package com.semmle.js.ast;

import com.semmle.jcorn.TokenType;
import com.semmle.ts.ast.ITypeExpression;

/**
 * A literal constant.
 * <p>
 * A <tt>null</tt> literal may occur as a TypeScript type annotation - other
 * literals are always expressions.
 */
public class Literal extends Expression implements ITypeExpression {
	private final TokenType tokenType;
	private final Object value;
	private final String raw;

	public Literal(SourceLocation loc, TokenType tokenType, Object value) {
		super("Literal", loc);

		// for numbers, check whether they can be represented as integers
		if (value instanceof Double) {
			Double dvalue = (Double)value;
			if (dvalue >= Long.MIN_VALUE && dvalue <= Long.MAX_VALUE && (dvalue%1) == 0)
				value = dvalue.longValue();
		} else if (value instanceof CharSequence) {
			value = value.toString();
		}

		this.tokenType = tokenType;
		this.value = value;
		this.raw = getLoc().getSource();
	}

	@Override
	public <Q, A> A accept(Visitor<Q, A> v, Q q) {
		return v.visit(this, q);
	}

	/**
	 * The type of the token corresponding to this literal.
	 */
	public TokenType getTokenType() {
		return tokenType;
	}

	/**
	 * The value of this literal; may be null if this is a null literal or a literal whose value
	 * cannot be represented by the parser.
	 */
	public Object getValue() {
		return value;
	}

	/**
	 * The source text of this literal.
	 */
	public String getRaw() {
		return raw;
	}

	/**
	 * Is this a regular expression literal?
	 */
	public boolean isRegExp() {
		return tokenType == TokenType.regexp;
	}

	/**
	 * The value of this literal expressed as a string.
	 */
	public String getStringValue() {
		// regular expressions may have a null value; use the raw value instead
		if (isRegExp())
			return raw;
		return String.valueOf(value);
	}

	/**
	 * Is the value of this literal falsy?
	 */
	public boolean isFalsy() {
		if (isRegExp())
			return false;
		return value == null ||
				value instanceof Number && ((Number)value).intValue() == 0 ||
				value == Boolean.FALSE ||
				value instanceof String && ((String)value).isEmpty();
	}

	/**
	 * Is the value of this literal truthy?
	 */
	public boolean isTruthy() {
		return !isFalsy();
	}
}