/*
 * Copyright (c) 2013 Cisco Systems, Inc. and others.  All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
 * and is available at http://www.eclipse.org/legal/epl-v10.html
 */
package org.opendaylight.yangtools.yang2sources.plugin;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkState;
import static java.util.Objects.requireNonNull;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Throwables;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableSet;
import com.google.common.io.CharStreams;
import java.io.File;
import java.io.IOException;
import java.io.Reader;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.AbstractMap.SimpleImmutableEntry;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Comparator;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Optional;
import java.util.ServiceLoader;
import java.util.Set;
import java.util.stream.Collectors;
import org.apache.maven.plugin.MojoExecutionException;
import org.apache.maven.plugin.MojoFailureException;
import org.apache.maven.project.MavenProject;
import org.opendaylight.yangtools.yang.common.YangConstants;
import org.opendaylight.yangtools.yang.model.parser.api.YangParser;
import org.opendaylight.yangtools.yang.model.parser.api.YangParserException;
import org.opendaylight.yangtools.yang.model.parser.api.YangParserFactory;
import org.opendaylight.yangtools.yang.model.repo.api.StatementParserMode;
import org.opendaylight.yangtools.yang.model.repo.api.YangTextSchemaSource;
import org.opendaylight.yangtools.yang.parser.rfc7950.repo.ASTSchemaSource;
import org.opendaylight.yangtools.yang.parser.rfc7950.repo.TextToASTTransformer;
import org.opendaylight.yangtools.yang2sources.plugin.ConfigArg.CodeGeneratorArg;
import org.opendaylight.yangtools.yang2sources.spi.BasicCodeGenerator;
import org.opendaylight.yangtools.yang2sources.spi.BasicCodeGenerator.ImportResolutionMode;
import org.opendaylight.yangtools.yang2sources.spi.BuildContextAware;
import org.opendaylight.yangtools.yang2sources.spi.MavenProjectAware;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.sonatype.plexus.build.incremental.BuildContext;
import org.sonatype.plexus.build.incremental.DefaultBuildContext;

class YangToSourcesProcessor {
    private static final Logger LOG = LoggerFactory.getLogger(YangToSourcesProcessor.class);
    private static final YangParserFactory DEFAULT_PARSER_FACTORY;

    static {
        final Iterator<YangParserFactory> it = ServiceLoader.load(YangParserFactory.class).iterator();
        checkState(it.hasNext(), "Failed to find a YangParserFactory implementation");
        DEFAULT_PARSER_FACTORY = it.next();
    }

    static final String LOG_PREFIX = "yang-to-sources:";
    private static final String META_INF_STR = "META-INF";
    private static final String YANG_STR = "yang";

    static final String META_INF_YANG_STRING = META_INF_STR + File.separator + YANG_STR;
    static final String META_INF_YANG_STRING_JAR = META_INF_STR + "/" + YANG_STR;
    static final String META_INF_YANG_SERVICES_STRING_JAR = META_INF_STR + "/" + "services";

    private final YangParserFactory parserFactory;
    private final File yangFilesRootDir;
    private final Set<File> excludedFiles;
    private final List<CodeGeneratorArg> codeGeneratorArgs;
    private final MavenProject project;
    private final boolean inspectDependencies;
    private final BuildContext buildContext;
    private final YangProvider yangProvider;

    private YangToSourcesProcessor(final BuildContext buildContext, final File yangFilesRootDir,
            final Collection<File> excludedFiles, final List<CodeGeneratorArg> codeGenerators,
            final MavenProject project, final boolean inspectDependencies, final YangProvider yangProvider) {
        this.buildContext = requireNonNull(buildContext, "buildContext");
        this.yangFilesRootDir = requireNonNull(yangFilesRootDir, "yangFilesRootDir");
        this.excludedFiles = ImmutableSet.copyOf(excludedFiles);
        this.codeGeneratorArgs = ImmutableList.copyOf(codeGenerators);
        this.project = requireNonNull(project);
        this.inspectDependencies = inspectDependencies;
        this.yangProvider = requireNonNull(yangProvider);
        this.parserFactory = DEFAULT_PARSER_FACTORY;
    }

    @VisibleForTesting
    YangToSourcesProcessor(final File yangFilesRootDir, final Collection<File> excludedFiles,
            final List<CodeGeneratorArg> codeGenerators, final MavenProject project, final boolean inspectDependencies,
            final YangProvider yangProvider) {
        this(new DefaultBuildContext(), yangFilesRootDir, excludedFiles, codeGenerators, project,
                inspectDependencies, yangProvider);
    }

