We build too many walls and not enough bridges

internal/metrics/metrics.go

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+// Copyright (c) 2020 Proton Technologies AG
+//
+// This file is part of ProtonMail Bridge.
+//
+// ProtonMail Bridge is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// ProtonMail Bridge is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with ProtonMail Bridge.  If not, see <https://www.gnu.org/licenses/>.
+
+// Package metrics collects string constants used to report anonymous usage metrics.
+package metrics
+
+type (
+	Category string
+	Action   string
+	Label    string
+)
+
+// Metric represents a single metric that can be reported and contains the necessary fields
+// of category, action and label that the /metrics endpoint expects.
+type Metric struct {
+	c Category
+	a Action
+	l Label
+}
+
+// New returns a metric struct with the given category, action and label.
+// Maybe in future we could perform checks here that the correct category is given for each action.
+// That's why the Metric fields are not exported; we don't want users creating broken metrics
+// (though for now they still can do that).
+func New(c Category, a Action, l Label) Metric {
+	return Metric{c: c, a: a, l: l}
+}
+
+// Get returns the category, action and label of a metric.
+func (m Metric) Get() (Category, Action, Label) {
+	return m.c, m.a, m.l
+}
+
+// Metrics related to bridge/account setup.
+const (
+	// Setup is used to group metrics related to bridge setup e.g. first start, new user.
+	Setup = Category("setup")
+
+	// FirstStart signifies that the bridge has been started for the first time on a user's
+	// machine (or at least, no config directory was found).
+	FirstStart = Action("first_start")
+
+	// NewUser signifies a new user account has been added to the bridge.
+	NewUser = Action("new_user")
+)
+
+// Metrics related to heartbeats of various kinds.
+const (
+	// Heartbeat is used to group heartbeat metrics e.g. the daily alive signal.
+	Heartbeat = Category("heartbeat")
+
+	// Daily is a daily signal that indicates continued bridge usage.
+	Daily = Action("daily")
+)
+
+const NoLabel = Label("")