package com.keylesspalace.tusky.util;

import android.content.Context;
import android.graphics.drawable.Drawable;
import android.os.AsyncTask;
import android.util.Log;
import android.util.Pair;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;

import com.keylesspalace.tusky.R;

import java.io.EOFException;
import java.io.File;
import java.io.FilenameFilter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import de.c1710.filemojicompat.FileEmojiCompatConfig;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;
import okio.BufferedSink;
import okio.Okio;
import okio.Source;


/**
 * This class bundles information about an emoji font as well as many convenient actions.
 */
public class EmojiCompatFont {
    private static final String TAG = "EmojiCompatFont";
    /**
     * This String represents the sub-directory the fonts are stored in.
     */
    private static final String DIRECTORY = "emoji";

    // These are the items which are also present in the JSON files
    private final String name, display, url;
    // The thumbnail image and the caption are provided as resource ids
    private final int img, caption;
    // The version is stored as a String in the x.xx.xx format (to be able to compare versions)
    private final String version;
    private final int[] versionCode;
    private AsyncTask fontDownloader;
    // The system font gets some special behavior...
    private static final EmojiCompatFont SYSTEM_DEFAULT =
            new EmojiCompatFont("system-default",
                    "System Default",
                    R.string.caption_systememoji,
                    R.drawable.ic_emoji_34dp,
                    "",
                    "0");
    private static final EmojiCompatFont BLOBMOJI =
            new EmojiCompatFont("Blobmoji",
                    "Blobmoji",
                    R.string.caption_blobmoji,
                    R.drawable.ic_blobmoji,
                    "https://tusky.app/hosted/emoji/BlobmojiCompat.ttf",
                    "12.0.0"
            );
    private static final EmojiCompatFont TWEMOJI =
            new EmojiCompatFont("Twemoji",
                    "Twemoji",
                    R.string.caption_twemoji,
                    R.drawable.ic_twemoji,
                    "https://tusky.app/hosted/emoji/TwemojiCompat.ttf",
                    "12.0.0"
            );
    private static final EmojiCompatFont NOTOEMOJI =
            new EmojiCompatFont("NotoEmoji",
                    "Noto Emoji",
                    R.string.caption_notoemoji,
                    R.drawable.ic_notoemoji,
                    "https://tusky.app/hosted/emoji/NotoEmojiCompat.ttf",
                    "11.0.0"
                    );

    /**
     * This array stores all available EmojiCompat fonts.
     * References to them can simply be saved by saving their indices
     */
    public static final EmojiCompatFont[] FONTS = {SYSTEM_DEFAULT, BLOBMOJI, TWEMOJI, NOTOEMOJI};
    // A list of all available font files and whether they are older than the current version or not
    // They are ordered by there version codes in ascending order
    private ArrayList<Pair<File, int[]>> existingFontFiles;

    private EmojiCompatFont(String name,
                            String display,
                            int caption,
                            int img,
                            String url,
                            String version) {
        this.name = name;
        this.display = display;
        this.caption = caption;
        this.img = img;
        this.url = url;
        this.version = version;
        this.versionCode = getVersionCode(version);
    }

    /**
     * Returns the Emoji font associated with this ID
     * @param id the ID of this font
     * @return the corresponding font. Will default to SYSTEM_DEFAULT if not in range.
     */
    public static EmojiCompatFont byId(int id) {
        if(id >= 0 && id < FONTS.length) {
            return FONTS[id];
        }
        else {
            return SYSTEM_DEFAULT;
        }
    }

    public int getId() {
        return Arrays.asList(FONTS).indexOf(this);
    }

    public String getName() {
        return name;
    }


    public String getDisplay(Context context) {
        return this != SYSTEM_DEFAULT ? display : context.getString(R.string.system_default);
    }

    public String getCaption(Context context) {
        return context.getResources().getString(caption);
    }

