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package org.jooby.assets;

import com.google.common.base.CaseFormat;
import com.google.common.base.Splitter;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableSet;
import com.google.common.io.ByteStreams;
import com.google.common.io.Closeables;
import com.typesafe.config.Config;
import com.typesafe.config.ConfigFactory;
import com.typesafe.config.ConfigValue;
import static java.util.Objects.requireNonNull;
import org.jooby.MediaType;
import org.jooby.funzy.Try;
import org.jooby.internal.assets.AssetWriter;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.nio.charset.Charset;
import java.nio.file.Path;
import java.time.Duration;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import java.util.function.BiConsumer;
import java.util.function.Consumer;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.stream.Collectors;
import java.util.stream.Stream;

/**
 * <h1>Asset compiler</h1>
 * <p>
 * Process static files by validate or modify them in some way.
 * </p>
 *
 * @author edgar
 * @see AssetProcessor
 * @see Assets
 * @since 0.11.0
 */
public class AssetCompiler {

    /** The logging system. */
    private final Logger log = LoggerFactory.getLogger(getClass());

    private final Map<String, List<AssetProcessor>> pipeline;

    private final List<AssetAggregator> aggregators = new ArrayList<>();

    private final Map<String, List<String>> fileset;

    private final Predicate<String> scripts;

    private final Predicate<String> styles;

    private final Config conf;

    private final Charset charset;

    private final EngineFactory engineFactory;

    private ClassLoader loader;

    private BiConsumer<Integer, Integer> progress;

    public AssetCompiler(final Config conf) throws Exception {
        this(AssetClassLoader.classLoader(conf.getClass().getClassLoader()), conf);
    }

    public AssetCompiler(final ClassLoader loader, final Config conf) throws Exception {
        this.loader = loader;
        this.conf = requireNonNull(conf, "Assets conf is required.");
        String basedir = conf.hasPath("assets.basedir") ? spath(conf.getString("assets.basedir")) : "";
        this.charset = Charset.forName(this.conf.getString("assets.charset"));
        this.engineFactory = engineFactory(loader);
        if (this.conf.hasPath("assets.fileset")) {
            this.fileset = fileset(this.loader, engineFactory, basedir, this.conf, aggregators::add);
        } else {
            this.fileset = new HashMap<>();
        }
        this.scripts = predicate(this.conf, ".js", ".coffee", ".ts");
        this.styles = predicate(this.conf, ".css", ".scss", ".sass", ".less");
        if (this.fileset.size() > 0) {
            this.pipeline = pipeline(this.loader, engineFactory, this.conf.getConfig("assets"));
        } else {
            this.pipeline = Collections.emptyMap();
        }
    }

    /**
     * Get all the assets for the provided file set. Example:
     *
     * <pre>
     * assets {
     *   fileset {
     *     home: [home.css, home.js]
     *   }
     * }
     * </pre>
     *
     * This method returns <code>home.css</code> and <code>home.js</code> for <code>home</code> file
     * set. If there is no fileset under that name then it returns an empty list.
     *
     * @param name Fileset name.
     * @return List of files or empty list.
     */
    public List<String> assets(final String name) {
        return fileset.getOrDefault(name, Collections.emptyList());
    }

    /**
     * @return Returns all the fileset.
     */
    public Set<String> fileset() {
        return fileset.keySet();
    }

    /**
     * Iterate over fileset and common path pattern for them. Example:
     *
     * <pre>
     * {
     *   assets {
     *     fileset {
     *       lib: [js/lib/jquery.js],
     *       home: [css/style.css, js/home.js]
     *     }
     *   }
     * }
     * </pre>
     *
     * This method returns a set with <code>/css/**</code> and <code>/js/**</code> pattern.
     *
     * @return Path pattern of the entire fileset.
     */
    public Set<String> patterns() {
        return patterns(file -> aggregators.stream().noneMatch(it -> it.fileset().contains(file)))
                .map(v -> "/" + v + "/**").collect(Collectors.toCollection(LinkedHashSet::new));
    }

