libhoney/dist/libhoney.browser.js

'use strict';

function _interopDefault (ex) { return (ex && (typeof ex === 'object') && 'default' in ex) ? ex['default'] : ex; }

var superagent = _interopDefault(require('superagent'));
var url = _interopDefault(require('url'));
var path = _interopDefault(require('path'));
var events = require('events');

var hasOwn = Object.prototype.hasOwnProperty;
var toStr = Object.prototype.toString;
var defineProperty = Object.defineProperty;
var gOPD = Object.getOwnPropertyDescriptor;

var isArray = function isArray(arr) {
	if (typeof Array.isArray === 'function') {
		return Array.isArray(arr);
	}

	return toStr.call(arr) === '[object Array]';
};

var isPlainObject = function isPlainObject(obj) {

	if (!obj || toStr.call(obj) !== '[object Object]') {
		return false;
	}

	var hasOwnConstructor = hasOwn.call(obj, 'constructor');
	var hasIsPrototypeOf = obj.constructor && obj.constructor.prototype && hasOwn.call(obj.constructor.prototype, 'isPrototypeOf');
	// Not own constructor property must be Object
	if (obj.constructor && !hasOwnConstructor && !hasIsPrototypeOf) {
		return false;
	}

	// Own properties are enumerated firstly, so to speed up,
	// if last one is own, then all properties are own.
	var key;
	for (key in obj) { /**/ }

	return typeof key === 'undefined' || hasOwn.call(obj, key);
};

// If name is '__proto__', and Object.defineProperty is available, define __proto__ as an own property on target
var setProperty = function setProperty(target, options) {
	if (defineProperty && options.name === '__proto__') {
		defineProperty(target, options.name, {
			enumerable: true,
			configurable: true,
			value: options.newValue,
			writable: true
		});
	} else {
		target[options.name] = options.newValue;
	}
};

// Return undefined instead of __proto__ if '__proto__' is not an own property
var getProperty = function getProperty(obj, name) {
	if (name === '__proto__') {
		if (!hasOwn.call(obj, name)) {
			return void 0;
		} else if (gOPD) {
			// In early versions of node, obj['__proto__'] is buggy when obj has
			// __proto__ as an own property. Object.getOwnPropertyDescriptor() works.
			return gOPD(obj, name).value;
		}
	}

	return obj[name];
};

var extend = function extend() {

	var options, name, src, copy, copyIsArray, clone;
	var target = arguments[0];
	var i = 1;
	var length = arguments.length;
	var deep = false;

	// Handle a deep copy situation
	if (typeof target === 'boolean') {
		deep = target;
		target = arguments[1] || {};
		// skip the boolean and the target
		i = 2;
	}
	if (target == null || (typeof target !== 'object' && typeof target !== 'function')) {
		target = {};
	}

	for (; i < length; ++i) {
		options = arguments[i];
		// Only deal with non-null/undefined values
		if (options != null) {
			// Extend the base object
			for (name in options) {
				src = getProperty(target, name);
				copy = getProperty(options, name);

				// Prevent never-ending loop
				if (target !== copy) {
					// Recurse if we're merging plain objects or arrays
					if (deep && copy && (isPlainObject(copy) || (copyIsArray = isArray(copy)))) {
						if (copyIsArray) {
							copyIsArray = false;
							clone = src && isArray(src) ? src : [];
						} else {
							clone = src && isPlainObject(src) ? src : {};
						}

						// Never move original objects, clone them
						setProperty(target, { name: name, newValue: extend(deep, clone, copy) });

					// Don't bring in undefined values
					} else if (typeof copy !== 'undefined') {
						setProperty(target, { name: name, newValue: copy });
					}
				}
			}
		}
	}

	// Return the modified object
	return target;
};

/**
 * Join two or more url pieces into one.
 *
 * Only the protocol/port/host in the first piece is saved,but all the get parameters
 * will be saved.
 *
 * @param {String|Function}... Multiple url pieces in function or string type.
 * @return {String} The URL joined.
 */
var urljoin = function urljoin() {

    //convert to Array
    var pieces = Array.prototype.slice.call(arguments);
    var query = {};
    var first, paths;

    if (!pieces.length) {
        return '';
    } else if (1 === pieces.length) {
        return pieces[0];
    }

    paths = pieces.map(function(piece) {
        var pieceStr = 'function' === typeof piece ? piece() : String(piece || '');

        if (!pieceStr) {
            return '';
        }

        var parsed = url.parse(pieceStr, true);

        if (!first && parsed) {
            first = parsed;
        }

        extend(query, parsed.query);
        return parsed.pathname;
    }).filter(function(piece) {
        return !!piece;
    });

    delete first.search; //we use query instead of search
    first.query = query;
    first.pathname = path.join.apply(path, paths).replace(new RegExp('\\' + path.sep, 'g'), '/');
    return url.format(first);
};

