// Importing the graph package index is what registers the built-in nodes.
import {
  ANNOTATION_KINDS,
  annotationList,
  createEmptyGraph,
  type DeclaredPort,
  type GraphAnnotation,
  MIN_ANNOTATION_SIZE,
  type DeclaredPortKind,
  type Graph,
  type GraphEdge,
  type GraphNode,
  isValidPortName,
  fixedPortKeys,
  type NodeDef,
  nodeDef,
  STATE,
} from '../graph';
import { isParticleNodeDef } from '../particles/nodes';
import { isShaderNodeDef } from '../shader/nodes';
import { isKeyInterpolation, normalizeKeys } from '../model/animation';
import type {
  AnimationKey,
  AnimationTrack,
  Asset,
  StateMachineAsset,
  TextureFrame,
  TilemapLayer,
} from '../model/Asset';
import { parseCellKey } from '../model/tilemap';
import { pluginsOf } from './projectPlugins';
import { decodeCells, encodeCells } from './tilemapCells';
import { isAssetType } from '../model/AssetTypes';
import { isFontFile } from '../model/font';
import { isSoundFile } from '../model/sound';
import { emptyEdit, type InstanceEdit, isEmptyEdit } from '../model/instance';
import {
  type FieldValue,
  type PropertyBag,
  type PropertyValue,
  type StructValue,
  tagOf,
  type Vec2,
} from '../model/Properties';
import { PROJECT_FORMAT_VERSION, type Project } from '../model/Project';
import { readScope } from '../model/Scope';
import type { SceneObject } from '../model/SceneObject';
import {
  DEFAULT_FILL,
  isTextureFile,
  normalizeBorders,
  normalizeFrameRect,
  setFrameCollision,
  setFrameSlice,
} from '../model/texture';
import { pointsOf } from '../model/polygon';
import { hasParentCycle } from '../model/walk';
import {
  DECLARED_PORT_KINDS,
  FIELD_KINDS,
  type FieldKind,
  isTaggedKind,
  VARIABLE_KINDS,
  type VariableKind,
} from '../properties/kinds';
import { type FlatItem, makeFlatItem } from '../properties/listItems';
import {
  coerceValue,
  isValidFieldName,
  isValidVariableName,
  type PropertyDef,
  type PropertySchema,
  rowsNotClaimedBy,
  schemaFor,
  type StructFieldDef,
  variableDef,
} from '../properties/PropertySchema';
import { particleParamDefs } from '../properties/particles';
import { SHADER_KEY, shaderParamDefs } from '../properties/shaders';

/**
 * Turns untrusted JSON (server file, import) into a well-formed Project: unknown keys are dropped,
 * missing ones get defaults, values are coerced against the schema, dangling objects are removed.
 */
export function deserializeProject(raw: unknown, fallbackId = ''): Project {
  const r = asRecord(raw);
  const rawAssets = (Array.isArray(r.assets) ? r.assets : []).map(asRecord);

