import type { PlaitElement } from "@plait/core";
import { getTopicEntries } from "./topic-details";

export type OutlineCommand =
  | "child"
  | "sibling"
  | "delete"
  | "indent"
  | "outdent"
  | "up"
  | "down";
export type OutlineDrop = {
  targetId: string;
  placement: "before" | "after" | "child";
};
const isSummary = (node: PlaitElement) =>
  Number.isInteger(node.start) && Number.isInteger(node.end);
const regular = (node: PlaitElement) =>
  (node.children || []).filter((child) => !isSummary(child));
const newTopic = (root = false): PlaitElement => ({
  id: crypto.randomUUID(),
  type: root ? "mindmap" : "mind_child",
  data: {
    topic: {
      type: "paragraph",
      children: [{ text: root ? "中心主题" : "新主题" }],
    },
  },
  children: [],
  ...(root
    ? { isRoot: true, layout: "standard", rightNodeCount: 0, points: [[0, 0]] }
    : {}),
});

/** Work on the model, including collapsed nodes that have no renderer path. */
export function applyOutlineCommand(
  elements: PlaitElement[],
  topicId: string | null,
  command: OutlineCommand | OutlineDrop
): { children: PlaitElement[]; selectedId: string } {
  const children = structuredClone(elements);
  if (!topicId) {
    if (command !== "child" || getTopicEntries(children).length)
      throw new Error("请先选择一个主题");
    const root = newTopic(true);
    children.push(root);
    return { children, selectedId: root.id };
  }
  const entries = getTopicEntries(children);
  const entry = entries.find(({ element }) => element.id === topicId);
  if (!entry) throw new Error("主题已不存在，请重新选择");
  const node = entry.element;
  const parentOf = (target: PlaitElement) =>
    entries.find(({ element }) => element.children?.includes(target))?.element;
  const parent = parentOf(node);
  const ranges = entries
    .filter(({ element }) => isSummary(element))
    .map(({ element }) => {
      const owner = parentOf(element)!;
      return {
        element,
        owner,
        ids: regular(owner)
          .slice(Number(element.start), Number(element.end) + 1)
          .map((child) => child.id),
      };
    });
  const remove = (target: PlaitElement) => {
    const owner = parentOf(target);
    const list = owner?.children || children;
    const index = list.indexOf(target);
    if (
      owner?.layout === "standard" &&
      !isSummary(target) &&
      index < Number(owner.rightNodeCount)
    )
      owner.rightNodeCount = Number(owner.rightNodeCount) - 1;
    list.splice(index, 1);
  };
  const insert = (owner: PlaitElement, target: PlaitElement, index: number) => {
    owner.children ||= [];
    const count = regular(owner).length;
    const at = Math.min(index, count);
    owner.children.splice(at, 0, target);
    if (owner.layout === "standard" && at <= Number(owner.rightNodeCount || 0))
      owner.rightNodeCount = Number(owner.rightNodeCount || 0) + 1;
    owner.isCollapsed = false;
  };
  let selectedId = node.id;
  if (command === "child" || command === "sibling") {
    const next = newTopic();
    if (command === "child") insert(node, next, regular(node).length);
    else {
      if (!parent || isSummary(node))
        throw new Error("中心主题和概要请使用新增子主题");
      insert(parent, next, parent.children!.indexOf(node) + 1);
    }
    selectedId = next.id;
  } else if (command === "delete") {
    const siblings = parent
      ? regular(parent)
      : children.filter((item) =>
          ["mind", "mindmap"].includes(String(item.type))
        );
    const index = siblings.indexOf(node);
    selectedId =
      siblings[index - 1]?.id || siblings[index + 1]?.id || parent?.id || "";
    remove(node);
  } else {
    if (!parent || isSummary(node))
      throw new Error("中心主题和概要暂不支持此层级调整");
    let target: PlaitElement | undefined;
    let placement: OutlineDrop["placement"] = "child";
    const siblings = regular(parent);
    const index = siblings.indexOf(node);
    if (typeof command === "object") {
      target = entries.find(
        ({ element }) => element.id === command.targetId
      )?.element;
      placement = command.placement;
    } else if (command === "indent") target = siblings[index - 1];
    else if (command === "outdent") {
      target = parent;
      placement = "after";
    } else {
      target = siblings[index + (command === "up" ? -1 : 1)];
      placement = command === "up" ? "before" : "after";
    }
    if (!target) throw new Error("此位置无法继续移动主题");
    if (isSummary(target)) throw new Error("请移动到普通主题附近");
    if (
      getTopicEntries([node]).some(({ element }) => element.id === target!.id)
    )
      throw new Error("不能把主题移入自身或它的子主题");
    const destination = placement === "child" ? target : parentOf(target);
    if (!destination) throw new Error("一级主题不能再提升层级");
    remove(node);
    const at =
      placement === "child"
        ? regular(destination).length
        : destination.children!.indexOf(target) +
          (placement === "after" ? 1 : 0);
    insert(destination, node, at);
  }
  // Keep summaries attached to their surviving topic range, never unrelated gaps.
  for (const range of ranges) {
    if (!range.owner.children?.includes(range.element)) continue;
    const indices = regular(range.owner).flatMap((child, index) =>
      range.ids.includes(child.id) ? [index] : []
    );
    if (!indices.length) {
      range.owner.children = range.owner.children.filter(
        (child) => child !== range.element
      );
      continue;
    }
    const start = indices[0];
    const end = indices[indices.length - 1];
    const newlyInserted = command === "child" || command === "sibling";
    if (!newlyInserted && end - start + 1 !== indices.length)
      throw new Error("移动会让概要范围断开，请先调整概要");
    range.element.start = start;
    range.element.end = end;
  }
  return { children, selectedId };
}

export function renameOutlineTopic(element: PlaitElement, title: string) {
  const data = element.data as Record<string, unknown>;
  const topic = data.topic as {
    children?: Record<string, unknown>[];
    type?: string;
  };
  return {
    ...data,
    topic: {
      ...topic,
      children: [
        { ...(topic.children?.[0] || {}), text: title.trim() || "未命名主题" },
      ],
    },
  };
}