// Copyright 2016 Hound Technology, Inc. All rights reserved.

const USER_AGENT = "libhoney-js/2.1.0";

const _global =
  typeof window !== "undefined"
    ? window
    : typeof global !== "undefined"
    ? global
    : undefined;

// how many events to collect in a batch
const batchSizeTrigger = 50; // either when the eventQueue is > this length
const batchTimeTrigger = 100; // or it's been more than this many ms since the first push

// how many batches to maintain in parallel
const maxConcurrentBatches = 10;

// how many events to queue up for busy batches before we start dropping
const pendingWorkCapacity = 10000;

const emptyResponseCallback = function() {};

const eachPromise = (arr, iteratorFn) =>
  arr.reduce((p, item) => {
    return p.then(() => {
      return iteratorFn(item);
    });
  }, Promise.resolve());

const partition = (arr, keyfn, createfn, addfn) => {
  let result = Object.create(null);
  arr.forEach(v => {
    let key = keyfn(v);
    if (!result[key]) {
      result[key] = createfn(v);
    } else {
      addfn(result[key], v);
    }
  });
  return result;
};

class BatchEndpointAggregator {
  constructor(events) {
    this.batches = partition(
      events,
      /* keyfn */
      ev => `${ev.apiHost}_${ev.writeKey}_${ev.dataset}`,
      /* createfn */
      ev => ({
        apiHost: ev.apiHost,
        writeKey: ev.writeKey,
        dataset: ev.dataset,
        events: [ev]
      }),
      /* addfn */
      (batch, ev) => batch.events.push(ev)
    );
  }

  encodeBatchEvents(events) {
    let first = true;
    let numEncoded = 0;
    let encodedEvents = events.reduce((acc, ev) => {
      try {
        let encodedEvent = ev.toJSON(); // directly call toJSON, not JSON.stringify, because the latter wraps it in an additional set of quotes
        numEncoded++;
        let newAcc = acc + (!first ? "," : "") + encodedEvent;
        first = false;
        return newAcc;
      } catch (e) {
        ev.encodeError = e;
        return acc;
      }
    }, "");

    let encoded = "[" + encodedEvents + "]";
    return { encoded, numEncoded };
  }
}

/**
 * @private
 */
class ValidatedEvent {
  constructor({
    timestamp,
    apiHost,
    postData,
    writeKey,
    dataset,
    sampleRate,
    metadata
  }) {
    this.timestamp = timestamp;
    this.apiHost = apiHost;
    this.postData = postData;
    this.writeKey = writeKey;
    this.dataset = dataset;
    this.sampleRate = sampleRate;
    this.metadata = metadata;
  }

  toJSON() {
    let fields = [];
    if (this.timestamp) {
      fields.push(`"time":${JSON.stringify(this.timestamp)}`);
    }
    if (this.sampleRate) {
      fields.push(`"samplerate":${JSON.stringify(this.sampleRate)}`);
    }
    if (this.postData) {
      fields.push(`"data":${this.postData}`);
    }
    return `{${fields.join(",")}}`;
  }
}

class MockTransmission {
  constructor(options) {
    this.constructorArg = options;
    this.events = [];
  }

  sendEvent(ev) {
    this.events.push(ev);
  }

  sendPresampledEvent(ev) {
    this.events.push(ev);
  }

  reset() {
    this.constructorArg = null;
    this.events = [];
  }
}

class WriterTransmission {
  sendEvent(ev) {
    console.log(JSON.stringify(ev));
  }

  sendPresampledEvent(ev) {
    console.log(JSON.stringify(ev));
  }
}

class NullTransmission {
  sendEvent(_ev) {}

  sendPresampledEvent(_ev) {}
}

/**
 * @private
 */
class Transmission {
  constructor(options) {
    this._responseCallback = emptyResponseCallback;
    this._batchSizeTrigger = batchSizeTrigger;
    this._batchTimeTrigger = batchTimeTrigger;
    this._maxConcurrentBatches = maxConcurrentBatches;
    this._pendingWorkCapacity = pendingWorkCapacity;
    this._sendTimeoutId = -1;
    this._eventQueue = [];
    this._batchCount = 0;

    if (typeof options.responseCallback === "function") {
      this._responseCallback = options.responseCallback;
    }
    if (typeof options.batchSizeTrigger === "number") {
      this._batchSizeTrigger = Math.max(options.batchSizeTrigger, 1);
    }
    if (typeof options.batchTimeTrigger === "number") {
      this._batchTimeTrigger = options.batchTimeTrigger;
    }
    if (typeof options.maxConcurrentBatches === "number") {
      this._maxConcurrentBatches = options.maxConcurrentBatches;
    }
    if (typeof options.pendingWorkCapacity === "number") {
      this._pendingWorkCapacity = options.pendingWorkCapacity;
    }

    this._userAgentAddition = options.userAgentAddition || "";
    this._proxy = options.proxy;

