package com.intellectualcrafters.configuration.file;

import com.intellectualcrafters.configuration.Configuration;
import com.intellectualcrafters.configuration.InvalidConfigurationException;
import com.intellectualcrafters.configuration.MemoryConfiguration;
import org.yaml.snakeyaml.external.biz.base64Coder.Base64Coder;

import java.io.BufferedReader;
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.io.OutputStreamWriter;
import java.io.Reader;
import java.io.Writer;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;

/**
 * This is a base class for all File based implementations of {@link
 * Configuration}
 */
public abstract class FileConfiguration extends MemoryConfiguration {
    /**
     * This value specified that the system default encoding should be
     * completely ignored, as it cannot handle the ASCII character set, or it
     * is a strict-subset of UTF8 already (plain ASCII).
     *
     * @deprecated temporary compatibility measure
     */
    @Deprecated
    public static final boolean UTF8_OVERRIDE;
    /**
     * This value specifies if the system default encoding is unicode, but
     * cannot parse standard ASCII.
     *
     * @deprecated temporary compatibility measure
     */
    @Deprecated
    public static final boolean UTF_BIG;
    /**
     * This value specifies if the system supports unicode.
     *
     * @deprecated temporary compatibility measure
     */
    @Deprecated
    public static final boolean SYSTEM_UTF;
    static {
        final byte[] testBytes = Base64Coder.decode("ICEiIyQlJicoKSorLC0uLzAxMjM0NTY3ODk6Ozw9Pj9AQUJDREVGR0hJSktMTU5PUFFSU1RVVldYWVpbXF1eX2BhYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3h5ent8fX4NCg==");
        final String testString = " !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\r\n";
        final Charset defaultCharset = Charset.defaultCharset();
        final String resultString = new String(testBytes, defaultCharset);
        final boolean trueUTF = defaultCharset.name().contains("UTF");
        UTF8_OVERRIDE = !testString.equals(resultString) || defaultCharset.equals(Charset.forName("US-ASCII"));
        SYSTEM_UTF = trueUTF || UTF8_OVERRIDE;
        UTF_BIG = trueUTF && UTF8_OVERRIDE;
    }
    
    /**
     * Creates an empty {@link FileConfiguration} with no default values.
     */
    public FileConfiguration() {
        super();
    }
    
    /**
     * Creates an empty {@link FileConfiguration} using the specified {@link
     * Configuration} as a source for all default values.
     *
     * @param defaults Default value provider
     */
    public FileConfiguration(final Configuration defaults) {
        super(defaults);
    }
    
    /**
     * Saves this {@link FileConfiguration} to the specified location.
     * <p>
     * If the file does not exist, it will be created. If already exists, it
     * will be overwritten. If it cannot be overwritten or created, an
     * exception will be thrown.
     * <p>
     * This method will save using the system default encoding, or possibly
     * using UTF8.
     *
     * @param file File to save to.
     * @throws IOException Thrown when the given file cannot be written to for
     *     any reason.
     * @throws IllegalArgumentException Thrown when file is null.
     */
    public void save(final File file) throws IOException {
        if (file == null) {
            throw new NullPointerException("File cannot be null");
        }
        file.getParentFile().mkdirs();
        
        final String data = saveToString();

        try (Writer writer = new OutputStreamWriter(new FileOutputStream(file),
                UTF8_OVERRIDE && !UTF_BIG ? StandardCharsets.UTF_8 : Charset.defaultCharset())) {
            writer.write(data);
        }
    }
    
    /**
     * Saves this {@link FileConfiguration} to the specified location.
     * <p>
     * If the file does not exist, it will be created. If already exists, it
     * will be overwritten. If it cannot be overwritten or created, an
     * exception will be thrown.
     * <p>
     * This method will save using the system default encoding, or possibly
     * using UTF8.
     *
     * @param file File to save to.
     * @throws IOException Thrown when the given file cannot be written to for
     *     any reason.
     * @throws IllegalArgumentException Thrown when file is null.
     */
    public void save(final String file) throws IOException {
        if (file == null) {
            throw new NullPointerException("File cannot be null");
        }
        
        save(new File(file));
    }
    
    /**
     * Saves this {@link FileConfiguration} to a string, and returns it.
     *
     * @return String containing this configuration.
     */
    public abstract String saveToString();
    
