import { build_link_handler } from "./links.js";

// drawImage on a composited WebGL canvas returns blank pixels unless
// preserveDrawingBuffer is set (needed by the pinch overlay snapshot); this must
// run before xterm.js's WebglAddon creates its context.
function ensurePreserveDrawingBuffer() {
    if (window.__zjPreserveDrawingBuffer) return;
    window.__zjPreserveDrawingBuffer = true;
    const orig = HTMLCanvasElement.prototype.getContext;
    HTMLCanvasElement.prototype.getContext = function (type, options) {
        if (type === "webgl" || type === "webgl2") {
            options = Object.assign({}, options || {}, {
                preserveDrawingBuffer: true,
            });
        }
        return orig.call(this, type, options);
    };
}

export function initTerminal() {
    ensurePreserveDrawingBuffer();
    const term = new Terminal({
        fontFamily: "Monospace",
        allowProposedApi: true,
        scrollback: 0,
    });
    window.term = term;
    const fitAddon = new FitAddon.FitAddon();
    const clipboardAddon = new ClipboardAddon.ClipboardAddon();

    const { linkHandler, activateLink } = build_link_handler();
    const webLinksAddon = new WebLinksAddon.WebLinksAddon(
        activateLink,
        linkHandler
    );
    term.options.linkHandler = linkHandler;

    const webglAddon = new WebglAddon.WebglAddon();
    term.loadAddon(fitAddon);
    term.loadAddon(clipboardAddon);
    term.loadAddon(webLinksAddon);
    webglAddon.onContextLoss((e) => {
        webglAddon.dispose();
    });
    term.loadAddon(webglAddon);
    term.open(document.getElementById("terminal"));
    fitAddon.fit();
    term.focus();
    return { term, fitAddon };
}

export const MIN_FONT_SIZE_PX = 6;
export const MAX_FONT_SIZE_PX = 96;

export function applyFontSize(term, fitAddon, requestedPx) {
    const requested =
        typeof requestedPx === "number" && requestedPx > 0
            ? requestedPx
            : term.options.fontSize || 12;
    const effective = clampFontSize(requested);
    if (term.options.fontSize !== effective) {
        term.options.fontSize = effective;
    }
    try {
        fitAddon.fit();
    } catch (e) {
    }
}

export function clampFontSize(px) {
    const n = Math.round(Number(px) || 0);
    if (n < MIN_FONT_SIZE_PX) return MIN_FONT_SIZE_PX;
    if (n > MAX_FONT_SIZE_PX) return MAX_FONT_SIZE_PX;
    return n;
}