    // Included for testing; to stub out randomness and verify that an event
    // was dropped.
    this._randomFn = Math.random;
  }

  _droppedCallback(ev, reason) {
    this._responseCallback([
      {
        metadata: ev.metadata,
        error: new Error(reason)
      }
    ]);
  }

  sendEvent(ev) {
    // bail early if we aren't sampling this event
    if (!this._shouldSendEvent(ev)) {
      this._droppedCallback(ev, "event dropped due to sampling");
      return;
    }

    this.sendPresampledEvent(ev);
  }

  sendPresampledEvent(ev) {
    if (this._eventQueue.length >= this._pendingWorkCapacity) {
      this._droppedCallback(ev, "queue overflow");
      return;
    }
    this._eventQueue.push(ev);
    if (this._eventQueue.length >= this._batchSizeTrigger) {
      this._sendBatch();
    } else {
      this._ensureSendTimeout();
    }
  }

  flush() {
    if (this._eventQueue.length === 0 && this._batchCount === 0) {
      // we're not currently waiting on anything, we're done!
      return Promise.resolve();
    }

    return new Promise(resolve => {
      this.flushCallback = () => {
        this.flushCallback = null;
        resolve();
      };
    });
  }

  _sendBatch() {
    if (this._batchCount === maxConcurrentBatches) {
      // don't start up another concurrent batch.  the next timeout/sendEvent or batch completion
      // will cause us to send another
      return;
    }

    this._clearSendTimeout();

    this._batchCount++;

    let batchAgg = new BatchEndpointAggregator(
      this._eventQueue.splice(0, this._batchSizeTrigger)
    );

    const finishBatch = () => {
      this._batchCount--;

      let queueLength = this._eventQueue.length;
      if (queueLength > 0) {
        if (queueLength >= this._batchSizeTrigger) {
          this._sendBatch();
        } else {
          this._ensureSendTimeout();
        }
        return;
      }

      if (this._batchCount === 0 && this.flushCallback) {
        this.flushCallback();
      }
    };

    let batches = Object.keys(batchAgg.batches).map(k => batchAgg.batches[k]);
    eachPromise(batches, batch => {
      let url = urljoin(batch.apiHost, "/1/batch", batch.dataset);
      let postReq = superagent.post(url);

      let reqPromise;
      {
        reqPromise = Promise.resolve({ req: postReq });
      }
      let { encoded, numEncoded } = batchAgg.encodeBatchEvents(batch.events);
      return reqPromise.then(
        ({ req }) =>
          new Promise(resolve => {
            // if we failed to encode any of the events, no point in sending anything to honeycomb
            if (numEncoded === 0) {
              this._responseCallback(
                batch.events.map(ev => ({
                  metadata: ev.metadata,
                  error: ev.encodeError
                }))
              );
              resolve();
              return;
            }

            let userAgent = USER_AGENT;
            let trimmedAddition = this._userAgentAddition.trim();
            if (trimmedAddition) {
              userAgent = `${USER_AGENT} ${trimmedAddition}`;
            }

            let start = Date.now();
            req
              .set("X-Honeycomb-Team", batch.writeKey)
              .set(
                 "X-Honeycomb-UserAgent"
                  ,
                userAgent
              )
              .type("json")
              .send(encoded)
              .end((err, res) => {
                let end = Date.now();

                if (err) {
                  this._responseCallback(
                    batch.events.map(ev => ({
                      // eslint-disable-next-line camelcase
                      status_code: ev.encodeError ? undefined : err.status,
                      duration: end - start,
                      metadata: ev.metadata,
                      error: ev.encodeError || err
                    }))
                  );
                } else {
                  let response = JSON.parse(res.text);
                  let respIdx = 0;
                  this._responseCallback(
                    batch.events.map(ev => {
                      if (ev.encodeError) {
                        return {
                          duration: end - start,
                          metadata: ev.metadata,
                          error: ev.encodeError
                        };
                      } else {
                        let nextResponse = response[respIdx++];
                        return {
                          // eslint-disable-next-line camelcase
                          status_code: nextResponse.status,
                          duration: end - start,
                          metadata: ev.metadata,
                          error: nextResponse.err
                        };
                      }
                    })
                  );
                }
                // we resolve unconditionally to continue the iteration in eachSeries.  errors will cause
                // the event to be re-enqueued/dropped.
                resolve();
              });
          })
      );
    })
      .then(finishBatch)
      .catch(finishBatch);
  }

  _shouldSendEvent(ev) {
    let { sampleRate } = ev;
    if (sampleRate <= 1) {
      return true;
    }
    return this._randomFn() < 1 / sampleRate;
  }

  _ensureSendTimeout() {
    if (this._sendTimeoutId === -1) {
      this._sendTimeoutId = _global.setTimeout(
        () => this._sendBatch(),
        this._batchTimeTrigger
      );
    }
  }

  _clearSendTimeout() {
    if (this._sendTimeoutId !== -1) {
      _global.clearTimeout(this._sendTimeoutId);
      this._sendTimeoutId = -1;
    }
  }
}

// Copyright 2016 Hound Technology, Inc. All rights reserved.
// Use of this source code is governed by the Apache License 2.0
// license that can be found in the LICENSE file.

