feat(macroplan): vendor plan model and grid from the macroplan app

Copied verbatim (imports resorted) from jclab/macroplan so future
upstream syncs stay copy-paste; extraction to a shared package is
deferred until drift hurts.

src/modules/macroplan/model/parse.ts

@@ -0,0 +1,153 @@
+import { parse as parseToml } from "smol-toml"
+import * as v from "valibot"
+
+import type { RawPlan, StatusLevel } from "./types"
+import { toYmd } from "./week"
+
+/** Thrown for any malformed source — message is safe to show the author. */
+export class PlanParseError extends Error {
+  constructor(message: string) {
+    super(message)
+    this.name = "PlanParseError"
+  }
+}
+
+const STATUSES = ["on-track", "at-risk", "off-track"] as const satisfies readonly StatusLevel[]
+
+// ── Field schemas ──────────────────────────────────────────────────────────
+// A TOML date (smol-toml returns a Date subclass) or a yyyy-mm-dd string,
+// normalized to yyyy-mm-dd via `toYmd`.
+const Ymd = v.pipe(
+  v.union([v.date(), v.string()], "must be a date (e.g. 2026-06-01)"),
+  v.transform((value: string | Date) => toYmd(value)),
+)
+
+const Status = v.picklist(STATUSES, `must be one of ${STATUSES.join(", ")}`)
+
+const Name = v.pipe(v.string("is required"), v.nonEmpty("is required"))
+
+const FeatureSchema = v.object({
+  name: Name,
+  start: Ymd,
+  original: Ymd,
+  reestimates: v.optional(v.array(Ymd, "must be a list of dates"), []),
+  delivered: v.optional(Ymd),
+  learning: v.optional(v.string()),
+  status: v.optional(Status),
+  note: v.optional(v.string()),
+})
+
+const MilestoneSchema = v.object({
+  name: Name,
+  week: Ymd,
+  requires: v.optional(
+    v.array(v.string("must be a feature name"), "must be a list of feature names"),
+    [],
+  ),
+})
+
+/** The Macroplan format version this build understands (see docs/format.md).
+ *  Files may declare `macroplan_version`; a newer version is rejected rather
+ *  than silently mis-rendered against a schema we don't know. */
+export const FORMAT_VERSION = 1
+
+/** Parse + validate a Macroplan TOML source into the raw model. */
+export function parseMacroplan(source: string): RawPlan {
+  let data: Record<string, unknown>
+  try {
+    data = parseToml(source) as Record<string, unknown>
+  } catch (e) {
+    throw new PlanParseError(e instanceof Error ? e.message : String(e))
+  }
+
+  checkVersion(data.macroplan_version)
+
+  const features = asBlocks(data.feature, "feature").map((f, i) =>
+    check(FeatureSchema, f, blockWhere("feature", f, i)),
+  )
+  requireUniqueFeatureNames(features)
+
+  return {
+    title: data.title != null ? String(data.title) : "Untitled Macroplan",
+    start: data.start != null ? check(Ymd, data.start, "plan", "start") : undefined,
+    end: data.end != null ? check(Ymd, data.end, "plan", "end") : undefined,
+    features,
+    milestones: asBlocks(data.milestone, "milestone").map((m, i) =>
+      check(MilestoneSchema, m, blockWhere("milestone", m, i)),
+    ),
+  }
+}
+
+/** Validate the optional `macroplan_version` marker. Absent means the current
+ *  version; a future version we don't understand is rejected rather than
+ *  silently mis-rendered. */
+function checkVersion(value: unknown): void {
+  if (value == null) return
+  if (typeof value !== "number" || !Number.isInteger(value) || value < 1) {
+    throw new PlanParseError("`macroplan_version` must be a positive integer")
+  }
+  if (value > FORMAT_VERSION) {
+    throw new PlanParseError(
+      `unsupported macroplan_version ${value} — this build understands up to ${FORMAT_VERSION}`,
+    )
+  }
+}
+
+/** Feature names are the join key for a Milestone's `requires`, so they must be
+ *  unique — otherwise a requirement resolves ambiguously to the first match. */
+function requireUniqueFeatureNames(features: readonly { name: string }[]): void {
+  const seen = new Set<string>()
+  for (const f of features) {
+    if (seen.has(f.name)) {
+      throw new PlanParseError(`duplicate feature name "${f.name}" — feature names must be unique`)
+    }
+    seen.add(f.name)
+  }
+}
+
+function asBlocks(value: unknown, key: string): unknown[] {
+  if (value == null) return []
+  if (!Array.isArray(value)) {
+    throw new PlanParseError(`\`${key}\` must be written as [[${key}]] blocks`)
+  }
+  return value
+}
+
+/** "feature \"Payments\"" when the block carries a name, else "feature #2". */
+function blockWhere(kind: string, block: unknown, i: number): string {
+  const name =
+    block != null && typeof block === "object" && "name" in block
+      ? (block as { name: unknown }).name
+      : undefined
+  return name != null && name !== "" ? `${kind} "${String(name)}"` : `${kind} #${i + 1}`
+}
+
+/** Validate `value` against `schema`, raising a contextual PlanParseError. */
+function check<S extends v.GenericSchema>(
+  schema: S,
+  value: unknown,
+  where: string,
+  field?: string,
+): v.InferOutput<S> {
+  const result = v.safeParse(schema, value)
+  if (!result.success) {
+    throw new PlanParseError(`${where}: ${friendly(result.issues[0], field)}`)
+  }
+  return result.output
+}
+
+type Issue = {
+  readonly message: string
+  readonly received: string
+  readonly path?: ReadonlyArray<{ readonly key: unknown }>
+}
+
+/** Render an issue against the offending field, e.g. "`start` must be a date"
+ *  — or "missing `original`" when the key is absent (valibot reports its own
+ *  "Invalid key" wording for that, which isn't fit to show the author). */
+function friendly(issue: Issue, fallbackField?: string): string {
+  const key = issue.path?.[0]?.key
+  const field = typeof key === "string" ? key : fallbackField
+  if (issue.received === "undefined") return field ? `missing \`${field}\`` : "missing value"
+  return field ? `\`${field}\` ${issue.message}` : issue.message
+}