import { type MindMapEdge, type MindMapNode, type Position } from '@/types/map';

/**
 * Compare deux freres.
 *
 * `order` fait foi ; a defaut, l'ordre d'apparition dans le tableau `nodes`
 * sert de repli, ce qui reproduit exactement le comportement d'avant la v3 pour
 * les cartes qui n'ont pas encore d'ordre explicite.
 */
export function compareSiblings(
  a: MindMapNode,
  b: MindMapNode,
  indexById: Map<string, number>,
): number {
  const orderA = a.order ?? Number.MAX_SAFE_INTEGER;
  const orderB = b.order ?? Number.MAX_SAFE_INTEGER;
  if (orderA !== orderB) return orderA - orderB;
  return (indexById.get(a.id) ?? 0) - (indexById.get(b.id) ?? 0);
}

function buildIndex(nodes: MindMapNode[]): Map<string, number> {
  const index = new Map<string, number>();
  nodes.forEach((node, position) => index.set(node.id, position));
  return index;
}

/**
 * Index parent -> enfants directs, tries par ordre de fratrie.
 * Construit une seule fois par operation.
 */
export function buildChildrenMap(nodes: MindMapNode[]): Map<string, string[]> {
  const byId = buildNodeMap(nodes);
  const indexById = buildIndex(nodes);
  const children = new Map<string, string[]>();

  for (const node of nodes) {
    if (!node.parentId) continue;
    const list = children.get(node.parentId);
    if (list) list.push(node.id);
    else children.set(node.parentId, [node.id]);
  }

  for (const list of children.values()) {
    if (list.length > 1) {
      list.sort((a, b) =>
        compareSiblings(byId.get(a) as MindMapNode, byId.get(b) as MindMapNode, indexById),
      );
    }
  }
  return children;
}

/** Enfants directs d'un noeud, dans l'ordre. `null` cible les racines. */
export function getOrderedChildren(
  nodes: MindMapNode[],
  parentId: string | null,
): MindMapNode[] {
  const byId = buildNodeMap(nodes);
  if (parentId === null) {
    const indexById = buildIndex(nodes);
    return getRootNodes(nodes).sort((a, b) => compareSiblings(a, b, indexById));
  }
  return (buildChildrenMap(nodes).get(parentId) ?? []).map((id) => byId.get(id) as MindMapNode);
}

/**
 * Renumerote les freres en 0..n-1, pour chaque parent et pour les racines.
 *
 * Appelee apres toute modification structurelle : l'ordre reste ainsi dense et
 * comparable, et les anciennes cartes recoivent un ordre explicite conforme a
 * leur affichage precedent.
 */
export function normalizeChildOrders(nodes: MindMapNode[]): MindMapNode[] {
  const indexById = buildIndex(nodes);
  const groups = new Map<string | null, MindMapNode[]>();
  const known = new Set(nodes.map((node) => node.id));

  for (const node of nodes) {
    // `null` regroupe les racines : aucune sentinelle textuelle a inventer.
    const key = node.parentId && known.has(node.parentId) ? node.parentId : null;
    const group = groups.get(key);
    if (group) group.push(node);
    else groups.set(key, [node]);
  }

  const orders = new Map<string, number>();
  for (const group of groups.values()) {
    group.sort((a, b) => compareSiblings(a, b, indexById));
    group.forEach((node, position) => orders.set(node.id, position));
  }

  let changed = false;
  const result = nodes.map((node) => {
    const order = orders.get(node.id) ?? 0;
    if (node.order === order) return node;
    changed = true;
    return { ...node, order };
  });
  return changed ? result : nodes;
}

/** Prochain rang libre parmi les enfants d'un parent. */
export function nextSiblingOrder(nodes: MindMapNode[], parentId: string | null): number {
  const siblings = nodes.filter((node) =>
    parentId === null ? !node.parentId : node.parentId === parentId,
  );
  if (siblings.length === 0) return 0;
  return Math.max(...siblings.map((node) => node.order ?? 0)) + 1;
}

export function buildNodeMap(nodes: MindMapNode[]): Map<string, MindMapNode> {
  return new Map(nodes.map((node) => [node.id, node]));
}

/** Racines de la carte : noeuds sans parent (ou dont le parent n'existe plus). */
export function getRootNodes(nodes: MindMapNode[]): MindMapNode[] {
  const ids = new Set(nodes.map((node) => node.id));
  return nodes.filter((node) => !node.parentId || !ids.has(node.parentId));
}

/** Profondeur de chaque noeud depuis sa racine (racine = 0). */
export function computeDepths(nodes: MindMapNode[]): Map<string, number> {
  const nodeMap = buildNodeMap(nodes);
  const depths = new Map<string, number>();

  const resolve = (id: string, seen: Set<string>): number => {
    const cached = depths.get(id);
    if (cached !== undefined) return cached;
    if (seen.has(id)) return 0; // securite : cycle impossible mais on ne boucle pas
    seen.add(id);

    const node = nodeMap.get(id);
    const parentId = node?.parentId;
    const depth = parentId && nodeMap.has(parentId) ? resolve(parentId, seen) + 1 : 0;
    depths.set(id, depth);
    return depth;
  };

  for (const node of nodes) resolve(node.id, new Set());
  return depths;
}

/** Tous les descendants d'un noeud (lui-meme exclu). */
export function getDescendantIds(nodes: MindMapNode[], rootId: string): string[] {
  const children = buildChildrenMap(nodes);
  const result: string[] = [];
  const queue = [...(children.get(rootId) ?? [])];

  while (queue.length > 0) {
    const current = queue.shift() as string;
    result.push(current);
    const next = children.get(current);
    if (next) queue.push(...next);
  }
  return result;
}

