feuerwerk/tests/core/graph.test.ts

import { describe, expect, it } from 'vitest';
import { requireNodeDef } from '../../src/core/commands/require';
import { CommandError } from '../../src/core/commands/Command';
import {
  AddNodeCommand,
  DisconnectCommand,
  RemoveNodeCommand,
  SetNodeParamCommand,
} from '../../src/core/commands/graphCommands';
import {
  AddVariableCommand,
  RemoveVariableCommand,
  RenameVariableCommand,
} from '../../src/core/commands/variableCommands';
import {
  GraphInterpreter,
  allNodeDefs,
  defAcceptsFrom,
  dropTargetPort,
  findNode,
  firstPortFor,
  NO_LOOKUP,
  type PortType,
  portsCompatible,
} from '../../src/core/graph';
import type { BehaviorAsset } from '../../src/core/model/Asset';
import { findAsset } from '../../src/core/model/Project';
import { deserializeProject, serializeProject } from '../../src/core/store/serialize';
import {
  type ProjectFixture,
  fakeContext,
  fakeEntity,
  graphEditor,
  makeBehavior,
  makeProject,
  makeSpriteScene,
  place,
  roundTrip,
} from '../helpers';

/** Adds "On key held(ArrowRight) → Move(owner, dx = speed × dt)" to a project, built through commands like the editor would. */
function withMover<F extends ProjectFixture>(fixture: F) {
  const behavior = makeBehavior(fixture, 'Mover', ['speed']);
  const edit = graphEditor(fixture, behavior);
  const held = edit.addNode('OnKeyHeld', { key: 'ArrowRight' });
  const owner = edit.addNode('Owner');
  const speed = edit.variables(['speed']);
  const mul = edit.addNode('Multiply');
  const move = edit.addNode('Move');
  edit.wire([
    [held, 'exec', move, 'exec'],
    [owner, 'object', move, 'object'],
    [speed, 'speed', mul, 'a'],
    [held, 'dt', mul, 'b'],
    [mul, 'result', move, 'dx'],
  ]);
  return { ...fixture, behavior, edit, nodes: { held, owner, speed, mul, move } };
}

/** A behavior "B" with the given number variables and an empty graph to edit. */
function emptyBehavior(variables: string[] = []) {
  const fixture = makeProject();
  const behavior = makeBehavior(fixture, 'B', variables);
  return { ...fixture, behavior, edit: graphEditor(fixture, behavior) };
}

describe('node registry', () => {
  it('registers the built-in node set with well-formed ports', () => {
    const defs = allNodeDefs();
    expect(defs.length).toBeGreaterThan(20);
    for (const def of defs) {
      const keys = [...def.inputs, ...def.outputs].map((p) => p.key);
      expect(new Set(def.inputs.map((p) => p.key)).size).toBe(def.inputs.length);
      expect(new Set(def.outputs.map((p) => p.key)).size).toBe(def.outputs.length);
      // An event is seeded by the runtime, so nothing flows into it.
      if (def.category === 'event') expect(def.inputs).toHaveLength(0);
      // A state is a name in a machine; its ports only anchor transitions, so it never runs.
      else if (def.category === 'state') expect(def.run).toBeUndefined();
      // A shader node is compiled to GLSL and a particle node to a function: neither is ever run.
      else if (def.category === 'shader' || def.category === 'particles') expect('emit' in def).toBe(true);
      else expect(def.run).toBeTypeOf('function');
      expect(keys.every((k) => k.length > 0)).toBe(true);
    }
  });

  it('type-checks port connections', () => {
    expect(portsCompatible('exec', 'exec')).toBe(true);
    expect(portsCompatible('exec', 'number')).toBe(false);
    expect(portsCompatible('number', 'any')).toBe(true);
    expect(portsCompatible('any', 'boolean')).toBe(true);
    expect(portsCompatible('number', 'boolean')).toBe(false);
    expect(portsCompatible('object', 'object')).toBe(true);
  });
});

