package nodomain.freeyourgadget.gadgetbridge.util;

import android.content.ContentResolver;
import android.content.Context;
import android.net.Uri;
import android.os.Environment;
import android.support.annotation.NonNull;
import android.util.Log;

import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.nio.channels.FileChannel;
import java.util.ArrayList;
import java.util.List;

import nodomain.freeyourgadget.gadgetbridge.GBApplication;

public class FileUtils {
    // Don't use slf4j here -- would be a bootstrapping problem
    private static final String TAG = "FileUtils";

    /**
     * Copies the the given sourceFile to destFile, overwriting it, in case it exists.
     *
     * @param sourceFile
     * @param destFile
     * @throws IOException
     */
    public static void copyFile(File sourceFile, File destFile) throws IOException {
        if (!sourceFile.exists()) {
            throw new IOException("Does not exist: " + sourceFile.getAbsolutePath());
        }
        copyFile(new FileInputStream(sourceFile), new FileOutputStream(destFile));
    }

    private static void copyFile(FileInputStream sourceStream, FileOutputStream destStream) throws IOException {
        try (FileChannel fromChannel = sourceStream.getChannel(); FileChannel toChannel = destStream.getChannel()) {
            fromChannel.transferTo(0, fromChannel.size(), toChannel);
        }
    }

    public static void copyURItoFile(Context ctx, Uri uri, File destFile) throws IOException {
        if (uri.getPath().equals(destFile.getPath())) {
            return;
        }

        ContentResolver cr = ctx.getContentResolver();
        InputStream fin;
        try {
            fin = new BufferedInputStream(cr.openInputStream(uri));
        } catch (FileNotFoundException e) {
            e.printStackTrace();
            return;
        }
        FileOutputStream fout = new FileOutputStream(destFile);
        byte[] buf = new byte[4096];
        while (fin.available() > 0) {
            int bytes = fin.read(buf);
            fout.write(buf, 0, bytes);
        }
        fin.close();
        fout.close();
    }

    public static String getStringFromFile(File file) throws IOException {
        FileInputStream fin = new FileInputStream(file);

        BufferedReader reader = new BufferedReader(new InputStreamReader(fin));
        StringBuilder sb = new StringBuilder();
        String line;
        while ((line = reader.readLine()) != null) {
            sb.append(line).append("\n");
        }
        reader.close();
        fin.close();
        return sb.toString();
    }

    /**
     * Returns the existing external storage dir. The directory is guaranteed to
     * exist and to be writable.
     *
     * @throws IOException when the directory is not available
     */
    public static File getExternalFilesDir() throws IOException {
        List<File> dirs = getWritableExternalFilesDirs();
        for (File dir : dirs) {
            if (canWriteTo(dir)) {
                return dir;
            }
        }
        throw new IOException("no writable external directory found");
    }

    private static boolean canWriteTo(File dir) {
        File file = new File(dir, "gbtest");
        try {
            FileOutputStream test = new FileOutputStream(file);
            try {
                test.close();
            } catch (IOException e) {
                // ignore
            }
            file.delete();
            return true;
        } catch (FileNotFoundException e) {
            return false;
        }
    }

    /**
     * Returns a list of directories to write to. The list is sorted by priority,
     * i.e. the first directory should be preferred, the last one is the least
     * preferred one.
     * <p/>
     * Note that the directories may not exist, so it is not guaranteed that you
     * can actually write to them. But when created, they *should* be writable.
     *
     * @return the list of writable directories
     * @throws IOException
     */
    @NonNull
    private static List<File> getWritableExternalFilesDirs() throws IOException {
        Context context = GBApplication.getContext();
        File[] dirs = context.getExternalFilesDirs(null);
        if (dirs == null) {
            throw new IOException("Unable to access external files dirs: null");
        }
        List<File> result = new ArrayList<>(dirs.length);
        if (dirs.length == 0) {
            throw new IOException("Unable to access external files dirs: 0");
        }
        for (int i = 0; i < dirs.length; i++) {
            File dir = dirs[i];
            if (dir == null || (!dir.exists() && !dir.mkdirs())) {
                continue;
            }
            // the first directory is also the primary external storage, i.e. the same as Environment.getExternalFilesDir()
            // TODO: check the mount state of *all* dirs when switching to later API level
            if (!dir.canWrite() || (i == 0 && !Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState()))) {
                Log.i(TAG, "ignoring non-writable external storage dir: " + dir);
                continue;
            }
            result.add(dir); // add last
        }
        return result;
    }

    /**
     * Reads the contents of the given InputStream into a byte array, but does not
     * read more than maxLen bytes. If the stream provides more than maxLen bytes,
     * an IOException is thrown.
     *
     * @param in     the stream to read from
     * @param maxLen the maximum number of bytes to read/return
     * @return the bytes read from the InputStream
     * @throws IOException when reading failed or when maxLen was exceeded
     */
    public static byte[] readAll(InputStream in, long maxLen) throws IOException {
        ByteArrayOutputStream out = new ByteArrayOutputStream(Math.max(8192, in.available()));
        byte[] buf = new byte[8192];
        int read = 0;
        long totalRead = 0;
        while ((read = in.read(buf)) > 0) {
            out.write(buf, 0, read);
            totalRead += read;
            if (totalRead > maxLen) {
                throw new IOException("Too much data to read into memory. Got already " + totalRead + buf);
            }
        }
        return out.toByteArray();
    }
}