    /**
     * Get all the javascript (or derived) for the provided fileset. Example:
     *
     * <pre>
     * {
     *   assets {
     *     fileset {
     *       mypage: [mypage.js, mypage.css]
     *     }
     *   }
     * }
     * </pre>
     *
     * <p>
     * This method returns <code>mypage.js</code> for <code>mypage</code> fileset.
     * </p>
     *
     * @param fileset Fileset name.
     * @return All the scripts for a fileset.
     */
    public List<String> scripts(final String fileset) {
        return assets(fileset).stream().filter(scripts).collect(Collectors.toList());
    }

    /**
     * Get all the css files (or derived) for the provided fileset. Example:
     *
     * <pre>
     * {
     *   assets {
     *     fileset {
     *       mypage: [mypage.js, mypage.css]
     *     }
     *   }
     * }
     * </pre>
     *
     * <p>
     * This method returns <code>mypage.js</code> for <code>mypage</code> fileset.
     * </p>
     *
     * @param fileset Fileset name.
     * @return All the scripts for a fileset.
     */
    public List<String> styles(final String fileset) {
        return assets(fileset).stream().filter(styles).collect(Collectors.toList());
    }

    /**
     * List all the {@link AssetProcessor} for a distribution (a.k.a. environment).
     *
     * @param dist Distribution's name.
     * @return A readonly list of available {@link AssetProcessor}.
     */
    public List<AssetProcessor> pipeline(final String dist) {
        List<AssetProcessor> chain = this.pipeline.get(dist);
        if (chain == null) {
            log.debug("no pipeline for: {}", dist);
            return Collections.emptyList();
        }
        return Collections.unmodifiableList(chain);
    }

    /**
     * @return Readonly list of available {@link AssetAggregator}.
     */
    public List<AssetAggregator> aggregators() {
        return Collections.unmodifiableList(aggregators);
    }

    /**
     * Build assets using the given distribution and write output to the provided directory.
     *
     * Build process is defined as follow:
     *
     * 1. First, it runs all the aggregators (if any)
     * 2. Then iterates each fileset and per each file in the fileset it apply the processor pipeline.
     * 3. Finally, it merge all the files into one file and compressed/optimized if need it.
     *
     * @param dist Distribution's name (usually dev or dist).
     * @param dir Output directory.
     * @return Map with fileset name as key and list of generated assets.
     * @throws Exception If something goes wrong.
     */
    public Map<String, List<File>> build(final String dist, final File dir) throws Exception {
        log.debug("{} aggregators: {}", dist, aggregators);
        aggregators(aggregators, conf);

        return buildInternal(dist, dir);
    }

    private Map<String, List<File>> buildInternal(final String dist, final File dir) throws Exception {
        Map<String, List<File>> output = new LinkedHashMap<>();

        List<AssetProcessor> pipeline = pipeline(dist);

        Set<String> processed = new HashSet<>();
        Predicate<String> shouldProcess = dist.equals("dev") ? processed::add : path -> true;

        int total = fileset.values().stream().mapToInt(List::size).sum();
        int count = 0;
        log.debug("{} pipeline: {}", dist, pipeline);
        for (Entry<String, List<String>> entries : fileset.entrySet()) {
            String fset = entries.getKey();
            List<String> files = entries.getValue();

            log.debug("compiling {}:", fset);

            /** CSS: */
            AssetWriter css = new AssetWriter(dist, fset, dir, ".css", "", charset, this.fileset, styles);
            count += compile(pipeline, files.stream().filter(styles).iterator(), MediaType.css, css, shouldProcess,
                    count, total);
            List<File> result = new ArrayList<>(css.getResult());

            /** JavaScript: */
            AssetWriter js = new AssetWriter(dist, fset, dir, ".js", ";", charset, this.fileset, scripts);
            count += compile(pipeline, files.stream().filter(scripts).iterator(), MediaType.js, js, shouldProcess,
                    count, total);
            result.addAll(js.getResult());

            result.forEach(it -> log.debug("{} {} ({})", it.getName(), humanReadableByteCount(it.length()), it));
            output.put(fset, result);
        }
        return output;
    }

    private void aggregators(final List<AssetAggregator> aggregators, final Config conf) throws Exception {
        for (AssetAggregator it : aggregators) {
            log.debug("applying {}", it);
            it.run(conf);
        }

