SumFilter.java

package com.hubspot.jinjava.lib.filter;

import java.math.BigDecimal;
import java.util.Map;
import java.util.Objects;

import com.hubspot.jinjava.doc.annotations.JinjavaDoc;
import com.hubspot.jinjava.doc.annotations.JinjavaParam;
import com.hubspot.jinjava.doc.annotations.JinjavaSnippet;
import com.hubspot.jinjava.interpret.JinjavaInterpreter;
import com.hubspot.jinjava.util.ForLoop;
import com.hubspot.jinjava.util.ObjectIterator;

@JinjavaDoc(
    value = "Returns the sum of a sequence of numbers plus the value of parameter ‘start’ (which defaults to 0). When the sequence is empty it returns start.",
    params = {
        @JinjavaParam(value = "value", type = "iterable", desc = "Selects the sequence or dict to sum values from"),
        @JinjavaParam(value = "attribute", desc = "Specify an optional attribute of dict to sum"),
        @JinjavaParam(value = "start", type = "number", defaultValue = "0", desc = "Sets a value to return, if there is nothing in the variable to sum")
    },
    snippets = {
        @JinjavaSnippet(
            code = "{% set sum_this = [1, 2, 3, 4, 5] %}\n" +
                "{{ sum_this|sum }}\n"),
        @JinjavaSnippet(
            desc = "Sum up only certain attributes",
            code = "Total: {{ items|sum(attribute='price') }}")
    })
public class SumFilter implements AdvancedFilter {

  @Override
  public String getName() {
    return "sum";
  }

  @Override
  public Object filter(Object var, JinjavaInterpreter interpreter, Object[] args, Map<String, Object> kwargs) {
    ForLoop loop = ObjectIterator.getLoop(var);

    BigDecimal sum = BigDecimal.ZERO;
    String attr = kwargs.containsKey("attribute") ? kwargs.get("attribute").toString() : null;

    if (args.length > 0) {
      try {
        sum = sum.add(new BigDecimal(args[0].toString()));
      } catch (NumberFormatException e) {
      }
    }

    while (loop.hasNext()) {
      Object val = loop.next();
      if (val == null) {
        continue;
      }

      BigDecimal addend = BigDecimal.ZERO;

      if (attr != null) {
        val = interpreter.resolveProperty(val, attr);
      }

      try {
        if (Number.class.isAssignableFrom(val.getClass())) {
          addend = new BigDecimal(((Number) val).doubleValue());
        }
        else {
          addend = new BigDecimal(Objects.toString(val, "0"));
        }
      } catch (NumberFormatException e) {
      }

      sum = sum.add(addend);
    }

    return sum;
  }

}