package tsm1

import (
	"encoding/binary"
	"fmt"
	"time"

	"github.com/influxdata/influxdb/influxql"
	"github.com/influxdata/influxdb/pkg/pool"
	"github.com/influxdata/influxdb/tsdb"
)

const (
	// BlockFloat64 designates a block encodes float64 values
	BlockFloat64 = byte(0)

	// BlockInteger designates a block encodes int64 values
	BlockInteger = byte(1)

	// BlockBoolean designates a block encodes boolean values
	BlockBoolean = byte(2)

	// BlockString designates a block encodes string values
	BlockString = byte(3)

	// encodedBlockHeaderSize is the size of the header for an encoded block.  There is one
	// byte encoding the type of the block.
	encodedBlockHeaderSize = 1
)

var (
	timeEncoderPool = pool.NewGeneric(1024, func(sz int) interface{} {
		return NewTimeEncoder(sz)
	})
	integerEncoderPool = pool.NewGeneric(1024, func(sz int) interface{} {
		return NewIntegerEncoder(sz)
	})
	floatEncoderPool = pool.NewGeneric(1024, func(sz int) interface{} {
		return NewFloatEncoder()
	})
	stringEncoderPool = pool.NewGeneric(1024, func(sz int) interface{} {
		return NewStringEncoder(sz)
	})
	booleanEncoderPool = pool.NewGeneric(1024, func(sz int) interface{} {
		return NewBooleanEncoder(sz)
	})
)

type Value interface {
	UnixNano() int64
	Value() interface{}
	Size() int
	String() string

	internalOnly()
}

func NewValue(t int64, value interface{}) Value {
	switch v := value.(type) {
	case int64:
		return &IntegerValue{unixnano: t, value: v}
	case float64:
		return &FloatValue{unixnano: t, value: v}
	case bool:
		return &BooleanValue{unixnano: t, value: v}
	case string:
		return &StringValue{unixnano: t, value: v}
	}
	return &EmptyValue{}
}

type EmptyValue struct {
}

func (e *EmptyValue) UnixNano() int64    { return tsdb.EOF }
func (e *EmptyValue) Value() interface{} { return nil }
func (e *EmptyValue) Size() int          { return 0 }
func (e *EmptyValue) String() string     { return "" }

func (_ *EmptyValue) internalOnly()   {}
func (_ *StringValue) internalOnly()  {}
func (_ *IntegerValue) internalOnly() {}
func (_ *BooleanValue) internalOnly() {}
func (_ *FloatValue) internalOnly()   {}

// Encode converts the values to a byte slice.  If there are no values,
// this function panics.
func (a Values) Encode(buf []byte) ([]byte, error) {
	if len(a) == 0 {
		panic("unable to encode block type")
	}

	switch a[0].(type) {
	case *FloatValue:
		return encodeFloatBlock(buf, a)
	case *IntegerValue:
		return encodeIntegerBlock(buf, a)
	case *BooleanValue:
		return encodeBooleanBlock(buf, a)
	case *StringValue:
		return encodeStringBlock(buf, a)
	}

	return nil, fmt.Errorf("unsupported value type %T", a[0])
}

// InfluxQLType returns the influxql.DataType the values map to.
func (a Values) InfluxQLType() (influxql.DataType, error) {
	if len(a) == 0 {
		return influxql.Unknown, fmt.Errorf("no values to infer type")
	}

	switch a[0].(type) {
	case *FloatValue:
		return influxql.Float, nil
	case *IntegerValue:
		return influxql.Integer, nil
	case *BooleanValue:
		return influxql.Boolean, nil
	case *StringValue:
		return influxql.String, nil
	}

	return influxql.Unknown, fmt.Errorf("unsupported value type %T", a[0])
}

// BlockType returns the type of value encoded in a block or an error
// if the block type is unknown.
func BlockType(block []byte) (byte, error) {
	blockType := block[0]
	switch blockType {
	case BlockFloat64, BlockInteger, BlockBoolean, BlockString:
		return blockType, nil
	default:
		return 0, fmt.Errorf("unknown block type: %d", blockType)
	}
}

func BlockCount(block []byte) int {
	if len(block) <= encodedBlockHeaderSize {
		panic(fmt.Sprintf("count of short block: got %v, exp %v", len(block), encodedBlockHeaderSize))
	}
	// first byte is the block type
	tb, _, err := unpackBlock(block[1:])
	if err != nil {
		panic(fmt.Sprintf("BlockCount: error unpacking block: %s", err.Error()))
	}
	return CountTimestamps(tb)
}

