# Core v2 API reference

`@native-vue-router/core-v2` is a routeless Vue scene compositor. A mounted
component can create another component, animate both through a local operation
frame, and retain either side when the operation resolves.

This document describes the experimental `0.1.0-experimental.0` API.

## Contents

- [Gesture start recognition](#gesture-start-recognition)
- [Minimum setup](#minimum-setup)
- [Components](#components)
- [Nested scenes](#nested-scenes)
- [Scene and view functions](#scene-and-view-functions)
- [Actions and history](#actions-and-history)
- [Gestures](#gestures)
- [Choreographies and effects](#choreographies-and-effects)
- [Node-scoped controls](#node-scoped-controls)
- [Scene diagnostics and manual operations](#scene-diagnostics-and-manual-operations)
- [Type reference](#type-reference)
- [Errors and constraints](#errors-and-constraints)

## Gesture start recognition

The builder separates where a gesture begins from the direction it moves:

```ts
const edgeBack = gesture.from
  .left("clamp(24px, 7vw, 48px)")
  .to.right()
  .navigate((context) => (context.canGoBack ? back() : null))
  .animate(slideRight);
```

Edges are measured from the **gesture host element**, not unconditionally from
the browser viewport. Supported start rules are:

```ts
gesture.from.left(distance);
gesture.from.right(distance);
gesture.from.top(distance);
gesture.from.bottom(distance);
gesture.from.anywhere();
gesture.from.when(predicate);
```

`distance` accepts a number in CSS pixels or a CSS length string, including
percentages, `calc()`, and `clamp()`. It is resolved against the current host
size at pointer-down.

`.from` is optional. A chain beginning at `.to` admits pointer-down anywhere:

```ts
gesture.to.right();
```

This is semantically equivalent to:

```ts
gesture.from.anywhere().to.right();
```

It does not capture on the first positive pixel. The recognizer waits until
directed movement crosses the intent threshold and dominates the cross-axis.

Custom shapes, safe-area rules, and exclusion zones belong in `.from.when()`:

```ts
const dropDialog = gesture.from
  .when(({ point, bounds, event }) => {
    const rail = Math.max(36, bounds.width * 0.08);
    const outsideExcludedBand =
      event.clientY < bounds.top + bounds.height * 0.35 ||
      event.clientY > bounds.top + bounds.height * 0.65;
    return point.localX <= rail && outsideExcludedBand;
  })
  .to.down()
  .navigate(() => above(originView(DialogView)))
  .animate(dropAnimation);
```

Interactive form controls are ignored automatically. Add
`data-origin-gesture="ignore"` to any other element or ancestor that should not
begin a gesture.

## Minimum setup

Import the required compositor stylesheet once:

```ts
import "@native-vue-router/core-v2/style.css";
```

Create a scene:

```ts
import { createOriginScene, originView } from "@native-vue-router/core-v2";
import HomeView from "./HomeView.vue";

export const scene = createOriginScene({
  initial: originView(HomeView, undefined, {
    key: "home",
    name: "Home",
  }),
});
```

Render it:

```vue
<script setup lang="ts">
import { OriginScene } from "@native-vue-router/core-v2";
import { scene } from "./scene";
</script>

<template>
  <OriginScene :scene="scene" />
</template>
```

`OriginScene` must have a non-zero width and height through its parent layout.

## Components

### `OriginScene`

Renders every currently mounted scene node as a stable, absolutely positioned
sibling.

| Prop    | Type          | Required | Description                            |
| ------- | ------------- | -------- | -------------------------------------- |
| `scene` | `OriginScene` | yes      | Scene created by `createOriginScene()` |

The component provides node ownership to descendants, registers host elements
for measurement, and applies the scene's composited styles. Application views
must be rendered through this component before calling `useOrigin()` or
`useOriginGesture()`.

