// convert a JS array to a postgres array literal
// uses comma separator so won't work for types like box that use
// a different array separator.
function arrayString(val) {
  var result = '{';
  for (var i = 0 ; i < val.length; i++) {
    if(i > 0) {
      result = result + ',';
    }
    if(val[i] === null || typeof val[i] === 'undefined') {
      result = result + 'NULL';
    }
    else if(Array.isArray(val[i])) {
      result = result + arrayString(val[i]);
    }
    else
    {
      result = result + JSON.stringify(prepareValue(val[i]));
    }
  }
  result = result + '}';
  return result;
}

//converts values from javascript types
//to their 'raw' counterparts for use as a postgres parameter
//note: you can override this function to provide your own conversion mechanism
//for complex types, etc...
var prepareValue = function(val, seen) {
  if (val instanceof Buffer) {
    return val;
  }
  if(val instanceof Date) {
    return dateToString(val);
  }
  if(Array.isArray(val)) {
    return arrayString(val);
  }
  if(val === null || typeof val === 'undefined') {
    return null;
  }
  if(typeof val === 'object') {
    return prepareObject(val, seen);
  }
  return val.toString();
};

function prepareObject(val, seen) {
  if(val.toPostgres && typeof val.toPostgres === 'function') {
    seen = seen || [];
    if (seen.indexOf(val) !== -1) {
      throw new Error('circular reference detected while preparing "' + val + '" for query');
    }
    seen.push(val);

    return prepareValue(val.toPostgres(prepareValue), seen);
  }
  return JSON.stringify(val);
}

function dateToString(date) {
  function pad(number, digits) {
    number = ""+number;
    while(number.length < digits)
      number = "0"+number;
    return number;
  }

  var offset = -date.getTimezoneOffset();
  var ret = pad(date.getFullYear(), 4) + '-' +
    pad(date.getMonth() + 1, 2) + '-' +
    pad(date.getDate(), 2) + 'T' +
    pad(date.getHours(), 2) + ':' +
    pad(date.getMinutes(), 2) + ':' +
    pad(date.getSeconds(), 2) + '.' +
    pad(date.getMilliseconds(), 3);

  if(offset < 0) {
    ret += "-";
    offset *= -1;
  }
  else
    ret += "+";

  return ret + pad(Math.floor(offset/60), 2) + ":" + pad(offset%60, 2);
}

function normalizeQueryConfig (config, values, callback) {
  //can take in strings or config objects
  config = (typeof(config) == 'string') ? { text: config } : config;
  if(values) {
    if(typeof values === 'function') {
      config.callback = values;
    } else {
      config.values = values;
    }
  }
  if(callback) {
    config.callback = callback;
  }
  return config;
}

module.exports = {
  prepareValue: prepareValue,
  normalizeQueryConfig: normalizeQueryConfig
};