    public String getUrl() {
        return url;
    }

    public Drawable getThumb(Context context) {
        return context.getResources().getDrawable(img);
    }

    public String getVersion() {
        return version;
    }

    public int[] getVersionCode() {
        return versionCode;
    }

    /**
     * This method will return the actual font file (regardless of its existence) for
     * the current version (not necessarily the latest!).
     * @return The font (TTF) file or null if called on SYSTEM_FONT
     */
    @Nullable
    private File getFont(Context context) {
        if(this != SYSTEM_DEFAULT) {
            File directory = new File(context.getExternalFilesDir(null), DIRECTORY);
            return new File(directory, this.getName() + this.getVersion() + ".ttf");
        }
        else {
            return null;
        }
    }


    public FileEmojiCompatConfig getConfig(Context context) {
        return new FileEmojiCompatConfig(context, getLatestFontFile(context));
    }

    public boolean isDownloaded(Context context) {
        // The existence of the current version is actually checked twice, although the first method should
        // be much faster and more common.
        return this == SYSTEM_DEFAULT || getFont(context) != null
                && (getFont(context).exists() || newerFileExists(context));
    }

    /**
     * Checks whether there is already a font version that satisfies the current version, i.e. it
     * has a higher or equal version code.
     * @param context The Context
     * @return Whether there is a font file with a higher or equal version code to the current
     */
    private boolean newerFileExists(Context context) {
        loadExistingFontFiles(context);
        if (!existingFontFiles.isEmpty())
            // The last file is already the newest one...
            return compareVersions(existingFontFiles.get(existingFontFiles.size() - 1).second,
                    getVersionCode()) >= 0;
        return false;
    }

    /**
     * Downloads the TTF file for this font
     * @param listeners The listeners which will be notified when the download has been finished
     */
    public void downloadFont(Context context, Downloader.EmojiDownloadListener... listeners) {
        if(this != SYSTEM_DEFAULT) {
            // Additionally run a cleanup process after the download has been successful.
            Downloader.EmojiDownloadListener cleanup = font -> deleteOldVersions(context);

            List<Downloader.EmojiDownloadListener> allListeners
                    = new ArrayList<>(Arrays.asList(listeners));
            allListeners.add(cleanup);
            Downloader.EmojiDownloadListener[] allListenersA =
                    new Downloader.EmojiDownloadListener[allListeners.size()];

            fontDownloader = new Downloader(
                    this,
                    allListeners.toArray(allListenersA))
                    .execute(getFont(context));
        }
        else {
            for(Downloader.EmojiDownloadListener listener: listeners) {
                // The system emoji font is always downloaded...
                listener.onDownloaded(this);
            }
        }
    }

    /**
     * Deletes any older version of a font
     * @param context The current Context
     */
    private void deleteOldVersions(Context context) {
        loadExistingFontFiles(context);
        Log.d(TAG, "deleting old versions...");

        Log.d(TAG, String.format("deleteOldVersions: Found %d other font files", existingFontFiles.size()));
        for (Pair<File, int[]> fileExists : existingFontFiles) {
            if (compareVersions(fileExists.second, getVersionCode()) < 0) {
                    File file = fileExists.first;
                    // Uses side effects!
                    Log.d(TAG, String.format("Deleted %s successfully: %s", file.getAbsolutePath(),
                            file.delete()));
                }
        }
    }

    private static final Comparator<Pair<File, int[]>> pairComparator = (o1, o2) -> compareVersions(o1.second, o2.second);


    /**
     * Loads all font files that are inside the files directory into an ArrayList with the information
     * on whether they are older than the currently available version or not.
     * @param context The Context
     */
    private void loadExistingFontFiles(Context context) {
        // Only load it once
        if (this.existingFontFiles == null) {
            // If we call this on the system default font, just return nothing...
            if (this == SYSTEM_DEFAULT) {
                existingFontFiles = new ArrayList<>(0);
            }

