plainleaf/client/markdown_renderer/markdown_render.ts

import {
  addParentPointers,
  collectNodesOfType,
  findNodeOfType,
  normalizeTableRow,
  type ParseTree,
  removeParentPointers,
  renderToText,
  traverseTree,
} from "@silverbulletmd/silverbullet/lib/tree";
import {
  encodePageURI,
  encodeRef,
  parseToRef,
} from "@silverbulletmd/silverbullet/lib/ref";
import { Fragment, renderHtml, type Tag } from "./html_render.ts";
import * as TagConstants from "../../plugs/index/constants.ts";
import { extractHashtag } from "@silverbulletmd/silverbullet/lib/tags";
import { justifiedTableRender } from "./justified_tables.ts";
import type { PageMeta } from "@silverbulletmd/silverbullet/type/index";
import { createMediaElement } from "./inline.ts";
import { parseTransclusion } from "@silverbulletmd/silverbullet/lib/transclusion";

export type MarkdownRenderOptions = {
  failOnUnknown?: true;
  smartHardBreak?: true;
  annotationPositions?: true;
  shortWikiLinks?: boolean;
  // When defined, use to inline images as data: urls
  translateUrls?: (url: string, type: "link" | "image") => string;
  expand?: true;
};

function cleanTags(values: (Tag | null)[], cleanWhitespace = false): Tag[] {
  const result: Tag[] = [];
  for (const value of values) {
    if (cleanWhitespace && typeof value === "string" && value.match(/^\s+$/)) {
      continue;
    }
    if (value) {
      result.push(value);
    }
  }
  return result;
}

/**
 * Cleans up a markdown tree. Side effect: adds parent pointers
 */
function preprocess(t: ParseTree) {
  addParentPointers(t);
  traverseTree(t, (node) => {
    if (!node.type) {
      // Remove redundant newlines in table
      if (node.text?.startsWith("\n")) {
        const prevNodeIdx = node.parent!.children!.indexOf(node) - 1;
        const prevNodeType = node.parent!.children![prevNodeIdx]?.type;
        if (
          prevNodeType?.includes("Heading") ||
          prevNodeType?.includes("Table")
        ) {
          node.text = node.text.slice(1);
        }
      }
    }
    return false;
  });
}

function posPreservingRender(
  t: ParseTree,
  options: MarkdownRenderOptions = {},
): Tag | null {
  const tag = render(t, options);
  if (!options.annotationPositions) {
    return tag;
  }
  if (!tag) {
    return null;
  }
  if (typeof tag === "string") {
    return tag;
  }
  if (t.from) {
    if (!tag.attrs) {
      tag.attrs = {};
    }
    tag.attrs["data-pos"] = `${t.from}`;
  }
  return tag;
}

