go.tools/godoc/present: move present package from go.talks

Godoc depends on go.talks/pkg/present by way of go.tools/pkg/blog.
Better to keep all godoc dependencies in one place.

R=golang-dev, dsymonds, r
CC=golang-dev
https://golang.org/cl/13656047

present/args.go

@@ -0,0 +1,229 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package present
+
+import (
+	"errors"
+	"regexp"
+	"strconv"
+	"unicode/utf8"
+)
+
+// This file is stolen from go/src/cmd/godoc/codewalk.go.
+// It's an evaluator for the file address syntax implemented by acme and sam,
+// but using Go-native regular expressions.
+// To keep things reasonably close, this version uses (?m:re) for all user-provided
+// regular expressions. That is the only change to the code from codewalk.go.
+// See http://plan9.bell-labs.com/sys/doc/sam/sam.html Table II
+// for details on the syntax.
+
+// addrToByte evaluates the given address starting at offset start in data.
+// It returns the lo and hi byte offset of the matched region within data.
+func addrToByteRange(addr string, start int, data []byte) (lo, hi int, err error) {
+	if addr == "" {
+		lo, hi = start, len(data)
+		return
+	}
+	var (
+		dir        byte
+		prevc      byte
+		charOffset bool
+	)
+	lo = start
+	hi = start
+	for addr != "" && err == nil {
+		c := addr[0]
+		switch c {
+		default:
+			err = errors.New("invalid address syntax near " + string(c))
+		case ',':
+			if len(addr) == 1 {
+				hi = len(data)
+			} else {
+				_, hi, err = addrToByteRange(addr[1:], hi, data)
+			}
+			return
+
+		case '+', '-':
+			if prevc == '+' || prevc == '-' {
+				lo, hi, err = addrNumber(data, lo, hi, prevc, 1, charOffset)
+			}
+			dir = c
+
+		case '$':
+			lo = len(data)
+			hi = len(data)
+			if len(addr) > 1 {
+				dir = '+'
+			}
+
+		case '#':
+			charOffset = true
+
+		case '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
+			var i int
+			for i = 1; i < len(addr); i++ {
+				if addr[i] < '0' || addr[i] > '9' {
+					break
+				}
+			}
+			var n int
+			n, err = strconv.Atoi(addr[0:i])
+			if err != nil {
+				break
+			}
+			lo, hi, err = addrNumber(data, lo, hi, dir, n, charOffset)
+			dir = 0
+			charOffset = false
+			prevc = c
+			addr = addr[i:]
+			continue
+
+		case '/':
+			var i, j int
+		Regexp:
+			for i = 1; i < len(addr); i++ {
+				switch addr[i] {
+				case '\\':
+					i++
+				case '/':
+					j = i + 1
+					break Regexp
+				}
+			}
+			if j == 0 {
+				j = i
+			}
+			pattern := addr[1:i]
+			lo, hi, err = addrRegexp(data, lo, hi, dir, pattern)
+			prevc = c
+			addr = addr[j:]
+			continue
+		}
+		prevc = c
+		addr = addr[1:]
+	}
+
+	if err == nil && dir != 0 {
+		lo, hi, err = addrNumber(data, lo, hi, dir, 1, charOffset)
+	}
+	if err != nil {
+		return 0, 0, err
+	}
+	return lo, hi, nil
+}
+
+// addrNumber applies the given dir, n, and charOffset to the address lo, hi.
+// dir is '+' or '-', n is the count, and charOffset is true if the syntax
+// used was #n.  Applying +n (or +#n) means to advance n lines
+// (or characters) after hi.  Applying -n (or -#n) means to back up n lines
+// (or characters) before lo.
+// The return value is the new lo, hi.
+func addrNumber(data []byte, lo, hi int, dir byte, n int, charOffset bool) (int, int, error) {
+	switch dir {
+	case 0:
+		lo = 0
+		hi = 0
+		fallthrough
+
+	case '+':
+		if charOffset {
+			pos := hi
+			for ; n > 0 && pos < len(data); n-- {
+				_, size := utf8.DecodeRune(data[pos:])
+				pos += size
+			}
+			if n == 0 {
+				return pos, pos, nil
+			}
+			break
+		}
+		// find next beginning of line
+		if hi > 0 {
+			for hi < len(data) && data[hi-1] != '\n' {
+				hi++
+			}
+		}
+		lo = hi
+		if n == 0 {
+			return lo, hi, nil
+		}
+		for ; hi < len(data); hi++ {
+			if data[hi] != '\n' {
+				continue
+			}
+			switch n--; n {
+			case 1:
+				lo = hi + 1
+			case 0:
+				return lo, hi + 1, nil
+			}
+		}
+
+	case '-':
+		if charOffset {
+			// Scan backward for bytes that are not UTF-8 continuation bytes.
+			pos := lo
+			for ; pos > 0 && n > 0; pos-- {
+				if data[pos]&0xc0 != 0x80 {
+					n--
+				}
+			}
+			if n == 0 {
+				return pos, pos, nil
+			}
+			break
+		}
+		// find earlier beginning of line
+		for lo > 0 && data[lo-1] != '\n' {
+			lo--
+		}
+		hi = lo
+		if n == 0 {
+			return lo, hi, nil
+		}
+		for ; lo >= 0; lo-- {
+			if lo > 0 && data[lo-1] != '\n' {
+				continue
+			}
+			switch n--; n {
+			case 1:
+				hi = lo
+			case 0:
+				return lo, hi, nil
+			}
+		}
+	}
+
+	return 0, 0, errors.New("address out of range")
+}
+
+// addrRegexp searches for pattern in the given direction starting at lo, hi.
+// The direction dir is '+' (search forward from hi) or '-' (search backward from lo).
+// Backward searches are unimplemented.
+func addrRegexp(data []byte, lo, hi int, dir byte, pattern string) (int, int, error) {
+	// We want ^ and $ to work as in sam/acme, so use ?m.
+	re, err := regexp.Compile("(?m:" + pattern + ")")
+	if err != nil {
+		return 0, 0, err
+	}
+	if dir == '-' {
+		// Could implement reverse search using binary search
+		// through file, but that seems like overkill.
+		return 0, 0, errors.New("reverse search not implemented")
+	}
+	m := re.FindIndex(data[hi:])
+	if len(m) > 0 {
+		m[0] += hi
+		m[1] += hi
+	} else if hi > 0 {
+		// No match.  Wrap to beginning of data.
+		m = re.FindIndex(data)
+	}
+	if len(m) == 0 {
+		return 0, 0, errors.New("no match for " + pattern)
+	}
+	return m[0], m[1], nil
+}

