/
render.go
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/
render.go
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// This file is part of gmnhg.
// gmnhg 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.
// gmnhg 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 gmnhg. If not, see <https://www.gnu.org/licenses/>.
// Package gemini provides functions to convert Markdown files to
// Gemtext. It supports the use of YAML front matter in Markdown.
package gemini
import (
"bytes"
"errors"
"fmt"
"time"
"git.tdem.in/tdemin/gmnhg/internal/gemini"
"github.com/gomarkdown/markdown"
"github.com/gomarkdown/markdown/parser"
"gopkg.in/yaml.v2"
)
// HugoMetadata implements gemini.Metadata, providing the bare minimum
// of possible post props.
type HugoMetadata struct {
PostTitle string `yaml:"title"`
PostIsDraft bool `yaml:"draft"`
PostLayout string `yaml:"layout"`
PostDate time.Time `yaml:"date"`
}
// Title returns post title.
func (h HugoMetadata) Title() string {
return h.PostTitle
}
// Date returns post date.
func (h HugoMetadata) Date() time.Time {
return h.PostDate
}
var yamlDelimiter = []byte("---\n")
// ErrPostIsDraft indicates the post rendered is a draft and is not
// supposed to be rendered.
var ErrPostIsDraft = errors.New("post is draft")
// RenderMarkdown converts Markdown text to text/gemini using
// gomarkdown, appending Hugo YAML front matter data if any is present
// to the post header.
//
// Only a subset of front matter data parsed by Hugo is included in the
// final document. At this point it's just title and date.
//
// Draft posts are still rendered, but with an error of type
// ErrPostIsDraft.
func RenderMarkdown(md []byte, withMetadata bool) (geminiText []byte, metadata HugoMetadata, err error) {
var (
blockEnd int
yamlContent []byte
)
// only allow front matter at file start
if bytes.Index(md, yamlDelimiter) != 0 {
goto parse
}
blockEnd = bytes.Index(md[len(yamlDelimiter):], yamlDelimiter)
if blockEnd == -1 {
goto parse
}
yamlContent = md[len(yamlDelimiter) : blockEnd+len(yamlDelimiter)]
if err := yaml.Unmarshal(yamlContent, &metadata); err != nil {
return nil, metadata, fmt.Errorf("invalid front matter: %w", err)
}
md = md[blockEnd+len(yamlDelimiter)*2:]
parse:
ast := markdown.Parse(md, parser.NewWithExtensions(parser.CommonExtensions))
var geminiContent []byte
if withMetadata && metadata.PostTitle != "" {
geminiContent = markdown.Render(ast, gemini.NewRendererWithMetadata(metadata))
} else {
geminiContent = markdown.Render(ast, gemini.NewRenderer())
}
if metadata.PostIsDraft {
return geminiContent, metadata, fmt.Errorf("%s: %w", metadata.PostTitle, ErrPostIsDraft)
}
return geminiContent, metadata, nil
}