package buscompose

import (
	"fmt"

	"github.com/nats-io/nats.go/jetstream"

	"git.novox.be/novox/mesh-sdk/go/catalogue"
)

// A module's own object bucket (novox/hq ADR 0592 §5, §9). The grants part creates it once, create-only, kept with no
// age limit and refusing a new object when full; only its module writes it; another module reads it only through a
// `reads` entry naming it and the owner's trusted config value of the bucket's grant naming that module, read-only, as a
// restricted stream is heard (ADR 0363 §4, §5). The condition when it passes 75 percent of its cap is the grants part's
// (grants.FullCondition).

// ObjectBucket is one object bucket a module owns, as the bus holds it.
type ObjectBucket struct {
	Module string
	Name   string
	// MaxMiB is its cap, catalogue.ObjectsLeastMiB to catalogue.ObjectsMostMiB.
	MaxMiB int
	// Restricted says it names a grant, so a module the owner's trusted config value names reads it.
	Restricted bool
}

// Bucket is its name on the bus, `<module>_<name>` (catalogue.ObjectsBucket).
func (o ObjectBucket) Bucket() string { return catalogue.ObjectsBucket(o.Module, o.Name) }

// Stream is the stream the bus keeps it in.
func (o ObjectBucket) Stream() string { return "OBJ_" + o.Bucket() }

// ObjectsStreamConfig is a module's object bucket as the stream the client library's object store makes of it, with
// the mesh's rule: no age limit, its own cap, and a new object refused when full rather than an old one dropped (ADR
// 0592 §5); file storage and one replica, as a state's.
func ObjectsStreamConfig(o ObjectBucket) jetstream.StreamConfig {
	b := o.Bucket()
	return jetstream.StreamConfig{
		Name: o.Stream(),
		Description: fmt.Sprintf("%s's object bucket %q (novox/hq ADR 0592 §5): written by %s alone, read by the modules its "+
			"grant names, kept with no age limit and at most %d MiB, a new object refused when full", o.Module, o.Name, o.Module, o.MaxMiB),
		Subjects:     []string{"$O." + b + ".C.>", "$O." + b + ".M.>"},
		MaxBytes:     int64(o.MaxMiB) * 1024 * 1024,
		Storage:      jetstream.FileStorage,
		Replicas:     1,
		Discard:      jetstream.DiscardNew,
		AllowRollup:  true,
		AllowDirect:  true,
		MaxMsgs:      -1,
		MaxConsumers: -1,
	}
}

// objectReadGrants is what reading one object bucket needs and nothing more: binding it, a direct get of an object's
// metadata, an ordered consumer on its chunks or its names (a list or a watch), that consumer's deletion and flow
// control. No publish under `$O.`, so no write; no purge.
func objectReadGrants(bucket string) []string {
	stream := "OBJ_" + bucket
	return []string{
		"$JS.API.STREAM.INFO." + stream,
		"$JS.API.DIRECT.GET." + stream + ".>",
		"$JS.API.CONSUMER.CREATE." + stream + ".>",
		"$JS.API.CONSUMER.DELETE." + stream + ".>",
		"$JS.FC." + stream + ".>",
	}
}

// objectGrants is what a principal publishes for its module's own object buckets (written, and a replaced or deleted
// object's chunks purged) and for those it reads (read-only), never their creation, which is the grants part's.
func objectGrants(own, reads []string) []string {
	var out []string
	for _, b := range own {
		if !safeSubject.MatchString(b) {
			continue
		}
		out = append(out, "$O."+b+".>", "$JS.API.STREAM.PURGE.OBJ_"+b)
		out = append(out, objectReadGrants(b)...)
	}
	for _, b := range reads {
		if safeSubject.MatchString(b) {
			out = append(out, objectReadGrants(b)...)
		}
	}
	return out
}

// objectNames is the bus names of a module's own object buckets.
func objectNames(objects []ObjectBucket) []string {
	out := make([]string, 0, len(objects))
	for _, o := range objects {
		out = append(out, o.Bucket())
	}
	return out
}

// writesOwnObjects is a module writing one of its own object buckets (ADR 0592 §5), itself or through the runtime that
// carries it, and nothing of another's.
func writesOwnObjects(p Principal, pattern string) bool {
	switch p.Kind {
	case KindModule:
		for _, b := range p.Objects {
			if pattern == "$O."+b+".>" {
				return true
			}
		}
	case KindNodeTools:
		for _, d := range p.Carries {
			for _, b := range objectNames(d.Objects) {
				if pattern == "$O."+b+".>" {
					return true
				}
			}
		}
	}
	return false
}