gojekyll/permalinks.go

package main

import (
	"fmt"
	"path/filepath"
	"strings"
)

// PermalinkStyles defines built-in styles from https://jekyllrb.com/docs/permalinks/#builtinpermalinkstyles
var PermalinkStyles = map[string]string{
	"date":    "/:categories/:year/:month/:day/:title.html",
	"pretty":  "/:categories/:year/:month/:day/:title/",
	"ordinal": "/:categories/:year/:y_day/:title.html",
	"none":    "/:categories/:title.html",
}

func permalinkTemplateVariables(path string, frontMatter VariableMap) map[string]string {
	var (
		collectionName string
		localPath      = path
		ext            = filepath.Ext(path)
		root           = path[:len(path)-len(ext)]
		outputExt      = ext
		name           = filepath.Base(root)
		title          = frontMatter.String("title", name)
	)

	if isMarkdown(path) {
		outputExt = ".html"
	}

	if val, found := frontMatter["collection"]; found {
		collectionName = val.(string)
		prefix := "_" + collectionName + "/"
		localPath = localPath[len(prefix):]
	}

	return map[string]string{
		"collection": collectionName,
		"ext":        strings.TrimLeft(ext, "."),
		"name":       hyphenateNonAlphaSequence(name),
		"output_ext": strings.TrimLeft(outputExt, "."),
		"path":       localPath,
		"title":      hyphenateNonAlphaSequence(title),
		// TODO year month imonth day i_day short_year hour minute second slug categories
	}
}

func expandPermalinkPattern(pattern string, path string, frontMatter VariableMap) (s string, err error) {
	if p, found := PermalinkStyles[pattern]; found {
		pattern = p
	}
	templateVariables := permalinkTemplateVariables(path, frontMatter)
	// The ReplaceAllStringFunc callback signals errors via panic.
	// Turn them into return values.
	defer func() {
		if r := recover(); r != nil {
			if e, ok := r.(error); ok {
				err = e
			} else {
				panic(r)
			}
		}
	}()
	s = templateVariableMatcher.ReplaceAllStringFunc(pattern, func(m string) string {
		varname := m[1:]
		value, found := templateVariables[varname]
		if !found {
			panic(fmt.Errorf("unknown variable %s in permalink template %s", varname, pattern))
		}
		return value
	})
	return
}