import { useCallback, useEffect, useRef, useState } from "react";
import { Terminal } from "@xterm/xterm";
import { FitAddon } from "@xterm/addon-fit";
import { WebglAddon } from "@xterm/addon-webgl";
import { WebLinksAddon } from "@xterm/addon-web-links";
import { openUrl } from "@tauri-apps/plugin-opener";
import "@xterm/xterm/css/xterm.css";
import { useTerminal } from "../../hooks/useTerminal";
import { UrlDetector } from "../../lib/urlDetector";
import UrlToast from "./UrlToast";

interface Props {
  sessionId: string;
  active: boolean;
}

export default function TerminalView({ sessionId, active }: Props) {
  const containerRef = useRef<HTMLDivElement>(null);
  const terminalContainerRef = useRef<HTMLDivElement>(null);
  const termRef = useRef<Terminal | null>(null);
  const fitRef = useRef<FitAddon | null>(null);
  const webglRef = useRef<WebglAddon | null>(null);
  const detectorRef = useRef<UrlDetector | null>(null);
  const { sendInput, resize, onOutput, onExit } = useTerminal();

  const [detectedUrl, setDetectedUrl] = useState<string | null>(null);

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

    const term = new Terminal({
      cursorBlink: true,
      fontSize: 14,
      fontFamily: "'JetBrains Mono', 'Fira Code', 'Cascadia Code', Menlo, Monaco, monospace",
      theme: {
        background: "#0d1117",
        foreground: "#e6edf3",
        cursor: "#58a6ff",
        selectionBackground: "#264f78",
        black: "#484f58",
        red: "#ff7b72",
        green: "#3fb950",
        yellow: "#d29922",
        blue: "#58a6ff",
        magenta: "#bc8cff",
        cyan: "#39d353",
        white: "#b1bac4",
        brightBlack: "#6e7681",
        brightRed: "#ffa198",
        brightGreen: "#56d364",
        brightYellow: "#e3b341",
        brightBlue: "#79c0ff",
        brightMagenta: "#d2a8ff",
        brightCyan: "#56d364",
        brightWhite: "#f0f6fc",
      },
    });

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

    // Web links addon — opens URLs in host browser via Tauri, with a permissive regex
    // that matches URLs even if they lack trailing path segments (the default regex
    // misses OAuth URLs that end mid-line).
    const urlRegex = /https?:\/\/[^\s'"\x07]+/;
    const webLinksAddon = new WebLinksAddon((_event, uri) => {
      openUrl(uri).catch((e) => console.error("Failed to open URL:", e));
    }, { urlRegex });
    term.loadAddon(webLinksAddon);

    term.open(containerRef.current);

    // WebGL addon is loaded/disposed dynamically in the active effect
    // to avoid exhausting the browser's limited WebGL context pool.

    fitAddon.fit();
    termRef.current = term;
    fitRef.current = fitAddon;

    // Send initial size
    resize(sessionId, term.cols, term.rows);

    // Handle user input -> backend
    const inputDisposable = term.onData((data) => {
      sendInput(sessionId, data);
    });

    // Handle backend output -> terminal
    let aborted = false;

    const detector = new UrlDetector((url) => setDetectedUrl(url));
    detectorRef.current = detector;

    const outputPromise = onOutput(sessionId, (data) => {
      if (aborted) return;
      term.write(data);
      detector.feed(data);
    }).then((unlisten) => {
      if (aborted) unlisten();
      return unlisten;
    });

    const exitPromise = onExit(sessionId, () => {
      if (aborted) return;
      term.write("\r\n\x1b[33m[Session ended]\x1b[0m\r\n");
    }).then((unlisten) => {
      if (aborted) unlisten();
      return unlisten;
    });

    // Handle resize (throttled via requestAnimationFrame to avoid excessive calls).
    // Skip resize work for hidden terminals — containerRef will have 0 dimensions.
    let resizeRafId: number | null = null;
    const resizeObserver = new ResizeObserver(() => {
      if (resizeRafId !== null) return;
      const el = containerRef.current;
      if (!el || el.offsetWidth === 0 || el.offsetHeight === 0) return;
      resizeRafId = requestAnimationFrame(() => {
        resizeRafId = null;
        if (!containerRef.current || containerRef.current.offsetWidth === 0) return;
        fitAddon.fit();
        resize(sessionId, term.cols, term.rows);
      });
    });
    resizeObserver.observe(containerRef.current);

    return () => {
      aborted = true;
      detector.dispose();
      detectorRef.current = null;
      inputDisposable.dispose();
      outputPromise.then((fn) => fn?.());
      exitPromise.then((fn) => fn?.());
      if (resizeRafId !== null) cancelAnimationFrame(resizeRafId);
      resizeObserver.disconnect();
      try { webglRef.current?.dispose(); } catch { /* may already be disposed */ }
      webglRef.current = null;
      term.dispose();
    };
  }, [sessionId]); // eslint-disable-line react-hooks/exhaustive-deps

  // Manage WebGL lifecycle and re-fit when tab becomes active.
  // Only the active terminal holds a WebGL context to avoid exhausting
  // the browser's limited pool (~8-16 contexts).
  useEffect(() => {
    const term = termRef.current;
    if (!term) return;

    if (active) {
      // Attach WebGL renderer
      if (!webglRef.current) {
        try {
          const addon = new WebglAddon();
          addon.onContextLoss(() => {
            try { addon.dispose(); } catch { /* ignore */ }
            webglRef.current = null;
          });
          term.loadAddon(addon);
          webglRef.current = addon;
        } catch {
          // WebGL not available, canvas renderer is fine
        }
      }
      fitRef.current?.fit();
      term.focus();
    } else {
      // Release WebGL context for inactive terminals
      if (webglRef.current) {
        try { webglRef.current.dispose(); } catch { /* ignore */ }
        webglRef.current = null;
      }
    }
  }, [active]);

  // Auto-dismiss toast after 30 seconds
  useEffect(() => {
    if (!detectedUrl) return;
    const timer = setTimeout(() => setDetectedUrl(null), 30_000);
    return () => clearTimeout(timer);
  }, [detectedUrl]);

  const handleOpenUrl = useCallback(() => {
    if (detectedUrl) {
      openUrl(detectedUrl).catch((e) =>
        console.error("Failed to open URL:", e),
      );
      setDetectedUrl(null);
    }
  }, [detectedUrl]);

  return (
    <div
      ref={terminalContainerRef}
      className={`w-full h-full relative ${active ? "" : "hidden"}`}
    >
      {detectedUrl && (
        <UrlToast
          url={detectedUrl}
          onOpen={handleOpenUrl}
          onDismiss={() => setDetectedUrl(null)}
        />
      )}
      <div
        ref={containerRef}
        className="w-full h-full"
        style={{ padding: "8px" }}
      />
    </div>
  );
}