// DecodeBlock takes a byte array and will decode into values of the appropriate type
// based on the block.
func DecodeBlock(block []byte, vals []Value) ([]Value, error) {
	if len(block) <= encodedBlockHeaderSize {
		panic(fmt.Sprintf("decode of short block: got %v, exp %v", len(block), encodedBlockHeaderSize))
	}

	blockType, err := BlockType(block)
	if err != nil {
		return nil, err
	}

	switch blockType {
	case BlockFloat64:
		var buf []FloatValue
		decoded, err := DecodeFloatBlock(block, &TimeDecoder{}, &FloatDecoder{}, &buf)
		if len(vals) < len(decoded) {
			vals = make([]Value, len(decoded))
		}
		for i := range decoded {
			vals[i] = &decoded[i]
		}
		return vals[:len(decoded)], err
	case BlockInteger:
		var buf []IntegerValue
		decoded, err := DecodeIntegerBlock(block, &TimeDecoder{}, &IntegerDecoder{}, &buf)
		if len(vals) < len(decoded) {
			vals = make([]Value, len(decoded))
		}
		for i := range decoded {
			vals[i] = &decoded[i]
		}
		return vals[:len(decoded)], err

	case BlockBoolean:
		var buf []BooleanValue
		decoded, err := DecodeBooleanBlock(block, &TimeDecoder{}, &BooleanDecoder{}, &buf)
		if len(vals) < len(decoded) {
			vals = make([]Value, len(decoded))
		}
		for i := range decoded {
			vals[i] = &decoded[i]
		}
		return vals[:len(decoded)], err

	case BlockString:
		var buf []StringValue
		decoded, err := DecodeStringBlock(block, &TimeDecoder{}, &StringDecoder{}, &buf)
		if len(vals) < len(decoded) {
			vals = make([]Value, len(decoded))
		}
		for i := range decoded {
			vals[i] = &decoded[i]
		}
		return vals[:len(decoded)], err

	default:
		panic(fmt.Sprintf("unknown block type: %d", blockType))
	}
}

type FloatValue struct {
	unixnano int64
	value    float64
}

func (f *FloatValue) UnixNano() int64 {
	return f.unixnano
}

func (f *FloatValue) Value() interface{} {
	return f.value
}

func (f *FloatValue) Size() int {
	return 16
}

func (f *FloatValue) String() string {
	return fmt.Sprintf("%v %v", time.Unix(0, f.unixnano), f.value)
}

func encodeFloatBlock(buf []byte, values []Value) (b []byte, err error) {
	if len(values) == 0 {
		return nil, nil
	}

	// A float block is encoded using different compression strategies
	// for timestamps and values.

	// Encode values using Gorilla float compression
	venc := getFloatEncoder()

	// Encode timestamps using an adaptive encoder that uses delta-encoding,
	// frame-or-reference and run length encoding.
	tsenc := getTimeEncoder(len(values))

	for _, v := range values {
		tsenc.Write(v.UnixNano())
		venc.Push(v.(*FloatValue).value)
	}
	venc.Finish()

	var tb, vb []byte

	// Encoded timestamp values
	tb, err = tsenc.Bytes()
	if err != nil {
		goto cleanup
	}
	// Encoded float values
	vb, err = venc.Bytes()
	if err != nil {
		goto cleanup
	}