present/code.go

@@ -0,0 +1,252 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package present
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"html/template"
+	"path/filepath"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+// Is the playground available?
+var PlayEnabled = false
+
+// TOOD(adg): replace the PlayEnabled flag with something less spaghetti-like.
+// Instead this will probably be determined by a template execution Context
+// value that contains various global metadata required when rendering
+// templates.
+
+func init() {
+	Register("code", parseCode)
+	Register("play", parseCode)
+}
+
+type Code struct {
+	Text template.HTML
+	Play bool // runnable code
+}
+
+func (c Code) TemplateName() string { return "code" }
+
+// The input line is a .code or .play entry with a file name and an optional HLfoo marker on the end.
+// Anything between the file and HL (if any) is an address expression, which we treat as a string here.
+// We pick off the HL first, for easy parsing.
+var (
+	highlightRE = regexp.MustCompile(`\s+HL([a-zA-Z0-9_]+)?$`)
+	hlCommentRE = regexp.MustCompile(`(.+) // HL(.*)$`)
+	codeRE      = regexp.MustCompile(`\.(code|play)\s+([^\s]+)(\s+)?(.*)?$`)
+)
+
+func parseCode(ctx *Context, sourceFile string, sourceLine int, cmd string) (Elem, error) {
+	cmd = strings.TrimSpace(cmd)
+
+	// Pull off the HL, if any, from the end of the input line.
+	highlight := ""
+	if hl := highlightRE.FindStringSubmatchIndex(cmd); len(hl) == 4 {
+		highlight = cmd[hl[2]:hl[3]]
+		cmd = cmd[:hl[2]-2]
+	}
+
+	// Parse the remaining command line.
+	// Arguments:
+	// args[0]: whole match
+	// args[1]:  .code/.play
+	// args[2]: file name
+	// args[3]: space, if any, before optional address
+	// args[4]: optional address
+	args := codeRE.FindStringSubmatch(cmd)
+	if len(args) != 5 {
+		return nil, fmt.Errorf("%s:%d: syntax error for .code/.play invocation", sourceFile, sourceLine)
+	}
+	command, file, addr := args[1], args[2], strings.TrimSpace(args[4])
+	play := command == "play" && PlayEnabled
+
+	// Read in code file and (optionally) match address.
+	filename := filepath.Join(filepath.Dir(sourceFile), file)
+	textBytes, err := ctx.ReadFile(filename)
+	if err != nil {
+		return nil, fmt.Errorf("%s:%d: %v", sourceFile, sourceLine, err)
+	}
+	lo, hi, err := addrToByteRange(addr, 0, textBytes)
+	if err != nil {
+		return nil, fmt.Errorf("%s:%d: %v", sourceFile, sourceLine, err)
+	}
+
+	// Acme pattern matches can stop mid-line,
+	// so run to end of line in both directions if not at line start/end.
+	for lo > 0 && textBytes[lo-1] != '\n' {
+		lo--
+	}
+	if hi > 0 {
+		for hi < len(textBytes) && textBytes[hi-1] != '\n' {
+			hi++
+		}
+	}
+
+	lines := codeLines(textBytes, lo, hi)
+
+	for i, line := range lines {
+		// Replace tabs by spaces, which work better in HTML.
+		line.L = strings.Replace(line.L, "\t", "    ", -1)
+
+		// Highlight lines that end with "// HL[highlight]"
+		// and strip the magic comment.
+		if m := hlCommentRE.FindStringSubmatch(line.L); m != nil {
+			line.L = m[1]
+			line.HL = m[2] == highlight
+		}
+
+		lines[i] = line
+	}
+
+	data := &codeTemplateData{Lines: lines}
+
+	// Include before and after in a hidden span for playground code.
+	if play {
+		data.Prefix = textBytes[:lo]
+		data.Suffix = textBytes[hi:]
+	}
+
+	var buf bytes.Buffer
+	if err := codeTemplate.Execute(&buf, data); err != nil {
+		return nil, err
+	}
+	return Code{Text: template.HTML(buf.String()), Play: play}, nil
+}
+
+type codeTemplateData struct {
+	Lines          []codeLine
+	Prefix, Suffix []byte
+}
+
+var leadingSpaceRE = regexp.MustCompile(`^[ \t]*`)
+
+var codeTemplate = template.Must(template.New("code").Funcs(template.FuncMap{
+	"trimSpace":    strings.TrimSpace,
+	"leadingSpace": leadingSpaceRE.FindString,
+}).Parse(codeTemplateHTML))
+
+const codeTemplateHTML = `
+{{with .Prefix}}<pre style="display: none"><span>{{printf "%s" .}}</span></pre>{{end}}
+
+<pre>{{range .Lines}}<span num="{{.N}}">{{/*
+	*/}}{{if .HL}}{{leadingSpace .L}}<b>{{trimSpace .L}}</b>{{/*
+	*/}}{{else}}{{.L}}{{end}}{{/*
+*/}}</span>
+{{end}}</pre>
+
+{{with .Suffix}}<pre style="display: none"><span>{{printf "%s" .}}</span></pre>{{end}}
+`
+
+// codeLine represents a line of code extracted from a source file.
+type codeLine struct {
+	L  string // The line of code.
+	N  int    // The line number from the source file.
+	HL bool   // Whether the line should be highlighted.
+}
+
+// codeLines takes a source file and returns the lines that
+// span the byte range specified by start and end.
+// It discards lines that end in "OMIT".
+func codeLines(src []byte, start, end int) (lines []codeLine) {
+	startLine := 1
+	for i, b := range src {
+		if i == start {
+			break
+		}
+		if b == '\n' {
+			startLine++
+		}
+	}
+	s := bufio.NewScanner(bytes.NewReader(src[start:end]))
+	for n := startLine; s.Scan(); n++ {
+		l := s.Text()
+		if strings.HasSuffix(l, "OMIT") {
+			continue
+		}
+		lines = append(lines, codeLine{L: l, N: n})
+	}
+	// Trim leading and trailing blank lines.
+	for len(lines) > 0 && len(lines[0].L) == 0 {
+		lines = lines[1:]
+	}
+	for len(lines) > 0 && len(lines[len(lines)-1].L) == 0 {
+		lines = lines[:len(lines)-1]
+	}
+	return
+}
+
+func parseArgs(name string, line int, args []string) (res []interface{}, err error) {
+	res = make([]interface{}, len(args))
+	for i, v := range args {
+		if len(v) == 0 {
+			return nil, fmt.Errorf("%s:%d bad code argument %q", name, line, v)
+		}
+		switch v[0] {
+		case '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
+			n, err := strconv.Atoi(v)
+			if err != nil {
+				return nil, fmt.Errorf("%s:%d bad code argument %q", name, line, v)
+			}
+			res[i] = n
+		case '/':
+			if len(v) < 2 || v[len(v)-1] != '/' {
+				return nil, fmt.Errorf("%s:%d bad code argument %q", name, line, v)
+			}
+			res[i] = v
+		case '$':
+			res[i] = "$"
+		default:
+			return nil, fmt.Errorf("%s:%d bad code argument %q", name, line, v)
+		}
+	}
+	return
+}
+
+// parseArg returns the integer or string value of the argument and tells which it is.
+func parseArg(arg interface{}, max int) (ival int, sval string, isInt bool, err error) {
+	switch n := arg.(type) {
+	case int:
+		if n <= 0 || n > max {
+			return 0, "", false, fmt.Errorf("%d is out of range", n)
+		}
+		return n, "", true, nil
+	case string:
+		return 0, n, false, nil
+	}
+	return 0, "", false, fmt.Errorf("unrecognized argument %v type %T", arg, arg)
+}
+
+// match identifies the input line that matches the pattern in a code invocation.
+// If start>0, match lines starting there rather than at the beginning.
+// The return value is 1-indexed.
+func match(file string, start int, lines []string, pattern string) (int, error) {
+	// $ matches the end of the file.
+	if pattern == "$" {
+		if len(lines) == 0 {
+			return 0, fmt.Errorf("%q: empty file", file)
+		}
+		return len(lines), nil
+	}
+	// /regexp/ matches the line that matches the regexp.
+	if len(pattern) > 2 && pattern[0] == '/' && pattern[len(pattern)-1] == '/' {
+		re, err := regexp.Compile(pattern[1 : len(pattern)-1])
+		if err != nil {
+			return 0, err
+		}
+		for i := start; i < len(lines); i++ {
+			if re.MatchString(lines[i]) {
+				return i + 1, nil
+			}
+		}
+		return 0, fmt.Errorf("%s: no match for %#q", file, pattern)
+	}
+	return 0, fmt.Errorf("unrecognized pattern: %q", pattern)
+}

