hugo/hugolib/permalinks.go

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package hugolib
import (
"errors"
"fmt"
"strconv"
"strings"
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"github.com/spf13/hugo/helpers"
)
// PathPattern represents a string which builds up a URL from attributes
type PathPattern string
// PageToPermaAttribute is the type of a function which, given a page and a tag
// can return a string to go in that position in the page (or an error)
type PageToPermaAttribute func(*Page, string) (string, error)
// PermalinkOverrides maps a section name to a PathPattern
type PermalinkOverrides map[string]PathPattern
// knownPermalinkAttributes maps :tags in a permalink specification to a
// function which, given a page and the tag, returns the resulting string
// to be used to replace that tag.
var knownPermalinkAttributes map[string]PageToPermaAttribute
// validate determines if a PathPattern is well-formed
func (pp PathPattern) validate() bool {
fragments := strings.Split(string(pp[1:]), "/")
var bail = false
for i := range fragments {
if bail {
return false
}
if len(fragments[i]) == 0 {
bail = true
continue
}
if !strings.HasPrefix(fragments[i], ":") {
continue
}
k := strings.ToLower(fragments[i][1:])
if _, ok := knownPermalinkAttributes[k]; !ok {
return false
}
}
return true
}
type permalinkExpandError struct {
pattern PathPattern
section string
err error
}
func (pee *permalinkExpandError) Error() string {
return fmt.Sprintf("error expanding %q section %q: %s", string(pee.pattern), pee.section, pee.err)
}
var (
errPermalinkIllFormed = errors.New("permalink ill-formed")
errPermalinkAttributeUnknown = errors.New("permalink attribute not recognised")
)
// Expand on a PathPattern takes a Page and returns the fully expanded Permalink
// or an error explaining the failure.
func (pp PathPattern) Expand(p *Page) (string, error) {
if !pp.validate() {
return "", &permalinkExpandError{pattern: pp, section: "<all>", err: errPermalinkIllFormed}
}
sections := strings.Split(string(pp), "/")
for i, field := range sections {
if len(field) == 0 || field[0] != ':' {
continue
}
attr := field[1:]
callback, ok := knownPermalinkAttributes[attr]
if !ok {
return "", &permalinkExpandError{pattern: pp, section: strconv.Itoa(i), err: errPermalinkAttributeUnknown}
}
newField, err := callback(p, attr)
if err != nil {
return "", &permalinkExpandError{pattern: pp, section: strconv.Itoa(i), err: err}
}
sections[i] = newField
}
return strings.Join(sections, "/"), nil
}
func pageToPermalinkDate(p *Page, dateField string) (string, error) {
// a Page contains a Node which provides a field Date, time.Time
switch dateField {
case "year":
return strconv.Itoa(p.Date.Year()), nil
case "month":
return fmt.Sprintf("%02d", int(p.Date.Month())), nil
case "monthname":
return p.Date.Month().String(), nil
case "day":
return fmt.Sprintf("%02d", int(p.Date.Day())), nil
case "weekday":
return strconv.Itoa(int(p.Date.Weekday())), nil
case "weekdayname":
return p.Date.Weekday().String(), nil
case "yearday":
return strconv.Itoa(p.Date.YearDay()), nil
}
//TODO: support classic strftime escapes too
// (and pass those through despite not being in the map)
panic("coding error: should not be here")
}
// pageToPermalinkTitle returns the URL-safe form of the title
func pageToPermalinkTitle(p *Page, _ string) (string, error) {
// Page contains Node which has Title
// (also contains UrlPath which has Slug, sometimes)
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return helpers.Urlize(p.Title), nil
}
// if the page has a slug, return the slug, else return the title
func pageToPermalinkSlugElseTitle(p *Page, a string) (string, error) {
if p.Slug != "" {
return p.Slug, nil
}
return pageToPermalinkTitle(p, a)
}
func pageToPermalinkSection(p *Page, _ string) (string, error) {
// Page contains Node contains UrlPath which has Section
return p.Section, nil
}
func init() {
knownPermalinkAttributes = map[string]PageToPermaAttribute{
"year": pageToPermalinkDate,
"month": pageToPermalinkDate,
"monthname": pageToPermalinkDate,
"day": pageToPermalinkDate,
"weekday": pageToPermalinkDate,
"weekdayname": pageToPermalinkDate,
"yearday": pageToPermalinkDate,
"section": pageToPermalinkSection,
"title": pageToPermalinkTitle,
"slug": pageToPermalinkSlugElseTitle,
}
}