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.
type ISODuration time.Duration

// NewISODuration creates a new duration from numeric components.
func NewISODuration(hours, minutes, seconds int) ISODuration {
	return ISODuration(
		time.Hour*time.Duration(hours) +
			time.Minute*time.Duration(minutes) +
			time.Second*time.Duration(seconds),
	)
}

// DurationFromISOString parses an ISO8601 duration string (e.g., "PT1H30M45S")
// and returns an ISODuration.
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 ISODuration(d.ToTimeDuration()), nil
}

// ISODurationFromDuration converts a time.Duration to an ISODuration.
func ISODurationFromDuration(d time.Duration) ISODuration {
	return ISODuration(d)
}

// String returns the ISO8601 string representation of the ISODuration.
func (d ISODuration) String() string {
	td := time.Duration(d)
	isoDur := duration.FromTimeDuration(td)
	return isoDur.String()
}

// Duration returns the time.Duration representation of the ISODuration.
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
}