package buildrun

import (
	"bytes"
	"context"
	"errors"
	"log"
	"strings"
	"testing"
	"time"

	"github.com/nats-io/nats.go/jetstream"

	"git.novox.be/novox/mesh-contracts/go/clients/meshmoduleassignerclient"
	"git.novox.be/novox/mesh-contracts/go/seats/meshmoduleassigner"
	meshwants "git.novox.be/novox/mesh-delivery/modules/mesh-delivery-contracts/go/seats/meshwants"
)

// placing is a value of the state `assignments` placing modules on node.
func placing(t *testing.T, node string, modules ...string) (string, []byte) {
	t.Helper()
	p := meshmoduleassigner.Assignments{Node: node}
	for _, m := range modules {
		p.Modules = append(p.Modules, meshmoduleassigner.PlacedModule{Module: m})
	}
	values, err := meshmoduleassignerclient.AssignmentsValues(p)
	if err != nil {
		t.Fatal(err)
	}
	key, _ := meshmoduleassignerclient.NodeKey(node)
	return key, values[key]
}

// The placements the builder counts nodes by (ADR 0624 §1): a settled assignments names the nodes its modules stand on, a
// revision of the assignment half the same; they hold no toolchain (design 47 G §546: a toolchain is forgotten on the
// node-engine seat's stopped, never on a placement).
func TestPlacedNodes(t *testing.T) {
	old := time.Date(2026, 10, 23, 6, 29, 18, 0, time.UTC)
	three := []string{"g14", "novox", "shanks"}

	t.Run("the assignments names the counted nodes once it is settled", func(t *testing.T) {
		gate := NewPlacedNodes(func(string, ...any) {})
		for _, node := range three {
			k, v := placing(t, node, testNode)
			if gate.Assignments(k, v, false, old) {
				t.Fatal("an assignments before it is settled changed the counted nodes")
			}
		}
		gate.Settled()
		if got := strings.Join(gate.Nodes(), ","); got != "g14,novox,shanks" {
			t.Fatalf("nodes = %q", got)
		}
		k, v := placing(t, "ace", testGo)
		if !gate.Assignments(k, v, false, old) || len(gate.Nodes()) != 4 {
			t.Fatalf("ace placed: nodes %v", gate.Nodes())
		}
		if !gate.Assignments(k, nil, true, old.Add(time.Hour)) || len(gate.Nodes()) != 3 {
			t.Fatalf("ace's assignments deleted: nodes %v", gate.Nodes())
		}
	})

	t.Run("the assignment half: the first revision settles, a later one moves the nodes", func(t *testing.T) {
		gate := NewPlacedNodes(func(string, ...any) {})
		revision := func(n int64, nodes ...string) meshwants.AssignmentRevision {
			at := old.Add(time.Duration(n) * time.Hour)
			r := meshwants.AssignmentRevision{Revision: n, Kind: "trunk", At: &at}
			for _, node := range nodes {
				r.Entries = append(r.Entries, meshwants.NodeEntryRef{Node: node, Module: testNode, Digest: "d-" + node})
			}
			return r
		}
		if !gate.Revision(revision(7, three...)) || len(gate.Nodes()) != 3 {
			t.Fatalf("the first revision: nodes %v", gate.Nodes())
		}
		if gate.Revision(revision(7, three...)) {
			t.Fatal("the same revision again changed the counted nodes")
		}
		if !gate.Revision(revision(9, "novox", "shanks")) || len(gate.Nodes()) != 2 {
			t.Fatalf("g14 taken off: nodes %v", gate.Nodes())
		}
	})

	t.Run("assignments the bus refuses is said, and the part goes on", func(t *testing.T) {
		var logs bytes.Buffer
		logger := log.New(&logs, "", 0)
		refused := errors.New("nats: permissions violation for publish to $JS.API.CONSUMER.CREATE.KV_mesh-delivery-assigner_assignments")
		gate := NewPlacedNodes(logger.Printf)
		for _, bus := range []refusingBus{{err: refused}, {refuseOpen: true, err: refused}} {
			if _, err := FollowAssignmentsIn(context.Background(), bus, "acme-assigner_assignments", gate, func(context.Context) {}, logger.Printf); err != nil {
				t.Errorf("a refused assignments stopped the start: %v", err)
			}
		}
		if !strings.Contains(logs.String(), "cannot be watched") || !strings.Contains(logs.String(), "cannot be read") {
			t.Errorf("the refusals were not said: %q", logs.String())
		}
	})
}

// refusingBus is a bus that refuses: every open (refuseOpen), or every watch of a bucket it opens, with err.
type refusingBus struct {
	refuseOpen bool
	err        error
}

func (r refusingBus) KeyValue(context.Context, string) (jetstream.KeyValue, error) {
	if r.refuseOpen {
		return nil, r.err
	}
	return refusedWatch{err: r.err}, nil
}

type refusedWatch struct {
	jetstream.KeyValue
	err error
}

func (r refusedWatch) WatchAll(context.Context, ...jetstream.WatchOpt) (jetstream.KeyWatcher, error) {
	return nil, r.err
}