webhooker/internal/delivery/target_config_view.go

package delivery

import (
	"fmt"
	"strconv"
	"time"

	"sneak.berlin/go/webhooker/internal/database"
)

// configUnavailable is what a target's configuration renders
// as when it is absent, of an unknown type, or does not
// parse. The stored blob is never shown as a fallback: it can
// hold a credential (a Slack incoming webhook URL is a bearer
// token) and a UI that prints it leaks that credential into
// browser history, screenshots and screen shares.
const configUnavailable = "(unavailable)"

// ConfigField is one labelled, display-safe value derived
// from a target's stored configuration.
type ConfigField struct {
	Label string
	Value string
}

// deletedNameSuffix marks the name of a target that no longer
// exists. Deletes are soft and delivery history outlives the
// target, so the event log shows names of targets that are gone;
// an operator reading one needs to know it cannot be delivered
// to, replayed to, or configured.
const deletedNameSuffix = " (deleted)"

// TargetView is the display-safe projection of a target for
// the UI. It deliberately has no raw configuration field, so
// no template — present or future — can render the stored
// blob.
type TargetView struct {
	ID   string
	Name string

	// Deleted reports that this target's row is soft deleted.
	// Only views built for historical display carry it set:
	// every other projection is of a live row.
	Deleted bool

	Type   database.TargetType
	Active bool
	Config []ConfigField
}

// DisplayName is the name to render, marked when the target has
// been deleted. Templates showing a name against historical data
// must use it rather than Name, which stays the stored name.
func (v TargetView) DisplayName() string {
	if v.Deleted {
		return v.Name + deletedNameSuffix
	}

	return v.Name
}

// NewTargetViews projects targets for rendering, replacing
// each stored configuration blob with named, display-safe
// fields.
//
// A soft-deleted row projects exactly as a live one does, minus
// the deleted marker on its name: masking is a property of the
// projection, not of the row's state, so a deleted target's
// credential is as unreachable from a template as a live
// target's.
func NewTargetViews(
	targets []database.Target,
) []TargetView {
	views := make([]TargetView, 0, len(targets))

	for i := range targets {
		t := &targets[i]

		views = append(views, TargetView{
			ID:      t.ID,
			Name:    t.Name,
			Deleted: t.DeletedAt.Valid,
			Type:    t.Type,
			Active:  t.Active,
			Config:  targetConfigFields(t),
		})
	}

	return views
}

// targetConfigFields returns the display-safe fields for a
// target's configuration. Anything it cannot parse becomes
// the neutral placeholder.
func targetConfigFields(
	t *database.Target,
) []ConfigField {
	switch t.Type {
	case database.TargetTypeSlack:
		return slackConfigFields(t)
	case database.TargetTypeHTTP:
		return httpConfigFields(t)
	case database.TargetTypeDatabase:
		return databaseConfigFields(t.Config)
	case database.TargetTypeLog:
		// The log target takes no configuration.
		return nil
	default:
		return unavailableConfigFields()
	}
}

// unavailableConfigFields is the neutral placeholder shown
// for a configuration that could not be presented.
func unavailableConfigFields() []ConfigField {
	return []ConfigField{{
		Label: "Configuration",
		Value: configUnavailable,
	}}
}

// slackConfigFields describes a Slack target: its masked
// webhook URL and its retry count. Only the masked URL is
// shown; the full URL is the credential.
func slackConfigFields(t *database.Target) []ConfigField {
	cfg, err := parseSlackConfig(t.Config)
	if err != nil {
		return unavailableConfigFields()
	}

	return []ConfigField{{
		Label: "Webhook URL",
		Value: cfg.MaskedWebhookURL(),
	}, maxRetriesField(t)}
}

// httpConfigFields describes an HTTP target: its destination
// and its retry settings. Header values are not shown — they
// routinely carry authorization tokens — only how many are
// configured.
//
// The destination is masked to scheme and host by the same
// rule the Slack target uses. An HTTP target's destination is
// commonly a Slack, Discord or Teams incoming-webhook endpoint
// whose path segments are the credential, and the field takes
// an arbitrary URL, so no segment can be assumed non-secret.
func httpConfigFields(t *database.Target) []ConfigField {
	cfg, err := parseHTTPConfig(t.Config)
	if err != nil {
		return unavailableConfigFields()
	}

	fields := []ConfigField{{
		Label: "Destination URL",
		Value: MaskURL(cfg.URL),
	}}

	if cfg.Timeout > 0 {
		fields = append(fields, ConfigField{
			Label: "Timeout",
			Value: strconv.Itoa(cfg.Timeout) + "s",
		})
	}

	if len(cfg.Headers) > 0 {
		fields = append(fields, ConfigField{
			Label: "Headers",
			Value: fmt.Sprintf(
				"%d configured", len(cfg.Headers),
			),
		})
	}

	fields = append(fields, maxRetriesField(t))

	return fields
}

// maxRetriesField describes a target's retry count, which lives
// on the target row rather than in its configuration blob. A
// stored 0 makes a single attempt, so it is shown as 1.
func maxRetriesField(t *database.Target) ConfigField {
	attempts := strconv.Itoa(t.MaxRetries)
	if t.MaxRetries == 0 {
		attempts = "1 (fire-and-forget: no retries, no circuit breaker)"
	}

	return ConfigField{
		Label: "Delivery attempts",
		Value: attempts,
	}
}

// databaseConfigFields describes an archive target by its
// expiry in plain units, such as "30 days", or "never" when
// the archive is kept forever, and by its rotation. An expiry
// that is set but not a valid duration, or a rotation that is
// not one of the four, is reported as unavailable rather than
// echoed back.
func databaseConfigFields(configJSON string) []ConfigField {
	expiry, err := parseArchiveExpiry(configJSON)
	if err != nil {
		return unavailableConfigFields()
	}

	rotation, err := parseArchiveRotation(configJSON)
	if err != nil {
		return unavailableConfigFields()
	}

	value := archiveExpiryNever
	if expiry > 0 {
		value = plainDuration(expiry)
	}

	return []ConfigField{{
		Label: "Archive expiry",
		Value: value,
	}, {
		Label: "Archive rotation",
		Value: rotation,
	}}
}

// plainDuration writes a positive duration as a count of the
// largest whole unit it divides into: "30 days", "12 hours",
// "1 minute". A duration with a fraction of a second is
// written as Go writes it.
func plainDuration(d time.Duration) string {
	const day = 24 * time.Hour

	units := []struct {
		size time.Duration
		name string
	}{
		{day, "day"},
		{time.Hour, "hour"},
		{time.Minute, "minute"},
		{time.Second, "second"},
	}

	for _, unit := range units {
		if d%unit.size != 0 {
			continue
		}

		count := int64(d / unit.size)
		if count == 1 {
			return "1 " + unit.name
		}

		return fmt.Sprintf("%d %ss", count, unit.name)
	}

	return d.String()
}

// MaskedWebhookURL returns the Slack webhook URL reduced to
// its scheme and host, with the path, query and any userinfo
// elided. The path segments are the credential, so none of
// them is shown: the field accepts an arbitrary URL, so no
// segment can be assumed non-secret. A URL that does not
// parse into a scheme and host yields the neutral
// placeholder, never the raw string.
func (c *SlackTargetConfig) MaskedWebhookURL() string {
	return MaskURL(c.WebhookURL)
}