fix: strict ClockTime parsing and ISODuration SQL

Validate constructors, strict HH:MM:SS parse, UTC ClockTimeFromTime,
ISODuration Value/Scan, Compare and TextMarshaler, codec.go split.

Co-authored-by: Cursor <cursoragent@cursor.com>

duration.go

@@ -1,20 +1,16 @@
 package clocktime
 
 import (
-	"encoding/json"
 	"fmt"
-	"io"
 	"time"
 
 	"github.com/sosodev/duration"
 )
 
-// ISODuration wraps a time.Duration to provide custom JSON and SQL
-// serialization and full ISO8061 compatibility. Note: ISODuration is limited
-// to the same range as time.Duration despite ISO8061 supporting larger durations.
+// ISODuration wraps time.Duration with ISO 8601 string formatting.
 type ISODuration time.Duration
 
-// NewISODuration creates a new duration from numeric components.
+// NewISODuration creates a duration from hour, minute, and second components.
 func NewISODuration(hours, minutes, seconds int) ISODuration {
 	return ISODuration(
 		time.Hour*time.Duration(hours) +
@@ -23,77 +19,31 @@ func NewISODuration(hours, minutes, seconds int) ISODuration {
 	)
 }
 
-// DurationFromISOString parses an ISO8601 duration string (e.g., "PT1H30M45S")
-// and returns an ISODuration.
+// ParseISODuration parses an ISO 8601 duration string (for example PT1H30M).
+func ParseISODuration(s string) (ISODuration, error) {
+	return DurationFromISOString(s)
+}
+
+// DurationFromISOString parses an ISO 8601 duration string.
 func DurationFromISOString(s string) (ISODuration, error) {
 	d, err := duration.Parse(s)
 	if err != nil {
-		return 0, fmt.Errorf("error parsing ISO8061 duration: %w", err)
+		return 0, fmt.Errorf("error parsing ISO 8601 duration: %w", err)
 	}
 	return ISODuration(d.ToTimeDuration()), nil
 }
 
-// ISODurationFromDuration converts a time.Duration to an ISODuration.
+// ISODurationFromDuration converts a time.Duration to ISODuration.
 func ISODurationFromDuration(d time.Duration) ISODuration {
 	return ISODuration(d)
 }
 
-// String returns the ISO8601 string representation of the ISODuration.
+// String returns the ISO 8601 representation.
 func (d ISODuration) String() string {
-	td := time.Duration(d)
-	isoDur := duration.FromTimeDuration(td)
-	return isoDur.String()
+	return duration.FromTimeDuration(time.Duration(d)).String()
 }
 
-// Duration returns the time.Duration representation of the ISODuration.
+// Duration returns the underlying time.Duration.
 func (d ISODuration) Duration() time.Duration {
 	return time.Duration(d)
 }
-
-// MarshalJSON implements the json.Marshaler interface for ISODuration,
-// serializing it as an ISO8601 duration string.
-func (d ISODuration) MarshalJSON() ([]byte, error) {
-	return json.Marshal("\"" + d.String() + "\"")
-}
-
-// UnmarshalJSON implements the json.Unmarshaler interface for ISODuration,
-// parsing an ISO8601 duration string.
-func (d *ISODuration) UnmarshalJSON(data []byte) error {
-	var s string
-	if err := json.Unmarshal(data, &s); err != nil {
-		return err
-	}
-	parsedDur, err := DurationFromISOString(s)
-	if err != nil {
-		return err
-	}
-	*d = parsedDur
-	return nil
-}
-
-// MarshalGQL implements the graphql.Marshaler interface for ISODuration,
-// serializing it as an ISO8601 duration string.
-func (d ISODuration) MarshalGQL(w io.Writer) {
-	fmt.Fprint(w, "\""+d.String()+"\"")
-}
-
-// UnmarshalGQL implements the graphql.Unmarshaler interface for ISODuration,
-// parsing an ISO8601 duration string. nil values are treated as zero duration.
-func (d *ISODuration) UnmarshalGQL(value any) error {
-	if value == nil {
-		*d = ISODuration(0)
-		return nil
-	}
-
-	s, ok := value.(string)
-	if !ok {
-		return fmt.Errorf("ISODuration must be a string")
-	}
-
-	parsedDur, err := DurationFromISOString(s)
-	if err != nil {
-		return err
-	}
-	*d = parsedDur
-	return nil
-}