Add support for latex blocks / environments

current support for latex fragments was inline only, i.e. lines containing block
elements (e.g. a line starting with `* `, i.e. a headline) will not be parsed
as part of the latex fragment but the respective block element. Parsing latex
blocks at the block level should fix that. Note that in any case we don't do
any processing and just emit the raw latex (leaving the rendering to e.g. js).

org/block.go

@@ -1,6 +1,7 @@
 package org
 
 import (
+	"math"
 	"regexp"
 	"strings"
 	"unicode"
@@ -21,9 +22,15 @@ type Example struct {
 	Children []Node
 }
 
+type LatexBlock struct {
+	Content []Node
+}
+
 var exampleLineRegexp = regexp.MustCompile(`^(\s*):(\s(.*)|\s*$)`)
 var beginBlockRegexp = regexp.MustCompile(`(?i)^(\s*)#\+BEGIN_(\w+)(.*)`)
 var endBlockRegexp = regexp.MustCompile(`(?i)^(\s*)#\+END_(\w+)`)
+var beginLatexBlockRegexp = regexp.MustCompile(`(?i)^(\s*)\\begin{([^}]+)}(\s*)$`)
+var endLatexBlockRegexp = regexp.MustCompile(`(?i)^(\s*)\\end{([^}]+)}(\s*)$`)
 var resultRegexp = regexp.MustCompile(`(?i)^(\s*)#\+RESULTS:`)
 var exampleBlockEscapeRegexp = regexp.MustCompile(`(^|\n)([ \t]*),([ \t]*)(\*|,\*|#\+|,#\+)`)
 
@@ -36,6 +43,15 @@ func lexBlock(line string) (token, bool) {
 	return nilToken, false
 }
 
+func lexLatexBlock(line string) (token, bool) {
+	if m := beginLatexBlockRegexp.FindStringSubmatch(line); m != nil {
+		return token{"beginLatexBlock", len(m[1]), strings.ToUpper(m[2]), m}, true
+	} else if m := endLatexBlockRegexp.FindStringSubmatch(line); m != nil {
+		return token{"endLatexBlock", len(m[1]), strings.ToUpper(m[2]), m}, true
+	}
+	return nilToken, false
+}
+
 func lexResult(line string) (token, bool) {
 	if m := resultRegexp.FindStringSubmatch(line); m != nil {
 		return token{"result", len(m[1]), "", m}, true
@@ -85,6 +101,22 @@ func (d *Document) parseBlock(i int, parentStop stopFn) (int, Node) {
 	return i + 1 - start, block
 }
 
+func (d *Document) parseLatexBlock(i int, parentStop stopFn) (int, Node) {
+	t, start := d.tokens[i], i
+	name, rawText, trim := t.content, "", trimIndentUpTo(int(math.Max((float64(d.baseLvl)), float64(t.lvl))))
+	stop := func(d *Document, i int) bool {
+		return i >= len(d.tokens) || (d.tokens[i].kind == "endLatexBlock" && d.tokens[i].content == name)
+	}
+	for ; !stop(d, i); i++ {
+		rawText += trim(d.tokens[i].matches[0]) + "\n"
+	}
+	if i >= len(d.tokens) || d.tokens[i].kind != "endLatexBlock" || d.tokens[i].content != name {
+		return 0, nil
+	}
+	rawText += trim(d.tokens[i].matches[0])
+	return i + 1 - start, LatexBlock{d.parseRawInline(rawText)}
+}
+
 func (d *Document) parseSrcBlockResult(i int, parentStop stopFn) (int, Node) {
 	start := i
 	for ; !parentStop(d, i) && d.tokens[i].kind == "text" && d.tokens[i].content == ""; i++ {
@@ -145,6 +177,7 @@ func (b Block) ParameterMap() map[string]string {
 	return m
 }
 
-func (n Example) String() string { return orgWriter.WriteNodesAsString(n) }
+func (n Example) String() string    { return orgWriter.WriteNodesAsString(n) }
-func (n Block) String() string   { return orgWriter.WriteNodesAsString(n) }
+func (n Block) String() string      { return orgWriter.WriteNodesAsString(n) }
-func (n Result) String() string  { return orgWriter.WriteNodesAsString(n) }
+func (n LatexBlock) String() string { return orgWriter.WriteNodesAsString(n) }
+func (n Result) String() string     { return orgWriter.WriteNodesAsString(n) }

org/document.go

@@ -72,6 +72,7 @@ var lexFns = []lexFn{
 	lexKeywordOrComment,
 	lexFootnoteDefinition,
 	lexExample,
+	lexLatexBlock,
 	lexText,
 }
 