describe('GraphInterpreter', () => {
  it('runs an event pulse and pulls data lazily (speed × dt moves the owner)', () => {
    const { behavior } = withMover(makeProject());
    const interpreter = new GraphInterpreter(behavior.graph);
    const ctx = fakeContext({ variables: { speed: 100 } });
    const fired = interpreter.fire('OnKeyHeld', ctx, { dt: 0.5 }, (n) => n.params.key === 'ArrowRight');
    expect(fired).toBe(1);
    expect(ctx.owner!.x).toBe(50);
    expect(interpreter.fire('OnKeyHeld', ctx, { dt: 0.5 }, (n) => n.params.key === 'ArrowLeft')).toBe(0);
    expect(ctx.owner!.x).toBe(50);
  });

  it('uses inline values for unconnected inputs', () => {
    const { behavior, edit } = emptyBehavior();
    const start = edit.addNode('OnStart');
    const self = edit.addNode('Self');
    const move = edit.addNode('Move', { dx: 7, dy: -3 });
    edit.wire([
      [start, 'exec', move, 'exec'],
      [self, 'object', move, 'object'],
    ]);
    const ctx = fakeContext();
    new GraphInterpreter(behavior.graph).fire('OnStart', ctx);
    expect(ctx.self.x).toBe(7);
    expect(ctx.self.y).toBe(-3);
  });

  it('uses port defaults for unconnected inputs (Move scale = 1, Clamp 0…1)', () => {
    const { behavior, edit } = emptyBehavior();
    const start = edit.addNode('OnStart');
    const self = edit.addNode('Self');
    const clamp = edit.addNode('Clamp', { value: 5 });
    const move = edit.addNode('Move', { dx: 4 });
    edit.wire([
      [start, 'exec', move, 'exec'],
      [self, 'object', move, 'object'],
      [clamp, 'result', move, 'dy'],
    ]);
    const ctx = fakeContext();
    new GraphInterpreter(behavior.graph).fire('OnStart', ctx);
    expect(ctx.self.x).toBe(4); // scale defaulted to 1, not 0
    expect(ctx.self.y).toBe(1); // clamp(5, 0, 1)
  });

  it('five-node mover: Axis input → Move(dt from On update) moves speed × dt, diagonals normalized', () => {
    const { behavior, edit } = emptyBehavior(['speed']);
    const update = edit.addNode('OnUpdate');
    const owner = edit.addNode('Owner');
    const axis = edit.addNode('AxisInput');
    const speed = edit.variables(['speed']);
    const move = edit.addNode('Move');
    edit.wire([
      [update, 'exec', move, 'exec'],
      [update, 'dt', move, 'dt'],
      [owner, 'object', move, 'object'],
      [axis, 'x', move, 'dx'],
      [axis, 'y', move, 'dy'],
      [speed, 'speed', move, 'scale'],
    ]);
    expect(behavior.graph.nodes).toHaveLength(5);

    const interpreter = new GraphInterpreter(behavior.graph);
    const run = (keys: string[]) => {
      const ctx = fakeContext({ variables: { speed: 100 }, dt: 0.5, isKeyDown: (k) => keys.includes(k) });
      interpreter.fire('OnUpdate', ctx, { dt: 0.5 });
      return { x: ctx.owner!.x, y: ctx.owner!.y };
    };
    expect(run([])).toEqual({ x: 0, y: 0 });
    expect(run(['ArrowRight'])).toEqual({ x: 50, y: 0 });
    expect(run(['ArrowLeft'])).toEqual({ x: -50, y: 0 });
    expect(run(['ArrowUp'])).toEqual({ x: 0, y: -50 });
    const diagonal = run(['ArrowLeft', 'ArrowUp']);
    expect(Math.hypot(diagonal.x, diagonal.y)).toBeCloseTo(50, 6); // same distance as a straight move
    expect(diagonal.x).toBeCloseTo(-50 / Math.SQRT2, 6);
    expect(diagonal.y).toBeCloseTo(-50 / Math.SQRT2, 6);
    expect(run(['ArrowLeft', 'ArrowRight'])).toEqual({ x: 0, y: 0 }); // opposite keys cancel
  });

