FetchNextSearchPageTask.java

/*
 * Copyright (C) 2017 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.example.github.repository;

import com.android.example.github.api.ApiResponse;
import com.android.example.github.api.GithubService;
import com.android.example.github.api.RepoSearchResponse;
import com.android.example.github.db.GithubDb;
import com.android.example.github.vo.RepoSearchResult;
import com.android.example.github.vo.Resource;

import android.arch.lifecycle.LiveData;
import android.arch.lifecycle.MutableLiveData;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import retrofit2.Response;

/**
 * A task that reads the search result in the database and fetches the next page, if it has one.
 */
public class FetchNextSearchPageTask implements Runnable {
    private final MutableLiveData<Resource<Boolean>> liveData = new MutableLiveData<>();
    private final String query;
    private final GithubService githubService;
    private final GithubDb db;

    FetchNextSearchPageTask(String query, GithubService githubService, GithubDb db) {
        this.query = query;
        this.githubService = githubService;
        this.db = db;
    }

    @Override
    public void run() {
        RepoSearchResult current = db.repoDao().findSearchResult(query);
        if(current == null) {
            liveData.postValue(null);
            return;
        }
        final Integer nextPage = current.next;
        if (nextPage == null) {
            liveData.postValue(Resource.success(false));
            return;
        }
        try {
            Response<RepoSearchResponse> response = githubService
                    .searchRepos(query, nextPage).execute();
            ApiResponse<RepoSearchResponse> apiResponse = new ApiResponse<>(response);
            if (apiResponse.isSuccessful()) {
                // we merge all repo ids into 1 list so that it is easier to fetch the result list.
                List<Integer> ids = new ArrayList<>();
                ids.addAll(current.repoIds);
                //noinspection ConstantConditions
                ids.addAll(apiResponse.body.getRepoIds());
                RepoSearchResult merged = new RepoSearchResult(query, ids,
                        apiResponse.body.getTotal(), apiResponse.getNextPage());
                try {
                    db.beginTransaction();
                    db.repoDao().insert(merged);
                    db.repoDao().insertRepos(apiResponse.body.getItems());
                    db.setTransactionSuccessful();
                } finally {
                    db.endTransaction();
                }
                liveData.postValue(Resource.success(apiResponse.getNextPage() != null));
            } else {
                liveData.postValue(Resource.error(apiResponse.errorMessage, true));
            }
        } catch (IOException e) {
            liveData.postValue(Resource.error(e.getMessage(), true));
        }
    }

    LiveData<Resource<Boolean>> getLiveData() {
        return liveData;
    }
}