package net.knarcraft.knarlib.util;

import net.knarcraft.knarlib.config.StargateYamlConfiguration;
import net.knarcraft.knarlib.plugin.ConfigCommentPlugin;
import net.knarcraft.knarlib.property.ColorConversion;
import org.bukkit.configuration.ConfigurationSection;
import org.bukkit.configuration.MemorySection;
import org.bukkit.configuration.file.FileConfiguration;
import org.bukkit.configuration.file.YamlConfiguration;
import org.bukkit.plugin.Plugin;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.util.Map;
import java.util.logging.Level;

/**
 * A helper class for dealing with a plugin's configuration file
 */
@SuppressWarnings("unused")
public final class ConfigHelper {

    private static final String CONFIG_FILE = "config.yml";
    private static final String BACKUP_CONFIG_FILE = "config.yml.old";
    private static final String MIGRATION_FILE = "config-migrations.txt";

    private ConfigHelper() {

    }

    /**
     * Gets the relative string path of the configuration file
     *
     * @return <p>The configuration file path</p>
     */
    public static String getConfigFile() {
        return CONFIG_FILE;
    }

    /**
     * Saves any missing configuration values to the given plugin's configuration
     *
     * @param plugin <p>The plugin to add missing default values to</p>
     */
    public static void saveDefaults(@NotNull Plugin plugin) {
        plugin.saveDefaultConfig();
        plugin.getConfig().options().copyDefaults(true);
        plugin.reloadConfig();
        plugin.saveConfig();
    }

    /**
     * Changes all configuration values from the old name to the new name
     *
     * <p>Note: This method expects a file "config-migrations.txt" in the resources directory that contains mappings:
     * oldKey=replacementKey in order to migrate from old to new configuration values.
     * The old configuration file will be saved to config.yml.old</p>
     *
     * @param plugin <p>The plugin to migrate the configuration for</p>
     * @return <p>True if the migration succeeded without any issues</p>
     */
    public static boolean migrateConfig(@NotNull ConfigCommentPlugin plugin) {
        File dataFolder = plugin.getDataFolder();
        File config = new File(dataFolder, CONFIG_FILE);

        //Save the old config just in case something goes wrong
        FileConfiguration oldConfiguration = plugin.getConfig();
        try {
            oldConfiguration.save(new File(dataFolder, BACKUP_CONFIG_FILE));
        } catch (IOException exception) {
            plugin.getLogger().log(Level.WARNING, "Unable to save old backup and do migration");
            return false;
        }

        // Read the default configuration
        InputStream configStream = loadInternalFile(plugin, CONFIG_FILE, "internal configuration");
        if (configStream == null) {
            return false;
        }
        YamlConfiguration newConfiguration = StargateYamlConfiguration.loadConfiguration(
                FileHelper.getBufferedReaderFromInputStream(configStream));

        //Read all available config migrations
        Map<String, String> migrationFields;
        try {
            InputStream migrationStream = loadInternalFile(plugin, MIGRATION_FILE, "internal migration paths");
            if (migrationStream == null) {
                return false;
            }
            migrationFields = FileHelper.readKeyValuePairs(FileHelper.getBufferedReaderFromInputStream(migrationStream),
                    "=", ColorConversion.NONE);
        } catch (IOException exception) {
            plugin.getLogger().log(Level.WARNING, "Unable to load config migration file");
            return false;
        }

        // Replace old config names with the new ones
        for (String key : migrationFields.keySet()) {
            if (oldConfiguration.contains(key)) {
                migrateProperty(migrationFields, key, oldConfiguration);
            }
        }

        // Copy all keys to the new config
        for (String key : StargateYamlConfiguration.getKeysWithoutComments(oldConfiguration, true)) {
            if (oldConfiguration.get(key) instanceof MemorySection) {
                continue;
            }
            newConfiguration.set(key, oldConfiguration.get(key));
        }

        // Save merged configuration
        if (!StargateYamlConfiguration.saveConfiguration(plugin, newConfiguration)) {
            return false;
        }

        plugin.reloadConfig();
        return true;
    }

    /**
     * Migrates one configuration property
     *
     * @param migrationFields  <p>The configuration fields to be migrated</p>
     * @param key              <p>The key/path of the property to migrate</p>
     * @param oldConfiguration <p>The original pre-migration configuration</p>
     */
    private static void migrateProperty(@NotNull Map<String, String> migrationFields, @NotNull String key,
                                        @NotNull FileConfiguration oldConfiguration) {
        String newPath = migrationFields.get(key);
        Object oldValue = oldConfiguration.get(key);
        if (!newPath.trim().isEmpty()) {
            if (oldConfiguration.isConfigurationSection(key)) {
                // Copy each value of a configuration section
                ConfigurationSection sourceSection = oldConfiguration.getConfigurationSection(key);
                ConfigurationSection destinationSection = oldConfiguration.createSection(newPath);
                if (sourceSection == null) {
                    return;
                }
                for (String path : StargateYamlConfiguration.getKeysWithoutComments(sourceSection, true)) {
                    destinationSection.set(path, sourceSection.get(path));
                }
            } else {
                // Copy the value to the new path
                oldConfiguration.set(newPath, oldValue);
            }
        }

        // Remove the old path's value
        oldConfiguration.set(key, null);
    }

    /**
     * Loads a file from the internal plugin .jar
     *
     * @param plugin          <p>The plugin to load the file from</p>
     * @param fileName        <p>The file to load</p>
     * @param fileDescription <p>The file description to use in error messages</p>
     * @return <p>An input stream for the file, or null if the file could not be read</p>
     */
    @Nullable
    private static InputStream loadInternalFile(@NotNull Plugin plugin, @NotNull String fileName,
                                                @NotNull String fileDescription) {
        InputStream configStream = FileHelper.getInputStreamForInternalFile("/" + fileName);
        if (configStream == null) {
            plugin.getLogger().log(Level.SEVERE, "Could not migrate the configuration, as the " + fileDescription +
                    " could not be read!");
            return null;
        } else {
            return configStream;
        }
    }

}