package org.openautonomousconnection.luascript.fx;

import javafx.scene.web.WebEngine;
import org.openautonomousconnection.luascript.hosts.ResourceHost;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.URL;
import java.net.URLConnection;
import java.nio.charset.StandardCharsets;
import java.util.Objects;

/**
 * ResourceHost that loads script src via URLConnection.
 *
 * <p>Relative URLs are resolved against the current WebEngine location.</p>
 */
public final class FxWebViewResourceHost implements ResourceHost {

    private final WebEngine engine;

    /**
     * Creates a new resource host.
     *
     * @param engine web engine
     */
    public FxWebViewResourceHost(WebEngine engine) {
        this.engine = Objects.requireNonNull(engine, "engine");
    }

    @Override
    public String readText(String src) throws Exception {
        Objects.requireNonNull(src, "src");
        String trimmed = src.trim();
        if (trimmed.isEmpty()) throw new IllegalArgumentException("src is empty");

        String base = FxThreadBridge.callAndWait(engine::getLocation);
        URL url = (base == null || base.isBlank())
                ? new URL(trimmed)
                : new URL(new URL(base), trimmed);

        URLConnection con = url.openConnection();
        con.setUseCaches(false);

        try (BufferedReader br = new BufferedReader(new InputStreamReader(con.getInputStream(), StandardCharsets.UTF_8))) {
            StringBuilder sb = new StringBuilder(4096);
            char[] buf = new char[8192];
            int r;
            while ((r = br.read(buf)) >= 0) {
                sb.append(buf, 0, r);
            }
            return sb.toString();
        }
    }
}