feat: add Snowflake

snowflake.go

@@ -0,0 +1,93 @@
+package snowflake
+
+import (
+	"bytes"
+	"encoding/json"
+	"strconv"
+	"time"
+)
+
+// Snowflake represents a Discord snowflake.
+// See https://discord.com/developers/docs/reference
+// for more information.
+type Snowflake int64
+
+// Nil represents an empty Snowflake.
+var Nil = (*Snowflake)(nil)
+
+// Zero represents the zero value for a Snowflake.
+var Zero = Snowflake(0)
+
+// discordEpoch is the time of the first second of 2015, in milliseconds.
+const discordEpoch = 1420070400000
+
+// Parse constructs a Snowflake from s.
+func Parse(s string) (Snowflake, error) {
+	if s == "" {
+		return Zero, nil
+	}
+	parsed, err := strconv.ParseInt(s, 10, 0)
+	return Snowflake(parsed), err
+}
+
+// FromTimestamp generates a Snowflake for the given time.
+func FromTimestamp(time time.Time) Snowflake {
+	return Snowflake(time.UnixMilli()-discordEpoch) << 22
+}
+
+// Timestamp returns the number of milliseconds since discordEpoch.
+func (s Snowflake) Timestamp() int64 {
+	return (int64(s) >> 22) + discordEpoch
+}
+
+// WorkerID returns the Snowflake's worker id.
+func (s Snowflake) WorkerID() int64 {
+	return (int64(s) & 0x3E0000) >> 17
+}
+
+// ProcessID returns the Snowflake's process id.
+func (s Snowflake) ProcessID() int64 {
+	return (int64(s) & 0x1F000) >> 12
+}
+
+// Increment returns the number of id's that have
+// been generated on the Snowflake's process.
+func (s Snowflake) Increment() int64 {
+	return int64(s) & 0xFFF
+}
+
+// UnmarshalJSON unmarshals data into s.
+func (s *Snowflake) UnmarshalJSON(data []byte) error {
+	dec := json.NewDecoder(bytes.NewReader(data))
+	dec.UseNumber()
+
+	var raw json.Number
+	if err := dec.Decode(&raw); err != nil {
+		typeErr, ok := err.(*json.UnmarshalTypeError)
+		if ok {
+			return UnmarshalTypeError{
+				value:      typeErr.Value,
+				structName: typeErr.Struct,
+				field:      typeErr.Field,
+				typ:        "int or string",
+			}
+		}
+		return err
+	}
+
+	parsed, err := raw.Int64()
+	if err == nil {
+		*s = Snowflake(parsed)
+	}
+	return err
+}
+
+// MarshalJSON returns the JSON representation of s.
+func (s Snowflake) MarshalJSON() ([]byte, error) {
+	return []byte(s.String()), nil
+}
+
+// String returns the string representation of s.
+func (s Snowflake) String() string {
+	return strconv.FormatInt(int64(s), 10)
+}

unmarshal_type_err.go

@@ -0,0 +1,20 @@
+package snowflake
+
+import "fmt"
+
+// UnmarshalTypeError is like json.UnmarshalTypeError, but
+// uses a string to represent the Go value it could not be
+// assigned to, instead of a reflect.Type.
+type UnmarshalTypeError struct {
+	value      string
+	structName string
+	field      string
+	typ        string
+}
+
+func (err UnmarshalTypeError) Error() string {
+	if err.structName != "" || err.field != "" {
+		return fmt.Sprintf("json: cannot unmarshal %s into Go struct field %s\".\"%s of type %s", err.value, err.structName, err.field, err.typ)
+	}
+	return fmt.Sprintf("json: cannot unmarshal %s into Go value of type %s", err.value, err.typ)
+}