/*
* Copyright (C) 2019 Max 'Libra' Kersten [@LibraAnalysis]
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package dao;
import dao.generic.IClassJsonParser;
import exception.JsonFolderNotFoundException;
import exception.JsonParseException;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import model.language.enums.Language;
import model.snippet.Snippet;
import model.snippet.SnippetConstants;
import org.json.*;
import service.LanguageService;
/**
* This class loads the snippets from the disk into snippet objects. This class
* is to be used with the <code>SnippetManager</code>, which is a class with
* static functions and variables. Therefore, the list of snippets resides in
* memory and is only resident once within the memory of Genesis. This allows
* the loading to be done once and only to be done again when an additional
* snippet is placed within the snippet folder. Regardless of the amount of
* requests to the list of snippets, only the one within the memory is accessed,
* resulting in a fast response from Genesis.
*
* @author Max 'Libra' Kersten [@LibraAnalysis]
*/
public class SnippetLoader {
/**
* The description of the snippets that are loaded (in JSON format) are
* stored in this list. This way, duplicates are not loaded twice
*/
private List<String> loadedSnippets;
/**
* Create an SnippetLoader object, which can load all snippets that are
* within the <code>SnippetConstants.SNIPPET_FOLDER</code> folder on the
* disk.
*/
public SnippetLoader() {
loadedSnippets = new ArrayList<>();
}
/**
* Loads a single snippet based on the ID. The file name is equal to the ID
* of the snippet plus ".json".
*
* @param snippetId the id of the snippet to load
* @return the loaded snippet
* @throws JsonParseException if the json file cannot be parsed correctly
* @throws JsonFolderNotFoundException if the json file cannot be found
*/
protected Snippet loadSnippet(String snippetId) throws JsonParseException, JsonFolderNotFoundException {
//The folder in which all the JSON files reside (in the root of the file system)
File jsonFolder = new File(SnippetConstants.SNIPPET_FOLDER);
//Checks if the folder exists or if the folder is a file
if (!jsonFolder.exists()) {
throw new JsonFolderNotFoundException("Unable to load the JSON folder because it does not exist!");
}
if (jsonFolder.isFile()) {
throw new JsonFolderNotFoundException("Unable to load the JSON folder because it is a file!");
}
//Listing all files in the folder
File[] jsonFiles = jsonFolder.listFiles();
for (File jsonFile : jsonFiles) {
try {
//Ignores the ".git" directory and all files that are within it
if (jsonFile.getAbsolutePath().contains(".git") || !jsonFile.getName().equalsIgnoreCase(snippetId + ".json")) {
continue;
}
//Load the file from the disk
JSONObject jsonObject = loadFileFromDisk(jsonFile);
//Return the parsed value
return parseSnippet(jsonObject);
} catch (IOException ex) {
throw new JsonParseException("Unable to load " + jsonFile.getAbsolutePath() + "!");
}
}
throw new JsonParseException("Unable to find a Snippet file for the given Snippet ID (" + snippetId + ")!");
}
/**
* Loads all snippets that reside within
* <code>SnippetConstants.SNIPPET_FOLDER</code> folder in the file system.
* All files are parsed with the corresponding parser and returned within a
* list.
*
* @return a list of all loaded snippets
* @throws JsonFolderNotFoundException is thrown if the
* <code>SnippetConstants.SNIPPET_FOLDER</code> folder cannot be found or if
* the folder is actually a file
* @throws JsonParseException is thrown if a JSON file cannot be parsed with
* one of the existing parsers
*/
protected List<Snippet> loadSnippets() throws JsonFolderNotFoundException, JsonParseException {
//To avoid duplicates, the variables are instantiated
List<Snippet> snippets = new ArrayList<>();
loadedSnippets = new ArrayList<>();
//The folder in which all the JSON files reside (in the root of the file system)
File jsonFolder = new File(SnippetConstants.SNIPPET_FOLDER);
//Checks if the folder exists or if the folder is a file
if (!jsonFolder.exists()) {
throw new JsonFolderNotFoundException("Unable to load the JSON folder because it does not exist!");
}
if (jsonFolder.isFile()) {
throw new JsonFolderNotFoundException("Unable to load the JSON folder because it is a file!");
}
//Listing all files in the folder
File[] jsonFiles = jsonFolder.listFiles();
for (File jsonFile : jsonFiles) {
//Ignores the ".git" directory and all files that are within it
if (jsonFile.getAbsolutePath().contains(".git")) {
continue;
}
try {
//Load the file from the disk
JSONObject jsonObject = loadFileFromDisk(jsonFile);
Snippet snippet = parseSnippet(jsonObject);
//The loaded snippets are checked: if the newly loaded snippet already exists within the list, then it is skipped
if (!loadedSnippets.contains(snippet.toString())) {
//Since the snippet is not loaded yet, it should be added to avoid duplicates of this snippet in the future
loadedSnippets.add(snippet.toString());
//The final list of all snippets should also contain this snippet
snippets.add(snippet);
}
} catch (IOException ex) {
throw new JsonParseException("Unable to load " + jsonFile.getAbsolutePath());
}
}
return snippets;
}
/**
* Parses a JSONObject into a <code>Snippet</code>.
*
* @param jsonObject the Snippet object to parse
* @return the parsed result in a <code>Snippet</code> object
* @throws JsonParseException is thrown if the JSONObject could not be
* parsed
*/
protected Snippet parseSnippet(JSONObject jsonObject) throws JsonParseException {
//Gets the language field from the class, which is stored as a value from the Language enumeration
Language language = Language.valueOf(jsonObject.getJSONObject("class").getString("language"));
//Instantiates the language service to obtain a language specific instance of a class later on
LanguageService languageService = new LanguageService();
//Gets the language specific parser that matches with this language
IClassJsonParser iClassJsonParser = languageService.getJsonParser(language);
//Returns the parsed result in the form of a Snippet object
return iClassJsonParser.parse(jsonObject);
}
/**
* Loads a file from the disk and creates a JSON object from it.
*
* @param file The file to be read
* @return the content of the file in the form of a JSON object
* @throws FileNotFoundException is thrown if the file cannot be found
* @throws IOException is thrown if something goes wrong when accessing the
* file
*/
private JSONObject loadFileFromDisk(File file) throws FileNotFoundException, IOException {
//Try to open the file using a file reader in a buffered reader to minimise the amount of system calls (and thus load on the system)
try (BufferedReader br = new BufferedReader(new FileReader(file))) {
//Creates a new string builder object
StringBuilder sb = new StringBuilder();
//Reads a line from the buffered reader
String line = br.readLine();
//As long as the line is not null, it means that there is line
while (line != null) {
//The current line is appended
sb.append(line);
//A line separator is added based on the operating system
sb.append(System.lineSeparator());
//The next line is read
line = br.readLine();
}
//Return the string in the form of a JSON object
return new JSONObject(sb.toString());
}
}
}
