feat: aggregate five Tasmota plugs with cost and daily historyHEADmaster

Proxy Tasmota energy JSON into Homepage's customapi widget, which can
render JSON but cannot do arithmetic. Applies the tariff, sums across
plugs, and records the per-day history the plugs do not keep.

Plugs are fetched in parallel; sequential polling would stack five
timeouts into a 25s hang. An offline plug is reported rather than
counted as zero, so a dead sensor cannot read as "consumed nothing".

Tasmota exposes only Today/Yesterday/Total, so each poll writes
yesterday's finished kWh into SQLite keyed (day, plug), making repeat
polls and restarts idempotent.

Display strings are preformatted server-side: Homepage's locale
formatting renders 1593 W as an ambiguous "1,593", and its widget has
no columns, so pairing kWh with its cost in one value is what keeps
the cards compact.

10 files changed, 1118 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
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--- /dev/null
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+__pycache__/
+*.pyc
+*.db
diff --git a/AGENTS.md b/AGENTS.md
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+++ b/AGENTS.md
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+# tasmota-dash
+
+Energy proxy between five Tasmota smart plugs on the LAN and a Homepage
+dashboard. Homepage's `customapi` widget cannot do arithmetic, cannot format
+numbers unambiguously, and has no table layout, so everything derived is
+computed and preformatted here and the widget only maps field names to labels.
+
+## Files
+
+| File | Role |
+|---|---|
+| `tasmota_proxy.py` | The whole service. Stdlib only, no dependencies. |
+| `test_proxy.py` | Self-check: `python3 test_proxy.py`, prints `ok`. Fakes the plugs, no LAN needed. |
+| `tasmota-proxy.service` | systemd unit. Deployed to `/etc/systemd/system/`. |
+| `homepage-services.yaml` | Snippet for Homepage's `services.yaml`. |
+| `homepage-settings.yaml` | `layout:` block for Homepage's `settings.yaml`, controls the rows. |
+
+Underscore in `tasmota_proxy.py` is deliberate: a dash is not importable, and
+the test imports the module. The unit file's `ExecStart` must match.
+
+## Endpoints
+
+- `/<name>` one plug: `ac`, `washer`, `dishwasher`, `pc`, `spare`
+- `/total` sum across plugs, plus rolling 7/30-day figures
+- `/history` per-day kWh, 30 days, JSON
+- `/graph` self-contained HTML bar chart, linked from the totals widget
+- `/` plug list and available paths
+
+Unknown plug name returns 404, an upstream failure 502.
+
+## Deployment
+
+Runs on the Homepage host, listening on `127.0.0.1:8099`.
+
+```bash
+scp tasmota_proxy.py <homepage-host>:/opt/tasmota-proxy/
+scp tasmota-proxy.service <homepage-host>:/etc/systemd/system/
+ssh <homepage-host> 'systemctl daemon-reload && systemctl restart tasmota-proxy'
+```
+
+`tasmota_proxy.py` and `homepage-services.yaml` are a matched pair. Deploying
+one without the other renders blank widget rows, because the YAML maps fields
+(`power_fmt`, `today_fmt`, ...) that only the newer proxy emits.
+
+Homepage may run in a container. If it does, `127.0.0.1:8099` is the
+container's loopback, not the host's, and the widget URLs need the host IP
+with the proxy bound accordingly.
+
+## Configuration
+
+All through environment variables in the unit file:
+
+- `TASMOTA_PLUGS` — `name=host,name=host,...`, defines both the plugs and their URL paths
+- `PORT` — default 8099
+- `RATE_MARGINAL` / `RATE_ALLIN` — €/kWh from the invoice. Marginal is the consumption quota alone; all-in is total bill divided by total kWh. Widgets show all-in.
+- `HISTORY_DB` — default `/var/lib/tasmota-proxy/history.db`
+
+`StateDirectory=tasmota-proxy` in the unit is load-bearing. `ProtectSystem=strict`
+makes the filesystem read-only, so without it the first history write crashes
+the service.
+
+## Daily history
+
+Tasmota exposes only `Today`, `Yesterday` and `Total`; there is no per-day
+series to fetch and no peak/maximum field of any kind. So each `/total` poll
+writes yesterday's finished kWh per plug into SQLite, keyed `(day, plug)` so
+repeat polls and restarts overwrite instead of accumulating. Homepage polls
+every 10s, so a day is captured as long as the proxy runs at some point during
+it.
