package skillpack

import "time"

// Subscription is a host's persisted "I track this pack, pinned here" record. It
// is metadata only — the pinned pack's bytes live in a PackCache keyed by
// PinnedDigest. A subscription is only ever advanced to new content by an
// explicit Apply (see Syncer): a sync records a PendingDigest, it never moves
// the pin. That is the supply-chain guard — a compromised or careless upstream
// cannot change what an agent runs without a human re-pin.
type Subscription struct {
	// ID is a stable host-assigned identifier.
	ID string
	// Name is the pack's manifest name (unique per host); what an agent lists in
	// its SkillPacks and what skill_use receives.
	Name string
	// Description is the pinned manifest's description, cached so the catalog
	// renders without opening the PackCache.
	Description string

	// Source coordinates.
	SourceKind string // "dir" | "git"
	SourceURL  string // dir path or git URL
	Subpath    string // git subpath, if any
	// TrackRef is the git commit-ish the host follows (branch/tag/SHA); empty =
	// default branch. Sync fetches THIS; the pin only moves on Apply.
	TrackRef string

	// Pinned* describe the currently-active content.
	PinnedDigest    string // content digest = PackCache key + change signal
	PinnedSourceRef string // source's resolved ref (git SHA) — provenance
	PinnedAt        time.Time
	PinnedBy        string

	// Pending* describe an update a sync found but has NOT applied. Empty
	// PendingDigest = no pending update. A pending digest equal to the pinned
	// one is impossible by construction (Syncer clears it).
	PendingDigest    string
	PendingSourceRef string
	PendingAt        time.Time

	// Enabled lets a host keep a subscription but deactivate it without
	// deleting the pin/history.
	Enabled bool
}

// HasPending reports whether a sync found an unapplied update.
func (s *Subscription) HasPending() bool {
	return s.PendingDigest != "" && s.PendingDigest != s.PinnedDigest
}

// pinTo advances the active pin to a fetched pack and clears any pending state.
// Used by initial pin and by Apply.
func (s *Subscription) pinTo(p *Pack, sourceRef, by string, now time.Time) {
	s.Name = p.Manifest.Name
	s.Description = p.Manifest.Description
	s.PinnedDigest = p.Digest
	s.PinnedSourceRef = sourceRef
	s.PinnedAt = now
	s.PinnedBy = by
	s.PendingDigest = ""
	s.PendingSourceRef = ""
	s.PendingAt = time.Time{}
}