// @ts-check

import crel, { fragment } from "./crel.js";
import pluralize from "./pluralize.js";
import formatBytes from "./formatBytes.js";
import allChildrenOf from "./allChildrenOf.js";
import * as nodePath from "./nodePath.js";
/** @typedef {import("./nodePath.js").NodePath} NodePath */
/** @typedef {import("../../types/png.d.ts").PngNode} PngNode */

/**
 * @typedef {Function} NodeUiFn
 * @param {PngNode} node
 * @returns {NodeUi}
 */

/**
 * @typedef {object} HoveringOver
 * @prop {"bytes" | "tree"} side
 * @prop {NodePath} path
 */

/**
 * @param {PngNode} rootNode
 * @param {NodeUiFn} getNodeUi
 * @returns {DocumentFragment}
 */
export default (rootNode, getNodeUi) => {
  const [bytesRootEl, treeRootEl] = traverse(rootNode, [], getNodeUi);

  const outerBytesEl = crel("div", { class: "bytes" }, bytesRootEl);
  const outerTreeEl = crel("div", { class: "tree" }, treeRootEl);

  /** @type {null | HoveringOver} */
  let hoveringOver = null;

  const rerender = () => {
    /**
     * @callback IsActivatedFn
     * @param {NodePath} path
     * @returns {boolean}
     */
    /** @type {IsActivatedFn} */ let isByteElActivated;
    /** @type {IsActivatedFn} */ let isTreeElActivated;
    if (hoveringOver) {
      const hoveredPath = hoveringOver.path;
      switch (hoveringOver.side) {
        case "bytes":
          isByteElActivated = (path) => nodePath.isEqualTo(path, hoveredPath);
          isTreeElActivated = (path) =>
            nodePath.isSupersetOf(path, hoveredPath);
          break;
        case "tree":
          isByteElActivated = (path) =>
            nodePath.isSupersetOf(hoveredPath, path);
          isTreeElActivated = (path) => nodePath.isEqualTo(path, hoveredPath);
          break;
        default:
          throw new Error("Unexpected hovering over");
      }
    } else {
      isByteElActivated = isTreeElActivated = () => false;
    }

    for (const bytesEl of allChildrenOf(bytesRootEl)) {
      const path = elPath(bytesEl);
      if (path) {
        bytesEl.classList.toggle("activated", isByteElActivated(path));
      } else {
        throw new Error("Expected a path");
      }
    }
    for (const treeEl of allChildrenOf(treeRootEl)) {
      const path = elPath(treeEl);
      if (!path) continue;
      treeEl.classList.toggle("activated", isTreeElActivated(path));
    }
  };

  outerBytesEl.addEventListener("click", (event) => {
    if (!(event.target instanceof HTMLElement)) return;

    const rawPath = event.target?.dataset?.path;
    if (!rawPath) return;

    for (const explorerEl of allChildrenOf(outerTreeEl)) {
      if (explorerEl.dataset.path) explorerEl.removeAttribute("open");
    }

    const leafEl = outerTreeEl.querySelector(
      `details[data-path="${rawPath}"]`,
    );
    let currentTreeEl = leafEl;
    while (currentTreeEl && (currentTreeEl !== outerTreeEl)) {
      currentTreeEl.setAttribute("open", "open");
      currentTreeEl = currentTreeEl.parentElement;
    }
    leafEl?.scrollIntoView({ behavior: "smooth" });
  });

  outerBytesEl.addEventListener("mousemove", (event) => {
    if (!(event.target instanceof HTMLElement)) return;
    const path = elPath(event.target);
    if (!path) return;

    hoveringOver = { side: "bytes", path };
    rerender();
  });

  outerBytesEl.addEventListener("mouseout", (event) => {
    if (event.target !== outerBytesEl) return;

    if (hoveringOver?.side === "bytes") {
      hoveringOver = null;
      rerender();
    }
  });

  /** @param {UIEvent} event */
  const onFocusExplorerTree = (event) => {
    if (!(event.target instanceof HTMLElement)) return;

    // We don't update the state in these situations to avoid UI jitter.
    if (event.target.classList.contains("children")) return;

    /** @type {null | HTMLElement} */ let nodeToCheckForPath = event.target;
    while (nodeToCheckForPath && (nodeToCheckForPath !== outerTreeEl)) {
      if (nodeToCheckForPath.dataset.path) break;
      nodeToCheckForPath = nodeToCheckForPath.parentElement;
    }
    const path = nodeToCheckForPath && elPath(nodeToCheckForPath);
    if (!path) return;

    hoveringOver = { side: "tree", path };
    rerender();
  };
  /** @param {UIEvent} event */
  const onBlurExplorerTree = (event) => {
    if (
      (event.target !== outerTreeEl) &&
      (event.target !== outerTreeEl.children[0]) &&
      (hoveringOver?.side !== "tree")
    ) return;
    hoveringOver = null;
    rerender();
  };
  outerTreeEl.addEventListener("mousemove", onFocusExplorerTree);
  outerTreeEl.addEventListener("focusin", onFocusExplorerTree);
  outerTreeEl.addEventListener("mouseout", onBlurExplorerTree);
  outerTreeEl.addEventListener("focusout", onBlurExplorerTree);

  outerTreeEl.addEventListener("click", (event) => {
    if (!(event.target instanceof HTMLElement)) return;

    /** @type {null | HTMLElement} */ let nodeToCheckForPath = event.target;
    while (nodeToCheckForPath && (nodeToCheckForPath !== outerTreeEl)) {
      if (nodeToCheckForPath.dataset.path) break;
      nodeToCheckForPath = nodeToCheckForPath.parentElement;
    }
    const rawPath = nodeToCheckForPath?.dataset.path;
    if (!rawPath) return;

    const bytesEl = outerBytesEl.querySelector(`[data-path="${rawPath}"]`);
    bytesEl?.scrollIntoView({ behavior: "smooth" });
  });

  return fragment(outerBytesEl, outerTreeEl);
};

/**
 * @param {PngNode} node
 * @param {NodePath} path
 * @param {NodeUiFn} getNodeUi
 * @returns [HTMLElement, HTMLElement] Each node's bytes and tree elements.
 */
const traverse = (node, path, getNodeUi) => {
  const nodeBytesEl = crel("span", { "data-path": path });

  const isRoot = path.length === 0;
  const { title, description } = getNodeUi(node);
  const nodeTreeEl = crel(
    "details",
    { "data-path": path, ...(isRoot ? { open: "open" } : {}) },
    crel(
      "summary",
      {},
      crel("span", { "class": "title" }, title),
      crel(
        "span",
        { "class": "bytecount" },
        pluralize(node.bytes.byteLength, "byte"),
      ),
    ),
    description,
  );

  if (node.children) {
    const treeChildrenEl = crel("div", { class: "children" });
    node.children.forEach((child, index) => {
      const [childBytesEl, childTreeEl] = traverse(
        child,
        path.concat(index),
        getNodeUi,
      );
      if (index > 0) nodeBytesEl.append(" ");
      nodeBytesEl.append(childBytesEl);
      treeChildrenEl.append(childTreeEl);
    });
    nodeTreeEl.append(treeChildrenEl);
  } else {
    nodeBytesEl.innerHTML = formatBytes(node.bytes, 256);
  }

  return [nodeBytesEl, nodeTreeEl];
};

/**
 * @param {HTMLElement} el
 * @returns {null | NodePath}
 */
const elPath = (el) => nodePath.parse(el.dataset?.path);