package diff

import (
	"testing"

	"github.com/vasyakrg/dns-autoresolver/internal/model"
)

func find(cs Changeset, key string) *RecordDiff {
	for i := range cs.Diffs {
		d := cs.Diffs[i]
		var r *model.Record
		if d.Desired != nil {
			r = d.Desired
		} else {
			r = d.Actual
		}
		if r.Key() == key {
			return &cs.Diffs[i]
		}
	}
	return nil
}

func TestDiffAddUpdateDeleteInSync(t *testing.T) {
	tmpl := []model.Record{
		{Type: model.A, Name: "a.example.com.", TTL: 300, Values: []string{"1.1.1.1"}}, // in sync
		{Type: model.A, Name: "b.example.com.", TTL: 300, Values: []string{"2.2.2.2"}}, // update
		{Type: model.A, Name: "c.example.com.", TTL: 300, Values: []string{"3.3.3.3"}}, // add
	}
	actual := []model.Record{
		{Type: model.A, Name: "a.example.com.", TTL: 300, Values: []string{"1.1.1.1"}},
		{Type: model.A, Name: "b.example.com.", TTL: 300, Values: []string{"9.9.9.9"}},
		{Type: model.A, Name: "d.example.com.", TTL: 300, Values: []string{"4.4.4.4"}}, // delete (extra)
	}
	cs := Diff(tmpl, actual)

	if d := find(cs, "A a.example.com."); d == nil || d.Kind != InSync {
		t.Fatalf("a should be InSync, got %+v", d)
	}
	if d := find(cs, "A b.example.com."); d == nil || d.Kind != Update {
		t.Fatalf("b should be Update, got %+v", d)
	}
	if d := find(cs, "A c.example.com."); d == nil || d.Kind != Add {
		t.Fatalf("c should be Add, got %+v", d)
	}
	if d := find(cs, "A d.example.com."); d == nil || d.Kind != Delete {
		t.Fatalf("d should be Delete, got %+v", d)
	}
}

func TestDiffMarksReadOnlyForNSSOA(t *testing.T) {
	tmpl := []model.Record{{Type: model.NS, Name: "example.com.", TTL: 3600, Values: []string{"ns1.example.com."}}}
	actual := []model.Record{{Type: model.NS, Name: "example.com.", TTL: 3600, Values: []string{"ns9.other.com."}}}
	cs := Diff(tmpl, actual)
	d := find(cs, "NS example.com.")
	if d == nil || d.Kind != Update || !d.ReadOnly {
		t.Fatalf("NS diff must be Update and ReadOnly, got %+v", d)
	}
}

// Global Constraint: an empty/nil template must not silently no-op — every managed
// record in the zone must surface as a Delete, while read-only records (NS/SOA)
// stay ReadOnly and excluded from Actionable(). This guards against mass deletion
// bugs where a missing template accidentally wipes the zone unattended.
func TestDiffEmptyTemplateDeletesAllManagedKeepsNSReadOnly(t *testing.T) {
	actual := []model.Record{
		{Type: model.A, Name: "a.example.com.", TTL: 300, Values: []string{"1.1.1.1"}},
		{Type: model.A, Name: "b.example.com.", TTL: 300, Values: []string{"2.2.2.2"}},
		{Type: model.NS, Name: "example.com.", TTL: 3600, Values: []string{"ns1.example.com."}},
	}
	cs := Diff(nil, actual)

	if len(cs.Diffs) != 3 {
		t.Fatalf("expected 3 diffs (2 A deletes + 1 NS), got %d: %+v", len(cs.Diffs), cs.Diffs)
	}

	da := find(cs, "A a.example.com.")
	if da == nil || da.Kind != Delete || da.ReadOnly {
		t.Fatalf("A a.example.com. must be a non-read-only Delete, got %+v", da)
	}
	db := find(cs, "A b.example.com.")
	if db == nil || db.Kind != Delete || db.ReadOnly {
		t.Fatalf("A b.example.com. must be a non-read-only Delete, got %+v", db)
	}
	dns := find(cs, "NS example.com.")
	if dns == nil || dns.Kind != Delete || !dns.ReadOnly {
		t.Fatalf("NS example.com. must be a ReadOnly Delete, got %+v", dns)
	}

	act := cs.Actionable()
	if len(act) != 2 {
		t.Fatalf("expected 2 actionable deletes (A records only), got %d: %+v", len(act), act)
	}
	for _, d := range act {
		if d.Type == model.NS {
			t.Fatalf("NS must be excluded from Actionable(), got %+v", d)
		}
	}
}

func TestActionableExcludesInSyncAndReadOnly(t *testing.T) {
	tmpl := []model.Record{
		{Type: model.A, Name: "a.example.com.", TTL: 300, Values: []string{"1.1.1.1"}},          // in sync
		{Type: model.A, Name: "b.example.com.", TTL: 300, Values: []string{"2.2.2.2"}},          // add
		{Type: model.NS, Name: "example.com.", TTL: 3600, Values: []string{"ns1.example.com."}}, // read-only add
	}
	actual := []model.Record{
		{Type: model.A, Name: "a.example.com.", TTL: 300, Values: []string{"1.1.1.1"}},
	}
	act := Diff(tmpl, actual).Actionable()
	if len(act) != 1 || act[0].Name != "b.example.com." {
		t.Fatalf("only b.example.com. is actionable, got %+v", act)
	}
}