present/code.go.orig

@@ -0,0 +1,252 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package present
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"html/template"
+	"path/filepath"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+// Is the playground available?
+var PlayEnabled = false
+
+// TOOD(adg): replace the PlayEnabled flag with something less spaghetti-like.
+// Instead this will probably be determined by a template execution Context
+// value that contains various global metadata required when rendering
+// templates.
+
+func init() {
+	Register("code", parseCode)
+	Register("play", parseCode)
+}
+
+type Code struct {
+	Text template.HTML
+	Play bool // runnable code
+}
+
+func (c Code) TemplateName() string { return "code" }
+
+// The input line is a .code or .play entry with a file name and an optional HLfoo marker on the end.
+// Anything between the file and HL (if any) is an address expression, which we treat as a string here.
+// We pick off the HL first, for easy parsing.
+var (
+	highlightRE = regexp.MustCompile(`\s+HL([a-zA-Z0-9_]+)?$`)
+	hlCommentRE = regexp.MustCompile(`(.+) // HL(.*)$`)
+	codeRE      = regexp.MustCompile(`\.(code|play)\s+([^\s]+)(\s+)?(.*)?$`)
+)
+
+func parseCode(ctx *Context, sourceFile string, sourceLine int, cmd string) (Elem, error) {
+	cmd = strings.TrimSpace(cmd)
+
+	// Pull off the HL, if any, from the end of the input line.
+	highlight := ""
+	if hl := highlightRE.FindStringSubmatchIndex(cmd); len(hl) == 4 {
+		highlight = cmd[hl[2]:hl[3]]
+		cmd = cmd[:hl[2]-2]
+	}
+
+	// Parse the remaining command line.
+	// Arguments:
+	// args[0]: whole match
+	// args[1]:  .code/.play
+	// args[2]: file name
+	// args[3]: space, if any, before optional address
+	// args[4]: optional address
+	args := codeRE.FindStringSubmatch(cmd)
+	if len(args) != 5 {
+		return nil, fmt.Errorf("%s:%d: syntax error for .code/.play invocation", sourceFile, sourceLine)
+	}
+	command, file, addr := args[1], args[2], strings.TrimSpace(args[4])
+	play := command == "play" && PlayEnabled
+
+	// Read in code file and (optionally) match address.
+	filename := filepath.Join(filepath.Dir(sourceFile), file)
+	textBytes, err := ctx.ReadFile(filename)
+	if err != nil {
+		return nil, fmt.Errorf("%s:%d: %v", sourceFile, sourceLine, err)
+	}
+	lo, hi, err := addrToByteRange(addr, 0, textBytes)
+	if err != nil {
+		return nil, fmt.Errorf("%s:%d: %v", sourceFile, sourceLine, err)
+	}
+
+	// Acme pattern matches can stop mid-line,
+	// so run to end of line in both directions if not at line start/end.
+	for lo > 0 && textBytes[lo-1] != '\n' {
+		lo--
+	}
+	if hi > 0 {
+		for hi < len(textBytes) && textBytes[hi-1] != '\n' {
+			hi++
+		}
+	}
+
+	lines := codeLines(textBytes, lo, hi)
+
+	for i, line := range lines {
+		// Replace tabs by spaces, which work better in HTML.
+		line.L = strings.Replace(line.L, "\t", "    ", -1)
+
+		// Highlight lines that end with "// HL[highlight]"
+		// and strip the magic comment.
+		if m := hlCommentRE.FindStringSubmatch(line.L); m != nil {
+			line.L = m[1]
+			line.HL = m[2] == highlight
+		}
+
+		lines[i] = line
+	}
+
+	data := &codeTemplateData{Lines: lines}
+
+	// Include before and after in a hidden span for playground code.
+	if play {
+		data.Prefix = textBytes[:lo]
+		data.Suffix = textBytes[hi:]
+	}
+
+	var buf bytes.Buffer
+	if err := codeTemplate.Execute(&buf, data); err != nil {
+		return nil, err
+	}
+	return Code{Text: template.HTML(buf.String()), Play: play}, nil
+}
+
+type codeTemplateData struct {
+	Lines          []codeLine
+	Prefix, Suffix []byte
+}
+
+var leadingSpaceRE = regexp.MustCompile(`^[ \t]*`)
+
+var codeTemplate = template.Must(template.New("code").Funcs(template.FuncMap{
+	"trimSpace":    strings.TrimSpace,
+	"leadingSpace": leadingSpaceRE.FindString,
+}).Parse(codeTemplateHTML))
+
+const codeTemplateHTML = `
+{{with .Prefix}}<pre style="display: none"><span>{{printf "%s" .}}</span></pre>{{end}}
+
+<pre>{{range .Lines}}<span num="{{.N}}"{{if .HL}} class="hl"{{end}}>{{/*
+	*/}}{{if .HL}}{{leadingSpace .L}}<b>{{trimSpace .L}}</b>{{/*
+	*/}}{{else}}{{.L}}{{end}}{{/*
+*/}}</span>
+{{end}}</pre>
+
+{{with .Suffix}}<pre style="display: none"><span>{{printf "%s" .}}</span></pre>{{end}}
+`
+
+// codeLine represents a line of code extracted from a source file.
+type codeLine struct {
+	L  string // The line of code.
+	N  int    // The line number from the source file.
+	HL bool   // Whether the line should be highlighted.
+}
+
+// codeLines takes a source file and returns the lines that
+// span the byte range specified by start and end.
+// It discards lines that end in "OMIT".
+func codeLines(src []byte, start, end int) (lines []codeLine) {
+	startLine := 1
+	for i, b := range src {
+		if i == start {
+			break
+		}
+		if b == '\n' {
+			startLine++
+		}
+	}
+	s := bufio.NewScanner(bytes.NewReader(src[start:end]))
+	for n := startLine; s.Scan(); n++ {
+		l := s.Text()
+		if strings.HasSuffix(l, "OMIT") {
+			continue
+		}
+		lines = append(lines, codeLine{L: l, N: n})
+	}
+	// Trim leading and trailing blank lines.
+	for len(lines) > 0 && len(lines[0].L) == 0 {
+		lines = lines[1:]
+	}
+	for len(lines) > 0 && len(lines[len(lines)-1].L) == 0 {
+		lines = lines[:len(lines)-1]
+	}
+	return
+}
+
+func parseArgs(name string, line int, args []string) (res []interface{}, err error) {
+	res = make([]interface{}, len(args))
+	for i, v := range args {
+		if len(v) == 0 {
+			return nil, fmt.Errorf("%s:%d bad code argument %q", name, line, v)
+		}
+		switch v[0] {
+		case '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
+			n, err := strconv.Atoi(v)
+			if err != nil {
+				return nil, fmt.Errorf("%s:%d bad code argument %q", name, line, v)
+			}
+			res[i] = n
+		case '/':
+			if len(v) < 2 || v[len(v)-1] != '/' {
+				return nil, fmt.Errorf("%s:%d bad code argument %q", name, line, v)
+			}
+			res[i] = v
+		case '$':
+			res[i] = "$"
+		default:
+			return nil, fmt.Errorf("%s:%d bad code argument %q", name, line, v)
+		}
+	}
+	return
+}
+
+// parseArg returns the integer or string value of the argument and tells which it is.
+func parseArg(arg interface{}, max int) (ival int, sval string, isInt bool, err error) {
+	switch n := arg.(type) {
+	case int:
+		if n <= 0 || n > max {
+			return 0, "", false, fmt.Errorf("%d is out of range", n)
+		}
+		return n, "", true, nil
+	case string:
+		return 0, n, false, nil
+	}
+	return 0, "", false, fmt.Errorf("unrecognized argument %v type %T", arg, arg)
+}
+
+// match identifies the input line that matches the pattern in a code invocation.
+// If start>0, match lines starting there rather than at the beginning.
+// The return value is 1-indexed.
+func match(file string, start int, lines []string, pattern string) (int, error) {
+	// $ matches the end of the file.
+	if pattern == "$" {
+		if len(lines) == 0 {
+			return 0, fmt.Errorf("%q: empty file", file)
+		}
+		return len(lines), nil
+	}
+	// /regexp/ matches the line that matches the regexp.
+	if len(pattern) > 2 && pattern[0] == '/' && pattern[len(pattern)-1] == '/' {
+		re, err := regexp.Compile(pattern[1 : len(pattern)-1])
+		if err != nil {
+			return 0, err
+		}
+		for i := start; i < len(lines); i++ {
+			if re.MatchString(lines[i]) {
+				return i + 1, nil
+			}
+		}
+		return 0, fmt.Errorf("%s: no match for %#q", file, pattern)
+	}
+	return 0, fmt.Errorf("unrecognized pattern: %q", pattern)
+}

