From e81d1d11386a0ee9550ce7e2725fb003e15c6c44 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Vytautas=20=C5=A0altenis?= <vytas@rtfb.lt>
Date: Thu, 2 Feb 2017 09:35:10 +0200
Subject: [PATCH] Change the public interface to use functional options

Convert the most important Blackfriday's function, Markdown(), to accept
functional options (as per this Dave Cheney's post:
https://dave.cheney.net/2014/10/17/functional-options-for-friendly-apis)
---
 block.go        |  58 ++++++-------
 block_test.go   |   4 +-
 helpers_test.go |  18 ++--
 inline.go       |  34 ++++----
 inline_test.go  |  70 ++++++++-------
 markdown.go     | 222 ++++++++++++++++++++++++++----------------------
 ref_test.go     |   2 +-
 7 files changed, 212 insertions(+), 196 deletions(-)

diff --git a/block.go b/block.go
index 9d3a003..43df826 100644
--- a/block.go
+++ b/block.go
@@ -34,7 +34,7 @@ var (
 // Parse block-level data.
 // Note: this function and many that it calls assume that
 // the input buffer ends with a newline.
-func (p *parser) block(data []byte) {
+func (p *Parser) block(data []byte) {
 	// this is called recursively: enforce a maximum depth
 	if p.nesting >= p.maxNesting {
 		return
@@ -197,14 +197,14 @@ func (p *parser) block(data []byte) {
 	p.nesting--
 }
 
-func (p *parser) addBlock(typ NodeType, content []byte) *Node {
+func (p *Parser) addBlock(typ NodeType, content []byte) *Node {
 	p.closeUnmatchedBlocks()
 	container := p.addChild(typ, 0)
 	container.content = content
 	return container
 }
 
-func (p *parser) isPrefixHeader(data []byte) bool {
+func (p *Parser) isPrefixHeader(data []byte) bool {
 	if data[0] != '#' {
 		return false
 	}
@@ -221,7 +221,7 @@ func (p *parser) isPrefixHeader(data []byte) bool {
 	return true
 }
 
-func (p *parser) prefixHeader(data []byte) int {
+func (p *Parser) prefixHeader(data []byte) int {
 	level := 0
 	for level < 6 && level < len(data) && data[level] == '#' {
 		level++
@@ -267,7 +267,7 @@ func (p *parser) prefixHeader(data []byte) int {
 	return skip
 }
 
-func (p *parser) isUnderlinedHeader(data []byte) int {
+func (p *Parser) isUnderlinedHeader(data []byte) int {
 	// test of level 1 header
 	if data[0] == '=' {
 		i := skipChar(data, 1, '=')
@@ -291,7 +291,7 @@ func (p *parser) isUnderlinedHeader(data []byte) int {
 	return 0
 }
 
-func (p *parser) titleBlock(data []byte, doRender bool) int {
+func (p *Parser) titleBlock(data []byte, doRender bool) int {
 	if data[0] != '%' {
 		return 0
 	}
@@ -315,7 +315,7 @@ func (p *parser) titleBlock(data []byte, doRender bool) int {
 	return consumed
 }
 
-func (p *parser) html(data []byte, doRender bool) int {
+func (p *Parser) html(data []byte, doRender bool) int {
 	var i, j int
 
 	// identify the opening tag
@@ -419,7 +419,7 @@ func finalizeHTMLBlock(block *Node) {
 }
 
 // HTML comment, lax form
-func (p *parser) htmlComment(data []byte, doRender bool) int {
+func (p *Parser) htmlComment(data []byte, doRender bool) int {
 	i := p.inlineHTMLComment(data)
 	// needs to end with a blank line
 	if j := p.isEmpty(data[i:]); j > 0 {
@@ -439,7 +439,7 @@ func (p *parser) htmlComment(data []byte, doRender bool) int {
 }
 
 // HR, which is the only self-closing block tag considered
-func (p *parser) htmlHr(data []byte, doRender bool) int {
+func (p *Parser) htmlHr(data []byte, doRender bool) int {
 	if len(data) < 4 {
 		return 0
 	}
@@ -472,7 +472,7 @@ func (p *parser) htmlHr(data []byte, doRender bool) int {
 	return 0
 }
 
-func (p *parser) htmlFindTag(data []byte) (string, bool) {
+func (p *Parser) htmlFindTag(data []byte) (string, bool) {
 	i := 0
 	for i < len(data) && isalnum(data[i]) {
 		i++
@@ -484,7 +484,7 @@ func (p *parser) htmlFindTag(data []byte) (string, bool) {
 	return "", false
 }
 
-func (p *parser) htmlFindEnd(tag string, data []byte) int {
+func (p *Parser) htmlFindEnd(tag string, data []byte) int {
 	// assume data[0] == '<' && data[1] == '/' already tested
 	if tag == "hr" {
 		return 2
@@ -519,7 +519,7 @@ func (p *parser) htmlFindEnd(tag string, data []byte) int {
 	return i + skip
 }
 