/**
 * a simple function that offers the same interface
 * for both Map and object key interation.
 * @private
 */
function foreach(col, f) {
  if (!col) {
    return;
  }
  if (col instanceof Map) {
    col.forEach(f);
  } else {
    Object.getOwnPropertyNames(col).forEach(k => f(col[k], k));
  }
}

// Copyright 2016 Hound Technology, Inc. All rights reserved.

/**
 * Represents an individual event to send to Honeycomb.
 * @class
 */
class Event {
  /**
   * @constructor
   * private
   */
  constructor(libhoney, fields, dynFields) {
    this.data = Object.create(null);
    this.metadata = null;

    /**
     * The hostname for the Honeycomb API server to which to send this event.  default:
     * https://api.honeycomb.io/
     *
     * @type {string}
     */
    this.apiHost = "";
    /**
     * The Honeycomb authentication token for this event.  Find your team write key at
     * https://ui.honeycomb.io/account
     *
     * @type {string}
     */
    this.writeKey = "";
    /**
     * The name of the Honeycomb dataset to which to send this event.
     *
     * @type {string}
     */
    this.dataset = "";
    /**
     * The rate at which to sample this event.
     *
     * @type {number}
     */
    this.sampleRate = 1;

    /**
     * If set, specifies the timestamp associated with this event. If unset,
     * defaults to Date.now();
     *
     * @type {Date}
     */
    this.timestamp = null;

    foreach(fields, (v, k) => this.addField(k, v));
    foreach(dynFields, (v, k) => this.addField(k, v()));

    // stash this away for .send()
    this._libhoney = libhoney;
  }

  /**
   * adds a group of field->values to this event.
   * @param {Object|Map} data field->value mapping.
   * @returns {Event} this event.
   * @example <caption>using an object</caption>
   *   builder.newEvent()
   *     .add ({
   *       responseTime_ms: 100,
   *       httpStatusCode: 200
   *     })
   *     .send();
   * @example <caption>using an ES2015 map</caption>
   *   let map = new Map();
   *   map.set("responseTime_ms", 100);
   *   map.set("httpStatusCode", 200);
   *   let event = honey.newEvent();
   *   event.add (map);
   *   event.send();
   */
  add(data) {
    foreach(data, (v, k) => this.addField(k, v));
    return this;
  }

  /**
   * adds a single field->value mapping to this event.
   * @param {string} name
   * @param {any} val
   * @returns {Event} this event.
   * @example
   *   builder.newEvent()
   *     .addField("responseTime_ms", 100)
   *     .send();
   */
  addField(name, val) {
    if (val === undefined) {
      this.data[name] = null;
      return this;
    }
    this.data[name] = val;
    return this;
  }

  /**
   * attaches data to an event that is not transmitted to honeycomb, but instead is available when checking the send responses.
   * @param {any} md
   * @returns {Event} this event.
   */
  addMetadata(md) {
    this.metadata = md;
    return this;
  }

  /**
   * Sends this event to honeycomb, sampling if necessary.
   */
  send() {
    this._libhoney.sendEvent(this);
  }

  /**
   * Dispatch an event to be sent to Honeycomb.  Assumes sampling has already happened,
   * and will send every event handed to it.
   */
  sendPresampled() {
    this._libhoney.sendPresampledEvent(this);
  }
}

// Copyright 2016 Hound Technology, Inc. All rights reserved.

/**
 * Allows piecemeal creation of events.
 * @class
 */
class Builder {
  /**
   * @constructor
   * @private
   */
  constructor(libhoney, fields, dynFields) {
    this._libhoney = libhoney;
    this._fields = Object.create(null);
    this._dynFields = Object.create(null);

    /**
     * The hostname for the Honeycomb API server to which to send events created through this
     * builder.  default: https://api.honeycomb.io/
     *
     * @type {string}
     */
    this.apiHost = "";
    /**
     * The Honeycomb authentication token. If it is set on a libhoney instance it will be used as the
     * default write key for all events. If absent, it must be explicitly set on a Builder or
     * Event. Find your team write key at https://ui.honeycomb.io/account
     *
     * @type {string}
     */
    this.writeKey = "";
    /**
     * The name of the Honeycomb dataset to which to send these events.  If it is specified during
     * libhoney initialization, it will be used as the default dataset for all events. If absent,
     * dataset must be explicitly set on a builder or event.
     *
     * @type {string}
     */
    this.dataset = "";
    /**
     * The rate at which to sample events. Default is 1, meaning no sampling. If you want to send one
     * event out of every 250 times send() is called, you would specify 250 here.
     *
     * @type {number}
     */
    this.sampleRate = 1;

    foreach(fields, (v, k) => this.addField(k, v));
    foreach(dynFields, (v, k) => this.addDynamicField(k, v));
  }

