// Package adapters is the per-vendor lifecycle a licence needs, selected by the licence's vendor.
//
// novox/hq ADR 0050: model access is one consumer-facing, vendor-blind provision, and *a vendor is
// an adapter* keyed by `licence.vendor`. A consumer names `model-access` and never a vendor; which
// vendor answers, and the lifecycle that vendor's credential needs, lives here — exactly as
// `public-dns` is one neutral interface answered by registrar-scoped providers (ADR 0044).
//
// **Two shapes.** A `static-key` vendor implements almost nothing: the credential is an
// operator-supplied value, sealed to each holder by the generic anonymous box (ADR 0024) and
// delivered unchanged. A `refreshable-grant` vendor carries the bounded carve-out — a manager node
// holds the refresh token encrypted at rest, access tokens are still sealed per holder, and the
// refresh token is never in a holder's delivery. This package holds the generic half of both. The
// vendor-specific half of a refresh — the actual OAuth call against a vendor's endpoint — is a
// VendorRefresher plugged in from outside (novox/hq ADR 0050, Phase C); this build ships none, and
// a refresh on a vendor with nothing plugged in is refused in as many words rather than pretended.
// The abstraction earns its keep by making the common vendor small, not the rare one clever.
package adapters

import (
	"context"
	"fmt"
	"sort"
	"strings"
	"sync"

	"github.com/novox/mesh-controller/internal/secrets"
)

// Shape is how a vendor's credential behaves, and the switch the ADR 0050 carve-out turns on.
type Shape string

const (
	// StaticKey is an operator-supplied value with nothing to rotate. The full "the mesh cannot
	// read what it stores" guarantee holds: accept seals it and discards the plaintext.
	StaticKey Shape = "static-key"
	// RefreshableGrant is an OAuth-style grant a manager node refreshes centrally (ADR 0050,
	// Phase B). It carries the one bounded relaxation of that guarantee. No adapter of this shape
	// ships in Phase A.
	RefreshableGrant Shape = "refreshable-grant"
)

// Adapter is a vendor's lifecycle, selected by a licence's vendor.
//
// Only these verbs are required, and they are all a static-key vendor needs: what shape it is, how
// a supplied value is sealed, and what a consumer is delivered. The optional capabilities below are
// found by type assertion, so a static-key adapter simply does not implement them.
type Adapter interface {
	// Vendor is the name a licence's `vendor` field carries to select this adapter.
	Vendor() string
	// Shape is static-key or refreshable-grant.
	Shape() Shape
	// Accept takes an operator-supplied credential and seals it to one holder — the `accept` verb
	// ADR 0024 defines. For a static key this is the generic seal, unchanged.
	Accept(value, consumerKey, providerKey string) (secrets.Sealed, error)
	// Deliver is the credential value a consumer receives. For a sealed static key it is the sealed
	// blob unchanged: the mesh never unseals it, only the holding node's private key can. A
	// refreshable-grant adapter (Phase B) strips the refresh token here.
	Deliver(sealed string) string
}

// RefreshInput is what producing a new access token needs, and all a refresh is given.
//
// It carries the refresh token **only as its sealed blob** — the caller (the control plane) never
// holds the refresh token in the clear, because it cannot open the box. Opening it, and the vendor
// call that follows, happen where the manager node's private key is (ADR 0050, Phase C).
type RefreshInput struct {
	Licence string
	// Manager is the node that holds the refresh token readably — the one place the box opens.
	Manager string
	// Sealed is the refresh token as an anonymous sealed box to the manager's key. Opaque to the
	// control plane; openable only by the manager node's private half.
	Sealed string
	// ManagerKey is the manager's public sealing key the token was sealed to.
	ManagerKey string
}

// RefreshResult is what a refresh produced: a new access token to seal per holder, and — only if the
// vendor rotated it — the refresh token re-sealed to the manager, ready to replace the stored blob.
type RefreshResult struct {
	// AccessToken is the new access token, in the clear. The mesh seals it per holder and discards
	// it, exactly as it does an accepted key. It is never the refresh token.
	AccessToken string
	// NewSealed is the refresh token re-sealed to the manager node, present only when the vendor
	// rotated the refresh token too. Empty leaves the stored blob untouched. Already sealed, so the
	// control plane stores it without ever seeing the refresh token in the clear.
	NewSealed string
	// NewManagerKey is the key NewSealed was sealed to, carried with it.
	NewManagerKey string
}