-func (*parser) isEmpty(data []byte) int {
+func (*Parser) isEmpty(data []byte) int {
 	// it is okay to call isEmpty on an empty buffer
 	if len(data) == 0 {
 		return 0
@@ -537,7 +537,7 @@ func (*parser) isEmpty(data []byte) int {
 	return i
 }
 
-func (*parser) isHRule(data []byte) bool {
+func (*Parser) isHRule(data []byte) bool {
 	i := 0
 
 	// skip up to three spaces
@@ -667,7 +667,7 @@ func isFenceLine(data []byte, syntax *string, oldmarker string) (end int, marker
 // fencedCodeBlock returns the end index if data contains a fenced code block at the beginning,
 // or 0 otherwise. It writes to out if doRender is true, otherwise it has no side effects.
 // If doRender is true, a final newline is mandatory to recognize the fenced code block.
-func (p *parser) fencedCodeBlock(data []byte, doRender bool) int {
+func (p *Parser) fencedCodeBlock(data []byte, doRender bool) int {
 	var syntax string
 	beg, marker := isFenceLine(data, &syntax, "")
 	if beg == 0 || beg >= len(data) {
@@ -739,7 +739,7 @@ func finalizeCodeBlock(block *Node) {
 	block.content = nil
 }
 
-func (p *parser) table(data []byte) int {
+func (p *Parser) table(data []byte) int {
 	table := p.addBlock(Table, nil)
 	i, columns := p.tableHeader(data)
 	if i == 0 {
@@ -782,7 +782,7 @@ func isBackslashEscaped(data []byte, i int) bool {
 	return backslashes&1 == 1
 }
 
-func (p *parser) tableHeader(data []byte) (size int, columns []CellAlignFlags) {
+func (p *Parser) tableHeader(data []byte) (size int, columns []CellAlignFlags) {
 	i := 0
 	colCount := 1
 	for i = 0; i < len(data) && data[i] != '\n'; i++ {
@@ -895,7 +895,7 @@ func (p *parser) tableHeader(data []byte) (size int, columns []CellAlignFlags) {
 	return
 }
 
-func (p *parser) tableRow(data []byte, columns []CellAlignFlags, header bool) {
+func (p *Parser) tableRow(data []byte, columns []CellAlignFlags, header bool) {
 	p.addBlock(TableRow, nil)
 	i, col := 0, 0
 
@@ -939,7 +939,7 @@ func (p *parser) tableRow(data []byte, columns []CellAlignFlags, header bool) {
 }
 
 // returns blockquote prefix length
-func (p *parser) quotePrefix(data []byte) int {
+func (p *Parser) quotePrefix(data []byte) int {
 	i := 0
 	for i < 3 && i < len(data) && data[i] == ' ' {
 		i++
@@ -955,7 +955,7 @@ func (p *parser) quotePrefix(data []byte) int {
 
 // blockquote ends with at least one blank line
 // followed by something without a blockquote prefix
-func (p *parser) terminateBlockquote(data []byte, beg, end int) bool {
+func (p *Parser) terminateBlockquote(data []byte, beg, end int) bool {
 	if p.isEmpty(data[beg:]) <= 0 {
 		return false
 	}
@@ -966,7 +966,7 @@ func (p *parser) terminateBlockquote(data []byte, beg, end int) bool {
 }
 
 // parse a blockquote fragment
-func (p *parser) quote(data []byte) int {
+func (p *Parser) quote(data []byte) int {
 	block := p.addBlock(BlockQuote, nil)
 	var raw bytes.Buffer
 	beg, end := 0, 0
@@ -1004,7 +1004,7 @@ func (p *parser) quote(data []byte) int {
 }
 
 // returns prefix length for block code
-func (p *parser) codePrefix(data []byte) int {
+func (p *Parser) codePrefix(data []byte) int {
 	if len(data) >= 1 && data[0] == '\t' {
 		return 1
 	}
@@ -1014,7 +1014,7 @@ func (p *parser) codePrefix(data []byte) int {
 	return 0
 }
 
-func (p *parser) code(data []byte) int {
+func (p *Parser) code(data []byte) int {
 	var work bytes.Buffer
 
 	i := 0
@@ -1064,7 +1064,7 @@ func (p *parser) code(data []byte) int {
 }
 
 // returns unordered list item prefix
-func (p *parser) uliPrefix(data []byte) int {
+func (p *Parser) uliPrefix(data []byte) int {
 	i := 0
 	// start with up to 3 spaces
 	for i < len(data) && i < 3 && data[i] == ' ' {
@@ -1082,7 +1082,7 @@ func (p *parser) uliPrefix(data []byte) int {
 }
 
 // returns ordered list item prefix
-func (p *parser) oliPrefix(data []byte) int {
+func (p *Parser) oliPrefix(data []byte) int {
 	i := 0
 
 	// start with up to 3 spaces
@@ -1107,7 +1107,7 @@ func (p *parser) oliPrefix(data []byte) int {
 }
 
 // returns definition list item prefix
-func (p *parser) dliPrefix(data []byte) int {
+func (p *Parser) dliPrefix(data []byte) int {
 	if len(data) < 2 {
 		return 0
 	}
@@ -1123,7 +1123,7 @@ func (p *parser) dliPrefix(data []byte) int {
 }
 