  // Pass 1: asset ids and their effective schemas, needed to coerce overrides in pass 2.
  const schemas = new Map<string, PropertySchema>();
  const variables = new Map<string, PropertyDef[]>();
  const rawProps = new Map<string, Record<string, unknown>>();
  const shaderGraphs = new Map<string, Graph>();
  const shaderRows = new Map<string, PropertyDef[]>();
  const particleGraphs = new Map<string, Graph>();
  const wearers = new Map<string, 'sprite' | 'particles'>();
  for (const a of rawAssets) {
    if (typeof a.id !== 'string' || !a.id || !isAssetType(a.type)) continue;
    rawProps.set(a.id, asRecord(a.props));
    if (a.type === 'sprite' || a.type === 'particles') wearers.set(a.id, a.type);
    if (a.type === 'behavior' || a.type === 'variables') {
      const vars = normalizeVariables(a.variables);
      variables.set(a.id, vars);
      // The full schema, not just the common rows: this is what pass 2 coerces `props` against, and
      // a behavior's own `runInEditor` would be dropped as undeclared.
      schemas.set(a.id, [...schemaFor(a.type), ...vars]);
    } else if (a.type === 'particles') {
      // A source's rows end with its own graph's parameters, so the graph is needed before the
      // overrides of the objects placed from it can be coerced.
      const graph = normalizeGraph(a.graph, isParticleNodeDef);
      particleGraphs.set(a.id, graph);
      schemas.set(a.id, [...schemaFor('particles'), ...particleParamDefs(graph)]);
    } else {
      if (a.type === 'shader') {
        const graph = normalizeGraph(a.graph, isShaderNodeDef);
        shaderGraphs.set(a.id, graph);
        shaderRows.set(a.id, shaderParamDefs(graph));
      }
      schemas.set(a.id, schemaFor(a.type));
    }
  }
  /**
   * A sprite's or source's rows end with the parameters of the shader its bag names – an override's,
   * else the asset's. A source already carries its own graph's rows, so a name it has stays its own.
   */
  const schemaOf = (assetId: string, bag: Record<string, unknown>): PropertySchema | undefined => {
    const schema = schemas.get(assetId);
    const wearer = wearers.get(assetId);
    if (!schema || !wearer) return schema;
    const own = bag[SHADER_KEY];
    const shader = typeof own === 'string' ? own : rawProps.get(assetId)?.[SHADER_KEY];
    const rows = shaderRows.get(typeof shader === 'string' ? shader : '') ?? [];
    return [...schema, ...(wearer === 'particles' ? rowsNotClaimedBy(rows, schema) : rows)];
  };

  // Pass 2: build assets. Frame ids share the reference space with asset ids, so `normalizeTexture`
  // is handed the ids already spoken for.
  const assets: Asset[] = [];
  const takenIds = new Set(schemas.keys());
  for (const a of rawAssets) {
    const id = typeof a.id === 'string' ? a.id : '';
    const schema = schemaOf(id, asRecord(a.props));
    if (!schema || !isAssetType(a.type)) continue;
    const type = a.type;
    const name = typeof a.name === 'string' ? a.name : type;
    const props = normalizeBag(a.props, schema, false);
    if (type === 'scene' || type === 'container') {
      assets.push({ id, type, name, props, objects: normalizeObjects(a.objects, schemaOf) });
    } else if (type === 'behavior') {
      assets.push({
        id,
        type,
        name,
        props,
        variables: variables.get(id) ?? [],
        graph: normalizeGraph(a.graph),
      });
    } else if (type === 'variables') {
      assets.push({ id, type, name, props, variables: variables.get(id) ?? [] });
    } else if (type === 'statemachine') {
      const machine: StateMachineAsset = {
        id,
        type,
        name,
        props,
        graph: normalizeGraph(a.graph, (def) => def.type === STATE),
      };
      if (readScope(a.scope) === 'global') machine.scope = 'global';
      // Kept as written even where it names no state any more: the same as a deleted start.
      if (typeof a.start === 'string' && a.start !== '') machine.start = a.start;
      assets.push(machine);
    } else if (type === 'shader') {
      assets.push({ id, type, name, props, graph: shaderGraphs.get(id) ?? createEmptyGraph() });
    } else if (type === 'particles') {
      assets.push({ id, type, name, props, graph: particleGraphs.get(id) ?? createEmptyGraph() });
    } else if (type === 'texture') {
      assets.push({ id, type, name, props, ...normalizeTexture(a, takenIds) });
    } else if (type === 'font') {
      const file = typeof a.file === 'string' && isFontFile(a.file) ? a.file : '';
      assets.push({ id, type, name, props, file });
    } else if (type === 'sound') {
      const file = typeof a.file === 'string' && isSoundFile(a.file) ? a.file : '';
      assets.push({ id, type, name, props, file });
    } else if (type === 'tile') {
      // A picture naming nothing is kept, like an animation's dangling root: it reads as missing
      // in the tab and comes back when the texture it named is restored by an undo.
      const pictures = (Array.isArray(a.pictures) ? a.pictures : []).filter(
        (id): id is string => typeof id === 'string' && id !== '',
      );
      assets.push({ id, type, name, props, pictures });
    } else if (type === 'tilemap') {
      assets.push({ id, type, name, props, layers: normalizeLayers(a.layers) });
    } else if (type === 'animation') {
      // A root or row aiming at something gone is kept: it reads as missing and keeps its keys.
      const root = typeof a.root === 'string' ? a.root : '';
      assets.push({ id, type, name, props, root, tracks: normalizeTracks(a.tracks) });
    } else {
      assets.push({ id, type, name, props });
    }
  }