// Refresher is implemented only by a refreshable-grant adapter (ADR 0050): the vendor-neutral half
// of the lease / rotate / publish machinery. A static-key adapter does not implement it, and a
// caller finds its absence by a type assertion — which is exactly what gates the carve-out to
// refreshable-grant vendors.
type Refresher interface {
	Refresh(ctx context.Context, in RefreshInput) (RefreshResult, error)
}

// VendorRefresher is the vendor-specific half, plugged in from outside (ADR 0050, Phase C): given a
// refresh, it opens the at-rest envelope with the manager node's key, calls the vendor's endpoint,
// and returns the new access token (and a re-sealed refresh token if the vendor rotated it). It is
// the one component that reads a refresh token in the clear, and in production it runs where the
// manager node's private key is. This build registers none; Anthropic's OAuth refresh is Phase C.
type VendorRefresher interface {
	Refresh(ctx context.Context, in RefreshInput) (RefreshResult, error)
}

// refreshers is what has been plugged in, keyed by vendor. Empty in this build.
var refreshers struct {
	sync.RWMutex
	byVendor map[string]VendorRefresher
}

// RegisterRefresher plugs a vendor's real refresh in (ADR 0050, Phase C), or a fake in a test. The
// generic refreshable-grant adapter for that vendor then delegates to it. Registering nothing leaves
// the seam empty, and a refresh on that vendor is refused with a message that names Phase C rather
// than failing obscurely.
func RegisterRefresher(vendor string, r VendorRefresher) {
	refreshers.Lock()
	defer refreshers.Unlock()
	if refreshers.byVendor == nil {
		refreshers.byVendor = map[string]VendorRefresher{}
	}
	refreshers.byVendor[vendor] = r
}

func refresherFor(vendor string) VendorRefresher {
	refreshers.RLock()
	defer refreshers.RUnlock()
	return refreshers.byVendor[vendor]
}

// Identifier is the mis-binding guard (ADR 0050, Phase B): a vendor whose credential carries an
// account identity worth checking implements it. A static-key adapter does not.
type Identifier interface {
	Identity(credential string) (string, error)
}

// UsageReader is a vendor's usage reading (ADR 0050 / ADR 0054, Phase B), mapped to the common
// normalised grain. A static-key adapter does not implement it.
type UsageReader interface {
	Usage(ctx context.Context, licence string) ([]UsageRow, error)
}

// UsageRow is the vendor-neutral usage grain ADR 0054 fixes: the metric is vendor-defined and no
// common unit is forced. Defined here as the Phase-B seam; nothing in Phase A produces one.
type UsageRow struct {
	Licence  string
	Consumer string
	Period   string
	Metric   string
	Value    float64
	// Raw is the vendor's own response, kept so a reading can be re-derived if the normalisation is
	// later found wrong.
	Raw []byte
}

// registry maps a vendor name to the shape its adapter has.
//
// The single place a vendor is taught to the mesh. anthropic's real credential is a subscription
// OAuth grant, so it is the first `refreshable-grant` vendor; `anthropic-api-key` is the same
// company's plain API keys, the early second `static-key` case ADR 0050 names — it exercises the
// whole path with the carve-out switched off. Static-key vendors are added here as one line each.
//
// TODO(Phase C, ADR 0050): register anthropic's real VendorRefresher — the OAuth refresh against the
// vendor's endpoint — with RegisterRefresher. Until then a refresh on it is refused, naming Phase C.
var registry = map[string]Shape{
	"anthropic":         RefreshableGrant,
	"anthropic-api-key": StaticKey,
	"openai":            StaticKey,
}

// For returns the adapter for a vendor, refusing an unknown one clearly.
//
// The refusal names what this mesh does know, because a vendor typo and a vendor this build has no
// adapter for are the same symptom to whoever hits it, and the list is the difference between fixing
// the name and filing a bug.
func For(vendor string) (Adapter, error) {
	shape, known := registry[vendor]
	if !known {
		return nil, fmt.Errorf(
			"this mesh has no adapter for the vendor %q; it knows: %s",
			vendor, strings.Join(vendors(), ", "))
	}
	switch shape {
	case StaticKey:
		return staticKey{vendor: vendor}, nil
	case RefreshableGrant:
		// The generic refreshable-grant adapter, carrying whatever VendorRefresher has been plugged
		// in for this vendor — nil in this build, which a refresh reports rather than hides.
		return refreshableGrant{vendor: vendor, refresher: refresherFor(vendor)}, nil
	default:
		// A shape this build has no adapter for at all. Said plainly rather than answered with an
		// adapter that would silently mishandle it.
		return nil, fmt.Errorf(
			"the vendor %q has shape %q, which this build has no adapter for", vendor, shape)
	}
}