 // parse ordered or unordered list block
-func (p *parser) list(data []byte, flags ListType) int {
+func (p *Parser) list(data []byte, flags ListType) int {
 	i := 0
 	flags |= ListItemBeginningOfList
 	block := p.addBlock(List, nil)
@@ -1191,7 +1191,7 @@ func finalizeList(block *Node) {
 
 // Parse a single list item.
 // Assumes initial prefix is already removed if this is a sublist.
-func (p *parser) listItem(data []byte, flags *ListType) int {
+func (p *Parser) listItem(data []byte, flags *ListType) int {
 	// keep track of the indentation of the first line
 	itemIndent := 0
 	if data[0] == '\t' {
@@ -1383,7 +1383,7 @@ gatherlines:
 }
 
 // render a single paragraph that has already been parsed out
-func (p *parser) renderParagraph(data []byte) {
+func (p *Parser) renderParagraph(data []byte) {
 	if len(data) == 0 {
 		return
 	}
@@ -1408,7 +1408,7 @@ func (p *parser) renderParagraph(data []byte) {
 	p.addBlock(Paragraph, data[beg:end])
 }
 
-func (p *parser) paragraph(data []byte) int {
+func (p *Parser) paragraph(data []byte) int {
 	// prev: index of 1st char of previous line
 	// line: index of 1st char of current line
 	// i: index of cursor/end of current line
diff --git a/block_test.go b/block_test.go
index 0a944a1..b1554f9 100644
--- a/block_test.go
+++ b/block_test.go
@@ -253,7 +253,7 @@ func TestPrefixHeaderIdExtensionWithPrefixAndSuffix(t *testing.T) {
 	}
 
 	doTestsParam(t, tests, TestParams{
-		Options:                Options{Extensions: HeaderIDs},
+		extensions:             HeaderIDs,
 		HTMLFlags:              UseXHTML,
 		HTMLRendererParameters: parameters,
 	})
@@ -365,7 +365,7 @@ func TestPrefixAutoHeaderIdExtensionWithPrefixAndSuffix(t *testing.T) {
 	}
 
 	doTestsParam(t, tests, TestParams{
-		Options:                Options{Extensions: AutoHeaderIDs},
+		extensions:             AutoHeaderIDs,
 		HTMLFlags:              UseXHTML,
 		HTMLRendererParameters: parameters,
 	})
diff --git a/helpers_test.go b/helpers_test.go
index ecefe2f..d2639d2 100644
--- a/helpers_test.go
+++ b/helpers_test.go
@@ -21,7 +21,8 @@ import (
 )
 
 type TestParams struct {
-	Options
+	extensions        Extensions
+	referenceOverride ReferenceOverrideFunc
 	HTMLFlags
 	HTMLRendererParameters
 }
@@ -45,13 +46,15 @@ func execRecoverableTestSuite(t *testing.T, tests []string, params TestParams, s
 func runMarkdown(input string, params TestParams) string {
 	params.HTMLRendererParameters.Flags = params.HTMLFlags
 	renderer := NewHTMLRenderer(params.HTMLRendererParameters)
-	return string(Markdown([]byte(input), renderer, params.Options))
+	return string(Markdown([]byte(input), WithRenderer(renderer),
+		WithExtensions(params.extensions),
+		WithRefOverride(params.referenceOverride)))
 }
 
 // doTests runs full document tests using MarkdownCommon configuration.
 func doTests(t *testing.T, tests []string) {
 	doTestsParam(t, tests, TestParams{
-		Options: DefaultOptions,
+		extensions: CommonExtensions,
 		HTMLRendererParameters: HTMLRendererParameters{
 			Flags: CommonHTMLFlags,
 		},
@@ -60,8 +63,8 @@ func doTests(t *testing.T, tests []string) {
 
 func doTestsBlock(t *testing.T, tests []string, extensions Extensions) {
 	doTestsParam(t, tests, TestParams{
-		Options:   Options{Extensions: extensions},
-		HTMLFlags: UseXHTML,
+		extensions: extensions,
+		HTMLFlags:  UseXHTML,
 	})
 }
 
@@ -124,8 +127,7 @@ func doSafeTestsInline(t *testing.T, tests []string) {
 }
 
 func doTestsInlineParam(t *testing.T, tests []string, params TestParams) {
-	params.Options.Extensions |= Autolink
-	params.Options.Extensions |= Strikethrough
+	params.extensions |= Autolink | Strikethrough
 	params.HTMLFlags |= UseXHTML
 	doTestsParam(t, tests, params)
 }
@@ -145,7 +147,7 @@ func transformLinks(tests []string, prefix string) []string {
 }
 
 func doTestsReference(t *testing.T, files []string, flag Extensions) {
-	params := TestParams{Options: Options{Extensions: flag}}
+	params := TestParams{extensions: flag}
 	execRecoverableTestSuite(t, files, params, func(candidate *string) {
 		for _, basename := range files {
 			filename := filepath.Join("testdata", basename+".text")
diff --git a/inline.go b/inline.go
index 2a1db7a..67ca219 100644
--- a/inline.go
+++ b/inline.go
@@ -32,7 +32,7 @@ var (
 // data is the complete block being rendered
 // offset is the number of valid chars before the current cursor
 
