import { useEffect } from 'react';
import { EditorContent, useEditor, type Editor } from '@tiptap/react';
import StarterKit from '@tiptap/starter-kit';
import Link from '@tiptap/extension-link';
import TextAlign from '@tiptap/extension-text-align';
import {
  AlignCenter,
  AlignJustify,
  AlignLeft,
  AlignRight,
  Bold,
  Heading2,
  Italic,
  Link2,
  List,
  ListOrdered,
  Redo2,
  Strikethrough,
  Undo2,
} from 'lucide-react';

/**
 * The editor for the site's copy.
 *
 * ── Why HTML in and HTML out ──
 *
 * `intro_text` and the rest are already HTML in the site's database, written by the old admin and
 * rendered straight into the page. So the editor's job is to read that and give it back — not to
 * introduce a second format with a conversion at each end, which is a migration and a class of bug
 * (round-tripping) bought for nothing.
 *
 * ── The toolbar is what the site can actually render ──
 *
 * Bold, italic, strike, a heading, two lists, four alignments, a link. Not because tiptap cannot do
 * more, but because anything offered here that the site's stylesheet has no rule for produces copy that
 * looks right while editing and wrong when published — the worst kind of editor, since the person only
 * finds out after saying it is done.
 *
 * ── Uncontrolled after the first render, deliberately ──
 *
 * tiptap owns its own document. Pushing `value` in on every render would move the caret to the end
 * mid-sentence, which is the classic controlled-contentEditable bug. So the parent's value seeds it,
 * and after that the editor is the source of truth until it is unmounted or the value changes from
 * somewhere that is not typing — see the effect below.
 */

const Tool = ({
  onClick,
  active,
  disabled,
  label,
  children,
}: {
  onClick: () => void;
  active?: boolean;
  disabled?: boolean;
  label: string;
  children: React.ReactNode;
}) => (
  <button
    type="button"
    onMouseDown={(event) => {
      // The editor loses focus on mousedown otherwise, and a command applied with no selection does
      // nothing — which reads as a dead button.
      event.preventDefault();
      onClick();
    }}
    disabled={disabled}
    aria-label={label}
    title={label}
    className={`rounded p-1.5 transition-colors disabled:opacity-40 ${
      active ? 'bg-primary/20 text-primary' : 'text-muted-foreground hover:bg-muted hover:text-foreground'
    }`}
  >
    {children}
  </button>
);

/**
 * The alignments the toolbar offers.
 *
 * The same four the site's sanitiser accepts — ALIGN_CLASSES in src/rich-text.ts. A fifth offered here
 * would be stripped on save, silently, leaving somebody pressing a button that appears to do nothing.
 */
const ALIGNMENTS = [
  { value: 'left' as const, Icon: AlignLeft },
  { value: 'center' as const, Icon: AlignCenter },
  { value: 'right' as const, Icon: AlignRight },
  { value: 'justify' as const, Icon: AlignJustify },
];

const Toolbar = ({ editor }: { editor: Editor }) => (
  <div className="flex flex-wrap items-center gap-0.5 border-b border-border px-1 py-1">
    <Tool label="Bold" onClick={() => editor.chain().focus().toggleBold().run()} active={editor.isActive('bold')}>
      <Bold className="size-3.5" />
    </Tool>
    <Tool label="Italic" onClick={() => editor.chain().focus().toggleItalic().run()} active={editor.isActive('italic')}>
      <Italic className="size-3.5" />
    </Tool>
    <Tool
      label="Strikethrough"
      onClick={() => editor.chain().focus().toggleStrike().run()}
      active={editor.isActive('strike')}
    >
      <Strikethrough className="size-3.5" />
    </Tool>

    <span className="mx-1 h-4 w-px bg-border" />

    <Tool
      label="Heading"
      onClick={() => editor.chain().focus().toggleHeading({ level: 2 }).run()}
      active={editor.isActive('heading', { level: 2 })}
    >
      <Heading2 className="size-3.5" />
    </Tool>
    <Tool
      label="Bulleted list"
      onClick={() => editor.chain().focus().toggleBulletList().run()}
      active={editor.isActive('bulletList')}
    >
      <List className="size-3.5" />
    </Tool>
    <Tool
      label="Numbered list"
      onClick={() => editor.chain().focus().toggleOrderedList().run()}
      active={editor.isActive('orderedList')}
    >
      <ListOrdered className="size-3.5" />
    </Tool>

    <span className="mx-1 h-4 w-px bg-border" />

    {/*
      Four alignments, justify included.

