it's a start...

internal/iam/repository_principal_role.go

@@ -1,18 +1,85 @@
 package iam
 
-import "context"
+import (
+	"context"
+	"fmt"
 
-func AddPrincipalRoles(ctx context.Context, roleId string, userIds, groupIds []string, opt ...Option) ([]*PrincipalRole, error) {
-	panic("not implemented")
+	"github.com/hashicorp/watchtower/internal/db"
+	"github.com/hashicorp/watchtower/internal/oplog"
+)
+
+func (r *Repository) AddPrincipalRoles(ctx context.Context, roleId string, userIds, groupIds []string, opt ...Option) ([]PrincipalRole, error) {
+	if roleId == "" {
+		return nil, fmt.Errorf("add principal role: missing role id %w", db.ErrInvalidParameter)
+	}
+	if len(userIds) == 0 && len(groupIds) == 0 {
+		return nil, fmt.Errorf("add principal roles: missing either user or groups to add %w", db.ErrInvalidParameter)
+	}
+	newPrincipalRoles := make([]PrincipalRole, 0, len(userIds)+len(groupIds))
+	for _, id := range userIds {
+		userRole, err := NewUserRole(roleId, id)
+		if err != nil {
+			panic(err.Error())
+		}
+		newPrincipalRoles = append(newPrincipalRoles, userRole)
+	}
+	for _, id := range groupIds {
+		grpRole, err := NewGroupRole(roleId, id)
+		if err != nil {
+			panic(err.Error())
+		}
+		newPrincipalRoles = append(newPrincipalRoles, grpRole)
+	}
+	role := allocRole()
+	role.PublicId = roleId
+	scope, err := role.GetScope(ctx, r.reader)
+	if err != nil {
+		return nil, fmt.Errorf("add principal roles: unable to get role %s scope to create metadata: %w", roleId, err)
+	}
+	metadata := oplog.Metadata{
+		"op-type":    []string{oplog.OpType_OP_TYPE_CREATE.String()},
+		"scope-id":   []string{scope.PublicId},
+		"scope-type": []string{scope.Type},
+	}
+
+	resultPrincipalRoles := make([]PrincipalRole, 0, len(userIds)+len(groupIds))
+	_, err = r.writer.DoTx(
+		ctx,
+		db.StdRetryCnt,
+		db.ExpBackoff{},
+		func(w db.Writer) error {
+			for _, principalRole := range newPrincipalRoles {
+				returnedPrincipalRole := principalRole.Clone()
+				err := w.Create(
+					ctx,
+					returnedPrincipalRole,
+					db.WithOplog(r.wrapper, metadata),
+				)
+				if err != nil {
+					if db.IsUniqueError(err) {
+						return fmt.Errorf("add principal role: unable to add principal %s to role %s : %w", principalRole.GetPrincipalId(), roleId, db.ErrNotUnique)
+					}
+					return fmt.Errorf("add principal role: %w when attempting to add principal %s to role %s", err, principalRole.GetPrincipalId(), roleId)
+				}
+				resultPrincipalRoles = append(resultPrincipalRoles, returnedPrincipalRole.(PrincipalRole))
+			}
+			return nil
+		},
+	)
+	if err != nil {
+		return nil, err
+	}
+	return resultPrincipalRoles, nil
 }
 
-func SetPrincipalRoles(ctx context.Context, roleId string, userIds []string, opt ...Option) ([]*PrincipalRole, int, error) {
+func (r *Repository) SetPrincipalRoles(ctx context.Context, roleId string, userIds []string, opt ...Option) ([]*PrincipalRole, int, error) {
 	panic("not implemented")
 }
 
-func LookupPrincipalRoles(ctx context.Context, roleId string) ([]*PrincipalRole, error) {
+func (r *Repository) LookupPrincipalRoles(ctx context.Context, roleId string) ([]*PrincipalRole, error) {
+	// see role_assigned_role.go for query
 	panic("not implemented")
 }
-func DeleteUserRoles(ctx context.Context, roleId string, userIds []string, opt ...Option) (int, error) {
+func (r *Repository) DeleteUserRoles(ctx context.Context, roleId string, userIds []string, opt ...Option) (int, error) {
 	panic("not implemented")
 }