  it('vector and math helpers', () => {
    const { behavior, edit } = emptyBehavior();
    const start = edit.addNode('OnStart');
    const sources = [
      edit.addNode('Normalize', { x: 3, y: 4 }),
      edit.addNode('Length', { x: 3, y: 4 }),
      edit.addNode('Sqrt', { value: 16 }),
      edit.addNode('Abs', { value: -2 }),
      edit.addNode('Min', { a: 3, b: -1 }),
      edit.addNode('Max', { a: 3, b: -1 }),
    ];
    const ports = ['x', 'result', 'result', 'result', 'result', 'result'];
    // One Log per source, chained after On start.
    let previous = start;
    sources.forEach((source, i) => {
      const log = edit.addNode('Log');
      edit.wire([
        [previous, 'exec', log, 'exec'],
        [source, ports[i]!, log, 'message'],
      ]);
      previous = log;
    });
    const ctx = fakeContext();
    new GraphInterpreter(behavior.graph).fire('OnStart', ctx);
    expect(ctx.logs).toEqual(['0.6', '5', '4', '2', '-1', '3']);
  });

  it('follows Branch, writes variables and logs', () => {
    const { behavior, edit } = emptyBehavior(['count']);
    const start = edit.addNode('OnStart');
    const get = edit.variables(['count']);
    const cmp = edit.addNode('Compare', { op: '<', b: 3 });
    const branch = edit.addNode('Branch');
    const add = edit.addNode('Add', { b: 1 });
    const set = edit.variables(['count'], { write: true });
    const logThen = edit.addNode('Log', { message: 'then' });
    const logElse = edit.addNode('Log', { message: 'else' });
    edit.wire([
      [start, 'exec', branch, 'exec'],
      [get, 'count', cmp, 'a'],
      [cmp, 'result', branch, 'condition'],
      [branch, 'then', set, 'exec'],
      [get, 'count', add, 'a'],
      [add, 'result', set, 'count'],
      [set, 'exec', logThen, 'exec'],
      [branch, 'else', logElse, 'exec'],
    ]);

    const interpreter = new GraphInterpreter(behavior.graph);
    const ctx = fakeContext({ variables: { count: 0 } });
    for (let i = 0; i < 5; i++) interpreter.fire('OnStart', ctx);
    expect(ctx.variables.count).toBe(3);
    expect(ctx.logs).toEqual(['then', 'then', 'then', 'else', 'else']);
  });

  it('reports traversed edges and nodes to the trace listener', () => {
    const { behavior, nodes } = withMover(makeProject());
    const interpreter = new GraphInterpreter(behavior.graph);
    const edges: string[] = [];
    const visited: string[] = [];
    interpreter.trace = { onEdge: (id) => edges.push(id), onNode: (id) => visited.push(id) };
    interpreter.fire('OnKeyHeld', fakeContext(), { dt: 1 });
    expect(edges).toHaveLength(1);
    expect(visited).toContain(nodes.mul.id);
    expect(visited).toContain(nodes.move.id);
  });

  it('stops a runaway flow instead of hanging', () => {
    const { behavior, edit } = emptyBehavior();
    const start = edit.addNode('OnStart');
    const a = edit.addNode('Sequence');
    const b = edit.addNode('Sequence');
    edit.wire([
      [start, 'exec', a, 'exec'],
      [a, 'a', b, 'exec'],
      [b, 'a', a, 'exec'],
    ]);
    expect(() => new GraphInterpreter(behavior.graph).fire('OnStart', fakeContext())).toThrow(
      /nested too deeply/,
    );
  });

  it('stops a loop that would run forever', () => {
    const { behavior, edit } = emptyBehavior(['count']);
    const start = edit.addNode('OnStart');
    const repeat = edit.addNode('Repeat', { times: 10_000_000 });
    const log = edit.addNode('Log', { message: 'x' });
    edit.wire([
      [start, 'exec', repeat, 'exec'],
      [repeat, 'body', log, 'exec'],
    ]);
    expect(() => new GraphInterpreter(behavior.graph).fire('OnStart', fakeContext())).toThrow(/step limit/);
  });
});

describe('Object by name', () => {
  /** Both graphs below name "Target"; only the way the name reaches the node differs. */
  function lookup(nodeParams: Record<string, string>, wireName: boolean) {
    const { behavior, edit } = emptyBehavior();
    const start = edit.addNode('OnStart');
    const byName = edit.addNode('ObjectByName', nodeParams);
    const log = edit.addNode('Log');
    edit.wire([
      [start, 'exec', log, 'exec'],
      [byName, 'object', log, 'message'],
    ]);
    if (wireName) {
      const join = edit.addNode('Join', { a: 'Tar', b: 'get' });
      edit.wire([[join, 'text', byName, 'name']]);
    }
    const ctx = fakeContext({ findByName: (name) => (name === 'Target' ? fakeEntity('Target') : null) });
    new GraphInterpreter(behavior.graph).fire('OnStart', ctx);
    return ctx.logs;
  }

