package pvdata_test

import (
	"bytes"
	"math"
	"reflect"
	"testing"

	"github.com/uopi/gopva/pvdata"
)

// ---- Scalar value codec: every type code -----------------------------

func TestScalarRoundTrip(t *testing.T) {
	cases := []struct {
		name string
		tc   byte
		v    pvdata.Value
	}{
		{"bool-true", pvdata.TypeCodeBoolean, true},
		{"bool-false", pvdata.TypeCodeBoolean, false},
		{"byte", pvdata.TypeCodeByte, int8(-12)},
		{"short", pvdata.TypeCodeShort, int16(-3000)},
		{"int", pvdata.TypeCodeInt, int32(-100000)},
		{"long", pvdata.TypeCodeLong, int64(-1 << 40)},
		{"ubyte", pvdata.TypeCodeUByte, uint8(200)},
		{"ushort", pvdata.TypeCodeUShort, uint16(60000)},
		{"uint", pvdata.TypeCodeUInt, uint32(4000000000)},
		{"ulong", pvdata.TypeCodeULong, uint64(1 << 50)},
		{"float", pvdata.TypeCodeFloat, float32(1.5)},
		{"double", pvdata.TypeCodeDouble, float64(2.5)},
	}
	for _, c := range cases {
		t.Run(c.name, func(t *testing.T) {
			desc := pvdata.FieldDesc{Kind: pvdata.KindScalar, TypeCode: c.tc}
			var buf bytes.Buffer
			if err := pvdata.WriteValue(&buf, desc, c.v); err != nil {
				t.Fatalf("WriteValue: %v", err)
			}
			got, err := pvdata.ReadValue(&buf, desc)
			if err != nil {
				t.Fatalf("ReadValue: %v", err)
			}
			if got != c.v {
				t.Errorf("got %v (%T) want %v (%T)", got, got, c.v, c.v)
			}
		})
	}
}

// ---- Scalar array codec: every array code ----------------------------

func TestScalarArrayRoundTrip(t *testing.T) {
	cases := []struct {
		name string
		tc   byte
		v    pvdata.Value
	}{
		{"bool", pvdata.TypeCodeBoolArr, []bool{true, false, true}},
		{"byte", pvdata.TypeCodeByteArr, []int8{-1, 2, -3}},
		{"short", pvdata.TypeCodeShortArr, []int16{-1, 2, 30000}},
		{"int", pvdata.TypeCodeIntArr, []int32{-1, 2, 1 << 30}},
		{"long", pvdata.TypeCodeLongArr, []int64{-1, 1 << 40}},
		{"ubyte", pvdata.TypeCodeUByteArr, []uint8{1, 2, 255}},
		{"ushort", pvdata.TypeCodeUShortArr, []uint16{1, 60000}},
		{"uint", pvdata.TypeCodeUIntArr, []uint32{1, 4000000000}},
		{"ulong", pvdata.TypeCodeULongArr, []uint64{1, 1 << 50}},
		{"float", pvdata.TypeCodeFloatArr, []float32{1.5, -2.25}},
		{"double", pvdata.TypeCodeDoubleArr, []float64{1.5, -2.25}},
	}
	for _, c := range cases {
		t.Run(c.name, func(t *testing.T) {
			desc := pvdata.FieldDesc{Kind: pvdata.KindScalarArr, TypeCode: c.tc}
			var buf bytes.Buffer
			if err := pvdata.WriteValue(&buf, desc, c.v); err != nil {
				t.Fatalf("WriteValue: %v", err)
			}
			got, err := pvdata.ReadValue(&buf, desc)
			if err != nil {
				t.Fatalf("ReadValue: %v", err)
			}
			if !reflect.DeepEqual(got, c.v) {
				t.Errorf("got %v want %v", got, c.v)
			}
		})
	}
}

func TestStringArrayRoundTrip(t *testing.T) {
	desc := pvdata.FieldDesc{Kind: pvdata.KindStringArr, TypeCode: pvdata.TypeCodeStringArr}
	for _, v := range [][]string{{"a", "", "epics"}, {}} {
		var buf bytes.Buffer
		if err := pvdata.WriteValue(&buf, desc, v); err != nil {
			t.Fatalf("WriteValue: %v", err)
		}
		got, err := pvdata.ReadValue(&buf, desc)
		if err != nil {
			t.Fatalf("ReadValue: %v", err)
		}
		gs := got.([]string)
		if len(gs) != len(v) {
			t.Fatalf("len: got %d want %d", len(gs), len(v))
		}
		for i := range v {
			if gs[i] != v[i] {
				t.Errorf("[%d]: got %q want %q", i, gs[i], v[i])
			}
		}
	}
}

