package de.robv.android.xposed;

import android.annotation.SuppressLint;
import android.content.Context;
import android.content.SharedPreferences;
import android.os.Environment;
import android.preference.PreferenceManager;
import android.util.Log;

import com.android.internal.util.XmlUtils;

import org.xmlpull.v1.XmlPullParserException;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;

import de.robv.android.xposed.services.FileResult;

/**
 * This class is basically the same as SharedPreferencesImpl from AOSP, but
 * read-only and without listeners support. Instead, it is made to be
 * compatible with all ROMs.
 */
public final class XSharedPreferences implements SharedPreferences {
    private static final String TAG = "XSharedPreferences";
    private final File mFile;
    private final String mFilename;
    private Map<String, Object> mMap;
    private boolean mLoaded = false;
    private long mLastModified;
    private long mFileSize;

    /**
     * Read settings from the specified file.
     *
     * @param prefFile The file to read the preferences from.
     */
    public XSharedPreferences(File prefFile) {
        mFile = prefFile;
        mFilename = mFile.getAbsolutePath();
        startLoadFromDisk();
    }

    /**
     * Read settings from the default preferences for a package.
     * These preferences are returned by {@link PreferenceManager#getDefaultSharedPreferences}.
     *
     * @param packageName The package name.
     */
    public XSharedPreferences(String packageName) {
        this(packageName, packageName + "_preferences");
    }

    /**
     * Read settings from a custom preferences file for a package.
     * These preferences are returned by {@link Context#getSharedPreferences(String, int)}.
     *
     * @param packageName  The package name.
     * @param prefFileName The file name without ".xml".
     */
    public XSharedPreferences(String packageName, String prefFileName) {
        mFile = new File(Environment.getDataDirectory(), "data/" + packageName + "/shared_prefs/" + prefFileName + ".xml");
        mFilename = mFile.getAbsolutePath();
        startLoadFromDisk();
    }

    /**
     * Tries to make the preferences file world-readable.
     *
     * <p><strong>Warning:</strong> This is only meant to work around permission "fix" functions that are part
     * of some recoveries. It doesn't replace the need to open preferences with {@code MODE_WORLD_READABLE}
     * in the module's UI code. Otherwise, Android will set stricter permissions again during the next save.
     *
     * <p>This will only work if executed as root (e.g. {@code initZygote()}) and only if SELinux is disabled.
     *
     * @return {@code true} in case the file could be made world-readable.
     */
    @SuppressLint("SetWorldReadable")
    public boolean makeWorldReadable() {
        if (!SELinuxHelper.getAppDataFileService().hasDirectFileAccess())
            return false; // It doesn't make much sense to make the file readable if we wouldn't be able to access it anyway.

        if (!mFile.exists()) // Just in case - the file should never be created if it doesn't exist.
            return false;

        return mFile.setReadable(true, false);
    }

    /**
     * Returns the file that is backing these preferences.
     *
     * <p><strong>Warning:</strong> The file might not be accessible directly.
     */
    public File getFile() {
        return mFile;
    }

    private void startLoadFromDisk() {
        synchronized (this) {
            mLoaded = false;
        }
        new Thread("XSharedPreferences-load") {
            @Override
            public void run() {
                synchronized (XSharedPreferences.this) {
                    loadFromDiskLocked();
                }
            }
        }.start();
    }

    @SuppressWarnings({"rawtypes", "unchecked"})
    private void loadFromDiskLocked() {
        if (mLoaded) {
            return;
        }

        Map map = null;
        FileResult result = null;
        try {
            result = SELinuxHelper.getAppDataFileService().getFileInputStream(mFilename, mFileSize, mLastModified);
            if (result.stream != null) {
                map = XmlUtils.readMapXml(result.stream);
                result.stream.close();
            } else {
                // The file is unchanged, keep the current values
                map = mMap;
            }
        } catch (XmlPullParserException e) {
            Log.w(TAG, "getSharedPreferences", e);
        } catch (FileNotFoundException ignored) {
            // SharedPreferencesImpl has a canRead() check, so it doesn't log anything in case the file doesn't exist
        } catch (IOException e) {
            Log.w(TAG, "getSharedPreferences", e);
        } finally {
            if (result != null && result.stream != null) {
                try {
                    result.stream.close();
                } catch (RuntimeException rethrown) {
                    throw rethrown;
                } catch (Exception ignored) {
                }
            }
        }

        mLoaded = true;
        if (map != null) {
            mMap = map;
            mLastModified = result.mtime;
            mFileSize = result.size;
        } else {
            mMap = new HashMap<>();
        }
        notifyAll();
    }

