package paris.tourolle.darkroom;

import android.app.Activity;
import android.content.ActivityNotFoundException;
import android.content.Context;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.util.Log;

/**
 * The system's folder picker, for an album's folder on this device (FR-EXP-10).
 *
 * <h2>Why an activity of its own</h2>
 *
 * <p>{@code ACTION_OPEN_DOCUMENT_TREE} answers through
 * {@code onActivityResult}, and the main activity is {@code NativeActivity},
 * whose result callback is not ours to override. So this one exists only to
 * ask: it starts the picker, takes the answer, and finishes — no layout, a
 * translucent theme, nothing on screen but the system's own chooser, which has
 * its own "New folder".
 *
 * <p>The answer is left in a static for Rust to poll ({@link #poll}), rather
 * than called back into native code: a callback would need a registered
 * native method and a thread to deliver on, and a poll from the Slint timer
 * that is already running is one static call.
 *
 * <h2>The grant</h2>
 *
 * <p>A tree URI is usable only while its permission is held, and a plain
 * result grants it until the process dies. {@code takePersistableUriPermission}
 * keeps it across restarts — an album's folder is chosen once and exported to
 * for months.
 */
public final class FolderPicker extends Activity {
    private static final String TAG = "DarkRoom";
    private static final int REQUEST = 0x5AF;

    /** The last answer: a tree URI, "" for a cancel, null while none has come. */
    private static volatile String answer = null;

    /**
     * Start asking. Clears any answer left from before.
     *
     * <p>Takes a {@code Context} rather than an {@code Activity}, because what
     * native code holds (ndk_context's handle) is the application context,
     * and starting an activity from one that is not an activity needs
     * {@code FLAG_ACTIVITY_NEW_TASK} — without it the call throws. The picker
     * shares the app's task affinity, so it still opens over the app and Back
     * still returns to it.
     */
    public static void start(Context from) {
        answer = null;
        Intent intent = new Intent(from, FolderPicker.class);
        if (!(from instanceof Activity)) {
            intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        }
        from.startActivity(intent);
    }

    /**
     * The answer, once: a tree URI, "" if the user backed out, or null while
     * the picker is still open. Reading it clears it, so a second poll after a
     * cancel does not see the cancel again.
     */
    public static String poll() {
        String a = answer;
        if (a != null) {
            answer = null;
        }
        return a;
    }

    @Override
    protected void onCreate(Bundle state) {
        super.onCreate(state);
        // Recreated after a rotation with the picker already up: asking again
        // would stack a second chooser over the first.
        if (state != null) {
            return;
        }
        Intent pick = new Intent(Intent.ACTION_OPEN_DOCUMENT_TREE);
        pick.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION
                | Intent.FLAG_GRANT_WRITE_URI_PERMISSION
                | Intent.FLAG_GRANT_PERSISTABLE_URI_PERMISSION);
        try {
            startActivityForResult(pick, REQUEST);
        } catch (ActivityNotFoundException e) {
            Log.w(TAG, "no folder picker on this device", e);
            answer = "";
            finish();
        }
    }

    @Override
    protected void onActivityResult(int request, int result, Intent data) {
        if (request != REQUEST) {
            return;
        }
        Uri tree = (result == RESULT_OK && data != null) ? data.getData() : null;
        if (tree == null) {
            answer = "";
        } else {
            try {
                getContentResolver().takePersistableUriPermission(tree,
                        Intent.FLAG_GRANT_READ_URI_PERMISSION
                                | Intent.FLAG_GRANT_WRITE_URI_PERMISSION);
            } catch (SecurityException e) {
                // Still usable this session; said in the log so a folder that
                // stops working after a restart has an explanation.
                Log.w(TAG, "the folder grant could not be kept: " + tree, e);
            }
            answer = tree.toString();
        }
        finish();
    }
}