present/doc.go

@@ -0,0 +1,184 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+/*
+The present file format
+
+Present files have the following format.  The first non-blank non-comment
+line is the title, so the header looks like
+
+	Title of document
+	Subtitle of document
+	15:04 2 Jan 2006
+	Tags: foo, bar, baz
+	<blank line>
+	Author Name
+	Job title, Company
+	joe@example.com
+	http://url/
+	@twitter_name
+
+The subtitle, date, and tags lines are optional.
+
+The date line may be written without a time:
+	2 Jan 2006
+In this case, the time will be interpreted as 10am UTC on that date.
+
+The tags line is a comma-separated list of tags that may be used to categorize
+the document.
+
+The author section may contain a mixture of text, twitter names, and links.
+For slide presentations, only the plain text lines will be displayed on the
+first slide.
+
+Multiple presenters may be specified, separated by a blank line.
+
+After that come slides/sections, each after a blank line:
+
+	* Title of slide or section (must have asterisk)
+
+	Some Text
+
+	** Subsection
+
+	- bullets
+	- more bullets
+	- a bullet with
+
+	*** Sub-subsection
+
+	Some More text
+
+	  Preformatted text
+	  is indented (however you like)
+
+	Further Text, including invocations like:
+
+	.code x.go /^func main/,/^}/
+	.play y.go
+	.image image.jpg
+	.iframe http://foo
+	.link http://foo label
+	.html file.html
+
+	Again, more text
+
+Blank lines are OK (not mandatory) after the title and after the
+text.  Text, bullets, and .code etc. are all optional; title is
+not.
+
+Lines starting with # in column 1 are commentary.
+
+Fonts:
+
+Within the input for plain text or lists, text bracketed by font
+markers will be presented in italic, bold, or program font.
+Marker characters are _ (italic), * (bold) and ` (program font).
+Unmatched markers appear as plain text.
+Within marked text, a single marker character becomes a space
+and a doubled single marker quotes the marker character.
+
+	_italic_
+	*bold*
+	`program`
+	_this_is_all_italic_
+	_Why_use_scoped__ptr_? Use plain ***ptr* instead.
+
+Inline links:
+
+Links can be included in any text with the form [[url][label]], or
+[[url]] to use the URL itself as the label.
+
+Functions:
+
+A number of template functions are available through invocations
+in the input text. Each such invocation contains a period as the
+first character on the line, followed immediately by the name of
+the function, followed by any arguments. A typical invocation might
+be
+	.play demo.go /^func show/,/^}/
+(except that the ".play" must be at the beginning of the line and
+not be indented like this.)
+
+Here follows a description of the functions:
+
+code:
+
+Injects program source into the output by extracting code from files
+and injecting them as HTML-escaped <pre> blocks.  The argument is
+a file name followed by an optional address that specifies what
+section of the file to display. The address syntax is similar in
+its simplest form to that of ed, but comes from sam and is more
+general. See
+	http://plan9.bell-labs.com/sys/doc/sam/sam.html Table II
+for full details. The displayed block is always rounded out to a
+full line at both ends.
+
+If no pattern is present, the entire file is displayed.
+
+Any line in the program that ends with the four characters
+	OMIT
+is deleted from the source before inclusion, making it easy
+to write things like
+	.code test.go /START OMIT/,/END OMIT/
+to find snippets like this
+	tedious_code = boring_function()
+	// START OMIT
+	interesting_code = fascinating_function()
+	// END OMIT
+and see only this:
+	interesting_code = fascinating_function()
+
+Also, inside the displayed text a line that ends
+	// HL
+will be highlighted in the display; the 'h' key in the browser will
+toggle extra emphasis of any highlighted lines. A highlighting mark
+may have a suffix word, such as
+	// HLxxx
+Such highlights are enabled only if the code invocation ends with
+"HL" followed by the word:
+	.code test.go /^type Foo/,/^}/ HLxxx
+
+play:
+
+The function "play" is the same as "code" but puts a button
+on the displayed source so the program can be run from the browser.
+Although only the selected text is shown, all the source is included
+in the HTML output so it can be presented to the compiler.
+
+link:
+
+Create a hyperlink. The syntax is 1 or 2 space-separated arguments.
+The first argument is always the HTTP URL.  If there is a second
+argument, it is the text label to display for this link.
+
+	.link http://golang.org golang.org
+
+image:
+
+The template uses the function "image" to inject picture files.
+
+The syntax is simple: 1 or 3 space-separated arguments.
+The first argument is always the file name.
+If there are more arguments, they are the height and width;
+both must be present.
+
+	.image images/betsy.jpg 100 200
+
+iframe:
+
+The function "iframe" injects iframes (pages inside pages).
+Its syntax is the same as that of image.
+
+html:
+
+The function html includes the contents of the specified file as
+unescaped HTML. This is useful for including custom HTML elements
+that cannot be created using only the slide format.
+It is your responsibilty to make sure the included HTML is valid and safe.
+
+	.html file.html
+
+*/
+package present

present/html.go

@@ -0,0 +1,31 @@
+package present
+
+import (
+	"errors"
+	"html/template"
+	"path/filepath"
+	"strings"
+)
+
+func init() {
+	Register("html", parseHTML)
+}
+
+func parseHTML(ctx *Context, fileName string, lineno int, text string) (Elem, error) {
+	p := strings.Fields(text)
+	if len(p) != 2 {
+		return nil, errors.New("invalid .html args")
+	}
+	name := filepath.Join(filepath.Dir(fileName), p[1])
+	b, err := ctx.ReadFile(name)
+	if err != nil {
+		return nil, err
+	}
+	return HTML{template.HTML(b)}, nil
+}
+
+type HTML struct {
+	template.HTML
+}
+
+func (s HTML) TemplateName() string { return "html" }