-func (p *parser) inline(currBlock *Node, data []byte) {
+func (p *Parser) inline(currBlock *Node, data []byte) {
 	// handlers might call us recursively: enforce a maximum depth
 	if p.nesting >= p.maxNesting || len(data) == 0 {
 		return
@@ -69,7 +69,7 @@ func (p *parser) inline(currBlock *Node, data []byte) {
 }
 
 // single and double emphasis parsing
-func emphasis(p *parser, data []byte, offset int) (int, *Node) {
+func emphasis(p *Parser, data []byte, offset int) (int, *Node) {
 	data = data[offset:]
 	c := data[0]
 
@@ -114,7 +114,7 @@ func emphasis(p *parser, data []byte, offset int) (int, *Node) {
 	return 0, nil
 }
 
-func codeSpan(p *parser, data []byte, offset int) (int, *Node) {
+func codeSpan(p *Parser, data []byte, offset int) (int, *Node) {
 	data = data[offset:]
 
 	nb := 0
@@ -161,7 +161,7 @@ func codeSpan(p *parser, data []byte, offset int) (int, *Node) {
 }
 
 // newline preceded by two spaces becomes <br>
-func maybeLineBreak(p *parser, data []byte, offset int) (int, *Node) {
+func maybeLineBreak(p *Parser, data []byte, offset int) (int, *Node) {
 	origOffset := offset
 	for offset < len(data) && data[offset] == ' ' {
 		offset++
@@ -177,7 +177,7 @@ func maybeLineBreak(p *parser, data []byte, offset int) (int, *Node) {
 }
 
 // newline without two spaces works when HardLineBreak is enabled
-func lineBreak(p *parser, data []byte, offset int) (int, *Node) {
+func lineBreak(p *Parser, data []byte, offset int) (int, *Node) {
 	if p.flags&HardLineBreak != 0 {
 		return 1, NewNode(Hardbreak)
 	}
@@ -200,14 +200,14 @@ func isReferenceStyleLink(data []byte, pos int, t linkType) bool {
 	return pos < len(data)-1 && data[pos] == '[' && data[pos+1] != '^'
 }
 
-func maybeImage(p *parser, data []byte, offset int) (int, *Node) {
+func maybeImage(p *Parser, data []byte, offset int) (int, *Node) {
 	if offset < len(data)-1 && data[offset+1] == '[' {
 		return link(p, data, offset)
 	}
 	return 0, nil
 }
 
-func maybeInlineFootnote(p *parser, data []byte, offset int) (int, *Node) {
+func maybeInlineFootnote(p *Parser, data []byte, offset int) (int, *Node) {
 	if offset < len(data)-1 && data[offset+1] == '[' {
 		return link(p, data, offset)
 	}
@@ -215,7 +215,7 @@ func maybeInlineFootnote(p *parser, data []byte, offset int) (int, *Node) {
 }
 
 // '[': parse a link or an image or a footnote
-func link(p *parser, data []byte, offset int) (int, *Node) {
+func link(p *Parser, data []byte, offset int) (int, *Node) {
 	// no links allowed inside regular links, footnote, and deferred footnotes
 	if p.insideLink && (offset > 0 && data[offset-1] == '[' || len(data)-1 > offset && data[offset+1] == '^') {
 		return 0, nil
@@ -573,7 +573,7 @@ func link(p *parser, data []byte, offset int) (int, *Node) {
 	return i, linkNode
 }
 
-func (p *parser) inlineHTMLComment(data []byte) int {
+func (p *Parser) inlineHTMLComment(data []byte) int {
 	if len(data) < 5 {
 		return 0
 	}
@@ -613,7 +613,7 @@ const (
 )
 
 // '<' when tags or autolinks are allowed
-func leftAngle(p *parser, data []byte, offset int) (int, *Node) {
+func leftAngle(p *Parser, data []byte, offset int) (int, *Node) {
 	data = data[offset:]
 	altype, end := tagLength(data)
 	if size := p.inlineHTMLComment(data); size > 0 {
@@ -646,7 +646,7 @@ func leftAngle(p *parser, data []byte, offset int) (int, *Node) {
 // '\\' backslash escape
 var escapeChars = []byte("\\`*_{}[]()#+-.!:|&<>~")
 
-func escape(p *parser, data []byte, offset int) (int, *Node) {
+func escape(p *Parser, data []byte, offset int) (int, *Node) {
 	data = data[offset:]
 
 	if len(data) > 1 {
@@ -686,7 +686,7 @@ func unescapeText(ob *bytes.Buffer, src []byte) {
 
