import { edgesInto, edgesOfNode, findNode, type Graph, type GraphEdge, type GraphNode } from '../graph/Graph';
import type { GraphLookup } from '../graph/lookup';
import { isTerminalType, resolveDef, terminalNode } from '../graph/nested';
import { nextTransitionName, parallelTransitions } from '../graph/stateMachine';
import { nodeDef, portsMeet, takesManyEdges } from '../graph/NodeRegistry';
import { graphLookup } from '../model/graphLookup';
import { newId } from '../ids';
import type { PropertyBag, PropertyValue } from '../model/Properties';
import type { Project } from '../model/Project';
import { coerceValue, defaultsOf } from '../properties/PropertySchema';
import { type Removed, removeById, removeFirst, removeWhere, restoreAt } from '../util/list';
import { type Command, CommandError } from './Command';
import { requireEdge, requireGraph, requireNode, requireNodeDef } from './require';
import { SetBagValueCommand } from './SetBagValueCommand';

export class AddNodeCommand implements Command {
  readonly label: string;
  readonly node: GraphNode;
  /** The end of the block the node opens (`Find` → `Match`), added beside it in the same step. */
  readonly closing: GraphNode | null;

  constructor(
    private readonly assetId: string,
    type: string,
    x: number,
    y: number,
    params: PropertyBag = {},
  ) {
    // An unknown type is rejected in `execute`: constructors run outside the editor's error
    // handling, so throwing here would crash instead of showing a notice.
    const def = nodeDef(type);
    this.node = {
      id: newId(),
      type,
      x: Math.round(x),
      y: Math.round(y),
      params: { ...defaultsOf(def?.params ?? []), ...params },
    };
    const opens = def?.opens;
    this.closing = opens
      ? {
          id: newId(),
          type: opens.type,
          x: this.node.x + opens.dx,
          y: this.node.y,
          params: defaultsOf(nodeDef(opens.type)?.params ?? []),
        }
      : null;
    this.label = def ? `Add ${def.label}` : `Add ${type}`;
  }

  execute(project: Project): void {
    requireNodeDef(this.node.type);
    const graph = requireGraph(project, this.assetId);
    // The two terminals give the behavior its signature; a second one of either would make
    // "which ports does this behavior have" ambiguous.
    if (isTerminalType(this.node.type) && terminalNode(graph, this.node.type))
      throw new CommandError(`This graph already has a ${nodeDef(this.node.type)?.label} node`);
    graph.nodes.push(this.node);
    if (this.closing) graph.nodes.push(this.closing);
  }

  undo(project: Project): void {
    const graph = requireGraph(project, this.assetId);
    graph.nodes = removeById(graph.nodes, this.node.id);
    if (this.closing) graph.nodes = removeById(graph.nodes, this.closing.id);
  }
}

/** Removes a node and every edge touching it. */
export class RemoveNodeCommand implements Command {
  readonly label = 'Remove node';
  private removed?: { node: Removed<GraphNode>; edges: Removed<GraphEdge>[] };

  constructor(
    private readonly assetId: string,
    private readonly nodeId: string,
  ) {}

  execute(project: Project): void {
    const graph = requireGraph(project, this.assetId);
    const node = removeFirst(graph.nodes, (n) => n.id === this.nodeId);
    if (!node) throw new CommandError(`Node ${this.nodeId} not found`);
    // `edgesOfNode` reads the edge list only, so it still finds them after the node is gone.
    const touching = edgesOfNode(graph, this.nodeId);
    this.removed = { node, edges: removeWhere(graph.edges, (e) => touching.includes(e)) };
  }

  undo(project: Project): void {
    if (!this.removed) return;
    const graph = requireGraph(project, this.assetId);
    restoreAt(graph.nodes, [this.removed.node]);
    restoreAt(graph.edges, this.removed.edges);
  }
}

/**
 * The previous position is read at execution time, so a caller that previewed the drag must restore
 * the node before executing.
 */
export class MoveNodeCommand implements Command {
  readonly label = 'Move node';
  private previous = { x: 0, y: 0 };

  constructor(
    private readonly assetId: string,
    private readonly nodeId: string,
    private readonly x: number,
    private readonly y: number,
  ) {}

  execute(project: Project): void {
    const node = requireNode(project, this.assetId, this.nodeId);
    this.previous = { x: node.x, y: node.y };
    node.x = Math.round(this.x);
    node.y = Math.round(this.y);
  }

  undo(project: Project): void {
    const node = requireNode(project, this.assetId, this.nodeId);
    node.x = this.previous.x;
    node.y = this.previous.y;
  }
}

