\n${match}`
        );
    }

    // Extract actual class names generated by quicktype (may differ from toPascalCase,
    // e.g. quicktype produces "SessionMCPList" not "SessionMcpList")
    const actualTypeNames = new Map<string, string>();
    const classRe = /^class\s+(\w+)\b/gm;
    let cm;
    while ((cm = classRe.exec(typesCode)) !== null) {
        actualTypeNames.set(cm[1].toLowerCase(), cm[1]);
    }
    const resolveType = (name: string): string => actualTypeNames.get(name.toLowerCase()) ?? name;

    const lines: string[] = [];
    lines.push(`"""
AUTO-GENERATED FILE - DO NOT EDIT
Generated from: api.schema.json
"""

from typing import TYPE_CHECKING

if TYPE_CHECKING:
    from .._jsonrpc import JsonRpcClient

from collections.abc import Callable
from dataclasses import dataclass
from typing import Protocol

`);
    lines.push(typesCode);
    lines.push(`
def _timeout_kwargs(timeout: float | None) -> dict:
    """Build keyword arguments for optional timeout forwarding."""
    if timeout is not None:
        return {"timeout": timeout}
    return {}

def _patch_model_capabilities(data: dict) -> dict:
    """Ensure model capabilities have required fields.

    TODO: Remove once the runtime schema correctly marks these fields as optional.
    Some models (e.g. embedding models) may omit 'limits' or 'supports' in their
    capabilities, or omit 'max_context_window_tokens' within limits. The generated
    deserializer requires these fields, so we supply defaults here.
    """
    for model in data.get("models", []):
        caps = model.get("capabilities")
        if caps is None:
            model["capabilities"] = {"supports": {}, "limits": {"max_context_window_tokens": 0}}
            continue
        if "supports" not in caps:
            caps["supports"] = {}
        if "limits" not in caps:
            caps["limits"] = {"max_context_window_tokens": 0}
        elif "max_context_window_tokens" not in caps["limits"]:
            caps["limits"]["max_context_window_tokens"] = 0
    return data

`);

    // Emit RPC wrapper classes
    if (schema.server) {
        emitRpcWrapper(lines, schema.server, false, resolveType);
    }
    if (schema.session) {
        emitRpcWrapper(lines, schema.session, true, resolveType);
    }
    if (schema.clientSession) {
        emitClientSessionApiRegistration(lines, schema.clientSession, resolveType);
    }

    // Patch models.list to normalize capabilities before deserialization
    let finalCode = lines.join("\n");
    finalCode = finalCode.replace(
        `ModelList.from_dict(await self._client.request("models.list"`,
        `ModelList.from_dict(_patch_model_capabilities(await self._client.request("models.list"`,
    );
    // Close the extra paren opened by _patch_model_capabilities(
    finalCode = finalCode.replace(
        /(_patch_model_capabilities\(await self\._client\.request\("models\.list",\s*\{[^)]*\)[^)]*\))/,
        "$1)",
    );

    const outPath = await writeGeneratedFile("python/copilot/generated/rpc.py", finalCode);
    console.log(`  ✓ ${outPath}`);
}

function emitRpcWrapper(lines: string[], node: Record<string, unknown>, isSession: boolean, resolveType: (name: string) => string): void {
    const groups = Object.entries(node).filter(([, v]) => typeof v === "object" && v !== null && !isRpcMethod(v));
    const topLevelMethods = Object.entries(node).filter(([, v]) => isRpcMethod(v));

    const wrapperName = isSession ? "SessionRpc" : "ServerRpc";

    // Emit API classes for groups
    for (const [groupName, groupNode] of groups) {
        const prefix = isSession ? "" : "Server";
        const apiName = prefix + toPascalCase(groupName) + "Api";
        const groupExperimental = isNodeFullyExperimental(groupNode as Record<string, unknown>);
        if (isSession) {
            if (groupExperimental) {
                lines.push(`# Experimental: this API group is experimental and may change or be removed.`);
            }
            lines.push(`class ${apiName}:`);
            lines.push(`    def __init__(self, client: "JsonRpcClient", session_id: str):`);
            lines.push(`        self._client = client`);
            lines.push(`        self._session_id = session_id`);
        } else {
            if (groupExperimental) {
                lines.push(`# Experimental: this API group is experimental and may change or be removed.`);
            }
            lines.push(`class ${apiName}:`);
            lines.push(`    def __init__(self, client: "JsonRpcClient"):`);
            lines.push(`        self._client = client`);
        }
        lines.push(``);
        for (const [key, value] of Object.entries(groupNode as Record<string, unknown>)) {
            if (!isRpcMethod(value)) continue;
            emitMethod(lines, key, value, isSession, resolveType, groupExperimental);
        }
        lines.push(``);
    }

