// Package usage holds the platform's metering shapes: what a box or console
// pass writes under usage/ in the deployment bucket, and the canonical meter
// vocabulary every consumer — statements, scenarios, dashboards, a future
// billing engine — speaks. Meter names are FROZEN once merged: renaming one
// orphans every statement already written (spec: billing readiness).
//
// Everything here is decision-grade, not invoice-grade (spec: modelling
// instrument): CAS-merge retries can in rare cases double-count one 5-minute
// window, and days a writer was down are simply absent. Consumers must treat
// missing days as reduced coverage, never as zero usage.
package usage

import "time"

// Meter identifiers — the canonical billing vocabulary.
const (
	MeterCPUCoreHours        = "cpu_core_hours"
	MeterMemGBHours          = "mem_gb_hours"
	MeterEgressGB            = "egress_gb"
	MeterRequests1k          = "requests_1k"
	MeterStorageGBMonth      = "storage_gb_month"
	MeterAppMonths           = "app_months"
	MeterInstanceHours       = "instance_hours"
	MeterFleetBoxHoursServer = "fleet_box_hours_server"
	MeterFleetBoxHoursDevice = "fleet_box_hours_device"
	// MeterBackhaulGB is the hop SUBSET of MeterEgressGB (usage.EdgeRow's
	// HopBytesOut): bytes that left a home box for a region edge before
	// reaching the client. It rides in statements and the economics sweep
	// as data (#288) and is priced in NO account's cost, revenue or bill —
	// #284's ruling is absorb. A billing engine iterating meters generically
	// must skip it, as economics.PriceAccount's usage check does; its priced
	// terms name their meters. The platform's own cost for it is the
	// inter-region leg, RateCard.InterRegionGBUSD.
	MeterBackhaulGB = "backhaul_gb"
	// MeterBackhaulRequests1k is the request-count twin of MeterBackhaulGB:
	// requests that crossed a region before being served. Informational,
	// unpriced, same posture.
	MeterBackhaulRequests1k = "backhaul_requests_1k"
	// Scan meters stay in the units the scanner observes. Converting bytes to
	// decimal gigabytes at collection time would discard small scans forever,
	// and neither meter is priced today.
	MeterScanObjects = "scan_objects"
	MeterScanBytes   = "scan_bytes"
)

// DayOf is the UTC date label used in every usage key.
func DayOf(t time.Time) string { return t.UTC().Format("2006-01-02") }

// MonthOf is the UTC month label used in statement and bill keys.
func MonthOf(t time.Time) string { return t.UTC().Format("2006-01") }

// HourLabel is the two-digit UTC hour used inside day objects.
func HourLabel(t time.Time) string { return t.UTC().Format("15") }