transit/tag/tag.go

package tag

import (
	"encoding/json"
	"net/url"
	"reflect"

	"github.com/mleku/transit/chk"
	"github.com/mleku/transit/errorf"
	"github.com/mleku/transit/id"
	"github.com/mleku/transit/pubkey"
)

type T [2]any

type U struct{ T }

// MarshalTypes is a list of types of tags that are valid. Note that this is all of the types that are
// valid. Additional tag keys may be added in the future but should never be taken away.
var MarshalTypes = map[string]reflect.Type{
	"root":    reflect.TypeOf(&id.I{}),
	"parent":  reflect.TypeOf(&id.I{}),
	"event":   reflect.TypeOf(&id.I{}),
	"user":    reflect.TypeOf(&pubkey.P{}),
	"hashtag": reflect.TypeOf(""),
	"url":     reflect.TypeOf(""),
}

// UnmarshalTypes is a list of types of tags that are valid. Note that this is all of the types that are
// valid. Additional tag keys may be added in the future but should never be taken away.
var UnmarshalTypes = map[string]func() any{
	"root":    func() any { return id.I{} },
	"parent":  func() any { return id.I{} },
	"event":   func() any { return id.I{} },
	"user":    func() any { return pubkey.P{} },
	"hashtag": func() any { return "" },
	"url":     func() any { return "" },
}

func New(key string, val any) (t *U) {
	return &U{T{key, val}}
}

// GetId returns the correctly typed value or the ok value is false.
func (t *U) GetId() (i *id.I, ok bool) { i, ok = t.T[1].(*id.I); return }

// GetPubkey returns the correctly typed value or the ok value is false.
func (t *U) GetPubkey() (p *pubkey.P, ok bool) {
	p, ok = t.T[1].(*pubkey.P)
	return
}

// GetString returns the correctly typed value or the ok value is false.
func (t *U) GetString() (s string, ok bool) {
	s, ok = t.T[1].(string)
	return
}

func (t *U) MarshalJSON() (b []byte, err error) {
	// first value must be a string
	k, ok := t.T[0].(string)
	if !ok {
		err = errorf.E("key must be a string, got '%v'", k)
		return
	}
	// second value must be one of MarshalTypes.
	var found bool
	for _, v := range MarshalTypes {
		if v == reflect.TypeOf(t.T[1]) {
			found = true
			break
		}
	}
	// url is a special case because it needs to be rendered using a stringer as it lacks a
	// json.MarshalJSON implementation.
	if k == "url" {
		var ur string
		if ur, ok = t.T[1].(string); !ok {
			err = errorf.E("url key does not have a value of type string: %v",
				reflect.TypeOf(t.T[1]))
			return
		}
		if _, err = url.Parse(ur); chk.E(err) {
			return
		}
		t.T[1] = ur
	}
	if k == "hashtag" {
		var ht string
		if ht, ok = t.T[1].(string); !ok {
			err = errorf.E("hashtag key does not have a value of type []byte: %v",
				reflect.TypeOf(t.T[1]))
			return
		}
		t.T[1] = ht
	}
	if !found {
		err = errorf.E("tag value is unknown type key: %s value: %v",
			t.T[0], reflect.TypeOf(t.T[1]))
		return
	}
	// marshal array into tag
	tt := t.T
	if b, err = json.Marshal(&tt); chk.E(err) {
		return
	}
	return
}

func (t *U) UnmarshalJSON(b []byte) (err error) {
	var kv []any
	if err = json.Unmarshal(b, &kv); chk.E(err) {
		return
	}
	// we only do the above to get the key name
	var ok bool
	var k string
	if k, ok = kv[0].(string); !ok {
		err = errorf.E("key must be a string, got '%v'", k)
		return
	}
	t.T[0] = k
	var vt func() any
	if vt, ok = UnmarshalTypes[k]; !ok {
		err = errorf.E("unknown key type '%s'", k)
		return
	}
	tt := vt()
	var vs string
	if vs, ok = kv[1].(string); !ok {
		err = errorf.E("value must be a string, got '%v'", k)
		return
	}
	// decode in accordance with the key
	switch ttt := tt.(type) {
	case id.I:
		vs = `"` + vs + `"`
		if err = ttt.UnmarshalJSON([]byte(vs)); chk.E(err) {
			return
		}
		t.T[1] = &ttt
	case pubkey.P:
		vs = `"` + vs + `"`
		if err = ttt.UnmarshalJSON([]byte(vs)); chk.E(err) {
			return
		}
		t.T[1] = &ttt
	case string:
		t.T[1] = vs
	case *url.URL:
		if ttt, err = url.Parse(vs); chk.E(err) {
			return
		}
		t.T[1] = vs
	}
	return
}