 // '&' escaped when it doesn't belong to an entity
 // valid entities are assumed to be anything matching &#?[A-Za-z0-9]+;
-func entity(p *parser, data []byte, offset int) (int, *Node) {
+func entity(p *Parser, data []byte, offset int) (int, *Node) {
 	data = data[offset:]
 
 	end := 1
@@ -748,7 +748,7 @@ var protocolPrefixes = [][]byte{
 
 const shortestPrefix = 6 // len("ftp://"), the shortest of the above
 
-func maybeAutoLink(p *parser, data []byte, offset int) (int, *Node) {
+func maybeAutoLink(p *Parser, data []byte, offset int) (int, *Node) {
 	// quick check to rule out most false hits
 	if p.insideLink || len(data) < offset+shortestPrefix {
 		return 0, nil
@@ -765,7 +765,7 @@ func maybeAutoLink(p *parser, data []byte, offset int) (int, *Node) {
 	return 0, nil
 }
 
-func autoLink(p *parser, data []byte, offset int) (int, *Node) {
+func autoLink(p *Parser, data []byte, offset int) (int, *Node) {
 	// Now a more expensive check to see if we're not inside an anchor element
 	anchorStart := offset
 	offsetFromAnchor := 0
@@ -1095,7 +1095,7 @@ func helperFindEmphChar(data []byte, c byte) int {
 	return 0
 }
 
-func helperEmphasis(p *parser, data []byte, c byte) (int, *Node) {
+func helperEmphasis(p *Parser, data []byte, c byte) (int, *Node) {
 	i := 0
 
 	// skip one symbol if coming from emph3
@@ -1135,7 +1135,7 @@ func helperEmphasis(p *parser, data []byte, c byte) (int, *Node) {
 	return 0, nil
 }
 
-func helperDoubleEmphasis(p *parser, data []byte, c byte) (int, *Node) {
+func helperDoubleEmphasis(p *Parser, data []byte, c byte) (int, *Node) {
 	i := 0
 
 	for i < len(data) {
@@ -1159,7 +1159,7 @@ func helperDoubleEmphasis(p *parser, data []byte, c byte) (int, *Node) {
 	return 0, nil
 }
 
-func helperTripleEmphasis(p *parser, data []byte, offset int, c byte) (int, *Node) {
+func helperTripleEmphasis(p *Parser, data []byte, offset int, c byte) (int, *Node) {
 	i := 0
 	origData := data
 	data = data[offset:]
diff --git a/inline_test.go b/inline_test.go
index 847980a..168ef17 100644
--- a/inline_test.go
+++ b/inline_test.go
@@ -100,38 +100,36 @@ func TestReferenceOverride(t *testing.T) {
 		"<p>test <a href=\"http://www.ref5.com/\" title=\"Reference 5\">Moo</a></p>\n",
 	}
 	doTestsInlineParam(t, tests, TestParams{
-		Options: Options{
-			ReferenceOverride: func(reference string) (rv *Reference, overridden bool) {
-				switch reference {
-				case "ref1":
-					// just an overridden reference exists without definition
-					return &Reference{
-						Link:  "http://www.ref1.com/",
-						Title: "Reference 1"}, true
-				case "ref2":
-					// overridden exists and reference defined
-					return &Reference{
-						Link:  "http://www.overridden.com/",
-						Title: "Reference Overridden"}, true
-				case "ref3":
-					// not overridden and reference defined
-					return nil, false
-				case "ref4":
-					// overridden missing and defined
-					return nil, true
-				case "!(*http.ServeMux).ServeHTTP":
-					return &Reference{
-						Link:  "http://localhost:6060/pkg/net/http/#ServeMux.ServeHTTP",
-						Title: "ServeHTTP docs"}, true
-				case "ref5":
-					return &Reference{
-						Link:  "http://www.ref5.com/",
-						Title: "Reference 5",
-						Text:  "Moo",
-					}, true
-				}
+		referenceOverride: func(reference string) (rv *Reference, overridden bool) {
+			switch reference {
+			case "ref1":
+				// just an overridden reference exists without definition
+				return &Reference{
+					Link:  "http://www.ref1.com/",
+					Title: "Reference 1"}, true
+			case "ref2":
+				// overridden exists and reference defined
+				return &Reference{
+					Link:  "http://www.overridden.com/",
+					Title: "Reference Overridden"}, true
+			case "ref3":
+				// not overridden and reference defined
 				return nil, false
-			},
+			case "ref4":
+				// overridden missing and defined
+				return nil, true
+			case "!(*http.ServeMux).ServeHTTP":
+				return &Reference{
+					Link:  "http://localhost:6060/pkg/net/http/#ServeMux.ServeHTTP",
+					Title: "ServeHTTP docs"}, true
+			case "ref5":
+				return &Reference{
+					Link:  "http://www.ref5.com/",
+					Title: "Reference 5",
+					Text:  "Moo",
+				}, true
+			}
+			return nil, false
 		},
 	})
 }
@@ -343,8 +341,8 @@ func TestLineBreak(t *testing.T) {
 		"this has an   \nextra space\n",
 		"<p>this has an<br />\nextra space</p>\n",
 	}
-	doTestsInlineParam(t, tests, TestParams{Options: Options{
-		Extensions: BackslashLineBreak}})
+	doTestsInlineParam(t, tests, TestParams{
+		extensions: BackslashLineBreak})
 }
 
 func TestInlineLink(t *testing.T) {
@@ -932,7 +930,7 @@ what happens here
 
 func TestFootnotes(t *testing.T) {
 	doTestsInlineParam(t, footnoteTests, TestParams{
-		Options: Options{Extensions: Footnotes},
+		extensions: Footnotes,
 	})
 }
 
