Google docs script for scraping eve data from eve-central.com

gistfile1.txt

// I hereby release this code to the public domain.

// Substitutes for placeholders in a string.
// Ex. sub("I am a {0} monkey.", "silly") -> "I am a silly monkey."
function sub(s) {
  var args = arguments;
  return s.replace(/{(\d+)}/g, function(match, number) { 
    var n = parseInt(number);
    return typeof args[n+1] != 'undefined'
    ? args[n+1]
    : match;
  });
};

// obj must contain properties "type_id" and "system_id". Fills obj with
// various other properties from eve-central, and enters it into the
// cache.
//
// In:
// type_id: The Eve item's type id.
// system_id: The system you want to collect data about.
//
// Out:
// buy: Data about buy orders in the system.
// sell: Data about sell orders in the system.
function getItemData(obj) {
  var obj = getOrCreate(obj);
  if (obj.last_update != null &&
      (new Date().getTime() - obj.last_update) < 12 * 60 * 60 * 1000) {
    return obj;
  }
  
  obj.last_update = new Date().getTime();
  try {
    obj = eveCentralUpdate(obj);
    save(obj);
  } catch (e) {
    Logger.log(e);
  }
}

// Get the buy data from type and system as an array. You can use this as
// a custom function in a spreadsheet cell.
function buyData(type_id, system_id) {
  return toArray(getItemData({type_id: type_id, system_id: system_id}).buy);
}
// The same, but for sell data.
function sellData(type_id, system_id) {
  return toArray(getItemData({type_id: type_id, system_id: system_id}).sell);
}

// Reformat a buy or sell tuple into an array.
function toArray(m) {
  return [m.volume, m.min, m.avg, m.max];
}

function test() {
  Logger.log(buyData(34, 30000142));
}

// Ask eve-central.com about obj, using its type_id and system_id properties.
function eveCentralUpdate(obj) {
  var resp = UrlFetchApp.fetch(sub("http://api.eve-central.com/api/marketstat?typeid={0}&systemlimit={1}", obj.type_id, obj.system_id)); 
  var orders = XmlService.parse(resp.getContentText()).getRootElement().getChild("marketstat").getChild("type");
  obj.buy = orderDict(orders.getChild("buy"));
  obj.sell = orderDict(orders.getChild("sell"));
  return obj;
}

function eveCentralTest() {
  Logger.log(getItemData({type_id: 34, system_id: 30002659}));
}

// Return a dictionary of order data from order xml in the eve-central.com response.
function orderDict(order_xml) {
  return {volume: fieldNum(order_xml, "volume"),
          avg: fieldNum(order_xml, "avg"),
          min: fieldNum(order_xml, "min"),
          max: fieldNum(order_xml, "max"),
          percentile: fieldNum(order_xml, "percentile")};
}

// Get the number inside of a named field in order_xml.
function fieldNum(order_xml, field) {
  return parseFloat(order_xml.getChild(field).getText());
}

// Get or create an object in the script database (a Google Docs-specific
// service). The existing properties of query are considered the keys
// of the query.
function getOrCreate(query) {
  var res = queryExpectingOne(query);
  if (res == null) {
    return query;
  }
  return res;
}

// Issue a query and return the first object in the cursor.
function queryExpectingOne(obj) {
  var db = ScriptDb.getMyDb();
  var iter = db.query(obj);
  if (iter.hasNext()) {
    return iter.next(); 
  } else {
    return null; 
  }
}

// Store obj in the ScriptDb.
function save(obj) {
  var db = ScriptDb.getMyDb(); 
  db.save(obj);
}