package link

import (
	"context"
	"errors"
	"testing"
	"time"
)

type heardWith struct{ err error }

func (h heardWith) Heard(context.Context, Report) error { return h.err }

// switchable answers with whatever it is set to — the store away, then back.
type switchable struct{ err error }

func (h *switchable) Heard(context.Context, Report) error { return h.err }

func aReport(node, declared string) Report {
	return Report{Node: node, Declared: declared, Applied: []string{"store"}}
}

// A report the store could not take right now is held, unsettled, and recorded when the store is
// back; one the store answered no to is acknowledged; one recorded is acknowledged (issue 082, 083).
func TestAReportTheStoreCouldNotTakeIsHeldAndOneItRefusedIsNot(t *testing.T) {
	store := &switchable{err: errors.Join(ErrTryAgain, errors.New("starting up"))}
	s, in := serving()
	s.listener = store
	held := &settled{}
	s.act(context.Background(), in.sends(t, held, KindReport, aReport("anchor", "d1")))
	if !held.unsettled() || len(in.held) != 1 {
		t.Fatalf("a report the store could not take was not held: %+v, %d held", held, len(in.held))
	}
	store.err = nil
	in.retries(context.Background(), s)
	if !held.acked || len(in.held) != 0 {
		t.Fatalf("a held report was not recorded once the store was back: %+v, %d held", held, len(in.held))
	}

	refused := &settled{}
	s, in = serving()
	s.listener = heardWith{err: errors.New("a report named no node")}
	s.act(context.Background(), in.sends(t, refused, KindReport, aReport("anchor", "d1")))
	if !refused.acked || refused.nacked {
		t.Fatalf("a report the store answered no to was not acknowledged: %+v", refused)
	}
}

// A newer report from the same node supersedes one of its reports still held: recorded after the
// newer, the older would overwrite what the node is doing now.
func TestANewerReportSupersedesAHeldOneFromTheSameNode(t *testing.T) {
	s, in := serving()
	s.listener = heardWith{err: errors.Join(ErrTryAgain, errors.New("starting up"))}
	older, newer, other := &settled{}, &settled{}, &settled{}
	s.act(context.Background(), in.sends(t, older, KindReport, aReport("anchor", "d1")))
	s.act(context.Background(), in.sends(t, other, KindReport, aReport("laptop", "d7")))
	s.act(context.Background(), in.sends(t, newer, KindReport, aReport("anchor", "d2")))
	if !older.acked {
		t.Fatalf("the older report was not set aside by the newer: %+v", older)
	}
	if !newer.unsettled() || !other.unsettled() || len(in.held) != 2 {
		t.Fatalf("the newer report and another node's were not both held: newer %+v other %+v, %d held",
			newer, other, len(in.held))
	}
}

// A store that has not come back within the bound is not restarting: the report is let go, loudly,
// rather than held for ever.
func TestAReportIsLetGoOnceTheStoreHasBeenGoneTooLong(t *testing.T) {
	s, in := serving()
	s.listener = heardWith{err: errors.Join(ErrTryAgain, errors.New("connection refused"))}
	s.giveUp = time.Millisecond
	held := &settled{}
	s.act(context.Background(), in.sends(t, held, KindReport, aReport("anchor", "d1")))
	if !held.unsettled() {
		t.Fatalf("the first failure was not held: %+v", held)
	}
	time.Sleep(5 * time.Millisecond)
	in.retries(context.Background(), s)
	if !held.acked || len(in.held) != 0 {
		t.Fatalf("a report past the bound was not let go: %+v, %d held", held, len(in.held))
	}
}