    YangToSourcesProcessor(final BuildContext buildContext, final File yangFilesRootDir,
                final Collection<File> excludedFiles, final List<CodeGeneratorArg> codeGenerators,
                final MavenProject project, final boolean inspectDependencies) {
        this(yangFilesRootDir, excludedFiles, codeGenerators, project, inspectDependencies, YangProvider.getInstance());
    }

    public void execute() throws MojoExecutionException, MojoFailureException {
        conditionalExecute(false);
    }

    void conditionalExecute(final boolean skip) throws MojoExecutionException, MojoFailureException {
        /*
         * Collect all files which affect YANG context. This includes all
         * files in current project and optionally any jars/files in the
         * dependencies.
         */
        final List<File> yangFilesInProject;
        try {
            yangFilesInProject = listFiles(yangFilesRootDir, excludedFiles);
        } catch (IOException e) {
            throw new MojoFailureException("Failed to list project files", e);
        }

        if (yangFilesInProject.isEmpty()) {
            // No files to process, skip.
            LOG.info("{} No input files found", LOG_PREFIX);
            return;
        }

        // We need to instantiate all code generators to determine required import resolution mode
        final List<Entry<CodeGeneratorArg, BasicCodeGenerator>> codeGenerators = instantiateGenerators();
        final StatementParserMode importMode = determineRequiredImportMode(codeGenerators);
        final Optional<ProcessorModuleReactor> optReactor = createReactor(importMode, yangFilesInProject);
        if (!optReactor.isPresent()) {
            return;
        }

        final ProcessorModuleReactor reactor = optReactor.get();
        if (!skip) {
            final ContextHolder holder;

            try {
                holder = createContextHolder(reactor);
            } catch (YangParserException e) {
                throw new MojoFailureException("Failed to process reactor " + reactor, e);
            } catch (IOException e) {
                throw new MojoExecutionException("Failed to read reactor " + reactor, e);
            }

            generateSources(holder, codeGenerators);
        } else {
            LOG.info("Skipping YANG code generation because property yang.skip is true");
        }

        // add META_INF/yang
        final Collection<YangTextSchemaSource> models = reactor.getModelsInProject();
        try {
            yangProvider.addYangsToMetaInf(project, models);
        } catch (IOException e) {
            throw new MojoExecutionException("Failed write model files for " + models, e);
        }

        // add META_INF/services
        File generatedServicesDir = new GeneratedDirectories(project).getYangServicesDir();
        YangProvider.setResource(generatedServicesDir, project);
        LOG.debug("{} Yang services files from: {} marked as resources: {}", LOG_PREFIX, generatedServicesDir,
            META_INF_YANG_SERVICES_STRING_JAR);
    }

    private static StatementParserMode determineRequiredImportMode(
            final Collection<Entry<CodeGeneratorArg, BasicCodeGenerator>> codeGenerators) throws MojoFailureException {
        ImportResolutionMode requestedMode = null;
        BasicCodeGenerator requestingGenerator = null;

        for (Entry<CodeGeneratorArg, BasicCodeGenerator> entry : codeGenerators) {
            final BasicCodeGenerator generator = entry.getValue();
            final ImportResolutionMode mode = generator.getImportResolutionMode();
            if (mode == null) {
                // the generator does not care about the mode
                continue;
            }

            if (requestedMode == null) {
                // No mode yet, we have just determined it
                requestedMode = mode;
                requestingGenerator = generator;
                continue;
            }

            if (mode != requestedMode) {
                throw new MojoFailureException(String.format(
                    "Import resolution mode conflict between %s (%s) and %s (%s)", requestingGenerator, requestedMode,
                    generator, mode));
            }
        }

        if (requestedMode == null) {
            return StatementParserMode.DEFAULT_MODE;
        }
        switch (requestedMode) {
            case REVISION_EXACT_OR_LATEST:
                return StatementParserMode.DEFAULT_MODE;
            case SEMVER_LATEST:
                return StatementParserMode.SEMVER_MODE;
            default:
                throw new IllegalStateException("Unhandled import resolution mode " + requestedMode);
        }
    }

    private List<Entry<CodeGeneratorArg, BasicCodeGenerator>> instantiateGenerators() throws MojoExecutionException {
        final List<Entry<CodeGeneratorArg, BasicCodeGenerator>> generators = new ArrayList<>(codeGeneratorArgs.size());
        for (CodeGeneratorArg arg : codeGeneratorArgs) {
            arg.check();

            final BasicCodeGenerator generator;
            try {
                generator = getInstance(arg.getCodeGeneratorClass(), BasicCodeGenerator.class);
            } catch (ClassNotFoundException | InstantiationException | IllegalAccessException e) {
                throw new MojoExecutionException("Failed to instantiate code generator "
                        + arg.getCodeGeneratorClass(), e);
            }