	// Prepend the first timestamp of the block in the first 8 bytes and the block
	// in the next byte, followed by the block
	b = packBlock(buf, BlockFloat64, tb, vb)

cleanup:
	putTimeEncoder(tsenc)
	putFloatEncoder(venc)
	return

}

func DecodeFloatBlock(block []byte, tdec *TimeDecoder, vdec *FloatDecoder, a *[]FloatValue) ([]FloatValue, error) {
	// Block type is the next block, make sure we actually have a float block
	blockType := block[0]
	if blockType != BlockFloat64 {
		return nil, fmt.Errorf("invalid block type: exp %d, got %d", BlockFloat64, blockType)
	}
	block = block[1:]

	tb, vb, err := unpackBlock(block)
	if err != nil {
		return nil, err
	}

	// Setup our timestamp and value decoders
	tdec.Init(tb)
	if err := vdec.SetBytes(vb); err != nil {
		return nil, err
	}

	// Decode both a timestamp and value
	i := 0
	for tdec.Next() && vdec.Next() {
		ts := tdec.Read()
		v := vdec.Values()
		if i < len(*a) {
			elem := &(*a)[i]
			elem.unixnano = ts
			elem.value = v
		} else {
			*a = append(*a, FloatValue{ts, v})
		}
		i++
	}

	// Did timestamp decoding have an error?
	if tdec.Error() != nil {
		return nil, tdec.Error()
	}
	// Did float decoding have an error?
	if vdec.Error() != nil {
		return nil, vdec.Error()
	}

	return (*a)[:i], nil
}

type BooleanValue struct {
	unixnano int64
	value    bool
}

func (b *BooleanValue) Size() int {
	return 9
}

func (b *BooleanValue) UnixNano() int64 {
	return b.unixnano
}

func (b *BooleanValue) Value() interface{} {
	return b.value
}

func (f *BooleanValue) String() string {
	return fmt.Sprintf("%v %v", time.Unix(0, f.unixnano), f.Value())
}

func encodeBooleanBlock(buf []byte, values []Value) (b []byte, err error) {
	if len(values) == 0 {
		return nil, nil
	}

	// A boolean block is encoded using different compression strategies
	// for timestamps and values.
	venc := getBooleanEncoder(len(values))

	// Encode timestamps using an adaptive encoder
	tsenc := getTimeEncoder(len(values))

	for _, v := range values {
		tsenc.Write(v.UnixNano())
		venc.Write(v.(*BooleanValue).value)
	}

	var tb, vb []byte

	// Encoded timestamp values
	tb, err = tsenc.Bytes()
	if err != nil {
		goto cleanup
	}
	// Encoded float values
	vb, err = venc.Bytes()
	if err != nil {
		goto cleanup
	}

	// Prepend the first timestamp of the block in the first 8 bytes and the block
	// in the next byte, followed by the block
	b = packBlock(buf, BlockBoolean, tb, vb)

cleanup:
	putTimeEncoder(tsenc)
	putBooleanEncoder(venc)
	return
}

func DecodeBooleanBlock(block []byte, tdec *TimeDecoder, vdec *BooleanDecoder, a *[]BooleanValue) ([]BooleanValue, error) {
	// Block type is the next block, make sure we actually have a float block
	blockType := block[0]
	if blockType != BlockBoolean {
		return nil, fmt.Errorf("invalid block type: exp %d, got %d", BlockBoolean, blockType)
	}
	block = block[1:]

	tb, vb, err := unpackBlock(block)
	if err != nil {
		return nil, err
	}

	// Setup our timestamp and value decoders
	tdec.Init(tb)
	vdec.SetBytes(vb)

	// Decode both a timestamp and value
	i := 0
	for tdec.Next() && vdec.Next() {
		ts := tdec.Read()
		v := vdec.Read()
		if i < len(*a) {
			elem := &(*a)[i]
			elem.unixnano = ts
			elem.value = v
		} else {
			*a = append(*a, BooleanValue{ts, v})
		}
		i++
	}