  let activeSceneId = typeof r.activeSceneId === 'string' ? r.activeSceneId : '';
  if (!assets.some((a) => a.type === 'scene' && a.id === activeSceneId)) {
    const first = assets.find((a) => a.type === 'scene');
    activeSceneId = first ? first.id : '';
  }

  // A dangling start scene reads as none at all – the run then falls back to the active scene,
  // which is also what every project written before there was such a field does.
  const startSceneId =
    typeof r.startSceneId === 'string' && assets.some((a) => a.type === 'scene' && a.id === r.startSceneId)
      ? r.startSceneId
      : '';

  const project: Project = {
    formatVersion: PROJECT_FORMAT_VERSION,
    id: typeof r.id === 'string' && r.id ? r.id : fallbackId,
    name: typeof r.name === 'string' ? r.name : 'Untitled',
    assets,
    activeSceneId,
    startSceneId,
    // The same reading the editor did before it loaded the plugins (#119), so the model says what
    // is actually running.
    plugins: pluginsOf(r),
  };
  return project;
}

/**
 * Plain JSON-ready copy of the project (deep clone, stable key order for readable diffs). The cells
 * of a tilemap are the one thing written differently from how they are held: see `tilemapCells.ts`.
 */
export function serializeProject(project: Project): unknown {
  const copy = JSON.parse(JSON.stringify(project)) as Project;
  for (const asset of copy.assets)
    if (asset.type === 'tilemap')
      (asset as { layers: unknown[] }).layers = asset.layers.map(({ cells, ...layer }) => ({
        ...layer,
        ...encodeCells(cells),
      }));
  return copy;
}

function normalizeObjects(
  raw: unknown,
  schemaOf: (assetId: string, overrides: Record<string, unknown>) => PropertySchema | undefined,
): SceneObject[] {
  const objects: SceneObject[] = [];
  for (const item of Array.isArray(raw) ? raw : []) {
    const o = asRecord(item);
    if (typeof o.id !== 'string' || !o.id || typeof o.assetId !== 'string') continue;
    const schema = schemaOf(o.assetId, asRecord(o.overrides));
    if (!schema || schema === schemaFor('scene')) continue; // dangling reference or illegal scene-in-scene
    const p = asRecord(o.position);
    const offset = asRecord(o.editorOffset);
    objects.push({
      id: o.id,
      assetId: o.assetId,
      name: typeof o.name === 'string' ? o.name : '',
      position: { x: toNumber(p.x), y: toNumber(p.y), z: toNumber(p.z) },
      editorOffset: { x: toNumber(offset.x), y: toNumber(offset.y) },
      overrides: normalizeBag(o.overrides, schema, true),
      parentId: typeof o.parentId === 'string' ? o.parentId : '',
      instanceEdits: normalizeInstanceEdits(o.instanceEdits),
    });
  }
  // Parents must exist in the same scene, differ from the object itself and not form cycles.
  const byId = new Map(objects.map((o) => [o.id, o]));
  for (const o of objects) if (o.parentId && (o.parentId === o.id || !byId.has(o.parentId))) o.parentId = '';
  // Cut one link per cycle: an object already unlinked here is a root for the objects checked after it.
  const parentOf = (o: SceneObject) => (o.parentId ? byId.get(o.parentId) : undefined);
  for (const o of objects) if (hasParentCycle(o, parentOf)) o.parentId = '';
  return objects;
}