// ---- FieldDesc round-trip for every Kind -----------------------------

func TestFieldDescVariants(t *testing.T) {
	descs := []pvdata.FieldDesc{
		{TypeCode: pvdata.TypeCodeNull},
		{Kind: pvdata.KindString, TypeCode: pvdata.TypeCodeString},
		{Kind: pvdata.KindStringArr, TypeCode: pvdata.TypeCodeStringArr},
		{Kind: pvdata.KindVariant, TypeCode: pvdata.TypeCodeVariant},
		{Kind: pvdata.KindScalarArr, TypeCode: pvdata.TypeCodeDoubleArr},
		{Kind: pvdata.KindUnion, TypeCode: pvdata.TypeCodeUnion, TypeID: "u", Fields: []pvdata.Field{
			{Name: "a", Desc: pvdata.FieldDesc{Kind: pvdata.KindScalar, TypeCode: pvdata.TypeCodeInt}},
		}},
		{Kind: pvdata.KindStructArr, TypeCode: pvdata.TypeCodeStructArr, TypeID: "s", Fields: []pvdata.Field{
			{Name: "x", Desc: pvdata.FieldDesc{Kind: pvdata.KindScalar, TypeCode: pvdata.TypeCodeDouble}},
		}},
		{Kind: pvdata.KindUnionArr, TypeCode: pvdata.TypeCodeUnionArr, TypeID: "ua", Fields: []pvdata.Field{
			{Name: "y", Desc: pvdata.FieldDesc{Kind: pvdata.KindScalar, TypeCode: pvdata.TypeCodeInt}},
		}},
	}
	for _, d := range descs {
		var buf bytes.Buffer
		if err := pvdata.WriteFieldDesc(&buf, d); err != nil {
			t.Fatalf("WriteFieldDesc(%#x): %v", d.TypeCode, err)
		}
		got, err := pvdata.ReadFieldDesc(&buf)
		if err != nil {
			t.Fatalf("ReadFieldDesc(%#x): %v", d.TypeCode, err)
		}
		if got.TypeCode != d.TypeCode {
			t.Errorf("TypeCode: got %#x want %#x", got.TypeCode, d.TypeCode)
		}
		if got.TypeID != d.TypeID {
			t.Errorf("TypeID: got %q want %q", got.TypeID, d.TypeID)
		}
		if len(got.Fields) != len(d.Fields) {
			t.Errorf("Fields: got %d want %d", len(got.Fields), len(d.Fields))
		}
	}
}

// ---- Struct array value (readStructArr) ------------------------------

func TestStructArrRoundTrip(t *testing.T) {
	fields := []pvdata.Field{
		{Name: "x", Desc: pvdata.FieldDesc{Kind: pvdata.KindScalar, TypeCode: pvdata.TypeCodeInt}},
	}
	elems := []pvdata.StructValue{
		{TypeID: "p", Fields: []pvdata.FieldValue{{Name: "x", Value: int32(1)}}},
		{TypeID: "p", Fields: []pvdata.FieldValue{{Name: "x", Value: int32(2)}}},
	}
	var buf bytes.Buffer
	if err := pvdata.WriteSize(&buf, int64(len(elems))); err != nil {
		t.Fatal(err)
	}
	sdesc := pvdata.FieldDesc{Kind: pvdata.KindStruct, TypeCode: pvdata.TypeCodeStruct, TypeID: "p", Fields: fields}
	for _, sv := range elems {
		if err := pvdata.WriteValue(&buf, sdesc, sv); err != nil {
			t.Fatal(err)
		}
	}
	adesc := pvdata.FieldDesc{Kind: pvdata.KindStructArr, TypeCode: pvdata.TypeCodeStructArr, TypeID: "p", Fields: fields}
	got, err := pvdata.ReadValue(&buf, adesc)
	if err != nil {
		t.Fatal(err)
	}
	arr := got.([]pvdata.StructValue)
	if len(arr) != 2 || arr[0].Fields[0].Value.(int32) != 1 || arr[1].Fields[0].Value.(int32) != 2 {
		t.Errorf("got %+v", arr)
	}
}

