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Permazen core API classes which provide objects, fields, indexes, queries, and schema management on top of a key/value store.
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/*
 * Copyright (C) 2015 Archie L. Cobbs. All rights reserved.
 */

package io.permazen.core;

import com.google.common.base.Preconditions;

import io.permazen.encoding.Encoding;
import io.permazen.kv.KeyFilter;
import io.permazen.kv.KeyFilterUtil;
import io.permazen.kv.KeyRanges;
import io.permazen.util.ByteUtil;

import java.util.Arrays;

/**
 * Common superclass for index view classes. Represents an index with optional filters on each field in the index.
 */
abstract class AbstractIndexView {

    final byte[] prefix;                    // prefix that is always expected and skipped over
    final boolean prefixMode;               // whether this instance requires prefix mode (i.e., entire key not consumed)
    final Encoding[] encodings;          // the encodings of the indexed values
    final KeyFilter[] filters;              // the filter that applies to each encoding, or null

    /**
     * Constructor.
     *
     * @param prefix key prefix
     * @param prefixMode true if prefix mode required because {@code encodings} does not extend through the final value
     * @param encodings encodings
     * @throws IllegalArgumentException if {@code prefix} is null or empty
     * @throws IllegalArgumentException if {@code filter} is null or empty
     */
    protected AbstractIndexView(byte[] prefix, boolean prefixMode, Encoding... encodings) {
        Preconditions.checkArgument(prefix != null && prefix.length > 0, "null/empty prefix");
        Preconditions.checkArgument(encodings != null, "null encodings");
        this.prefix = prefix;
        this.prefixMode = prefixMode;
        this.encodings = encodings;
        for (int i = 0; i < this.encodings.length; i++)
            this.encodings[i] = Index.genericize(this.encodings[i]);
        this.filters = new KeyFilter[this.encodings.length];
    }

    /**
     * Copy-ish constructor for filter().
     */
    protected AbstractIndexView(AbstractIndexView original) {
        this.prefix = original.prefix;
        this.prefixMode = original.prefixMode;
        this.encodings = original.encodings;
        this.filters = original.filters.clone();
    }

    public KeyFilter getFilter(int index) {
        return this.filters[index];
    }

    public boolean hasFilters() {
        for (KeyFilter filter : this.filters) {
            if (filter != null)
                return true;
        }
        return false;
    }

    public AbstractIndexView filter(int index, KeyFilter filter) {
        Preconditions.checkArgument(filter != null, "null filter");
        if (filter instanceof KeyRanges && ((KeyRanges)filter).isFull())
            return this;
        if (this.filters[index] != null)
            filter = KeyFilterUtil.intersection(filter, this.filters[index]);
        final AbstractIndexView copy = this.copy();
        copy.filters[index] = filter;
        return copy;
    }

    protected abstract AbstractIndexView copy();

    @Override
    public String toString() {
        return this.getClass().getSimpleName()
          + "[prefix=" + ByteUtil.toString(this.prefix)
          + ",prefixMode=" + prefixMode
          + ",encodings=" + Arrays.asList(this.encodings)
          + (this.hasFilters() ? ",filters=" + Arrays.asList(this.filters) : "")
          + "]";
    }
}