/**
 * Sets a node param or the inline value of an unconnected data input. A param can decide how many
 * ports the node has, so this takes the edges of ports the new value does away with: an edge on a
 * port that is gone draws as nothing but survives every save, and comes back to life if the port
 * ever returns.
 */
export class SetNodeParamCommand extends SetBagValueCommand<GraphNode> {
  private orphans: Removed<GraphEdge>[] = [];

  constructor(
    private readonly assetId: string,
    private readonly nodeId: string,
    key: string,
    private readonly value: PropertyValue,
  ) {
    super(key, `Set ${key}`);
  }

  override execute(project: Project): void {
    const graph = requireGraph(project, this.assetId);
    const lookup = graphLookup(project);
    // A param can reshape another node too – a Find's mode decides its Match's outputs (#259).
    const held = new Set(graph.edges.filter((e) => edgeHolds(graph, e, lookup)));
    super.execute(project);
    this.orphans = removeWhere(
      graph.edges,
      (e) =>
        (held.has(e) || e.from.node === this.nodeId || e.to.node === this.nodeId) &&
        !edgeHolds(graph, e, lookup),
    );
  }

  override undo(project: Project): void {
    super.undo(project);
    restoreAt(requireGraph(project, this.assetId).edges, this.orphans);
  }

  protected override resolveTarget(project: Project): GraphNode {
    return requireNode(project, this.assetId, this.nodeId);
  }

  protected override bagOf(node: GraphNode): PropertyBag {
    return node.params;
  }

  protected override computeNext(node: GraphNode): PropertyValue {
    const param = requireNodeDef(node.type).params.find((p) => p.key === this.key);
    // Inline input values are stored as-is; declared params are coerced against their definition.
    return param && param.kind !== 'enum' ? coerceValue(param, this.value) : this.value;
  }
}

/** Whether both ends of an edge name a port their node has; a node of unknown type is not judged. */
function edgeHolds(graph: Graph, edge: GraphEdge, lookup: GraphLookup): boolean {
  const has = (end: GraphEdge['from'], side: 'inputs' | 'outputs') => {
    const node = findNode(graph, end.node);
    const def = node && resolveDef(node, graph, lookup);
    return !def || def[side].some((p) => p.key === end.port);
  };
  return has(edge.from, 'outputs') && has(edge.to, 'inputs');
}

/** A data input holds at most one edge, so an existing one is replaced (and restored on undo). */
export class ConnectCommand implements Command {
  readonly label = 'Connect';
  readonly edge: GraphEdge;
  private replaced: Removed<GraphEdge>[] = [];

  constructor(
    private readonly assetId: string,
    from: { node: string; port: string },
    to: { node: string; port: string },
  ) {
    this.edge = { id: newId(), from: { ...from }, to: { ...to } };
  }

  execute(project: Project): void {
    const graph = requireGraph(project, this.assetId);
    const fromNode = findNode(graph, this.edge.from.node);
    const toNode = findNode(graph, this.edge.to.node);
    if (!fromNode || !toNode) throw new CommandError('Node not found');
    const lookup = graphLookup(project);
    const fromDef = resolveDef(fromNode, graph, lookup);
    // A transition back into its own state re-enters it; any other edge onto its own node is a loop.
    if (fromNode === toNode && fromDef?.transitionEdges !== true)
      throw new CommandError('A node cannot connect to itself');
    const out = fromDef?.outputs.find((p) => p.key === this.edge.from.port);
    const toDef = resolveDef(toNode, graph, lookup);
    const inp = toDef?.inputs.find((p) => p.key === this.edge.to.port);
    if (!out || !inp) throw new CommandError('Port not found');
    if (!portsMeet(out, inp)) throw new CommandError(`Cannot connect ${out.type} to ${inp.type}`);
    if (graph.edges.some((e) => sameEnds(e, this.edge))) {
      // Transitions are told apart by name, so a further one between the same states gets its own.
      if (fromDef?.transitionEdges !== true || toDef?.transitionEdges !== true)
        throw new CommandError('Already connected');
      this.edge.label = nextTransitionName(graph, this.edge);
    }
    const occupied = takesManyEdges(inp) ? [] : edgesInto(graph, this.edge.to.node, this.edge.to.port);
    this.replaced = removeWhere(graph.edges, (e) => occupied.includes(e));
    graph.edges.push(this.edge);
  }

  undo(project: Project): void {
    const graph = requireGraph(project, this.assetId);
    graph.edges = removeById(graph.edges, this.edge.id);
    restoreAt(graph.edges, this.replaced);
  }
}

