package bus

import (
	"context"
	"errors"
	"fmt"
	"io"

	"git.novox.be/novox/mesh-sdk/go/buscalls"
	"github.com/nats-io/nats.go/jetstream"
)

// The bus side of a bundle's put and get sessions (design 47 G §518, A-21, A-25): a put written into the module's object
// store as its chunks arrive and a get read out of it as they are asked, through the store's own chunking, so no more than
// one chunk is held in memory. The session itself is the runtime's (internal/runtime/sessions.go).

// ObjectsPutStream stores the object r.Name of the module's object store r.Objects from in, read to its end, with the
// put's description (A-25); it answers once the object is sealed. A read error of in drops the object: nothing is left.
func (c *Conn) ObjectsPutStream(ctx context.Context, module string, r buscalls.ObjectsNameRequest, description string, in io.Reader) (buscalls.ObjectInfo, error) {
	if r.Name == "" {
		return buscalls.ObjectInfo{}, errors.New("an object is put under a name")
	}
	obs, _, err := c.objectStore(ctx, module, r.Objects)
	if err != nil {
		return buscalls.ObjectInfo{}, err
	}
	info, err := obs.Put(ctx, jetstream.ObjectMeta{Name: r.Name, Description: description}, in)
	if err != nil {
		_ = obs.Delete(context.WithoutCancel(ctx), r.Name)
		return buscalls.ObjectInfo{}, err
	}
	return objectInfoOf(info), nil
}

// ObjectsOpen is one object of the module's object store as a reader of its bytes beside its info; found is false when there
// is none. The caller closes the reader.
func (c *Conn) ObjectsOpen(ctx context.Context, module string, r buscalls.ObjectsNameRequest) (info buscalls.ObjectInfo, rd io.ReadCloser, found bool, err error) {
	obs, _, err := c.objectStore(ctx, module, r.Objects)
	if err != nil {
		return info, nil, false, err
	}
	res, err := obs.Get(ctx, r.Name)
	if errors.Is(err, jetstream.ErrObjectNotFound) {
		return info, nil, false, nil
	}
	if err != nil {
		return info, nil, false, err
	}
	i, err := res.Info()
	if err != nil {
		res.Close()
		return info, nil, false, err
	}
	return objectInfoOf(i), res, true, nil
}

// SentOpen is a sent object, read by its reference as SentGet reads it, as a reader of its bytes beside its info.
func (c *Conn) SentOpen(ctx context.Context, r buscalls.ObjectsSentGetRequest) (buscalls.ObjectInfo, io.ReadCloser, error) {
	obs, err := c.sentStore(ctx, r)
	if err != nil {
		return buscalls.ObjectInfo{}, nil, err
	}
	res, err := obs.Get(ctx, r.Object)
	if errors.Is(err, jetstream.ErrObjectNotFound) {
		return buscalls.ObjectInfo{}, nil, fmt.Errorf("the sent object %s is not in %s: it is kept 7 days, then expires", r.Object, r.Store)
	}
	if err != nil {
		return buscalls.ObjectInfo{}, nil, fmt.Errorf("the sent object %s of %s: %w", r.Object, r.Store, err)
	}
	i, err := res.Info()
	if err != nil {
		res.Close()
		return buscalls.ObjectInfo{}, nil, err
	}
	return objectInfoOf(i), res, nil
}