package org.gingercal.net;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

import android.content.Context;

/**
 * Mozilla roots shipped as assets/roots/<sha1(subject)>-<n>.der
 *
 * Roots are read from the APK once and kept: an app installed on the SD card loses its APK while the
 * card is shared over USB, and a failed read must not leave every server "untrusted" until a restart.
 */
public final class AssetRoots implements CertVerifier.RootStore {
    private final Context ctx;
    private Set<String> names;                                                  // asset file names, once listed
    private final Map<String, List<byte[]>> found = new HashMap<String, List<byte[]>>(); // by subject hash; null = none

    public AssetRoots(Context c) { ctx = c.getApplicationContext(); }

    public synchronized List<byte[]> find(byte[] subjectDer) {
        String h = CertVerifier.sha1Hex(subjectDer);
        if (found.containsKey(h)) return found.get(h);
        try {
            if (names == null) {
                String[] l = ctx.getAssets().list("roots");
                if (l == null || l.length == 0) return null; // APK unreadable right now: try again next time
                Set<String> n = new HashSet<String>();
                for (int i = 0; i < l.length; i++) n.add(l[i]);
                names = n;
            }
            List<byte[]> out = null;
            for (int i = 0; names.contains(h + "-" + i + ".der"); i++) {
                if (out == null) out = new ArrayList<byte[]>();
                out.add(readAll(ctx.getAssets().open("roots/" + h + "-" + i + ".der")));
            }
            found.put(h, out);
            return out;
        } catch (IOException e) {
            return null; // not cached: the next handshake reads again
        }
    }

    static byte[] readAll(InputStream in) throws IOException {
        try {
            ByteArrayOutputStream b = new ByteArrayOutputStream();
            byte[] buf = new byte[4096];
            int n;
            while ((n = in.read(buf)) > 0) b.write(buf, 0, n);
            return b.toByteArray();
        } finally {
            in.close();
        }
    }
}