present/iframe.go

@@ -0,0 +1,45 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package present
+
+import (
+	"fmt"
+	"strings"
+)
+
+func init() {
+	Register("iframe", parseIframe)
+}
+
+type Iframe struct {
+	URL    string
+	Width  int
+	Height int
+}
+
+func (i Iframe) TemplateName() string { return "iframe" }
+
+func parseIframe(ctx *Context, fileName string, lineno int, text string) (Elem, error) {
+	args := strings.Fields(text)
+	i := Iframe{URL: args[1]}
+	a, err := parseArgs(fileName, lineno, args[2:])
+	if err != nil {
+		return nil, err
+	}
+	switch len(a) {
+	case 0:
+		// no size parameters
+	case 2:
+		if v, ok := a[0].(int); ok {
+			i.Height = v
+		}
+		if v, ok := a[1].(int); ok {
+			i.Width = v
+		}
+	default:
+		return nil, fmt.Errorf("incorrect image invocation: %q", text)
+	}
+	return i, nil
+}

present/image.go

@@ -0,0 +1,45 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package present
+
+import (
+	"fmt"
+	"strings"
+)
+
+func init() {
+	Register("image", parseImage)
+}
+
+type Image struct {
+	URL    string
+	Width  int
+	Height int
+}
+
+func (i Image) TemplateName() string { return "image" }
+
+func parseImage(ctx *Context, fileName string, lineno int, text string) (Elem, error) {
+	args := strings.Fields(text)
+	img := Image{URL: args[1]}
+	a, err := parseArgs(fileName, lineno, args[2:])
+	if err != nil {
+		return nil, err
+	}
+	switch len(a) {
+	case 0:
+		// no size parameters
+	case 2:
+		if v, ok := a[0].(int); ok {
+			img.Height = v
+		}
+		if v, ok := a[1].(int); ok {
+			img.Width = v
+		}
+	default:
+		return nil, fmt.Errorf("incorrect image invocation: %q", text)
+	}
+	return img, nil
+}

present/link.go

@@ -0,0 +1,88 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package present
+
+import (
+	"fmt"
+	"net/url"
+	"strings"
+)
+
+func init() {
+	Register("link", parseLink)
+}
+
+type Link struct {
+	URL   *url.URL
+	Label string
+}
+
+func (l Link) TemplateName() string { return "link" }
+
+func parseLink(ctx *Context, fileName string, lineno int, text string) (Elem, error) {
+	args := strings.Fields(text)
+	url, err := url.Parse(args[1])
+	if err != nil {
+		return nil, err
+	}
+	label := ""
+	if len(args) > 2 {
+		label = strings.Join(args[2:], " ")
+	} else {
+		scheme := url.Scheme + "://"
+		if url.Scheme == "mailto" {
+			scheme = "mailto:"
+		}
+		label = strings.Replace(url.String(), scheme, "", 1)
+	}
+	return Link{url, label}, nil
+}
+
+func renderLink(url, text string) string {
+	text = font(text)
+	if text == "" {
+		text = url
+	}
+	return fmt.Sprintf(`<a href="%s" target="_blank">%s</a>`, url, text)
+}
+
+// parseInlineLink parses an inline link at the start of s, and returns
+// a rendered HTML link and the total length of the raw inline link.
+// If no inline link is present, it returns all zeroes.
+func parseInlineLink(s string) (link string, length int) {
+	if !strings.HasPrefix(s, "[[") {
+		return
+	}
+	end := strings.Index(s, "]]")
+	if end == -1 {
+		return
+	}
+	urlEnd := strings.Index(s, "]")
+	rawURL := s[2:urlEnd]
+	const badURLChars = `<>"{}|\^[] ` + "`" // per RFC2396 section 2.4.3
+	if strings.ContainsAny(rawURL, badURLChars) {
+		return
+	}
+	if urlEnd == end {
+		simpleUrl := ""
+		url, err := url.Parse(rawURL)
+		if err == nil {
+			// If the URL is http://foo.com, drop the http://
+			// In other words, render [[http://golang.org]] as:
+			//   <a href="http://golang.org">golang.org</a>
+			if strings.HasPrefix(rawURL, url.Scheme+"://") {
+				simpleUrl = strings.TrimPrefix(rawURL, url.Scheme+"://")
+			} else if strings.HasPrefix(rawURL, url.Scheme+":") {
+				simpleUrl = strings.TrimPrefix(rawURL, url.Scheme+":")
+			}
+		}
+		return renderLink(rawURL, simpleUrl), end + 2
+	}
+	if s[urlEnd:urlEnd+2] != "][" {
+		return
+	}
+	text := s[urlEnd+2 : end]
+	return renderLink(rawURL, text), end + 2
+}

present/link_test.go

@@ -0,0 +1,40 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package present
+
+import "testing"
+
+func TestInlineParsing(t *testing.T) {
+	var tests = []struct {
+		in     string
+		link   string
+		text   string
+		length int
+	}{
+		{"[[http://golang.org]]", "http://golang.org", "golang.org", 21},
+		{"[[http://golang.org][]]", "http://golang.org", "http://golang.org", 23},
+		{"[[http://golang.org]] this is ignored", "http://golang.org", "golang.org", 21},
+		{"[[http://golang.org][link]]", "http://golang.org", "link", 27},
+		{"[[http://golang.org][two words]]", "http://golang.org", "two words", 32},
+		{"[[http://golang.org][*link*]]", "http://golang.org", "<b>link</b>", 29},
+		{"[[http://bad[url]]", "", "", 0},
+		{"[[http://golang.org][a [[link]] ]]", "http://golang.org", "a [[link", 31},
+		{"[[http:// *spaces* .com]]", "", "", 0},
+		{"[[http://bad`char.com]]", "", "", 0},
+		{" [[http://google.com]]", "", "", 0},
+		{"[[mailto:gopher@golang.org][Gopher]]", "mailto:gopher@golang.org", "Gopher", 36},
+		{"[[mailto:gopher@golang.org]]", "mailto:gopher@golang.org", "gopher@golang.org", 28},
+	}
+
+	for i, test := range tests {
+		link, length := parseInlineLink(test.in)
+		if length == 0 && test.length == 0 {
+			continue
+		}
+		if a := renderLink(test.link, test.text); length != test.length || link != a {
+			t.Errorf("#%d: parseInlineLink(%q):\ngot\t%q, %d\nwant\t%q, %d", i, test.in, link, length, a, test.length)
+		}
+	}
+}