  it('still reads a name stored as a node setting, the way every saved project holds it', () => {
    expect(lookup({ name: 'Target' }, false)).toEqual(['Target']);
  });

  it('takes a name put together at runtime', () => {
    expect(lookup({}, true)).toEqual(['Target']);
  });
});

/**
 * A loop is the one place where the per-pulse data cache would lie: every round has to read its
 * inputs anew, or the body would keep computing with the values of the first round.
 */
describe('Repeat', () => {
  /** "count = count + index" in the body of a Repeat, so the sum proves each round saw its own index. */
  function summingLoop(times: number) {
    const fixture = emptyBehavior(['count']);
    const { edit } = fixture;
    const start = edit.addNode('OnStart');
    const repeat = edit.addNode('Repeat', { times });
    const get = edit.variables(['count']);
    const add = edit.addNode('Add');
    const set = edit.variables(['count'], { write: true });
    edit.wire([
      [start, 'exec', repeat, 'exec'],
      [repeat, 'body', set, 'exec'],
      [get, 'count', add, 'a'],
      [repeat, 'index', add, 'b'],
      [add, 'result', set, 'count'],
    ]);
    return { ...fixture, nodes: { repeat, set } };
  }

  it('runs the body once per round, each round seeing its own index', () => {
    const { behavior } = summingLoop(5);
    const ctx = fakeContext({ variables: { count: 0 } });
    new GraphInterpreter(behavior.graph).fire('OnStart', ctx);
    // 0+1+2+3+4. A stale data cache would add the first round's index five times (0) instead.
    expect(ctx.variables.count).toBe(10);
  });

  it('runs nothing at all for a count of zero', () => {
    const { behavior } = summingLoop(0);
    const ctx = fakeContext({ variables: { count: 7 } });
    new GraphInterpreter(behavior.graph).fire('OnStart', ctx);
    expect(ctx.variables.count).toBe(7);
  });

  it('continues along done when the rounds are over', () => {
    const { behavior, edit, nodes } = summingLoop(3);
    const done = edit.addNode('Log', { message: 'done' });
    edit.wire([[nodes.repeat, 'done', done, 'exec']]);
    const ctx = fakeContext({ variables: { count: 0 } });
    new GraphInterpreter(behavior.graph).fire('OnStart', ctx);
    expect({ count: ctx.variables.count, logs: ctx.logs }).toEqual({ count: 3, logs: ['done'] });
  });

  it('nests: the inner loop starts over for every round of the outer one', () => {
    const { behavior, edit } = emptyBehavior(['count']);
    const start = edit.addNode('OnStart');
    const outer = edit.addNode('Repeat', { times: 3 });
    const inner = edit.addNode('Repeat', { times: 4 });
    const get = edit.variables(['count']);
    const add = edit.addNode('Add', { b: 1 });
    const set = edit.variables(['count'], { write: true });
    edit.wire([
      [start, 'exec', outer, 'exec'],
      [outer, 'body', inner, 'exec'],
      [inner, 'body', set, 'exec'],
      [get, 'count', add, 'a'],
      [add, 'result', set, 'count'],
    ]);
    const ctx = fakeContext({ variables: { count: 0 } });
    new GraphInterpreter(behavior.graph).fire('OnStart', ctx);
    expect(ctx.variables.count).toBe(12);
  });

