Convert gas meter volume readings to kWh for cost calculations
Gas meters are read in raw volume (ft3 on our imperial meter, m3 on newer metric ones), never kWh — but tariff rates and CCL/RAB levy are all p/kWh. Add gas_volume_unit + gas_calorific_value to meters, and convert reading deltas to kWh in cost-calc.js using the standard UK gas-billing formula (matches the exact calculation printed on supplier invoices) before any cost math runs. Also fixes meter/readings pages showing raw gas dial readings mislabeled as "kWh" — they now show the actual physical unit (ft³/m³) via a new reading_unit_label, while computed consumption stays correctly labeled kWh. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
This commit is contained in:
parent
23d8009e00
commit
67dd943cdb
8 changed files with 140 additions and 16 deletions
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@ -47,6 +47,13 @@ export async function initDb() {
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ALTER TABLE meters ADD COLUMN IF NOT EXISTS mqtt_topic TEXT;
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CREATE UNIQUE INDEX IF NOT EXISTS meters_mqtt_topic_uidx ON meters (mqtt_topic) WHERE mqtt_topic IS NOT NULL;
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-- gas meters read raw volume off the dial (m3 on newer metric meters, ft3 on
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-- older imperial ones like ours), never kWh directly — these two columns let
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-- cost-calc.js convert a volume reading to billed kWh using the same
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-- industry formula suppliers print on their invoices. NULL on non-gas meters.
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ALTER TABLE meters ADD COLUMN IF NOT EXISTS gas_volume_unit TEXT;
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ALTER TABLE meters ADD COLUMN IF NOT EXISTS gas_calorific_value NUMERIC(6,3);
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-- fallback_split_pct e.g. {"day":60,"night":40} — used to split one cumulative
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-- reading across TOU rate windows when there's no device data (v1: manual only)
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CREATE TABLE IF NOT EXISTS tariffs (
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@ -47,6 +47,40 @@ async function latestReading(meterId) {
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return rows[0] || null
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}
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// Gas meters are read in raw volume (m3 on newer metric meters, ft3 on older
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// imperial ones) — never kWh directly. These constants mirror the standard
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// UK gas-billing formula suppliers print on their invoices: metric meters
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// skip the imperial multiplier, imperial ones apply it first.
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const GAS_VOLUME_CORRECTION_FACTOR = 1.02264 // fixed industry constant, corrects for temperature/pressure
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const GAS_IMPERIAL_TO_METRIC_FACTOR = 2.83 // ft3 meters only
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const GAS_DEFAULT_CALORIFIC_VALUE = 39.5 // typical UK natural gas CV (MJ/m3), used until a meter's own value is set from a bill
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function gasVolumeToKwh(volume, unit, calorificValue) {
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const cv = Number(calorificValue) || GAS_DEFAULT_CALORIFIC_VALUE
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const base = unit === 'ft3' ? volume * GAS_IMPERIAL_TO_METRIC_FACTOR : volume
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return (base * cv * GAS_VOLUME_CORRECTION_FACTOR) / 3.6
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}
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async function getMeterGasConfig(meterId) {
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const { rows } = await pool.query(
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`SELECT c.key AS category_key, m.gas_volume_unit, m.gas_calorific_value
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FROM meters m JOIN meter_categories c ON c.id = m.category_id WHERE m.id = $1`,
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[meterId]
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)
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return rows[0] || null
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}
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// Converts a raw reading-delta to the category's billed unit — a no-op for
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// every category except gas meters with a volume unit configured, where the
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// raw m3/ft3 delta becomes kWh so it lines up with tariff rates (p/kWh).
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async function convertMeterConsumption(meterId, rawConsumption) {
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const gasConfig = await getMeterGasConfig(meterId)
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if (gasConfig?.category_key === 'gas' && gasConfig.gas_volume_unit) {
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return gasVolumeToKwh(rawConsumption, gasConfig.gas_volume_unit, gasConfig.gas_calorific_value)
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}
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return rawConsumption
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}
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// Consumption for a meter over [periodStart, periodEnd] (inclusive), bracketing
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// the boundaries with the nearest available readings — meters get one manual
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// cumulative reading, not necessarily one exactly on the period edge.
