package inventory

import (
	"errors"
	"strings"
	"testing"
	"time"
)

// Composing and sending one node's declaration is serialised: a second holder waits for the first.
func TestHoldingANodeMakesTheNextHolderWait(t *testing.T) {
	inv := fresh(t)
	ctx := t.Context()
	release, err := inv.HoldNodes(ctx, []string{"anchor", "laptop"})
	if err != nil {
		t.Fatal(err)
	}
	got := make(chan func(), 1)
	go func() {
		second, err := inv.HoldNodes(ctx, []string{"laptop"})
		if err != nil {
			t.Error(err)
			got <- func() {}
			return
		}
		got <- second
	}()
	select {
	case <-got:
		t.Fatal("a node held by one caller was held by another at the same time")
	case <-time.After(300 * time.Millisecond):
	}
	// Another node is not held up.
	other, err := inv.HoldNodes(ctx, []string{"joiner"})
	if err != nil {
		t.Fatal(err)
	}
	other()
	release()
	select {
	case second := <-got:
		second()
	case <-time.After(5 * time.Second):
		t.Fatal("releasing the node did not let the next holder in")
	}
}

// A waiter pins no pool connection while it waits, and gives up after a bounded wait saying which
// node is busy.
func TestAWaiterPinsNoConnectionAndGivesUp(t *testing.T) {
	inv := fresh(t)
	ctx := t.Context()
	release, err := inv.HoldNodes(ctx, []string{"anchor"})
	if err != nil {
		t.Fatal(err)
	}
	defer release()
	savedWait, savedPoll := HoldWaitFor, HoldPoll
	HoldWaitFor, HoldPoll = 1500*time.Millisecond, 50*time.Millisecond
	defer func() { HoldWaitFor, HoldPoll = savedWait, savedPoll }()

	pool := inv.store.Pool()
	base := pool.Stat().AcquiredConns()
	const waiters = 3
	done := make(chan error, waiters)
	for range waiters {
		go func() {
			_, err := inv.HoldNodes(ctx, []string{"anchor"})
			done <- err
		}()
	}
	// While they wait, the pool lends nothing to them for longer than a look.
	pinned := 0
	for range 10 {
		time.Sleep(60 * time.Millisecond)
		if n := int(pool.Stat().AcquiredConns() - base); n > pinned {
			pinned = n
		}
	}
	if pinned >= waiters {
		t.Fatalf("%d connections were held by %d waiters", pinned, waiters)
	}
	for range waiters {
		if err := <-done; !errors.Is(err, ErrNodeBusy) || !strings.Contains(err.Error(), "anchor") {
			t.Fatalf("a waiter did not give up naming the busy node: %v", err)
		}
	}
}