+
+Consequences worth knowing:
+
+- Today is deliberately excluded from rolling sums; it is unfinished.
+- An offline plug is skipped, so its day-row is short. A later poll *the same
+  day* fills it in; after midnight that day is lost, because Tasmota cannot be
+  asked about a day before yesterday.
+- Extended downtime leaves permanent gaps.
+
+## Working on the plugs
+
+Read state before writing it. Tasmota's HTTP API is `http://<host>/cm?cmnd=<Command>`,
+with `%20` before an argument to set it, no argument to query.
+
+**Firmware varies, probe before assuming.** On these plugs:
+
+- `EnergyReset1/2/3` do **not** exist, they return `{"Command":"Unknown"}`.
+  The working commands are `EnergyTotal`, `EnergyToday`, `EnergyYesterday`.
+- `VoltSet` / `PowerSet` do not exist either. Calibration goes through
+  `VoltageCal`, `CurrentCal`, `PowerCal`.
+- `cmnd=Cmd=0` is not the argument syntax; it arrives as `CMD =0` and fails.
+  Use `cmnd=Cmd%200`.
+
+Counter resets are irreversible. Confirm scope with the user first, and name
+which plugs are excluded.
+
+### Calibration
+
+All five are NOUS A1T, same template, and should share calibration values:
+`VoltageCal 1550`, `CurrentCal 3500`, `PowerCal 12530`.
+
+Stock `VoltageCal` is 220 and is wrong for this hardware: voltage reads ~34 V
+instead of ~239. Because power factor and apparent power are derived from
+voltage, one wrong value cascades into physically impossible readings, PF
+above 1.0, apparent power below real power, ReactivePower pinned at 3276.
+
+Diagnosing a suspect plug: compare against a known-good one on the same mains,
+and sanity-check the physics. Mains is ~230-240 V, PF cannot exceed 1.0,
+apparent power cannot be below real power. A plug failing those is
+miscalibrated, and its kWh totals are wrong too, not just its instantaneous
+reading.
+
+Voltage needs no meter, since nominal mains is known. Current and power need a
+known resistive load with a nameplate rating. PF a few percent above 1.0 is
+residual per-unit variation and is not worth chasing for cost tracking.
+
+## Conventions
+
+- Stdlib only. No dependencies, and no reason to add one.
+- Preformatted display strings (`power_fmt`, `today_fmt`, ...) exist because
+  Homepage's locale formatting renders 1593 W as an ambiguous "1,593". Numeric
+  fields stay in the JSON alongside them for any other consumer.
+- `1585 W` formats as `1.58 kW`, not 1.59. Python rounds the exact half to
+  even. Verified in the test, not a bug.
+- Widget labels are Italian, matching the rest of the dashboard.
+- Non-trivial logic keeps its assertion in `test_proxy.py`. Run it before
+  committing.
diff --git a/CLAUDE.md b/CLAUDE.md
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--- /dev/null
+++ b/CLAUDE.md
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+# tasmota-dash
+
+See @AGENTS.md for everything: architecture, endpoints, deployment, plug
+calibration and the Tasmota command gotchas.
+
+This file is intentionally thin. AGENTS.md is the single source of truth,
+shared across every agent tool. Do not duplicate content here, edit AGENTS.md
+instead.
diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..9efa6fb
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,338 @@
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diff --git a/README.md b/README.md
new file mode 100644
index 0000000..85491d6
--- /dev/null
+++ b/README.md
@@ -0,0 +1,85 @@
+# tasmota-dash
+
+Aggregates five [Tasmota](https://tasmota.github.io/docs/) smart plugs into a
+[Homepage](https://gethomepage.dev) dashboard: live power, per-day and
+lifetime energy, and what it costs in euro.
+
+Homepage's `customapi` widget can render JSON but cannot do arithmetic, so
+this proxy sits between the plugs and the dashboard, applies the tariff, sums
+across plugs and records a daily history that the plugs themselves do not keep.
+
+Stdlib Python, no dependencies, one file.
