package msgpack

import (
	"fmt"
	"math"
	"reflect"

	"github.com/vmihailenco/msgpack/v5/codes"
)

func (d *Decoder) skipN(n int) error {
	_, err := d.readN(n)
	return err
}

func (d *Decoder) uint8() (uint8, error) {
	c, err := d.readCode()
	if err != nil {
		return 0, err
	}
	return uint8(c), nil
}

func (d *Decoder) int8() (int8, error) {
	n, err := d.uint8()
	return int8(n), err
}

func (d *Decoder) uint16() (uint16, error) {
	b, err := d.readN(2)
	if err != nil {
		return 0, err
	}
	return (uint16(b[0]) << 8) | uint16(b[1]), nil
}

func (d *Decoder) int16() (int16, error) {
	n, err := d.uint16()
	return int16(n), err
}

func (d *Decoder) uint32() (uint32, error) {
	b, err := d.readN(4)
	if err != nil {
		return 0, err
	}
	n := (uint32(b[0]) << 24) |
		(uint32(b[1]) << 16) |
		(uint32(b[2]) << 8) |
		uint32(b[3])
	return n, nil
}

func (d *Decoder) int32() (int32, error) {
	n, err := d.uint32()
	return int32(n), err
}

func (d *Decoder) uint64() (uint64, error) {
	b, err := d.readN(8)
	if err != nil {
		return 0, err
	}
	n := (uint64(b[0]) << 56) |
		(uint64(b[1]) << 48) |
		(uint64(b[2]) << 40) |
		(uint64(b[3]) << 32) |
		(uint64(b[4]) << 24) |
		(uint64(b[5]) << 16) |
		(uint64(b[6]) << 8) |
		uint64(b[7])
	return n, nil
}

func (d *Decoder) int64() (int64, error) {
	n, err := d.uint64()
	return int64(n), err
}

// DecodeUint64 decodes msgpack int8/16/32/64 and uint8/16/32/64
// into Go uint64.
func (d *Decoder) DecodeUint64() (uint64, error) {
	c, err := d.readCode()
	if err != nil {
		return 0, err
	}
	return d.uint(c)
}

func (d *Decoder) uint(c codes.Code) (uint64, error) {
	if c == codes.Nil {
		return 0, nil
	}
	if codes.IsFixedNum(c) {
		return uint64(int8(c)), nil
	}
	switch c {
	case codes.Uint8:
		n, err := d.uint8()
		return uint64(n), err
	case codes.Int8:
		n, err := d.int8()
		return uint64(n), err
	case codes.Uint16:
		n, err := d.uint16()
		return uint64(n), err
	case codes.Int16:
		n, err := d.int16()
		return uint64(n), err
	case codes.Uint32:
		n, err := d.uint32()
		return uint64(n), err
	case codes.Int32:
		n, err := d.int32()
		return uint64(n), err
	case codes.Uint64, codes.Int64:
		return d.uint64()
	}
	return 0, fmt.Errorf("msgpack: invalid code=%x decoding uint64", c)
}

// DecodeInt64 decodes msgpack int8/16/32/64 and uint8/16/32/64
// into Go int64.
func (d *Decoder) DecodeInt64() (int64, error) {
	c, err := d.readCode()
	if err != nil {
		return 0, err
	}
	return d.int(c)
}

func (d *Decoder) int(c codes.Code) (int64, error) {
	if c == codes.Nil {
		return 0, nil
	}
	if codes.IsFixedNum(c) {
		return int64(int8(c)), nil
	}
	switch c {
	case codes.Uint8:
		n, err := d.uint8()
		return int64(n), err
	case codes.Int8:
		n, err := d.uint8()
		return int64(int8(n)), err
	case codes.Uint16:
		n, err := d.uint16()
		return int64(n), err
	case codes.Int16:
		n, err := d.uint16()
		return int64(int16(n)), err
	case codes.Uint32:
		n, err := d.uint32()
		return int64(n), err
	case codes.Int32:
		n, err := d.uint32()
		return int64(int32(n)), err
	case codes.Uint64, codes.Int64:
		n, err := d.uint64()
		return int64(n), err
	}
	return 0, fmt.Errorf("msgpack: invalid code=%x decoding int64", c)
}

func (d *Decoder) DecodeFloat32() (float32, error) {
	c, err := d.readCode()
	if err != nil {
		return 0, err
	}
	return d.float32(c)
}

func (d *Decoder) float32(c codes.Code) (float32, error) {
	if c == codes.Float {
		n, err := d.uint32()
		if err != nil {
			return 0, err
		}
		return math.Float32frombits(n), nil
	}

	n, err := d.int(c)
	if err != nil {
		return 0, fmt.Errorf("msgpack: invalid code=%x decoding float32", c)
	}
	return float32(n), nil
}

// DecodeFloat64 decodes msgpack float32/64 into Go float64.
func (d *Decoder) DecodeFloat64() (float64, error) {
	c, err := d.readCode()
	if err != nil {
		return 0, err
	}
	return d.float64(c)
}

func (d *Decoder) float64(c codes.Code) (float64, error) {
	switch c {
	case codes.Float:
		n, err := d.float32(c)
		if err != nil {
			return 0, err
		}
		return float64(n), nil
	case codes.Double:
		n, err := d.uint64()
		if err != nil {
			return 0, err
		}
		return math.Float64frombits(n), nil
	}

	n, err := d.int(c)
	if err != nil {
		return 0, fmt.Errorf("msgpack: invalid code=%x decoding float32", c)
	}
	return float64(n), nil
}

func (d *Decoder) DecodeUint() (uint, error) {
	n, err := d.DecodeUint64()
	return uint(n), err
}

func (d *Decoder) DecodeUint8() (uint8, error) {
	n, err := d.DecodeUint64()
	return uint8(n), err
}

func (d *Decoder) DecodeUint16() (uint16, error) {
	n, err := d.DecodeUint64()
	return uint16(n), err
}

func (d *Decoder) DecodeUint32() (uint32, error) {
	n, err := d.DecodeUint64()
	return uint32(n), err
}

func (d *Decoder) DecodeInt() (int, error) {
	n, err := d.DecodeInt64()
	return int(n), err
}

func (d *Decoder) DecodeInt8() (int8, error) {
	n, err := d.DecodeInt64()
	return int8(n), err
}

func (d *Decoder) DecodeInt16() (int16, error) {
	n, err := d.DecodeInt64()
	return int16(n), err
}

func (d *Decoder) DecodeInt32() (int32, error) {
	n, err := d.DecodeInt64()
	return int32(n), err
}

func decodeFloat32Value(d *Decoder, v reflect.Value) error {
	f, err := d.DecodeFloat32()
	if err != nil {
		return err
	}
	v.SetFloat(float64(f))
	return nil
}

func decodeFloat64Value(d *Decoder, v reflect.Value) error {
	f, err := d.DecodeFloat64()
	if err != nil {
		return err
	}
	v.SetFloat(f)
	return nil
}

func decodeInt64Value(d *Decoder, v reflect.Value) error {
	n, err := d.DecodeInt64()
	if err != nil {
		return err
	}
	v.SetInt(n)
	return nil
}

func decodeUint64Value(d *Decoder, v reflect.Value) error {
	n, err := d.DecodeUint64()
	if err != nil {
		return err
	}
	v.SetUint(n)
	return nil
}