import { Signal } from '@preact/signals-core';

/**
 * Fine-grained signal bindings (KF-294 spike).
 *
 * When a `Signal` is interpolated straight into a JSX attribute
 * (`class={sig}`) or a text child (`{sig}`) INSIDE a `mount()` render, the
 * JSX runtime stops stringifying it. Instead it emits a marker into the HTML
 * string and records a binding here; after the string is parsed to DOM, a
 * wiring pass attaches one `effect` per binding that writes straight to the
 * live node. A later change to that signal then updates the node WITHOUT
 * re-running the render function or walking the list reconciler.
 *
 * This reuses the "marker in string, wire up after parse" mechanism the
 * keyed-list reconciler already uses for `<!--kf-list:{id}-->` markers.
 *
 * TWO SCOPES of binding, with disjoint marker namespaces so their wiring
 * passes never collide:
 *
 *   - GLOBAL holes — signals in the static surrounds (outside any `each()`
 *     row). Markers: `data-kfb` attribute / `<!--kfb:{id}-->` comment. Ids come
 *     from the mount render context's counter; wired by `wireBindings()` over
 *     the whole mount root; disposed/re-wired by `mount()` each render.
 *
 *   - ROW holes — signals inside an `each()` row. Markers: `data-kfbrow`
 *     attribute / `<!--kfbr:{id}-->` comment. Ids are row-LOCAL (reset per row)
 *     so they stay stable and collision-free as rows are inserted/removed/moved.
 *     Captured per row by `captureRowBindings()`, carried on the list segment
 *     item, and wired/disposed by the list reconciler at each row node's
 *     create/remove — so a binding's lifetime tracks its row node's lifetime,
 *     and row reorders (which reuse the same node) are free.
 *
 * Outside a `mount()` render (SSR / `SafeHtml.toString()`) neither scope is
 * active: the runtime snapshots `signal.value` and emits no markers, so server
 * output is correct and legacy `.toString()` callers are unaffected.
 *
 * Module-level mutable state note: `context` / `rowSink` (plus `rowCounter`,
 * the row-hole id counter that resets with each row capture) are a third
 * sanctioned module-level mutable location (alongside `store.ts:REGISTRY` and
 * `each.ts:context`). They hold the current render's binding sinks and are set
 * / cleared by `mount()` and `each()` around the render calls. The only other
 * module-level container here is `insertedTextNodes`, a WeakMap keyed on text
 * marker comments — a pure cache whose entries die with their nodes (GC-tied
 * lifetime), so it carries no cross-render semantics.
 */

interface AttrBinding {
    kind: 'attr';
    id: string;
    attr: string;
    signal: Signal<unknown>;
}
interface TextBinding {
    kind: 'text';
    id: string;
    signal: Signal<unknown>;
}
type Binding = AttrBinding | TextBinding;

export type { Binding as B };