+
+## Features
+
+- Per-plug and aggregate readings on one endpoint each
+- Cost in euro at two tariffs: marginal (consumption quota) and all-in (total bill / total kWh)
+- Daily kWh history in SQLite, with rolling 7 and 30 day figures
+- A bar-chart page for the last 30 days
+- An offline plug is reported, not silently counted as zero
+
+## Endpoints
+
+| Path | Returns |
+|---|---|
+| `/<name>` | One plug: power, today/yesterday/lifetime kWh, cost |
+| `/total` | Sum across plugs, plus rolling 7/30 day figures |
+| `/history` | Per-day kWh, last 30 days, JSON |
+| `/graph` | HTML bar chart of the last 30 days |
+| `/` | Plug list and available paths |
+
+## Install
+
+Runs on the machine hosting Homepage, listening on `127.0.0.1:8099`.
+
+```bash
+install -Dm755 tasmota_proxy.py /opt/tasmota-proxy/tasmota_proxy.py
+install -Dm644 tasmota-proxy.service /etc/systemd/system/tasmota-proxy.service
+# edit the unit: plug addresses and tariff rates
+systemctl daemon-reload && systemctl enable --now tasmota-proxy
+curl -s localhost:8099/total
+```
+
+Then merge `homepage-services.yaml` into Homepage's `services.yaml` and the
+`layout:` block from `homepage-settings.yaml` into its `settings.yaml`, and
+restart Homepage.
+
+## Configuration
+
+Environment variables, set in the unit file:
+
+| Variable | Default | Meaning |
+|---|---|---|
+| `TASMOTA_PLUGS` | five LAN addresses | `name=host,name=host,...` — also defines the URL paths |
+| `PORT` | `8099` | Listen port, bound to localhost |
+| `RATE_MARGINAL` | `0.17598` | €/kWh, consumption quota only |
+| `RATE_ALLIN` | `0.2754` | €/kWh, total bill divided by total kWh |
+| `HISTORY_DB` | `/var/lib/tasmota-proxy/history.db` | Daily history |
+
+## History
+
+Tasmota keeps only today, yesterday and a lifetime total. Each poll records
+yesterday's finished kWh per plug, keyed by day so repeated polls overwrite
+rather than accumulate. History therefore starts from first run, and only
+covers days the proxy was running for. Today is excluded from rolling sums
+because it is unfinished.
+
+## Tests
+
+```bash
+python3 test_proxy.py
+```
+
+Fakes the plugs, so it needs no LAN access. Prints `ok`.
+
+## License
+
+GPLv2. See [LICENSE](LICENSE).
+
+## Development Approach
+
+This project is developed using AI-assisted tools. Code is generated with the help of AI based on human-provided specifications, design decisions, and iterative feedback.
+
+All contributions are reviewed, tested, and curated by the maintainer before being included in the codebase. AI is used as a productivity and exploration tool, while human oversight remains central to all decisions.
+
+The goal is to combine the flexibility of AI-assisted development with standard open-source practices such as transparency, review, and accountability.
diff --git a/homepage-services.yaml b/homepage-services.yaml
new file mode 100644
index 0000000..2ee00e6
--- /dev/null
+++ b/homepage-services.yaml
@@ -0,0 +1,126 @@
+# Append to Homepage's services.yaml. Replaces the old single "Presa Tasmota" entry
+# under "Other Local Services" - delete that one.
+#
+# Layout (total on its own row, the 5 plugs on the row below) is set in
+# settings.yaml, not here. See homepage-settings.yaml.