### `OriginGesture`

Convenience component that renders one HTML element and binds one gesture
recognizer to it.

| Prop      | Type                      | Default | Description                        |
| --------- | ------------------------- | ------- | ---------------------------------- |
| `as`      | `string`                  | `"div"` | HTML tag used for the gesture host |
| `gesture` | `OriginGestureDefinition` | —       | Preferred builder definition       |

Attributes, classes, and listeners not consumed as props are forwarded to the
rendered host.

```vue
<OriginGesture as="main" class="profile" :gesture="openDetailsGesture">
  ...
</OriginGesture>
```

For compatibility, the component also accepts the legacy mutually exclusive
set of `direction`, `edge`, `threshold`, and `action` props.

Use `useOriginGesture()` instead when an extra wrapper is undesirable.

### `OriginGestureSurface`

Policy-neutral host for multiple completed builder definitions:

```vue
<script setup lang="ts">
const gestures = [forwardGesture, backGesture] as const;
</script>

<template>
  <OriginGestureSurface as="main" :gestures="gestures">
    ...
  </OriginGestureSurface>
</template>
```

| Prop       | Type                                 | Default  | Description                    |
| ---------- | ------------------------------------ | -------- | ------------------------------ |
| `as`       | `string`                             | `"div"`  | Shared native gesture host     |
| `gestures` | `readonly OriginGestureDefinition[]` | required | Fully defined page-owned rules |

The component adds no recognition or navigation policy. It installs each
definition with `useOriginGesture()`, forwards every pointer event to every
binding, and derives the least-permissive shared `touch-action`:

- horizontal only: `pan-y`;
- vertical only: `pan-x`;
- both axes: `none`.

Definitions should be immutable and stable for the lifetime of the rendered
surface. The owning page remains the visible declaration point for every
`.from`, `.to`, `.complete`, `.navigate`, and `.animate` choice.

## Nested scenes

`OriginScene` is a reusable compositor, not an application-only singleton. A
component may render another scene inside its own layout:

```vue
<section class="carousel">
  <OriginScene :scene="carouselScene" />
</section>
```

The child scene gets independent mounted nodes, retained history, measurements,
operations, and clipping. `useOrigin()` and `useOriginGesture()` resolve the
nearest scene-node provider, so declarations inside a carousel slide operate
on carousel components rather than the outer page.

Parent/child gesture arbitration is currently pointer-down based. An eligible
child recognizer stops propagation immediately. If its later `.navigate()`
factory returns `null`, that same pointer sequence is not offered to the
parent. Cooperative nested components should reserve a start region with
`.from.when()` or `.from.left()` that allows the parent handler to receive
pointer-down.

The nested-scenes demo contains both this cooperative policy and an intentional
greedy-child conflict. A future gesture arena could delay ownership until
direction and navigation availability are known.

## Scene and view functions

### `originView(component, props?, options?)`

Creates a lightweight recipe for mounting a Vue component.

```ts
const profile = originView(
  ProfileView,
  { userId: "42" },
  { key: "profile-42", name: "Profile" },
);
```

The recipe is not itself a mounted instance. A forward action creates an
instance from it, then retains that exact instance while its entry remains in
history. Back does not call the recipe again. Component definitions are marked
raw so Vue does not proxy them inside reactive scene structures.

`OriginViewOptions`:

| Field  | Type     | Description                                   |
| ------ | -------- | --------------------------------------------- |
| `key`  | `string` | Recipe identity and generated node-key prefix |
| `name` | `string` | Human-readable diagnostic label               |

When no key is supplied, one is generated from the component/name and a
sequence number.

### `createOriginScene(options)`

Creates one independent scene graph, history context, and compositor.

```ts
const scene = createOriginScene({
  initial: originView(HomeView),
});
```

`options.initial` accepts one `OriginView` or an array of independent root
views. Scenes do not share nodes, history, operation IDs, or measurements.

## Actions and history

### `forward(target, choreography?, options?)`

With choreography, creates a complete retained-history push action:

```ts
const openProfile = () =>
  forward(originView(ProfileView, { userId: "42" }), slideLeft);
```

Without choreography, it creates an `OriginNavigationIntent` for a gesture
builder:

```ts
.navigate(() => forward(originView(ProfileView, { userId: "42" })))
```

When forward commits, the origin remains mounted but becomes parked. Its DOM,
component-local state, and nested scroll positions remain intact.