  /**
   * adds a group of field->values to the events created from this builder.
   * @param {Object|Map<string, any>} data field->value mapping.
   * @returns {Builder} this Builder instance.
   * @example <caption>using an object</caption>
   *   var honey = new libhoney();
   *   var builder = honey.newBuilder();
   *   builder.add ({
   *     component: "web",
   *     depth: 200
   *   });
   * @example <caption>using an ES2015 map</caption>
   *   let map = new Map();
   *   map.set("component", "web");
   *   map.set("depth", 200);
   *   builder.add (map);
   */
  add(data) {
    foreach(data, (v, k) => this.addField(k, v));
    return this;
  }

  /**
   * adds a single field->value mapping to the events created from this builder.
   * @param {string} name
   * @param {any} val
   * @returns {Builder} this Builder instance.
   * @example
   *   builder.addField("component", "web");
   */
  addField(name, val) {
    if (val === undefined) {
      this._fields[name] = null;
      return this;
    }
    this._fields[name] = val;
    return this;
  }

  /**
   * adds a single field->dynamic value function, which is invoked to supply values when events are created from this builder.
   * @param {string} name the name of the field to add to events.
   * @param {function(): any} fn the function called to generate the value for this field.
   * @returns {Builder} this Builder instance.
   * @example
   *   builder.addDynamicField("process_heapUsed", () => process.memoryUsage().heapUsed);
   */
  addDynamicField(name, fn) {
    this._dynFields[name] = fn;
  }

  /**
   * creates and sends an event, including all builder fields/dynFields, as well as anything in the optional data parameter.
   * @param {Object|Map<string, any>} [data] field->value mapping to add to the event sent.
   * @example <caption>empty sendNow</caption>
   *   builder.sendNow(); // sends just the data that has been added via add/addField/addDynamicField.
   * @example <caption>adding data at send-time</caption>
   *   builder.sendNow({
   *     additionalField: value
   *   });
   */
  sendNow(data) {
    let ev = this.newEvent();
    ev.add(data);
    ev.send();
  }

  /**
   * creates and returns a new Event containing all fields/dynFields from this builder, that can be further fleshed out and sent on its own.
   * @returns {Event} an Event instance
   * @example <caption>adding data at send-time</caption>
   *   let ev = builder.newEvent();
   *   ev.addField("additionalField", value);
   *   ev.send();
   */
  newEvent() {
    let ev = new Event(this._libhoney, this._fields, this._dynFields);
    ev.apiHost = this.apiHost;
    ev.writeKey = this.writeKey;
    ev.dataset = this.dataset;
    ev.sampleRate = this.sampleRate;
    return ev;
  }

  /**
   * creates and returns a clone of this builder, merged with fields and dynFields passed as arguments.
   * @param {Object|Map<string, any>} fields a field->value mapping to merge into the new builder.
   * @param {Object|Map<string, any>} dynFields a field->dynamic function mapping to merge into the new builder.
   * @returns {Builder} a Builder instance
   * @example <caption>no additional fields/dyn_field</caption>
   *   let anotherBuilder = builder.newBuilder();
   * @example <caption>additional fields/dyn_field</caption>
   *   let anotherBuilder = builder.newBuilder({ requestId },
   *                                           {
   *                                             process_heapUsed: () => process.memoryUsage().heapUsed
   *                                           });
   */
  newBuilder(fields, dynFields) {
    let b = new Builder(this._libhoney, this._fields, this._dynFields);

    foreach(fields, (v, k) => b.addField(k, v));
    foreach(dynFields, (v, k) => b.addDynamicField(k, v));

    b.apiHost = this.apiHost;
    b.writeKey = this.writeKey;
    b.dataset = this.dataset;
    b.sampleRate = this.sampleRate;

    return b;
  }
}

// Copyright 2016 Hound Technology, Inc. All rights reserved.

const defaults = Object.freeze({
  apiHost: "https://api.honeycomb.io/",

  // http
  proxy: undefined,

  // sample rate of data.  causes us to send 1/sample-rate of events
  // i.e. `sampleRate: 10` means we only send 1/10th the events.
  sampleRate: 1,

  // transmission constructor, or a string to pick one of our builtin versions.
  // we fall back to the base impl if worker or a custom implementation throws on init.
  // string options available are:
  //  - "base": the default transmission implementation
  //  - "worker": a web-worker based transmission (not currently available, see https://github.com/honeycombio/libhoney-js/issues/22)
  //  - "mock": an implementation that accumulates all events sent
  //  - "writer": an implementation that logs to the console all events sent
  //  - "null": an implementation that does nothing
  transmission: "base",

  // batch triggers
  batchSizeTrigger: 50, // we send a batch to the api when we have this many outstanding events
  batchTimeTrigger: 100, // ... or after this many ms has passed.

