# Migration Guide

This guide covers changes between the git tag `release` and the current tree.
At `release`, `masque.__version__` was `3.3`; the current tree reports `3.4`.

Most downstream changes are in `masque/builder/*`, but there are a few other
API changes that may require code updates.

## Routing API: renamed and consolidated

The routing helpers were consolidated into a single implementation in
`masque/builder/pather.py`.

The biggest migration point is that the old routing verbs were renamed:

| Old API | New API |
| --- | --- |
| `Pather.path(...)` | `Pather.trace(...)` |
| `Pather.path_to(...)` | `Pather.trace_to(...)` |
| `Pather.mpath(...)` | `Pather.trace(...)` / `Pather.trace_to(...)` with multiple ports |
| `Pather.pathS(...)` | `Pather.jog(...)` |
| `Pather.pathU(...)` | `Pather.uturn(...)` |
| `Pather.path_into(...)` | `Pather.trace_into(...)` |
| `Pather.path_from(src, dst)` | `Pather.at(src).trace_into(dst)` |
| `RenderPather.path(...)` | `Pather(..., auto_render=False).trace(...)` |
| `RenderPather.path_to(...)` | `Pather(..., auto_render=False).trace_to(...)` |
| `RenderPather.mpath(...)` | `Pather(..., auto_render=False).trace(...)` / `Pather(..., auto_render=False).trace_to(...)` |
| `RenderPather.pathS(...)` | `Pather(..., auto_render=False).jog(...)` |
| `RenderPather.pathU(...)` | `Pather(..., auto_render=False).uturn(...)` |
| `RenderPather.path_into(...)` | `Pather(..., auto_render=False).trace_into(...)` |
| `RenderPather.path_from(src, dst)` | `Pather(..., auto_render=False).at(src).trace_into(dst)` |

There are also new convenience wrappers:

- `straight(...)` for `trace_to(..., ccw=None, ...)`
- `ccw(...)` for `trace_to(..., ccw=True, ...)`
- `cw(...)` for `trace_to(..., ccw=False, ...)`
- `jog(...)` for S-bends
- `uturn(...)` for U-bends

Important: `Pather.path()` is no longer the routing API. It now forwards to
`Pattern.path()` and creates a geometric `Path` element. Any old routing code
that still calls `pather.path(...)` must be renamed.

### Common rewrites

```python
# old
pather.path('VCC', False, 6_000)
pather.path_to('VCC', None, x=0)
pather.mpath(['GND', 'VCC'], True, xmax=-10_000, spacing=5_000)
pather.pathS('VCC', offset=-2_000, length=8_000)
pather.pathU('VCC', offset=4_000, length=5_000)
pather.path_into('src', 'dst')
pather.path_from('src', 'dst')

# new
pather.cw('VCC', 6_000)
pather.straight('VCC', x=0)
pather.ccw(['GND', 'VCC'], xmax=-10_000, spacing=5_000)
pather.jog('VCC', offset=-2_000, length=8_000)
pather.uturn('VCC', offset=4_000, length=5_000)
pather.trace_into('src', 'dst')
pather.at('src').trace_into('dst')
```

If you prefer the more explicit spelling, `trace(...)` and `trace_to(...)`
remain the underlying primitives:

```python
pather.trace('VCC', False, 6_000)
pather.trace_to('VCC', None, x=0)
```

## `PortPather` and `.at(...)`

Routing can now be written in a fluent style via `.at(...)`, which returns a
`PortPather`.

```python
(rpather.at('VCC')
    .trace(False, length=6_000)
    .trace_to(None, x=0)
)
```

This is additive, not required for migration. Existing code can stay with the
non-fluent `Pather` methods after renaming the verbs above.

Old `PortPather` helper names were also cleaned up:

| Old API | New API |
| --- | --- |
| `save_copy(...)` | `mark(...)` |
| `rename_to(...)` | `rename(...)` |

Example:

```python
# old
pp.save_copy('branch')
pp.rename_to('feed')

# new
pp.mark('branch')
pp.rename('feed')
```

## Imports and module layout

`Pather` now provides the remaining builder/routing surface in
`masque/builder/pather.py`. The old module files
`masque/builder/builder.py` and `masque/builder/renderpather.py` were removed.

Update imports like this:

```python
# old
from masque.builder.builder import Builder
from masque.builder.renderpather import RenderPather

# new
from masque.builder import Pather

builder = Pather(...)
deferred = Pather(..., auto_render=False)
```

Top-level imports from `masque` also continue to work.

`Pather` now defaults to `auto_render=True`, so plain construction replaces the
old `Builder` behavior. Use `Pather(..., auto_render=False)` where you
previously used `RenderPather`.

