"use client";

import { useEffect, useMemo, useRef, useState } from "react";
import {
  categoryOptionLabel,
  type MeshkeeEntityCategory,
} from "@/services/meshkee-catalog";
import styles from "./CatalogCategorySelect.module.css";

type TreeNode = MeshkeeEntityCategory & { children: TreeNode[] };

function buildTree(categories: MeshkeeEntityCategory[]): TreeNode[] {
  const byId = new Map<string, TreeNode>();
  for (const category of categories) {
    byId.set(category.id, { ...category, children: [] });
  }

  const roots: TreeNode[] = [];
  for (const node of byId.values()) {
    if (node.parentId && byId.has(node.parentId)) {
      byId.get(node.parentId)!.children.push(node);
    } else {
      roots.push(node);
    }
  }

  const sortNodes = (nodes: TreeNode[]) => {
    nodes.sort((a, b) =>
      categoryOptionLabel(a).localeCompare(categoryOptionLabel(b), undefined, {
        sensitivity: "base",
      }),
    );
    for (const node of nodes) sortNodes(node.children);
  };
  sortNodes(roots);
  return roots;
}

function matchesQuery(category: MeshkeeEntityCategory, q: string) {
  if (!q) return true;
  const hay = [category.name, category.nameFa ?? "", category.description ?? ""]
    .join(" ")
    .toLowerCase();
  return hay.includes(q);
}

function filterTree(nodes: TreeNode[], q: string): TreeNode[] {
  if (!q) return nodes;
  const result: TreeNode[] = [];
  for (const node of nodes) {
    const children = filterTree(node.children, q);
    if (matchesQuery(node, q) || children.length) {
      result.push({ ...node, children });
    }
  }
  return result;
}

function collectExpandIds(nodes: TreeNode[], into: Set<string>) {
  for (const node of nodes) {
    if (node.children.length) {
      into.add(node.id);
      collectExpandIds(node.children, into);
    }
  }
}

export default function CatalogCategorySelect({
  categories,
  value,
  onChange,
  disabled = false,
  label = "Category",
  optional = false,
  placeholder = "Select category",
}: {
  categories: MeshkeeEntityCategory[];
  value: string;
  onChange: (id: string) => void;
  disabled?: boolean;
  label?: string;
  optional?: boolean;
  placeholder?: string;
}) {
  const rootRef = useRef<HTMLDivElement>(null);
  const [open, setOpen] = useState(false);
  const [query, setQuery] = useState("");
  const [expanded, setExpanded] = useState<Set<string>>(() => new Set());

  const tree = useMemo(() => buildTree(categories), [categories]);
  const q = query.trim().toLowerCase();
  const visibleTree = useMemo(() => filterTree(tree, q), [tree, q]);

  const selected = useMemo(
    () => categories.find((item) => item.id === value) ?? null,
    [categories, value],
  );

  useEffect(() => {
    if (!q) return;
    const next = new Set<string>();
    collectExpandIds(visibleTree, next);
    setExpanded(next);
  }, [q, visibleTree]);

  useEffect(() => {
    if (!open) return;
    function onPointerDown(event: MouseEvent) {
      if (!rootRef.current?.contains(event.target as Node)) {
        setOpen(false);
        setQuery("");
      }
    }
    function onKey(event: KeyboardEvent) {
      if (event.key === "Escape") {
        setOpen(false);
        setQuery("");
      }
    }
    document.addEventListener("mousedown", onPointerDown);
    document.addEventListener("keydown", onKey);
    return () => {
      document.removeEventListener("mousedown", onPointerDown);
      document.removeEventListener("keydown", onKey);
    };
  }, [open]);

  function select(id: string) {
    onChange(id);
    setOpen(false);
    setQuery("");
  }

  function toggleExpand(id: string) {
    setExpanded((prev) => {
      const next = new Set(prev);
      if (next.has(id)) next.delete(id);
      else next.add(id);
      return next;
    });
  }

  function renderNodes(nodes: TreeNode[], depth: number) {
    return nodes.map((node) => {
      const hasChildren = node.children.length > 0;
      const isExpanded = q ? true : expanded.has(node.id);
      const active = value === node.id;

      return (
        <li key={node.id} className={styles.node}>
          <div
            className={`${styles.row}${active ? ` ${styles.rowActive}` : ""}`}
            style={{ paddingInlineStart: `${10 + depth * 18}px` }}
          >
            {hasChildren ? (
              <button
                type="button"
                className={`${styles.expand} ${isExpanded ? styles.expandOpen : ""}`}
                aria-label={isExpanded ? "Collapse" : "Expand"}
                tabIndex={-1}
                onClick={() => toggleExpand(node.id)}
              >
                <span aria-hidden>{isExpanded ? "−" : "+"}</span>
              </button>
            ) : (
              <span
                className={`${styles.expandSpacer}${depth > 0 ? ` ${styles.leafMark}` : ""}`}
                aria-hidden
              />
            )}
            <button
              type="button"
              className={styles.option}
              disabled={disabled}
              onClick={() => select(node.id)}
            >
              <span className={styles.optionLabel} dir="auto">
                {categoryOptionLabel(node)}
              </span>
            </button>
          </div>
          {hasChildren && isExpanded ? (
            <ul className={styles.branch}>{renderNodes(node.children, depth + 1)}</ul>
          ) : null}
        </li>
      );
    });
  }

  return (
    <div className={styles.root} ref={rootRef}>
      <span className={styles.label}>
        {label}
        {optional ? (
          <em className={styles.optional}> (optional)</em>
        ) : null}
      </span>
      <div className={styles.control}>
        <input
          value={open ? query : selected ? categoryOptionLabel(selected) : ""}
          disabled={disabled}
          placeholder={placeholder}
          aria-expanded={open}
          aria-haspopup="listbox"
          onFocus={() => {
            setOpen(true);
            setQuery("");
          }}
          onChange={(event) => {
            setQuery(event.target.value);
            setOpen(true);
          }}
          onClick={() => setOpen(true)}
        />
        <button
          type="button"
          className={`${styles.caret} ${open ? styles.caretOpen : ""}`}
          aria-label={open ? "Close categories" : "Open categories"}
          disabled={disabled}
          onClick={() => {
            setOpen((prev) => !prev);
            setQuery("");
          }}
        />
      </div>

      {open ? (
        <div className={styles.dropdown} role="listbox">
          {optional ? (
            <button
              type="button"
              className={`${styles.clearOption}${!value ? ` ${styles.rowActive}` : ""}`}
              disabled={disabled}
              onClick={() => select("")}
            >
              No category
            </button>
          ) : null}
          {visibleTree.length ? (
            <ul className={styles.list}>{renderNodes(visibleTree, 0)}</ul>
          ) : (
            <p className={styles.empty}>No categories found</p>
          )}
        </div>
      ) : null}
    </div>
  );
}