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package jscl.text;

import jscl.MathContext;
import jscl.math.Generic;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

/**
 * Main parser interface.
 * 
 * Aim of parser is to convert input string expression into java objects
 *
 * @param  type of result object of parser
 */
public interface Parser {

	/**
	 * @param p                  parse parameters
	 * @param previousSumElement sum element to the left of last + sign
	 * @return parsed object of type T
	 * @throws ParseException occurs if object could not be parsed from the string
	 */
	T parse(@Nonnull Parameters p, @Nullable Generic previousSumElement) throws ParseException;

	static class Parameters {

		@Nonnull
		private final String expression;

		@Nonnull
		private final MutableInt position;

		@Nonnull
		private final List exceptions = new ArrayList();

		@Nonnull
		private final MathContext mathContext;

		/**
		 * @param expression  expression to be parsed
		 * @param position    current position of expression. Side effect: if parsing is successful this parameter should be increased on the number of parsed letters (incl whitespaces etc)
		 * @param mathContext math engine to be used in parsing
		 */
		Parameters(@Nonnull String expression, @Nonnull MutableInt position, @Nonnull MathContext mathContext) {
			this.expression = expression;
			this.position = position;
			this.mathContext = mathContext;
		}

		@Nonnull
		public static Parameters newInstance(@Nonnull String expression, @Nonnull MutableInt position, @Nonnull final MathContext mathEngine) {
			return new Parameters(expression, position, mathEngine);
		}

		@Nonnull
		public String getExpression() {
			return expression;
		}

		@Nonnull
		public MutableInt getPosition() {
			return position;
		}

		public void addException(@Nonnull ParseException e) {
			if (!exceptions.contains(e)) {
				exceptions.add(e);
			}
		}

		@Nonnull
		public MathContext getMathContext() {
			return mathContext;
		}

		@Nonnull
		public List getExceptions() {
			return Collections.unmodifiableList(exceptions);
		}
	}
}