            File directory = new File(context.getExternalFilesDir(null), DIRECTORY);
            // It will search for old versions using a regex that matches the font's name plus
            // (if present) a version code. No version code will be regarded as version 0.
            Pattern fontRegex = Pattern.compile(getName() + "(\\d+(\\.\\d+)*)?" + "\\.ttf");


            FilenameFilter ttfFilter = (dir, name) -> name.endsWith(".ttf");
            File[] existingFontFiles = directory.isDirectory() ? directory.listFiles(ttfFilter) : new File[0];
            Log.d(TAG, String.format("loadExistingFontFiles: %d other font files found",
                    existingFontFiles.length));
            // This is actually the upper bound
            this.existingFontFiles = new ArrayList<>(existingFontFiles.length);


            for(File file : existingFontFiles) {
                Matcher matcher = fontRegex.matcher(file.getName());
                if (matcher.matches()) {
                    String version = matcher.group(1);
                    int[] versionCode = getVersionCode(version);
                    Pair<File, int[]> entry = new Pair<>(file, versionCode);
                    // https://stackoverflow.com/a/51893026
                    // Insert it in a sorted way
                    int index = Collections.binarySearch(this.existingFontFiles, entry, pairComparator);
                    if (index < 0) {
                        index = -index - 1;
                    }
                    this.existingFontFiles.add(index, entry);
                }
            }
        }
    }

    /**
     * Returns the current or latest version of this font file (if there is any)
     * @param context The Context
     * @return The file for this font with the current or (if not existent) highest version code or null if there is no file for this font.
     */
    private File getLatestFontFile(@NonNull Context context) {
        File current = getFont(context);
        if (current != null && current.exists())
            return current;
        loadExistingFontFiles(context);
        try {
            return existingFontFiles.get(existingFontFiles.size() - 1).first;
        } catch (IndexOutOfBoundsException e) {
            return getFont(context);
        }
    }

    private @Nullable
    int[] getVersionCode(@Nullable String version) {
        if (version == null)
            return null;
        String[] versions = version.split("\\.");
        int[] versionCodes = new int[versions.length];
        for (int i = 0; i < versions.length; i++)
            versionCodes[i] = parseInt(versions[i], 0);
        return versionCodes;
    }

    /**
     * A small helper method to convert a String to an int with a default value
     *
     * @param value The String to be parsed
     * @param def   The default value
     * @return Either the String parsed to an int or - if this is not possible - the default value
     */
    private int parseInt(@Nullable String value, int def) {
        try {
            return Integer.parseInt(value);
        } catch (NumberFormatException | NullPointerException e) {
            e.printStackTrace();
            return def;
        }
    }

    /**
     * Compares two version codes to each other
     *
     * @param versionA The first version
     * @param versionB The second version
     * @return -1 if versionA < versionB, 1 if versionA > versionB and 0 otherwise
     */
    private static int compareVersions(int[] versionA, int[] versionB) {
        // This saves us much headache about handling a null version
        if (versionA == null)
            versionA = new int[]{0};

        int len = Math.max(versionB.length, versionA.length);

        int vA, vB;
        // Compare the versions
        for (int i = 0; i < len; i++) {
            // Just to make sure there is something specified here
            if (versionA.length > i) {
                vA = versionA[i];
            } else {
                vA = 0;
            }
            if (versionB.length > i) {
                vB = versionB[i];
            } else {
                vB = 0;
            }

            // It needs to be decided on the next level
            if (vB == vA)
                continue;
            // Okay, is version B newer or version A?
            return Integer.compare(vA, vB);
        }

        // The versions are equal
        return 0;
    }

    /**
     * Stops downloading the font. If no one started a font download, nothing happens.
     */
    public void cancelDownload() {
        if(fontDownloader != null) {
            fontDownloader.cancel(false);
            fontDownloader = null;
        }
    }

