// 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).
//
// **Phase A ships only the `static-key` shape.** 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. The refreshable-grant machinery — central rotation, an
// identity guard, a usage reading, refresh-token-stripped delivery — is Phase B, and its verbs are
// named here as optional capabilities (Refresher, Identifier, UsageReader) so the seam exists
// before the code does. The abstraction earns its keep by making the common vendor small, not the
// rare one clever (ADR 0050).
package adapters

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

	"github.com/novox/mesh-control/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
}

// Refresher is implemented only by a refreshable-grant adapter (ADR 0050, Phase B): the
// lease / rotate / publish machinery a manager node runs. A static-key adapter does not implement
// it, and a caller finds its absence by a type assertion.
type Refresher interface {
	Refresh(ctx context.Context, licence string) error
}

// 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. For Phase A the only entry is anthropic as a
// static-key vendor, which is what the lab bed exercises.
//
// TODO(Phase B, ADR 0050): anthropic's real credential is a subscription OAuth grant, so its entry
// becomes RefreshableGrant and a refreshable-grant adapter is registered for it; the static-key
// path for the same vendor's plain API keys moves to a separate `anthropic-api-key` vendor, the
// early second static-key case ADR 0050 names. Static-key vendors are added here as one line each.
var registry = map[string]Shape{
	"anthropic": 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
	default:
		// A vendor registered with a shape this build does not implement yet — the refreshable-grant
		// seam. Said plainly rather than answered with a static-key adapter that would silently
		// mishandle it.
		return nil, fmt.Errorf(
			"the vendor %q needs a %s adapter, which this build does not ship yet", 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 }