From cc8667004b2aee4247956e9ee6f4efe4b88769bc Mon Sep 17 00:00:00 2001
From: Felix Van der Jeugt <felix.vanderjeugt@posteo.net>
Date: Fri, 4 Dec 2020 14:52:07 +0100
Subject: [PATCH] add a markdown lexer to vis

---
 config/vis/lexers/markdown.lua | 110 +++++++++++++++++++++++++++++++++
 1 file changed, 110 insertions(+)
 create mode 100644 config/vis/lexers/markdown.lua

diff --git a/config/vis/lexers/markdown.lua b/config/vis/lexers/markdown.lua
new file mode 100644
index 0000000..50405fe
--- /dev/null
+++ b/config/vis/lexers/markdown.lua
@@ -0,0 +1,110 @@
+-- Copyright 2006-2017 Mitchell mitchell.att.foicica.com. See LICENSE.
+-- Markdown LPeg lexer.
+
+local l = require('lexer')
+local token, word_match = l.token, l.word_match
+local P, R, S = lpeg.P, lpeg.R, lpeg.S
+
+local M = {_NAME = 'markdown'}
+
+-- Whitespace.
+local ws = token(l.WHITESPACE, l.space^1)
+
+-- Block elements.
+local header = token('h6', l.starts_line('######') * l.nonnewline^0) +
+               token('h5', l.starts_line('#####') * l.nonnewline^0) +
+               token('h4', l.starts_line('####') * l.nonnewline^0) +
+               token('h3', l.starts_line('###') * l.nonnewline^0) +
+               token('h2', l.starts_line('##') * l.nonnewline^0) +
+               token('h1', l.starts_line('#') * l.nonnewline^0)
+
+local blockquote = token(l.STRING,
+                         lpeg.Cmt(l.starts_line(S(' \t')^0 * '>'),
+                                  function(input, index)
+                                    local _, e = input:find('\n[ \t]*\r?\n',
+                                                            index)
+                                    return (e or #input) + 1
+                                  end))
+
+local blockcode = token('code', l.starts_line(P(' ')^4 + P('\t')) * -P('<') *
+                                l.nonnewline^0)
+
+local hr = token('hr', lpeg.Cmt(l.starts_line(S(' \t')^0 * lpeg.C(S('*-_'))),
+                                function(input, index, c)
+                                  local line = input:match('[^\n]*', index)
+                                  line = line:gsub('[ \t]', '')
+                                  if line:find('[^'..c..']') or #line < 2 then
+                                    return nil
+                                  end
+                                  return (input:find('\n', index) or #input) + 1
+                                end))
+
+-- Span elements.
+local dq_str = token(l.STRING, l.delimited_range('"', false, true))
+local sq_str = token(l.STRING, l.delimited_range("'", false, true))
+local paren_str = token(l.STRING, l.delimited_range('()'))
+local link = token('link', P('!')^-1 * l.delimited_range('[]') *
+                           (P('(') * (l.any - S(') \t'))^0 *
+                            (S(' \t')^1 *
+                             l.delimited_range('"', false, true))^-1 * ')' +
+                            S(' \t')^0 * l.delimited_range('[]')) +
+                           P('http://') * (l.any - l.space)^1)
+local link_label = token('link_label', l.delimited_range('[]') * ':') * ws *
+                   token('link_url', (l.any - l.space)^1) *
+                   (ws * (dq_str + sq_str + paren_str))^-1
+
+local strong = token('strong', (P('**') * (l.any - '**')^0 * P('**')^-1) +
+                               (P('__') * (l.any - '__')^0 * P('__')^-1))
+local em = token('em',
+                 l.delimited_range('*', true) + l.delimited_range('_', true))
+local code = token('code', (P('``') * (l.any - '``')^0 * P('``')^-1) +
+                           l.delimited_range('`', true, true))
+
+local escape = token(l.DEFAULT, P('\\') * 1)
+
+local list = token('list',
+                   l.starts_line(S(' \t')^0 * (S('*+-') + R('09')^1 * '.')) *
+                   S(' \t'))
+
+M._rules = {
+  {'header', header},
+  {'blockquote', blockquote},
+  {'blockcode', blockcode},
+  {'hr', hr},
+  {'list', list},
+  {'whitespace', ws},
+  {'link_label', link_label},
+  {'escape', escape},
+  {'link', link},
+  {'strong', strong},
+  {'em', em},
+  {'code', code},
+}
+
+local font_size = 10
+local hstyle = 'fore:red'
+M._tokenstyles = {
+  h6 = hstyle,
+  h5 = hstyle..',size:'..(font_size + 1),
+  h4 = hstyle..',size:'..(font_size + 2),
+  h3 = hstyle..',size:'..(font_size + 3),
+  h2 = hstyle..',size:'..(font_size + 4),
+  h1 = hstyle..',size:'..(font_size + 5),
+  -- code = l.STYLE_EMBEDDED..',eolfilled',
+  code = 'fore:blue'..',eolfilled',
+  hr = l.STYLE_DEFAULT..',bold',
+  link = 'underlined',
+  link_url = 'underlined',
+  link_label = l.STYLE_LABEL,
+  strong = 'bold',
+  em = 'italics',
+  list = l.STYLE_CONSTANT,
+}
+
+-- Embedded HTML.
+local html = l.load('html')
+local start_rule = token('tag', l.starts_line(S(' \t')^0 * '<'))
+local end_rule = token(l.DEFAULT, P('\n')) -- TODO: l.WHITESPACE causes errors
+l.embed_lexer(M, html, start_rule, end_rule)
+
+return M