    /**
     * This class is used to easily manage the download of a font
     */
    public static class Downloader extends AsyncTask<File, Float, File> {
        // All interested objects/methods
        private final EmojiDownloadListener[] listeners;
        // The MIME-Type which might be unnecessary
        private static final String MIME = "application/woff";
        // The font belonging to this download
        private final EmojiCompatFont font;
        private static final String TAG = "Emoji-Font Downloader";
        private static long CHUNK_SIZE = 4096;
        private boolean failed = false;

        Downloader(EmojiCompatFont font, EmojiDownloadListener... listeners) {
            super();
            this.listeners = listeners;
            this.font = font;
        }

        @Override
        protected File doInBackground(File... files){
            // Only download to one file...
            File downloadFile = files[0];
            try {
                // It is possible (and very likely) that the file does not exist yet
                if (!downloadFile.exists()) {
                    downloadFile.getParentFile().mkdirs();
                    downloadFile.createNewFile();
                }
                OkHttpClient client = new OkHttpClient();
                Request request = new Request.Builder().url(font.getUrl())
                        .addHeader("Content-Type", MIME)
                        .build();
                Response response = client.newCall(request).execute();
                BufferedSink sink = Okio.buffer(Okio.sink(downloadFile));
                Source source = null;
                try {
                    long size;
                    // Download!
                    if (response.body() != null
                            && response.isSuccessful()
                            && (size = response.body().contentLength()) > 0) {
                        float progress = 0;
                        source = response.body().source();
                        try {
                            while (!isCancelled()) {
                                sink.write(response.body().source(), CHUNK_SIZE);
                                progress += CHUNK_SIZE;
                                publishProgress(progress / size);
                            }
                        } catch (EOFException ex) {
                            /*
                             This means we've finished downloading the file since sink.write
                             will throw an EOFException when the file to be read is empty.
                            */
                        }
                    } else {
                        Log.e(TAG, "downloading " + font.getUrl() + " failed. No content to download.");
                        Log.e(TAG, "Status code: " + response.code());
                        failed = true;
                    }
                }
                finally {
                    if(source != null) {
                        source.close();
                    }
                    sink.close();
                    // This 'if' uses side effects to delete the File.
                    if(isCancelled() && !downloadFile.delete()) {
                        Log.e(TAG, "Could not delete file " + downloadFile);
                    }
                }
            } catch (IOException ex) {
                ex.printStackTrace();
                failed = true;
            }
            return downloadFile;
        }

        @Override
        public void onProgressUpdate(Float... progress) {
            for(EmojiDownloadListener listener: listeners) {
                listener.onProgress(progress[0]);
            }
        }

        @Override
        public void onPostExecute(File downloadedFile) {
            if(!failed && downloadedFile.exists()) {
                for (EmojiDownloadListener listener : listeners) {
                    listener.onDownloaded(font);
                }
            }
            else {
                fail(downloadedFile);
            }
        }

        private void fail(File failedFile) {
            if(failedFile.exists() && !failedFile.delete()) {
                Log.e(TAG, "Could not delete file " + failedFile);
            }
            for(EmojiDownloadListener listener : listeners) {
                listener.onFailed();
            }
        }

        /**
         * This interfaced is used to get notified when a download has been finished
         */
        public interface EmojiDownloadListener {
            /**
             * Called after successfully finishing a download.
             * @param font The font related to this download. This will help identifying the download
             */
            void onDownloaded(EmojiCompatFont font);

            // TODO: Add functionality
            /**
             * Called when something went wrong with the download.
             * This one won't be called when the download has been cancelled though.
             */
            default void onFailed() {
                // Oh no! D:
            }

            /**
             * Called whenever the progress changed
             * @param Progress A value between 0 and 1 representing the current progress
             */
            default void onProgress(float Progress) {
                // ARE WE THERE YET?
            }
        }
    }

    @Override
    @NonNull
    public String toString() {
        return display;
    }
}