  // batches are sent serially (one event at a time), so we allow multiple concurrent batches
  // to increase parallelism while sending.
  maxConcurrentBatches: 10,

  // the maximum number of pending events we allow in our to-be-batched-and-transmitted queue before dropping them.
  pendingWorkCapacity: 10000,

  // the maximum number of responses we enqueue before we begin dropping them.
  maxResponseQueueSize: 1000,

  // if this is set to true, all sending is disabled.  useful for disabling libhoney when testing
  disabled: false,

  // If this is non-empty, append it to the end of the User-Agent header.
  userAgentAddition: ""
});

/**
 * libhoney aims to make it as easy as possible to create events and send them on into Honeycomb.
 *
 * See https://honeycomb.io/docs for background on this library.
 * @class
 */
class Libhoney extends events.EventEmitter {
  /**
   * Constructs a libhoney context in order to configure default behavior,
   * though each of its members (`apiHost`, `writeKey`, `dataset`, and
   * `sampleRate`) may in fact be overridden on a specific Builder or Event.
   *
   * @param {Object} [opts] overrides for the defaults
   * @param {string} [opts.apiHost=https://api.honeycomb.io] - Server host to receive Honeycomb events.
   * @param {string} [opts.proxy] - The proxy to send events through.
   * @param {string} opts.writeKey - Write key for your Honeycomb team. (Required)
   * @param {string} opts.dataset - Name of the dataset that should contain this event. The dataset will be created for your team if it doesn't already exist.
   * @param {number} [opts.sampleRate=1] - Sample rate of data. If set, causes us to send 1/sampleRate of events and drop the rest.
   * @param {number} [opts.batchSizeTrigger=50] - We send a batch to the API when this many outstanding events exist in our event queue.
   * @param {number} [opts.batchTimeTrigger=100] - We send a batch to the API after this many milliseconds have passed.
   * @param {number} [opts.maxConcurrentBatches=10] - We process batches concurrently to increase parallelism while sending.
   * @param {number} [opts.pendingWorkCapacity=10000] - The maximum number of pending events we allow to accumulate in our sending queue before dropping them.
   * @param {number} [opts.maxResponseQueueSize=1000] - The maximum number of responses we enqueue before dropping them.
   * @param {boolean} [opts.disabled=false] - Disable transmission of events to the specified `apiHost`, particularly useful for testing or development.
   * @constructor
   * @example
   * import Libhoney from 'libhoney';
   * let honey = new Libhoney({
   *   writeKey: "YOUR_WRITE_KEY",
   *   dataset: "honeycomb-js-example",
   *   // disabled: true // uncomment when testing or in development
   * });
   */
  constructor(opts) {
    super();
    this._options = Object.assign(
      { responseCallback: this._responseCallback.bind(this) },
      defaults,
      opts
    );
    this._transmission = getAndInitTransmission(
      this._options.transmission,
      this._options
    );
    this._usable = this._transmission !== null;
    this._builder = new Builder(this);

    this._builder.apiHost = this._options.apiHost;
    this._builder.writeKey = this._options.writeKey;
    this._builder.dataset = this._options.dataset;
    this._builder.sampleRate = this._options.sampleRate;

    this._responseQueue = [];
  }

  _responseCallback(responses) {
    let queue = this._responseQueue;
    if (queue.length < this._options.maxResponseQueueSize) {
      this._responseQueue = this._responseQueue.concat(responses);
    }
    this.emit("response", this._responseQueue);
  }

  /**
   * The transmission implementation in use for this libhoney instance.  Useful when mocking libhoney (specify
   * "mock" for options.transmission, and use this field to get at the list of events sent through libhoney.)
   */
  get transmission() {
    return this._transmission;
  }

  /**
   * The hostname for the Honeycomb API server to which to send events created through this libhoney
   * instance. default: https://api.honeycomb.io/
   *
   * @type {string}
   */
  set apiHost(v) {
    this._builder.apiHost = v;
  }
  /**
   * The hostname for the Honeycomb API server to which to send events created through this libhoney
   * instance. default: https://api.honeycomb.io/
   *
   * @type {string}
   */
  get apiHost() {
    return this._builder.apiHost;
  }

  /**
   * The Honeycomb authentication token. If it is set on a libhoney instance it will be used as the
   * default write key for all events. If absent, it must be explicitly set on a Builder or
   * Event. Find your team write key at https://ui.honeycomb.io/account
   *
   * @type {string}
   */
  set writeKey(v) {
    this._builder.writeKey = v;
  }
  /**
   * The Honeycomb authentication token. If it is set on a libhoney instance it will be used as the
   * default write key for all events. If absent, it must be explicitly set on a Builder or
   * Event. Find your team write key at https://ui.honeycomb.io/account
   *
   * @type {string}
   */
  get writeKey() {
    return this._builder.writeKey;
  }

