package ru.ifmo.rain.brichev.implementor;

import info.kgeorgiy.java.advanced.implementor.JarImpler;
import info.kgeorgiy.java.advanced.implementor.ImplerException;


import javax.tools.JavaCompiler;
import javax.tools.ToolProvider;
import java.io.*;
import java.lang.reflect.*;
import java.net.URISyntaxException;
import java.nio.file.Files;
import java.nio.file.InvalidPathException;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.security.CodeSource;
import java.util.*;
import java.util.function.Function;
import java.util.jar.Attributes;
import java.util.jar.JarOutputStream;
import java.util.jar.Manifest;
import java.util.stream.Collectors;
import java.util.zip.ZipEntry;

/**
 * Implementation class for {@link JarImpler} interface.
 */

public class JarImplementor implements JarImpler {
    /**
     * Line separator specified to current OS
     */

    private static final Character PATH_SEPARATOR = File.separatorChar;

    /**
     * End line separator specified to current OS
     */
    private static final String END_LINE = System.lineSeparator();

    /**
     * Template of exception message, that is thrown during writing
     */

    private static final String WRITING_FILE_ERROR = "Writing file error: ";

    /**
     * Whitespace separator.
     */

    private static final String TAB = "    ";

    /**
     * Default constructor.
     */

    public JarImplementor() {
    }

    /**
     * Main method.
     * First argument should be "-class" or "-jar".
     * Second argument must be classname and in case of "-jar" option should be name of jar file to generate
     *
     * @param args - arguments
     */

    public static void main(String[] args) {
        if (args == null || (args.length != 2 && args.length != 3)) {
            System.out.println("Wrong arguments format");
            return;
        }

        for (String arg : args) {
            if (arg == null) {
                System.out.println("Null argument appeared");
                return;
            }
        }

        try {
            if (args.length == 2) {
                new ru.ifmo.rain.brichev.implementor.JarImplementor().implement(Class.forName(args[0]), Paths.get(args[1]));
            } else if ("-jar".equals(args[0])) {
                new ru.ifmo.rain.brichev.implementor.JarImplementor().implementJar(Class.forName(args[1]), Paths.get(args[2]));
            } else {
                System.out.println("Wrong arguments format");
            }
        } catch (ClassNotFoundException e) {
            System.out.println("Class not found");
        } catch (InvalidPathException e) {
            System.out.println("Invalid path");
        } catch (ImplerException e) {
            System.err.println(e.getMessage());
        }
    }


    /**
     * Creates an arguments for compiler
     *
     * @param token  class
     * @param tmpDir temporary directory
     * @param cp     path of class
     * @return compile args
     */
    private String[] getArgs(Class<?> token, Path tmpDir, String cp) {
        String[] args = new String[]{
                "-cp",
                System.getProperty("java.class.path") + File.pathSeparator
                        + tmpDir + File.pathSeparator +
                        cp,
                tmpDir.resolve(getFilePath(token, tmpDir, ".java")).toString()};
        return args;
    }

    /**
     * Method that clean a temporary directory
     *
     * @param tmpDir temporary directory
     * @throws ImplerException if an error occurs
     */

    private void cleanDirectory(Path tmpDir) throws ImplerException {
        try {
            Files.walk(tmpDir)
                    .map(Path::toFile)
                    .sorted(Comparator.reverseOrder())
                    .forEach(File::delete);
        } catch (IOException e) {
            throw new ImplerException("Failed deleting temporary files in " + tmpDir.toString());
        }
    }

    /**
     * Convert to unicode string
     *
     * @param in input string
     * @return converted string
     */
    private String toUnicode(String in) {
        StringBuilder b = new StringBuilder();

        for (char c : in.toCharArray()) {
            if (c >= 128)
                b.append("\\u").append(String.format("%04X", (int) c));
            else
                b.append(c);
        }

        return b.toString();
    }


    /**
     * @param token given token
     * @return path to implementation of class
     */

    private static String getPathToImplementation(Class<?> token) {
        return Paths.get("").resolve(token.getPackageName().replace('.', '/')).resolve(token.getSimpleName()).toString().replace('\\', '/');
    }

    /**
     * @param token given token
     * @return super class path
     * @throws ImplerException if an error occurs
     */
    private static Path getSuperPath(Class<?> token) throws ImplerException {
        try {
            CodeSource codeSource = token.getProtectionDomain().getCodeSource();
            if (codeSource == null) {
                return Path.of(".");
            } else {
                return Path.of(codeSource.getLocation().toURI());
            }
        } catch (InvalidPathException | URISyntaxException e) {
            throw new ImplerException("Classpath generation failed", e);
        }
    }