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@ -57,7 +91,8 @@ export async function getPeriodConsumption(meterId, periodStart, periodEnd) {
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if (!first || !last || last.reading_date <= first.reading_date) {
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return { consumption: null, first, last, has_data: false }
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}
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const consumption = Number(last.reading_value) - Number(first.reading_value)
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const rawConsumption = Number(last.reading_value) - Number(first.reading_value)
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const consumption = await convertMeterConsumption(meterId, rawConsumption)
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return { consumption, first, last, has_data: true }
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}
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@ -80,7 +115,8 @@ export async function getTrailingDailyRate(meterId, windowDays) {
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const days = daysBetween(before.reading_date, latest.reading_date)
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if (days <= 0) return { daily_rate: null, latest }
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const consumption = Number(latest.reading_value) - Number(before.reading_value)
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const rawConsumption = Number(latest.reading_value) - Number(before.reading_value)
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const consumption = await convertMeterConsumption(meterId, rawConsumption)
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return { daily_rate: consumption / days, latest, window_start_reading: before }
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}
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@ -4,9 +4,20 @@ import { createWriteStream } from 'fs'
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import { mkdir, unlink } from 'fs/promises'
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import { randomUUID } from 'crypto'
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import { extname, join } from 'path'
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import { refreshTopicMap } from '../lib/mqtt.js'
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import { getMeterHistorySeries } from '../lib/history.js'
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const ALLOWED_IMAGES = ['image/jpeg', 'image/jpg', 'image/png', 'image/webp']
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// A gas meter's raw dial reads volume (ft3/m3), never the category's billed
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// unit (kWh) — everywhere a raw reading_value is displayed it needs this
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// label instead of c.unit_label, which is correct only for computed consumption.
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const READING_UNIT_LABEL_SQL = `
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CASE WHEN c.key = 'gas' AND m.gas_volume_unit IS NOT NULL
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THEN (CASE WHEN m.gas_volume_unit = 'ft3' THEN 'ft³' ELSE 'm³' END)
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ELSE c.unit_label END AS reading_unit_label
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`
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export async function meterRoutes(app, opts) {
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const UPLOADS_DIR = opts.uploadsDir
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app.addHook('preHandler', requireAuth)
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@ -21,7 +32,7 @@ export async function meterRoutes(app, opts) {
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const where = conditions.length ? `WHERE ${conditions.join(' AND ')}` : ''
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const { rows } = await pool.query(
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`SELECT m.*, c.name AS category_name, c.key AS category_key, c.unit_label,
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`SELECT m.*, c.name AS category_name, c.key AS category_key, c.unit_label, ${READING_UNIT_LABEL_SQL},
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p.name AS parent_name,
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lr.reading_value AS latest_reading_value, lr.reading_date AS latest_reading_date
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FROM meters m
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@ -41,7 +52,7 @@ export async function meterRoutes(app, opts) {
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// GET /api/meters/:id — detail: meter + children + tariff history + recent readings
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app.get('/api/meters/:id', async (req, reply) => {
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const { rows } = await pool.query(
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`SELECT m.*, c.name AS category_name, c.key AS category_key, c.unit_label, p.name AS parent_name
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`SELECT m.*, c.name AS category_name, c.key AS category_key, c.unit_label, ${READING_UNIT_LABEL_SQL}, p.name AS parent_name
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FROM meters m
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JOIN meter_categories c ON c.id = m.category_id
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LEFT JOIN meters p ON p.id = m.parent_meter_id
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@ -81,10 +92,16 @@ export async function meterRoutes(app, opts) {
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const b = req.body || {}