@@ -959,7 +957,7 @@ func TestFootnotesWithParameters(t *testing.T) {
 	}
 
 	doTestsInlineParam(t, tests, TestParams{
-		Options:                Options{Extensions: Footnotes},
+		extensions:             Footnotes,
 		HTMLFlags:              FootnoteReturnLinks,
 		HTMLRendererParameters: params,
 	})
@@ -989,7 +987,7 @@ func TestNestedFootnotes(t *testing.T) {
 </div>
 `,
 	}
-	doTestsInlineParam(t, tests, TestParams{Options: Options{Extensions: Footnotes}})
+	doTestsInlineParam(t, tests, TestParams{extensions: Footnotes})
 }
 
 func TestInlineComments(t *testing.T) {
diff --git a/markdown.go b/markdown.go
index 9c3fdb0..b34d021 100644
--- a/markdown.go
+++ b/markdown.go
@@ -57,9 +57,9 @@ const (
 
 // DefaultOptions is a convenience variable with all the options that are
 // enabled by default.
-var DefaultOptions = Options{
-	Extensions: CommonExtensions,
-}
+// var DefaultOptions = Options{
+// 	Extensions: CommonExtensions,
+// }
 
 // ListType contains bitwise or'ed flags for list and list item objects.
 type ListType int
@@ -160,11 +160,11 @@ type Renderer interface {
 
 // Callback functions for inline parsing. One such function is defined
 // for each character that triggers a response when parsing inline data.
-type inlineParser func(p *parser, data []byte, offset int) (int, *Node)
+type inlineParser func(p *Parser, data []byte, offset int) (int, *Node)
 
 // Parser holds runtime state used by the parser.
 // This is constructed by the Markdown function.
-type parser struct {
+type Parser struct {
 	refOverride    ReferenceOverrideFunc
 	refs           map[string]*reference
 	inlineCallback [256]inlineParser
@@ -185,7 +185,7 @@ type parser struct {
 	allClosed            bool
 }
 
-func (p *parser) getRef(refid string) (ref *reference, found bool) {
+func (p *Parser) getRef(refid string) (ref *reference, found bool) {
 	if p.refOverride != nil {
 		r, overridden := p.refOverride(refid)
 		if overridden {
@@ -205,17 +205,17 @@ func (p *parser) getRef(refid string) (ref *reference, found bool) {
 	return ref, found
 }
 
-func (p *parser) finalize(block *Node) {
+func (p *Parser) finalize(block *Node) {
 	above := block.Parent
 	block.open = false
 	p.tip = above
 }
 
-func (p *parser) addChild(node NodeType, offset uint32) *Node {
+func (p *Parser) addChild(node NodeType, offset uint32) *Node {
 	return p.addExistingChild(NewNode(node), offset)
 }
 
-func (p *parser) addExistingChild(node *Node, offset uint32) *Node {
+func (p *Parser) addExistingChild(node *Node, offset uint32) *Node {
 	for !p.tip.canContain(node.Type) {
 		p.finalize(p.tip)
 	}
@@ -224,7 +224,7 @@ func (p *parser) addExistingChild(node *Node, offset uint32) *Node {
 	return node
 }
 
-func (p *parser) closeUnmatchedBlocks() {
+func (p *Parser) closeUnmatchedBlocks() {
 	if !p.allClosed {
 		for p.oldTip != p.lastMatchedContainer {
 			parent := p.oldTip.Parent
@@ -259,108 +259,46 @@ type Reference struct {
 // See the documentation in Options for more details on use-case.
 type ReferenceOverrideFunc func(reference string) (ref *Reference, overridden bool)
 
-// Options represents configurable overrides and callbacks (in addition to the
-// extension flag set) for configuring a Markdown parse.
-type Options struct {
-	// Extensions is a flag set of bit-wise ORed extension bits. See the
-	// Extensions flags defined in this package.
-	Extensions Extensions
-
-	// ReferenceOverride is an optional function callback that is called every
-	// time a reference is resolved.
-	//
-	// In Markdown, the link reference syntax can be made to resolve a link to
-	// a reference instead of an inline URL, in one of the following ways:
-	//
-	//  * [link text][refid]
-	//  * [refid][]
-	//
-	// Usually, the refid is defined at the bottom of the Markdown document. If
-	// this override function is provided, the refid is passed to the override
-	// function first, before consulting the defined refids at the bottom. If
-	// the override function indicates an override did not occur, the refids at
-	// the bottom will be used to fill in the link details.
-	ReferenceOverride ReferenceOverrideFunc
+// Processor contains all the state necessary for Blackfriday to operate.
+type Processor struct {
+	r                 Renderer
+	extensions        Extensions
+	referenceOverride ReferenceOverrideFunc
 }
 