/**
 * Deviations of container content, keyed by template path. Values are not coerced against a schema:
 * which asset a path leads to depends on container assets that may not be built yet, and resolving
 * drops what the schema does not declare anyway.
 */
function normalizeInstanceEdits(raw: unknown): Record<string, InstanceEdit> {
  const edits: Record<string, InstanceEdit> = {};
  for (const [path, value] of Object.entries(asRecord(raw))) {
    if (!path) continue;
    const e = asRecord(value);
    const edit = emptyEdit();
    if (typeof e.name === 'string') edit.name = e.name;
    const position = asRecord(e.position);
    for (const axis of ['x', 'y', 'z'] as const)
      if (typeof position[axis] === 'number' && Number.isFinite(position[axis]))
        edit.position[axis] = position[axis];
    const offset = asRecord(e.editorOffset);
    if (typeof offset.x === 'number' || typeof offset.y === 'number')
      edit.editorOffset = { x: toNumber(offset.x), y: toNumber(offset.y) };
    for (const [key, v] of Object.entries(asRecord(e.overrides))) {
      const value = asStoredValue(v);
      if (value !== undefined) edit.overrides[key] = value;
    }
    if (!isEmptyEdit(edit)) edits[path] = edit;
  }
  return edits;
}

function normalizeVariables(raw: unknown): PropertyDef[] {
  const defs: PropertyDef[] = [];
  const seen = new Set<string>();
  for (const item of Array.isArray(raw) ? raw : []) {
    const v = asRecord(item);
    const key = typeof v.key === 'string' ? v.key : '';
    const kind = (VARIABLE_KINDS as readonly string[]).includes(String(v.kind))
      ? (v.kind as VariableKind)
      : 'number';
    // Common property keys are reserved – a variable of that name would shadow the switch.
    if (!isValidVariableName(key) || seen.has(key)) continue;
    seen.add(key);
    const fields = normalizeStructFields(v.fields);
    const def = variableDef(key, kind, undefined, fields);
    def.default = coerceValue(def, (v.default ?? def.default) as PropertyValue);
    defs.push(def);
  }
  return defs;
}

/** An unreadable field is dropped rather than defaulted: an invented key would claim a value. */
function normalizeStructFields(raw: unknown): StructFieldDef[] {
  const fields: StructFieldDef[] = [];
  const seen = new Set<string>();
  for (const item of Array.isArray(raw) ? raw : []) {
    const f = asRecord(item);
    const key = typeof f.key === 'string' ? f.key : '';
    if (!isValidFieldName(key) || seen.has(key)) continue;
    const field = readField(key, f);
    if (!field) continue;
    seen.add(key);
    fields.push(field);
  }
  return fields;
}

function readField(key: string, f: Record<string, unknown>): StructFieldDef | null {
  const isFieldKind = (value: unknown) => (FIELD_KINDS as readonly string[]).includes(String(value));
  if (f.kind === 'list') return { key, kind: 'list' };
  return isFieldKind(f.kind) ? { key, kind: f.kind as FieldKind } : null;
}

function normalizePorts(raw: unknown, fixed: readonly string[], writable: boolean): DeclaredPort[] {
  const ports: DeclaredPort[] = [];
  const seen = new Set(fixed);
  for (const item of Array.isArray(raw) ? raw : []) {
    const p = asRecord(item);
    const key = typeof p.key === 'string' ? p.key : '';
    if (!isValidPortName(key) || seen.has(key)) continue;
    seen.add(key);
    const kind = (DECLARED_PORT_KINDS as readonly string[]).includes(String(p.kind))
      ? (p.kind as DeclaredPortKind)
      : 'number';
    ports.push(writable && p.write === true ? { key, kind, write: true } : { key, kind });
  }
  return ports;
}