            LOG.info("{} Code generator instantiated from {}", LOG_PREFIX, arg.getCodeGeneratorClass());
            generators.add(new SimpleImmutableEntry<>(arg, generator));
        }

        return generators;
    }

    @SuppressWarnings("checkstyle:illegalCatch")
    private Optional<ProcessorModuleReactor> createReactor(final StatementParserMode parserMode,
            final List<File> yangFilesInProject) throws MojoExecutionException {
        LOG.info("{} Inspecting {}", LOG_PREFIX, yangFilesRootDir);
        try {

            final Collection<File> allFiles = new ArrayList<>(yangFilesInProject);
            if (inspectDependencies) {
                allFiles.addAll(Util.findYangFilesInDependencies(project));
            }

            /*
             * Check if any of the listed files changed. If no changes occurred,
             * simply return null, which indicates and of execution.
             */
            if (!allFiles.stream().anyMatch(buildContext::hasDelta)) {
                LOG.info("{} None of {} input files changed", LOG_PREFIX, allFiles.size());
                return Optional.empty();
            }

            final YangParser parser = parserFactory.createParser(parserMode);
            final List<YangTextSchemaSource> sourcesInProject = new ArrayList<>(yangFilesInProject.size());
            for (final File f : yangFilesInProject) {
                final YangTextSchemaSource textSource = YangTextSchemaSource.forFile(f);
                final ASTSchemaSource astSource = TextToASTTransformer.transformText(textSource);

                parser.addSource(astSource);

                if (!astSource.getIdentifier().equals(textSource.getIdentifier())) {
                    // AST indicates a different source identifier, make sure we use that
                    sourcesInProject.add(YangTextSchemaSource.delegateForByteSource(astSource.getIdentifier(),
                        textSource));
                } else {
                    sourcesInProject.add(textSource);
                }
            }

            LOG.debug("Processed project files: {}", yangFilesInProject);
            LOG.info("{} Project model files parsed: {}", LOG_PREFIX, yangFilesInProject.size());

            final ProcessorModuleReactor reactor = new ProcessorModuleReactor(parser, sourcesInProject);
            LOG.debug("Initialized reactor {}", reactor, yangFilesInProject);
            return Optional.of(reactor);
        } catch (Exception e) {
            // MojoExecutionException is thrown since execution cannot continue
            LOG.error("{} Unable to parse YANG files from {}", LOG_PREFIX, yangFilesRootDir, e);
            Throwable rootCause = Throwables.getRootCause(e);
            throw new MojoExecutionException(LOG_PREFIX + " Unable to parse YANG files from " + yangFilesRootDir,
                rootCause);
        }
    }

    private ContextHolder createContextHolder(final ProcessorModuleReactor reactor) throws MojoFailureException,
            IOException, YangParserException {
        /**
         * Set contains all modules generated from input sources. Number of
         * modules may differ from number of sources due to submodules
         * (parsed submodule's data are added to its parent module). Set
         * cannot contains null values.
         */
        if (inspectDependencies) {
            final List<YangTextSchemaSource> sourcesInDependencies = Util.findYangFilesInDependenciesAsStream(
                project);
            for (YangTextSchemaSource s : toUniqueSources(sourcesInDependencies)) {
                reactor.registerSourceFromDependency(s);
            }
        }

        return reactor.toContext();
    }

    private static List<File> listFiles(final File root, final Collection<File> excludedFiles)
            throws IOException {
        if (!root.isDirectory()) {
            LOG.warn("{} YANG source directory {} not found. No code will be generated.", LOG_PREFIX, root);
            return ImmutableList.of();
        }

        return Files.walk(root.toPath()).map(Path::toFile).filter(File::isFile).filter(f -> {
            if (excludedFiles.contains(f)) {
                LOG.info("{} YANG file excluded {}", LOG_PREFIX, f);
                return false;
            }
            return true;
        }).filter(f -> f.getName().endsWith(YangConstants.RFC6020_YANG_FILE_EXTENSION)).collect(Collectors.toList());
    }

    private static Collection<YangTextSchemaSource> toUniqueSources(final Collection<YangTextSchemaSource> sources)
            throws IOException {
        final Map<String, YangTextSchemaSource> byContent = new HashMap<>();
        for (YangTextSchemaSource s : sources) {
            try (Reader reader = s.asCharSource(StandardCharsets.UTF_8).openStream()) {
                final String contents = CharStreams.toString(reader);
                byContent.putIfAbsent(contents, s);
            }
        }
        return byContent.values();
    }