/** Folding is drawing only: the edge keeps carrying its value either way. */
export class FoldEdgeCommand implements Command {
  readonly label: string;
  private previous = false;

  constructor(
    private readonly assetId: string,
    private readonly edgeId: string,
    private readonly folded: boolean,
  ) {
    this.label = folded ? 'Hide link' : 'Show link';
  }

  execute(project: Project): void {
    const edge = requireEdge(project, this.assetId, this.edgeId);
    this.previous = edge.folded === true;
    this.apply(edge, this.folded);
  }

  undo(project: Project): void {
    this.apply(requireEdge(project, this.assetId, this.edgeId), this.previous);
  }

  private apply(edge: GraphEdge, folded: boolean): void {
    if (folded) edge.folded = true;
    else delete edge.folded;
  }
}

/** The name a transition answers to. Blank clears it, since an unnamed transition is the normal one. */
export class NameTransitionCommand implements Command {
  readonly label = 'Name transition';
  private previous = '';

  constructor(
    private readonly assetId: string,
    private readonly edgeId: string,
    private readonly name: string,
  ) {}

  execute(project: Project): void {
    const edge = requireEdge(project, this.assetId, this.edgeId);
    const name = this.name.trim();
    // Between the same two states the name is all that tells transitions apart.
    if (parallelTransitions(requireGraph(project, this.assetId), edge).some((e) => (e.label ?? '') === name))
      throw new CommandError(
        name
          ? `Another transition between these states is already called "${name}"`
          : 'Another transition between these states is already unnamed',
      );
    this.previous = edge.label ?? '';
    this.apply(edge, name);
  }

  undo(project: Project): void {
    this.apply(requireEdge(project, this.assetId, this.edgeId), this.previous);
  }

  private apply(edge: GraphEdge, name: string): void {
    if (name) edge.label = name;
    else delete edge.label;
  }
}

/** One undo step for the whole selection; every node is found before any of them changes. */
export class CollapseNodesCommand implements Command {
  readonly label: string;
  private previous: boolean[] = [];

  constructor(
    private readonly assetId: string,
    private readonly nodeIds: readonly string[],
    private readonly collapsed: boolean,
  ) {
    const noun = nodeIds.length === 1 ? 'node' : 'nodes';
    this.label = collapsed ? `Collapse ${noun}` : `Expand ${noun}`;
  }

  execute(project: Project): void {
    const nodes = this.nodeIds.map((id) => requireNode(project, this.assetId, id));
    this.previous = nodes.map((n) => n.collapsed === true);
    for (const node of nodes) setCollapsed(node, this.collapsed);
  }

  undo(project: Project): void {
    this.nodeIds.forEach((id, i) => setCollapsed(requireNode(project, this.assetId, id), this.previous[i]!));
  }
}

function setCollapsed(node: GraphNode, collapsed: boolean): void {
  if (collapsed) node.collapsed = true;
  else delete node.collapsed;
}

export class DisconnectCommand implements Command {
  readonly label = 'Disconnect';
  private removed: Removed<GraphEdge>[] = [];

  constructor(
    private readonly assetId: string,
    private readonly edgeId: string,
  ) {}

  execute(project: Project): void {
    const graph = requireGraph(project, this.assetId);
    this.removed = removeWhere(graph.edges, (e) => e.id === this.edgeId);
    if (this.removed.length === 0) throw new CommandError(`Edge ${this.edgeId} not found`);
  }

  undo(project: Project): void {
    restoreAt(requireGraph(project, this.assetId).edges, this.removed);
  }
}

function sameEnds(a: GraphEdge, b: GraphEdge): boolean {
  return (
    a.from.node === b.from.node &&
    a.from.port === b.from.port &&
    a.to.node === b.to.node &&
    a.to.port === b.to.port
  );
}