import * as net from 'node:net';
import * as readline from 'node:readline';
import {type ChildProcess, spawn} from 'node:child_process';
import * as os from 'node:os';
import * as path from 'node:path';
import * as fs from 'node:fs';
import * as util from 'node:util';
import {QueuedEvent} from 'ts-events';

const IPC_SOCKET_ARG = '--ipc-socket';

enum MsgType {
    Call = 1,
    Response = 2,
}

type Vals = any[];

interface CallMessage {
    type: MsgType.Call,
    id: number,
    method: string;
    params: Vals;
}

interface ResponseMessage {
    type: MsgType.Response,
    id: number,
    result?: Vals;
    error?: string;
}

type Message = CallMessage | ResponseMessage;

interface CallResult {
    result: Vals;
    error: Error | null;
}

abstract class IPCCommon {
    protected localApi: any;
    protected socketPath: string;
    protected conn: net.Socket | null = null;
    protected nextId: number = 0;
    protected pendingCalls: Record<number, (result: CallResult) => void> = {};
    protected errors: QueuedEvent<Error>;

    protected constructor(localApi: any, socketPath: string) {
        this.localApi = localApi;
        this.socketPath = socketPath;
        this.errors = new QueuedEvent();
    }

    protected readConn(): void {
        if (!this.conn) throw new Error('no connection');

        const rl = readline.createInterface({
            input: this.conn,
            crlfDelay: Infinity,
        });

        rl.on('line', (line) => {
            try {
                const msg: Message = JSON.parse(line);
                this.processMsg(msg);
            } catch (e) {
                this.raiseErr(new Error(`${e}`));
            }
        });

        rl.on('error', (e) => {
            this.raiseErr(e);
        });

        rl.on('close', () => {
            this.raiseErr(new Error('connection closed'));
        });
    }

    protected processMsg(msg: Message): void {
        switch (msg.type) {
            case MsgType.Call:
                this.handleCall(msg);
                break;
            case MsgType.Response:
                this.handleResponse(msg);
                break;
        }
    }

    protected handleCall(msg: CallMessage): void {
        if (!this.localApi) {
            this.sendMsg({type: MsgType.Response, id: msg.id, error: 'remote side does not accept ipc calls'});
            return;
        }

        const method = this.localApi[msg.method];
        if (!method || typeof method !== 'function') {
            this.sendMsg({type: MsgType.Response, id: msg.id, error: `method not found: ${msg.method}`});
            return;
        }

        const argsCount = method.length;
        if (msg.params.length !== argsCount) {
            this.sendMsg({
                type: MsgType.Response,
                id: msg.id,
                error: `argument count mismatch: expected ${argsCount}, got ${msg.params.length}`
            });
            return;
        }

        try {
            const result = method.apply(this.localApi, msg.params);

            if (result instanceof Promise) {
                result
                    .then((res) => {
                        this.sendMsg({type: MsgType.Response, id: msg.id, result: [res]});
                    })
                    .catch((err) => {
                        this.sendMsg({type: MsgType.Response, id: msg.id, error: `${err}`});
                    });
            } else {
                this.sendMsg({type: MsgType.Response, id: msg.id, result: [result]});
            }
        } catch (err) {
            this.sendMsg({type: MsgType.Response, id: msg.id, error: `${err}`});
        }
    }

    protected sendMsg(msg: Message): void {
        if (!this.conn) throw new Error('no connection');

        try {
            const data = JSON.stringify(msg) + '\n';
            this.conn.write(data);
        } catch (e) {
            this.raiseErr(new Error(`send response for ${msg.id}: ${e}`));
        }
    }

    protected handleResponse(msg: ResponseMessage): void {
        const callback = this.pendingCalls[msg.id];
        if (!callback) {
            this.raiseErr(new Error(`received response for unknown msgId: ${msg.id}`));
            return;
        }

        delete this.pendingCalls[msg.id];

        const err = msg.error ? new Error(`remote error: ${msg.error}`) : null;
        callback({ result: msg.result || [], error: err });
    }

    protected raiseErr(err: Error): void {
        this.errors.post(err);
    }

    call(method: string, ...params: Vals): Promise<Vals> {
        return new Promise((resolve, reject) => {
            const id = this.nextId++;

            this.pendingCalls[id] = (result: CallResult) => {
                if (result.error) {
                    reject(result.error);
                } else {
                    resolve(result.result);
                }
            };
            try {
                this.sendMsg({
                    type: MsgType.Call,
                    id,
                    method,
                    params,
                });
            } catch (e) {
                delete this.pendingCalls[id];
                reject(new Error(`send call: ${e}`));
            }
        });
    }
}


class ParentIPC extends IPCCommon {
    private readonly cmdPath: string;
    private readonly cmdArgs: string[];
    private cmd: ChildProcess | null = null;
    private readonly listener: net.Server;

    constructor(cmdPath: string, cmdArgs: string[], localApi: any) {
        const socketPath = path.join(os.tmpdir(), `kitten-ipc-${process.pid}.sock`);
        super(localApi, socketPath);

        this.cmdPath = cmdPath;
        if (cmdArgs.includes(IPC_SOCKET_ARG)) {
            throw new Error(`you should not use '${IPC_SOCKET_ARG}' argument in your command`);
        }
        this.cmdArgs = cmdArgs;

        this.listener = net.createServer();
    }

    async start(): Promise<void> {
        try {
            fs.unlinkSync(this.socketPath);
        } catch {}


        await new Promise<void>((resolve, reject) => {
            this.listener.listen(this.socketPath, () => {
                resolve();
            });
            this.listener.on('error', reject);
        });

        const cmdArgs = [...this.cmdArgs, IPC_SOCKET_ARG, this.socketPath];
        this.cmd = spawn(this.cmdPath, cmdArgs, {stdio: 'inherit'});

        this.cmd.on('error', (err) => {
            this.raiseErr(err);
        });

        this.acceptConn().catch();
    }

    private async acceptConn(): Promise<void> {
        const acceptTimeout = 10000;

        const acceptPromise = new Promise<net.Socket>((resolve, reject) => {
            this.listener.once('connection', (conn) => {
                resolve(conn);
            });
            this.listener.once('error', reject);
        });

        try {
            this.conn = await timeout(acceptPromise, acceptTimeout);
            this.readConn();
        } catch (e) {
            if (this.cmd) this.cmd.kill();
            this.raiseErr(e as Error);
        }
    }

    async wait(): Promise<void> {
        return new Promise((resolve, reject) => {
            if(!this.cmd) throw new Error('Command is not started yet');
            this.cmd.addListener('close', (code, signal) => {
                if(signal || code) {
                    if(signal) reject(new Error(`Process exited with signal ${signal}`));
                    else reject(new Error(`Process exited with code ${code}`));
                } else {
                    resolve();
                }
            });
            this.errors.attach(err => {
                reject(err);
            })
        })
    }
}


export class ChildIPC extends IPCCommon {
    constructor(localApi: any) {
        super(localApi, socketPathFromArgs());
    }

    async start(): Promise<void> {
        return new Promise((resolve, reject) => {
            this.conn = net.createConnection(this.socketPath, () => {
                this.readConn();
                resolve();
            });
            this.conn.on('error', reject);
        });
    }

    async wait(): Promise<void> {
        return new Promise((resolve, reject) => {

        });
    }
}


function socketPathFromArgs(): string {
    const {values} = util.parseArgs({options: {
            IPC_SOCKET_ARG: {
                type: 'string',
            }
        }});

    if(!values.IPC_SOCKET_ARG) {
        throw new Error('ipc socket path is missing');
    }

    return values.IPC_SOCKET_ARG;
}


function sleep(ms: number): Promise<void> {
    return new Promise(resolve => setTimeout(resolve, ms));
}


// throws on timeout
function timeout<T>(prom: Promise<T>, ms: number): Promise<T> {
    return Promise.race(
        [prom, new Promise((res, reject) => setTimeout(reject, ms))]
    ) as Promise<T>;
}