import "../core/document";

import "../core/vendor";

var d3_timer_queueHead,

d3_timer_queueTail,

d3_timer_interval, // is an interval (or frame) active?

d3_timer_timeout, // is a timeout active?

d3_timer_active, // active timer object

d3_timer_frame = d3_window[d3_vendorSymbol(d3_window, "requestAnimationFrame")] || function(callback) { setTimeout(callback, 17); };

// The timer will continue to fire until callback returns true.

d3.timer = function(callback, delay, then) {

var n = arguments.length;

if (n < 2) delay = 0;

if (n < 3) then = Date.now();

// Add the callback to the tail of the queue.

var time = then + delay, timer = {callback: callback, time: time, next: null};

if (d3_timer_queueTail) d3_timer_queueTail.next = timer;

else d3_timer_queueHead = timer;

d3_timer_queueTail = timer;

// Start animatin'!

if (!d3_timer_interval) {

d3_timer_timeout = clearTimeout(d3_timer_timeout);

d3_timer_interval = 1;

d3_timer_frame(d3_timer_step);

}

};

function d3_timer_step() {

var now = d3_timer_mark(),

delay = d3_timer_sweep() - now;

if (delay > 24) {

if (isFinite(delay)) {

clearTimeout(d3_timer_timeout);

d3_timer_timeout = setTimeout(d3_timer_step, delay);

}

d3_timer_interval = 0;

} else {

d3_timer_interval = 1;

d3_timer_frame(d3_timer_step);

}

}

d3.timer.flush = function() {

d3_timer_mark();

d3_timer_sweep();

};

function d3_timer_replace(callback, delay, then) {

var n = arguments.length;

if (n < 2) delay = 0;

if (n < 3) then = Date.now();

d3_timer_active.callback = callback;

d3_timer_active.time = then + delay;

}

function d3_timer_mark() {

var now = Date.now();

d3_timer_active = d3_timer_queueHead;

while (d3_timer_active) {

if (now >= d3_timer_active.time) d3_timer_active.flush = d3_timer_active.callback(now - d3_timer_active.time);

d3_timer_active = d3_timer_active.next;

}

return now;

}

// Flush after callbacks to avoid concurrent queue modification.

// Returns the time of the earliest active timer, post-sweep.

function d3_timer_sweep() {

var t0,

t1 = d3_timer_queueHead,

time = Infinity;

while (t1) {

if (t1.flush) {

t1 = t0 ? t0.next = t1.next : d3_timer_queueHead = t1.next;

} else {

if (t1.time < time) time = t1.time;

t1 = (t0 = t1).next;

}

}

d3_timer_queueTail = t0;

return time;

}