present/parse.go

@@ -0,0 +1,495 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package present
+
+import (
+	"bufio"
+	"bytes"
+	"errors"
+	"fmt"
+	"html/template"
+	"io"
+	"io/ioutil"
+	"log"
+	"net/url"
+	"regexp"
+	"strings"
+	"time"
+	"unicode"
+	"unicode/utf8"
+)
+
+var (
+	parsers = make(map[string]ParseFunc)
+	funcs   = template.FuncMap{}
+)
+
+// Template returns an empty template with the action functions in its FuncMap.
+func Template() *template.Template {
+	return template.New("").Funcs(funcs)
+}
+
+// Render renders the doc to the given writer using the provided template.
+func (d *Doc) Render(w io.Writer, t *template.Template) error {
+	data := struct {
+		*Doc
+		Template    *template.Template
+		PlayEnabled bool
+	}{d, t, PlayEnabled}
+	return t.ExecuteTemplate(w, "root", data)
+}
+
+type ParseFunc func(ctx *Context, fileName string, lineNumber int, inputLine string) (Elem, error)
+
+// Register binds the named action, which does not begin with a period, to the
+// specified parser to be invoked when the name, with a period, appears in the
+// present input text.
+func Register(name string, parser ParseFunc) {
+	if len(name) == 0 || name[0] == ';' {
+		panic("bad name in Register: " + name)
+	}
+	parsers["."+name] = parser
+}
+
+// Doc represents an entire document.
+type Doc struct {
+	Title    string
+	Subtitle string
+	Time     time.Time
+	Authors  []Author
+	Sections []Section
+	Tags     []string
+}
+
+// Author represents the person who wrote and/or is presenting the document.
+type Author struct {
+	Elem []Elem
+}
+
+// TextElem returns the first text elements of the author details.
+// This is used to display the author' name, job title, and company
+// without the contact details.
+func (p *Author) TextElem() (elems []Elem) {
+	for _, el := range p.Elem {
+		if _, ok := el.(Text); !ok {
+			break
+		}
+		elems = append(elems, el)
+	}
+	return
+}
+
+// Section represents a section of a document (such as a presentation slide)
+// comprising a title and a list of elements.
+type Section struct {
+	Number []int
+	Title  string
+	Elem   []Elem
+}
+
+func (s Section) Sections() (sections []Section) {
+	for _, e := range s.Elem {
+		if section, ok := e.(Section); ok {
+			sections = append(sections, section)
+		}
+	}
+	return
+}
+
+// Level returns the level of the given section.
+// The document title is level 1, main section 2, etc.
+func (s Section) Level() int {
+	return len(s.Number) + 1
+}
+
+// FormattedNumber returns a string containing the concatenation of the
+// numbers identifying a Section.
+func (s Section) FormattedNumber() string {
+	b := &bytes.Buffer{}
+	for _, n := range s.Number {
+		fmt.Fprintf(b, "%v.", n)
+	}
+	return b.String()
+}
+
+func (s Section) TemplateName() string { return "section" }
+
+// Elem defines the interface for a present element. That is, something that
+// can provide the name of the template used to render the element.
+type Elem interface {
+	TemplateName() string
+}
+
+// renderElem implements the elem template function, used to render
+// sub-templates.
+func renderElem(t *template.Template, e Elem) (template.HTML, error) {
+	var data interface{} = e
+	if s, ok := e.(Section); ok {
+		data = struct {
+			Section
+			Template *template.Template
+		}{s, t}
+	}
+	return execTemplate(t, e.TemplateName(), data)
+}
+
+func init() {
+	funcs["elem"] = renderElem
+}
+
+// execTemplate is a helper to execute a template and return the output as a
+// template.HTML value.
+func execTemplate(t *template.Template, name string, data interface{}) (template.HTML, error) {
+	b := new(bytes.Buffer)
+	err := t.ExecuteTemplate(b, name, data)
+	if err != nil {
+		return "", err
+	}
+	return template.HTML(b.String()), nil
+}
+
+// Text represents an optionally preformatted paragraph.
+type Text struct {
+	Lines []string
+	Pre   bool
+}
+
+func (t Text) TemplateName() string { return "text" }
+
+// List represents a bulleted list.
+type List struct {
+	Bullet []string
+}
+
+func (l List) TemplateName() string { return "list" }
+
+// Lines is a helper for parsing line-based input.
+type Lines struct {
+	line int // 0 indexed, so has 1-indexed number of last line returned
+	text []string
+}
+
+func readLines(r io.Reader) (*Lines, error) {
+	var lines []string
+	s := bufio.NewScanner(r)
+	for s.Scan() {
+		lines = append(lines, s.Text())
+	}
+	if err := s.Err(); err != nil {
+		return nil, err
+	}
+	return &Lines{0, lines}, nil
+}
+
+func (l *Lines) next() (text string, ok bool) {
+	for {
+		current := l.line
+		l.line++
+		if current >= len(l.text) {
+			return "", false
+		}
+		text = l.text[current]
+		// Lines starting with # are comments.
+		if len(text) == 0 || text[0] != '#' {
+			ok = true
+			break
+		}
+	}
+	return
+}
+
+func (l *Lines) back() {
+	l.line--
+}
+
+func (l *Lines) nextNonEmpty() (text string, ok bool) {
+	for {
+		text, ok = l.next()
+		if !ok {
+			return
+		}
+		if len(text) > 0 {
+			break
+		}
+	}
+	return
+}
+
+// A Context specifies the supporting context for parsing a presentation.
+type Context struct {
+	// ReadFile reads the file named by filename and returns the contents.
+	ReadFile func(filename string) ([]byte, error)
+}
+
+// ParseMode represents flags for the Parse function.
+type ParseMode int
+
+const (
+	// If set, parse only the title and subtitle.
+	TitlesOnly ParseMode = 1
+)
+
+// Parse parses a document from r.
+func (ctx *Context) Parse(r io.Reader, name string, mode ParseMode) (*Doc, error) {
+	doc := new(Doc)
+	lines, err := readLines(r)
+	if err != nil {
+		return nil, err
+	}
+	err = parseHeader(doc, lines)
+	if err != nil {
+		return nil, err
+	}
+	if mode&TitlesOnly != 0 {
+		return doc, nil
+	}
+	// Authors
+	if doc.Authors, err = parseAuthors(lines); err != nil {
+		return nil, err
+	}
+	// Sections
+	if doc.Sections, err = parseSections(ctx, name, lines, []int{}, doc); err != nil {
+		return nil, err
+	}
+	return doc, nil
+}
+
+// Parse parses a document from r. Parse reads assets used by the presentation
+// from the file system using ioutil.ReadFile.
+func Parse(r io.Reader, name string, mode ParseMode) (*Doc, error) {
+	ctx := Context{ReadFile: ioutil.ReadFile}
+	return ctx.Parse(r, name, mode)
+}
+
+// isHeading matches any section heading.
+var isHeading = regexp.MustCompile(`^\*+ `)
+
+// lesserHeading returns true if text is a heading of a lesser or equal level
+// than that denoted by prefix.
+func lesserHeading(text, prefix string) bool {
+	return isHeading.MatchString(text) && !strings.HasPrefix(text, prefix+"*")
+}
+
+// parseSections parses Sections from lines for the section level indicated by
+// number (a nil number indicates the top level).
+func parseSections(ctx *Context, name string, lines *Lines, number []int, doc *Doc) ([]Section, error) {
+	var sections []Section
+	for i := 1; ; i++ {
+		// Next non-empty line is title.
+		text, ok := lines.nextNonEmpty()
+		for ok && text == "" {
+			text, ok = lines.next()
+		}
+		if !ok {
+			break
+		}
+		prefix := strings.Repeat("*", len(number)+1)
+		if !strings.HasPrefix(text, prefix+" ") {
+			lines.back()
+			break
+		}
+		section := Section{
+			Number: append(append([]int{}, number...), i),
+			Title:  text[len(prefix)+1:],
+		}
+		text, ok = lines.nextNonEmpty()
+		for ok && !lesserHeading(text, prefix) {
+			var e Elem
+			r, _ := utf8.DecodeRuneInString(text)
+			switch {
+			case unicode.IsSpace(r):
+				i := strings.IndexFunc(text, func(r rune) bool {
+					return !unicode.IsSpace(r)
+				})
+				if i < 0 {
+					break
+				}
+				indent := text[:i]
+				var s []string
+				for ok && (strings.HasPrefix(text, indent) || text == "") {
+					if text != "" {
+						text = text[i:]
+					}
+					s = append(s, text)
+					text, ok = lines.next()
+				}
+				lines.back()
+				pre := strings.Join(s, "\n")
+				pre = strings.Replace(pre, "\t", "    ", -1) // browsers treat tabs badly
+				pre = strings.TrimRightFunc(pre, unicode.IsSpace)
+				e = Text{Lines: []string{pre}, Pre: true}
+			case strings.HasPrefix(text, "- "):
+				var b []string
+				for ok && strings.HasPrefix(text, "- ") {
+					b = append(b, text[2:])
+					text, ok = lines.next()
+				}
+				lines.back()
+				e = List{Bullet: b}
+			case strings.HasPrefix(text, prefix+"* "):
+				lines.back()
+				subsecs, err := parseSections(ctx, name, lines, section.Number, doc)
+				if err != nil {
+					return nil, err
+				}
+				for _, ss := range subsecs {
+					section.Elem = append(section.Elem, ss)
+				}
+			case strings.HasPrefix(text, "."):
+				args := strings.Fields(text)
+				parser := parsers[args[0]]
+				if parser == nil {
+					return nil, fmt.Errorf("%s:%d: unknown command %q\n", name, lines.line, text)
+				}
+				t, err := parser(ctx, name, lines.line, text)
+				if err != nil {
+					return nil, err
+				}
+				e = t
+			default:
+				var l []string
+				for ok && strings.TrimSpace(text) != "" {
+					if text[0] == '.' { // Command breaks text block.
+						break
+					}
+					if strings.HasPrefix(text, `\.`) { // Backslash escapes initial period.
+						text = text[1:]
+					}
+					l = append(l, text)
+					text, ok = lines.next()
+				}
+				if len(l) > 0 {
+					e = Text{Lines: l}
+				}
+			}
+			if e != nil {
+				section.Elem = append(section.Elem, e)
+			}
+			text, ok = lines.nextNonEmpty()
+		}
+		if isHeading.MatchString(text) {
+			lines.back()
+		}
+		sections = append(sections, section)
+	}
+	return sections, nil
+}
+
+func parseHeader(doc *Doc, lines *Lines) error {
+	var ok bool
+	// First non-empty line starts header.
+	doc.Title, ok = lines.nextNonEmpty()
+	if !ok {
+		return errors.New("unexpected EOF; expected title")
+	}
+	for {
+		text, ok := lines.next()
+		if !ok {
+			return errors.New("unexpected EOF")
+		}
+		if text == "" {
+			break
+		}
+		const tagPrefix = "Tags:"
+		if strings.HasPrefix(text, tagPrefix) {
+			tags := strings.Split(text[len(tagPrefix):], ",")
+			for i := range tags {
+				tags[i] = strings.TrimSpace(tags[i])
+			}
+			doc.Tags = append(doc.Tags, tags...)
+		} else if t, ok := parseTime(text); ok {
+			doc.Time = t
+		} else if doc.Subtitle == "" {
+			doc.Subtitle = text
+		} else {
+			return fmt.Errorf("unexpected header line: %q", text)
+		}
+	}
+	return nil
+}
+
+func parseAuthors(lines *Lines) (authors []Author, err error) {
+	// This grammar demarcates authors with blanks.
+
+	// Skip blank lines.
+	if _, ok := lines.nextNonEmpty(); !ok {
+		return nil, errors.New("unexpected EOF")
+	}
+	lines.back()
+
+	var a *Author
+	for {
+		text, ok := lines.next()
+		if !ok {
+			return nil, errors.New("unexpected EOF")
+		}
+
+		// If we find a section heading, we're done.
+		if strings.HasPrefix(text, "* ") {
+			lines.back()
+			break
+		}
+
+		// If we encounter a blank we're done with this author.
+		if a != nil && len(text) == 0 {
+			authors = append(authors, *a)
+			a = nil
+			continue
+		}
+		if a == nil {
+			a = new(Author)
+		}
+
+		// Parse the line. Those that
+		// - begin with @ are twitter names,
+		// - contain slashes are links, or
+		// - contain an @ symbol are an email address.
+		// The rest is just text.
+		var el Elem
+		switch {
+		case strings.HasPrefix(text, "@"):
+			el = parseURL("http://twitter.com/" + text[1:])
+		case strings.Contains(text, ":"):
+			el = parseURL(text)
+		case strings.Contains(text, "@"):
+			el = parseURL("mailto:" + text)
+		}
+		if l, ok := el.(Link); ok {
+			l.Label = text
+			el = l
+		}
+		if el == nil {
+			el = Text{Lines: []string{text}}
+		}
+		a.Elem = append(a.Elem, el)
+	}
+	if a != nil {
+		authors = append(authors, *a)
+	}
+	return authors, nil
+}
+
+func parseURL(text string) Elem {
+	u, err := url.Parse(text)
+	if err != nil {
+		log.Printf("Parse(%q): %v", text, err)
+		return nil
+	}
+	return Link{URL: u}
+}
+
+func parseTime(text string) (t time.Time, ok bool) {
+	t, err := time.Parse("15:04 2 Jan 2006", text)
+	if err == nil {
+		return t, true
+	}
+	t, err = time.Parse("2 Jan 2006", text)
+	if err == nil {
+		// at 11am UTC it is the same date everywhere
+		t = t.Add(time.Hour * 11)
+		return t, true
+	}
+	return time.Time{}, false
+}

