import { Fragment, type ReactNode } from 'react';
import { Platform, type ViewStyle } from 'react-native';
import { Renderer, useMarkdown, type MarkedStyles } from 'react-native-marked';

// Shared markdown rendering for text and paper particles. Mirrors the desktop
// Crepe palette (markdown-editor.css `--crepe-*`) so a message reads the same
// on both surfaces: white-on-transparent text, a blue accent, pink inline
// code, and a near-opaque dark surface behind code blocks and tables.
//
// Known gap vs desktop: fenced code blocks aren't syntax-highlighted (Crepe
// uses CodeMirror; react-native-marked only exposes the language tag). They
// render as plain monospace on the dark surface, which is acceptable for v1.
const TEXT_COLOR = 'rgba(255,255,255,0.92)';
const ACCENT = '#60a5fa';
const SURFACE = 'rgba(24,24,28,0.96)';
const OUTLINE = 'rgba(255,255,255,0.2)';
const MONO = Platform.OS === 'ios' ? 'Menlo' : 'monospace';

// react-native-marked doesn't render GFM task-list checkboxes (marked strips
// the `[ ]`/`[x]` into token flags the parser ignores), so a write/read drift
// shows up as bullets with no box. Swap the marker for a checkbox glyph before
// parsing — read-only, matching desktop's bullet-free checkboxes.
const TASK_ITEM_RE = /^(\s*)[-*+] \[([ xX])\] /gm;

function withTaskCheckboxes(markdown: string): string {
  return markdown.replace(
    TASK_ITEM_RE,
    (_match, indent: string, mark: string) =>
      `${indent}${mark === ' ' ? '☐' : '☑'} `,
  );
}

const MARKDOWN_THEME = {
  colors: {
    text: TEXT_COLOR,
    link: ACCENT,
    code: SURFACE,
    border: OUTLINE,
  },
};

const MARKDOWN_STYLES: MarkedStyles = {
  text: { color: TEXT_COLOR, fontSize: 18, lineHeight: 28 },
  li: { color: TEXT_COLOR, fontSize: 18, lineHeight: 28 },
  strong: { fontWeight: '700' },
  em: { fontStyle: 'italic' },
  strikethrough: {
    textDecorationLine: 'line-through',
    color: 'rgba(255,255,255,0.6)',
  },
  // fontStyle "normal" cancels react-native-marked's italic-by-default for
  // links and inline code (desktop renders neither italic).
  link: { color: ACCENT, fontStyle: 'normal' },
  // borderBottomWidth 0 removes the library's default heading underline rule,
  // which desktop's headings don't have.
  h1: {
    color: '#ffffff',
    fontSize: 28,
    lineHeight: 34,
    fontWeight: '700',
    marginTop: 8,
    marginBottom: 8,
    borderBottomWidth: 0,
  },
  h2: {
    color: '#ffffff',
    fontSize: 24,
    lineHeight: 30,
    fontWeight: '700',
    marginTop: 8,
    marginBottom: 6,
    borderBottomWidth: 0,
  },
  h3: {
    color: '#ffffff',
    fontSize: 20,
    lineHeight: 26,
    fontWeight: '600',
    marginTop: 6,
    marginBottom: 4,
  },
  h4: {
    color: '#ffffff',
    fontSize: 18,
    lineHeight: 24,
    fontWeight: '600',
    marginTop: 6,
    marginBottom: 4,
  },
  h5: {
    color: '#ffffff',
    fontSize: 16,
    lineHeight: 22,
    fontWeight: '600',
    marginTop: 4,
    marginBottom: 2,
  },
  h6: {
    color: 'rgba(255,255,255,0.7)',
    fontSize: 15,
    lineHeight: 20,
    fontWeight: '600',
    marginTop: 4,
    marginBottom: 2,
  },
  codespan: {
    color: '#fca5a5',
    fontFamily: MONO,
    fontStyle: 'normal',
    backgroundColor: 'rgba(255,255,255,0.1)',
  },
  code: {
    backgroundColor: SURFACE,
    borderColor: OUTLINE,
    borderWidth: 1,
    borderRadius: 8,
    padding: 12,
    marginVertical: 6,
  },
  blockquote: {
    borderLeftWidth: 3,
    borderLeftColor: OUTLINE,
    paddingLeft: 12,
    marginVertical: 6,
    opacity: 0.85,
  },
  // hr is left to the library default, which already draws a 1px rule in the
  // themed border color (OUTLINE).
  table: { borderWidth: 1, borderColor: OUTLINE, marginVertical: 6 },
  tableRow: { borderColor: OUTLINE },
  tableCell: { borderColor: OUTLINE, padding: 8 },
};

// react-native-marked feeds fenced code blocks the `em` (italic, proportional)
// text style, so out of the box code renders italic in the body font. Override
// `code` to apply a monospace, non-italic style instead — matching desktop's
// code blocks.
const CODE_TEXT_STYLE = {
  color: TEXT_COLOR,
  fontFamily: MONO,
  fontSize: 15,
  lineHeight: 22,
};

class MarkdownRenderer extends Renderer {
  code(text: string, language?: string, containerStyle?: ViewStyle): ReactNode {
    return super.code(text, language, containerStyle, CODE_TEXT_STYLE);
  }
}

const MARKDOWN_RENDERER = new MarkdownRenderer();

/**
 * Renders GFM markdown using the shared Flowy palette. `useMarkdown` returns an
 * array of block nodes; we splat them into a Fragment so they nest cleanly
 * inside a parent ScrollView (vs. the library's own FlatList-based component).
 */
export function MarkdownBody({ content }: { content: string }) {
  const nodes = useMarkdown(withTaskCheckboxes(content), {
    renderer: MARKDOWN_RENDERER,
    theme: MARKDOWN_THEME,
    styles: MARKDOWN_STYLES,
  });
  return <Fragment>{nodes}</Fragment>;
}