// Prune-guard: with an empty/nil template every managed zone record surfaces
// as a Delete. Prunes() must isolate exactly those (potentially destructive)
// entries, while Updates() must stay empty — there is nothing safe to apply.
func TestPrunesEmptyTemplateAllManagedNoneInUpdates(t *testing.T) {
	actual := []model.Record{
		{Type: model.A, Name: "a.example.com.", TTL: 300, Values: []string{"1.1.1.1"}},
		{Type: model.A, Name: "b.example.com.", TTL: 300, Values: []string{"2.2.2.2"}},
		{Type: model.NS, Name: "example.com.", TTL: 3600, Values: []string{"ns1.example.com."}},
	}
	cs := Diff(nil, actual)

	prunes := cs.Prunes()
	if len(prunes) != 2 {
		t.Fatalf("expected 2 managed prunes (A records only), got %d: %+v", len(prunes), prunes)
	}
	for _, d := range prunes {
		if d.Kind != Delete {
			t.Fatalf("Prunes() must only contain Delete diffs, got %+v", d)
		}
		if d.ReadOnly {
			t.Fatalf("Prunes() must exclude ReadOnly diffs, got %+v", d)
		}
		if d.Type == model.NS {
			t.Fatalf("NS must be excluded from Prunes(), got %+v", d)
		}
	}

	updates := cs.Updates()
	if len(updates) != 0 {
		t.Fatalf("expected 0 updates for an empty template, got %d: %+v", len(updates), updates)
	}
}

// Mixed case: Add/Update land in Updates(), Delete lands in Prunes(), and the
// ReadOnly NS diff (here an Add) is excluded from both — mirroring Actionable().
func TestUpdatesAndPrunesMixedSeparation(t *testing.T) {
	tmpl := []model.Record{
		{Type: model.A, Name: "a.example.com.", TTL: 300, Values: []string{"1.1.1.1"}}, // in sync
		{Type: model.A, Name: "b.example.com.", TTL: 300, Values: []string{"9.9.9.9"}}, // update
		{Type: model.A, Name: "c.example.com.", TTL: 300, Values: []string{"3.3.3.3"}}, // add
		{Type: model.NS, Name: "example.com.", TTL: 3600, Values: []string{"ns1.example.com."}}, // read-only add
	}
	actual := []model.Record{
		{Type: model.A, Name: "a.example.com.", TTL: 300, Values: []string{"1.1.1.1"}},
		{Type: model.A, Name: "b.example.com.", TTL: 300, Values: []string{"2.2.2.2"}},
		{Type: model.A, Name: "d.example.com.", TTL: 300, Values: []string{"4.4.4.4"}}, // delete (extra)
	}
	cs := Diff(tmpl, actual)

	updates := cs.Updates()
	if len(updates) != 2 {
		t.Fatalf("expected 2 updates (b update + c add), got %d: %+v", len(updates), updates)
	}
	for _, d := range updates {
		if d.Kind != Add && d.Kind != Update {
			t.Fatalf("Updates() must only contain Add/Update diffs, got %+v", d)
		}
		if d.ReadOnly {
			t.Fatalf("Updates() must exclude ReadOnly diffs, got %+v", d)
		}
	}

	prunes := cs.Prunes()
	if len(prunes) != 1 || prunes[0].Name != "d.example.com." {
		t.Fatalf("expected exactly 1 prune (d.example.com.), got %+v", prunes)
	}
	if prunes[0].ReadOnly {
		t.Fatalf("prune must not be ReadOnly, got %+v", prunes[0])
	}

	// Updates ∪ Prunes must equal Actionable, with no overlap.
	act := cs.Actionable()
	if len(act) != len(updates)+len(prunes) {
		t.Fatalf("Updates()+Prunes() must partition Actionable(): actionable=%d updates=%d prunes=%d",
			len(act), len(updates), len(prunes))
	}
}

// Dedup semantics: index() is keyed by model.Record.Key(). If the same Key()
// appears twice within a single slice (e.g. actual records fetched from a
// provider with a duplicate RRset entry), the map assignment in the loop
// means the LAST occurrence wins and earlier ones are discarded silently.
// This test fixes that behavior in place so it is a documented, intentional
// choice rather than an accidental artifact of map iteration order.
func TestIndexDedupLastWriteWins(t *testing.T) {
	actual := []model.Record{
		{Type: model.A, Name: "dup.example.com.", TTL: 300, Values: []string{"1.1.1.1"}},
		{Type: model.A, Name: "dup.example.com.", TTL: 300, Values: []string{"9.9.9.9"}}, // same Key(), later wins
	}
	tmpl := []model.Record{
		{Type: model.A, Name: "dup.example.com.", TTL: 300, Values: []string{"9.9.9.9"}},
	}
	cs := Diff(tmpl, actual)

	// Only one diff should exist for the duplicated key (dedup collapsed it),
	// and it must reflect the LAST actual record ("9.9.9.9"), matching the
	// template value, hence InSync rather than Update.
	d := find(cs, "A dup.example.com.")
	if d == nil {
		t.Fatalf("expected a diff for dup.example.com.")
	}
	if d.Kind != InSync {
		t.Fatalf("expected InSync (last actual record wins in index()), got %+v", d)
	}
	if d.Actual == nil || len(d.Actual.Values) != 1 || d.Actual.Values[0] != "9.9.9.9" {
		t.Fatalf("expected Actual to be the last duplicate (9.9.9.9), got %+v", d.Actual)
	}

	count := 0
	for _, dd := range cs.Diffs {
		if dd.Type == model.A && dd.Name == "dup.example.com." {
			count++
		}
	}
	if count != 1 {
		t.Fatalf("expected exactly 1 diff for the duplicated key, got %d", count)
	}
}