112 lines
3.4 KiB
Go
112 lines
3.4 KiB
Go
// This file is part of gmnhg.
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// gmnhg is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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// gmnhg is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// You should have received a copy of the GNU General Public License
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// along with gmnhg. If not, see <https://www.gnu.org/licenses/>.
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// Package gemini provides functions to convert Markdown files to
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// Gemtext. It supports the use of YAML front matter in Markdown.
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package gemini
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import (
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"bytes"
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"errors"
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"fmt"
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"time"
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"git.tdem.in/tdemin/gmnhg/internal/gemini"
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"github.com/gomarkdown/markdown"
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"github.com/gomarkdown/markdown/parser"
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"gopkg.in/yaml.v2"
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)
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// HugoMetadata implements gemini.Metadata, providing the bare minimum
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// of possible post props.
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type HugoMetadata struct {
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PostTitle string `yaml:"title"`
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PostIsDraft bool `yaml:"draft"`
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PostLayout string `yaml:"layout"`
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PostDate time.Time `yaml:"date"`
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}
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// Title returns post title.
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func (h HugoMetadata) Title() string {
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return h.PostTitle
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}
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// Date returns post date.
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func (h HugoMetadata) Date() time.Time {
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return h.PostDate
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}
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var yamlDelimiter = []byte("---\n")
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// ErrPostIsDraft indicates the post rendered is a draft and is not
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// supposed to be rendered.
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var ErrPostIsDraft = errors.New("post is draft")
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// Settings is a bitmask for renderer preferences.
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type Settings uint
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// Has uses AND to check whether a flag is set.
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func (s Settings) Has(setting Settings) bool {
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return (s & setting) != 0
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}
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const (
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// Defaults simply renders the document.
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Defaults Settings = 0b0
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// WithMetadata indicates that the metadata should be included in
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// the text produced by the renderer.
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WithMetadata Settings = 0b1
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)
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// RenderMarkdown converts Markdown text to Gemtext using gomarkdown. It
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// appends Hugo YAML front matter data to the post header if
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// WithMetadata is set.
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//
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// Only a subset of front matter data parsed by Hugo is included in the
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// final document. At this point it's just title and date.
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//
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// Draft posts are still rendered, but with an error of type
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// ErrPostIsDraft.
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func RenderMarkdown(md []byte, settings Settings) (geminiText []byte, metadata HugoMetadata, err error) {
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var (
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blockEnd int
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yamlContent []byte
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)
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// only allow front matter at file start
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if bytes.Index(md, yamlDelimiter) != 0 {
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goto parse
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}
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blockEnd = bytes.Index(md[len(yamlDelimiter):], yamlDelimiter)
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if blockEnd == -1 {
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goto parse
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}
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yamlContent = md[len(yamlDelimiter) : blockEnd+len(yamlDelimiter)]
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if err := yaml.Unmarshal(yamlContent, &metadata); err != nil {
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return nil, metadata, fmt.Errorf("invalid front matter: %w", err)
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}
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md = md[blockEnd+len(yamlDelimiter)*2:]
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parse:
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ast := markdown.Parse(md, parser.NewWithExtensions(parser.CommonExtensions))
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var geminiContent []byte
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if settings.Has(WithMetadata) && metadata.PostTitle != "" {
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geminiContent = markdown.Render(ast, gemini.NewRendererWithMetadata(metadata))
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} else {
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geminiContent = markdown.Render(ast, gemini.NewRenderer())
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}
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if metadata.PostIsDraft {
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return geminiContent, metadata, fmt.Errorf("%s: %w", metadata.PostTitle, ErrPostIsDraft)
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}
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return geminiContent, metadata, nil
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}
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