    /**
     * Loads this {@link FileConfiguration} from the specified location.
     * <p>
     * All the values contained within this configuration will be removed,
     * leaving only settings and defaults, and the new values will be loaded
     * from the given file.
     * <p>
     * If the file cannot be loaded for any reason, an exception will be
     * thrown.
     * <p>
     * This will attempt to use the {@link Charset#defaultCharset()} for
     * files, unless {@link #UTF8_OVERRIDE} but not {@link #UTF_BIG} is
     * specified.
     *
     * @param file File to load from.
     * @throws FileNotFoundException Thrown when the given file cannot be
     *     opened.
     * @throws IOException Thrown when the given file cannot be read.
     * @throws InvalidConfigurationException Thrown when the given file is not
     *     a valid Configuration.
     * @throws IllegalArgumentException Thrown when file is null.
     */
    public void load(final File file) throws IOException, InvalidConfigurationException {
        if (file == null) {
            throw new NullPointerException("File cannot be null");
        }
        
        final FileInputStream stream = new FileInputStream(file);
        
        load(new InputStreamReader(stream, UTF8_OVERRIDE && !UTF_BIG ? StandardCharsets.UTF_8 : Charset.defaultCharset()));
    }
    
    /**
     * Loads this {@link FileConfiguration} from the specified stream.
     * <p>
     * All the values contained within this configuration will be removed,
     * leaving only settings and defaults, and the new values will be loaded
     * from the given stream.
     * <p>
     * This will attempt to use the {@link Charset#defaultCharset()}, unless
     * {@link #UTF8_OVERRIDE} or {@link #UTF_BIG} is specified.
     *
     * @param stream Stream to load from
     * @throws IOException Thrown when the given file cannot be read.
     * @throws InvalidConfigurationException Thrown when the given file is not
     *     a valid Configuration.
     * @throws IllegalArgumentException Thrown when stream is null.
     * @deprecated This does not consider encoding
     * @see #load(Reader)
     */
    @Deprecated
    public void load(final InputStream stream) throws IOException, InvalidConfigurationException {
        if (stream == null) {
            throw new NullPointerException("Stream cannot be null");
        }
        
        load(new InputStreamReader(stream, UTF8_OVERRIDE ? StandardCharsets.UTF_8 : Charset.defaultCharset()));
    }
    
    /**
     * Loads this {@link FileConfiguration} from the specified reader.
     * <p>
     * All the values contained within this configuration will be removed,
     * leaving only settings and defaults, and the new values will be loaded
     * from the given stream.
     *
     * @param reader the reader to load from
     * @throws IOException thrown when underlying reader throws an IOException
     * @throws InvalidConfigurationException thrown when the reader does not
     *      represent a valid Configuration
     * @throws IllegalArgumentException thrown when reader is null
     */
    public void load(final Reader reader) throws IOException, InvalidConfigurationException {

        final StringBuilder builder = new StringBuilder();

        try (BufferedReader input = reader instanceof BufferedReader ? (BufferedReader) reader : new BufferedReader(reader)) {
            String line;

            while ((line = input.readLine()) != null) {
                builder.append(line);
                builder.append('\n');
            }
        }
        
        loadFromString(builder.toString());
    }
    
    /**
     * Loads this {@link FileConfiguration} from the specified location.
     * <p>
     * All the values contained within this configuration will be removed,
     * leaving only settings and defaults, and the new values will be loaded
     * from the given file.
     * <p>
     * If the file cannot be loaded for any reason, an exception will be
     * thrown.
     *
     * @param file File to load from.
     * @throws FileNotFoundException Thrown when the given file cannot be
     *     opened.
     * @throws IOException Thrown when the given file cannot be read.
     * @throws InvalidConfigurationException Thrown when the given file is not
     *     a valid Configuration.
     * @throws IllegalArgumentException Thrown when file is null.
     */
    public void load(final String file) throws IOException, InvalidConfigurationException {
        if (file == null) {
            throw new NullPointerException("File cannot be null");
        }
        
        load(new File(file));
    }
    
    /**
     * Loads this {@link FileConfiguration} from the specified string, as
     * opposed to from file.
     * <p>
     * All the values contained within this configuration will be removed,
     * leaving only settings and defaults, and the new values will be loaded
     * from the given string.
     * <p>
     * If the string is invalid in any way, an exception will be thrown.
     *
     * @param contents Contents of a Configuration to load.
     * @throws InvalidConfigurationException Thrown if the specified string is
     *     invalid.
     * @throws IllegalArgumentException Thrown if contents is null.
     */
    public abstract void loadFromString(final String contents) throws InvalidConfigurationException;
    
    /**
     * Compiles the header for this {@link FileConfiguration} and returns the
     * result.
     * <p>
     * This will use the header from {@link #options()} -> {@link
     * FileConfigurationOptions#header()}, respecting the rules of {@link
     * FileConfigurationOptions#copyHeader()} if set.
     *
     * @return Compiled header
     */
    protected abstract String buildHeader();
    
    @Override
    public FileConfigurationOptions options() {
        if (options == null) {
            options = new FileConfigurationOptions(this);
        }
        
        return (FileConfigurationOptions) options;
    }
}