    /**
     * @param token     given token
     * @param sourceDir source directory
     * @throws ImplerException if an error occurs
     */
    private static void compile(Class<?> token, Path sourceDir) throws ImplerException {

        Path toSuper = getSuperPath(token);

        JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
        if (compiler == null) {
            throw new ImplerException("Compiler is not installed");
        }

        String[] compilationArgs = {"-encoding", "UTF-8",
                "-cp",
                sourceDir.toString() + File.pathSeparator + toSuper.toString(),
                Path.of(sourceDir.toString(), getPathToImplementation(token) + "Impl.java").toString()
        };

        int compilationResultCode = compiler.run(null, null, null, compilationArgs);
        if (compilationResultCode != 0) {
            throw new ImplerException("Compilation failed (result code is not 0): " + compilationResultCode);
        }

    }

    /**
     * {@inheritDoc}
     */

    @Override
    public void implementJar(Class<?> token, Path jarFile) throws ImplerException {
        if (token == null || jarFile == null) {
            throw new ImplerException("Invalid argument: null");
        }

        createDirectories(jarFile);

        Path tmpDir;
        try {
            tmpDir = Files.createTempDirectory(jarFile.toAbsolutePath().getParent(), "tmp");
        } catch (IOException e) {
            throw new ImplerException("Error during creating temporary directory", e);
        }

        try {
            implement(token, tmpDir);
            compile(token, tmpDir);

            Manifest manifest = new Manifest();
            Attributes attributes = manifest.getMainAttributes();
            attributes.put(Attributes.Name.MANIFEST_VERSION, "1.0");
            attributes.put(Attributes.Name.IMPLEMENTATION_VENDOR, "Anton Brichev");

            try (JarOutputStream stream = new JarOutputStream(Files.newOutputStream(jarFile), manifest)) {
                String implementationPath = getPathToImplementation(token) + "Impl.class";
                stream.putNextEntry(new ZipEntry(implementationPath));
                Files.copy(Path.of(tmpDir.toString(), implementationPath), stream);

            } catch (IOException e) {
                throw new ImplerException("Writing a jar file error ", e);
            }
        } finally {
            cleanDirectory(tmpDir);
        }
    }

    /**
     * Converts the given token into the path of source file
     * potentially implemented and resolved against the given path
     * and add the given file extension
     *
     * @param token  given token
     * @param root   path to be resolve against
     * @param suffix file extension
     * @return the resulting path
     */

    private Path getFilePath(Class<?> token, Path root, String suffix) {
        return root.resolve(token.getPackageName().replace('.', PATH_SEPARATOR))
                .resolve(token.getSimpleName() + "Impl" + suffix);
    }


    /**
     * Creates directories using given path
     *
     * @param path given path
     * @throws ImplerException if an error occurs
     */

    private void createDirectories(Path path) throws ImplerException {
        if (path.getParent() != null) {
            try {
                Files.createDirectories(path.getParent());
            } catch (IOException e) {
                throw new ImplerException("Can't create directories in: " + path);
            }
        }
    }


    /**
     * Class that pack {@link Method} and provides {@link ru.ifmo.rain.brichev.implementor.JarImplementor.MethodSetter#equals(Object)} and
     * {@link ru.ifmo.rain.brichev.implementor.JarImplementor.MethodSetter#hashCode()} depending on packed method
     */

    private static class MethodSetter {

        /**
         * packed method
         */

        final private Method method;


        /**
         * Constructor receiving method for packing
         *
         * @param method method to be packed
         */

        private MethodSetter(Method method) {
            this.method = method;
        }

        /**
         * Getter for packed method
         *
         * @return packed method
         */

        private Method getMethod() {
            return method;
        }

        /**
         * {@inheritDoc}
         */

        @Override
        public boolean equals(Object obj) {
            if (obj == null) {
                return false;
            }
            if (obj instanceof ru.ifmo.rain.brichev.implementor.JarImplementor.MethodSetter) {
                ru.ifmo.rain.brichev.implementor.JarImplementor.MethodSetter other = (ru.ifmo.rain.brichev.implementor.JarImplementor.MethodSetter) obj;
                return Arrays.equals(method.getParameterTypes(), other.method.getParameterTypes())
                        && method.getName().equals(other.method.getName())
                        && method.getReturnType().equals(other.method.getReturnType());
            }
            return false;
        }

        /**
         * {@inheritDoc}
         */

        @Override
        public int hashCode() {
            return 31 * 31 * Arrays.hashCode(method.getParameterTypes())
                    + 31 * method.getName().hashCode()
                    + method.getReturnType().hashCode();
        }