-// MarkdownBasic is a convenience function for simple rendering.
-// It processes markdown input with no extensions enabled.
-func MarkdownBasic(input []byte) []byte {
-	// set up the HTML renderer
-	renderer := NewHTMLRenderer(HTMLRendererParameters{
-		Flags: UseXHTML,
-	})
-
-	// set up the parser
-	return Markdown(input, renderer, Options{})
-}
-
-// MarkdownCommon is a convenience function for simple rendering. It calls
-// Markdown with most useful extensions enabled, including:
-//
-// * Smartypants processing with smart fractions and LaTeX dashes
-//
-// * Intra-word emphasis suppression
-//
-// * Tables
-//
-// * Fenced code blocks
-//
-// * Autolinking
-//
-// * Strikethrough support
-//
-// * Strict header parsing
-//
-// * Custom Header IDs
-func MarkdownCommon(input []byte) []byte {
-	// set up the HTML renderer
-	renderer := NewHTMLRenderer(HTMLRendererParameters{
-		Flags: CommonHTMLFlags,
-	})
-	return Markdown(input, renderer, DefaultOptions)
-}
-
-// Markdown is the main rendering function.
-// It parses and renders a block of markdown-encoded text.
-// The supplied Renderer is used to format the output, and extensions dictates
-// which non-standard extensions are enabled.
-//
-// To use the supplied HTML renderer, see NewHTMLRenderer.
-func Markdown(input []byte, renderer Renderer, options Options) []byte {
-	if renderer == nil {
-		return nil
+// DefaultProcessor creates the processor tuned to the most common behavior.
+func DefaultProcessor() *Processor {
+	return &Processor{
+		r: NewHTMLRenderer(HTMLRendererParameters{
+			Flags: CommonHTMLFlags,
+		}),
+		extensions: CommonExtensions,
 	}
-	return renderer.Render(Parse(input, options))
 }
 
-// Parse is an entry point to the parsing part of Blackfriday. It takes an
-// input markdown document and produces a syntax tree for its contents. This
-// tree can then be rendered with a default or custom renderer, or
-// analyzed/transformed by the caller to whatever non-standard needs they have.
-func Parse(input []byte, opts Options) *Node {
-	extensions := opts.Extensions
-
-	// fill in the render structure
-	p := new(parser)
-	p.flags = extensions
-	p.refOverride = opts.ReferenceOverride
+// NewParser constructs a Parser. You can use the same With* functions as for
+// Markdown() to customize parser's behavior.
+func (proc *Processor) NewParser(opts ...Option) *Parser {
+	for _, opt := range opts {
+		opt(proc)
+	}
+	var p Parser
+	p.flags = proc.extensions
+	p.refOverride = proc.referenceOverride
 	p.refs = make(map[string]*reference)
 	p.maxNesting = 16
 	p.insideLink = false
-
 	docNode := NewNode(Document)
 	p.doc = docNode
 	p.tip = docNode
 	p.oldTip = docNode
 	p.lastMatchedContainer = docNode
 	p.allClosed = true
-
 	// register inline parsers
 	p.inlineCallback[' '] = maybeLineBreak
 	p.inlineCallback['*'] = emphasis
 	p.inlineCallback['_'] = emphasis
-	if extensions&Strikethrough != 0 {
+	if proc.extensions&Strikethrough != 0 {
 		p.inlineCallback['~'] = emphasis
 	}
 	p.inlineCallback['`'] = codeSpan
@@ -371,8 +309,7 @@ func Parse(input []byte, opts Options) *Node {
 	p.inlineCallback['&'] = entity
 	p.inlineCallback['!'] = maybeImage
 	p.inlineCallback['^'] = maybeInlineFootnote
-
-	if extensions&Autolink != 0 {
+	if proc.extensions&Autolink != 0 {
 		p.inlineCallback['h'] = maybeAutoLink
 		p.inlineCallback['m'] = maybeAutoLink
 		p.inlineCallback['f'] = maybeAutoLink
@@ -380,11 +317,90 @@ func Parse(input []byte, opts Options) *Node {
 		p.inlineCallback['M'] = maybeAutoLink
 		p.inlineCallback['F'] = maybeAutoLink
 	}
-
-	if extensions&Footnotes != 0 {
+	if proc.extensions&Footnotes != 0 {
 		p.notes = make([]*reference, 0)
 	}
+	return &p
+}
 
