feat(cip27): add model for CIP-27 (#95)

Signed-off-by: Ales Verbic <verbotenj@blinklabs.io>

cip27.go

@@ -0,0 +1,170 @@
+// Copyright 2024 Blink Labs Software
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package models
+
+import (
+	"encoding/json"
+	"errors"
+	"strconv"
+
+	"github.com/go-playground/validator/v10"
+)
+
+// Cip27Metadata is the top-level container for royalties data under the "777" tag.
+type Cip27Metadata struct {
+	Num777 Cip777 `cbor:"777,keyasint" json:"777" validate:"required"`
+}
+
+// Cip777 represents the actual royalty info. It handles both modern "rate" and legacy "pct."
+type Cip777 struct {
+	// Internally, Rate is our main numeric string (e.g., "0.20").
+	Rate string `json:"-"`
+
+	// We store the raw strings for either "pct" or "rate."
+	// We only expose "rate" in the final JSON.
+	pctRaw  *string
+	rateRaw *string
+
+	// 'addr' can be either a string or array of strings, so we wrap it in AddrField.
+	Addr AddrField `cbor:"addr" json:"addr" validate:"required"`
+}
+
+func (c *Cip27Metadata) UnmarshalJSON(data []byte) error {
+	// Unmarshal into a map so we can check for "777" explicitly.
+	var raw map[string]json.RawMessage
+	if err := json.Unmarshal(data, &raw); err != nil {
+		return err
+	}
+
+	// Verify the "777" key exists at the top level.
+	val, ok := raw["777"]
+	if !ok {
+		return errors.New(`missing "777" key in CIP-27 metadata`)
+	}
+
+	// Unmarshal the contents of "777" into c.Num777.
+	if err := json.Unmarshal(val, &c.Num777); err != nil {
+		return err
+	}
+
+	// Run validation (so any "required" or numeric checks fail immediately).
+	if err := c.Validate(); err != nil {
+		return err
+	}
+	return nil
+}
+
+// UnmarshalJSON checks which field ("rate" or "pct") is present, giving precedence to "rate."
+func (c *Cip777) UnmarshalJSON(data []byte) error {
+	// Temporary structure for decoding both fields plus 'addr.'
+	var raw struct {
+		Pct  *string   `json:"pct"`
+		Rate *string   `json:"rate"`
+		Addr AddrField `json:"addr"`
+	}
+
+	if err := json.Unmarshal(data, &raw); err != nil {
+		return err
+	}
+
+	switch {
+	case raw.Rate != nil:
+		c.Rate = *raw.Rate
+	case raw.Pct != nil:
+		c.Rate = *raw.Pct
+	default:
+		return errors.New("missing both 'rate' and 'pct' fields")
+	}
+
+	c.pctRaw = raw.Pct
+	c.rateRaw = raw.Rate
+	c.Addr = raw.Addr
+	return nil
+}
+
+// MarshalJSON outputs "rate" as our canonical field.
+func (c Cip777) MarshalJSON() ([]byte, error) {
+	// We only expose "rate" in the final JSON.
+	var out struct {
+		Rate string    `json:"rate"`
+		Addr AddrField `json:"addr"`
+	}
+	out.Rate = c.Rate
+	out.Addr = c.Addr
+	return json.Marshal(out)
+}
+
+// AddrField supports either a single string or an array of strings in JSON.
+type AddrField struct {
+	Addresses []string
+}
+
+// UnmarshalJSON attempts to parse 'addr' as a single string; if that fails, it tries an array of strings.
+func (af *AddrField) UnmarshalJSON(data []byte) error {
+	var single string
+	if err := json.Unmarshal(data, &single); err == nil {
+		af.Addresses = []string{single}
+		return nil
+	}
+
+	var arr []string
+	if err := json.Unmarshal(data, &arr); err == nil {
+		af.Addresses = arr
+		return nil
+	}
+
+	return errors.New("addr must be a string or an array of strings")
+}
+
+// MarshalJSON returns 'addr' as a single string if only one address is present, otherwise an array.
+func (af AddrField) MarshalJSON() ([]byte, error) {
+	if len(af.Addresses) == 1 {
+		return json.Marshal(af.Addresses[0])
+	}
+	return json.Marshal(af.Addresses)
+}
+
+// NewCip27Metadata creates a new CIP-027 metadata object with the given rate and addresses.
+func NewCip27Metadata(rate string, addresses []string) (*Cip27Metadata, error) {
+	meta := &Cip27Metadata{
+		Num777: Cip777{
+			Rate: rate,
+			Addr: AddrField{Addresses: addresses},
+		},
+	}
+	if err := meta.Validate(); err != nil {
+		return nil, err
+	}
+	return meta, nil
+}
+
+// Validate checks that Rate is within [0..1] and there's at least one address.
+func (c *Cip27Metadata) Validate() error {
+	validate := validator.New()
+	if err := validate.Struct(c); err != nil {
+		return err
+	}
+	val, err := strconv.ParseFloat(c.Num777.Rate, 64)
+	if err != nil {
+		return errors.New("rate must be a valid floating point number")
+	}
+	if val < 0 || val > 1 {
+		return errors.New("rate must be between 0.0 and 1.0")
+	}
+	if len(c.Num777.Addr.Addresses) == 0 {
+		return errors.New("at least one address is required")
+	}
+	return nil
+}