  /**
   * The name of the Honeycomb dataset to which to send events through this libhoney instance.  If
   * it is specified during libhoney initialization, it will be used as the default dataset for all
   * events. If absent, dataset must be explicitly set on a builder or event.
   *
   * @type {string}
   */
  set dataset(v) {
    this._builder.dataset = v;
  }
  /**
   * The name of the Honeycomb dataset to which to send these events through this libhoney instance.
   * If it is specified during libhoney initialization, it will be used as the default dataset for
   * all events. If absent, dataset must be explicitly set on a builder or event.
   *
   * @type {string}
   */
  get dataset() {
    return this._builder.dataset;
  }

  /**
   * The rate at which to sample events. Default is 1, meaning no sampling. If you want to send one
   * event out of every 250 times send() is called, you would specify 250 here.
   *
   * @type {number}
   */
  set sampleRate(v) {
    this._builder.sampleRate = v;
  }
  /**
   * The rate at which to sample events. Default is 1, meaning no sampling. If you want to send one
   * event out of every 250 times send() is called, you would specify 250 here.
   *
   * @type {number}
   */
  get sampleRate() {
    return this._builder.sampleRate;
  }

  /**
   *  sendEvent takes events of the following form:
   *
   * {
   *   data: a JSON-serializable object, keys become colums in Honeycomb
   *   timestamp [optional]: time for this event, defaults to now()
   *   writeKey [optional]: your team's write key.  overrides the libhoney instance's value.
   *   dataset [optional]: the data set name.  overrides the libhoney instance's value.
   *   sampleRate [optional]: cause us to send 1 out of sampleRate events.  overrides the libhoney instance's value.
   * }
   *
   * Sampling is done based on the supplied sampleRate, so events passed to this method might not
   * actually be sent to Honeycomb.
   * @private
   */
  sendEvent(event) {
    let transmitEvent = this.validateEvent(event);
    if (!transmitEvent) {
      return;
    }

    this._transmission.sendEvent(transmitEvent);
  }

  /**
   *  sendPresampledEvent takes events of the following form:
   *
   * {
   *   data: a JSON-serializable object, keys become colums in Honeycomb
   *   timestamp [optional]: time for this event, defaults to now()
   *   writeKey [optional]: your team's write key.  overrides the libhoney instance's value.
   *   dataset [optional]: the data set name.  overrides the libhoney instance's value.
   *   sampleRate: the rate this event has already been sampled.
   * }
   *
   * Sampling is presumed to have already been done (at the supplied sampledRate), so all events passed to this method
   * are sent to Honeycomb.
   * @private
   */
  sendPresampledEvent(event) {
    let transmitEvent = this.validateEvent(event);
    if (!transmitEvent) {
      return;
    }

    this._transmission.sendPresampledEvent(transmitEvent);
  }

  /**
   * validateEvent takes an event and validates its structure and contents.
   *
   * @returns {Object} the validated libhoney Event. May return undefined if
   *                   the event was invalid in some way or unable to be sent.
   * @private
   */
  validateEvent(event) {
    if (!this._usable) return null;

    let timestamp = event.timestamp || Date.now();
    if (typeof timestamp === "string" || typeof timestamp === "number")
      timestamp = new Date(timestamp);

    if (typeof event.data !== "object" || event.data === null) {
      console.error(".data must be an object");
      return null;
    }
    let postData;
    try {
      postData = JSON.stringify(event.data);
    } catch (e) {
      console.error("error converting event data to JSON: " + e);
      return null;
    }

    let apiHost = event.apiHost;
    if (typeof apiHost !== "string" || apiHost === "") {
      console.error(".apiHost must be a non-empty string");
      return null;
    }

    let writeKey = event.writeKey;
    if (typeof writeKey !== "string" || writeKey === "") {
      console.error(".writeKey must be a non-empty string");
      return null;
    }

    let dataset = event.dataset;
    if (typeof dataset !== "string" || dataset === "") {
      console.error(".dataset must be a non-empty string");
      return null;
    }

    let sampleRate = event.sampleRate;
    if (typeof sampleRate !== "number") {
      console.error(".sampleRate must be a number");
      return null;
    }

    let metadata = event.metadata;
    return new ValidatedEvent({
      timestamp,
      apiHost,
      postData,
      writeKey,
      dataset,
      sampleRate,
      metadata
    });
  }