	// Did timestamp decoding have an error?
	if tdec.Error() != nil {
		return nil, tdec.Error()
	}
	// Did boolean decoding have an error?
	if vdec.Error() != nil {
		return nil, vdec.Error()
	}

	return (*a)[:i], nil
}

type IntegerValue struct {
	unixnano int64
	value    int64
}

func (v *IntegerValue) Value() interface{} {
	return v.value
}

func (v *IntegerValue) UnixNano() int64 {
	return v.unixnano
}

func (v *IntegerValue) Size() int {
	return 16
}

func (f *IntegerValue) String() string {
	return fmt.Sprintf("%v %v", time.Unix(0, f.unixnano), f.Value())
}

func encodeIntegerBlock(buf []byte, values []Value) (b []byte, err error) {
	tsEnc := getTimeEncoder(len(values))
	vEnc := getIntegerEncoder(len(values))

	for _, v := range values {
		tsEnc.Write(v.UnixNano())
		vEnc.Write(v.(*IntegerValue).value)
	}

	var tb, vb []byte

	// Encoded timestamp values
	tb, err = tsEnc.Bytes()
	if err != nil {
		goto cleanup
	}
	// Encoded int64 values
	vb, err = vEnc.Bytes()
	if err != nil {
		goto cleanup
	}

	// Prepend the first timestamp of the block in the first 8 bytes
	b = packBlock(buf, BlockInteger, tb, vb)

cleanup:
	putTimeEncoder(tsEnc)
	putIntegerEncoder(vEnc)
	return
}

func DecodeIntegerBlock(block []byte, tdec *TimeDecoder, vdec *IntegerDecoder, a *[]IntegerValue) ([]IntegerValue, error) {
	blockType := block[0]
	if blockType != BlockInteger {
		return nil, fmt.Errorf("invalid block type: exp %d, got %d", BlockInteger, blockType)
	}

	block = block[1:]

	// The first 8 bytes is the minimum timestamp of the block
	tb, vb, err := unpackBlock(block)
	if err != nil {
		return nil, err
	}

	// Setup our timestamp and value decoders
	tdec.Init(tb)
	vdec.SetBytes(vb)

	// Decode both a timestamp and value
	i := 0
	for tdec.Next() && vdec.Next() {
		ts := tdec.Read()
		v := vdec.Read()
		if i < len(*a) {
			elem := &(*a)[i]
			elem.unixnano = ts
			elem.value = v
		} else {
			*a = append(*a, IntegerValue{ts, v})
		}
		i++
	}

	// Did timestamp decoding have an error?
	if tdec.Error() != nil {
		return nil, tdec.Error()
	}
	// Did int64 decoding have an error?
	if vdec.Error() != nil {
		return nil, vdec.Error()
	}

	return (*a)[:i], nil
}

type StringValue struct {
	unixnano int64
	value    string
}

func (v *StringValue) Value() interface{} {
	return v.value
}

func (v *StringValue) UnixNano() int64 {
	return v.unixnano
}

func (v *StringValue) Size() int {
	return 8 + len(v.value)
}

func (f *StringValue) String() string {
	return fmt.Sprintf("%v %v", time.Unix(0, f.unixnano), f.Value())
}

func encodeStringBlock(buf []byte, values []Value) (b []byte, err error) {
	tsEnc := getTimeEncoder(len(values))
	vEnc := getStringEncoder(len(values) * len(values[0].(*StringValue).value))

	for _, v := range values {
		tsEnc.Write(v.UnixNano())
		vEnc.Write(v.(*StringValue).value)
	}

	var tb, vb []byte

	// Encoded timestamp values
	tb, err = tsEnc.Bytes()
	if err != nil {
		goto cleanup
	}
	// Encoded string values
	vb, err = vEnc.Bytes()
	if err != nil {
		goto cleanup
	}

	// Prepend the first timestamp of the block in the first 8 bytes
	b = packBlock(buf, BlockString, tb, vb)

cleanup:
	putTimeEncoder(tsEnc)
	putStringEncoder(vEnc)
	return
}

func DecodeStringBlock(block []byte, tdec *TimeDecoder, vdec *StringDecoder, a *[]StringValue) ([]StringValue, error) {
	blockType := block[0]
	if blockType != BlockString {
		return nil, fmt.Errorf("invalid block type: exp %d, got %d", BlockString, blockType)
	}

	block = block[1:]

	// The first 8 bytes is the minimum timestamp of the block
	tb, vb, err := unpackBlock(block)
	if err != nil {
		return nil, err
	}