+
+- Consumi:
+    - Totale:
+        icon: mdi-flash
+        href: http://127.0.0.1:8099/graph
+        description: Tutte le prese - consumo e costo
+        widget:
+          type: customapi
+          url: http://127.0.0.1:8099/total
+          refreshInterval: 10000
+          display: list
+          mappings:
+            - field: power_fmt
+              label: Potenza attuale
+            - field: today_fmt
+              label: Oggi
+            - field: yesterday_fmt
+              label: Ieri
+            - field: last7_fmt
+              label: Ultimi 7 giorni
+            - field: last30_fmt
+              label: Ultimi 30 giorni
+            - field: total_fmt
+              label: Storico
+            - field: plugs_ok
+              label: Prese online
+              format: number
+
+- Prese:
+    - Condizionatore:
+        icon: mdi-air-conditioner
+        href: http://172.16.34.176/
+        #description: NOUS A1T
+        widget:
+          type: customapi
+          url: http://127.0.0.1:8099/ac
+          refreshInterval: 10000
+          display: list
+          mappings:
+            - field: power_fmt
+              label: Ora
+            - field: today_fmt
+              label: Oggi
+            - field: yesterday_fmt
+              label: Ieri
+            - field: total_fmt
+              label: Storico
+
+    - Lavatrice:
+        icon: mdi-washing-machine
+        href: http://172.16.34.127/
+        widget:
+          type: customapi
+          url: http://127.0.0.1:8099/washer
+          refreshInterval: 10000
+          display: list
+          mappings:
+            - field: power_fmt
+              label: Ora
+            - field: today_fmt
+              label: Oggi
+            - field: yesterday_fmt
+              label: Ieri
+            - field: total_fmt
+              label: Storico
+
+    - Lavastoviglie:
+        icon: mdi-dishwasher
+        href: http://172.16.34.149/
+        widget:
+          type: customapi
+          url: http://127.0.0.1:8099/dishwasher
+          refreshInterval: 10000
+          display: list
+          mappings:
+            - field: power_fmt
+              label: Ora
+            - field: today_fmt
+              label: Oggi
+            - field: yesterday_fmt
+              label: Ieri
+            - field: total_fmt
+              label: Storico
+
+    - PC e NAS:
+        icon: mdi-server
+        href: http://172.16.34.118/
+        description: UPS - PC, nodi Proxmox, NAS
+        widget:
+          type: customapi
+          url: http://127.0.0.1:8099/pc
+          refreshInterval: 10000
+          display: list
+          mappings:
+            - field: power_fmt
+              label: Ora
+            - field: today_fmt
+              label: Oggi
+            - field: yesterday_fmt
+              label: Ieri
+            - field: total_fmt
+              label: Storico
+
+    - Varie:
+        icon: mdi-power-socket-eu
+        href: http://172.16.34.186/
+        description: friggitrice, forno pizza, ecc
+        widget:
+          type: customapi
+          url: http://127.0.0.1:8099/spare
+          refreshInterval: 10000
+          display: list
+          mappings:
+            - field: power_fmt
+              label: Ora
+            - field: today_fmt
+              label: Oggi
+            - field: yesterday_fmt
+              label: Ieri
+            - field: total_fmt
+              label: Storico
diff --git a/homepage-settings.yaml b/homepage-settings.yaml
new file mode 100644
index 0000000..095b03b
--- /dev/null
+++ b/homepage-settings.yaml
@@ -0,0 +1,21 @@
+# Merge this `layout:` block into Homepage's settings.yaml.
+#
+# The layout block controls rows. `style: row` + `columns:` puts a group's
+# services side by side on one row; without it they stack in a column.
+# Listing every group also fixes their order on the page, so groups you
+# already have must appear here too, or they fall to the bottom.
+
+layout:
+  Consumi:
+    style: row
+    columns: 1        # single full-width card: the total gets its own row
+  Prese:
+    style: row
+    columns: 5        # the 5 plugs side by side on the row below
+
+  # Your other groups go here too. Any group omitted from this block falls to
+  # the bottom of the page, so list them all in the order you want them shown:
+  #
+  # Nome Gruppo:
+  #   style: row
+  #   columns: 3
diff --git a/tasmota-proxy.service b/tasmota-proxy.service
new file mode 100644
index 0000000..1776c42
--- /dev/null
+++ b/tasmota-proxy.service
@@ -0,0 +1,23 @@
+[Unit]
+Description=Tasmota energy proxy for Homepage
+After=network-online.target
+Wants=network-online.target
+
+[Service]
+ExecStart=/usr/bin/python3 /opt/tasmota-proxy/tasmota_proxy.py
+Environment=TASMOTA_PLUGS=ac=172.16.34.176,washer=172.16.34.127,dishwasher=172.16.34.149,pc=172.16.34.118,spare=172.16.34.186
+Environment=PORT=8099
+Environment=RATE_MARGINAL=0.17598
+Environment=RATE_ALLIN=0.2754
+Environment=HISTORY_DB=/var/lib/tasmota-proxy/history.db
+Restart=always
+RestartSec=5
+DynamicUser=yes
+StateDirectory=tasmota-proxy
+NoNewPrivileges=yes
+PrivateTmp=yes
+ProtectSystem=strict
+ProtectHome=yes
+
+[Install]
+WantedBy=multi-user.target
diff --git a/tasmota_proxy.py b/tasmota_proxy.py
new file mode 100755
index 0000000..e1c40d3
--- /dev/null
+++ b/tasmota_proxy.py
@@ -0,0 +1,269 @@
+#!/usr/bin/env python3
+# Copyright (C) 2026 Danilo M. <danix@danix.xyz>
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 as
+# published by the Free Software Foundation.