    /**
     * Reload the settings from file if they have changed.
     *
     * <p><strong>Warning:</strong> With enforcing SELinux, this call might be quite expensive.
     */
    public synchronized void reload() {
        if (hasFileChanged())
            startLoadFromDisk();
    }

    /**
     * Check whether the file has changed since the last time it has been loaded.
     *
     * <p><strong>Warning:</strong> With enforcing SELinux, this call might be quite expensive.
     */
    public synchronized boolean hasFileChanged() {
        try {
            FileResult result = SELinuxHelper.getAppDataFileService().statFile(mFilename);
            return mLastModified != result.mtime || mFileSize != result.size;
        } catch (FileNotFoundException ignored) {
            // SharedPreferencesImpl doesn't log anything in case the file doesn't exist
            return true;
        } catch (IOException e) {
            Log.w(TAG, "hasFileChanged", e);
            return true;
        }
    }

    private void awaitLoadedLocked() {
        while (!mLoaded) {
            try {
                wait();
            } catch (InterruptedException unused) {
            }
        }
    }

    /**
     * @hide
     */
    @Override
    public Map<String, ?> getAll() {
        synchronized (this) {
            awaitLoadedLocked();
            return new HashMap<>(mMap);
        }
    }

    /**
     * @hide
     */
    @Override
    public String getString(String key, String defValue) {
        synchronized (this) {
            awaitLoadedLocked();
            String v = (String) mMap.get(key);
            return v != null ? v : defValue;
        }
    }

    /**
     * @hide
     */
    @Override
    @SuppressWarnings("unchecked")
    public Set<String> getStringSet(String key, Set<String> defValues) {
        synchronized (this) {
            awaitLoadedLocked();
            Set<String> v = (Set<String>) mMap.get(key);
            return v != null ? v : defValues;
        }
    }

    /**
     * @hide
     */
    @Override
    public int getInt(String key, int defValue) {
        synchronized (this) {
            awaitLoadedLocked();
            Integer v = (Integer) mMap.get(key);
            return v != null ? v : defValue;
        }
    }

    /**
     * @hide
     */
    @Override
    public long getLong(String key, long defValue) {
        synchronized (this) {
            awaitLoadedLocked();
            Long v = (Long) mMap.get(key);
            return v != null ? v : defValue;
        }
    }

    /**
     * @hide
     */
    @Override
    public float getFloat(String key, float defValue) {
        synchronized (this) {
            awaitLoadedLocked();
            Float v = (Float) mMap.get(key);
            return v != null ? v : defValue;
        }
    }

    /**
     * @hide
     */
    @Override
    public boolean getBoolean(String key, boolean defValue) {
        synchronized (this) {
            awaitLoadedLocked();
            Boolean v = (Boolean) mMap.get(key);
            return v != null ? v : defValue;
        }
    }

    /**
     * @hide
     */
    @Override
    public boolean contains(String key) {
        synchronized (this) {
            awaitLoadedLocked();
            return mMap.containsKey(key);
        }
    }

    /**
     * @deprecated Not supported by this implementation.
     */
    @Deprecated
    @Override
    public Editor edit() {
        throw new UnsupportedOperationException("read-only implementation");
    }

    /**
     * @deprecated Not supported by this implementation.
     */
    @Deprecated
    @Override
    public void registerOnSharedPreferenceChangeListener(OnSharedPreferenceChangeListener listener) {
        throw new UnsupportedOperationException("listeners are not supported in this implementation");
    }

    /**
     * @deprecated Not supported by this implementation.
     */
    @Deprecated
    @Override
    public void unregisterOnSharedPreferenceChangeListener(OnSharedPreferenceChangeListener listener) {
        throw new UnsupportedOperationException("listeners are not supported in this implementation");
    }

}