    }


    /**
     * {@inheritDoc}
     */

    @Override
    public void implement(Class<?> token, Path root) throws ImplerException {
        if (token == null || root == null) {
            throw new ImplerException("Not-null arguments expected");
        }
        if (token.equals(Enum.class) || token.isPrimitive() || token.isArray() || token.isEnum() || Modifier.isFinal(token.getModifiers()) || Modifier.isPrivate(token.getModifiers())) {
            throw new ImplerException("bad token");
        }
        Path filepath = getFilePath(token, root, ".java");
        createDirectories(filepath);
        try (Writer writer = Files.newBufferedWriter(filepath)) {
            addPackage(writer, token);
            addClassName(writer, token);
            if (!token.isInterface())
                addConstructors(writer, token);
            addMethods(writer, token);
            writer.write(toUnicode("}"));
        } catch (IOException e) {
            throw new ImplerException(WRITING_FILE_ERROR + e.getMessage());
        }
    }


    /**
     * Adds constructors of token into file associated with writer
     *
     * @param writer writer associated with implemented class file
     * @param token  implemented class token
     * @throws ImplerException if given token has no non-private constructors
     *                         or any error occurs during writing into file
     */


    private void addConstructors(Writer writer, Class<?> token) throws ImplerException {
        Constructor<?>[] constructors = token.getDeclaredConstructors();
        List<Constructor<?>> constructors_ = Arrays.stream(constructors)
                .filter(x -> !Modifier.isPrivate(x.getModifiers())).collect(Collectors.toList());
        if (constructors_.isEmpty()) {
            throw new ImplerException("No constructors");
        }
        for (Constructor<?> constructor : constructors_) {
            try {
                writer.write(toUnicode(getExecutable(constructor)));
            } catch (IOException e) {
                throw new ImplerException(WRITING_FILE_ERROR + e.getMessage());
            }
        }
    }

    /**
     * Add methods by applying func on given token, then
     * Packs them by {@link ru.ifmo.rain.brichev.implementor.JarImplementor.MethodSetter} and inserts into the given {@link Set}
     *
     * @param methods set for insertions
     * @param token   class token
     * @param func    Function receiving token and returning array of methods
     */


    private void addMethodsToSet(Set<ru.ifmo.rain.brichev.implementor.JarImplementor.MethodSetter> methods, Class<?> token,
                                 Function<Class<?>, Method[]> func) {
        Arrays.stream(func.apply(token))
                .filter(x -> Modifier.isAbstract(x.getModifiers()))
                .map(ru.ifmo.rain.brichev.implementor.JarImplementor.MethodSetter::new)
                .collect(Collectors.toCollection(() -> methods));
    }


    /**
     * Extracts all {@link Modifier#ABSTRACT} methods of given token
     *
     * @param token class token
     * @return set of abstract methods
     */

    private Set<Method> getAllAbstractMethods(Class<?> token) {
        Set<ru.ifmo.rain.brichev.implementor.JarImplementor.MethodSetter> methods = new HashSet<>();
        addMethodsToSet(methods, token, Class::getMethods);
        while (token != null) {
            addMethodsToSet(methods, token, Class::getDeclaredMethods);
            token = token.getSuperclass();
        }
        return methods.stream().map(ru.ifmo.rain.brichev.implementor.JarImplementor.MethodSetter::getMethod).collect(Collectors.toCollection(HashSet::new));
    }

    /**
     * Writes all methods of class implemented token's class into file associated with writer
     *
     * @param wr    writer associated with implementing class file
     * @param token implementing class token
     * @throws ImplerException if any errors occurs during writing
     */

    private void addMethods(Writer wr, Class<?> token) throws ImplerException {
        Set<Method> methods = getAllAbstractMethods(token);
        for (Method m : methods) {
            try {
                wr.write(toUnicode(getExecutable(m)));
            } catch (IOException e) {
                throw new ImplerException(WRITING_FILE_ERROR + e.getMessage());
            }
        }
    }


    /**
     * Multiplies {@link ru.ifmo.rain.brichev.implementor.JarImplementor#TAB}
     *
     * @param count number of repetition
     * @return {@link ru.ifmo.rain.brichev.implementor.JarImplementor#TAB} repeated count times
     */


    private String getTabs(int count) {
        return TAB.repeat(count);
    }

    /**
     * Converts the given array of tokens into string.
     * Every token is separated by ", "
     *
     * @param exceptions given array of tokens
     * @return string representation of given token's array
     */


    private String getExceptions(Class<?>[] exceptions) {
        StringBuilder stringBuilder = new StringBuilder();
        for (Class<?> exception : exceptions) {
            stringBuilder.append(exception.getCanonicalName()).append(", ");
        }
        return stringBuilder.substring(0, stringBuilder.length() - 2);
    }

