package buildstep

import (
	"context"
	"encoding/json"
	"errors"
	"sync"
	"testing"
	"time"

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

// keys is a steps state in memory: every value put, in order, per key, and a signal for each end.
type keys struct {
	mu    sync.Mutex
	puts  map[string][]delivery.Step
	ended chan string
}

func newKeys() *keys { return &keys{puts: map[string][]delivery.Step{}, ended: make(chan string, 16)} }

func (k *keys) put(key string, value any) (uint64, error) {
	step, err := delivery.DecodeStep(value.(json.RawMessage))
	if err != nil {
		return 0, err
	}
	k.mu.Lock()
	k.puts[key] = append(k.puts[key], step)
	n := uint64(len(k.puts[key]))
	k.mu.Unlock()
	if step.State != delivery.StepRunning {
		k.ended <- key
	}
	return n, nil
}

func (k *keys) last(key string) delivery.Step {
	k.mu.Lock()
	defer k.mu.Unlock()
	s := k.puts[key]
	return s[len(s)-1]
}

func (k *keys) waitEnd(t *testing.T) string {
	t.Helper()
	select {
	case key := <-k.ended:
		return key
	case <-time.After(3 * time.Second):
		t.Fatal("the step never ended on its key")
		return ""
	}
}

// 1471/AC1: a run that blocks: Start answers an id within 100 ms and the key holds running.
func TestStartAnswersAtOnceWithTheStepRunning(t *testing.T) {
	k := newKeys()
	release := make(chan struct{})
	defer close(release)
	began := time.Now()
	id, err := Start(context.Background(), k.put, "ace", "fetch", func(ctx context.Context) (any, error) {
		<-release
		return nil, nil
	})
	if err != nil {
		t.Fatal(err)
	}
	if d := time.Since(began); d > 100*time.Millisecond {
		t.Errorf("Start took %v", d)
	}
	s := k.last("ace." + id)
	if s.State != delivery.StepRunning || s.Tool != "fetch" || s.Node != "ace" || s.ID != id || s.Started.IsZero() {
		t.Errorf("step = %+v", s)
	}
}

// 1471/AC2 and 1473/AC4: a result, an error and a Refusal end the step passed, failed and refused.
func TestStepEndsPassedFailedOrRefusedOnItsKey(t *testing.T) {
	for _, c := range []struct {
		name   string
		run    func(context.Context) (any, error)
		state  string
		reason string
		result string
	}{
		{"result", func(context.Context) (any, error) { return map[string]string{"sha": "abc"}, nil }, delivery.StepPassed, "", `{"sha":"abc"}`},
		{"error", func(context.Context) (any, error) { return nil, errors.New("exit 2") }, delivery.StepFailed, "exit 2", ""},
		{"refusal", func(context.Context) (any, error) {
			return nil, &Refusal{Text: "go 1.27.1 installed, the recipe builds with go 1.27.0", Want: "1.27.0", Have: "1.27.1"}
		}, delivery.StepRefused, "go 1.27.1 installed, the recipe builds with go 1.27.0", ""},
	} {
		t.Run(c.name, func(t *testing.T) {
			k := newKeys()
			id, err := Start(context.Background(), k.put, "ace", "test", c.run)
			if err != nil {
				t.Fatal(err)
			}
			if got := k.waitEnd(t); got != "ace."+id {
				t.Fatalf("ended key %q", got)
			}
			s := k.last("ace." + id)
			if s.State != c.state || s.Reason != c.reason || string(s.Result) != c.result || s.Ended.IsZero() {
				t.Errorf("step = %+v", s)
			}
		})
	}
}

// 1471/AC3: a panic in run ends the step failed, naming it, and the test process goes on.
func TestAPanicEndsTheStepFailed(t *testing.T) {
	k := newKeys()
	id, _ := Start(context.Background(), k.put, "ace", "build", func(context.Context) (any, error) { panic("boom") })
	k.waitEnd(t)
	s := k.last("ace." + id)
	if s.State != delivery.StepFailed || s.Reason != "the step panicked: boom" {
		t.Errorf("step = %+v", s)
	}
}

// 1471/AC5: ids made in one and the same millisecond differ, and each is one key token. The clock is fixed
// while no step runs, so no goroutine reads it meanwhile.
func TestTwoIDsInOneMillisecondDiffer(t *testing.T) {
	was := now
	defer func() { now = was }()
	at := time.Date(2026, 10, 20, 12, 0, 0, 0, time.UTC)
	now = func() time.Time { return at }
	seen := map[string]bool{}
	for i := 0; i < 50; i++ {
		id := NewID()
		if seen[id] {
			t.Fatalf("id %q handed out twice", id)
		}
		seen[id] = true
		if _, err := delivery.StepKey("ace", id); err != nil {
			t.Errorf("id %q: %v", id, err)
		}
	}
}

// A first write that fails starts nothing.
func TestStartAnswersTheErrorWhenTheRunningWriteFails(t *testing.T) {
	ran := make(chan struct{}, 1)
	_, err := Start(context.Background(), func(string, any) (uint64, error) { return 0, errors.New("no grant") }, "ace", "fetch",
		func(context.Context) (any, error) { ran <- struct{}{}; return nil, nil })
	if err == nil {
		t.Fatal("Start answered no error")
	}
	select {
	case <-ran:
		t.Error("run was called")
	case <-time.After(50 * time.Millisecond):
	}
}