+#
+# This program 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 this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+"""Fetch Tasmota energy JSON from several plugs, add cost fields, serve for Homepage customapi.
+
+Paths: /<name> for one plug, /total for the sum, /history for per-day kWh,
+/graph for a bar chart page, / for the plug list.
+
+Daily history: Tasmota keeps only Today/Yesterday/Total, so each poll records
+yesterday's finished kWh per plug into SQLite, keyed (day, plug) so repeated
+polls and restarts overwrite rather than accumulate.
+"""
+
+import datetime as dt
+import json
+import os
+import sqlite3
+import urllib.request
+from concurrent.futures import ThreadPoolExecutor
+from http.server import BaseHTTPRequestHandler, ThreadingHTTPServer
+
+# name -> host. Override wholesale with TASMOTA_PLUGS="name=host,name=host".
+PLUGS = dict(
+    p.split("=", 1)
+    for p in os.environ.get(
+        "TASMOTA_PLUGS",
+        "ac=172.16.34.176,washer=172.16.34.127,dishwasher=172.16.34.149,"
+        "pc=172.16.34.118,spare=172.16.34.186",
+    ).split(",")
+)
+PORT = int(os.environ.get("PORT", "8099"))
+# Rates from invoice: marginal = consumption quota only, all-in = total bill / total kWh
+RATE_MARGINAL = float(os.environ.get("RATE_MARGINAL", "0.17598"))
+RATE_ALLIN = float(os.environ.get("RATE_ALLIN", "0.2754"))
+DB = os.environ.get("HISTORY_DB", "/var/lib/tasmota-proxy/history.db")
+
+
+def db():
+    conn = sqlite3.connect(DB, timeout=5)
+    conn.execute(
+        "CREATE TABLE IF NOT EXISTS daily ("
+        "day TEXT, plug TEXT, kwh REAL, PRIMARY KEY (day, plug))"
+    )
+    return conn
+
+
+def record(plugs):
+    """Store yesterday's finished kWh per plug. Idempotent: same day+plug overwrites."""
+    day = (dt.date.today() - dt.timedelta(days=1)).isoformat()
+    rows = [
+        (day, name, p["yesterday_kwh"])
+        for name, p in plugs.items()
+        if "error" not in p
+    ]
+    if not rows:
+        return
+    with db() as conn:
+        conn.executemany("INSERT OR REPLACE INTO daily VALUES (?, ?, ?)", rows)
+
+
+def history(days=30):
+    """Per-day totals across all plugs, oldest first."""
+    since = (dt.date.today() - dt.timedelta(days=days)).isoformat()
+    with db() as conn:
+        rows = conn.execute(
+            "SELECT day, ROUND(SUM(kwh), 3) FROM daily WHERE day >= ? "
+            "GROUP BY day ORDER BY day",
+            (since,),
+        ).fetchall()
+    return [
+        {"day": d, "kwh": k, "cost_allin": round(k * RATE_ALLIN, 2)} for d, k in rows
+    ]
+
+
+def rolling(days):
+    """kWh summed over the last N recorded days (excludes today, which is unfinished)."""
+    since = (dt.date.today() - dt.timedelta(days=days)).isoformat()
+    with db() as conn:
+        (kwh,) = conn.execute(
+            "SELECT COALESCE(SUM(kwh), 0) FROM daily WHERE day >= ?", (since,)
+        ).fetchone()
+    return round(kwh, 3)
+
+
+def watts(power_w):
+    """Human-readable power: kW above 1000 W, W below. Preformatted so no locale
+    separator can turn 1585 W into an ambiguous "1,585"."""
