// Package session provides functions for sessions of incoming requests.
package session // import "v2ray.com/core/common/session"

import (
	"context"
	"math/rand"

	"v2ray.com/core/common/errors"
)

// ID of a session.
type ID uint32

// NewID generates a new ID. The generated ID is high likely to be unique, but not cryptographically secure.
// The generated ID will never be 0.
func NewID() ID {
	for {
		id := ID(rand.Uint32())
		if id != 0 {
			return id
		}
	}
}

type sessionKey int

const (
	idSessionKey sessionKey = iota
)

// ContextWithID returns a new context with the given ID.
func ContextWithID(ctx context.Context, id ID) context.Context {
	return context.WithValue(ctx, idSessionKey, id)
}

// IDFromContext returns ID in this context, or 0 if not contained.
func IDFromContext(ctx context.Context) ID {
	if id, ok := ctx.Value(idSessionKey).(ID); ok {
		return id
	}
	return 0
}

func ExportIDToError(ctx context.Context) errors.ExportOption {
	id := IDFromContext(ctx)
	return func(h *errors.ExportOptionHolder) {
		h.SessionID = uint32(id)
	}
}