  it('leaves the world alone after the loop: what follows reads current values, not the last round', () => {
    const { behavior, edit } = emptyBehavior(['count']);
    const start = edit.addNode('OnStart');
    const repeat = edit.addNode('Repeat', { times: 3 });
    const get = edit.variables(['count']);
    const add = edit.addNode('Add', { b: 1 });
    const set = edit.variables(['count'], { write: true });
    const after = edit.variables(['count'], { write: true });
    const afterAdd = edit.addNode('Multiply', { b: 10 });
    edit.wire([
      [start, 'exec', repeat, 'exec'],
      [repeat, 'body', set, 'exec'],
      [get, 'count', add, 'a'],
      [add, 'result', set, 'count'],
      [repeat, 'done', after, 'exec'],
      [get, 'count', afterAdd, 'a'],
      [afterAdd, 'result', after, 'count'],
    ]);
    const ctx = fakeContext({ variables: { count: 0 } });
    new GraphInterpreter(behavior.graph).fire('OnStart', ctx);
    // 3 rounds, then ×10 on the *current* count – a cache left over from the last round would give 20.
    expect(ctx.variables.count).toBe(30);
  });
});

describe('graph commands', () => {
  it('rejects incompatible, self and duplicate connections', () => {
    const {
      edit,
      nodes: { held, mul, move },
    } = withMover(makeProject());
    expect(() => edit.connect(held, 'exec', mul, 'a')).toThrow(/Cannot connect/);
    expect(() => edit.connect(mul, 'result', mul, 'a')).toThrow(/itself/);
    expect(() => edit.connect(held, 'exec', move, 'exec')).toThrow(/Already/);
    expect(() => edit.connect(held, 'nope', move, 'exec')).toThrow(/Port/);
  });

  it('replaces the edge of a data input and restores it on undo', () => {
    const { behavior, stack, edit, nodes } = withMover(makeProject());
    const literal = edit.addNode('Number', { value: 9 });
    const before = behavior.graph.edges.length;
    edit.connect(literal, 'value', nodes.move, 'dx');
    expect(behavior.graph.edges.length).toBe(before); // one replaced, one added
    const sourceOfDx = () =>
      behavior.graph.edges.find((e) => e.to.node === nodes.move.id && e.to.port === 'dx')!.from.node;
    expect(sourceOfDx()).toBe(literal.id);
    stack.undo();
    expect(sourceOfDx()).toBe(nodes.mul.id);
  });

  it('removing a node drops its edges; undo restores both', () => {
    const { behavior, stack, nodes } = withMover(makeProject());
    const edgesBefore = behavior.graph.edges.length;
    stack.execute(new RemoveNodeCommand(behavior.id, nodes.mul.id));
    expect(findNode(behavior.graph, nodes.mul.id)).toBeUndefined();
    expect(behavior.graph.edges.length).toBe(edgesBefore - 3);
    stack.undo();
    expect(findNode(behavior.graph, nodes.mul.id)).toBeDefined();
    expect(behavior.graph.edges.length).toBe(edgesBefore);
    stack.execute(new DisconnectCommand(behavior.id, behavior.graph.edges[0]!.id));
    expect(behavior.graph.edges.length).toBe(edgesBefore - 1);
    stack.undo();
    expect(behavior.graph.edges.length).toBe(edgesBefore);
  });

  it('coerces declared params and keeps inline input values', () => {
    const { behavior, stack, nodes } = withMover(makeProject());
    stack.execute(new SetNodeParamCommand(behavior.id, nodes.held.id, 'key', 'ArrowLeft'));
    stack.execute(new SetNodeParamCommand(behavior.id, nodes.move.id, 'dy', 4));
    const held = findNode(behavior.graph, nodes.held.id)!;
    const move = findNode(behavior.graph, nodes.move.id)!;
    expect(held.params.key).toBe('ArrowLeft');
    expect(move.params.dy).toBe(4);
    stack.undo();
    expect(move.params.dy).toBeUndefined();
  });
});

describe('variable commands', () => {
  it('adds, renames (including graph references and overrides) and removes variables', () => {
    const f = withMover(makeSpriteScene());
    const { behavior, stack, nodes, object } = f;
    const logic = place(f, behavior.id, { x: 0, y: 0 });
    object(logic).overrides.speed = 5;

    stack.execute(new RenameVariableCommand(behavior.id, 'speed', 'velocity'));
    expect(behavior.variables[0]!.key).toBe('velocity');
    expect(behavior.props).toEqual({ enabled: true, runInEditor: false, velocity: 0 });
    expect(object(logic).overrides).toEqual({ velocity: 5 });
    expect(findNode(behavior.graph, nodes.speed.id)!.ports).toEqual([{ key: 'velocity', kind: 'number' }]);
    stack.undo();
    expect(behavior.variables[0]!.key).toBe('speed');
    expect(object(logic).overrides).toEqual({ speed: 5 });