      The site has always been able to render it: `rt-justify` is in the sanitiser's allowlist and
      styles.css gives it `text-align: justify` with `hyphens: auto` — hyphenation being what stops
      justified text opening rivers of white space between words. Only the toolbar was missing.
    */}
    {ALIGNMENTS.map(({ value, Icon }) => (
      <Tool
        key={value}
        label={`Align ${value}`}
        onClick={() => editor.chain().focus().setTextAlign(value).run()}
        active={editor.isActive({ textAlign: value })}
      >
        <Icon className="size-3.5" />
      </Tool>
    ))}

    <span className="mx-1 h-4 w-px bg-border" />

    <Tool
      label="Link"
      active={editor.isActive('link')}
      onClick={() => {
        if (editor.isActive('link')) {
          editor.chain().focus().unsetLink().run();
          return;
        }
        // `prompt` rather than a dialog: it is one string, it is modal either way, and a bespoke
        // dialog here would be a component to maintain for a field with no validation worth doing.
        const href = window.prompt('Link to');
        if (href) editor.chain().focus().setLink({ href }).run();
      }}
    >
      <Link2 className="size-3.5" />
    </Tool>

    <span className="ml-auto flex items-center gap-0.5">
      <Tool label="Undo" onClick={() => editor.chain().focus().undo().run()} disabled={!editor.can().undo()}>
        <Undo2 className="size-3.5" />
      </Tool>
      <Tool label="Redo" onClick={() => editor.chain().focus().redo().run()} disabled={!editor.can().redo()}>
        <Redo2 className="size-3.5" />
      </Tool>
    </span>
  </div>
);

/**
 * Stored alignment classes, back into the inline styles tiptap understands.
 *
 * ── The round trip was LOSSY, and this is the half that was missing ──
 *
 * The editor emits `style="text-align: right"`. The site's sanitiser refuses style attributes — one is
 * a way to position something over the rest of the page — and converts alignment to `class="rt-right"`
 * on the way in. That half has always worked.
 *
 * Coming back out, tiptap parses styles and knows nothing about those classes. So a document loaded
 * from the database arrived with every alignment gone, and the next save wrote that loss back. Editing
 * one paragraph silently un-aligned the others: a right-aligned line lost its alignment because
 * somebody justified something else.
 *
 * Converting here makes the two ends symmetric — class in, style out, style in, class out — and the
 * conversion is the sanitiser's own table read backwards.
 *
 * `rt-font-*` is NOT converted, and that is a known gap rather than an oversight: this editor has no
 * font control, so a stored font class has nothing to become and would be dropped either way. It wants
 * a font button before it wants a parser.
 */
const ALIGNMENT_CLASS = /class="rt-(left|center|right|justify)"/g;

const toEditorHtml = (html: string): string =>
  html.replace(ALIGNMENT_CLASS, (_whole, align: string) => `style="text-align: ${align}"`);

export const RichText = ({
  value,
  onChange,
  placeholder,
}: {
  value: string;
  onChange: (html: string) => void;
  placeholder?: string;
}) => {
  const editor = useEditor({
    extensions: [
      StarterKit,
      TextAlign.configure({ types: ['heading', 'paragraph'] }),
      // `openOnClick: false` — inside an editor a click is a cursor, not navigation. Without it,
      // clicking a link to edit its text opens it and loses whatever was unsaved.
      Link.configure({ openOnClick: false }),
    ],
    content: toEditorHtml(value),
    editorProps: {
      attributes: {
        class:
          'prose prose-sm prose-invert max-w-none min-h-40 px-3 py-2 focus:outline-none [&_a]:text-primary [&_a]:underline',
      },
    },
    onUpdate: ({ editor: current }) => onChange(current.getHTML()),
  });

  /*
    Only when the value changes from somewhere that is NOT this editor.

    Comparing against `getHTML()` first is what makes that distinction: while somebody types, the two
    already agree, so nothing is written back and the caret stays where it is. When a save returns the
    server's version — or the panel loads a different record — they differ, and the document is
    replaced. Without the comparison this is the classic controlled-contentEditable bug: the caret
    jumps to the end on every keystroke.
  */
  useEffect(() => {
    if (!editor) return;
    // Compared in the EDITOR's dialect, or every load looks like a change: the stored html says
    // `class="rt-right"` and getHTML() says `style="text-align: right"`, which never match.
    const incoming = toEditorHtml(value);
    if (incoming !== editor.getHTML()) editor.commands.setContent(incoming, { emitUpdate: false });
  }, [editor, value]);

  if (!editor) return null;

  return (
    <div className="overflow-hidden rounded-md border border-border bg-background">
      <Toolbar editor={editor} />
      <EditorContent editor={editor} />
      {!value && placeholder && (
        <p className="pointer-events-none -mt-9 px-3 text-xs text-muted-foreground/50">{placeholder}</p>
      )}
    </div>
  );
};