From d2744db4eefffe6ad0a5335755e7b056d0db688e Mon Sep 17 00:00:00 2001
From: sjat <sjat@fisi.nyumbani.baobab.band>
Date: Wed, 24 Jun 2026 14:38:23 +0200
Subject: [PATCH] feat(rack): render mermaid power graph into the rack page

---
 scripts/gen_rack.py    | 47 +++++++++++++++++++++++++++++
 tests/test_gen_rack.py | 67 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 114 insertions(+)

diff --git a/scripts/gen_rack.py b/scripts/gen_rack.py
index 499d162..37d0b68 100644
--- a/scripts/gen_rack.py
+++ b/scripts/gen_rack.py
@@ -292,6 +292,47 @@ def render_svg(rack: str, items: list[dict]) -> str:
     return "\n".join(p) + "\n"
 
 
+def _node_id(name: str) -> str:
+    """A mermaid-safe node id derived from a hostname."""
+    return re.sub(r"[^0-9A-Za-z]", "_", str(name))
+
+
+def render_power(rack: str, items: list[dict]) -> str:
+    """Return a mermaid power-distribution flowchart, or '' if no feeds."""
+    powered = [fm for fm in items if fm.get("power")]
+    if not powered:
+        return ""
+    pdus = _pdu_index(items)
+
+    edges: list[tuple[str, int, str]] = []
+    for fm in powered:
+        device = fm.get("hostname", "?")
+        for feed in fm["power"]:
+            edges.append((feed["pdu"], feed["outlet"], device))
+    edges.sort()
+
+    lines: list[str] = ["```mermaid", "flowchart LR"]
+    for pdu in sorted(pdus):
+        outlets = pdus[pdu].get("outlets")
+        lines.append(f'    {_node_id(pdu)}["{pdu}<br/>{outlets} outlets"]')
+    devices = sorted(
+        powered,
+        key=lambda i: (
+            i.get("rack_u", 0) if isinstance(i.get("rack_u"), int) else 0,
+            i.get("hostname", ""),
+        ),
+    )
+    for fm in devices:
+        device = fm.get("hostname", "?")
+        lines.append(f'    {_node_id(device)}["{device}"]')
+    for pdu, outlet, device in edges:
+        lines.append(
+            f"    {_node_id(pdu)} -->|outlet {outlet}| {_node_id(device)}"
+        )
+    lines.append("```")
+    return "\n".join(lines) + "\n"
+
+
 def render_page(rack: str, items: list[dict]) -> str:
     items = _sorted_items(items)
     lines: list[str] = []
@@ -307,6 +348,12 @@ def render_page(rack: str, items: list[dict]) -> str:
     lines.append("")
     lines.append(f"![Rack {rack} elevation]({rack}-elevation.svg)")
     lines.append("")
+    power = render_power(rack, items)
+    if power:
+        lines.append("## Power")
+        lines.append("")
+        lines.append(power.rstrip())
+        lines.append("")
     lines.append("## Occupancy")
     lines.append("")
     lines.append("| U | Device | Kind | Face | Status |")
diff --git a/tests/test_gen_rack.py b/tests/test_gen_rack.py
index 875c3a4..6ecd93c 100644
--- a/tests/test_gen_rack.py
+++ b/tests/test_gen_rack.py
@@ -275,3 +275,70 @@ def test_generate_returns_1_on_bad_power_ref(tmp_path):
     rc = gen_rack.generate(hw, out)
     assert rc == 1
     assert not (out / "rack01.md").exists()
+
+
+def test_render_power_has_nodes_and_edge_labels():
+    items = [
+        item(hostname="pdu01", kind="pdu", rack_face="left", outlets=8),
+        item(hostname="mf00", rack_u=1, u_height=1, rack_face="front",
+             power=[{"pdu": "pdu01", "outlet": 3}]),
+    ]
+    out = gen_rack.render_power("rack01", items)
+    assert "```mermaid" in out
+    assert "flowchart LR" in out
+    assert "pdu01" in out
+    assert "8 outlets" in out
+    assert "outlet 3" in out
+    assert "mf00" in out
+
+
+def test_render_power_redundant_device_has_two_edges():
+    items = [
+        item(hostname="pdu01", kind="pdu", rack_face="left", outlets=8),
+        item(hostname="pdu02", kind="pdu", rack_face="right", outlets=8),
+        item(hostname="mf00", rack_u=1, u_height=1, rack_face="front",
+             power=[{"pdu": "pdu01", "outlet": 1},
+                    {"pdu": "pdu02", "outlet": 1}]),
+    ]
+    out = gen_rack.render_power("rack01", items)
+    assert out.count("-->|outlet") == 2
+
+
+def test_render_power_empty_when_no_feeds():
+    items = [item(hostname="mf00", rack_u=1, u_height=1, rack_face="front")]
+    assert gen_rack.render_power("rack01", items) == ""
+
+
+def test_render_power_is_deterministic():
+    a = item(hostname="pdu01", kind="pdu", rack_face="left", outlets=8)
+    b = item(hostname="mf01", rack_u=2, u_height=1, rack_face="front",
+             power=[{"pdu": "pdu01", "outlet": 2}])
+    c = item(hostname="mf00", rack_u=1, u_height=1, rack_face="front",
+             power=[{"pdu": "pdu01", "outlet": 1}])
+    assert gen_rack.render_power("rack01", [a, b, c]) == \
+        gen_rack.render_power("rack01", [c, b, a])
+
+
+def test_generate_includes_power_section(tmp_path):
+    hw = tmp_path / "hardware"
+    out = tmp_path / "out"
+    hw.mkdir()
+    _write_item(
+        hw,
+        "pdu01",
+        "---\nhostname: pdu01\nkind: pdu\nstatus: in-use\n"
+        "rack: rack01\nrack_face: left\noutlets: 8\n---\n",
+    )
+    _write_item(
+        hw,
+        "mf00",
+        "---\nhostname: mf00\nkind: server\nstatus: in-use\n"
+        "rack: rack01\nrack_u: 1\nu_height: 1\nrack_face: front\n"
+        "power:\n  - { pdu: pdu01, outlet: 1 }\n---\n",
+    )
+    rc = gen_rack.generate(hw, out)
+    assert rc == 0
+    page = (out / "rack01.md").read_text()
+    assert "## Power" in page
+    assert "```mermaid" in page
+    assert "outlet 1" in page