auth/rbac/claims_provider.go

package rbac

import (
	"context"
	"encoding/json"

	"code.nochebuena.dev/einherjar/contracts/security"
)

var _ security.PermissionProvider = (*claimsPermissionProvider)(nil)

type claimsPermissionProvider struct {
	claimsKey string
	getClaims func(context.Context) map[string]any
}

// NewClaimsPermissionProvider returns a PermissionProvider that reads
// pre-computed permission bitmasks from JWT claims stored in context.
//
// claimsKey is the top-level claim key whose value is a map[resource]int64.
// Falls back to wildcard key "*" if the specific resource is absent.
// Zero DB calls — fastest permission resolution for read-heavy APIs.
//
// getClaims is the function used to retrieve claims from context.
// Pass authmw.GetClaims when using the authmw middleware chain.
//
// Flat claims format: claims["perms"]["orders"] = 7
// For multi-tenant permission isolation, use [NewCachedPermissionProvider]
// wrapping a DB lookup — it automatically scopes cache keys per tenant.
func NewClaimsPermissionProvider(claimsKey string, getClaims func(context.Context) map[string]any) security.PermissionProvider {
	return &claimsPermissionProvider{claimsKey: claimsKey, getClaims: getClaims}
}

func (p *claimsPermissionProvider) ResolveMask(ctx context.Context, _, resource string) (security.PermissionMask, error) {
	claims := p.getClaims(ctx)
	if claims == nil {
		return 0, nil
	}

	raw, ok := claims[p.claimsKey]
	if !ok {
		return 0, nil
	}

	resourceMap, ok := raw.(map[string]any)
	if !ok {
		return 0, nil
	}

	mask := extractMask(resourceMap, resource)
	if mask == 0 {
		mask = extractMask(resourceMap, "*")
	}
	return security.PermissionMask(mask), nil
}

func extractMask(m map[string]any, key string) int64 {
	v, ok := m[key]
	if !ok {
		return 0
	}
	switch n := v.(type) {
	case int64:
		return n
	case float64:
		return int64(n)
	case json.Number:
		i, err := n.Int64()
		if err != nil {
			return 0
		}
		return i
	}
	return 0
}