    }

    /**
     * Apply the processor pipeline to the given asset. Like {@link #build(String, File)} but for a
     * single file or asset.
     *
     * @param filename Asset to build.
     * @return Processed asset.
     * @throws Exception If something goes wrong.
     */
    public File buildOne(String filename, File dir) throws Exception {

        String dist = "dev";
        final MediaType type;
        AssetWriter writer;
        if (scripts.test(filename)) {
            type = MediaType.js;
            writer = new AssetWriter(dist, null, dir, ".js", ";", charset, this.fileset, scripts);
        } else if (styles.test(filename)) {
            type = MediaType.css;
            writer = new AssetWriter(dist, null, dir, ".css", "", charset, this.fileset, styles);
        } else {
            return null;
        }

        List<AssetProcessor> pipeline = pipeline(dist);
        compile(pipeline, ImmutableList.of(filename).iterator(), type, writer, path -> true, 0, 0);

        return new File(dir, filename);
    }

    /**
     * Print a summary of the given results.
     *
     * @param result Compilation result.
     * @param outDir Output directory.
     * @param dist Distribution (dev or prod).
     * @param duration Execution time in millis.
     * @param extraInfo Additional information.
     * @return Summary.
     */
    public String summary(Map<String, List<File>> result, Path outDir, String dist, long duration,
            String... extraInfo) {
        StringBuilder buffer = new StringBuilder();

        buffer.append("Summary:\n");
        long seconds = Duration.ofMillis(duration).getSeconds();
        String took = seconds > 0 ? seconds + "s" : duration + "ms";
        buffer.append("Pipeline: ").append(pipeline(dist)).append("\n");
        buffer.append("Time: ").append(took).append("\n");
        buffer.append("Output: ").append(outDir).append("\n");
        Stream.of(extraInfo).forEach(line -> buffer.append(line).append("\n"));
        int w1 = result.keySet().stream().map(it -> it.length() + 2).max(Integer::compareTo).orElse(0);
        int mw1 = Math.max(w1, "Fileset".length() + 2);
        int w2 = result.values().stream().flatMap(List::stream)
                .map(file -> outDir.relativize(file.toPath()).toString()).map(String::length)
                .max(Integer::compareTo).orElse(0);
        buffer.append(format(w1, w2, "Fileset", "Output", "Size"));
        result.forEach((fileset, files) -> {
            if (files.size() > 0) {
                // Head
                buffer.append(format(mw1, w2, "  " + fileset, "", ""));
                // Tail
                files.forEach(file -> buffer.append(format(mw1, w2, "", outDir.relativize(file.toPath()),
                        AssetCompiler.humanReadableByteCount(file.length()))));
            }
        });
        return buffer.toString();
    }

    private static String format(int w1, int w2, Object... args) {
        return String.format("%-" + w1 + "s %" + w2 + "s %10s\n", args);
    }

    @Override
    public String toString() {
        return fileset.toString();
    }

    public void stop() {
        if (engineFactory != null) {
            this.engineFactory.release();
        }
    }

    /**
     * Set a progress bar.
     *
     * @param progress Progress bar.
     */
    public void setProgressBar(BiConsumer<Integer, Integer> progress) {
        this.progress = progress;
    }

    private Stream<String> patterns(final Predicate<String> filter) {
        return fileset.values().stream().flatMap(List::stream).filter(filter).map(path -> path.split("/")[1]);

    }

    private int compile(final List<AssetProcessor> pipeline, final Iterator<String> files, final MediaType type,
            final AssetWriter writer, Predicate<String> process, int progress, int total) throws Exception {
        int count = 0;
        while (files.hasNext()) {
            String file = files.next();
            if (process.test(file)) {
                String chunk = compile(pipeline, file, type, readFile(loader, file, charset));
                writer.write(file, chunk);
            } else {
                writer.add(file);
            }
            count += 1;
            if (this.progress != null) {
                this.progress.accept(progress + count, total);
            }
        }
        return count;
    }

    private String compile(final List<AssetProcessor> pipeline, final String filename, final MediaType type,
            final String input) throws Exception {