function render(t: ParseTree, options: MarkdownRenderOptions = {}): Tag | null {
  if (t.type?.endsWith("Mark") || t.type?.endsWith("Delimiter")) {
    return null;
  }
  switch (t.type) {
    case "Document":
      return {
        name: Fragment,
        body: cleanTags(mapRender(t.children!)),
      };
    case "FrontMatter":
      return null;
    case "CommentBlock":
      // Remove, for now
      return null;
    case "ATXHeading1":
      return {
        name: "h1",
        body: cleanTags(mapRender(t.children!)),
      };
    case "ATXHeading2":
      return {
        name: "h2",
        body: cleanTags(mapRender(t.children!)),
      };
    case "ATXHeading3":
      return {
        name: "h3",
        body: cleanTags(mapRender(t.children!)),
      };
    case "ATXHeading4":
      return {
        name: "h4",
        body: cleanTags(mapRender(t.children!)),
      };
    case "ATXHeading5":
      return {
        name: "h5",
        body: cleanTags(mapRender(t.children!)),
      };
    case "ATXHeading6":
      return {
        name: "h6",
        body: cleanTags(mapRender(t.children!)),
      };
    case "Paragraph":
      return {
        name: "span",
        attrs: {
          class: "p",
        },
        body: cleanTags(mapRender(t.children!)),
      };
    // Code blocks
    case "FencedCode":
    case "CodeBlock": {
      // Clear out top-level indent blocks
      const lang = findNodeOfType(t, "CodeInfo");
      t.children = t.children!.filter((c) => c.type);
      return {
        name: "pre",
        attrs: {
          "data-lang": lang ? lang.children![0].text : undefined,
        },
        body: cleanTags(mapRender(t.children!)),
      };
    }
    case "CodeInfo":
      return null;
    case "CodeText":
      return t.children![0].text!;
    case "Blockquote":
      return {
        name: "blockquote",
        body: cleanTags(mapRender(t.children!)),
      };
    case "HardBreak":
      return {
        name: "br",
        body: "",
      };
    // Basic styling
    case "Emphasis":
      return {
        name: "em",
        body: cleanTags(mapRender(t.children!)),
      };
    case "Highlight":
      return {
        name: "span",
        attrs: {
          class: "highlight",
        },
        body: cleanTags(mapRender(t.children!)),
      };
    case "Strikethrough":
      return {
        name: "del",
        body: cleanTags(mapRender(t.children!)),
      };
    case "InlineCode":
      return {
        name: "code",
        attrs: {
          class: "sb-code",
        },
        body: cleanTags(mapRender(t.children!)),
      };
    case "BulletList":
      return {
        name: "ul",
        body: cleanTags(mapRender(t.children!), true),
      };
    case "OrderedList":
      return {
        name: "ol",
        body: cleanTags(mapRender(t.children!), true),
      };
    case "ListItem":
      return {
        name: "li",
        body: cleanTags(mapRender(t.children!), true),
      };
    case "StrongEmphasis":
      return {
        name: "strong",
        body: cleanTags(mapRender(t.children!)),
      };
    case "HorizontalRule":
      return {
        name: "hr",
        body: "",
      };
    case "Link": {
      const linkTextChildren = t.children!.slice(1, -4);
      const urlNode = findNodeOfType(t, "URL");
      if (!urlNode) {
        return renderToText(t);
      }
      return {
        name: "a",
        attrs: {
          href: urlNode.children![0].text!,
          target: "_blank",
        },
        body: cleanTags(mapRender(linkTextChildren)),
      };
    }
    case "Autolink": {
      const urlNode = findNodeOfType(t, "URL");
      if (!urlNode) {
        return renderToText(t);
      }
      const url = urlNode.children![0].text!;
      return {
        name: "a",
        attrs: {
          href: url,
          target: "_blank",
        },
        body: url,
      };
    }
    case "Image": {
      const text = renderToText(t);

      const transclusion = parseTransclusion(text);
      if (!transclusion) {
        return text;
      }

      try {
        const element = createMediaElement(transclusion);
        if (!element) {
          return text;
        }

        return {
          name: element.tagName,
          attrs: Array.from(element.attributes).reduce(
            (obj, attr) => {
              obj[attr.name] = attr.value;
              return obj;
            },
            {} as Record<string, string>,
          ),
          body: "",
        };
      } catch (e: any) {
        console.error("Error handling image or transclusion", e.message);
        return {
          name: "span",
          body: "Error loading image",
        };
      }
    }

    // Custom stuff
    case "WikiLink": {
      const link = findNodeOfType(t, "WikiLinkPage")!.children![0].text!;
      let linkText =
        options.shortWikiLinks === true ? link.split("/").pop()! : link;
      const aliasNode = findNodeOfType(t, "WikiLinkAlias");
      if (aliasNode) {
        linkText = aliasNode.children![0].text!;
      }

      // For invalid refs the link just won't link
      let href: string = `#`;

      const ref = parseToRef(link);
      if (ref) {
        href = `/${encodePageURI(encodeRef(ref))}`;
      }

      return {
        name: "a",
        attrs: {
          href,
          class: "wiki-link",
          "data-ref": link,
        },
        body: linkText,
      };
    }
    case "NakedURL": {
      const url = t.children![0].text!;
      return {
        name: "a",
        attrs: {
          href: url,
          target: "_blank",
        },
        body: url,
      };
    }
    case "Hashtag": {
      const tagText: string = t.children![0].text!;
      const link = TagConstants.tagPrefix + extractHashtag(tagText);
      return {
        name: "a",
        attrs: {
          class: "hashtag sb-hashtag",
          "data-tag-name": extractHashtag(tagText),
          href: `/${encodePageURI(link)}`,
          "data-ref": link,
        },
        body: tagText,
      };
    }
    case "Task": {
      let externalTaskRef = "";
      collectNodesOfType(t, "WikiLinkPage").forEach((wikilink) => {
        const ref = parseToRef(wikilink.children![0].text!);