`OriginNavigationActionOptions.placement` defaults to `"above"`.

### `back(choreography?, options?)`

Creates a retained-history pop action:

```ts
const goBack = (context: OriginContext) =>
  context.canGoBack ? back(slideRight) : null;
```

Back has no target recipe. When it begins, the scene resolves the origin's
`previousNodeKey` and reveals that exact mounted instance. A committed back
unmounts only the current entry. A cancelled back hides the previous entry
again and leaves the current entry active.

`back()` without choreography returns an animation-free navigation intent for
`.navigate()`. `back(slideRight)` returns a complete programmatic action.

`OriginNavigationActionOptions.placement` defaults to `"under"`.

### `replace(target, choreography?, options?)`

Creates a new target while removing the current history entry:

```ts
const confirmOrder = () =>
  replace(
    originView(OrderConfirmationView, { orderId: "NVO-2048" }),
    slideLeft,
  );
```

The target inherits the origin's `previousNodeKey`, so a later back skips the
replaced entry. The origin remains mounted while the operation is interactive
or settling and is unmounted only after commit. Cancelling removes the proposed
target and restores the origin without changing history.

Without choreography, `replace(target)` creates an intent suitable for a
gesture builder:

```ts
.navigate(() => replace(originView(OrderConfirmationView)))
.animate(slideLeft)
```

`OriginNavigationActionOptions.placement` defaults to `"above"`.

### `originAction(target, choreography, options?)`

Constructs a complete low-level `OriginAction`. Prefer `forward()`, `replace()`,
and `back()` when expressing retained navigation.

```ts
const action = originAction(profile, slideLeft, {
  placement: "above",
  history: "push",
});
```

`OriginActionOptions`:

| Field       | Type                 | Default   | Description                  |
| ----------- | -------------------- | --------- | ---------------------------- |
| `placement` | `"above" \| "under"` | `"above"` | Target stacking relationship |
| `history`   | `OriginHistoryMode`  | `"push"`  | Target history mutation      |

### `above(target, choreography?, options?)`

Shorthand for `originAction()` with `placement: "above"`.

```ts
const openProfile = () => above(originView(ProfileView), slideLeft);
```

Placement controls stacking only. It does not imply a movement direction.
Omitting choreography returns a navigation intent for a gesture builder.

### `under(target, choreography?, options?)`

Shorthand for `originAction()` with `placement: "under"`.

```ts
const goBack = (context: OriginContext) =>
  context.previous ? back(slideRight) : null;
```

`under()` does not automatically mean history back. It remains available for
custom stacking actions; `back()` is the clearer retained-history primitive.
Omitting choreography returns a navigation intent for a gesture builder.

### History modes

History is a linked chain of mounted scene nodes.

| Mode        | Commit behavior                                                |
| ----------- | -------------------------------------------------------------- |
| `"push"`    | Park and retain the origin; activate the new target            |
| `"replace"` | Create a new target, inherit prior history, unmount the origin |
| `"back"`    | Reuse the retained previous target; pop and unmount the origin |

Parked entries are `inert`, `aria-hidden`, invisible, and excluded from pointer
input. They remain mounted until back pops them or the scene is destroyed.

## Gestures

### `gesture`

Immutable fluent builder for component-owned gesture policy:

```ts
const swipeBack = gesture.from
  .left(32)
  .to.right({ threshold: 10 })
  .complete(({ progress, velocity }) => progress >= 0.4 || velocity >= 0.9)
  .navigate((context) => (context.canGoBack ? back() : null))
  .animate(slideRight);
```

The stages have distinct responsibilities:

| Stage                  | Responsibility                                             |
| ---------------------- | ---------------------------------------------------------- |
| `.from.*`              | Optional pointer-down eligibility                          |
| `.to.*`                | Required movement direction and intent-recognition options |
| `.complete(predicate)` | Optional release commit/cancel decision                    |
| `.navigate(factory)`   | Required target and retained-history intent                |
| `.animate(routine)`    | Required source/target/frame choreography                  |

The builder is persistent and immutable. Reusing an earlier stage cannot
change a definition already produced from it.

