From 0355745bf4326e0186538432d1f70145503cc232 Mon Sep 17 00:00:00 2001
From: Miek Gieben <miek@miek.nl>
Date: Sun, 29 Jul 2018 17:03:36 +0100
Subject: [PATCH] Ordered list: detect starting number

This keeps track of the starting number of an ordered list and uses it
when not zero. Fails the tests so it will probably have to wait until
we have the Mmark extension merged.

Signed-off-by: Miek Gieben <miek@miek.nl>
---
 ast/node.go      |  1 +
 html/renderer.go |  3 +++
 parser/block.go  | 23 ++++++++++++++++-------
 3 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/ast/node.go b/ast/node.go
index 6fe70cd..825b343 100644
--- a/ast/node.go
+++ b/ast/node.go
@@ -137,6 +137,7 @@ type List struct {
 	Tight           bool   // Skip <p>s around list item data if true
 	BulletChar      byte   // '*', '+' or '-' in bullet lists
 	Delimiter       byte   // '.' or ')' after the number in ordered lists
+	Start           int    // for ordered lists this indicates the starting number if > 0
 	RefLink         []byte // If not nil, turns this list item into a footnote item and triggers different rendering
 	IsFootnotesList bool   // This is a list of footnotes
 }
diff --git a/html/renderer.go b/html/renderer.go
index 6089e56..0d03e98 100644
--- a/html/renderer.go
+++ b/html/renderer.go
@@ -653,6 +653,9 @@ func (r *Renderer) listEnter(w io.Writer, nodeData *ast.List) {
 
 	openTag := "<ul"
 	if nodeData.ListFlags&ast.ListTypeOrdered != 0 {
+		if nodeData.Start > 0 {
+			attrs = append(attrs, fmt.Sprintf(`start="%d"`, nodeData.Start))
+		}
 		openTag = "<ol"
 	}
 	if nodeData.ListFlags&ast.ListTypeDefinition != 0 {
diff --git a/parser/block.go b/parser/block.go
index 3f78754..45c6244 100644
--- a/parser/block.go
+++ b/parser/block.go
@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"html"
 	"regexp"
+	"strconv"
 	"unicode"
 
 	"github.com/gomarkdown/markdown/ast"
@@ -229,7 +230,7 @@ func (p *Parser) block(data []byte) {
 		//
 		// also works with + or -
 		if p.uliPrefix(data) > 0 {
-			data = data[p.list(data, 0):]
+			data = data[p.list(data, 0, 0):]
 			continue
 		}
 
@@ -237,8 +238,15 @@ func (p *Parser) block(data []byte) {
 		//
 		// 1. Item 1
 		// 2. Item 2
-		if p.oliPrefix(data) > 0 {
-			data = data[p.list(data, ast.ListTypeOrdered):]
+		if i := p.oliPrefix(data); i > 0 {
+			start := 0
+			if i > 2 {
+				start, _ = strconv.Atoi(string(data[:i-2])) // this cannot fail because we just est. the thing *is* a number.
+				if start == 1 {
+					start = 0
+				}
+			}
+			data = data[p.list(data, ast.ListTypeOrdered, start):]
 			continue
 		}
 
@@ -252,7 +260,7 @@ func (p *Parser) block(data []byte) {
 		// :   Definition c
 		if p.extensions&DefinitionLists != 0 {
 			if p.dliPrefix(data) > 0 {
-				data = data[p.list(data, ast.ListTypeDefinition):]
+				data = data[p.list(data, ast.ListTypeDefinition, 0):]
 				continue
 			}
 		}
@@ -1192,12 +1200,13 @@ func (p *Parser) dliPrefix(data []byte) int {
 }
 
 // parse ordered or unordered list block
-func (p *Parser) list(data []byte, flags ast.ListType) int {
+func (p *Parser) list(data []byte, flags ast.ListType, start int) int {
 	i := 0
 	flags |= ast.ListItemBeginningOfList
 	list := &ast.List{
 		ListFlags: flags,
 		Tight:     true,
+		Start:     start,
 	}
 	block := p.addBlock(list)
 
@@ -1533,7 +1542,7 @@ func (p *Parser) paragraph(data []byte) int {
 			// did this blank line followed by a definition list item?
 			if p.extensions&DefinitionLists != 0 {
 				if i < len(data)-1 && data[i+1] == ':' {
-					listLen := p.list(data[prev:], ast.ListTypeDefinition)
+					listLen := p.list(data[prev:], ast.ListTypeDefinition, 0)
 					return prev + listLen
 				}
 			}
@@ -1600,7 +1609,7 @@ func (p *Parser) paragraph(data []byte) int {
 		// if there's a definition list item, prev line is a definition term
 		if p.extensions&DefinitionLists != 0 {
 			if p.dliPrefix(current) != 0 {
-				ret := p.list(data[prev:], ast.ListTypeDefinition)
+				ret := p.list(data[prev:], ast.ListTypeDefinition, 0)
 				return ret + prev
 			}
 		}