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source.go
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source.go
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/*******************************************************************************
*
* Copyright 2018 Stefan Majewsky <majewsky@gmx.net>
*
* This program is free software: you can redistribute it and/or modify it under
* the terms of the GNU General Public License as published by the Free Software
* Foundation, either version 3 of the License, or (at your option) any later
* version.
*
* This program is distributed in the hope that it will be useful, but WITHOUT ANY
* WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
* A PARTICULAR PURPOSE. See the GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along with
* this program. If not, see <http://www.gnu.org/licenses/>.
*
*******************************************************************************/
package main
import (
"bytes"
"crypto/md5"
"encoding/hex"
"encoding/json"
"errors"
"fmt"
"html"
"html/template"
"io/ioutil"
"os"
"os/exec"
"path/filepath"
"regexp"
"strings"
"gitlab.com/golang-commonmark/markdown"
)
//SourceFile represents a Markdown source file.
type SourceFile struct {
FilesystemPath string
URLPath string
}
//FindSourceFiles discovers all source files in the input directory.
func FindSourceFiles(inputDir string) ([]SourceFile, error) {
var result []SourceFile
baseDir := filepath.Join(inputDir, "spec")
err := walk(baseDir, func(path string, fi os.FileInfo) {
if fi.Mode().IsRegular() && strings.HasSuffix(path, ".md") {
relativePath, _ := filepath.Rel(baseDir, path)
result = append(result, newSourceFile(path, filepath.Join("std", relativePath)))
}
})
if err != nil {
return nil, err
}
baseDir = filepath.Join(inputDir, "website/pages")
err = walk(baseDir, func(path string, fi os.FileInfo) {
if fi.Mode().IsRegular() && strings.HasSuffix(path, ".md") {
relativePath, _ := filepath.Rel(baseDir, path)
result = append(result, newSourceFile(path, relativePath))
}
})
if err != nil {
return nil, err
}
return result, nil
}
//Like filepath.Walk(), but don't pass errors to the callback.
func walk(root string, callback func(string, os.FileInfo)) error {
return filepath.Walk(root, func(path string, fi os.FileInfo, err error) error {
if err != nil {
return err
}
callback(path, fi)
return nil
})
}
//Called by FindSourceFiles().
func newSourceFile(path, relativePath string) SourceFile {
//e.g. path = "/path/to/vt6/spec/core/1.0.md"
//and relativePath = "std/core/1.0.md" ("std" was added above already)
//strip the ".md" suffix from the URL
urlPath := strings.TrimSuffix(relativePath, ".md")
//if the path ends in "index", that's just a trick for when we cannot spell
//out the path otherwise, e.g. the page for URLPath = "/" is at
//"website/pages/index.md" instead of "website/pages/.md" because that would
//be a hidden file
if urlPath == "index" {
urlPath = "/"
} else {
urlPath = filepath.Join("/", strings.TrimSuffix(urlPath, "/index"))
}
return SourceFile{
FilesystemPath: path,
URLPath: urlPath,
}
}
//Render converts the Markdown from the source file to HTML and initializes a
//Page instance for this source file.
func (s SourceFile) Render() (Page, error) {
contentBytes, err := ioutil.ReadFile(s.FilesystemPath)
if err != nil {
return Page{}, err
}
md := markdown.New(markdown.HTML(true))
tokens := md.Parse(contentBytes)
toc := CollectTableOfContents(tokens)
contentHTML := md.RenderTokensToString(tokens)
//recognize paragraphs starting with *Rationale:*
contentHTML = strings.Replace(contentHTML,
"\n<p><em>Rationale:</em>",
"\n<p class=\"rationale\"><em>Rationale:</em>",
-1,
)
//add link targets to headings
contentHTML = InjectTargetsIntoHeadings(contentHTML, toc)
//compile TikZ code into SVGs
tikzOpening := `<pre><code class="language-tikz">`
tikzClosing := `</code></pre>`
tikzRx := regexp.MustCompile(tikzOpening + `(?s)(.*?)` + tikzClosing)
err = nil
var assets []Asset
contentHTML = tikzRx.ReplaceAllStringFunc(contentHTML, func(match string) string {
match = strings.TrimPrefix(match, tikzOpening)
match = strings.TrimSuffix(match, tikzClosing)
match = html.UnescapeString(match)
asset, err2 := compileTikzPicture(match)
if err == nil {
err = err2
}
if asset.Path != "" {
assets = append(assets, asset)
}
//TODO "alt" attribute
return "<img class=\"svg\" src=\"/" + asset.Path + "\" />"
})
if err != nil {
return Page{}, err
}
//recognize draft marker ...