	// Setup our timestamp and value decoders
	tdec.Init(tb)
	if err := vdec.SetBytes(vb); err != nil {
		return nil, err
	}

	// Decode both a timestamp and value
	i := 0
	for tdec.Next() && vdec.Next() {
		ts := tdec.Read()
		v := vdec.Read()
		if i < len(*a) {
			elem := &(*a)[i]
			elem.unixnano = ts
			elem.value = v
		} else {
			*a = append(*a, StringValue{ts, v})
		}
		i++
	}

	// Did timestamp decoding have an error?
	if tdec.Error() != nil {
		return nil, tdec.Error()
	}
	// Did string decoding have an error?
	if vdec.Error() != nil {
		return nil, vdec.Error()
	}

	return (*a)[:i], nil
}

func packBlock(buf []byte, typ byte, ts []byte, values []byte) []byte {
	// We encode the length of the timestamp block using a variable byte encoding.
	// This allows small byte slices to take up 1 byte while larger ones use 2 or more.
	sz := 1 + binary.MaxVarintLen64 + len(ts) + len(values)
	if cap(buf) < sz {
		buf = make([]byte, sz)
	}
	b := buf[:sz]
	b[0] = typ
	i := binary.PutUvarint(b[1:1+binary.MaxVarintLen64], uint64(len(ts)))
	i += 1

	// block is <len timestamp bytes>, <ts bytes>, <value bytes>
	copy(b[i:], ts)
	// We don't encode the value length because we know it's the rest of the block after
	// the timestamp block.
	copy(b[i+len(ts):], values)
	return b[:i+len(ts)+len(values)]
}

func unpackBlock(buf []byte) (ts, values []byte, err error) {
	// Unpack the timestamp block length
	tsLen, i := binary.Uvarint(buf)
	if i <= 0 {
		err = fmt.Errorf("unpackBlock: unable to read timestamp block length")
		return
	}

	// Unpack the timestamp bytes
	tsIdx := int(i) + int(tsLen)
	if tsIdx > len(buf) {
		err = fmt.Errorf("unpackBlock: not enough data for timestamp")
		return
	}
	ts = buf[int(i):tsIdx]

	// Unpack the value bytes
	values = buf[tsIdx:]
	return
}

// ZigZagEncode converts a int64 to a uint64 by zig zagging negative and positive values
// across even and odd numbers.  Eg. [0,-1,1,-2] becomes [0, 1, 2, 3]
func ZigZagEncode(x int64) uint64 {
	return uint64(uint64(x<<1) ^ uint64((int64(x) >> 63)))
}

// ZigZagDecode converts a previously zigzag encoded uint64 back to a int64
func ZigZagDecode(v uint64) int64 {
	return int64((v >> 1) ^ uint64((int64(v&1)<<63)>>63))
}
func getTimeEncoder(sz int) TimeEncoder {
	x := timeEncoderPool.Get(sz).(TimeEncoder)
	x.Reset()
	return x
}
func putTimeEncoder(enc TimeEncoder) { timeEncoderPool.Put(enc) }

func getIntegerEncoder(sz int) IntegerEncoder {
	x := integerEncoderPool.Get(sz).(IntegerEncoder)
	x.Reset()
	return x
}
func putIntegerEncoder(enc IntegerEncoder) { integerEncoderPool.Put(enc) }

func getFloatEncoder() *FloatEncoder {
	x := floatEncoderPool.Get(1024).(*FloatEncoder)
	x.Reset()
	return x
}
func putFloatEncoder(enc *FloatEncoder) { floatEncoderPool.Put(enc) }

func getStringEncoder(sz int) StringEncoder {
	x := stringEncoderPool.Get(sz).(StringEncoder)
	x.Reset()
	return x
}
func putStringEncoder(enc StringEncoder) { stringEncoderPool.Put(enc) }

func getBooleanEncoder(sz int) BooleanEncoder {
	x := booleanEncoderPool.Get(sz).(BooleanEncoder)
	x.Reset()
	return x
}
func putBooleanEncoder(enc BooleanEncoder) { booleanEncoderPool.Put(enc) }