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package org.yamcs.xtce;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;

/**
 * Describes an element from an aggregate/array member access path For example, the third element from this path : 

 * a/c[2]/d[0][5]/x 

 * is: 

 * name = "d"

 * index = [0, 5]
 * 
 * both name and index can be null
 */
public class PathElement implements Serializable {
    private static final long serialVersionUID = 1L;

    final String name;
    final int[] index;

    public PathElement(String name, int[] index) {
        this.name = name;
        this.index = index;
    }

    /**
     * Encodes the path element into a string like
     * 
     * 
     * name[idx_1][idx_2]..[idx_n]
     * 
     */
    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder();
        if (name != null) {
            sb.append(name);
        }
        if (index != null) {
            for (int i = 0; i < index.length; i++) {
                sb.append("[").append(index[i]).append("]");
            }
        }
        return sb.toString();
    }

    /**
     * Creates a path element from a string like
     * 
     *      * name[idx_1][idx_2]..[idx_n]
     * 
     */
    public static PathElement fromString(String s) {
        List idx = new ArrayList<>();
        int k = s.indexOf('[', 0);
        if (k == -1) {
            return new PathElement(s, null);
        }

        String name = k > 0 ? s.substring(0, k) : null;

        while (true) {
            k = s.indexOf('[', k);
            if (k == -1) {
                break;
            }
            int k2 = s.indexOf(']', k);
            if (k2 == -1) {
                throw new IllegalArgumentException("Invalid aggregate member path '" + s + "'");
            }
            int n = Integer.parseInt(s.substring(k + 1, k2));
            if (n < 0) {
                throw new IllegalArgumentException("Negative array index: " + n);
            }
            idx.add(n);
            k = k2;
        }
        int[] idx1 = null;
        if (!idx.isEmpty()) {
            idx1 = new int[idx.size()];
            for (int u = 0; u < idx.size(); u++) {
                idx1[u] = idx.get(u);
            }
        }

        return new PathElement(name, idx1);
    }

    public String getName() {
        return name;
    }

    public int[] getIndex() {
        return index;
    }

    /**
     * Transforms the path into a string like

     * a/c[2]/d[0][5]/x 

     * 
     * @param path
     * @return
     */
    public static String pathToString(PathElement[] path) {
        if (path == null) {
            return "null";
        }
        StringBuilder sb = new StringBuilder();
        boolean first = true;
        for (PathElement pe : path) {
            if (first) {
                first = false;
            } else {
                sb.append("/");
            }
            sb.append(pe.toString());
        }
        return sb.toString();
    }
}