fields := strings.SplitN(contentHTML, "\n", 2)
firstLine := fields[0]
isDraft := strings.TrimSpace(firstLine) == "<!-- draft -->"
//... and remove it
if isDraft {
contentHTML = fields[1]
}
//recognize explicit title/description declaration...
fields = strings.SplitN(contentHTML, "\n", 2)
firstLine = fields[0]
match := regexp.MustCompile(`^<!--\s*(\{.*\})\s*-->$`).FindStringSubmatch(firstLine)
title, description := "", ""
if match != nil {
//...parse it...
var data struct {
Title string `json:"title"`
Description string `json:"description"`
}
err := json.Unmarshal([]byte(match[1]), &data)
if err != nil {
return Page{}, fmt.Errorf(
"read %s: unmarshal front matter failed: %s",
s.FilesystemPath, err.Error(),
)
}
title = data.Title
description = data.Description
//... and remove it
contentHTML = fields[1]
}
//find page title, usually from leading heading
if title == "" {
if len(toc) > 0 && toc[0].IsPageTitle {
title = toc[0].Caption
// do we have a pair of title and description, e.g.
// title = "vt6/posix1.0 - Platform integration on POSIX-compliant systems"
fields := strings.SplitN(title, " - ", 2)
if len(fields) == 2 {
title = fields[0]
description = fields[1]
}
} else {
//last-resort fallback
fmt.Fprintf(os.Stderr, "WARNING: cannot determine page title for %s\n", s.URLPath)
title = strings.TrimPrefix(s.URLPath, "/")
}
}
return Page{
Path: s.URLPath,
Title: title,
Description: description,
IsDraft: isDraft,
ContentHTML: template.HTML(contentHTML),
TableOfContentsHTML: template.HTML(RenderTableOfContents(toc)),
Assets: assets,
}, nil
}
//Takes in some LaTeX/TikZ source code and returns the rendered SVG.
func compileTikzPicture(code string) (asset Asset, returnErr error) {
pictureHash := md5.Sum([]byte(code))
pictureID := hex.EncodeToString(pictureHash[:])
//split preamble from drawing code
fields := regexp.MustCompile(`(?m)^---\s*$`).Split(code, 2)
if len(fields) < 2 {
return Asset{}, errors.New("cannot find preamble separator")
}
preamble := strings.TrimSpace(fields[0])
drawingCode := strings.TrimSpace(fields[1])
//create temp directory for compilation
tempDir := filepath.Join(
os.TempDir(),
"vt6-website-build-"+pictureID,
)
err := os.MkdirAll(tempDir, 0700)
if err != nil {
return Asset{}, err
}
defer func() {
if returnErr == nil {
returnErr = os.RemoveAll(tempDir)
}
}()
//prepare full LaTeX source file
fullCode := "\\documentclass[tikz]{standalone}\n" +
preamble + "\\begin{document}\\begin{tikzpicture}\n" +
drawingCode + "\\end{tikzpicture}\\end{document}\n"
err = ioutil.WriteFile(filepath.Join(tempDir, "picture.tex"), []byte(fullCode), 0600)
if err != nil {
return Asset{}, err
}
//run pdflatex
cmd := exec.Command("pdflatex", "-interaction", "nonstopmode", "picture")
cmd.Dir = tempDir
cmd.Stdin = nil
cmd.Stdout = nil
cmd.Stderr = nil
err = cmd.Run()
if err != nil {
return Asset{}, fmt.Errorf("exec pdflatex failed: %s", err.Error())
}
//run pdf2svg
cmd = exec.Command("pdf2svg", "picture.pdf", "/dev/fd/1", "1")
cmd.Dir = tempDir
cmd.Stdin = nil
var buf bytes.Buffer
cmd.Stdout = &buf
cmd.Stderr = os.Stderr
err = cmd.Run()
if err != nil {
return Asset{}, fmt.Errorf("exec pdflatex failed: %s", err.Error())
}
return Asset{Path: "svg/" + pictureID + ".svg", Content: buf.Bytes()}, nil
}