oklahomer/go-sarah

package sarah

import (
    "context"
    "fmt"
    "strings"
)

// Alerter notifies administrators when Sarah or a bot is in a critical state.
// This is recommended to design one Alerter implementation deal with one and only one communication channel.
// e.g. MailAlerter sends an e-mail to administrators; SMSAlerter sends an SMS message to administrators.
// To notify via multiple communication channels, register as many Alerter implementations as required with multiple RegisterAlerter calls.
type Alerter interface {
    // Alert sends a notification to administrators so they can acknowledge the current critical state.
    Alert(context.Context, BotType, error) error
}

type alertErrs []error

func (e *alertErrs) appendError(err error) {
    *e = append(*e, err)
}

func (e *alertErrs) isEmpty() bool {
    return len(*e) == 0
}

// Error returns stringified form of all stored errors.
func (e *alertErrs) Error() string {
    var errs []string
    for _, err := range *e {
        errs = append(errs, err.Error())
    }
    return strings.Join(errs, "\n")
}

type alerters []Alerter

func (a *alerters) appendAlerter(alerter Alerter) {
    *a = append(*a, alerter)
}

func (a *alerters) alertAll(ctx context.Context, botType BotType, err error) error {
    errs := &alertErrs{}
    for _, alerter := range *a {
        // Considering the irregular state of Bot's lifecycle and importance of alert,
        // it is safer to be panic-proof.
        func() {
            defer func() {
                if r := recover(); r != nil {
                    e, ok := r.(error)
                    if ok {
                        errs.appendError(fmt.Errorf("panic on alerting via %T: %w", alerter, e))
                        return
                    }

                    errs.appendError(fmt.Errorf("panic on alerting via %T: %+v", alerter, r))
                }
            }()

            err := alerter.Alert(ctx, botType, err)
            if err != nil {
                errs.appendError(fmt.Errorf("failed to send alert via %T: %w", alerter, err))
            }
        }()
    }

    if errs.isEmpty() {
        return nil
    }
    return errs
}