    /**
     * Converts the given executable into default string representation.
     * It includes return type for functions or methods, name, checked exceptions
     * throwing by it, its arguments and body
     *
     * @param exec given executable
     * @return default string representation of given executable
     */


    private String getExecutable(Executable exec) {
        return getTabs(1) + Modifier.toString(exec.getModifiers() & (Modifier.PUBLIC | Modifier.PROTECTED))
                + " " + getReturnTypeAndName(exec)
                + "(" + getArguments(exec) + ")"
                + (exec.getExceptionTypes().length == 0
                ? ""
                : " throws " + getExceptions(exec.getExceptionTypes()) + " ") + "{" + END_LINE
                + getBody(exec) + END_LINE
                + getTabs(1) + "}" + END_LINE + END_LINE;
    }


    /**
     * Converts the given executable into string containing its default body.
     * The body will contains only return statement with default value
     * concerted with return type of given executable for functions and methods.
     * For constructors it also will contains the call of super method with correct arguments
     * related with given executable arguments
     *
     * @param exec given executable
     * @return default body of given executable
     */

    private String getBody(Executable exec) {
        return (exec instanceof Constructor ?
                getTabs(2) + "super(" + getArguments(exec, false) + ");" + END_LINE : "") +
                getTabs(2) + "return " + getReturn(exec) + ";";
    }


    /**
     * Converts the given executable into string containing all its arguments accompanied by their
     * types and separated by ", ".
     * Equivalently to call {@link ru.ifmo.rain.brichev.implementor.JarImplementor#getArguments(Executable, boolean)} with true flag
     *
     * @param exec given executable
     * @return arguments of executable separated by ", "
     */

    private String getArguments(Executable exec) {
        return getArguments(exec, true);
    }


    /**
     * Converts the given executable into string containing all its arguments separated by ", ".
     * If flag is true they will be accompanied by their types
     *
     * @param exec     given executable
     * @param withType identifier of should type be written before the variables names
     * @return arguments of executable separated by ", "
     */

    private String getArguments(Executable exec, boolean withType) {
        StringBuilder sb = new StringBuilder();
        Parameter[] parameters = exec.getParameters();
        for (Parameter parameter : parameters) {
            sb.
                    append(withType ? parameter.getType().getCanonicalName() : "")
                    .append(" ").append(parameter.getName()).append(", ");
        }
        return sb.length() > 0 ? sb.substring(0, sb.length() - 2) : sb.toString();
    }

    /**
     * Converts the given executable into string containing return type and name
     *
     * @param exec given executable
     * @return string containing return type and name of the given executable
     */

    private String getReturnTypeAndName(Executable exec) {
        if (exec instanceof Method) {
            Method m = (Method) exec;
            return m.getReturnType().getCanonicalName() + " " + m.getName();
        } else {
            return exec.getDeclaringClass().getSimpleName() + "Impl";
        }
    }

    /**
     * Converts the given executable into string containing return with default value
     *
     * @param exec given executable
     * @return "return" + default value for given executable("" for void functions and constructors) + ";"
     */

    private String getReturn(Executable exec) {
        if (exec instanceof Method) {
            Method m = (Method) exec;
            if (m.getReturnType() == void.class) {
                return "";
            } else if (m.getReturnType().isPrimitive()) {
                return m.getReturnType() == boolean.class ? "false" : "0";
            }
            return "null";
        }
        return "";
    }

    /**
     * Writes definition of class implementing token's class into file associated with writer
     *
     * @param wr    writer associated with implementing class file
     * @param token implementing class token
     * @throws ImplerException if any errors occurs during writing
     */

    private void addPackage(Writer wr, Class<?> token) throws ImplerException {
        try {
            if (token.getPackageName() != null) {
                wr.write(toUnicode("package " + token.getPackageName() + ";" + END_LINE + END_LINE));
            } else {
                wr.write(toUnicode(" " + END_LINE + END_LINE));
            }
        } catch (IOException e) {
            throw new ImplerException(WRITING_FILE_ERROR + e.getMessage());
        }
    }


    /**
     * @param wr    writer
     * @param token given token
     * @throws ImplerException if an error occurs
     */

    private void addClassName(Writer wr, Class<?> token) throws ImplerException {
        try {
            wr.write(toUnicode("public class " + token.getSimpleName() + "Impl "
                    + (token.isInterface() ? "implements " : "extends ")
                    + token.getCanonicalName()
                    + " {" + END_LINE));
        } catch (IOException e) {
            throw new ImplerException(WRITING_FILE_ERROR + e.getMessage());
        }
    }
}