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Modules for processing bibliographic data
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/*
 * Copyright 2016 Christoph Böhme
 *
 * Licensed under the Apache License, Version 2.0 the "License";
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.metafacture.biblio.pica;


/**
 * A parser for PICA+ records. Only single records can be parsed as the parser
 * ignores end of record markers. The initial parser state is FIELD_NAME. All
 * states are valid end states. The parser processes any input, there is no
 * error state.
 *
 * The parser ignores spaces in field names. They are not included in the
 * field name.
 *
 * Empty subfields are skipped. For instance, parsing the following input
 * would NOT produce an empty literal: 003@ \u001f\u001e. The parser also
 * skips unnamed fields without any subfields.
 *
 * @author Christoph Böhme
 *
 */
enum PicaParserState {

    FIELD_NAME {
        @Override
        protected PicaParserState parseChar(final char ch, final PicaParserContext ctx) {
            final PicaParserState next;
            switch (ch) {
            case PicaConstants.RECORD_MARKER:
            case PicaConstants.FIELD_MARKER:
            case PicaConstants.FIELD_END_MARKER:
                ctx.emitStartEntity();
                ctx.emitEndEntity();
                next = FIELD_NAME;
                break;
            case PicaConstants.SUBFIELD_MARKER:
                ctx.emitStartEntity();
                next = SUBFIELD_NAME;
                break;
            default:
                ctx.appendText(ch);
                next = this;
            }
            return next;
        }

        @Override
        protected void endOfInput(final PicaParserContext ctx) {
            ctx.emitStartEntity();
            ctx.emitEndEntity();
        }
    },
    SUBFIELD_NAME {
        @Override
        protected PicaParserState parseChar(final char ch, final PicaParserContext ctx) {
            final PicaParserState next;
            switch (ch) {
            case PicaConstants.RECORD_MARKER:
            case PicaConstants.FIELD_MARKER:
            case PicaConstants.FIELD_END_MARKER:
                ctx.emitEndEntity();
                next = FIELD_NAME;
                break;
            case PicaConstants.SUBFIELD_MARKER:
                next = this;
                break;
            default:
                ctx.setSubfieldName(ch);
                next = SUBFIELD_VALUE;
            }
            return next;
        }

        @Override
        protected void endOfInput(final PicaParserContext ctx) {
            ctx.emitEndEntity();
        }
    },
    SUBFIELD_VALUE {
        @Override
        protected PicaParserState parseChar(final char ch, final PicaParserContext ctx) {
            final PicaParserState next;
            switch (ch) {
            case PicaConstants.RECORD_MARKER:
            case PicaConstants.FIELD_MARKER:
            case PicaConstants.FIELD_END_MARKER:
                ctx.emitLiteral();
                ctx.emitEndEntity();
                next = FIELD_NAME;
                break;
            case PicaConstants.SUBFIELD_MARKER:
                ctx.emitLiteral();
                next = SUBFIELD_NAME;
                break;
            default:
                ctx.appendText(ch);
                next = this;
            }
            return next;
        }

        @Override
        protected void endOfInput(final PicaParserContext ctx) {
            ctx.emitLiteral();
            ctx.emitEndEntity();
        }
    };

    protected abstract PicaParserState parseChar(final char ch, final PicaParserContext ctx);

    protected abstract void endOfInput(final PicaParserContext ctx);

}