present/style.go

@@ -0,0 +1,166 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package present
+
+import (
+	"bytes"
+	"html"
+	"html/template"
+	"strings"
+	"unicode"
+	"unicode/utf8"
+)
+
+/*
+	Fonts are demarcated by an initial and final char bracketing a
+	space-delimited word, plus possibly some terminal punctuation.
+	The chars are
+		_ for italic
+		* for bold
+		` (back quote) for fixed width.
+	Inner appearances of the char become spaces. For instance,
+		_this_is_italic_!
+	becomes
+		<i>this is italic</i>!
+*/
+
+func init() {
+	funcs["style"] = Style
+}
+
+// Style returns s with HTML entities escaped and font indicators turned into
+// HTML font tags.
+func Style(s string) template.HTML {
+	return template.HTML(font(html.EscapeString(s)))
+}
+
+// font returns s with font indicators turned into HTML font tags.
+func font(s string) string {
+	if strings.IndexAny(s, "[`_*") == -1 {
+		return s
+	}
+	words := split(s)
+	var b bytes.Buffer
+Word:
+	for w, word := range words {
+		if len(word) < 2 {
+			continue Word
+		}
+		if link, _ := parseInlineLink(word); link != "" {
+			words[w] = link
+			continue Word
+		}
+		const punctuation = `.,;:()!?—–'"`
+		const marker = "_*`"
+		// Initial punctuation is OK but must be peeled off.
+		first := strings.IndexAny(word, marker)
+		if first == -1 {
+			continue Word
+		}
+		// Is the marker prefixed only by punctuation?
+		for _, r := range word[:first] {
+			if !strings.ContainsRune(punctuation, r) {
+				continue Word
+			}
+		}
+		open, word := word[:first], word[first:]
+		char := word[0] // ASCII is OK.
+		close := ""
+		switch char {
+		default:
+			continue Word
+		case '_':
+			open += "<i>"
+			close = "</i>"
+		case '*':
+			open += "<b>"
+			close = "</b>"
+		case '`':
+			open += "<code>"
+			close = "</code>"
+		}
+		// Terminal punctuation is OK but must be peeled off.
+		last := strings.LastIndex(word, word[:1])
+		if last == 0 {
+			continue Word
+		}
+		head, tail := word[:last+1], word[last+1:]
+		for _, r := range tail {
+			if !strings.ContainsRune(punctuation, r) {
+				continue Word
+			}
+		}
+		b.Reset()
+		b.WriteString(open)
+		var wid int
+		for i := 1; i < len(head)-1; i += wid {
+			var r rune
+			r, wid = utf8.DecodeRuneInString(head[i:])
+			if r != rune(char) {
+				// Ordinary character.
+				b.WriteRune(r)
+				continue
+			}
+			if head[i+1] != char {
+				// Inner char becomes space.
+				b.WriteRune(' ')
+				continue
+			}
+			// Doubled char becomes real char.
+			// Not worth worrying about "_x__".
+			b.WriteByte(char)
+			wid++ // Consumed two chars, both ASCII.
+		}
+		b.WriteString(close) // Write closing tag.
+		b.WriteString(tail)  // Restore trailing punctuation.
+		words[w] = b.String()
+	}
+	return strings.Join(words, "")
+}
+
+// split is like strings.Fields but also returns the runs of spaces
+// and treats inline links as distinct words.
+func split(s string) []string {
+	var (
+		words = make([]string, 0, 10)
+		start = 0
+	)
+
+	// appendWord appends the string s[start:end] to the words slice.
+	// If the word contains the beginning of a link, the non-link portion
+	// of the word and the entire link are appended as separate words,
+	// and the start index is advanced to the end of the link.
+	appendWord := func(end int) {
+		if j := strings.Index(s[start:end], "[["); j > -1 {
+			if _, l := parseInlineLink(s[start+j:]); l > 0 {
+				// Append portion before link, if any.
+				if j > 0 {
+					words = append(words, s[start:start+j])
+				}
+				// Append link itself.
+				words = append(words, s[start+j:start+j+l])
+				// Advance start index to end of link.
+				start = start + j + l
+				return
+			}
+		}
+		// No link; just add the word.
+		words = append(words, s[start:end])
+		start = end
+	}
+
+	wasSpace := false
+	for i, r := range s {
+		isSpace := unicode.IsSpace(r)
+		if i > start && isSpace != wasSpace {
+			appendWord(i)
+		}
+		wasSpace = isSpace
+	}
+	for start < len(s) {
+		appendWord(len(s))
+	}
+	return words
+}

