internal/web: merge with go.dev/cmd/internal/site

internal/web was the framework left serving golang.org.
go.dev/cmd/internal/site was the framework serving go.dev.
This CL merges the two into a coherent, simple site serving
framework that works for both sites, a step toward merging
the sites themselves.

The CL is difficult to break up, so it's a bit larger than would be ideal.
The best place to start is the doc comment in internal/web/site.go
and then the other changes in that directory.
The rest of the CL is just minor adjustments to the repo to match.

Change-Id: I927dea29396104a817bd81b6bf25fa43f996968f
Reviewed-on: https://go-review.googlesource.com/c/website/+/339403
Trust: Russ Cox <rsc@golang.org>
Website-Publish: Russ Cox <rsc@golang.org>
Reviewed-by: Jamal Carvalho <jamal@golang.org>

1 files changed, 147 insertions, 0 deletions

diff --git a/internal/web/code.go b/internal/web/code.go
new file mode 100644
index 00000000..3da494e2
--- /dev/null
+++ b/internal/web/code.go
@@ -0,0 +1,147 @@
+// 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 web
+
+import (
+	"bytes"
+	"fmt"
+	"log"
+	"regexp"
+	"strings"
+
+	"golang.org/x/website/internal/backport/html/template"
+	"golang.org/x/website/internal/texthtml"
+)
+
+func (s *siteDir) code(file string, arg ...interface{}) (_ template.HTML, err error) {
+	defer func() {
+		if r := recover(); r != nil {
+			err = fmt.Errorf("%v", r)
+		}
+	}()
+
+	btext, err := s.readFile(s.dir, file)
+	if err != nil {
+		return "", err
+	}
+	text := string(btext)
+	var command string
+	switch len(arg) {
+	case 0:
+		// text is already whole file.
+		command = fmt.Sprintf("code %q", file)
+	case 1:
+		command = fmt.Sprintf("code %q %s", file, stringFor(arg[0]))
+		text = s.oneLine(file, text, arg[0])
+	case 2:
+		command = fmt.Sprintf("code %q %s %s", file, stringFor(arg[0]), stringFor(arg[1]))
+		text = s.multipleLines(file, text, arg[0], arg[1])
+	default:
+		return "", fmt.Errorf("incorrect code invocation: code %q [%v, ...] (%d arguments)", file, arg[0], len(arg))
+	}
+	// Trim spaces from output.
+	text = strings.Trim(text, "\n")
+	// Replace tabs by spaces, which work better in HTML.
+	text = strings.Replace(text, "\t", "    ", -1)
+	var buf bytes.Buffer
+	// HTML-escape text and syntax-color comments like elsewhere.
+	buf.Write(texthtml.Format([]byte(text), texthtml.Config{GoComments: true}))
+	// Include the command as a comment.
+	text = fmt.Sprintf("<pre><!--{{%s}}\n-->%s</pre>", command, buf.Bytes())
+	return template.HTML(text), nil
+}
+
+// Functions in this file panic on error, but the panic is recovered
+// to an error by 'code'.
+
+// stringFor returns a textual representation of the arg, formatted according to its nature.
+func stringFor(arg interface{}) string {
+	switch arg := arg.(type) {
+	case int:
+		return fmt.Sprintf("%d", arg)
+	case string:
+		if len(arg) > 2 && arg[0] == '/' && arg[len(arg)-1] == '/' {
+			return fmt.Sprintf("%#q", arg)
+		}
+		return fmt.Sprintf("%q", arg)
+	default:
+		log.Panicf("unrecognized argument: %v type %T", arg, arg)
+	}
+	return ""
+}
+
+// oneLine returns the single line generated by a two-argument code invocation.
+func (s *Site) oneLine(file, text string, arg interface{}) string {
+	lines := strings.SplitAfter(text, "\n")
+	line, pattern, isInt := parseArg(arg, file, len(lines))
+	if isInt {
+		return lines[line-1]
+	}
+	return lines[match(file, 0, lines, pattern)-1]
+}
+
+// multipleLines returns the text generated by a three-argument code invocation.
+func (s *Site) multipleLines(file, text string, arg1, arg2 interface{}) string {
+	lines := strings.SplitAfter(text, "\n")
+	line1, pattern1, isInt1 := parseArg(arg1, file, len(lines))
+	line2, pattern2, isInt2 := parseArg(arg2, file, len(lines))
+	if !isInt1 {
+		line1 = match(file, 0, lines, pattern1)
+	}
+	if !isInt2 {
+		line2 = match(file, line1, lines, pattern2)
+	} else if line2 < line1 {
+		log.Panicf("lines out of order for %q: %d %d", file, line1, line2)
+	}
+	for k := line1 - 1; k < line2; k++ {
+		if strings.HasSuffix(lines[k], "OMIT\n") {
+			lines[k] = ""
+		}
+	}
+	return strings.Join(lines[line1-1:line2], "")
+}
+
+// parseArg returns the integer or string value of the argument and tells which it is.
+func parseArg(arg interface{}, file string, max int) (ival int, sval string, isInt bool) {
+	switch n := arg.(type) {
+	case int:
+		if n <= 0 || n > max {
+			log.Panicf("%q:%d is out of range", file, n)
+		}
+		return n, "", true
+	case string:
+		return 0, n, false
+	}
+	log.Panicf("unrecognized argument %v type %T", arg, arg)
+	return
+}
+
+// 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 {
+	// $ matches the end of the file.
+	if pattern == "$" {
+		if len(lines) == 0 {
+			log.Panicf("%q: empty file", file)
+		}
+		return len(lines)
+	}
+	// /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 {
+			log.Panic(err)
+		}
+		for i := start; i < len(lines); i++ {
+			if re.MatchString(lines[i]) {
+				return i + 1
+			}
+		}
+		log.Panicf("%s: no match for %#q", file, pattern)
+	}
+	log.Panicf("unrecognized pattern: %q", pattern)
+	return 0
+}