        log.debug("  {}", filename);
        Iterator<AssetProcessor> it = pipeline.iterator();
        String output = input;
        while (it.hasNext()) {
            AssetProcessor processor = it.next();
            if (processor.matches(type) && !processor.excludes(filename)) {
                String pname = processor.name();
                long start = System.currentTimeMillis();
                try {
                    log.debug("    executing: {}", pname);
                    output = processor.process(filename, output, conf, loader);
                } finally {
                    long end = System.currentTimeMillis();
                    log.debug("    {} took {}ms", pname, end - start);
                }
            }
        }
        return output;
    }

    private static String readFile(final ClassLoader loader, final String path, final Charset charset)
            throws IOException {
        String spath = path.startsWith("/") ? path.substring(1) : path;
        InputStream resource = loader.getResourceAsStream(spath);
        if (resource == null) {
            throw new FileNotFoundException(path);
        }
        return toString(resource, charset);
    }

    private static String toString(final InputStream in, final Charset charset) throws IOException {
        try {
            return new String(ByteStreams.toByteArray(in), charset);
        } finally {
            Closeables.closeQuietly(in);
        }
    }

    private static Predicate<String> predicate(final Config fileset, final String... extension) {
        String path = "assets" + extension[0];
        Set<String> extensions = new HashSet<>(Arrays.asList(extension));
        if (fileset.hasPath(path)) {
            extensions.addAll(strlist(fileset.getAnyRef(path)));
        }
        return file -> {
            for (String ext : extensions) {
                if (file.endsWith(ext)) {
                    return true;
                }
            }
            return false;
        };
    }

    private static Map<String, List<String>> fileset(final ClassLoader loader, final EngineFactory engineFactory,
            final String basedir, final Config conf, final Consumer<AssetAggregator> aggregators) {
        Map<String, List<String>> raw = new HashMap<>();
        Map<String, List<String>> graph = new HashMap<>();
        Config assetconf = conf.getConfig("assets");
        Config fileset = assetconf.getConfig("fileset");
        // 1st pass, collect single resources (no merge)
        fileset.entrySet().forEach(e -> {
            List<String> key = Splitter.on('<').trimResults().omitEmptyStrings().splitToList(unquote(e.getKey()));
            List<String> candidates = strlist(e.getValue().unwrapped(), v -> basedir + spath(v));
            List<String> values = new ArrayList<>();
            candidates.forEach(it -> Try
                    .run(() -> processors(assetconf, loader, engineFactory, null, ImmutableList.of(it.substring(1)),
                            ImmutableSet.of()).stream().filter(AssetAggregator.class::isInstance).forEach(p -> {
                                AssetAggregator a = (AssetAggregator) p;
                                aggregators.accept(a);
                                a.fileset().forEach(f -> values.add(spath(f)));
                            }))
                    .onFailure(x -> values.add(it)));
            raw.put(key.get(0), values);
            graph.put(key.get(0), key);
        });

        Map<String, List<String>> resolved = new HashMap<>();
        graph.forEach((fs, deps) -> resolve(fs, deps, raw, graph, resolved));
        return resolved;
    }

    private static List<String> resolve(final String fs, final List<String> deps,
            final Map<String, List<String>> raw, final Map<String, List<String>> graph,
            final Map<String, List<String>> resolved) {
        List<String> result = resolved.get(fs);
        if (result == null) {
            result = new ArrayList<>();
            resolved.put(fs, result);
            for (int i = deps.size() - 1; i > 0; i--) {
                result.addAll(resolve(deps.get(i), graph.get(deps.get(i)), raw, graph, resolved));
            }
            result.addAll(raw.get(fs));
        }
        return result;
    }

    private static String unquote(final String key) {
        return key.replace("\"", "");
    }

    private static Map<String, List<AssetProcessor>> pipeline(final ClassLoader loader,
            final EngineFactory engineFactory, final Config conf) throws Exception {
        Map<String, List<AssetProcessor>> processors = new HashMap<>();
        processors.put("dev", Collections.emptyList());
        if (conf.hasPath("pipeline")) {
            Set<String> filter = conf.getConfig("pipeline").entrySet().stream().map(Entry::getKey)
                    .collect(Collectors.toSet());
            filter.add("class");
            Set<Entry<String, ConfigValue>> entrySet = conf.getConfig("pipeline").entrySet();
            for (Entry<String, ConfigValue> entry : entrySet) {
                String env = unquote(entry.getKey());
                processors.put(env, processors(conf, loader, engineFactory, env,
                        strlist(entry.getValue().unwrapped()), filter));
            }
        }
        return processors;
    }

