From 989f409fd07c4613681029fc3758d2406ef5c7c0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Michael=20Mur=C3=A9?= <batolettre@gmail.com>
Date: Tue, 17 Sep 2024 19:12:31 +0200
Subject: [PATCH] add a pkg to handle meta values

---
 pkg/meta/meta.go | 120 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 120 insertions(+)
 create mode 100644 pkg/meta/meta.go

diff --git a/pkg/meta/meta.go b/pkg/meta/meta.go
new file mode 100644
index 0000000..40f604c
--- /dev/null
+++ b/pkg/meta/meta.go
@@ -0,0 +1,120 @@
+package meta
+
+import (
+	"errors"
+
+	"github.com/ipld/go-ipld-prime"
+	"github.com/ipld/go-ipld-prime/datamodel"
+	"github.com/ipld/go-ipld-prime/node/basicnode"
+)
+
+var ErrNotFound = errors.New("key-value not found in meta")
+
+// Meta is a container for meta key-value pairs in a UCAN token.
+// This also serves as a way to construct the underlying IPLD data with minimum allocations and transformations,
+// while hiding the IPLD complexity from the caller.
+type Meta struct {
+	Keys   []string
+	Values map[string]ipld.Node
+}
+
+// NewMeta constructs a new Meta.
+func NewMeta() *Meta {
+	return &Meta{Values: map[string]ipld.Node{}}
+}
+
+// GetBool retrieves a value as a bool.
+// Returns ErrNotFound if the given key is missing.
+// Returns datamodel.ErrWrongKind if the value has the wrong type.
+func (m Meta) GetBool(key string) (bool, error) {
+	v, ok := m.Values[key]
+	if !ok {
+		return false, ErrNotFound
+	}
+	return v.AsBool()
+}
+
+// GetString retrieves a value as a string.
+// Returns ErrNotFound if the given key is missing.
+// Returns datamodel.ErrWrongKind if the value has the wrong type.
+func (m Meta) GetString(key string) (string, error) {
+	v, ok := m.Values[key]
+	if !ok {
+		return "", ErrNotFound
+	}
+	return v.AsString()
+}
+
+// GetInt64 retrieves a value as an int64.
+// Returns ErrNotFound if the given key is missing.
+// Returns datamodel.ErrWrongKind if the value has the wrong type.
+func (m Meta) GetInt64(key string) (int64, error) {
+	v, ok := m.Values[key]
+	if !ok {
+		return 0, ErrNotFound
+	}
+	return v.AsInt()
+}
+
+// GetFloat64 retrieves a value as a float64.
+// Returns ErrNotFound if the given key is missing.
+// Returns datamodel.ErrWrongKind if the value has the wrong type.
+func (m Meta) GetFloat64(key string) (float64, error) {
+	v, ok := m.Values[key]
+	if !ok {
+		return 0, ErrNotFound
+	}
+	return v.AsFloat()
+}
+
+// GetBytes retrieves a value as a []byte.
+// Returns ErrNotFound if the given key is missing.
+// Returns datamodel.ErrWrongKind if the value has the wrong type.
+func (m Meta) GetBytes(key string) ([]byte, error) {
+	v, ok := m.Values[key]
+	if !ok {
+		return nil, ErrNotFound
+	}
+	return v.AsBytes()
+}
+
+// GetNode retrieves a value as a raw IPLD node.
+// Returns ErrNotFound if the given key is missing.
+// Returns datamodel.ErrWrongKind if the value has the wrong type.
+func (m Meta) GetNode(key string) (ipld.Node, error) {
+	v, ok := m.Values[key]
+	if !ok {
+		return nil, ErrNotFound
+	}
+	return v, nil
+}
+
+// Add adds a key/value pair in the meta set.
+// Accepted types for the value are: bool, string, int, int32, int64, []byte,
+// and ipld.Node.
+func (m Meta) Add(key string, val any) error {
+	switch val := val.(type) {
+	case bool:
+		m.Values[key] = basicnode.NewBool(val)
+	case string:
+		m.Values[key] = basicnode.NewString(val)
+	case int:
+		m.Values[key] = basicnode.NewInt(int64(val))
+	case int32:
+		m.Values[key] = basicnode.NewInt(int64(val))
+	case int64:
+		m.Values[key] = basicnode.NewInt(val)
+	case float32:
+		m.Values[key] = basicnode.NewFloat(float64(val))
+	case float64:
+		m.Values[key] = basicnode.NewFloat(val)
+	case []byte:
+		m.Values[key] = basicnode.NewBytes(val)
+	case datamodel.Node:
+		m.Values[key] = val
+	default:
+		panic("invalid value type")
+	}
+	m.Keys = append(m.Keys, key)
+	return nil
+}