+// Option customizes Processor's default behavior.
+type Option func(*Processor)
+
+// WithRenderer allows you to override the default renderer.
+func WithRenderer(r Renderer) Option {
+	return func(p *Processor) {
+		p.r = r
+	}
+}
+
+// WithExtensions allows you to pick some of the many extensions provided by
+// Blackfriday. You can bitwise OR them.
+func WithExtensions(e Extensions) Option {
+	return func(p *Processor) {
+		p.extensions = e
+	}
+}
+
+// WithNoExtensions turns off all extensions and custom behavior.
+func WithNoExtensions() Option {
+	return func(p *Processor) {
+		p.extensions = NoExtensions
+		p.r = NewHTMLRenderer(HTMLRendererParameters{
+			Flags: HTMLFlagsNone,
+		})
+	}
+}
+
+// WithRefOverride sets an optional function callback that is called every
+// time a reference is resolved.
+//
+// In Markdown, the link reference syntax can be made to resolve a link to
+// a reference instead of an inline URL, in one of the following ways:
+//
+//  * [link text][refid]
+//  * [refid][]
+//
+// Usually, the refid is defined at the bottom of the Markdown document. If
+// this override function is provided, the refid is passed to the override
+// function first, before consulting the defined refids at the bottom. If
+// the override function indicates an override did not occur, the refids at
+// the bottom will be used to fill in the link details.
+func WithRefOverride(o ReferenceOverrideFunc) Option {
+	return func(p *Processor) {
+		p.referenceOverride = o
+	}
+}
+
+// Markdown is the main entry point to Blackfriday. It parses and renders a
+// block of markdown-encoded text.
+//
+// The simplest invocation of Markdown takes one argument, input:
+//     output := Markdown(input)
+// This will parse the input with CommonExtensions enabled and render it with
+// the default HTMLRenderer (with CommonHTMLFlags).
+//
+// Variadic arguments opts can customize the default behavior. Since Processor
+// type does not contain exported fields, you can not use it directly. Instead,
+// use the With* functions. For example, this will call the most basic
+// functionality, with no extensions:
+//     output := Markdown(input, WithNoExtensions())
+//
+// You can use any number of With* arguments, even contradicting ones. They
+// will be applied in order of appearance and the latter will override the
+// former:
+//     output := Markdown(input, WithNoExtensions(), WithExtensions(exts),
+//         WithRenderer(yourRenderer))
+func Markdown(input []byte, opts ...Option) []byte {
+	p := DefaultProcessor()
+	parser := p.NewParser(opts...)
+	return p.r.Render(parser.Parse(input))
+}
+
+// Parse is an entry point to the parsing part of Blackfriday. It takes an
+// input markdown document and produces a syntax tree for its contents. This
+// tree can then be rendered with a default or custom renderer, or
+// analyzed/transformed by the caller to whatever non-standard needs they have.
+func (p *Parser) Parse(input []byte) *Node {
 	p.block(input)
 	// Walk the tree and finish up some of unfinished blocks
 	for p.tip != nil {
@@ -402,7 +418,7 @@ func Parse(input []byte, opts Options) *Node {
 	return p.doc
 }
 
-func (p *parser) parseRefsToAST() {
+func (p *Parser) parseRefsToAST() {
 	if p.flags&Footnotes == 0 || len(p.notes) == 0 {
 		return
 	}
@@ -527,7 +543,7 @@ func (r *reference) String() string {
 // (in the render struct).
 // Returns the number of bytes to skip to move past it,
 // or zero if the first line is not a reference.
-func isReference(p *parser, data []byte, tabSize int) int {
+func isReference(p *Parser, data []byte, tabSize int) int {
 	// up to 3 optional leading spaces
 	if len(data) < 4 {
 		return 0
@@ -630,7 +646,7 @@ func isReference(p *parser, data []byte, tabSize int) int {
 	return lineEnd
 }
 
-func scanLinkRef(p *parser, data []byte, i int) (linkOffset, linkEnd, titleOffset, titleEnd, lineEnd int) {
+func scanLinkRef(p *Parser, data []byte, i int) (linkOffset, linkEnd, titleOffset, titleEnd, lineEnd int) {
 	// link: whitespace-free sequence, optionally between angle brackets
 	if data[i] == '<' {
 		i++
@@ -701,13 +717,13 @@ func scanLinkRef(p *parser, data []byte, i int) (linkOffset, linkEnd, titleOffse
 	return
 }
 
-// The first bit of this logic is the same as (*parser).listItem, but the rest
+// The first bit of this logic is the same as Parser.listItem, but the rest
 // is much simpler. This function simply finds the entire block and shifts it
 // over by one tab if it is indeed a block (just returns the line if it's not).
 // blockEnd is the end of the section in the input buffer, and contents is the
 // extracted text that was shifted over one tab. It will need to be rendered at
 // the end of the document.
-func scanFootnote(p *parser, data []byte, i, indentSize int) (blockStart, blockEnd int, contents []byte, hasBlock bool) {
+func scanFootnote(p *Parser, data []byte, i, indentSize int) (blockStart, blockEnd int, contents []byte, hasBlock bool) {
 	if i == 0 || len(data) == 0 {
 		return
 	}
diff --git a/ref_test.go b/ref_test.go
index a9b63d9..4375f54 100644
--- a/ref_test.go
+++ b/ref_test.go
@@ -80,7 +80,7 @@ func TestReference_EXTENSION_NO_EMPTY_LINE_BEFORE_BLOCK(t *testing.T) {
 var benchResultAnchor string
 
 func BenchmarkReference(b *testing.B) {
-	params := TestParams{Options: Options{Extensions: CommonExtensions}}
+	params := TestParams{extensions: CommonExtensions}
 	files := []string{
 		"Amps and angle encoding",
 		"Auto links",