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if (!b.name || !b.category_id) return reply.status(400).send({ error: 'name and category_id required' })
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const { rows } = await pool.query(
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`INSERT INTO meters (category_id, parent_meter_id, name, location, serial_number, install_date, notes)
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VALUES ($1,$2,$3,$4,$5,$6,$7) RETURNING *`,
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[b.category_id, b.parent_meter_id || null, b.name, b.location || null, b.serial_number || null, b.install_date || null, b.notes || null]
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`INSERT INTO meters (category_id, parent_meter_id, name, location, serial_number, install_date, notes, mqtt_topic,
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gas_volume_unit, gas_calorific_value)
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VALUES ($1,$2,$3,$4,$5,$6,$7,$8,$9,$10) RETURNING *`,
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[
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b.category_id, b.parent_meter_id || null, b.name, b.location || null, b.serial_number || null,
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b.install_date || null, b.notes || null, b.mqtt_topic || null,
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b.gas_volume_unit || null, b.gas_calorific_value || null,
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]
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)
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if (b.mqtt_topic) await refreshTopicMap()
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return rows[0]
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})
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@ -98,8 +115,9 @@ export async function meterRoutes(app, opts) {
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}
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const { rows } = await pool.query(
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`UPDATE meters SET category_id = $1, parent_meter_id = $2, name = $3, location = $4,
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serial_number = $5, install_date = $6, notes = $7, active = $8
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WHERE id = $9 RETURNING *`,
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serial_number = $5, install_date = $6, notes = $7, active = $8, mqtt_topic = $9,
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gas_volume_unit = $10, gas_calorific_value = $11
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WHERE id = $12 RETURNING *`,
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[
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b.category_id ?? m.category_id,
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b.parent_meter_id !== undefined ? b.parent_meter_id : m.parent_meter_id,
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@ -109,12 +127,26 @@ export async function meterRoutes(app, opts) {
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b.install_date !== undefined ? b.install_date : m.install_date,
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b.notes !== undefined ? b.notes : m.notes,
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b.active ?? m.active,
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b.mqtt_topic !== undefined ? b.mqtt_topic : m.mqtt_topic,
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b.gas_volume_unit !== undefined ? b.gas_volume_unit : m.gas_volume_unit,
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b.gas_calorific_value !== undefined ? b.gas_calorific_value : m.gas_calorific_value,
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req.params.id,
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]
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)
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if (b.mqtt_topic !== undefined) await refreshTopicMap()
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return rows[0]
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})
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// GET /api/meters/:id/history?from=&to= — stitched telemetry + readings series
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app.get('/api/meters/:id/history', async (req, reply) => {
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const { from, to } = req.query
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if (!from || !to) return reply.status(400).send({ error: 'from and to are required (YYYY-MM-DD)' })
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const { rows } = await pool.query('SELECT id FROM meters WHERE id = $1', [req.params.id])
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if (!rows.length) return reply.status(404).send({ error: 'Meter not found' })
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const series = await getMeterHistorySeries(req.params.id, from, to)
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return { meter_id: Number(req.params.id), from, to, series }
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})
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// POST /api/meters/:id/image — multipart upload, cashup-style pattern
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app.post('/api/meters/:id/image', { preHandler: requireCap('meters') }, async (req, reply) => {
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const meterId = parseInt(req.params.id)
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const ALLOWED_IMAGES = ['image/jpeg', 'image/jpg', 'image/png', 'image/webp']
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// Mirrors routes/meters.js — a gas meter's raw reading is volume (ft3/m3),
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// never the category's billed kWh unit.
