package schedule

import (
	"encoding"
	"fmt"
	"io"
	"strconv"
	"time"

	"github.com/99designs/gqlgen/graphql"
	"github.com/google/uuid"
	"github.com/target/goalert/util/timeutil"
	"github.com/target/goalert/validation"
)

// An OnCallNotificationRule defines when notifications for on-call users for a schedule
// should be sent.
type OnCallNotificationRule struct {
	// ID is a persistent value for UI or other systems to track rule additions/deletions/edits.
	ID RuleID

	// ChannelID is the notification channel ID for notifications.
	ChannelID uuid.UUID

	Time          *timeutil.Clock
	WeekdayFilter *timeutil.WeekdayFilter

	NextNotification *time.Time
}

// RuleID uniquely identifies an OnCallNotificationRule within the context of a single schedule
// and is stable across updates.
type RuleID struct {
	scheduleID uuid.UUID
	id         int
	valid      bool
}

var (
	_ encoding.TextMarshaler   = RuleID{}
	_ encoding.TextUnmarshaler = &RuleID{}
	_ graphql.Marshaler        = RuleID{}
	_ graphql.Unmarshaler      = &RuleID{}
)

func (r RuleID) MarshalGQL(w io.Writer) {
	graphql.MarshalString(r.String()).MarshalGQL(w)
}

func (r *RuleID) UnmarshalGQL(v interface{}) error {
	s, err := graphql.UnmarshalString(v)
	if err != nil {
		return err
	}
	err = r.UnmarshalText([]byte(s))
	if err != nil {
		return validation.WrapError(err)
	}

	return nil
}

func (r RuleID) String() string {
	if !r.valid {
		return ""
	}

	return fmt.Sprintf("%s:%d", r.scheduleID.String(), r.id)
}

func (r RuleID) MarshalText() ([]byte, error) {
	if !r.valid {
		return nil, nil
	}

	return []byte(r.String()), nil
}

// UnmarshalText will parse a rule in string form.
//
// Format is a 36-char UUID string, then colon, followed by a unique int value.
func (r *RuleID) UnmarshalText(data []byte) error {
	s := string(data)
	if s == "" {
		r.valid = false
		r.id = 0
		r.scheduleID = uuid.UUID{}
		return nil
	}
	if len(s) < 38 {
		return fmt.Errorf("input too short")
	}

	var err error
	r.scheduleID, err = uuid.Parse(s[:36])
	if err != nil {
		return err
	}
	i, err := strconv.ParseInt(string(data[37:]), 10, 32)
	if err != nil {
		return err
	}
	r.id = int(i)
	r.valid = true

	return nil
}