// vendors is every vendor this mesh has an adapter for, sorted — what a refusal lists.
func vendors() []string {
	out := make([]string, 0, len(registry))
	for v := range registry {
		out = append(out, v)
	}
	sort.Strings(out)
	return out
}

// staticKey is the adapter for a vendor whose credential is a single operator-supplied value.
//
// It holds no vendor-specific logic, and that is the point: accept is the generic seal, deliver is
// the value, and refresh / identity / usage are not implemented at all. It is one type shared by
// every static-key vendor rather than one per vendor, because the sealing is vendor-independent.
type staticKey struct{ vendor string }

func (s staticKey) Vendor() string { return s.vendor }
func (s staticKey) Shape() Shape   { return StaticKey }

// Accept is the generic anonymous-box seal (ADR 0024): a static key needs nothing vendor-specific.
func (s staticKey) Accept(value, consumerKey, providerKey string) (secrets.Sealed, error) {
	return secrets.Accept(value, consumerKey, providerKey)
}

// Deliver hands the consumer the credential value. For a sealed static key that is the sealed blob
// unchanged — there is no vendor step between the store and the node, and the mesh never sees the
// plaintext.
func (s staticKey) Deliver(sealed string) string { return sealed }

// refreshableGrant is the adapter for a vendor whose credential is an OAuth-style grant a manager
// node refreshes centrally (novox/hq ADR 0050). It is vendor-neutral: the generic half — the shape
// that gates the carve-out, the per-holder seal of an access token, delivery that carries only an
// access token, and the dispatch of a refresh to a plugged-in VendorRefresher — lives here; the
// vendor's actual OAuth call is the injected refresher.
//
// **What makes this the carve-out and not a second static key.** The refresh token never touches
// this adapter. It lives in the licences context's own refresh_grant store, keyed by licence, sealed
// to the manager node (secrets.Seal) and delivered to the manager holder alone. What Accept seals and
// Deliver hands out to a CONSUMER is the ACCESS token, per holder, exactly as a static key's value is
// — so "a consumer is never delivered the refresh token" is structural here: a consumer's row never
// holds it, because the refresh token is a different holder's credential entirely.
type refreshableGrant struct {
	vendor    string
	refresher VendorRefresher
}

func (r refreshableGrant) Vendor() string { return r.vendor }
func (r refreshableGrant) Shape() Shape   { return RefreshableGrant }

// Accept seals an access token to one holder — the generic anonymous-box seal, the same as a static
// key. The refresh token is not accepted here: it is adopted onto the manager node and kept in the
// at-rest store (ADR 0050, Phase C), never sealed per holder.
func (r refreshableGrant) Accept(value, consumerKey, providerKey string) (secrets.Sealed, error) {
	return secrets.Accept(value, consumerKey, providerKey)
}

// Deliver hands the consumer its sealed ACCESS token, unchanged. There is no refresh token to strip
// because a holder's row never held one — the stripping is in the shape of the store, not a step
// here.
func (r refreshableGrant) Deliver(sealed string) string { return sealed }

// Refresh is the vendor-neutral half of the lease/rotate/publish machinery: it dispatches to the
// vendor's plugged-in refresher and returns what that produced. The lease, the per-holder reseal and
// the publish are the licences context's (ADR 0050, Phase B); the OAuth call is the vendor's
// (Phase C). With nothing plugged in, it refuses in a way that names why.
func (r refreshableGrant) Refresh(ctx context.Context, in RefreshInput) (RefreshResult, error) {
	if r.refresher == nil {
		return RefreshResult{}, fmt.Errorf(
			"the vendor %q is refreshable-grant but has no refresher plugged in, so its grant "+
				"cannot be refreshed in this build (novox/hq ADR 0050, Phase C)", r.vendor)
	}
	return r.refresher.Refresh(ctx, in)
}