  /**
   * adds a group of field->values to the global Builder.
   * @param {Object|Map<string, any>} data field->value mapping.
   * @returns {Libhoney} this libhoney instance.
   * @example <caption>using an object</caption>
   *   honey.add ({
   *     buildID: "a6cc38a1",
   *     env: "staging"
   *   });
   * @example <caption>using an ES2015 map</caption>
   *   let map = new Map();
   *   map.set("build_id", "a6cc38a1");
   *   map.set("env", "staging");
   *   honey.add (map);
   */
  add(data) {
    this._builder.add(data);
    return this;
  }

  /**
   * adds a single field->value mapping to the global Builder.
   * @param {string} name name of field to add.
   * @param {any} val value of field to add.
   * @returns {Libhoney} this libhoney instance.
   * @example
   *   honey.addField("build_id", "a6cc38a1");
   */
  addField(name, val) {
    this._builder.addField(name, val);
    return this;
  }

  /**
   * adds a single field->dynamic value function to the global Builder.
   * @param {string} name name of field to add.
   * @param {function(): any} fn function that will be called to generate the value whenever an event is created.
   * @returns {Libhoney} this libhoney instance.
   * @example
   *   honey.addDynamicField("process_heapUsed", () => process.memoryUsage().heapUsed);
   */
  addDynamicField(name, fn) {
    this._builder.addDynamicField(name, fn);
    return this;
  }

  /**
   * creates and sends an event, including all global builder fields/dynFields, as well as anything in the optional data parameter.
   * @param {Object|Map<string, any>} data field->value mapping.
   * @example <caption>using an object</caption>
   *   honey.sendNow ({
   *     responseTime_ms: 100,
   *     httpStatusCode: 200
   *   });
   * @example <caption>using an ES2015 map</caption>
   *   let map = new Map();
   *   map.set("responseTime_ms", 100);
   *   map.set("httpStatusCode", 200);
   *   honey.sendNow (map);
   */
  sendNow(data) {
    return this._builder.sendNow(data);
  }

  /**
   * creates and returns a new Event containing all fields/dynFields from the global Builder, that can be further fleshed out and sent on its own.
   * @returns {Event} an Event instance
   * @example <caption>adding data at send-time</caption>
   *   let ev = honey.newEvent();
   *   ev.addField("additionalField", value);
   *   ev.send();
   */
  newEvent() {
    return this._builder.newEvent();
  }

  /**
   * creates and returns a clone of the global Builder, merged with fields and dynFields passed as arguments.
   * @param {Object|Map<string, any>} fields a field->value mapping to merge into the new builder.
   * @param {Object|Map<string, any>} dynFields a field->dynamic function mapping to merge into the new builder.
   * @returns {Builder} a Builder instance
   * @example <caption>no additional fields/dyn_field</caption>
   *   let builder = honey.newBuilder();
   * @example <caption>additional fields/dyn_field</caption>
   *   let builder = honey.newBuilder({ requestId },
   *                                  {
   *                                    process_heapUsed: () => process.memoryUsage().heapUsed
   *                                  });
   */
  newBuilder(fields, dynFields) {
    return this._builder.newBuilder(fields, dynFields);
  }

  /**
   * Allows you to easily wait for everything to be sent to Honeycomb (and for responses to come back for
   * events). Also initializes a transmission instance for libhoney to use, so any events sent
   * after a call to flush will not be waited on.
   * @returns {Promise} a promise that will resolve when all currently enqueued events/batches are sent.
   */
  flush() {
    const transmission = this._transmission;

    this._transmission = getAndInitTransmission(
      this._options.transmission,
      this._options
    );

    return transmission.flush();
  }
}

const getTransmissionClass = transmissionClassName => {
  switch (transmissionClassName) {
    case "base":
      return Transmission;
    case "mock":
      return MockTransmission;
    case "null":
      return NullTransmission;
    case "worker":
      console.warn(
        "worker implementation not ready yet.  using base implementation"
      );
      return Transmission;
    case "writer":
      return WriterTransmission;
    default:
      throw new Error(
        `unknown transmission implementation "${transmissionClassName}".`
      );
  }
};

function getAndInitTransmission(transmission, options) {
  if (options.disabled) {
    return null;
  }

  if (typeof transmission === "string") {
    const transmissionClass = getTransmissionClass(transmission);
    return new transmissionClass(options);
  } else if (typeof transmission !== "function") {
    throw new Error(
      ".transmission must be one of 'base'/'worker'/'mock'/'writer'/'null' or a constructor."
    );
  }

  try {
    return new transmission(options);
  } catch (initialisationError) {
    if (transmission === Transmission) {
      throw new Error(
        "unable to initialize base transmission implementation.",
        initialisationError
      );
    }

    console.warn(
      "failed to initialize transmission, falling back to base implementation."
    );
    try {
      return new Transmission(options);
    } catch (fallbackInitialisationError) {
      throw new Error(
        "unable to initialize base transmission implementation.",
        fallbackInitialisationError
      );
    }
  }
}

module.exports = Libhoney;