/** `keep` restricts the node types kept: a state machine's graph holds states, a shader's shader nodes, and nothing else. */
function normalizeGraph(raw: unknown, keep?: (def: NodeDef) => boolean): Graph {
  const g = asRecord(raw);
  const graph = createEmptyGraph();
  const nodeIds = new Set<string>();
  for (const item of Array.isArray(g.nodes) ? g.nodes : []) {
    const n = asRecord(item);
    const id = typeof n.id === 'string' ? n.id : '';
    const type = typeof n.type === 'string' ? n.type : '';
    const def = nodeDef(type);
    if (!id || nodeIds.has(id) || !def || (keep !== undefined && !keep(def))) continue;
    nodeIds.add(id);
    // Params carry both settings and inline input values, so there is no schema to coerce against.
    const params: PropertyBag = {};
    for (const [key, value] of Object.entries(asRecord(n.params))) {
      const stored = asStoredValue(value);
      if (stored !== undefined) params[key] = stored;
    }
    const node: GraphNode = { id, type, x: toNumber(n.x), y: toNumber(n.y), params };
    const ports = normalizePorts(n.ports, fixedPortKeys(def), def.declaresPorts === 'both');
    if (ports.length > 0) node.ports = ports;
    if (n.collapsed === true) node.collapsed = true;
    graph.nodes.push(node);
  }
  const edgeIds = new Set<string>();
  for (const item of Array.isArray(g.edges) ? g.edges : []) {
    const e = asRecord(item);
    const from = asRecord(e.from);
    const to = asRecord(e.to);
    const id = typeof e.id === 'string' ? e.id : '';
    if (!id || edgeIds.has(id)) continue;
    if (
      typeof from.node !== 'string' ||
      typeof from.port !== 'string' ||
      typeof to.node !== 'string' ||
      typeof to.port !== 'string'
    )
      continue;
    if (!nodeIds.has(from.node) || !nodeIds.has(to.node)) continue;
    edgeIds.add(id);
    const edge: GraphEdge = {
      id,
      from: { node: from.node, port: from.port },
      to: { node: to.node, port: to.port },
    };
    if (e.folded === true) edge.folded = true;
    const label = typeof e.label === 'string' ? e.label.trim() : '';
    if (label) edge.label = label;
    graph.edges.push(edge);
  }
  for (const kind of ANNOTATION_KINDS) {
    const list = normalizeAnnotations(g[kind === 'group' ? 'groups' : 'notes'], nodeIds);
    if (list.length > 0) annotationList(graph, kind).push(...list);
  }
  return graph;
}

/**
 * Annotations share the id space with nodes and with each other: a duplicate would make one
 * selection mean two boxes. A size below the minimum is raised rather than dropped – a box nobody
 * can see is worse than one that is a little larger than it was written.
 */
function normalizeAnnotations(raw: unknown, takenIds: Set<string>): GraphAnnotation[] {
  const list: GraphAnnotation[] = [];
  for (const item of Array.isArray(raw) ? raw : []) {
    const a = asRecord(item);
    const id = typeof a.id === 'string' ? a.id : '';
    if (!id || takenIds.has(id)) continue;
    takenIds.add(id);
    const annotation: GraphAnnotation = {
      id,
      x: toNumber(a.x),
      y: toNumber(a.y),
      w: Math.max(toNumber(a.w), MIN_ANNOTATION_SIZE.w),
      h: Math.max(toNumber(a.h), MIN_ANNOTATION_SIZE.h),
      text: typeof a.text === 'string' ? a.text : '',
    };
    if (typeof a.color === 'number' && Number.isFinite(a.color))
      annotation.color = Math.max(0, Math.min(0xffffff, Math.floor(a.color)));
    list.push(annotation);
  }
  return list;
}