`.to.left()`, `.to.right()`, `.to.up()`, and `.to.down()` accept optional
`OriginGestureDirectionOptions`:

| Field           | Default | Description                                       |
| --------------- | ------- | ------------------------------------------------- |
| `threshold`     | `8`     | Directed CSS pixels required before capture       |
| `axisDominance` | `1.15`  | Directed/cross-axis ratio required before capture |

If `.complete()` is omitted, the choreography's `commitThreshold` and
`commitVelocity` decide release normally.

The completion context contains the origin, direction, normalized progress and
velocity, directed pixel distance, cross-axis distance, duration, pointer-up
event, host, bounds, and start/current points. Completion predicates are
synchronous because they select operation intent at release.

### `useOriginGesture(definition)`

Creates one primary-pointer, single-axis recognizer owned by the component that
calls it.

```ts
const open = useOriginGesture(
  gesture.to
    .left({ threshold: 10 })
    .navigate(() => forward(originView(DetailsView)))
    .animate(slideLeft),
);
```

The return value contains:

```ts
interface OriginGestureBinding {
  readonly style: Readonly<CSSProperties>;
  readonly onPointerdown: (event: PointerEvent) => void;
  readonly onPointermove: (event: PointerEvent) => void;
  readonly onPointerup: (event: PointerEvent) => void;
  readonly onPointercancel: () => void;
}
```

Apply all handlers to the same element. The returned style sets dimensions and
`touch-action` so native scrolling remains available on the cross-axis.

Recognition requires:

1. A primary, left-button pointer satisfies the optional start policy.
2. The target is not an ignored interactive element.
3. Directed movement reaches `threshold`.
4. Directed movement exceeds cross-axis movement by `axisDominance`.
5. The navigation factory returns an intent.

Progress is directed distance divided by host width or height. Release velocity
is normalized by the same dimension.

An asynchronous navigation factory is supported. If it resolves after the
pointer was released or cancelled, the stale result is discarded.

The legacy `OriginGestureOptions` object remains accepted. Its `edge` is a
number inferred from the side opposite `direction`, matching the previous API.

## Choreographies and effects

### `defineOriginChoreography(choreography)`

Type-safe identity helper for declaring custom visual routines.

```ts
const scaleIn = defineOriginChoreography({
  name: "scale-in",
  commitThreshold: 0.4,
  commitVelocity: 0.8,
  effects: ({ progress, viewport }) => ({
    source: {
      transform: `scale(${1 - progress * 0.08})`,
      opacity: 1 - progress * 0.3,
    },
    target: {
      transform: `translateY(${(1 - progress) * viewport.height}px)`,
    },
  }),
});
```

The function returns the same object. Its value is type checking and a clear
construction point.

Set `persistAtRest: true` when progress `1` should remain as a connected visual
relationship after a committed push:

```ts
const openPartialDrawer = defineOriginChoreography({
  name: "partial-drawer-open",
  persistAtRest: true,
  effects: ({ progress }) => ({
    source: {
      transform: `translateX(${progress * 66.6667}%)`,
    },
    target: {
      transform: `translateX(${(progress - 1) * 66.6667}%)`,
    },
  }),
});
```

This leaves the retained source mounted, visible, and inert instead of parking
it. The target remains the active history entry. Beginning back suspends the
resting relationship so a reciprocal close choreography can take over;
cancelling back restores it exactly.

Connected resting effects are supported only by retained-history push actions.
They are designed for partial drawers, inspectors, and other presentations
where both mounted views remain visible after commit. They do not appear in
`scene.operations`, which reports live interactive/settling edges only.

`effects()` may return:

| Effect   | Applied to                                                 |
| -------- | ---------------------------------------------------------- |
| `frame`  | Source, target, and descendants on both sides of this edge |
| `source` | Component that originated this operation                   |
| `target` | Component created by this operation and its descendants    |

Transforms are concatenated from inherited frames to local frames. Opacity is
multiplied. Properties inside `style` use local-last precedence, except
`transform` and numeric `opacity`, which are also composed.

Choreography callbacks should be deterministic and free of side effects. They
can run repeatedly during rendering and animation.