        if (
          !externalTaskRef &&
          ref &&
          (ref.details?.type === "position" ||
            ref.details?.type === "linecolumn")
        ) {
          externalTaskRef = wikilink.children![0].text!;
        }
      });

      return {
        name: "span",
        attrs: externalTaskRef
          ? {
              "data-external-task-ref": externalTaskRef,
            }
          : {},
        body: cleanTags(mapRender(t.children!)),
      };
    }
    case "TaskState": {
      // child[0] = marker, child[1] = state, child[2] = marker
      const stateText = t.children![1].text!;
      if ([" ", "x", "X"].includes(stateText)) {
        return {
          name: "input",
          attrs: {
            type: "checkbox",
            checked: stateText !== " " ? "checked" : undefined,
            "data-state": stateText,
          },
          body: "",
        };
      }
      return {
        name: Fragment,
        body: [
          { name: "span", attrs: { class: "sb-task-mark" }, body: "[" },
          {
            name: "span",
            attrs: { class: "sb-task-state", "data-state": stateText },
            body: stateText,
          },
          { name: "span", attrs: { class: "sb-task-mark" }, body: "]" },
        ],
      };
    }

    // Tables
    case "Table":
      return {
        name: "table",
        body: justifiedTableRender(cleanTags(mapRender(t.children!)), t),
      };
    case "TableHeader":
      return {
        name: "thead",
        body: [
          {
            name: "tr",
            body: cleanTags(mapRender(t.children!), true),
          },
        ],
      };
    case "TableCell":
      return {
        name: "td",
        body: cleanTags(mapRender(t.children!)),
      };
    case "TableRow": {
      const table = t.parent;
      const header = table?.children?.find((c) => c.type === "TableHeader");
      let columnCount = 0;
      let headerHasLeadingDelim: boolean | undefined;
      if (header) {
        normalizeTableRow(header);
        headerHasLeadingDelim = header.children?.[0]?.type === "TableDelimiter";
        for (const c of header.children ?? []) {
          if (c.type === "TableCell") columnCount++;
        }
      }
      normalizeTableRow(t, columnCount, headerHasLeadingDelim);
      return {
        name: "tr",
        body: cleanTags(mapRender(t.children!), true),
      };
    }
    case "Attribute": {
      const nameNode = findNodeOfType(t, "AttributeName");
      const valueNode = findNodeOfType(t, "AttributeValue");
      const colonNode = findNodeOfType(t, "AttributeColon");
      const attrName = nameNode?.children?.[0].text ?? "";
      const attrValue = valueNode?.children?.[0].text ?? "";
      const attrColon = colonNode?.children?.[0].text ?? ": ";
      return {
        name: "span",
        attrs: {
          class: "sb-attribute",
          ...(attrName ? { [`data-${attrName}`]: attrValue } : {}),
        },
        body: [
          {
            name: "span",
            attrs: { class: "sb-frontmatter sb-meta" },
            body: "[",
          },
          {
            name: "span",
            attrs: { class: "sb-frontmatter sb-attribute-name" },
            body: attrName,
          },
          {
            name: "span",
            attrs: { class: "sb-frontmatter sb-meta" },
            body: attrColon,
          },
          {
            name: "span",
            attrs: { class: "sb-frontmatter sb-attribute-value" },
            body: attrValue,
          },
          {
            name: "span",
            attrs: { class: "sb-frontmatter sb-meta" },
            body: "]",
          },
        ],
      };
    }
    case "Escape": {
      return {
        name: "span",
        attrs: {
          class: "escape",
        },
        body: t.children![0].text!.slice(1),
      };
    }
    case "Entity":
      return t.children![0].text!;