@@ -209,6 +210,8 @@ func (d *Document) parseOne(i int, stop stopFn) (consumed int, node Node) {
 		consumed, node = d.parseTable(i, stop)
 	case "beginBlock":
 		consumed, node = d.parseBlock(i, stop)
+	case "beginLatexBlock":
+		consumed, node = d.parseLatexBlock(i, stop)
 	case "result":
 		consumed, node = d.parseResult(i, stop)
 	case "beginDrawer":

org/html_writer.go

@@ -162,6 +162,11 @@ func (w *HTMLWriter) WriteBlock(b Block) {
 	}
 }
 
+func (w *HTMLWriter) WriteLatexBlock(b LatexBlock) {
+	WriteNodes(w, b.Content...)
+	w.WriteString("\n")
+}
+
 func (w *HTMLWriter) WriteResult(r Result) { WriteNodes(w, r.Node) }
 
 func (w *HTMLWriter) WriteInlineBlock(b InlineBlock) {

org/org_writer.go

@@ -109,6 +109,12 @@ func (w *OrgWriter) WriteBlock(b Block) {
 	}
 }
 
+func (w *OrgWriter) WriteLatexBlock(b LatexBlock) {
+	w.WriteString(w.indent)
+	WriteNodes(w, b.Content...)
+	w.WriteString("\n")
+}
+
 func (w *OrgWriter) WriteResult(r Result) {
 	w.WriteString("#+RESULTS:\n")
 	WriteNodes(w, r.Node)

org/testdata/latex.html

@@ -6,8 +6,18 @@ we support <code class="verbatim">\(...\)</code>, <code class="verbatim">\[...\]
 <li>\[\sum_{i=1}^n a_n\]</li>
 <li>$$\sum_{i=1}^n a_n$$</li>
 <li>\begin{xyz}\sum_{i=1}^n a_n\end{xyz}</li>
-<li>\begin{xyz}
+<li>
+\begin{xyz}
 \sum_{i=1}^n a_n
-\end{xyz}</li>
+\end{xyz}
+</li>
 <li>$2 + 2$, $3 - 3$</li>
+<li>
+\begin{xyz}
+latex block ignores block lvl elements (e.g. list - line starting with -)
+a = b
+- c
+- d
+\end{xyz}
+</li>
 </ul>

org/testdata/latex.org

@@ -10,3 +10,9 @@ we support =\(...\)=, =\[...\]=, =$$...$$= and =\begin{$env}...\end{$env}= as la
   \sum_{i=1}^n a_n
   \end{xyz}
 - $2 + 2$, $3 - 3$
+- \begin{xyz}
+  latex block ignores block lvl elements (e.g. list - line starting with -)
+  a = b
+  - c
+  - d
+  \end{xyz}

org/testdata/latex.pretty_org

@@ -10,3 +10,9 @@ we support =\(...\)=, =\[...\]=, =$$...$$= and =\begin{$env}...\end{$env}= as la
   \sum_{i=1}^n a_n
   \end{xyz}
 - $2 + 2$, $3 - 3$
+- \begin{xyz}
+  latex block ignores block lvl elements (e.g. list - line starting with -)
+  a = b
+  - c
+  - d
+  \end{xyz}

org/writer.go

@@ -19,6 +19,7 @@ type Writer interface {
 	WriteHeadline(Headline)
 	WriteBlock(Block)
 	WriteResult(Result)
+	WriteLatexBlock(LatexBlock)
 	WriteInlineBlock(InlineBlock)
 	WriteExample(Example)
 	WriteDrawer(Drawer)
@@ -62,6 +63,8 @@ func WriteNodes(w Writer, nodes ...Node) {
 			w.WriteBlock(n)
 		case Result:
 			w.WriteResult(n)
+		case LatexBlock:
+			w.WriteLatexBlock(n)
 		case InlineBlock:
 			w.WriteInlineBlock(n)
 		case Example: