import {
    ClientRequest,
    Agent as HTTPAgent,
    IncomingMessage,
    RequestOptions,
    STATUS_CODES,
    request as httpRequest,
} from "http";

import { Readable } from "stream";
import EventEmitter from "events";

import {
    C2SRequestTypes,
    HTTPRequestPayload,
    HTTPResponsePayload,
    ProtoBareHeaders,
    S2CRequestTypes,
} from "../protocol/index.js";
import { BareError, bareFetch, options } from "./http.js";
export class Client {
    send: (msg: Buffer) => void;
    events: EventEmitter;

    constructor(send) {
        this.send = send;
        this.events = new EventEmitter();
    }

    static parseMsgInit(
        msg: Buffer
    ): { cursor: number; seq: number; op: number } | undefined {
        try {
            let cursor = 0;
            const seq = msg.readUint16BE(cursor);
            cursor += 2;
            const op = msg.readUint8(cursor);
            cursor += 1;
            return { cursor, seq, op };
        } catch (e) {
            if (e instanceof RangeError) {
                // malformed message
                return;
            }
            throw e;
        }
    }

    static parseHttpReqPayload(
        payloadRaw: Buffer
    ): HTTPRequestPayload | undefined {
        let payload;
        try {
            payload = JSON.parse(payloadRaw.toString());
        } catch (e) {
            if (e instanceof SyntaxError) {
                return;
            }
            throw e;
        }
        console.log({ payload });
        return payload;
    }

    static bareErrorToResponse(e: BareError): {
        payload: HTTPResponsePayload;
        body: Buffer;
    } {
        return {
            payload: {
                status: e.status,
                statusText: STATUS_CODES[e.status] || "",
                headers: {},
            },
            body: Buffer.from(JSON.stringify(e.body)),
        };
    }

    async handleHTTPRequest(payload: HTTPRequestPayload): Promise<{
        payload: HTTPResponsePayload;
        body: Buffer;
    }> {
        const abort = new AbortController();
        const onClose = () => {
            abort.abort();
            this.events.off("close", onClose);
        };
        this.events.on("close", onClose);

        let resp: IncomingMessage;
        try {
            resp = await bareFetch(
                payload,
                abort.signal,
                new URL(payload.remote),
                options
            );
        } catch (e) {
            if (e instanceof BareError) {
                return Client.bareErrorToResponse(e);
            }
            this.events.off("close", onClose);
            throw e;
        }

        this.events.off("close", onClose);
        const buffers: any[] = [];

        // node.js readable streams implement the async iterator protocol
        for await (const data of resp) {
            buffers.push(data);
        }
        const body = Buffer.concat(buffers);

        return {
            payload: {
                status: resp.statusCode || 500,
                statusText: resp.statusMessage || "",
                headers: Object.fromEntries(
                    Object.entries(resp.headersDistinct).filter(([k, v]) => Boolean(v))
                ) as ProtoBareHeaders,
            },
            body,
        };
    }

    sendHTTPResponse(seq: number, payload: HTTPResponsePayload, body: Buffer) {
        const payloadBuffer = Buffer.from(JSON.stringify(payload));
        const buf = Buffer.alloc(2 + 1 + 4 + payloadBuffer.length + body.length);
        let cursor = 0;
        cursor = buf.writeUInt16BE(seq, cursor);
        cursor = buf.writeUInt8(S2CRequestTypes.HTTPResponse, cursor);
        cursor = buf.writeUInt32BE(payloadBuffer.length, cursor);
        cursor += payloadBuffer.copy(buf, cursor);
        body.copy(buf, cursor);
        this.send(buf);
    }

    async onMsg(msg: Buffer) {
        const init = Client.parseMsgInit(msg);
        if (!init) return;
        const { cursor, seq, op } = init;
        switch (op) {
            case C2SRequestTypes.HTTPRequest:
                let resp;
                const reqPayload = Client.parseHttpReqPayload(msg.subarray(cursor));
                if (!reqPayload) return;
                try {
                    resp = await this.handleHTTPRequest(reqPayload);
                } catch (e) {
                    if (options.logErrors) console.error(e);

                    let bareError;
                    if (e instanceof BareError) {
                        bareError = e;
                    } else if (e instanceof Error) {
                        bareError = new BareError(500, {
                            code: "UNKNOWN",
                            id: `error.${e.name}`,
                            message: e.message,
                            stack: e.stack,
                        });
                    } else {
                        bareError = new BareError(500, {
                            code: "UNKNOWN",
                            id: "error.Exception",
                            message: "Error: " + e,
                            stack: new Error(<string | undefined>e).stack,
                        });
                    }

                    resp = Client.bareErrorToResponse(bareError);
                }

                const { payload, body } = resp;
                this.sendHTTPResponse(seq, payload, body);
                break;
            default:
                // not implemented
                break;
        }
    }

    onClose() {
        this.events.emit("close");
    }
}