package times

import (
	"sort"
	"time"
)

type clockState struct {
	current   time.Time
	chans     map[time.Time][]chan<- time.Time
	chantlist []time.Time
}

type test struct {
	state chan clockState
}

func makeTestClock(initial time.Time) test {
	s := make(chan clockState, 1)
	s <- clockState{
		current: initial,
		chans:   make(map[time.Time][]chan<- time.Time),
	}

	return test{state: s}
}

func triggerChans(s clockState) clockState {
	for len(s.chantlist) > 0 && !s.chantlist[0].After(s.current) {
		var ct time.Time
		ct, s.chantlist = s.chantlist[0], s.chantlist[1:]
		for _, c := range s.chans[ct] {
			c <- s.current
		}

		delete(s.chans, ct)
	}

	return s
}

func (t test) now() time.Time {
	s := <-t.state
	defer func() {
		t.state <- s
	}()

	return s.current
}

func (t test) after(d time.Duration) <-chan time.Time {
	s := <-t.state
	defer func() {
		t.state <- s
	}()

	c := make(chan time.Time, 1)
	ct := s.current.Add(d)
	if !ct.After(s.current) {
		c <- s.current
		return c
	}

	_, ctset := s.chans[ct]
	s.chans[ct] = append(s.chans[ct], c)
	if !ctset {
		s.chantlist = append(s.chantlist, ct)
		sort.Slice(s.chantlist, func(i, j int) bool {
			return s.chantlist[i].Before(s.chantlist[j])
		})
	}

	return c
}

func (t test) pass(d time.Duration) {
	s := <-t.state
	defer func() {
		t.state <- s
	}()

	if d < 0 {
		d = 0
	}

	s.current = s.current.Add(d)
	s = triggerChans(s)
}

func (t test) jump(to time.Time) {
	s := <-t.state
	defer func() {
		t.state <- s
	}()

	if to.Before(s.current) {
		return
	}

	s.current = to
	s = triggerChans(s)
}