Add go dependencies for mdtoc

vendor/github.com/mmarkdown/mmark/mparser/index.go

@@ -0,0 +1,111 @@
+package mparser
+
+import (
+	"bytes"
+	"fmt"
+	"sort"
+
+	"github.com/gomarkdown/markdown/ast"
+	"github.com/mmarkdown/mmark/mast"
+)
+
+// IndexToDocumentIndex crawls the entire doc searching for indices, it will then return
+// an mast.DocumentIndex that contains a tree:
+//
+// IndexLetter
+// - IndexItem
+//   - IndexLink
+//   - IndexSubItem
+//     - IndexLink
+//     - IndexLink
+//
+// Which can then be rendered by the renderer.
+func IndexToDocumentIndex(doc ast.Node) *mast.DocumentIndex {
+	main := map[string]*mast.IndexItem{}
+	subitem := map[string][]*mast.IndexSubItem{} // gather these so we can add them in one swoop at the end
+
+	// Gather all indexes.
+	ast.WalkFunc(doc, func(node ast.Node, entering bool) ast.WalkStatus {
+		switch i := node.(type) {
+		case *ast.Index:
+			item := string(i.Item)
+
+			if _, ok := main[item]; !ok {
+				main[item] = &mast.IndexItem{Index: i}
+			}
+			// only the main item
+			if i.Subitem == nil {
+				ast.AppendChild(main[item], newLink(i.ID, len(main[item].GetChildren()), i.Primary))
+				return ast.GoToNext
+			}
+			// check if we already have a child with the subitem and then just add the link
+			for _, sub := range subitem[item] {
+				if bytes.Compare(sub.Subitem, i.Subitem) == 0 {
+					ast.AppendChild(sub, newLink(i.ID, len(sub.GetChildren()), i.Primary))
+					return ast.GoToNext
+				}
+			}
+
+			sub := &mast.IndexSubItem{Index: i}
+			ast.AppendChild(sub, newLink(i.ID, len(subitem[item]), i.Primary))
+			subitem[item] = append(subitem[item], sub)
+		}
+		return ast.GoToNext
+	})
+	if len(main) == 0 {
+		return nil
+	}
+
+	// Now add a subitem children to the correct main item.
+	for k, sub := range subitem {
+		// sort sub here ideally
+		for j := range sub {
+			ast.AppendChild(main[k], sub[j])
+		}
+	}
+
+	keys := []string{}
+	for k := range main {
+		keys = append(keys, k)
+	}
+	sort.Strings(keys)
+
+	letters := []*mast.IndexLetter{}
+	var prevLetter byte
+	var il *mast.IndexLetter
+	for _, k := range keys {
+		letter := k[0]
+		if letter != prevLetter {
+			il = &mast.IndexLetter{}
+			il.Literal = []byte{letter}
+			letters = append(letters, il)
+		}
+		ast.AppendChild(il, main[k])
+		prevLetter = letter
+	}
+	docIndex := &mast.DocumentIndex{}
+	for i := range letters {
+		ast.AppendChild(docIndex, letters[i])
+	}
+
+	return docIndex
+}
+
+func newLink(id string, number int, primary bool) *mast.IndexLink {
+	link := &ast.Link{Destination: []byte(id)}
+	il := &mast.IndexLink{Link: link, Primary: primary}
+	il.Literal = []byte(fmt.Sprintf("%d", number))
+	return il
+}
+
+// AddIndex adds an index to the end of the current document. If not indices can be found
+// this returns false and no index will be added.
+func AddIndex(doc ast.Node) bool {
+	idx := IndexToDocumentIndex(doc)
+	if idx == nil {
+		return false
+	}
+
+	ast.AppendChild(doc, idx)
+	return true
+}