package de.jplag;

/**
 * This class represents a token in a source code. It can represent keywords, identifiers, syntactical structures etc.
 * What types of tokens there are depends on the specific language, meaning JPlag does not enforce a specific token set.
 * The language parsers decide what is a token and what is not.
 */
public abstract class Token {
    /** Indicates that the requested field has no value. */
    public static final int NO_VALUE = -1;

    private int line;
    private int column;
    private int length;
    private String file;

    protected int type;

    /**
     * Creates a token without information about the column or the length of the token in the line.
     * @param type is the token type.
     * @param file is the name of the source code file.
     * @param line is the line index in the source code where the token resides. Cannot be smaller than 1. For
     * {@link TokenConstants#FILE_END FILE_END} it is automatically set to {@link #NO_VALUE}.
     */
    public Token(int type, String file, int line) {
        this.type = type;
        this.file = file;
        if (type == TokenConstants.FILE_END) {
            this.line = NO_VALUE;
        } else {
            this.line = line > 0 ? line : 1;
        }
    }

    /**
     * Creates a token with column and length information.
     * @param type is the token type.
     * @param file is the name of the source code file.
     * @param line is the line index in the source code where the token resides. Cannot be smaller than 1.
     * @param column is the column index, meaning where the token starts in the line.
     * @param length is the length of the token in the source code.
     */
    public Token(int type, String file, int line, int column, int length) {
        this(type, file, line);
        this.column = column;
        this.length = length;
    }

    /**
     * Returns the character index which denotes where the code sections represented by this token starts in the line.
     * @return the character index in the line.
     */
    public int getColumn() {
        return column;
    }

    /**
     * @return the name of the file where the source code that the token represents is located in.
     */
    public String getFile() {
        return file;
    }

    /**
     * Gives the length if the code sections represented by this token.
     * @return the length in characters.
     */
    public int getLength() {
        return length;
    }

    /**
     * Gives the line index denoting in which line the code sections represented by this token starts.
     * @return the line index.
     */
    public int getLine() {
        return line;
    }

    /**
     * @return the type identifier of the token.
     */
    public int getType() {
        return type;
    }

    /**
     * Sets the character index which denotes where the code sections represented by this token starts in the line.
     * @param column is the index in characters to set.
     */
    public void setColumn(int column) {
        this.column = column;
    }

    @Override
    public String toString() {
        return type2string();
    }

    /**
     * @return a string representation depending on the type of the token.
     */
    protected abstract String type2string();
}