import { Fragment, Node as PMNode } from 'prosemirror-model';

/** email-fidelity: writes the editor's data-table rendering into the saved HTML; layout tables keep their authored output. */

/** Theme-resolved colours the editor draws data tables with; null = not drawn. */
export interface EmailRenderDefaults {
  borderColor: string | null;
  headerBackground: string | null;
}

/** Kept in sync by hand with `.ProseMirror td, .ProseMirror th { padding: 6px 8px }`. */
const CELL_PADDING: Record<string, string> = {
  paddingTop: '6px',
  paddingRight: '8px',
  paddingBottom: '6px',
  paddingLeft: '8px',
};

const CELL_BORDERS = ['borderTop', 'borderRight', 'borderBottom', 'borderLeft'];

/** `.ProseMirror td > *` zeroes block margins inside cells. */
const CELL_CHILD_MARGIN = 'margin-top: 0px; margin-bottom: 0px';

type Context = 'data-table' | 'data-cell' | null;

/** Returns a copy of `doc` with the editor's data-table rendering filled into node attrs. */
export function applyEmailRenderDefaults(doc: PMNode, defaults: EmailRenderDefaults): PMNode {
  return fill(doc, null, defaults);
}

function fill(node: PMNode, context: Context, defaults: EmailRenderDefaults): PMNode {
  if (node.isLeaf) return node;
  const name = node.type.name;
  let attrs = node.attrs;
  let childContext: Context = null;

  if (name === 'table') {
    if (!attrs.layout) {
      childContext = 'data-table';
      if (!attrs.width) attrs = { ...attrs, width: '100%' };
    }
  } else if (name === 'table_row') {
    childContext = context;
  } else if ((name === 'table_cell' || name === 'table_header') && context === 'data-table') {
    attrs = cellDefaults(attrs, name === 'table_header', defaults);
    childContext = 'data-cell';
  } else if (context === 'data-cell' && 'margin' in attrs && !attrs.margin) {
    attrs = { ...attrs, margin: CELL_CHILD_MARGIN };
  }

  const children: PMNode[] = [];
  node.forEach(child => children.push(fill(child, childContext, defaults)));
  return node.type.create(attrs, Fragment.fromArray(children), node.marks);
}

function cellDefaults(
  attrs: Record<string, any>,
  header: boolean,
  defaults: EmailRenderDefaults
): Record<string, any> {
  const next = { ...attrs };
  for (const [key, value] of Object.entries(CELL_PADDING)) if (!next[key]) next[key] = value;
  if (!next.valign) next.valign = 'top';
  if (defaults.borderColor) {
    const border = `1px solid ${defaults.borderColor}`;
    for (const key of CELL_BORDERS) if (!next[key]) next[key] = border;
  }
  // A resized column keeps its width in data-colwidth, which mail clients ignore.
  const colwidth = next.colwidth as number[] | null;
  if (!next.width && Array.isArray(colwidth) && colwidth.length && colwidth.every(w => w > 0)) {
    next.width = `${colwidth.reduce((sum, w) => sum + w, 0)}px`;
  }
  if (header) {
    if (!next.background && defaults.headerBackground) next.background = defaults.headerBackground;
    if (!next.textAlign) next.textAlign = 'left';
    const textStyle = (next.textStyle as string | null) ?? '';
    if (!/font-weight/i.test(textStyle)) {
      next.textStyle = textStyle ? `${textStyle}; font-weight: 600` : 'font-weight: 600';
    }
  }
  return next;
}

/** Collapsed borders and no cell spacing on every table, fixed columns on data tables. */
export function finishEmailTables(container: HTMLElement): void {
  for (const table of Array.from(container.querySelectorAll('table'))) {
    if (!table.hasAttribute('cellpadding')) table.setAttribute('cellpadding', '0');
    if (!table.hasAttribute('cellspacing')) table.setAttribute('cellspacing', '0');
    const style = table.getAttribute('style') ?? '';
    const add: string[] = [];
    if (!/(^|;)\s*border-collapse\s*:/i.test(style)) add.push('border-collapse: collapse');
    const layout = table.getAttribute('role') === 'presentation';
    if (!layout && !/(^|;)\s*table-layout\s*:/i.test(style)) add.push('table-layout: fixed');
    if (add.length) {
      const base = style.trim().replace(/;\s*$/, '');
      table.setAttribute('style', base ? `${base}; ${add.join('; ')}` : add.join('; '));
    }
  }
}