/**
 * A file name that is not the server's content-addressed form is dropped: a request built from it
 * would 404, and the texture then loads as "no picture".
 */
function normalizeTexture(
  raw: Record<string, unknown>,
  takenIds: Set<string>,
): { file: string; width: number; height: number; frames: TextureFrame[] } {
  const file = typeof raw.file === 'string' && isTextureFile(raw.file) ? raw.file : '';
  const size = (value: unknown): number =>
    typeof value === 'number' && Number.isFinite(value) && value > 0 ? Math.floor(value) : 0;
  const width = size(raw.width);
  const height = size(raw.height);
  const frames: TextureFrame[] = [];
  for (const item of Array.isArray(raw.frames) ? raw.frames : []) {
    const f = asRecord(item);
    const id = typeof f.id === 'string' ? f.id : '';
    // Frame ids share the reference space with asset ids, so a duplicate would make one
    // reference mean two pictures.
    if (!id || takenIds.has(id)) continue;
    takenIds.add(id);
    const rect = normalizeFrameRect(
      { x: toNumber(f.x), y: toNumber(f.y), w: toNumber(f.w), h: toNumber(f.h) },
      width,
      height,
    );
    const frame: TextureFrame = { id, name: typeof f.name === 'string' ? f.name : '', ...rect };
    // Against the frame, not the image: the borders are distances inside the cut-out. A frame
    // without them is one nobody sliced, and keeps saying so.
    const border = asRecord(f.border);
    setFrameSlice(frame, {
      border: normalizeBorders(
        {
          left: toNumber(border.left),
          top: toNumber(border.top),
          right: toNumber(border.right),
          bottom: toNumber(border.bottom),
        },
        rect.w,
        rect.h,
      ),
      fill: f.fill === 'stretch' ? 'stretch' : DEFAULT_FILL,
    });
    // Corners that are no numbers fall away; what is left is kept only as an outline (#141).
    const outlines = collisionOutlines(f.collision).filter((outline) => outline.length >= 3);
    if (outlines.length > 0) setFrameCollision(frame, outlines);
    frames.push(frame);
  }
  return { file, width, height, frames };
}

/**
 * A frame's stored outlines: a list of corner lists, or – as saved before a frame held several –
 * one corner list, which is one outline.
 */
function collisionOutlines(raw: unknown): Vec2[][] {
  if (!Array.isArray(raw)) return [];
  if (raw.some((item) => !Array.isArray(item))) return [pointsOf(raw as PropertyValue)];
  return raw.map((outline) => pointsOf(outline as PropertyValue));
}

/**
 * The rows of an animation. Keys hold flat values only – a row animates one property – and are
 * sorted onto whole frames; a second row on the same target and property, or with an id already
 * taken, is dropped like a doubled node.
 */
function normalizeTracks(raw: unknown): AnimationTrack[] {
  const tracks: AnimationTrack[] = [];
  for (const item of Array.isArray(raw) ? raw : []) {
    const t = asRecord(item);
    if (typeof t.id !== 'string' || !t.id || typeof t.property !== 'string' || !t.property) continue;
    const target = typeof t.target === 'string' ? t.target : '';
    if (tracks.some((o) => o.id === t.id || (o.target === target && o.property === t.property))) continue;
    const keys: AnimationKey[] = [];
    for (const k of Array.isArray(t.keys) ? t.keys : []) {
      const key = asRecord(k);
      const frame = Number(key.frame);
      if (!Number.isFinite(frame) || !isPrimitive(key.value)) continue;
      const kept: AnimationKey = { frame, value: key.value };
      // `linear` is what no field means, so it is not kept; an unknown one reads as linear, too.
      if (isKeyInterpolation(key.interpolation) && key.interpolation !== 'linear')
        kept.interpolation = key.interpolation;
      keys.push(kept);
    }
    const track: AnimationTrack = { id: t.id, target, property: t.property, keys: normalizeKeys(keys) };
    if (t.relative === true) track.relative = true;
    tracks.push(track);
  }
  return tracks;
}

