From ffb08ed9ee28c18a5058b2f21e5e8f392f80b79e Mon Sep 17 00:00:00 2001
From: Dmitriy Pleshevskiy <dmitriy@ideascup.me>
Date: Sat, 11 Jun 2022 22:07:22 +0300
Subject: [PATCH] par(md): add parsing heading

---
 .gitignore     |  6 +++++
 par/md.test.ts | 23 ++++++++++++++++
 par/md.ts      | 73 ++++++++++++++++++++++++++++++++++++++++++++++++++
 par/types.ts   |  5 ++++
 4 files changed, 107 insertions(+)
 create mode 100644 par/md.test.ts
 create mode 100644 par/md.ts
 create mode 100644 par/types.ts

diff --git a/.gitignore b/.gitignore
index 8c55080..4634098 100644
--- a/.gitignore
+++ b/.gitignore
@@ -9,5 +9,11 @@
 !/import_map.json
 
 !/core
+/core/*
 !/ren
+/ren/*
+!/par
+/par/*
+
+!/**/*.ts
 
diff --git a/par/md.test.ts b/par/md.test.ts
new file mode 100644
index 0000000..436708b
--- /dev/null
+++ b/par/md.test.ts
@@ -0,0 +1,23 @@
+import { assertEquals } from "testing/asserts.ts";
+import { HtmlStrRenderer } from "../ren/html_str.ts";
+import { MarkdownParser } from "./md.ts";
+
+const ren = new HtmlStrRenderer();
+
+Deno.test({
+  name: "should parse header",
+  fn: () => {
+    const par = new MarkdownParser();
+    const res = par.parse("#");
+    assertEquals(ren.render(res), "<h1></h1>");
+  },
+});
+
+Deno.test({
+  name: "should parse header with text",
+  fn: () => {
+    const par = new MarkdownParser();
+    const res = par.parse("# hello");
+    assertEquals(ren.render(res), "<h1>hello</h1>");
+  },
+});
diff --git a/par/md.ts b/par/md.ts
new file mode 100644
index 0000000..e6a275a
--- /dev/null
+++ b/par/md.ts
@@ -0,0 +1,73 @@
+import { AnyNode, Elem, Fragment, TextNode } from "../core/node.ts";
+import { isNil } from "../core/utils.ts";
+import { Parser } from "./types.ts";
+
+const RE_OPEN_HEADING = /^\s{0,3}(#{1,6})(\s|$)/;
+
+export class MarkdownParser implements Parser {
+  parse(input: string): AnyNode {
+    const ast: AstDocument = { kind: AstKind.Document, content: [] };
+
+    let readStr = input;
+
+    const match = RE_OPEN_HEADING.exec(readStr);
+    if (!isNil(match)) {
+      readStr = readStr.slice(match[0].length);
+
+      console.log({ match });
+
+      const heading: AstHeading = {
+        kind: AstKind.Heading,
+        level: match[1].length as HeadingLevel,
+        content: [],
+      };
+      ast.content.push(heading);
+
+      if (match[2].length > 0) {
+        const textContent = readStr.split("\n", 1)[0];
+        readStr = readStr.slice(textContent.length);
+
+        const text: AstText = {
+          kind: AstKind.Text,
+          content: textContent,
+        };
+
+        heading.content.push(text);
+      }
+    }
+
+    return new Fragment(ast.content.map(Heading));
+  }
+}
+
+function Heading(ast: AstHeading): Elem {
+  return new Elem(`h${ast.level}`, {}, ast.content.map(Text));
+}
+
+function Text(ast: AstText): TextNode {
+  return new TextNode(ast.content);
+}
+
+// AST
+
+type AstDocument = BaseAstItem<AstKind.Document, AstDocumentChild[]>;
+type AstDocumentChild = AstHeading;
+
+interface AstHeading extends BaseAstItem<AstKind.Heading, AstText[]> {
+  level: HeadingLevel;
+}
+
+type AstText = BaseAstItem<AstKind.Text, string>;
+
+type HeadingLevel = 1 | 2 | 3 | 4 | 5 | 6;
+
+interface BaseAstItem<K extends AstKind, Cont> {
+  kind: K;
+  content: Cont;
+}
+
+enum AstKind {
+  Document,
+  Heading,
+  Text,
+}
diff --git a/par/types.ts b/par/types.ts
new file mode 100644
index 0000000..ecbf894
--- /dev/null
+++ b/par/types.ts
@@ -0,0 +1,5 @@
+import { AnyNode } from "../core/node.ts";
+
+export interface Parser {
+  parse(input: string): AnyNode;
+}