### Commit thresholds

When `finish()` does not explicitly override the decision, a target commits
when either:

- `progress >= commitThreshold`, default `0.36`; or
- `progress >= 0.06` and `velocity >= commitVelocity`, default `0.9`.

The operation's intent becomes final before its spring settles.

### Included presets

| Export       | Behavior                                                      |
| ------------ | ------------------------------------------------------------- |
| `slideLeft`  | Target enters from the right above a slightly receding source |
| `slideRight` | Source exits right and reveals a target underneath            |
| `fade`       | Source fades out as target fades in                           |

These are ordinary `OriginChoreography` objects and can be replaced entirely.

### `normalizedEffect(effect, fallbackLayer?)`

Internal compositor helper exposed for custom diagnostics or compositors. It
returns a defined effect and adds `fallbackLayer` to the effect's own layer.
Applications normally return plain effects and let the scene normalize them.

## Node-scoped controls

### `useOrigin()`

Returns controls scoped to the scene node containing the calling component.

```ts
const origin = useOrigin();

await origin.perform(forward(originView(SettingsView), fade));
```

Return value:

| Field             | Description                                         |
| ----------------- | --------------------------------------------------- |
| `nodeKey`         | Unique key of this mounted node                     |
| `scene`           | Containing `OriginScene`                            |
| `context`         | Reactive node-local `OriginContext`                 |
| `view`            | Reactive shorthand for the current recipe           |
| `previous`        | Recipe belonging to the retained previous instance  |
| `canGoBack`       | Whether a retained previous instance exists         |
| `begin(action)`   | Create a target and return manual operation control |
| `perform(action)` | Create and programmatically commit a target         |

The composable throws when called outside a view mounted by `OriginScene`.
There is no global `activeView`; the injected node containing the event is the
origin.

## Scene diagnostics and manual operations

### `OriginScene` fields

| Field        | Type                                      | Description                           |
| ------------ | ----------------------------------------- | ------------------------------------- |
| `nodes`      | `ComputedRef<readonly OriginSceneNode[]>` | Currently mounted Vue component nodes |
| `operations` | `ComputedRef<readonly OriginOperation[]>` | Live operation edges                  |
| `roots`      | `ShallowRef<readonly string[]>`           | Visible operation-graph roots         |

These fields are suitable for inspectors and diagnostics. Do not mutate their
contents.

### `scene.contextFor(nodeKey)`

Returns the `OriginContext` for a mounted node. Throws if the key no longer
exists.

### `scene.begin(originKey, action)`

For forward or replace, mounts a new target and waits one Vue tick for
measurement. For back, reveals and measures the retained previous node. It
then returns an `OriginOperationHandle`.

```ts
const handle = await scene.begin(nodeKey, action);
handle.update(0.25, 0.4);
const committed = await handle.finish();
```

Only one outgoing operation may exist for a given origin. Its created target
can immediately begin its own outgoing operation, enabling X → Y → Z chains.

### `OriginOperationHandle`

| Member                        | Description                                         |
| ----------------------------- | --------------------------------------------------- |
| `id`                          | Unique operation ID                                 |
| `originKey`                   | Source node key                                     |
| `targetKey`                   | Created or retained target node key                 |
| `update(progress, velocity?)` | Update normalized interactive state                 |
| `finish(options?)`            | Decide, settle, and return whether target committed |
| `cancel(options?)`            | Force cancellation and remove the target branch     |

`OriginFinishOptions`:

| Field     | Default            | Description                  |
| --------- | ------------------ | ---------------------------- |
| `commit`  | threshold decision | Force commit or cancellation |
| `animate` | `true`             | Run the settling spring      |

### `scene.perform(originKey, action)`

Equivalent to beginning an operation and immediately finishing it with
`commit: true`. The target still uses the settling spring unless reduced motion
is active.

### Renderer integration methods

`registerElement()`, `registerContainer()`, `styleForNode()`, and
`isNodeInteractive()` are public at the TypeScript boundary because the Vue
renderer components consume them. They are internal integration APIs and may
change during the experimental series.