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const READING_UNIT_LABEL_SQL = `
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CASE WHEN c.key = 'gas' AND m.gas_volume_unit IS NOT NULL
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THEN (CASE WHEN m.gas_volume_unit = 'ft3' THEN 'ft³' ELSE 'm³' END)
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ELSE c.unit_label END AS unit_label
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`
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export async function readingRoutes(app, opts) {
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const UPLOADS_DIR = opts.uploadsDir
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app.addHook('preHandler', requireAuth)
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@ -23,7 +31,7 @@ export async function readingRoutes(app, opts) {
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params.push(Math.min(parseInt(limit) || 100, 500))
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const { rows } = await pool.query(
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`SELECT r.*, m.name AS meter_name, c.unit_label
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`SELECT r.*, m.name AS meter_name, ${READING_UNIT_LABEL_SQL}
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FROM readings r
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JOIN meters m ON m.id = r.meter_id
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JOIN meter_categories c ON c.id = m.category_id
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@ -96,7 +96,7 @@ export default function MeterDetail() {
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<div className="stats-strip">
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<div className="stat-box"><div className="stat-value">{meter.category_name}</div><div className="stat-label">Category</div></div>
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<div className="stat-box">
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<div className="stat-value">{formatUnits(meter.latest_reading_value ? Number(meter.latest_reading_value) : null, meter.unit_label)}</div>
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<div className="stat-value">{formatUnits(meter.latest_reading_value ? Number(meter.latest_reading_value) : null, meter.reading_unit_label)}</div>
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<div className="stat-label">Latest reading</div>
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</div>
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<div className="stat-box"><div className="stat-value">{currentTariff?.tariff_name || '—'}</div><div className="stat-label">Current tariff</div></div>
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@ -184,7 +184,7 @@ export default function MeterDetail() {
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{meter.recent_readings.map(r => (
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<tr key={r.id}>
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<td>{new Date(r.reading_date).toLocaleDateString('en-GB')}</td>
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<td className="num">{Number(r.reading_value).toLocaleString()} {meter.unit_label}</td>
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<td className="num">{Number(r.reading_value).toLocaleString()} {meter.reading_unit_label}</td>
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<td>{r.recorded_by || '—'}</td>
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<td>{r.notes || '—'}</td>
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</tr>
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@ -9,6 +9,7 @@ import * as api from '../api'
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const emptyForm = {
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id: 0, category_id: 0, parent_meter_id: '' as number | '', name: '', location: '',
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serial_number: '', install_date: '', notes: '', active: true,
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gas_volume_unit: '' as 'm3' | 'ft3' | '', gas_calorific_value: '' as number | '',
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}
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export default function Meters() {
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@ -52,6 +53,7 @@ export default function Meters() {
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name: m.name, location: m.location || '', serial_number: m.serial_number || '',
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install_date: m.install_date ? m.install_date.slice(0, 10) : '', notes: m.notes || '',
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active: m.active,
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gas_volume_unit: m.gas_volume_unit || '', gas_calorific_value: m.gas_calorific_value != null ? Number(m.gas_calorific_value) : '',
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})
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setImageFile(null)
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}
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@ -62,6 +64,7 @@ export default function Meters() {
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setSaving(true)
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setError(null)
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try {
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const isGas = categories.find(c => c.id === form.category_id)?.key === 'gas'
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const body = {
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category_id: form.category_id,
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parent_meter_id: form.parent_meter_id || null,
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@ -71,6 +74,8 @@ export default function Meters() {
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install_date: form.install_date || null,
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notes: form.notes || null,
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active: form.active,
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gas_volume_unit: isGas && form.gas_volume_unit ? form.gas_volume_unit : null,
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gas_calorific_value: isGas && form.gas_calorific_value !== '' ? form.gas_calorific_value : null,
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}
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const saved = form.id ? await api.updateMeter(form.id, body) : await api.createMeter(body)
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if (imageFile) await api.uploadMeterImage(saved.id, imageFile)
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@ -140,7 +145,7 @@ export default function Meters() {
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</div>
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</div>
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<div className="meter-card-side">
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<span className="meter-reading-val">{formatUnits(m.latest_reading_value ? Number(m.latest_reading_value) : null, m.unit_label)}</span>