+    if power_w >= 1000:
+        return f"{power_w / 1000:.2f} kW"
+    return f"{power_w:g} W"
+
+
+def kwh_eur(kwh):
+    """One row's worth of text: "0.87 kWh · 0.24 €". Homepage's customapi has no
+    columns, so pairing the two numbers here is what keeps the card two-up."""
+    return f"{kwh:g} kWh · {kwh * RATE_ALLIN:.2f} €"
+
+
+def costs(power_w, today, total):
+    return {
+        "now_hourly_marginal": round(power_w / 1000 * RATE_MARGINAL, 4),
+        "now_hourly_allin": round(power_w / 1000 * RATE_ALLIN, 4),
+        "today_marginal": round(today * RATE_MARGINAL, 2),
+        "today_allin": round(today * RATE_ALLIN, 2),
+        "total_marginal": round(total * RATE_MARGINAL, 2),
+        "total_allin": round(total * RATE_ALLIN, 2),
+    }
+
+
+def fetch(host):
+    url = f"http://{host}/cm?cmnd=Status%2010"
+    with urllib.request.urlopen(url, timeout=5) as r:
+        e = json.load(r)["StatusSNS"]["ENERGY"]
+    return {
+        "power": e["Power"],
+        "power_fmt": watts(e["Power"]),
+        "voltage": e["Voltage"],
+        "current": e["Current"],
+        "today_kwh": e["Today"],
+        "yesterday_kwh": e["Yesterday"],
+        "total_kwh": e["Total"],
+        "today_fmt": kwh_eur(e["Today"]),
+        "yesterday_fmt": kwh_eur(e["Yesterday"]),
+        "total_fmt": kwh_eur(e["Total"]),
+        "cost": costs(e["Power"], e["Today"], e["Total"]),
+    }
+
+
+def fetch_all():
+    """All plugs in parallel; an offline plug yields {"error": ...} instead of failing the batch."""
+    def one(item):
+        name, host = item
+        try:
+            return name, fetch(host)
+        except Exception as exc:  # plug offline, bad JSON, timeout
+            return name, {"error": str(exc)}
+
+    with ThreadPoolExecutor(max_workers=len(PLUGS)) as pool:
+        return dict(pool.map(one, PLUGS.items()))
+
+
+def total():
+    plugs = fetch_all()
+    record(plugs)
+    ok = {n: p for n, p in plugs.items() if "error" not in p}
+    power = sum(p["power"] for p in ok.values())
+    today = sum(p["today_kwh"] for p in ok.values())
+    tot = sum(p["total_kwh"] for p in ok.values())
+    last7, last30 = rolling(7), rolling(30)
+    return {
+        "today_fmt": kwh_eur(round(today, 3)),
+        "yesterday_fmt": kwh_eur(round(sum(p["yesterday_kwh"] for p in ok.values()), 3)),
+        "last7_fmt": kwh_eur(last7),
+        "last30_fmt": kwh_eur(last30),
+        "total_fmt": kwh_eur(round(tot, 3)),
+        "power": round(power, 1),
+        "power_fmt": watts(power),
+        "today_kwh": round(today, 3),
+        "yesterday_kwh": round(sum(p["yesterday_kwh"] for p in ok.values()), 3),
+        "total_kwh": round(tot, 3),
+        "cost": costs(power, today, tot),
+        "plugs_ok": len(ok),
+        "plugs_total": len(plugs),
+        "offline": sorted(set(plugs) - set(ok)),
+        "last7_kwh": last7,
+        "last30_kwh": last30,
+        "last7_allin": round(last7 * RATE_ALLIN, 2),
+        "last30_allin": round(last30 * RATE_ALLIN, 2),
+    }
+
+
+GRAPH_PAGE = """<!doctype html><meta charset=utf-8>
+<title>Consumi giornalieri</title>
+<style>
+ body{{background:#1a1c1e;color:#e8eaed;font:14px system-ui,sans-serif;margin:0;padding:24px}}
+ h1{{font-size:16px;font-weight:600;margin:0 0 4px}}
+ p{{color:#9aa0a6;margin:0 0 24px}}
+ .bars{{display:flex;align-items:flex-end;gap:4px;height:260px;
+        border-bottom:1px solid #3c4043;padding-bottom:2px}}
+ .bar{{flex:1;background:#8ab4f8;border-radius:2px 2px 0 0;min-height:1px}}
