package skillpack

import (
	"context"
	"fmt"
	"testing"
	"time"
)

// fakeSource returns a caller-controlled tree, so sync behavior is tested with
// no filesystem or git.
type fakeSource struct {
	tree Tree
	ref  string
	err  error
}

func (f *fakeSource) Fetch(context.Context, string) (Tree, string, error) {
	return f.tree, f.ref, f.err
}
func (f *fakeSource) Kind() string   { return "fake" }
func (f *fakeSource) String() string { return "fake://pack" }

func packTree(name, body string) Tree {
	return Tree{ManifestName: []byte("---\nname: " + name + "\ndescription: does " + name + "\n---\n" + body + "\n")}
}

func newTestSyncer(src *fakeSource) *Syncer {
	n := 0
	return &Syncer{
		Cache:     NewMemoryPackCache(),
		Subs:      NewMemory(),
		Now:       func() time.Time { return time.Unix(1000, 0) },
		NewID:     func() string { n++; return fmt.Sprintf("id-%d", n) },
		SourceFor: func(*Subscription) (Source, error) { return src, nil },
	}
}

func TestSubscribeAndPin(t *testing.T) {
	ctx := context.Background()
	src := &fakeSource{tree: packTree("alpha", "v1"), ref: "sha-v1"}
	y := newTestSyncer(src)

	sub, err := y.Subscribe(ctx, src, "main", "steve")
	if err != nil {
		t.Fatal(err)
	}
	if sub.Name != "alpha" || sub.PinnedSourceRef != "sha-v1" || sub.PinnedBy != "steve" {
		t.Fatalf("bad pin: %+v", sub)
	}
	if sub.HasPending() {
		t.Fatal("fresh subscription should have no pending update")
	}
	// pinned tree is cached under its digest
	if _, err := y.Cache.Get(ctx, sub.PinnedDigest); err != nil {
		t.Fatalf("pinned tree not cached: %v", err)
	}
}

func TestSubscribe_DuplicateName(t *testing.T) {
	ctx := context.Background()
	src := &fakeSource{tree: packTree("alpha", "v1"), ref: "r"}
	y := newTestSyncer(src)
	if _, err := y.Subscribe(ctx, src, "", "s"); err != nil {
		t.Fatal(err)
	}
	if _, err := y.Subscribe(ctx, src, "", "s"); err == nil {
		t.Fatal("expected duplicate-name error")
	}
}

func TestCheck_RecordsPendingButDoesNotMovePin(t *testing.T) {
	ctx := context.Background()
	src := &fakeSource{tree: packTree("alpha", "v1"), ref: "sha-v1"}
	y := newTestSyncer(src)
	sub, _ := y.Subscribe(ctx, src, "main", "s")
	pinnedBefore := sub.PinnedDigest

	// upstream changes
	src.tree = packTree("alpha", "v2-new-instructions")
	src.ref = "sha-v2"

	updated, err := y.Check(ctx, sub.ID)
	if err != nil {
		t.Fatal(err)
	}
	if !updated.HasPending() {
		t.Fatal("expected a pending update after upstream change")
	}
	if updated.PinnedDigest != pinnedBefore {
		t.Fatal("Check must NOT move the pin — that is the supply-chain guard")
	}
	if updated.PendingSourceRef != "sha-v2" {
		t.Errorf("pending ref = %q", updated.PendingSourceRef)
	}
	// the pending tree is cached, ready for Apply
	if _, err := y.Cache.Get(ctx, updated.PendingDigest); err != nil {
		t.Fatalf("pending tree not cached: %v", err)
	}
}

func TestCheck_ClearsStalePendingWhenUpstreamMatches(t *testing.T) {
	ctx := context.Background()
	src := &fakeSource{tree: packTree("alpha", "v1"), ref: "r1"}
	y := newTestSyncer(src)
	sub, _ := y.Subscribe(ctx, src, "main", "s")

	src.tree = packTree("alpha", "v2")
	src.ref = "r2"
	sub, _ = y.Check(ctx, sub.ID) // records pending
	if !sub.HasPending() {
		t.Fatal("precondition: pending expected")
	}
	// upstream reverts to the pinned content
	src.tree = packTree("alpha", "v1")
	src.ref = "r1"
	sub, _ = y.Check(ctx, sub.ID)
	if sub.HasPending() {
		t.Fatal("pending should be cleared once upstream matches the pin again")
	}
}

func TestApply_MovesPinAndClearsPending(t *testing.T) {
	ctx := context.Background()
	src := &fakeSource{tree: packTree("alpha", "v1"), ref: "sha-v1"}
	y := newTestSyncer(src)
	sub, _ := y.Subscribe(ctx, src, "main", "s")

	src.tree = packTree("alpha", "v2")
	src.ref = "sha-v2"
	sub, _ = y.Check(ctx, sub.ID)
	pendingDigest := sub.PendingDigest

	applied, err := y.Apply(ctx, sub.ID, "admin")
	if err != nil {
		t.Fatal(err)
	}
	if applied.PinnedDigest != pendingDigest {
		t.Fatal("Apply must move the pin to the pending digest")
	}
	if applied.PinnedSourceRef != "sha-v2" || applied.PinnedBy != "admin" {
		t.Errorf("bad post-apply pin: %+v", applied)
	}
	if applied.HasPending() {
		t.Fatal("Apply must clear the pending update")
	}
}

func TestApply_NoPending(t *testing.T) {
	ctx := context.Background()
	src := &fakeSource{tree: packTree("alpha", "v1"), ref: "r"}
	y := newTestSyncer(src)
	sub, _ := y.Subscribe(ctx, src, "", "s")
	if _, err := y.Apply(ctx, sub.ID, "admin"); err == nil {
		t.Fatal("expected error applying with no pending update")
	}
}

func TestCheckAll(t *testing.T) {
	ctx := context.Background()
	src := &fakeSource{tree: packTree("alpha", "v1"), ref: "r1"}
	y := newTestSyncer(src)
	sub, _ := y.Subscribe(ctx, src, "main", "s")

	if pend, errs := y.CheckAll(ctx); len(pend) != 0 || len(errs) != 0 {
		t.Fatalf("no change: pend=%v errs=%v", pend, errs)
	}
	src.tree = packTree("alpha", "v2")
	src.ref = "r2"
	pend, errs := y.CheckAll(ctx)
	if len(errs) != 0 {
		t.Fatalf("errs: %v", errs)
	}
	if len(pend) != 1 || pend[0].ID != sub.ID {
		t.Fatalf("expected 1 pending, got %v", pend)
	}
}