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<span className="meter-reading-val">{formatUnits(m.latest_reading_value ? Number(m.latest_reading_value) : null, m.reading_unit_label)}</span>
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<span className="meter-reading-date">{m.latest_reading_date ? new Date(m.latest_reading_date).toLocaleDateString('en-GB') : 'no readings'}</span>
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</div>
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{canManage && (
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@ -165,7 +170,15 @@ export default function Meters() {
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</div>
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<div className="field">
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<label>Category</label>
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<select value={form.category_id} onChange={e => setForm({ ...form, category_id: parseInt(e.target.value), parent_meter_id: '' })}>
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<select value={form.category_id} onChange={e => {
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const category_id = parseInt(e.target.value)
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const isGas = categories.find(c => c.id === category_id)?.key === 'gas'
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setForm({
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...form, category_id, parent_meter_id: '',
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gas_volume_unit: isGas ? form.gas_volume_unit : '',
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gas_calorific_value: isGas ? form.gas_calorific_value : '',
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})
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}}>
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{categories.map(c => <option key={c.id} value={c.id}>{c.name}</option>)}
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</select>
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</div>
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@ -182,6 +195,31 @@ export default function Meters() {
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</div>
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</div>
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{categories.find(c => c.id === form.category_id)?.key === 'gas' && (
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<div className="field-row">
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<div className="field">
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<label>Meter reads in</label>
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<select value={form.gas_volume_unit} onChange={e => setForm({ ...form, gas_volume_unit: e.target.value as 'm3' | 'ft3' | '' })}>
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<option value="">Select…</option>
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<option value="m3">m³ (metric)</option>
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<option value="ft3">ft³ (imperial)</option>
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</select>
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</div>
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<div className="field">
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<label>Calorific value (MJ/m³)</label>
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<input type="number" step="0.001" placeholder="e.g. 39.5 (from latest bill)" value={form.gas_calorific_value}
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onChange={e => setForm({ ...form, gas_calorific_value: e.target.value === '' ? '' : parseFloat(e.target.value) })} />
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</div>
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</div>
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)}
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{categories.find(c => c.id === form.category_id)?.key === 'gas' && (
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<div className="muted" style={{ marginTop: -8, marginBottom: 14, fontSize: '0.85em' }}>
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Readings for this meter are entered as raw volume off the dial — cost calculations convert to
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kWh using the standard gas-billing formula. Update the calorific value from time to time from
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a recent bill; it drifts slightly and defaults to a typical UK average (39.5) if left blank.
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</div>
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)}
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<div className="field-row">
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<div className="field">
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<label>Parent meter (sub-metering)</label>
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@ -90,7 +90,7 @@ export default function Readings() {
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</select>
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</div>
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<div className="field" style={{ marginBottom: 0 }}>
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<label>Reading value{selectedMeter ? ` (${selectedMeter.unit_label})` : ''}</label>
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<label>Reading value{selectedMeter ? ` (${selectedMeter.reading_unit_label})` : ''}</label>
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<input type="number" step="0.001" value={value} onChange={e => setValue(e.target.value)} placeholder="e.g. 45231.5" />
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</div>
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<div className="field" style={{ marginBottom: 0 }}>
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@ -107,7 +107,7 @@ export default function Readings() {
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</div>
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{selectedMeter?.latest_reading_value && (
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<div className="field-hint" style={{ marginTop: 6 }}>
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Previous reading: {Number(selectedMeter.latest_reading_value).toLocaleString()} {selectedMeter.unit_label} on {new Date(selectedMeter.latest_reading_date!).toLocaleDateString('en-GB')}
|
||||
Previous reading: {Number(selectedMeter.latest_reading_value).toLocaleString()} {selectedMeter.reading_unit_label} on {new Date(selectedMeter.latest_reading_date!).toLocaleDateString('en-GB')}
|
||||
</div>
|
||||
)}
|
||||
</div>
|
||||
|
|
|
|||
|
|
@ -37,6 +37,9 @@ export interface Meter {
|
|||
category_name: string
|
||||
category_key: string
|
||||
unit_label: string
|
||||
reading_unit_label: string
|
||||
gas_volume_unit: 'm3' | 'ft3' | null
|
||||
gas_calorific_value: number | null
|
||||
parent_meter_id: number | null
|
||||
parent_name: string | null
|
||||
name: string
|
||||
|
|
|
|||
Loading…
Add table
Add a link
Reference in a new issue