+ .bar:hover{{background:#aecbfa}}
+ .labels{{display:flex;gap:4px;margin-top:6px;color:#9aa0a6;font-size:11px}}
+ .labels span{{flex:1;text-align:center;overflow:hidden}}
+ .empty{{color:#9aa0a6;padding:40px 0}}
+</style>
+<h1>Consumi giornalieri</h1>
+<p>{subtitle}</p>
+{body}
+"""
+
+
+def graph_html():
+    rows = history(30)
+    if not rows:
+        return GRAPH_PAGE.format(
+            subtitle="Nessun dato ancora. Una riga per giorno viene registrata "
+                     "dal giorno successivo al primo avvio.",
+            body='<div class=empty>In attesa del primo giorno completo.</div>',
+        )
+    peak = max(r["kwh"] for r in rows) or 1
+    bars = "".join(
+        '<div class=bar style="height:{h:.1f}%" title="{day}: {kwh} kWh - {cost} EUR"></div>'.format(
+            h=r["kwh"] / peak * 100, day=r["day"], kwh=r["kwh"], cost=r["cost_allin"]
+        )
+        for r in rows
+    )
+    labels = "".join("<span>{}</span>".format(r["day"][8:]) for r in rows)
+    tot = round(sum(r["kwh"] for r in rows), 2)
+    return GRAPH_PAGE.format(
+        subtitle="Ultimi {n} giorni - {tot} kWh - {eur} EUR".format(
+            n=len(rows), tot=tot, eur=round(tot * RATE_ALLIN, 2)
+        ),
+        body='<div class=bars>{}</div><div class=labels>{}</div>'.format(bars, labels),
+    )
+
+
+class Handler(BaseHTTPRequestHandler):
+    def do_GET(self):
+        name = self.path.strip("/").split("?")[0]
+        try:
+            if name == "graph":
+                page = graph_html().encode()
+                self.send_response(200)
+                self.send_header("Content-Type", "text/html; charset=utf-8")
+                self.send_header("Content-Length", str(len(page)))
+                self.end_headers()
+                self.wfile.write(page)
+                return
+            if name == "total":
+                body, code = total(), 200
+            elif name == "history":
+                body, code = {"days": history(30)}, 200
+            elif name in PLUGS:
+                body, code = fetch(PLUGS[name]), 200
+            elif not name:
+                body, code = {
+                    "plugs": sorted(PLUGS),
+                    "paths": ["/total", "/history", "/graph"],
+                }, 200
+            else:
+                body, code = {"error": f"unknown plug {name!r}"}, 404
+        except Exception as exc:  # plug offline, bad JSON, timeout
+            body, code = {"error": str(exc)}, 502
+        body = json.dumps(body).encode()
+        self.send_response(code)
+        self.send_header("Content-Type", "application/json")
+        self.send_header("Content-Length", str(len(body)))
+        self.end_headers()
+        self.wfile.write(body)
+
+    def log_message(self, *a):
+        pass  # ponytail: no access log, journald has the unit status
+
+
+if __name__ == "__main__":
+    ThreadingHTTPServer(("127.0.0.1", PORT), Handler).serve_forever()
diff --git a/test_proxy.py b/test_proxy.py
new file mode 100644
index 0000000..e1f1e51
--- /dev/null
+++ b/test_proxy.py
@@ -0,0 +1,119 @@
+#!/usr/bin/env python3
+# Copyright (C) 2026 Danilo M. <danix@danix.xyz>
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 as
+# published by the Free Software Foundation.
+#
+# This program 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 this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+"""Self-check: run `python3 test_proxy.py`. Fakes the plugs, exercises routing and totals."""
