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/*
 * Copyright (c) 2010-2017, KolibriFX AS. Licensed under the Apache License, version 2.0.
 */

package com.kolibrifx.plovercrest.server.internal;

import java.io.File;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
import java.util.UUID;
import org.apache.commons.io.Charsets;
import org.apache.commons.io.FileUtils;
import org.apache.commons.io.FilenameUtils;
import com.kolibrifx.plovercrest.client.PlovercrestException;
import com.kolibrifx.plovercrest.client.TableMetadata;
import com.kolibrifx.plovercrest.client.internal.shared.PlovercrestConstants;
import com.kolibrifx.plovercrest.client.internal.shared.TableMetadataUtils;
import com.kolibrifx.plovercrest.server.TableInfo;

public final class TableInfoSerializer {
    private static final String FANOUT_DISTANCE_FIELD = "com.kolibrifx.plovercrest.fanout-distance";
    private static final String TABLE_NAME_FIELD = "com.kolibrifx.plovercrest.table-name";
    // Prefix that indicates that the (unsanitized) file name may not be the same as the table name.
    // For all file names that start with this prefix, the plovercrest engine must read contents of
    // the .info file to find the actual table name. This can be considerably slower than just using
    // the file name.
    private static final String LONG_NAME_FILENAME_INDICATOR = "__";

    private TableInfoSerializer() {
    }

    public static void write(final TableInfo info, final File infoFile) throws IOException {
        final Map builtinFields = new HashMap<>();
        builtinFields.put(FANOUT_DISTANCE_FIELD, Integer.toString(info.getFanOutDistance()));
        if (!info.getName().equals(unsanitizedTableName(infoFile))) {
            builtinFields.put(TABLE_NAME_FIELD, info.getName());
        }
        final TableMetadata metadata;
        if (info.getMetadata() == null) {
            metadata = new TableMetadata(builtinFields);
        } else {
            metadata = info.getMetadata().addFields(builtinFields);
        }
        FileUtils.write(infoFile, metadata.toPersistableString(), Charsets.UTF_8);
    }

    public static TableInfo read(final File infoFile) throws IOException {
        final String metadataStr = FileUtils.readFileToString(infoFile, Charsets.UTF_8);
        final TableMetadata metadata = TableMetadataUtils.parse(metadataStr);
        final int fanoutDistance =
                metadata.tryGetInt(FANOUT_DISTANCE_FIELD, PlovercrestConstants.DEFAULT_FANOUT_DISTANCE);
        final String tableName = metadata.containsKey(TABLE_NAME_FIELD) ? metadata.get(TABLE_NAME_FIELD)
                : unsanitizedTableName(infoFile);
        return new TableInfo(tableName, fanoutDistance, metadata);
    }

    private static String unsanitizedTableName(final File infoFile) {
        final String saneName = FilenameUtils.removeExtension(infoFile.getName());
        final String tableName = PathUtils.unsanitize(saneName);
        return tableName;
    }

    public static String tableNameFromInfoFile(final File infoFile) {
        if (infoFile.getName().startsWith(LONG_NAME_FILENAME_INDICATOR)) {
            try {
                return read(infoFile).getName();
            } catch (final IOException e) {
                throw new PlovercrestException("Failed to read table name from info file " + infoFile, e);
            }
        }
        return unsanitizedTableName(infoFile);
    }

    public static String generateUniqueFileNamePrefix() {
        return LONG_NAME_FILENAME_INDICATOR + UUID.randomUUID().toString();
    }
}