/** Un noeud plus tous ses descendants, sans doublon. */
export function withDescendants(nodes: MindMapNode[], ids: string[]): string[] {
  const collected = new Set<string>();
  for (const id of ids) {
    collected.add(id);
    for (const descendant of getDescendantIds(nodes, id)) collected.add(descendant);
  }
  return [...collected];
}

/** Noeuds masques parce qu'un ancetre est replie. */
export function getHiddenNodeIds(nodes: MindMapNode[]): Set<string> {
  const hidden = new Set<string>();
  const children = buildChildrenMap(nodes);

  for (const node of nodes) {
    if (!node.collapsed) continue;
    const queue = [...(children.get(node.id) ?? [])];
    while (queue.length > 0) {
      const current = queue.shift() as string;
      if (hidden.has(current)) continue;
      hidden.add(current);
      const next = children.get(current);
      if (next) queue.push(...next);
    }
  }
  return hidden;
}

/** Nombre de descendants masques par un noeud replie. */
export function countHiddenDescendants(nodes: MindMapNode[], nodeId: string): number {
  return getDescendantIds(nodes, nodeId).length;
}

/** Empeche de rattacher un noeud a l'un de ses propres descendants. */
export function wouldCreateCycle(
  nodes: MindMapNode[],
  childId: string,
  nextParentId: string,
): boolean {
  if (childId === nextParentId) return true;
  return getDescendantIds(nodes, childId).includes(nextParentId);
}

/**
 * Recalcule les liens a partir de la hierarchie : parentId fait autorite.
 * Les liens sont emis dans l'ordre de fratrie, ce dont dagre se sert pour
 * disposer les enfants dans le bon ordre.
 */
export function rebuildEdges(nodes: MindMapNode[]): MindMapEdge[] {
  const edges: MindMapEdge[] = [];
  for (const [parentId, childIds] of buildChildrenMap(nodes)) {
    for (const childId of childIds) {
      edges.push({ id: `e-${parentId}-${childId}`, source: parentId, target: childId });
    }
  }
  return edges;
}

/** Parcours en profondeur, racines et enfants dans l'ordre de fratrie. */
export function flattenInOrder(nodes: MindMapNode[]): MindMapNode[] {
  const byId = buildNodeMap(nodes);
  const children = buildChildrenMap(nodes);
  const indexById = buildIndex(nodes);
  const result: MindMapNode[] = [];
  const seen = new Set<string>();

  const visit = (node: MindMapNode): void => {
    if (seen.has(node.id)) return;
    seen.add(node.id);
    result.push(node);
    for (const childId of children.get(node.id) ?? []) {
      const child = byId.get(childId);
      if (child) visit(child);
    }
  };

  for (const root of getRootNodes(nodes).sort((a, b) => compareSiblings(a, b, indexById))) {
    visit(root);
  }
  // Securite : un noeud isole par une donnee incoherente reste present.
  for (const node of nodes) if (!seen.has(node.id)) result.push(node);
  return result;
}

/**
 * Restaure `parentId` a partir des liens.
 * Utilise a l'import, si un fichier fournit des liens mais pas de hierarchie.
 */
export function rebuildHierarchyFromEdges(
  nodes: MindMapNode[],
  edges: MindMapEdge[],
): MindMapNode[] {
  const parentByChild = new Map<string, string>();
  for (const edge of edges) {
    if (!parentByChild.has(edge.target)) parentByChild.set(edge.target, edge.source);
  }
  return nodes.map((node) =>
    node.parentId === undefined || node.parentId === null
      ? { ...node, parentId: parentByChild.get(node.id) ?? null }
      : node,
  );
}

/** Prochaine position libre pour un nouvel enfant, avant tout auto-layout. */
export function suggestChildPosition(
  nodes: MindMapNode[],
  parent: MindMapNode,
  horizontal: boolean,
  direction: 1 | -1,
): Position {
  return suggestChildPositions(nodes, parent, horizontal, direction, 1)[0] as Position;
}

const CHILD_GAP_Y = 72;
const CHILD_GAP_X = 200;

/**
 * Positions de depart pour `count` nouveaux enfants.
 *
 * Elles ne remplacent pas l'auto-layout : elles evitent seulement que plusieurs
 * noeuds crees d'un coup se superposent, en les repartissant autour du parent.
 */
export function suggestChildPositions(
  nodes: MindMapNode[],
  parent: MindMapNode,
  horizontal: boolean,
  direction: 1 | -1,
  count: number,
): Position[] {
  const existing = nodes.filter((node) => node.parentId === parent.id).length;
  const total = existing + count;
  const positions: Position[] = [];

  for (let index = 0; index < count; index += 1) {
    const slot = existing + index;
    if (horizontal) {
      positions.push({
        x: parent.position.x + direction * 220,
        y: parent.position.y + (slot - (total - 1) / 2) * CHILD_GAP_Y,
      });
    } else {
      positions.push({
        x: parent.position.x + (slot - (total - 1) / 2) * CHILD_GAP_X,
        y: parent.position.y + direction * 140,
      });
    }
  }
  return positions;
}