    // Emit wrapper class
    if (isSession) {
        lines.push(`class ${wrapperName}:`);
        lines.push(`    """Typed session-scoped RPC methods."""`);
        lines.push(`    def __init__(self, client: "JsonRpcClient", session_id: str):`);
        lines.push(`        self._client = client`);
        lines.push(`        self._session_id = session_id`);
        for (const [groupName] of groups) {
            lines.push(`        self.${toSnakeCase(groupName)} = ${toPascalCase(groupName)}Api(client, session_id)`);
        }
    } else {
        lines.push(`class ${wrapperName}:`);
        lines.push(`    """Typed server-scoped RPC methods."""`);
        lines.push(`    def __init__(self, client: "JsonRpcClient"):`);
        lines.push(`        self._client = client`);
        for (const [groupName] of groups) {
            lines.push(`        self.${toSnakeCase(groupName)} = Server${toPascalCase(groupName)}Api(client)`);
        }
    }
    lines.push(``);

    // Top-level methods
    for (const [key, value] of topLevelMethods) {
        if (!isRpcMethod(value)) continue;
        emitMethod(lines, key, value, isSession, resolveType, false);
    }
    lines.push(``);
}

function emitMethod(lines: string[], name: string, method: RpcMethod, isSession: boolean, resolveType: (name: string) => string, groupExperimental = false): void {
    const methodName = toSnakeCase(name);
    const hasResult = !isVoidSchema(method.result);
    const resultType = hasResult ? resolveType(pythonResultTypeName(method)) : "None";
    const resultIsObject = isObjectSchema(method.result);

    const paramProps = method.params?.properties || {};
    const nonSessionParams = Object.keys(paramProps).filter((k) => k !== "sessionId");
    const hasParams = isSession ? nonSessionParams.length > 0 : Object.keys(paramProps).length > 0;
    const paramsType = resolveType(pythonParamsTypeName(method));

    // Build signature with typed params + optional timeout
    const sig = hasParams
        ? `    async def ${methodName}(self, params: ${paramsType}, *, timeout: float | None = None) -> ${resultType}:`
        : `    async def ${methodName}(self, *, timeout: float | None = None) -> ${resultType}:`;

    lines.push(sig);

    if (method.stability === "experimental" && !groupExperimental) {
        lines.push(`        """.. warning:: This API is experimental and may change or be removed in future versions."""`);
    }

    // For object results use .from_dict(); for enums/primitives use direct construction
    const deserialize = (expr: string) => resultIsObject ? `${resultType}.from_dict(${expr})` : `${resultType}(${expr})`;

    // Build request body with proper serialization/deserialization
    if (isSession) {
        if (hasParams) {
            lines.push(`        params_dict = {k: v for k, v in params.to_dict().items() if v is not None}`);
            lines.push(`        params_dict["sessionId"] = self._session_id`);
            if (hasResult) {
                lines.push(`        return ${deserialize(`await self._client.request("${method.rpcMethod}", params_dict, **_timeout_kwargs(timeout))`)}`);
            } else {
                lines.push(`        await self._client.request("${method.rpcMethod}", params_dict, **_timeout_kwargs(timeout))`);
            }
        } else {
            if (hasResult) {
                lines.push(`        return ${deserialize(`await self._client.request("${method.rpcMethod}", {"sessionId": self._session_id}, **_timeout_kwargs(timeout))`)}`);
            } else {
                lines.push(`        await self._client.request("${method.rpcMethod}", {"sessionId": self._session_id}, **_timeout_kwargs(timeout))`);
            }
        }
    } else {
        if (hasParams) {
            lines.push(`        params_dict = {k: v for k, v in params.to_dict().items() if v is not None}`);
            if (hasResult) {
                lines.push(`        return ${deserialize(`await self._client.request("${method.rpcMethod}", params_dict, **_timeout_kwargs(timeout))`)}`);
            } else {
                lines.push(`        await self._client.request("${method.rpcMethod}", params_dict, **_timeout_kwargs(timeout))`);
            }
        } else {
            if (hasResult) {
                lines.push(`        return ${deserialize(`await self._client.request("${method.rpcMethod}", {}, **_timeout_kwargs(timeout))`)}`);
            } else {
                lines.push(`        await self._client.request("${method.rpcMethod}", {}, **_timeout_kwargs(timeout))`);
            }
        }
    }
    lines.push(``);
}

function emitClientSessionApiRegistration(
    lines: string[],
    node: Record<string, unknown>,
    resolveType: (name: string) => string
): void {
    const groups = Object.entries(node).filter(([, value]) => typeof value === "object" && value !== null && !isRpcMethod(value));