+
+import datetime as dt
+import json
+import os
+import tempfile
+import urllib.request
+
+os.environ["HISTORY_DB"] = os.path.join(tempfile.mkdtemp(), "test.db")
+os.environ["TASMOTA_PLUGS"] = "ac=1.1.1.1,washer=2.2.2.2,dead=3.3.3.3"
+os.environ["RATE_MARGINAL"] = "0.1"
+os.environ["RATE_ALLIN"] = "0.2"
+
+import tasmota_proxy as p  # noqa: E402
+
+SAMPLE = {
+    "1.1.1.1": {"Power": 1000, "Voltage": 230, "Current": 4.3,
+                "Today": 2.0, "Yesterday": 1.0, "Total": 10.0},
+    "2.2.2.2": {"Power": 500, "Voltage": 231, "Current": 2.1,
+                "Today": 1.0, "Yesterday": 0.5, "Total": 5.0},
+}
+
+
+class FakeResponse:
+    def __init__(self, host):
+        if host not in SAMPLE:
+            raise OSError("plug offline")
+        self._body = json.dumps({"StatusSNS": {"ENERGY": SAMPLE[host]}})
+
+    def read(self):
+        return self._body.encode()
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, *a):
+        return False
+
+
+p.urllib.request.urlopen = lambda url, timeout=None: FakeResponse(
+    urllib.parse.urlparse(url).hostname
+)
+
+one = p.fetch("1.1.1.1")
+assert one["power"] == 1000, one
+assert one["cost"]["today_allin"] == 0.4, one          # 2.0 kWh * 0.2
+assert one["cost"]["now_hourly_marginal"] == 0.1, one  # 1 kW * 0.1
+
+allp = p.fetch_all()
+assert set(allp) == {"ac", "washer", "dead"}, allp
+assert "error" in allp["dead"], allp                   # offline plug isolated
+assert "error" not in allp["ac"], allp
+
+t = p.total()
+assert t["power"] == 1500, t                           # dead plug excluded, not zero-filled
+assert t["today_kwh"] == 3.0, t
+assert t["cost"]["today_allin"] == 0.6, t
+assert t["plugs_ok"] == 2 and t["plugs_total"] == 3, t
+assert t["offline"] == ["dead"], t
+
+# --- power formatting ---
+# 1585 W -> "1.58 kW": banker's rounding on the exact half, not a typo.
+for w, want in [(1585, "1.58 kW"), (79.7, "79.7 W"), (0, "0 W"),
+                (999, "999 W"), (1000, "1.00 kW"), (2340.5, "2.34 kW")]:
+    assert p.watts(w) == want, (w, p.watts(w), want)
+assert one["power_fmt"] == "1.00 kW", one   # the 1000 W fake plug
+assert p.total()["power_fmt"] == "1.50 kW", p.total()
+
+# --- paired kWh + cost rows ---
+assert p.kwh_eur(2.0) == "2 kWh · 0.40 €", p.kwh_eur(2.0)   # RATE_ALLIN=0.2 here
+assert p.kwh_eur(0) == "0 kWh · 0.00 €", p.kwh_eur(0)
+t = p.total()
+assert one["today_fmt"] == "2 kWh · 0.40 €", one       # per-plug rows
+assert one["total_fmt"] == "10 kWh · 2.00 €", one
+t = p.total()
+assert t["today_fmt"] == "3 kWh · 0.60 €", t                # 2.0 + 1.0, dead skipped
+assert t["total_fmt"] == "15 kWh · 3.00 €", t
+
+# --- daily history ---
+yday = (dt.date.today() - dt.timedelta(days=1)).isoformat()
+
+h = p.history()
+assert h == [{"day": yday, "kwh": 1.5, "cost_allin": 0.3}], h  # 1.0 + 0.5, dead skipped
+
+p.total()  # poll again same day
+h = p.history()
+assert len(h) == 1 and h[0]["kwh"] == 1.5, h  # idempotent, not doubled
+
+# an older day coexists rather than replacing
+with p.db() as c:
+    c.execute("INSERT OR REPLACE INTO daily VALUES (?, ?, ?)",
+              ((dt.date.today() - dt.timedelta(days=3)).isoformat(), "ac", 4.0))
+assert [r["kwh"] for r in p.history()] == [4.0, 1.5], p.history()  # oldest first
+assert p.rolling(7) == 5.5, p.rolling(7)
+assert p.rolling(2) == 1.5, p.rolling(2)  # window excludes the 3-day-old row
+
+t = p.total()
+assert t["last7_kwh"] == 5.5 and t["last7_allin"] == 1.1, t
+
+assert "<div class=bar" in p.graph_html()
+assert "5.5 kWh" in p.graph_html()
+
+print("ok")