    expect(() => stack.execute(new AddVariableCommand(behavior.id, 'speed', 'number'))).toThrow(/already/);
    expect(() => stack.execute(new AddVariableCommand(behavior.id, '1bad', 'number'))).toThrow(/names/);

    stack.execute(new RemoveVariableCommand(behavior.id, 'speed'));
    expect(behavior.variables).toHaveLength(0);
    expect(object(logic).overrides).toEqual({});
    stack.undo();
    expect(behavior.variables).toHaveLength(1);
    expect(object(logic).overrides).toEqual({ speed: 5 });
  });
});

describe('behavior serialization', () => {
  it('round-trips variables and graph, dropping unknown node types and dangling edges', () => {
    const { project, behavior } = withMover(makeProject());
    const loaded = findAsset(roundTrip(project), behavior.id) as BehaviorAsset;
    expect(loaded.variables).toEqual(behavior.variables);
    expect(loaded.graph).toEqual(behavior.graph);
    expect(loaded.props).toEqual({ enabled: true, speed: 0 });

    const raw = serializeProject(project) as {
      assets: { id: string; graph?: { nodes: unknown[]; edges: unknown[] } }[];
    };
    const rawGraph = raw.assets.find((a) => a.id === behavior.id)!.graph!;
    rawGraph.nodes.push({ id: 'zzz', type: 'DoesNotExist', x: 0, y: 0, params: {} });
    rawGraph.edges.push({
      id: 'e-bad',
      from: { node: 'zzz', port: 'exec' },
      to: { node: behavior.graph.nodes[0]!.id, port: 'exec' },
    });
    const cleaned = findAsset(deserializeProject(raw), behavior.id) as BehaviorAsset;
    expect(cleaned.graph.nodes.length).toBe(behavior.graph.nodes.length);
    expect(cleaned.graph.edges.length).toBe(behavior.graph.edges.length);
  });

  it('keeps a node param that is a whole list or a struct, not just a single value', () => {
    const { project, behavior, edit } = emptyBehavior();
    const list = edit.addNode('List', { value: [3, 1, 4] });
    const struct = edit.addNode('Number', { bundle: { x: 2, tags: ['a'] } });
    const loaded = findAsset(roundTrip(project), behavior.id) as BehaviorAsset;
    expect(findNode(loaded.graph, list.id)!.params.value).toEqual([3, 1, 4]);
    expect(findNode(loaded.graph, struct.id)!.params.bundle).toEqual({ x: 2, tags: ['a'] });
  });
});

describe('unknown node types', () => {
  it('are rejected as a CommandError by execute, not thrown from the constructor', () => {
    const fixture = makeProject();
    const behavior = makeBehavior(fixture, 'B');
    // Building the command must not throw: callers construct it outside the editor's
    // error handling (`state.execute(new AddNodeCommand(…))`), so a throw here would crash.
    const command = new AddNodeCommand(behavior.id, 'DoesNotExist', 0, 0);
    expect(command.label).toBe('Add DoesNotExist');
    expect(() => command.execute(fixture.project)).toThrow(CommandError);
    expect(behavior.graph.nodes).toHaveLength(0);
  });
});

describe('dropping an edge on a node', () => {
  /** A behavior with a number source and a Clamp, so a drag has several compatible inputs. */
  function fixtureWithClamp() {
    const fixture = makeProject();
    const behavior = makeBehavior(fixture, 'B');
    const edit = graphEditor(fixture, behavior);
    return { graph: behavior.graph, edit, number: edit.addNode('Number'), clamp: edit.addNode('Clamp') };
  }

  it('picks the first compatible input', () => {
    const { graph, number, clamp } = fixtureWithClamp();
    const from = { nodeId: number.id, port: 'value', isOutput: true };
    expect(dropTargetPort(graph, from, clamp.id, NO_LOOKUP)).toEqual({
      nodeId: clamp.id,
      port: 'value',
      isOutput: false,
    });
  });

