package buildstep

import (
	"context"
	"sync"
	"time"

	"git.novox.be/novox/mesh-sdk/go/delivery"
)

// FakeAsks is a test double of a seat's workers for the build modules' unit tests: Publish puts an ask on a kind's
// worker, Next hands them out in their order, and the fates the puller gives them are counted. Safe for concurrent use.
type FakeAsks struct {
	mu      sync.Mutex
	waiting map[string][][]byte
	added   chan struct{}
	// Acked, Termed and Naked are the asks' ids or data by fate, InProgress how many heartbeats were given.
	Acked, Termed, Naked []string
	InProgress           int
	// Delivered, when set, is the delivery count every ask handed over says (1 when 0): a test of a poisoned ask sets it.
	Delivered uint64
}

// NewFakeAsks is an empty double.
func NewFakeAsks() *FakeAsks {
	return &FakeAsks{waiting: map[string][][]byte{}, added: make(chan struct{}, 1)}
}

// Publish puts an encoded ask on kind's worker.
func (f *FakeAsks) Publish(kind string, data []byte) {
	f.mu.Lock()
	f.waiting[kind] = append(f.waiting[kind], data)
	f.mu.Unlock()
	select {
	case f.added <- struct{}{}:
	default:
	}
}

// PublishAsk encodes a and puts it on its kind's worker.
func (f *FakeAsks) PublishAsk(a delivery.StepAsk) error {
	raw, err := delivery.EncodeStepAsk(a)
	if err != nil {
		return err
	}
	f.Publish(a.Kind, raw)
	return nil
}

// Waiting is how many asks wait on kind's worker.
func (f *FakeAsks) Waiting(kind string) int {
	f.mu.Lock()
	defer f.mu.Unlock()
	return len(f.waiting[kind])
}

// Fates is a copy of the acked, termed and naked lists.
func (f *FakeAsks) Fates() (acked, termed, naked []string) {
	f.mu.Lock()
	defer f.mu.Unlock()
	return append([]string(nil), f.Acked...), append([]string(nil), f.Termed...), append([]string(nil), f.Naked...)
}

// Next is AskSource's.
func (f *FakeAsks) Next(ctx context.Context, kind string, wait time.Duration) (*Pulled, error) {
	var deadline <-chan time.Time
	if wait > 0 {
		t := time.NewTimer(wait)
		defer t.Stop()
		deadline = t.C
	}
	for {
		f.mu.Lock()
		if q := f.waiting[kind]; len(q) > 0 {
			data := q[0]
			f.waiting[kind] = q[1:]
			f.mu.Unlock()
			return f.pulled(data), nil
		}
		f.mu.Unlock()
		if wait <= 0 {
			return nil, nil
		}
		select {
		case <-ctx.Done():
			return nil, ctx.Err()
		case <-deadline:
			return nil, nil
		case <-f.added:
		}
	}
}

func (f *FakeAsks) pulled(data []byte) *Pulled {
	id := string(data)
	if a, err := delivery.DecodeStepAsk(data); err == nil {
		id = a.ID
	}
	fate := func(list *[]string) func() error {
		return func() error {
			f.mu.Lock()
			*list = append(*list, id)
			f.mu.Unlock()
			return nil
		}
	}
	delivered := f.Delivered
	if delivered == 0 {
		delivered = 1
	}
	return &Pulled{Data: data, Delivered: delivered, Ack: fate(&f.Acked), Nak: fate(&f.Naked), Term: fate(&f.Termed),
		InProgress: func() error { f.mu.Lock(); f.InProgress++; f.mu.Unlock(); return nil }}
}