present/style_test.go

@@ -0,0 +1,116 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package present
+
+import (
+	"fmt"
+	"reflect"
+	"testing"
+)
+
+func TestSplit(t *testing.T) {
+	var tests = []struct {
+		in  string
+		out []string
+	}{
+		{"", []string{}},
+		{" ", []string{" "}},
+		{"abc", []string{"abc"}},
+		{"abc def", []string{"abc", " ", "def"}},
+		{"abc def ", []string{"abc", " ", "def", " "}},
+		{"hey [[http://golang.org][Gophers]] around",
+			[]string{"hey", " ", "[[http://golang.org][Gophers]]", " ", "around"}},
+		{"A [[http://golang.org/doc][two words]] link",
+			[]string{"A", " ", "[[http://golang.org/doc][two words]]", " ", "link"}},
+		{"Visit [[http://golang.org/doc]] now",
+			[]string{"Visit", " ", "[[http://golang.org/doc]]", " ", "now"}},
+		{"not [[http://golang.org/doc][a [[link]] ]] around",
+			[]string{"not", " ", "[[http://golang.org/doc][a [[link]]", " ", "]]", " ", "around"}},
+		{"[[http://golang.org][foo bar]]",
+			[]string{"[[http://golang.org][foo bar]]"}},
+		{"ends with [[http://golang.org][link]]",
+			[]string{"ends", " ", "with", " ", "[[http://golang.org][link]]"}},
+		{"my talk ([[http://talks.golang.org/][slides here]])",
+			[]string{"my", " ", "talk", " ", "(", "[[http://talks.golang.org/][slides here]]", ")"}},
+	}
+	for _, test := range tests {
+		out := split(test.in)
+		if !reflect.DeepEqual(out, test.out) {
+			t.Errorf("split(%q):\ngot\t%q\nwant\t%q", test.in, out, test.out)
+		}
+	}
+}
+
+func TestFont(t *testing.T) {
+	var tests = []struct {
+		in  string
+		out string
+	}{
+		{"", ""},
+		{" ", " "},
+		{"\tx", "\tx"},
+		{"_a_", "<i>a</i>"},
+		{"*a*", "<b>a</b>"},
+		{"`a`", "<code>a</code>"},
+		{"_a_b_", "<i>a b</i>"},
+		{"_a__b_", "<i>a_b</i>"},
+		{"_a___b_", "<i>a_ b</i>"},
+		{"*a**b*?", "<b>a*b</b>?"},
+		{"_a_<>_b_.", "<i>a <> b</i>."},
+		{"(_a_)", "(<i>a</i>)"},
+		{"((_a_), _b_, _c_).", "((<i>a</i>), <i>b</i>, <i>c</i>)."},
+		{"(_a)", "(_a)"},
+		{"(_a)", "(_a)"},
+		{"_Why_use_scoped__ptr_? Use plain ***ptr* instead.", "<i>Why use scoped_ptr</i>? Use plain <b>*ptr</b> instead."},
+		{"_hey_ [[http://golang.org][*Gophers*]] *around*",
+			`<i>hey</i> <a href="http://golang.org" target="_blank"><b>Gophers</b></a> <b>around</b>`},
+		{"_hey_ [[http://golang.org][so _many_ *Gophers*]] *around*",
+			`<i>hey</i> <a href="http://golang.org" target="_blank">so <i>many</i> <b>Gophers</b></a> <b>around</b>`},
+		{"Visit [[http://golang.org]] now",
+			`Visit <a href="http://golang.org" target="_blank">golang.org</a> now`},
+		{"my talk ([[http://talks.golang.org/][slides here]])",
+			`my talk (<a href="http://talks.golang.org/" target="_blank">slides here</a>)`},
+	}
+	for _, test := range tests {
+		out := font(test.in)
+		if out != test.out {
+			t.Errorf("font(%q):\ngot\t%q\nwant\t%q", test.in, out, test.out)
+		}
+	}
+}
+
+func TestStyle(t *testing.T) {
+	var tests = []struct {
+		in  string
+		out string
+	}{
+		{"", ""},
+		{" ", " "},
+		{"\tx", "\tx"},
+		{"_a_", "<i>a</i>"},
+		{"*a*", "<b>a</b>"},
+		{"`a`", "<code>a</code>"},
+		{"_a_b_", "<i>a b</i>"},
+		{"_a__b_", "<i>a_b</i>"},
+		{"_a___b_", "<i>a_ b</i>"},
+		{"*a**b*?", "<b>a*b</b>?"},
+		{"_a_<>_b_.", "<i>a &lt;&gt; b</i>."},
+		{"(_a_<>_b_)", "(<i>a &lt;&gt; b</i>)"},
+		{"((_a_), _b_, _c_).", "((<i>a</i>), <i>b</i>, <i>c</i>)."},
+		{"(_a)", "(_a)"},
+	}
+	for _, test := range tests {
+		out := string(Style(test.in))
+		if out != test.out {
+			t.Errorf("style(%q):\ngot\t%q\nwant\t%q", test.in, out, test.out)
+		}
+	}
+}
+
+func ExampleStyle() {
+	const s = "*Gophers* are _clearly_ > *cats*!"
+	fmt.Println(Style(s))
+	// Output: <b>Gophers</b> are <i>clearly</i> &gt; <b>cats</b>!
+}