  it('skips inputs that already hold an edge', () => {
    const { graph, edit, number, clamp } = fixtureWithClamp();
    const other = edit.addNode('Number');
    edit.connect(other, 'value', clamp, 'value');
    const from = { nodeId: number.id, port: 'value', isOutput: true };
    expect(dropTargetPort(graph, from, clamp.id, NO_LOOKUP)?.port).toBe('min');
  });

  it('falls back to the last compatible input once every one is taken', () => {
    const { graph, edit, number, clamp } = fixtureWithClamp();
    for (const port of ['value', 'min', 'max']) edit.connect(edit.addNode('Number'), 'value', clamp, port);
    const from = { nodeId: number.id, port: 'value', isOutput: true };
    // Not free, but the drop still connects – it replaces the edge, as dropping on the port would.
    expect(dropTargetPort(graph, from, clamp.id, NO_LOOKUP)?.port).toBe('max');
  });

  it('keeps offering an exec input, which is never exclusive', () => {
    const fixture = makeProject();
    const behavior = makeBehavior(fixture, 'B');
    const edit = graphEditor(fixture, behavior);
    const held = edit.addNode('OnKeyHeld');
    const move = edit.addNode('SetPosition');
    edit.connect(edit.addNode('OnKeyHeld'), 'exec', move, 'exec');
    const from = { nodeId: held.id, port: 'exec', isOutput: true };
    expect(dropTargetPort(behavior.graph, from, move.id, NO_LOOKUP)?.port).toBe('exec');
  });

  it('refuses a node that offers nothing compatible, and the node itself', () => {
    const { graph, edit, number, clamp } = fixtureWithClamp();
    const boolean = edit.addNode('Boolean');
    const from = { nodeId: number.id, port: 'value', isOutput: true };
    expect(dropTargetPort(graph, from, boolean.id, NO_LOOKUP)).toBeNull();
    expect(dropTargetPort(graph, from, number.id, NO_LOOKUP)).toBeNull();
    // A pair that is already wired is not offered again either.
    edit.connect(number, 'value', clamp, 'value');
    edit.connect(number, 'value', clamp, 'min');
    edit.connect(number, 'value', clamp, 'max');
    expect(dropTargetPort(graph, from, clamp.id, NO_LOOKUP)).toBeNull();
  });

  it('resolves a drag started at an input to an output', () => {
    const { graph, number, clamp } = fixtureWithClamp();
    const from = { nodeId: clamp.id, port: 'value', isOutput: false };
    expect(dropTargetPort(graph, from, number.id, NO_LOOKUP)).toEqual({
      nodeId: number.id,
      port: 'value',
      isOutput: true,
    });
  });
});

describe('the palette offered when an edge is dropped into empty space', () => {
  const offers = (type: string, fromType: PortType, fromIsOutput: boolean) =>
    defAcceptsFrom(requireNodeDef(type), fromType, fromIsOutput);

  it('offers only nodes with a matching input when the drag started at an output', () => {
    expect(offers('Move', 'exec', true)).toBe(true);
    expect(offers('Clamp', 'number', true)).toBe(true);
    // An exec output has no business at a data node, nor a number at a node without number inputs.
    expect(offers('Number', 'exec', true)).toBe(false);
    expect(offers('OnUpdate', 'number', true)).toBe(false);
  });

  it('looks at outputs instead when the drag started at an input', () => {
    expect(offers('Number', 'number', false)).toBe(true);
    expect(offers('OnUpdate', 'exec', false)).toBe(true);
    expect(offers('Number', 'exec', false)).toBe(false);
    expect(offers('StopGame', 'number', false)).toBe(false);
  });

  it('lets `any` match every data type, but never exec', () => {
    expect(offers('Log', 'number', true)).toBe(true);
    expect(offers('Log', 'string', true)).toBe(true);
    expect(offers('ToText', 'exec', true)).toBe(false);
  });

  it('wires the picked node to its first compatible port', () => {
    expect(firstPortFor(requireNodeDef('Clamp'), 'number', true)).toBe('value');
    expect(firstPortFor(requireNodeDef('Move'), 'exec', true)).toBe('exec');
    expect(firstPortFor(requireNodeDef('Number'), 'number', false)).toBe('value');
    expect(firstPortFor(requireNodeDef('Number'), 'exec', true)).toBeNull();
  });
});