import type { CategoryKind } from "@/shared/schemas/category";
import { compareTr } from "@/shared/search";

/**
 * Kategori ağacı saf fonksiyonları (framework'ten bağımsız, birim testli).
 * Derinlik pratikte 3 seviye; güvenlik için en fazla MAX_DEPTH seviye.
 */
export const MAX_DEPTH = 5;

export type FlatCategory = {
  id: string;
  kind: CategoryKind;
  name: string;
  parentId: string | null;
  order: number;
  archived: boolean;
};

export type CategoryNode<T extends FlatCategory = FlatCategory> = T & {
  depth: number;
  children: CategoryNode<T>[];
};

const bySortOrder = (a: FlatCategory, b: FlatCategory) =>
  a.order - b.order || compareTr(a.name, b.name);

/** Düz listeden ağaç kurar. Üstü bulunamayan (veya döngülü) düğümler köke alınır. */
export function buildTree<T extends FlatCategory>(items: readonly T[]): CategoryNode<T>[] {
  const nodes = new Map(
    items.map((c) => [c.id, { ...c, depth: 0, children: [] as CategoryNode<T>[] }]),
  );
  const roots: CategoryNode<T>[] = [];
  for (const node of nodes.values()) {
    const parent = node.parentId ? nodes.get(node.parentId) : undefined;
    if (parent && parent !== node) parent.children.push(node);
    else roots.push(node);
  }
  const visit = (list: CategoryNode<T>[], depth: number, seen: Set<string>) => {
    list.sort(bySortOrder);
    for (const n of list) {
      if (seen.has(n.id)) continue;
      seen.add(n.id);
      n.depth = depth;
      visit(n.children, depth + 1, seen);
    }
  };
  visit(roots, 0, new Set());
  return roots;
}

export type CategoryOption = {
  id: string;
  label: string;
  path: string;
  depth: number;
  kind: CategoryKind;
};

/** Seçim listesi (işlem formları): derinlik sırasıyla, "Faturalar › Elektrik" yoluyla. */
export function toOptions<T extends FlatCategory>(
  tree: CategoryNode<T>[],
  { includeArchived = false } = {},
): CategoryOption[] {
  const out: CategoryOption[] = [];
  const walk = (list: CategoryNode<T>[], prefix: string[]) => {
    for (const n of list) {
      if (n.archived && !includeArchived) continue;
      const path = [...prefix, n.name];
      out.push({ id: n.id, label: n.name, path: path.join(" › "), depth: n.depth, kind: n.kind });
      walk(n.children, path);
    }
  };
  walk(tree, []);
  return out;
}

/** `id`'nin tüm alt kategorileri (kendisi hariç). */
export function descendantIds(items: readonly FlatCategory[], id: string): string[] {
  const children = new Map<string, string[]>();
  for (const c of items)
    if (c.parentId) children.set(c.parentId, [...(children.get(c.parentId) ?? []), c.id]);
  const out: string[] = [];
  const stack = [...(children.get(id) ?? [])];
  while (stack.length) {
    const next = stack.pop()!;
    if (out.includes(next)) continue;
    out.push(next);
    stack.push(...(children.get(next) ?? []));
  }
  return out;
}

/** Kökten `id`'ye kadar üst kategori kimlikleri (id hariç). */
export function ancestorIds(items: readonly FlatCategory[], id: string): string[] {
  const byId = new Map(items.map((c) => [c.id, c]));
  const out: string[] = [];
  let cur = byId.get(id)?.parentId ?? null;
  while (cur && !out.includes(cur)) {
    out.unshift(cur);
    cur = byId.get(cur)?.parentId ?? null;
  }
  return out;
}

/** Alt ağacın yüksekliği (yaprak = 0). */
function subtreeHeight(items: readonly FlatCategory[], id: string): number {
  const kids = items.filter((c) => c.parentId === id);
  return kids.length ? 1 + Math.max(...kids.map((k) => subtreeHeight(items, k.id))) : 0;
}

export type MoveViolation =
  "self" | "descendant" | "kind" | "depth" | "parentNotFound" | "parentArchived";

/** `id` kategorisi `newParentId` altına (null = kök) taşınabilir mi? */
export function checkMove(
  items: readonly FlatCategory[],
  id: string,
  newParentId: string | null,
): MoveViolation | null {
  if (newParentId === null) return null;
  if (newParentId === id) return "self";
  const parent = items.find((c) => c.id === newParentId);
  const self = items.find((c) => c.id === id);
  if (!parent || !self) return "parentNotFound";
  if (parent.kind !== self.kind) return "kind";
  if (parent.archived) return "parentArchived";
  if (descendantIds(items, id).includes(newParentId)) return "descendant";
  const newDepth = ancestorIds(items, newParentId).length + 1;
  if (newDepth + subtreeHeight(items, id) >= MAX_DEPTH) return "depth";
  return null;
}

/** Yeni kategori `parentId` altına eklenebilir mi? */
export function checkCreate(
  items: readonly FlatCategory[],
  kind: CategoryKind,
  parentId: string | null,
): MoveViolation | null {
  if (!parentId) return null;
  const parent = items.find((c) => c.id === parentId);
  if (!parent) return "parentNotFound";
  if (parent.kind !== kind) return "kind";
  if (parent.archived) return "parentArchived";
  if (ancestorIds(items, parentId).length + 1 >= MAX_DEPTH) return "depth";
  return null;
}

/**
 * Kategori bazlı tutarları üst kategorilere toplar (raporlar ve bütçe için):
 * her kategori kendi tutarı + tüm alt kategorilerinin tutarı.
 */
export function rollupTotals(
  items: readonly FlatCategory[],
  totals: ReadonlyMap<string, number>,
): Map<string, number> {
  const out = new Map<string, number>();
  for (const c of items) {
    const own = totals.get(c.id) ?? 0;
    for (const target of [c.id, ...ancestorIds(items, c.id)])
      out.set(target, (out.get(target) ?? 0) + own);
  }
  return out;
}