    /**
     * Call generate on every generator from plugin configuration.
     */
    @SuppressWarnings("checkstyle:illegalCatch")
    private void generateSources(final ContextHolder context,
            final Collection<Entry<CodeGeneratorArg, BasicCodeGenerator>> generators) throws MojoFailureException {
        if (generators.isEmpty()) {
            LOG.warn("{} No code generators provided", LOG_PREFIX);
            return;
        }

        final Map<String, String> thrown = new HashMap<>();
        for (Entry<CodeGeneratorArg, BasicCodeGenerator> entry : generators) {
            final String codeGeneratorClass = entry.getKey().getCodeGeneratorClass();

            try {
                generateSourcesWithOneGenerator(context, entry.getKey(), entry.getValue());
            } catch (Exception e) {
                // try other generators, exception will be thrown after
                LOG.error("{} Unable to generate sources with {} generator", LOG_PREFIX, codeGeneratorClass, e);
                thrown.put(codeGeneratorClass, e.getClass().getCanonicalName());
            }
        }

        if (!thrown.isEmpty()) {
            String message = " One or more code generators failed, including failed list(generatorClass=exception) ";
            LOG.error("{}{}{}", LOG_PREFIX, message, thrown.toString());
            throw new MojoFailureException(LOG_PREFIX + message + thrown.toString());
        }
    }

    /**
     * Complete initialization of a code generator and invoke it.
     */
    private void generateSourcesWithOneGenerator(final ContextHolder context, final CodeGeneratorArg codeGeneratorCfg,
            final BasicCodeGenerator codeGenerator) throws IOException {

        final File outputDir = requireNonNull(codeGeneratorCfg.getOutputBaseDir(project),
            "outputBaseDir is null. Please provide a valid outputBaseDir value in pom.xml");

        project.addCompileSourceRoot(outputDir.getAbsolutePath());

        LOG.info("{} Sources will be generated to {}", LOG_PREFIX, outputDir);
        LOG.debug("{} Project root dir is {}", LOG_PREFIX, project.getBasedir());
        LOG.debug("{} Additional configuration picked up for : {}: {}", LOG_PREFIX, codeGeneratorCfg
                        .getCodeGeneratorClass(), codeGeneratorCfg.getAdditionalConfiguration());

        if (codeGenerator instanceof BuildContextAware) {
            ((BuildContextAware)codeGenerator).setBuildContext(buildContext);
        }
        if (codeGenerator instanceof MavenProjectAware) {
            ((MavenProjectAware)codeGenerator).setMavenProject(project);
        }
        codeGenerator.setAdditionalConfig(codeGeneratorCfg.getAdditionalConfiguration());
        File resourceBaseDir = codeGeneratorCfg.getResourceBaseDir(project);

        YangProvider.setResource(resourceBaseDir, project);
        codeGenerator.setResourceBaseDir(resourceBaseDir);
        LOG.debug("{} Folder: {} marked as resources for generator: {}", LOG_PREFIX, resourceBaseDir,
                codeGeneratorCfg.getCodeGeneratorClass());

        if (outputDir.exists()) {
            Files.walk(outputDir.toPath()).sorted(Comparator.reverseOrder()).map(Path::toFile).forEach(File::delete);
            LOG.info("{} Succesfully deleted output directory {}", LOG_PREFIX, outputDir);
        }
        Collection<File> generated = codeGenerator.generateSources(context.getContext(), outputDir,
            context.getYangModules(), context::moduleToResourcePath);

        LOG.info("{} Sources generated by {}: {}", LOG_PREFIX, codeGeneratorCfg.getCodeGeneratorClass(), generated);
    }

    /**
     * Instantiate object from fully qualified class name.
     */
    private static <T> T getInstance(final String codeGeneratorClass, final Class<T> baseType) throws
            ClassNotFoundException, InstantiationException, IllegalAccessException {
        final Class<?> clazz = Class.forName(codeGeneratorClass);
        checkArgument(baseType.isAssignableFrom(clazz), "Code generator %s has to implement %s", clazz, baseType);
        return baseType.cast(clazz.newInstance());
    }
}