feat(model): add domain types and model factory

src/model/factory.ts

@@ -0,0 +1,74 @@
+/**
+ * Pure constructors for Model pieces: id generation, a blank Model, and the
+ * auto-naming that lets F1 place a node with zero dialogs. No store, no Vue —
+ * just data in, data out, so it stays unit-testable.
+ */
+import {
+  type CloudNode,
+  type ConverterNode,
+  type FlowNode,
+  type Model,
+  MODEL_VERSION,
+  type ModelNode,
+  type NodeKind,
+  type Position,
+  type StockNode,
+} from "./types"
+
+/** Short, readable, collision-resistant id. `crypto.randomUUID` is built in. */
+export function newId(prefix: string): string {
+  return `${prefix}-${crypto.randomUUID().slice(0, 8)}`
+}
+
+/** Human label per kind, used for auto-naming. Clouds are unnamed boundaries. */
+const LABEL: Record<Exclude<NodeKind, "cloud">, string> = {
+  stock: "Stock",
+  flow: "Flow",
+  converter: "Converter",
+}
+
+export function emptyModel(name = "Untitled model"): Model {
+  return { version: MODEL_VERSION, id: newId("model"), name, nodes: [], infoLinks: [] }
+}
+
+/**
+ * Next free auto-name for `kind`, e.g. "Stock 3". Picks one past the highest
+ * trailing number already in use so it stays stable across deletes/renames.
+ */
+export function nextName(nodes: ModelNode[], kind: Exclude<NodeKind, "cloud">): string {
+  const label = LABEL[kind]
+  const pattern = new RegExp(`^${label} (\\d+)$`)
+  let max = 0
+  for (const node of nodes) {
+    if (node.kind !== kind || !("name" in node)) continue
+    const match = pattern.exec(node.name)
+    if (match) max = Math.max(max, Number(match[1]))
+  }
+  return `${label} ${max + 1}`
+}
+
+export function makeStock(position: Position, name: string): StockNode {
+  return { id: newId("stock"), kind: "stock", name, position }
+}
+
+export function makeConverter(position: Position, name: string): ConverterNode {
+  return { id: newId("conv"), kind: "converter", name, position }
+}
+
+export function makeFlow(
+  position: Position,
+  name: string,
+  source: string,
+  target: string,
+): FlowNode {
+  return { id: newId("flow"), kind: "flow", name, source, target, position }
+}
+
+export function makeCloud(position: Position): CloudNode {
+  return { id: newId("cloud"), kind: "cloud", position }
+}
+
+/** Midpoint between two positions — where a Flow's valve sits on its pipe. */
+export function midpoint(a: Position, b: Position): Position {
+  return { x: (a.x + b.x) / 2, y: (a.y + b.y) / 2 }
+}