## Type reference

### `OriginView<Props>`

A component recipe containing `component`, optional `props`, optional `key`,
and optional diagnostic `name`.

### `OriginAction`

A choreography, placement, history mode, and—except for back—target recipe.

### `OriginNavigationIntent`

An animation-free target, placement, and history mutation returned by
`forward()`, `replace()`, `back()`, `above()`, or `under()` when choreography
is omitted. Gesture `.animate()` combines it with choreography to create the
internal action.

### Gesture definition types

- `OriginGestureDefinition`: immutable executable result passed to
  `useOriginGesture()` or the `OriginGesture` component.
- `OriginGestureStart`: anywhere, edge, or predicate start policy.
- `OriginGestureDistance`: numeric CSS pixels or a CSS length string.
- `OriginGestureStartContext`: pointer-down event, origin, host, bounds, and
  local/client point.
- `OriginGestureCompletionContext`: release metrics and origin/DOM context.
- `OriginGestureDirectionOptions`: `threshold` and `axisDominance`.
- `OriginGestureBinding`: host style and four pointer handlers.
- `OriginGestureSurfaceProps`: shared host tag and completed definition list.
- `MaybeOriginNavigationIntent`: synchronous or asynchronous nullable
  navigation-factory result.

### `OriginContext`

Node-local action context:

- `nodeKey`: mounted origin identity.
- `view`: origin recipe.
- `canGoBack`: whether a retained previous instance exists.
- `previous`: recipe belonging to the mounted previous entry.
- `history`: recipes belonging to all retained previous entries.

### `MaybeOriginAction`

```ts
OriginAction | null | undefined | Promise<OriginAction | null | undefined>;
```

### `OriginEffect`

| Field       | Description                                     |
| ----------- | ----------------------------------------------- |
| `transform` | Composable CSS transform contribution           |
| `opacity`   | Multiplicative opacity contribution             |
| `layer`     | Relative stacking contribution                  |
| `style`     | Other CSS properties with local-last precedence |

`above()` adds a default target layer of `+1`; `under()` adds `-1`.

### `OriginChoreographyContext`

| Field        | Description                                            |
| ------------ | ------------------------------------------------------ |
| `progress`   | Normalized `0..1` progress                             |
| `velocity`   | Normalized progress units per second                   |
| `phase`      | `preparing`, `interactive`, `settling`, or `finished`  |
| `intent`     | `undecided`, `commit`, or `cancel`                     |
| `originRect` | Origin bounds captured before target mounting          |
| `targetRect` | Target bounds measured after mounting                  |
| `viewport`   | Scene-container bounds, with browser viewport fallback |

Rect values are viewport CSS pixels.

### Diagnostic types

- `OriginSceneNode`: mounted identity, retained previous key, state, recipe,
  history, and incoming edge.
- `OriginSceneNodeState`: `active`, `transitioning`, `exposed`, or `parked`.
- `OriginOperation`: read-only live edge state.
- `OriginOperationPhase`: operation lifecycle phase.
- `OriginOperationIntent`: selected operation outcome.
- `OriginRect`: top, left, width, and height.

### Internal types

`OriginNodeScope` and `MutableOriginOperation` are renderer/runtime
implementation types. They are exported by the current barrel but marked
`@internal` and should not be application dependencies.

## Errors and constraints

- `useOrigin()` and `useOriginGesture()` must run inside a component mounted by
  `OriginScene`.
- An origin can own only one outgoing operation at a time.
- Parked or exposed retained entries are inert and cannot originate operations.
  The active connected target owns interactions until back reveals its source.
- A target can originate its own operation as soon as its incoming operation's
  intent becomes commit.
- The included recognizer follows one primary pointer and one axis.
- Builder edges accept CSS lengths; arbitrary start policy belongs in
  `.from.when()`.
- Every pushed history entry retains its Vue instance and DOM until a committed
  back operation pops it. There is no eviction policy yet.
- Parked instances remain mounted, so their ordinary Vue effects and timers
  continue running.
- A choreography creates one target. Chaining supports any number of
  simultaneously mounted targets.
- Reduced-motion preference resolves settling immediately.