## `BasicTool` was replaced

`BasicTool` is no longer exported. Use `AutoTool` for reusable straight, bend,
transition, and S-bend primitives.

### Old `BasicTool`

```python
from masque.builder.tools import BasicTool

tool = BasicTool(
    straight=(make_straight, 'input', 'output'),
    bend=(lib.abstract('bend'), 'input', 'output'),
    transitions={
        'm2wire': (lib.abstract('via'), 'top', 'bottom'),
    },
)
```

### New `AutoTool`

```python
from masque.builder import AutoTool

tool = (
    AutoTool()
    .add_straight(make_straight, 'm1wire', 'input')
    .add_bend(lib.abstract('bend'), 'input', 'output', clockwise=True)
    .add_transition(lib.abstract('via'), 'top', 'bottom')
)
```

The key differences are:

- `BasicTool` -> `AutoTool`
- `straight=(fn, in_name, out_name)` -> `add_straight(fn, ptype, in_name)`
- `bend=(abstract, in_name, out_name)` -> `add_bend(abstract, in_name, out_name)`
- transitions are registered with `add_transition(abstract, external_port, internal_port)`
- transitions are bidirectional by default; pass `one_way=True` to inhibit the reverse adapter

## Custom `Tool` subclasses

If you maintain your own `Tool` subclass, the interface changed:

- `primitive_offers()` is now the planning boundary
- `render()` consumes committed primitive render tokens
- `Tool.path(...)`, `traceL()`, `traceS()`, `traceU()`, `planL()`,
  `planS()`, and `planU()` are no longer part of the public `Tool` API

In practice, a minimal old implementation like:

```python
class MyTool(Tool):
    def path(self, ccw, length, **kwargs):
        ...
```

should now become:

```python
from collections.abc import Sequence
from typing import Any

from masque import Port
from masque.builder import RenderStep, StraightOffer, Tool


class MyTool(Tool):
    def primitive_offers(self, kind, *, in_ptype=None, out_ptype=None, **kwargs):
        if kind != 'straight':
            return ()

        def endpoint(length):
            ptype = out_ptype or in_ptype
            return Port((length, 0), rotation=3.141592653589793, ptype=ptype)

        def commit(length):
            return {'length': length}

        return (StraightOffer(
            in_ptype=in_ptype,
            out_ptype=out_ptype or in_ptype,
            endpoint_planner=endpoint,
            commit_planner=commit,
            ),)

    def render(self, batch: Sequence[RenderStep], **kwargs: Any):
        ...
```

If a tool does not provide a primitive kind, return `()` for that kind. `Pather`
will compose available primitive offers where the route family allows it.

### Primitive offers

Tools describe legal routing primitives through `Tool.primitive_offers()`.
`Pather` composes those primitive offers to implement `trace()`, `jog()`,
`uturn()`, and `trace_into()`.

For custom tools, construct the concrete offer class that matches the primitive
you are exposing:

- `StraightOffer` for non-turning length-parameterized primitives
- `BendOffer` for single-turn length-parameterized primitives
- `SOffer` for S-like jog-parameterized primitives
- `UOffer` for U-like jog-parameterized primitives

`PrimitiveOffer` is the shared base type used for generic annotations and
common callback behavior. It is not the normal class users should instantiate.
The concrete offer classes carry the semantic fields (`length_domain`,
`jog_domain`, `ccw`) so tools do not need to encode primitive identity in
strings.

Minimal straight-only example:

```python
from collections.abc import Sequence
from typing import Literal

from masque import Port
from masque.builder import RenderStep, StraightOffer, Tool


class MyTool(Tool):
    def primitive_offers(
            self,
            kind: Literal['straight', 'bend', 's', 'u'],
            *,
            in_ptype=None,
            out_ptype=None,
            **kwargs,
            ):
        if kind != 'straight':
            return ()

        def endpoint(length):
            ptype = out_ptype or in_ptype
            return Port((length, 0), rotation=3.141592653589793, ptype=ptype)

        def commit(length):
            return {'length': length}

        return (StraightOffer(
            in_ptype=in_ptype,
            out_ptype=out_ptype or in_ptype,
            endpoint_planner=endpoint,
            commit_planner=commit,
            ),)

    def render(self, batch: Sequence[RenderStep], **kwargs):
        ...
```

Primitive offers are local planning objects:

- `endpoint_at(parameter)` returns the local output `Port`
- `cost_at(parameter)` returns an additive scalar route-selection cost
- `bbox_at(parameter)` returns local primitive bounds when a footprint hook is supplied
- `parameterized_bbox` may carry opaque future-router footprint metadata
- `commit(parameter)` returns opaque render data consumed later by `render()`
- `(min, max)` parameter domains are half-open; `(value, value)` is a fixed singleton
- selected parameter values must be finite; domains may use infinite open bounds but not `NaN`
- `None` and `"unk"` ptypes are wildcards; concrete ptype mismatches reject an offer

Heterogeneous `StraightOffer` and `SOffer` objects may be used as ptype
adapters. Requested `out_ptype` constrains only the final route endpoint; any
intermediate ptypes are chosen by the route solver.