    @SuppressWarnings("unchecked")
    private static <T extends AssetOptions> List<T> processors(final Config conf, final ClassLoader loader,
            final EngineFactory engineFactory, final String env, final List<String> names, final Set<String> filter)
            throws Exception {
        Map<String, Class<AssetOptions>> classes = new LinkedHashMap<>();
        for (Entry<String, String> entry : bind(conf, names).entrySet()) {
            classes.put(entry.getKey(), (Class<AssetOptions>) loader.loadClass(entry.getValue()));
        }
        return (List<T>) processors(conf, loader, engineFactory, env, filter, classes);
    }

    @SuppressWarnings("unchecked")
    private static <T extends AssetOptions> List<T> processors(final Config conf, final ClassLoader loader,
            final EngineFactory engineFactory, final String env, final Set<String> filter,
            final Map<String, Class<T>> classes) throws Exception {
        List<T> processors = new ArrayList<>();
        Function<Config, Config> without = options -> {
            for (String path : filter) {
                options = options.withoutPath(path);
            }
            return options;
        };
        for (Entry<String, Class<T>> entry : classes.entrySet()) {
            String name = entry.getKey();
            Class<T> clazz = entry.getValue();
            Config options = ConfigFactory.empty();
            if (conf.hasPath(name)) {
                options = conf.getConfig(name);
                if (env != null && options.hasPath(env)) {
                    options = options.getConfig(env).withFallback(options);
                }
            }
            AssetOptions processor = clazz.newInstance();
            processor.set(without.apply(options));
            processors.add((T) processor);
            if (processor instanceof AssetProcessor) {
                ((AssetProcessor) processor).set(engineFactory);
            }
        }
        return processors;
    }

    private static EngineFactory engineFactory(ClassLoader loader) throws Exception {
        try {
            return (EngineFactory) loader
                    .loadClass(System.getProperty("assets.engine", "org.jooby.assets.V8EngineFactory"))
                    .newInstance();
        } catch (ClassNotFoundException e) {
            // Ignore:
            return null;
        }
    }

    private static Map<String, String> bind(final Config conf, final List<String> names) {
        Map<String, String> map = new LinkedHashMap<>();
        names.forEach(name -> {
            String clazz = AssetCompiler.class.getPackage().getName() + "."
                    + CaseFormat.LOWER_HYPHEN.to(CaseFormat.UPPER_CAMEL, name);
            if (conf.hasPath(name + ".class")) {
                clazz = conf.getString(name + ".class");
            }
            map.put(name, clazz);
        });

        return map;
    }

    private static List<String> strlist(final Object value) {
        return strlist(value, v -> v);
    }

    @SuppressWarnings("unchecked")
    private static List<String> strlist(final Object value, final Function<String, String> mapper) {
        ImmutableList.Builder<String> list = ImmutableList.builder();
        if (value instanceof Collection) {
            ((Collection<? extends String>) value).forEach(v -> list.add(mapper.apply(v)));
        } else {
            list.add(mapper.apply(value.toString()));
        }
        return list.build();
    }

    private static String spath(final String path) {
        return path.charAt(0) == '/' ? path : "/" + path;
    }

    // http://stackoverflow.com/questions/3758606/how-to-convert-byte-size-into-human-readable-format-in-java
    static String humanReadableByteCount(final long bytes) {
        int unit = 1024;
        if (bytes < unit) {
            return bytes + "b";
        }
        int exp = (int) (Math.log(bytes) / Math.log(unit));
        char pre = "kmgtpe".charAt(exp - 1);
        return String.format("%.1f%sb", bytes / Math.pow(unit, exp), pre);
    }

}