// ---- Union value (readUnion / writeUnion) ----------------------------

func unionDesc() pvdata.FieldDesc {
	return pvdata.FieldDesc{
		Kind: pvdata.KindUnion, TypeCode: pvdata.TypeCodeUnion, TypeID: "u",
		Fields: []pvdata.Field{
			{Name: "i", Desc: pvdata.FieldDesc{Kind: pvdata.KindScalar, TypeCode: pvdata.TypeCodeInt}},
			{Name: "s", Desc: pvdata.FieldDesc{Kind: pvdata.KindString, TypeCode: pvdata.TypeCodeString}},
		},
	}
}

func TestUnionSelectedValue(t *testing.T) {
	desc := unionDesc()
	// Manually encode: select field 1 (string) with value "hi".
	var buf bytes.Buffer
	if err := pvdata.WriteSize(&buf, 1); err != nil {
		t.Fatal(err)
	}
	if err := pvdata.WriteValue(&buf, desc.Fields[1].Desc, "hi"); err != nil {
		t.Fatal(err)
	}
	got, err := pvdata.ReadValue(&buf, desc)
	if err != nil {
		t.Fatal(err)
	}
	uv := got.(pvdata.UnionValue)
	if uv.Selected != 1 || uv.Name != "s" || uv.Value.(string) != "hi" {
		t.Errorf("got %+v", uv)
	}
}

func TestUnionNullSelector(t *testing.T) {
	desc := unionDesc()
	// writeUnion only writes the selector; an out-of-range selector → null.
	var buf bytes.Buffer
	if err := pvdata.WriteValue(&buf, desc, pvdata.UnionValue{Selected: 7}); err != nil {
		t.Fatal(err)
	}
	got, err := pvdata.ReadValue(&buf, desc)
	if err != nil {
		t.Fatal(err)
	}
	uv := got.(pvdata.UnionValue)
	if uv.Selected != 7 || uv.Value != nil {
		t.Errorf("got %+v, want null selector", uv)
	}
}

func TestUnionArrRoundTrip(t *testing.T) {
	desc := pvdata.FieldDesc{
		Kind: pvdata.KindUnionArr, TypeCode: pvdata.TypeCodeUnionArr, TypeID: "u",
		Fields: []pvdata.Field{
			{Name: "i", Desc: pvdata.FieldDesc{Kind: pvdata.KindScalar, TypeCode: pvdata.TypeCodeInt}},
		},
	}
	var buf bytes.Buffer
	if err := pvdata.WriteSize(&buf, 2); err != nil {
		t.Fatal(err)
	}
	for _, val := range []int32{10, 20} {
		if err := pvdata.WriteSize(&buf, 0); err != nil { // selector 0
			t.Fatal(err)
		}
		if err := pvdata.WriteValue(&buf, desc.Fields[0].Desc, val); err != nil {
			t.Fatal(err)
		}
	}
	got, err := pvdata.ReadValue(&buf, desc)
	if err != nil {
		t.Fatal(err)
	}
	arr := got.([]pvdata.UnionValue)
	if len(arr) != 2 || arr[0].Value.(int32) != 10 || arr[1].Value.(int32) != 20 {
		t.Errorf("got %+v", arr)
	}
}