`Tool` subclasses must override `primitive_offers()` and return `()` themselves
for recognized unsupported kinds. There is no route-level `plan*()` fallback.
Omitted-length S/U behavior comes from direct `SOffer` and `UOffer` endpoint
domains or from composed straight/bend primitives.

Offer constructors accept split `endpoint_planner` and `commit_planner`
callbacks. Provide both callbacks or override the offer methods in a subclass;
partial callback configurations are rejected during offer construction.

When writing direct primitive offers, declare the actual endpoint ptype
produced by the offer if it can differ from the requested value; `Pather`
validates evaluated endpoints against the declared offer ptype.

Stable imports for custom tool authors live in `masque.builder`. The
`masque.builder.planner` module is an internal planner implementation; do not
import it from user code.

`trace_into()` uses the same primitive-offer route selection and now searches
bounded route topologies with up to four bend roles. This preserves the common
straight, bend, S-like, U-like, and dogleg cases while allowing routes that
need an additional bounded bend pair. Among legal bounded candidates,
`trace_into()` selects the lowest total primitive-offer cost; bend count and
step count are used only to break exact cost ties.

Explicit-length `jog()` routes may also be satisfied by composing a straight
primitive before or after an omitted-length native S primitive. `uturn()` routes
may compose a straight primitive before an omitted-length native U primitive.
These compositions are used when they are the lowest-cost legal route for the
explicit request.

`AutoTool` can attach `bbox_at()` hooks to its primitive offers by rendering the
selected primitive into a temporary pattern and measuring it. If the rendered
primitive contains reusable refs, pass the source library as `bbox_library=...`;
normal routing does not require this.

### Omitted-length routing

Single-port omitted-length calls now evaluate legal primitive routes at their
minimum legal length-like parameter, or at their intrinsic endpoint length when
the requested offset fixes the primitive geometry. Cost then selects among
those minimum-length candidates:

```python
pather.trace('A', None)     # minimum straight-like route
pather.jog('A', offset=2)   # minimum S-like route for that offset
pather.uturn('A', offset=4) # minimum U-like route for that offset
```

For U-turns, use explicit `length=0` to request the old zero-public-length
shape:

```python
pather.uturn('A', offset=4, length=0)
```

## Transform semantics changed

The other major user-visible change is that `mirror()` and `rotate()` are now
treated more consistently as intrinsic transforms on low-level objects.

The practical migration rule is:

- use `mirror()` / `rotate()` when you want to change the object relative to its
  own origin
- use `flip_across(...)`, `rotate_around(...)`, or container-level transforms
  when you want to move the object in its parent coordinate system

### Example: `Port`

Old behavior:

```python
port.mirror(0)   # changed both offset and orientation
```

New behavior:

```python
port.mirror(0)          # changes orientation only
port.flip_across(axis=0)  # old "mirror in the parent pattern" behavior
```

### What to audit

Check code that calls:

- `Port.mirror(...)`
- `Ref.rotate(...)`
- `Ref.mirror(...)`
- `Label.rotate_around(...)` / `Label.mirror(...)`

If that code expected offsets or repetition grids to move automatically, it
needs updating. For whole-pattern transforms, prefer calling `Pattern.mirror()`
or `Pattern.rotate_around(...)` at the container level.

## Other user-facing changes

### DXF environments

If you install the DXF extra, the supported `ezdxf` baseline moved from
`~=1.0.2` to `~=1.4`. Any pinned environments should be updated accordingly.

### New exports

These are additive, but available now from `masque` and `masque.builder`:

- `PortPather`
- `AutoTool`
- `boolean`

## Minimal migration checklist

If your code uses the routing stack, do these first:

1. Replace `path`/`path_to`/`mpath`/`path_into` calls with
   `trace`/`trace_to`/multi-port `trace`/`trace_into`.
2. Replace `BasicTool` with `AutoTool`.
3. Fix imports that still reference `masque.builder.builder` or
   `masque.builder.renderpather`.
4. Audit any low-level `mirror()` usage, especially on `Port` and `Ref`.

If your code only uses `Pattern`, `Library`, `place()`, and `plug()` without the
routing helpers, you may not need any changes beyond the transform audit and any
stale imports.