package de.thedevstack.android.logcat.tasks;

import android.os.AsyncTask;
import android.widget.ArrayAdapter;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;

import de.thedevstack.android.logcat.Logging;

/**
 * Task to read the logcat of the App.
 * The command <code>logcat -d -v time</code> is used to load the logs.
 * This reader uses a white list to restrict the messages to display, otherwise it might be flooded with useless log messages.
 * The white list checks if a log messages contains one of the following strings:
 * <ul>
 *     <li>{@value Logging#LOG_TAG_PREFIX}</li>
 *     <li><code>E/</code> - for every error message</li>
 *     <li><code>W/</code> - for every warning message</li>
 * </ul>
 */
public class ReadLogCatAsyncTask extends AsyncTask<Void, Void, String[]> {
    /**
     * The array adapter to publish the log messages to.
     */
    private final ArrayAdapter<String> arrayAdapter;
    /**
     * The command to execute logcat.
     */
    private static final String[] LOG_CAT_CMD = { "logcat", "-d", "-v", "time"};
    /**
     * The white list to filter log messages.
     */
    private static final String[] WHITE_LIST = { Logging.getLogTagPrefix(), "E/", "W/" };

    /**
     * Initializes the Task with the array adapter to publish the log messages to.
     * @param arrayAdapter the array adapter
     */
    public ReadLogCatAsyncTask(ArrayAdapter<String> arrayAdapter) {
        this.arrayAdapter = arrayAdapter;
    }

    /**
     * Executes the logcat command, reads the output of the command and returns all log messages.
     * @param params no params will be passed. (interface compliance)
     * @return the array of log messages
     */
    @Override
    protected String[] doInBackground(Void... params) {
        ArrayList<String> logCatOutput = new ArrayList<>();
        BufferedReader bufferedReader = null;
        try {
            Process process = Runtime.getRuntime().exec(ReadLogCatAsyncTask.LOG_CAT_CMD);
            bufferedReader = new BufferedReader(new InputStreamReader(process.getInputStream()));
            String line = "";
            while ((line = bufferedReader.readLine()) != null) {
                logCatOutput.add(line);
            }
        } catch (IOException e) {
            Logging.e("ReadLogCat", "error while retrieving information from logcat: " + e.getMessage(), e);
        } finally {
            if (null != bufferedReader) {
                try {
                    bufferedReader.close();
                } catch (IOException e) {
                }
            }
        }
        logCatOutput.trimToSize();
        return logCatOutput.toArray(new String[0]);
    }

    /**
     * Clears the array adapter and adds the filtered log messages.
     * @param items all log messages
     */
    @Override
    protected void onPostExecute(String[] items) {
        this.arrayAdapter.clear();
        if (null != items && items.length > 0) {
            for (String item : items) {
                if (!filter(item)) {
                    this.arrayAdapter.add(item);
                }
            }
        }
    }

    /**
     * Checks whether a log message contains a white listed string or not.
     * @param item the item to filter
     * @return <code>true</code> if the string should be filtered (removed from the list) <code>false</code> otherwise.
     */
    protected boolean filter(String item) {
        for (String whiteListed : ReadLogCatAsyncTask.WHITE_LIST) {
            if (item.contains(whiteListed)) {
                return false;
            }
        }
        return true;
    }
}