    case "Superscript":
      return {
        name: "sup",
        body: cleanTags(mapRender(t.children!)),
      };
    case "Subscript":
      return {
        name: "sub",
        body: cleanTags(mapRender(t.children!)),
      };
    case "FootnoteRef": {
      const label = findNodeOfType(t, "FootnoteRefLabel")!.children![0].text!;
      return {
        name: "sup",
        attrs: {
          class: "sb-rendered-footnote-ref",
        },
        body: label,
      };
    }
    case "FootnoteDefinition": {
      const label = findNodeOfType(t, "FootnoteDefLabel")!.children![0].text!;
      const body = findNodeOfType(t, "FootnoteDefBody");
      return {
        name: "div",
        attrs: {
          class: "sb-rendered-footnote-def",
          id: `fn-${label}`,
        },
        body: [
          {
            name: "span",
            attrs: { class: "sb-rendered-footnote-def-label" },
            body: `${label}. `,
          },
          ...(body ? cleanTags(mapRender(body.children!)) : []),
        ],
      };
    }
    case "FootnoteDefBody":
      return {
        name: Fragment,
        body: cleanTags(mapRender(t.children!)),
      };
    case "InlineFootnote": {
      const content = findNodeOfType(t, "InlineFootnoteContent")!.children![0]
        .text!;
      return {
        name: "sup",
        attrs: {
          class: "sb-rendered-footnote-ref",
        },
        body: [
          {
            name: "span",
            attrs: {
              class: "sb-rendered-inline-footnote-content",
              title: content,
            },
            body: "*",
          },
        ],
      };
    }
    case "LuaDirective":
      return {
        name: "span",
        attrs: {
          class: "sb-lua-directive",
        },
        body: renderToText(t),
      };

    // Text
    case undefined:
      return t.text!;
    default:
      if (options.failOnUnknown) {
        removeParentPointers(t);
        console.error("Not handling", JSON.stringify(t, null, 2));
        throw new Error(`Unknown markdown node type ${t.type}`);
      } else {
        // Falling back to rendering verbatim
        removeParentPointers(t);
        console.warn("Not handling", JSON.stringify(t, null, 2));
        return renderToText(t);
      }
  }

  function mapRender(children: ParseTree[]) {
    return children.map((t) => posPreservingRender(t, options));
  }
}

function traverseTag(t: Tag, fn: (t: Tag) => void) {
  fn(t);
  if (typeof t === "string") {
    return;
  }
  if (t.body) {
    for (const child of t.body) {
      traverseTag(child, fn);
    }
  }
}

export function renderMarkdownToHtml(
  t: ParseTree,
  options: MarkdownRenderOptions = {},
  allPages: PageMeta[] = [],
) {
  preprocess(t);
  const htmlTree = posPreservingRender(t, options);
  if (htmlTree) {
    traverseTag(htmlTree, (t) => {
      if (typeof t === "string") {
        return;
      }
      if (t.name === "img" && options.translateUrls) {
        t.attrs!.src = options.translateUrls!(t.attrs!.src!, "image");
      }

      if (t.name === "a" && t.attrs!.href) {
        if (options.translateUrls) {
          t.attrs!.href = options.translateUrls!(t.attrs!.href, "link");
        }
        if (t.attrs!["data-ref"]?.length) {
          const ref = parseToRef(t.attrs!["data-ref"]!);
          if (!ref) {
            return;
          }

          const pageMeta = allPages.find(
            (p) => ref.path === parseToRef(p.ref)?.path,
          );
          if (
            pageMeta &&
            !(
              ref.details?.type === "position" ||
              ref.details?.type === "linecolumn"
            )
          ) {
            t.body = [(pageMeta.pageDecoration?.prefix ?? "") + t.body];
            if (pageMeta.pageDecoration?.cssClasses) {
              t.attrs!.class +=
                " sb-decorated-object " +
                pageMeta.pageDecoration.cssClasses
                  .join(" ")
                  .replaceAll(/[^a-zA-Z0-9-_ ]/g, "");
            }
          }
        }
        if (t.body.length === 0) {
          t.body = [t.attrs!.href];
        }
      }
    });
  }
  return renderHtml(htmlTree);
}