delegation: make the examples more examply, less testy

pkg/meta/meta.go

@@ -4,10 +4,12 @@ import (
 	"errors"
 	"fmt"
 	"reflect"
+	"strings"
 
 	"github.com/ipld/go-ipld-prime"
 	"github.com/ipld/go-ipld-prime/datamodel"
 	"github.com/ipld/go-ipld-prime/node/basicnode"
+	"github.com/ipld/go-ipld-prime/printer"
 )
 
 var ErrUnsupported = errors.New("failure adding unsupported type to meta")
@@ -139,6 +141,25 @@ func (m *Meta) Equals(other *Meta) bool {
 	return true
 }
 
+func (m *Meta) String() string {
+	buf := strings.Builder{}
+	buf.WriteString("{")
+
+	var i int
+	for key, node := range m.Values {
+		if i > 0 {
+			buf.WriteString(", ")
+		}
+		i++
+		buf.WriteString(key)
+		buf.WriteString(":")
+		buf.WriteString(printer.Sprint(node))
+	}
+
+	buf.WriteString("}")
+	return buf.String()
+}
+
 func fqtn(val any) string {
 	var name string
 

pkg/policy/policy.go

@@ -3,7 +3,11 @@ package policy
 // https://github.com/ucan-wg/delegation/blob/4094d5878b58f5d35055a3b93fccda0b8329ebae/README.md#policy
 
 import (
+	"fmt"
+	"strings"
+
 	"github.com/ipld/go-ipld-prime"
+	"github.com/ipld/go-ipld-prime/codec/dagjson"
 
 	"github.com/ucan-wg/go-ucan/pkg/policy/selector"
 )
@@ -24,8 +28,20 @@ const (
 
 type Policy []Statement
 
+func (p Policy) String() string {
+	if len(p) == 0 {
+		return "[]"
+	}
+	childs := make([]string, len(p))
+	for i, statement := range p {
+		childs[i] = strings.ReplaceAll(statement.String(), "\n", "\n  ")
+	}
+	return fmt.Sprintf("[\n  %s\n]", strings.Join(childs, ",\n  "))
+}
+
 type Statement interface {
 	Kind() string
+	String() string
 }
 
 type equality struct {
@@ -38,6 +54,14 @@ func (e equality) Kind() string {
 	return e.kind
 }
 
+func (e equality) String() string {
+	child, err := ipld.Encode(e.value, dagjson.Encode)
+	if err != nil {
+		return "ERROR: INVALID VALUE"
+	}
+	return fmt.Sprintf(`["%s", "%s", %s]`, e.kind, e.selector, strings.ReplaceAll(string(child), "\n", "\n  "))
+}
+
 func Equal(selector selector.Selector, value ipld.Node) Statement {
 	return equality{kind: KindEqual, selector: selector, value: value}
 }
@@ -66,6 +90,11 @@ func (n negation) Kind() string {
 	return KindNot
 }
 
+func (n negation) String() string {
+	child := n.statement.String()
+	return fmt.Sprintf(`["%s", "%s"]`, n.Kind(), strings.ReplaceAll(child, "\n", "\n  "))
+}
+
 func Not(stmt Statement) Statement {
 	return negation{statement: stmt}
 }
@@ -79,6 +108,14 @@ func (c connective) Kind() string {
 	return c.kind
 }
 
+func (c connective) String() string {
+	childs := make([]string, len(c.statements))
+	for i, statement := range c.statements {
+		childs[i] = strings.ReplaceAll(statement.String(), "\n", "\n  ")
+	}
+	return fmt.Sprintf("[\"%s\", [\n  %s]]\n", c.kind, strings.Join(childs, ",\n  "))
+}
+
 func And(stmts ...Statement) Statement {
 	return connective{kind: KindAnd, statements: stmts}
 }
@@ -96,6 +133,10 @@ func (n wildcard) Kind() string {
 	return KindLike
 }
 
+func (n wildcard) String() string {
+	return fmt.Sprintf(`["%s", "%s", "%s"]`, n.Kind(), n.selector, n.pattern)
+}
+
 func Like(selector selector.Selector, pattern string) (Statement, error) {
 	g, err := parseGlob(pattern)
 	if err != nil {
@@ -105,6 +146,14 @@ func Like(selector selector.Selector, pattern string) (Statement, error) {
 	return wildcard{selector: selector, pattern: g}, nil
 }
 
+func MustLike(selector selector.Selector, pattern string) Statement {
+	g, err := Like(selector, pattern)
+	if err != nil {
+		panic(err)
+	}
+	return g
+}
+
 type quantifier struct {
 	kind      string
 	selector  selector.Selector
@@ -115,6 +164,11 @@ func (n quantifier) Kind() string {
 	return n.kind
 }
 
+func (n quantifier) String() string {
+	child := n.statement.String()
+	return fmt.Sprintf("[\"%s\", \"%s\",\n  %s]", n.Kind(), n.selector, strings.ReplaceAll(child, "\n", "\n  "))
+}
+
 func All(selector selector.Selector, statement Statement) Statement {
 	return quantifier{kind: KindAll, selector: selector, statement: statement}
 }

pkg/policy/selector/parsing.go

@@ -27,7 +27,7 @@ func Parse(str string) (Selector, error) {
 			if len(sel) > 0 && sel[len(sel)-1].Identity() {
 				return nil, newParseError("selector contains unsupported recursive descent segment: '..'", str, col, tok)
 			}
-			sel = append(sel, Identity)
+			sel = append(sel, segment{".", true, false, false, nil, "", 0})
 		case "[]":
 			sel = append(sel, segment{tok, false, opt, true, nil, "", 0})
 		default:

pkg/policy/selector/selector.go

@@ -23,7 +23,7 @@ func (s Selector) String() string {
 	return res.String()
 }
 
-var Identity = segment{".", true, false, false, nil, "", 0}
+var Identity = MustParse(".")
 
 var (
 	indexRegex = regexp.MustCompile(`^-?\d+$`)