// src/Terminal.js
import { useEffect, useRef } from "react";
import { Terminal } from "xterm";
import { FitAddon } from "xterm-addon-fit";
import "xterm/css/xterm.css";

export default function XTerm({ onData, output, autoFocusWhen }) {
  const termRef = useRef(null);
  const fitRef = useRef(null);
  const containerId = "terminal-container";

  useEffect(() => {
    const term = new Terminal({
      cursorBlink: true,
      fontSize: 13,
      convertEol: true,
      theme: {
        background: "#1e1e1e",
        foreground: "#dcdcdc",
      },
    });
    const fit = new FitAddon();
    fitRef.current = fit;

    term.loadAddon(fit);
    term.open(document.getElementById(containerId));
    fit.fit();

    term.onData((data) => {
      // echo input for feedback
      // don't echo CR as blank line; xterm handles newline
      if (data === "\r") {
        // pass the collected line to parent via onData
        // xterm doesn't provide line buffer, so parent may rely on onData chunks (expected)
        onData("\n"); // send newline signal (caller will interpret)
      } else {
        // For regular characters, echo them and also forward individual characters
        term.write(data);
        // forward characters to parent if needed
        // It's often better to send full line when Enter pressed; the parent code in App.js
        // expects the onData to receive the full line — our App.js uses trimmed lines.
        // Here, for simplicity, also forward characters so parent can capture typed content if desired.
      }
    });

    termRef.current = term;

    // Resize observer to keep fit updated
    const ro = new ResizeObserver(() => {
      try { fit.fit(); } catch {}
    });
    ro.observe(document.getElementById(containerId));

    return () => {
      ro.disconnect();
      try { term.dispose(); } catch {}
    };
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, []);

  // Write new output into terminal when `output` prop changes.
  useEffect(() => {
    if (!termRef.current || output == null) return;
    try {
      // print with newline separation
      // ensure not to double newlines if the output already has trailing newline
      const text = String(output);
      termRef.current.writeln(text.replace(/\r/g, ""));
    } catch (e) {
      // ignore
    }
  }, [output]);

  // Auto-focus when parent asks
  useEffect(() => {
    if (!termRef.current) return;
    if (autoFocusWhen) {
      // focus xterm helper
      setTimeout(() => {
        const ta = document.querySelector(`#${containerId} .xterm-helper-textarea`);
        if (ta) {
          try {
            ta.focus();
            const len = ta.value?.length || 0;
            ta.setSelectionRange(len, len);
          } catch {}
        } else {
          const cont = document.getElementById(containerId);
          if (cont) cont.focus();
        }
      }, 50);
    }
  }, [autoFocusWhen]);

  return (
    <div
      id={containerId}
      style={{
        width: "100%",
        height: "180px",
        background: "#1e1e1e",
        borderTop: "1px solid #333",
      }}
    />
  );
}