Slice.java

/*

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package com.google.refine.expr.functions;

import java.util.List;
import java.util.Properties;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONWriter;

import com.google.refine.expr.ExpressionUtils;
import com.google.refine.expr.HasFieldsList;
import com.google.refine.grel.Function;

public class Slice implements Function {

    @Override
    public Object call(Properties bindings, Object[] args) {
        if (args.length > 1 && args.length <= 3) {
            Object v = args[0];
            Object from = args[1];
            Object to = (args.length == 3) ? args[2] : null;
            
            if (v != null && from != null && from instanceof Number && (to == null || to instanceof Number)) {
                if (v.getClass().isArray() || v instanceof List<?> || v instanceof HasFieldsList || v instanceof JSONArray) {
                    int length = 0;
                    if (v.getClass().isArray()) { 
                        length = ((Object[]) v).length;
                    } else if (v instanceof HasFieldsList) {
                        length = ((HasFieldsList) v).length();
                    } else if (v instanceof JSONArray) {
                        length = ((JSONArray) v).length();
                    } else {
                        length = ExpressionUtils.toObjectList(v).size();
                    }
                    
                    int start = ((Number) from).intValue();
                    int end = (to != null) ? ((Number) to).intValue() : length;
                                
                    if (start < 0) {
                        start = length + start;
                    }
                    start = Math.min(length, Math.max(0, start));
                    
                    if (end < 0) {
                        end = length + end;
                    }
                    end = Math.min(length, Math.max(start, end));
                    
                    if (v.getClass().isArray()) {
                        Object[] a2 = new Object[end - start];
                        
                        System.arraycopy(v, start, a2, 0, end - start);
                        
                        return a2;
                    } else if (v instanceof HasFieldsList) {
                        return ((HasFieldsList) v).getSubList(start, end);
                    } else if (v instanceof JSONArray) {
                        JSONArray a = (JSONArray) v;
                        Object[] a2 = new Object[end - start];
                        
                        for (int i = 0; i < a2.length; i++) {
                            try {
                                a2[i] = a.get(start + i);
                            } catch (JSONException e) {
                                // ignore
                            }
                        }
                        
                        return a2;
                    } else {
                        return ExpressionUtils.toObjectList(v).subList(start, end);
                    }
                } else {
                    String s = (v instanceof String) ? (String) v : v.toString();
                    
                    int start = ((Number) from).intValue();
                    if (start < 0) {
                        start = s.length() + start;
                    }
                    start = Math.min(s.length(), Math.max(0, start));
                    
                    if (to != null) {
                        int end = ((Number) to).intValue();
                        if (end < 0) {
                            end = s.length() + end;
                        }
                        end = Math.min(s.length(), Math.max(start, end));
                        
                        return s.substring(start, end);
                    } else {
                        return s.substring(start);
                    }
                }
            }
        }
        return null;
    }

    @Override
    public void write(JSONWriter writer, Properties options)
        throws JSONException {
    
        writer.object();
        writer.key("description"); writer.value(
            "If o is an array, returns o[from, to]. " +
            "if o is a string, returns o.substring(from, to)"
        );
        writer.key("params"); writer.value("o, number from, optional number to");
        writer.key("returns"); writer.value("Depends on actual arguments");
        writer.endObject();
    }
}