import { ClipboardAddon } from "@xterm/addon-clipboard";
import { FitAddon } from "@xterm/addon-fit";
import { Unicode11Addon } from "@xterm/addon-unicode11";
import { WebLinksAddon } from "@xterm/addon-web-links";
import * as xterm from "@xterm/xterm";
import { Loader2 } from "lucide-react";
import { useEffect, useRef, useState } from "react";

import cn from "~/utils/cn";
import { useLiveData } from "~/utils/live-data";
import toast from "~/utils/toast";

import "@xterm/xterm/css/xterm.css";

interface XTermProps {
  ipn: TsWasmNet;
  username: string;
  hostname: string;
}

// Go's WASM -> JS crosses realms so we might have to normalize the data under
// certain conditions. This also enforces bytes instead of strings being sent.
function normU8(data: unknown) {
  if (data instanceof Uint8Array) {
    return data;
  }

  if (data && typeof data === "object") {
    const any = data as {
      buffer?: ArrayBufferLike;
      byteOffset?: number;
      byteLength?: number;
    };

    if (any.buffer instanceof ArrayBuffer && typeof any.byteLength === "number") {
      return new Uint8Array(
        any.buffer.slice(any.byteOffset ?? 0, (any.byteOffset ?? 0) + any.byteLength),
      );
    }
  }

  throw new Error("Data is not a Uint8Array or ArrayBuffer-like object");
}

export default function XTerm({ ipn, username, hostname }: XTermProps) {
  const { pause } = useLiveData();

  const genRef = useRef(0);
  const termRef = useRef<xterm.Terminal>(null);
  const roRef = useRef<ResizeObserver>(null);
  const inputRef = useRef<(input: Uint8Array) => void>(null);
  const sshRef = useRef<SSHSession>(null);
  const divRef = useRef<HTMLDivElement>(null);

  const [isResizing, setIsResizing] = useState(false);
  const [isLoading, setIsLoading] = useState(true);
  const [error, setError] = useState<string | null>(null);

  useEffect(() => {
    pause();
  });

  useEffect(() => {
    if (!divRef.current) {
      return;
    }

    const currentGen = ++genRef.current;
    const term = new xterm.Terminal({
      allowProposedApi: true,
      cursorBlink: true,
      convertEol: true,
      fontSize: 14,
    });

    const fit = new FitAddon();
    term.loadAddon(fit);

    term.loadAddon(new Unicode11Addon());
    term.loadAddon(new ClipboardAddon());
    term.loadAddon(
      new WebLinksAddon((event, uri) => {
        event.view?.open(uri, "_blank", "noopener noreferrer");
      }),
    );

    term.unicode.activeVersion = "11";
    termRef.current = term;
    term.open(divRef.current!);
    fit.fit();
    term.focus();

    const session = ipn.OpenSSH(hostname, username, {
      rows: term.rows,
      cols: term.cols,
      onStdout: (data) => {
        if (currentGen !== genRef.current || term !== termRef.current) {
          console.warn("Stale terminal instance, ignoring stdout");
          return;
        }

        const text = normU8(data);
        term.write(text);
      },
      onStderr: (data) => {
        if (currentGen !== genRef.current || term !== termRef.current) {
          console.warn("Stale terminal instance, ignoring stderr");
          return;
        }

        const text = normU8(data);
        term.write(text);
        const str = new TextDecoder().decode(text);
        setError(str);
      },
      onStdin: (func) => {
        inputRef.current = func;
      },
      onConnect: () => {
        if (currentGen !== genRef.current) {
          console.warn("Stale terminal instance, ignoring onConnect");
          return;
        }

        setIsLoading(false);
      },
      onDisconnect: () => {
        if (currentGen !== genRef.current) {
          console.warn("Stale terminal instance, ignoring onDisconnect");
          return;
        }

        roRef.current?.disconnect();
        term.dispose();
        termRef.current = null;
        inputRef.current = null;
        sshRef.current = null;

        setIsLoading(false);
      },
    });

    sshRef.current = session;
    const enc = new TextEncoder();
    term.onData((data) => {
      if (currentGen !== genRef.current) {
        console.warn("Stale terminal instance, ignoring onData");
        return;
      }

      const bytes = enc.encode(data);
      inputRef.current?.(bytes);
    });

    const ro = new ResizeObserver(() => {
      if (currentGen !== genRef.current || term !== termRef.current) {
        console.warn("Stale terminal instance, ignoring resize");
        return;
      }

      setIsResizing(true);
      fit.fit();
      sshRef.current?.Resize(term.cols, term.rows);
      setTimeout(() => setIsResizing(false), 100);
    });

    roRef.current = ro;
    ro.observe(divRef.current!);

    return () => {
      ++genRef.current;
      roRef.current?.disconnect();
      roRef.current = null;

      sshRef.current?.Close();
      sshRef.current = null;

      term.dispose();
      if (termRef.current === term) {
        termRef.current = null;
      }

      inputRef.current = null;
    };
  }, [ipn, username, hostname]);

  return (
    <>
      {isLoading ? (
        <div className="absolute z-50 mx-auto flex h-screen w-screen items-center justify-center">
          <Loader2 className="size-10 animate-spin text-mist-50" />
        </div>
      ) : undefined}
      <div className={cn("w-full h-full", isLoading ? "opacity-0" : "opacity-100")} ref={divRef} />
      {termRef.current && isResizing ? (
        <div
          className={cn(
            "absolute left-1/2 top-1/2 -translate-x-1/2 -translate-y-1/2",
            "px-4 py-2 bg-mist-800 text-white rounded-full shadow z-50",
          )}
        >
          {termRef.current.cols}x{termRef.current.rows}
        </div>
      ) : undefined}
      {error !== null ? (
        <div
          className={cn(
            "absolute left-1/2 top-1/2 -translate-x-1/2 -translate-y-1/2 text-center",
            "px-4 py-2 bg-mist-800 text-white rounded-full shadow z-50",
          )}
        >
          Failed to connect to SSH session
          {error}
        </div>
      ) : undefined}
    </>
  );
}