/**
 * The layers of a tilemap. A cell whose key is not a pair of whole numbers, or which names nothing,
 * is dropped; one naming a deleted tile is kept, like an animation's dangling row, so an undo
 * brings the drawing back. A doubled layer id is dropped as a doubled node is.
 */
function normalizeLayers(raw: unknown): TilemapLayer[] {
  const layers: TilemapLayer[] = [];
  for (const item of Array.isArray(raw) ? raw : []) {
    const l = asRecord(item);
    if (typeof l.id !== 'string' || !l.id || layers.some((o) => o.id === l.id)) continue;
    const stored = decodeCells(l);
    const cells: Record<string, string> = {};
    for (const [key, value] of Object.entries(stored))
      if (parseCellKey(key) && typeof value === 'string' && value !== '') cells[key] = value;
    const layer: TilemapLayer = { id: l.id, name: typeof l.name === 'string' ? l.name : 'Layer', cells };
    if (l.hidden === true) layer.hidden = true;
    if (typeof l.z === 'number' && Number.isFinite(l.z) && l.z !== 0) layer.z = l.z;
    layers.push(layer);
  }
  return layers;
}

function normalizeBag(raw: unknown, schema: PropertySchema, sparse: boolean): PropertyBag {
  const r = asRecord(raw);
  const bag: PropertyBag = {};
  for (const def of schema) {
    const value = r[def.key];
    if (value === undefined || value === null) {
      if (!sparse) bag[def.key] = def.default;
      continue;
    }
    bag[def.key] = coerceValue(def, value as PropertyValue);
  }
  return bag;
}

function asRecord(value: unknown): Record<string, unknown> {
  return value && typeof value === 'object' ? (value as Record<string, unknown>) : {};
}

/**
 * A value from an untyped slot (node params, instance edits). Lists and structs are kept but
 * flattened one level, so nothing deeper than the model allows can enter behind the type's back.
 */
function asStoredValue(value: unknown): PropertyValue | undefined {
  if (isPrimitive(value)) return value;
  if (Array.isArray(value)) return value.map(asStoredItem).filter((item) => item !== undefined);
  return asStoredStruct(value, asStoredField);
}

const isPrimitive = (value: unknown): value is number | string | boolean =>
  typeof value === 'number' || typeof value === 'string' || typeof value === 'boolean';

/** A primitive, or the one object a flat position may hold: a tagged item. */
const asFlatItem = (value: unknown): FlatItem | undefined => {
  if (isPrimitive(value)) return value;
  const tag = tagOf(value);
  return tag !== undefined && isTaggedKind(tag) ? makeFlatItem(tag, value as PropertyValue) : undefined;
};

/** A list item: a flat one, or a struct of flat ones. */
const asStoredItem = (value: unknown): number | string | boolean | StructValue | undefined =>
  asFlatItem(value) ?? asStoredStruct(value, asFlatItem);

/** A struct field: a flat item or a flat list. A field that is itself a struct is dropped. */
const asStoredField = (value: unknown): FieldValue | undefined =>
  Array.isArray(value) ? value.map(asFlatItem).filter((item) => item !== undefined) : asFlatItem(value);

function asStoredStruct(
  value: unknown,
  ofField: (item: unknown) => FieldValue | undefined,
): StructValue | undefined {
  if (!value || typeof value !== 'object' || Array.isArray(value)) return undefined;
  const fields: Record<string, FieldValue> = {};
  for (const [key, item] of Object.entries(value)) {
    const stored = ofField(item);
    if (stored !== undefined) fields[key] = stored;
  }
  return fields;
}

function toNumber(value: unknown): number {
  const n = Number(value);
  return Number.isFinite(n) ? n : 0;
}