// ---- Variant value (readVariant + WriteValue variant path) -----------

func TestVariantRoundTrip(t *testing.T) {
	inner := pvdata.FieldDesc{Kind: pvdata.KindScalar, TypeCode: pvdata.TypeCodeDouble}
	vv := pvdata.VariantValue{Desc: inner, Value: float64(9.5)}
	desc := pvdata.FieldDesc{Kind: pvdata.KindVariant, TypeCode: pvdata.TypeCodeVariant}
	var buf bytes.Buffer
	if err := pvdata.WriteValue(&buf, desc, vv); err != nil {
		t.Fatal(err)
	}
	got, err := pvdata.ReadValue(&buf, desc)
	if err != nil {
		t.Fatal(err)
	}
	gvv := got.(pvdata.VariantValue)
	if gvv.Value.(float64) != 9.5 || gvv.Desc.TypeCode != pvdata.TypeCodeDouble {
		t.Errorf("got %+v", gvv)
	}
}

// ---- Compact size: extended (>MaxInt32) encodings --------------------

func TestCompactSizeLarge(t *testing.T) {
	cases := []int64{math.MaxInt32, math.MaxInt32 + 1, 1 << 40}
	for _, n := range cases {
		var buf bytes.Buffer
		if err := pvdata.WriteSize(&buf, n); err != nil {
			t.Fatalf("WriteSize(%d): %v", n, err)
		}
		got, err := pvdata.ReadSize(&buf)
		if err != nil {
			t.Fatalf("ReadSize(%d): %v", n, err)
		}
		if got != n {
			t.Errorf("round-trip size %d → %d", n, got)
		}
	}
}

// ---- Error / truncation paths ----------------------------------------

func TestReadErrors(t *testing.T) {
	if _, err := pvdata.ReadSize(bytes.NewReader(nil)); err == nil {
		t.Error("ReadSize on empty: want error")
	}
	if _, err := pvdata.ReadString(bytes.NewReader([]byte{0x05})); err == nil {
		t.Error("ReadString truncated: want error")
	}
	if _, err := pvdata.ReadFieldDesc(bytes.NewReader(nil)); err == nil {
		t.Error("ReadFieldDesc on empty: want error")
	}
	// Unknown scalar type code.
	badScalar := pvdata.FieldDesc{Kind: pvdata.KindScalar, TypeCode: 0x99}
	if _, err := pvdata.ReadValue(bytes.NewReader([]byte{1, 2, 3, 4}), badScalar); err == nil {
		t.Error("ReadValue unknown scalar code: want error")
	}
	// Unknown array type code (after a valid size byte).
	badArr := pvdata.FieldDesc{Kind: pvdata.KindScalarArr, TypeCode: 0x99}
	if _, err := pvdata.ReadValue(bytes.NewReader([]byte{0x01}), badArr); err == nil {
		t.Error("ReadValue unknown array code: want error")
	}
	// Unknown kind.
	if _, err := pvdata.ReadValue(bytes.NewReader(nil), pvdata.FieldDesc{Kind: pvdata.Kind(99)}); err == nil {
		t.Error("ReadValue unknown kind: want error")
	}
	// WriteValue unsupported kind (struct array has no writer).
	if err := pvdata.WriteValue(&bytes.Buffer{}, pvdata.FieldDesc{Kind: pvdata.KindStructArr}, nil); err == nil {
		t.Error("WriteValue unsupported kind: want error")
	}
}

// ---- BitSet edges ----------------------------------------------------

func TestBitSetEdges(t *testing.T) {
	bs := pvdata.NewBitSet()
	if bs.Has(0) {
		t.Error("fresh NewBitSet should be empty")
	}
	bs.Set(0)
	bs.Set(5)
	bs.Set(12)
	if got := bs.FieldIndices(); !reflect.DeepEqual(got, []int{0, 5, 12}) {
		t.Errorf("FieldIndices: got %v want [0 5 12]", got)
	}
	if bs.Has(100) { // far out of range → no panic, false
		t.Error("Has(100) should be false")
	}

	// Empty BitSet round-trips as a zero-length payload.
	var buf bytes.Buffer
	if err := pvdata.WriteBitSet(&buf, pvdata.NewBitSet()); err != nil {
		t.Fatal(err)
	}
	got, err := pvdata.ReadBitSet(&buf)
	if err != nil {
		t.Fatal(err)
	}
	if len(got.FieldIndices()) != 0 {
		t.Errorf("empty BitSet round-trip: got %v", got.FieldIndices())
	}
}