implement fetching listings from remote instances

mastodon/src/main/java/org/joinmastodon/android/api/MastodonAPIRequest.java

@@ -20,9 +20,11 @@ import java.util.HashMap;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 import java.util.function.Consumer;
 
 import androidx.annotation.CallSuper;
+import androidx.annotation.Nullable;
 import androidx.annotation.StringRes;
 import me.grishka.appkit.api.APIRequest;
 import me.grishka.appkit.api.Callback;
@@ -44,7 +46,7 @@ public abstract class MastodonAPIRequest<T> extends APIRequest<T>{
 	TypeToken<T> respTypeToken;
 	Call okhttpCall;
 	Token token;
-	boolean canceled;
+	boolean canceled, isRemote;
 	Map<String, String> headers;
 	private ProgressDialog progressDialog;
 	protected boolean removeUnsupportedItems;
@@ -101,6 +103,21 @@ public abstract class MastodonAPIRequest<T> extends APIRequest<T>{
 		return this;
 	}
 
+	public MastodonAPIRequest<T> execRemote(String domain) {
+		return execRemote(domain, null);
+	}
+
+	public MastodonAPIRequest<T> execRemote(String domain, @Nullable AccountSession remoteSession) {
+		this.isRemote = true;
+		return Optional.ofNullable(remoteSession)
+				.or(() -> AccountSessionManager.getInstance().getLoggedInAccounts().stream()
+						.filter(acc -> acc.domain.equals(domain))
+						.findAny())
+				.map(AccountSession::getID)
+				.map(this::exec)
+				.orElse(this.execNoAuth(domain));
+	}
+
 	public MastodonAPIRequest<T> wrapProgress(Activity activity, @StringRes int message, boolean cancelable){
 		return wrapProgress(activity, message, cancelable, null);
 	}
@@ -167,6 +184,7 @@ public abstract class MastodonAPIRequest<T> extends APIRequest<T>{
 	@CallSuper
 	public void validateAndPostprocessResponse(T respObj, Response httpResponse) throws IOException{
 		if(respObj instanceof BaseModel){
+			((BaseModel) respObj).isRemote = isRemote;
 			((BaseModel) respObj).postprocess();
 		}else if(respObj instanceof List){
 			if(removeUnsupportedItems){
@@ -175,6 +193,7 @@ public abstract class MastodonAPIRequest<T> extends APIRequest<T>{
 					Object item=itr.next();
 					if(item instanceof BaseModel){
 						try{
+							((BaseModel) item).isRemote = isRemote;
 							((BaseModel) item).postprocess();
 						}catch(ObjectValidationException x){
 							Log.w(TAG, "Removing invalid object from list", x);
@@ -182,15 +201,20 @@ public abstract class MastodonAPIRequest<T> extends APIRequest<T>{
 						}
 					}
 				}
+				// no idea why we're post-processing twice, but well, as long
+				// as upstream does it like this, i don't wanna break anything
 				for(Object item:((List<?>) respObj)){
 					if(item instanceof BaseModel){
+						((BaseModel) item).isRemote = isRemote;
 						((BaseModel) item).postprocess();
 					}
 				}
 			}else{
 				for(Object item:((List<?>) respObj)){
-					if(item instanceof BaseModel)
+					if(item instanceof BaseModel) {
+						((BaseModel) item).isRemote = isRemote;
 						((BaseModel) item).postprocess();
+					}
 				}
 			}
 		}

mastodon/src/main/java/org/joinmastodon/android/api/requests/accounts/GetAccountByHandle.java

@@ -0,0 +1,15 @@
+package org.joinmastodon.android.api.requests.accounts;
+
+import org.joinmastodon.android.api.MastodonAPIRequest;
+import org.joinmastodon.android.model.Account;
+
+public class GetAccountByHandle extends MastodonAPIRequest<Account>{
+    /**
+     * note that this method usually only returns a result if the instance already knows about an
+     * account - so it makes sense for looking up local users, search might be preferred otherwise
+     */
+    public GetAccountByHandle(String acct){
+        super(HttpMethod.GET, "/accounts/lookup", Account.class);
+        addQueryParameter("acct", acct);
+    }
+}

mastodon/src/main/java/org/joinmastodon/android/api/session/AccountSessionManager.java

@@ -160,6 +160,11 @@ public class AccountSessionManager{
 		return sessions.get(id);
 	}
 
+	@Nullable
+	public AccountSession tryGetAccount(Account account) {
+		return sessions.get(account.getDomainFromURL() + "_" + account.id);
+	}
+
 	@Nullable
 	public AccountSession getLastActiveAccount(){
 		if(sessions.isEmpty() || lastActiveAccountID==null)