    for (const [groupName, groupNode] of groups) {
        const handlerName = `${toPascalCase(groupName)}Handler`;
        const groupExperimental = isNodeFullyExperimental(groupNode as Record<string, unknown>);
        if (groupExperimental) {
            lines.push(`# Experimental: this API group is experimental and may change or be removed.`);
        }
        lines.push(`class ${handlerName}(Protocol):`);
        for (const [methodName, value] of Object.entries(groupNode as Record<string, unknown>)) {
            if (!isRpcMethod(value)) continue;
            emitClientSessionHandlerMethod(lines, methodName, value, resolveType, groupExperimental);
        }
        lines.push(``);
    }

    lines.push(`@dataclass`);
    lines.push(`class ClientSessionApiHandlers:`);
    if (groups.length === 0) {
        lines.push(`    pass`);
    } else {
        for (const [groupName] of groups) {
            lines.push(`    ${toSnakeCase(groupName)}: ${toPascalCase(groupName)}Handler | None = None`);
        }
    }
    lines.push(``);

    lines.push(`def register_client_session_api_handlers(`);
    lines.push(`    client: "JsonRpcClient",`);
    lines.push(`    get_handlers: Callable[[str], ClientSessionApiHandlers],`);
    lines.push(`) -> None:`);
    lines.push(`    """Register client-session request handlers on a JSON-RPC connection."""`);
    if (groups.length === 0) {
        lines.push(`    return`);
    } else {
        for (const [groupName, groupNode] of groups) {
            for (const [methodName, value] of Object.entries(groupNode as Record<string, unknown>)) {
                if (!isRpcMethod(value)) continue;
                emitClientSessionRegistrationMethod(
                    lines,
                    groupName,
                    methodName,
                    value,
                    resolveType
                );
            }
        }
    }
    lines.push(``);
}

function emitClientSessionHandlerMethod(
    lines: string[],
    name: string,
    method: RpcMethod,
    resolveType: (name: string) => string,
    groupExperimental = false
): void {
    const paramsType = resolveType(pythonParamsTypeName(method));
    const resultType = !isVoidSchema(method.result) ? resolveType(pythonResultTypeName(method)) : "None";
    lines.push(`    async def ${toSnakeCase(name)}(self, params: ${paramsType}) -> ${resultType}:`);
    if (method.stability === "experimental" && !groupExperimental) {
        lines.push(`        """.. warning:: This API is experimental and may change or be removed in future versions."""`);
    }
    lines.push(`        pass`);
}

function emitClientSessionRegistrationMethod(
    lines: string[],
    groupName: string,
    methodName: string,
    method: RpcMethod,
    resolveType: (name: string) => string
): void {
    const handlerVariableName = `handle_${toSnakeCase(groupName)}_${toSnakeCase(methodName)}`;
    const paramsType = resolveType(pythonParamsTypeName(method));
    const resultType = !isVoidSchema(method.result) ? resolveType(pythonResultTypeName(method)) : null;
    const handlerField = toSnakeCase(groupName);
    const handlerMethod = toSnakeCase(methodName);

    lines.push(`    async def ${handlerVariableName}(params: dict) -> dict | None:`);
    lines.push(`        request = ${paramsType}.from_dict(params)`);
    lines.push(`        handler = get_handlers(request.session_id).${handlerField}`);
    lines.push(
        `        if handler is None: raise RuntimeError(f"No ${handlerField} handler registered for session: {request.session_id}")`
    );
    if (resultType) {
        lines.push(`        result = await handler.${handlerMethod}(request)`);
        if (isObjectSchema(method.result)) {
            lines.push(`        return result.to_dict()`);
        } else {
            lines.push(`        return result.value if hasattr(result, 'value') else result`);
        }
    } else {
        lines.push(`        await handler.${handlerMethod}(request)`);
        lines.push(`        return None`);
    }
    lines.push(`    client.set_request_handler("${method.rpcMethod}", ${handlerVariableName})`);
}

// ── Main ────────────────────────────────────────────────────────────────────

async function generate(sessionSchemaPath?: string, apiSchemaPath?: string): Promise<void> {
    await generateSessionEvents(sessionSchemaPath);
    try {
        await generateRpc(apiSchemaPath);
    } catch (err) {
        if ((err as NodeJS.ErrnoException).code === "ENOENT" && !apiSchemaPath) {
            console.log("Python: skipping RPC (api.schema.json not found)");
        } else {
            throw err;
        }
    }
}

const sessionArg = process.argv[2] || undefined;
const apiArg = process.argv[3] || undefined;
generate(sessionArg, apiArg).catch((err) => {
    console.error("Python generation failed:", err);
    process.exit(1);
});