package datagen

import (
	"bytes"
	"crypto/sha256"
	"encoding/hex"
	"io"
)

// Payload represents arbitrary data to be packed into S3 or native object.
// Implementations could be thread-unsafe.
type Payload interface {
	// Reader returns io.Reader instance to read the payload.
	// Must not be called twice.
	Reader() io.Reader
	// Bytes is a helper which reads all data from Reader() into slice.
	// The sole purpose of this method is to simplify HTTP scenario,
	// where all payload needs to be read and wrapped.
	Bytes() []byte
	// Size returns payload size, which is equal to the total amount of data
	// that could be read from the Reader().
	Size() int
	// Hash returns payload sha256 hash. Must be called after all data is read from the reader.
	Hash() string
}

type bytesPayload struct {
	data []byte
}

func (p *bytesPayload) Reader() io.Reader {
	return bytes.NewReader(p.data)
}

func (p *bytesPayload) Size() int {
	return len(p.data)
}

func (p *bytesPayload) Hash() string {
	h := sha256.Sum256(p.data[:])
	return hex.EncodeToString(h[:])
}

func (p *bytesPayload) Bytes() []byte {
	return p.data
}

func NewFixedPayload(data []byte) Payload {
	return &bytesPayload{data: data}
}