# Functional Requirements: Circuit List Inside a Distribution Board

## Scope

This specification focuses only on the circuit list inside one distribution board.

Out of scope for this document:

- project management
- user accounts
- permissions
- full tender export
- CAD integration
- full norm-compliant electrical calculation
- cloud deployment

The first goal is a fast, spreadsheet-like editor for creating, editing, sorting and restructuring circuit lists.

## Sections

The circuit list is grouped into sections.

Default sections:

| Section | Default prefix |
|---|---|
| Lighting | `-1F` |
| Single-phase circuits | `-2F` |
| Three-phase circuits | `-3F` |

Sections are displayed as separator rows in the table, not as normal visible data columns.

Example:

```text
Lighting
-1F1  Beleuchtung Flur
-1F2  Beleuchtung Außen

Single-phase circuits
-2F1  Arbeitsplatzsteckdosen Büro
-2F2  Handtrockner WC

Three-phase circuits
-3F1  Durchlauferhitzer
```

Internally, every circuit belongs to a section. In the UI, the section is shown as a grouping separator.

## Future Section Configuration

Sections and numbering prefixes should later be configurable per project.

Future project configurations may support:

- one continuous numbering sequence without lighting/single-phase/three-phase separation
- numbering grouped by RCD
- numbering grouped by functional area
- custom prefixes and suffixes
- custom section names

The first implementation may use the default sections, but the structure must not permanently hardcode them.

## Circuit Numbering / Equipment Identifiers

Each circuit has an equipment identifier.

Examples:

- `-1F1`
- `-1F2`
- `-2F1`
- `-2F2`
- `-3F1`

Default convention:

- `-1Fx` = lighting circuits
- `-2Fx` = single-phase circuits
- `-3Fx` = three-phase circuits

When a new circuit is created, the next identifier is calculated as:

```text
highest existing number in the section + 1
```

Example:

Existing identifiers in single-phase section:

- `-2F1`
- `-2F2`
- `-2F5`

New circuit receives:

- `-2F6`

Gaps are not filled automatically.

Gaps may be closed only by:

- manually editing equipment identifiers
- explicitly using a renumbering action

## Renumbering

The app must never automatically renumber existing circuits after:

- inserting a circuit
- deleting a circuit
- moving a circuit
- moving a device
- sorting a section
- dragging rows
- changing a device
- synchronizing a linked project device

Renumbering only happens through an explicit user action.

Each section has a "Renumber section" action.

The renumbering action:

- keeps the current visual order
- updates only circuits in that section
- ignores device rows for numbering
- does not affect other sections
- uses the section prefix

## Reserve / Empty Circuits

Empty circuits are allowed.

An empty circuit may be used as a reserve circuit.

If the last device is removed from a circuit, the user may choose:

- keep empty circuit as reserve
- delete circuit completely
- cancel

Reserve circuits remain visible and keep their equipment identifier unless manually changed or explicitly renumbered.