package correlation

import (
	"context"
	"encoding/hex"
)

const Key string = "correlation_id"

var Empty CorrelationID = CorrelationID{0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}

// Correlation ID is a byte array of length 16
type CorrelationID []byte

func (ci CorrelationID) String() string {
	if ci == nil {
		return hex.EncodeToString(Empty)
	}
	return hex.EncodeToString(ci)
}

func FromContext(ctx context.Context) CorrelationID {
	if v := ctx.Value("correlation_id"); v != nil {
		if c, ok := v.(CorrelationID); ok {
			return c
		}
	}
	return nil
}

type Sequencer interface {
	Next() []byte
}

type Generator struct {
	seq Sequencer
}

func NewGenerator(seq Sequencer) *Generator {
	return &Generator{
		seq: seq,
	}
}

func (g *Generator) Next() CorrelationID {
	return CorrelationID(g.seq.Next())
}