hugo/parser/frontmatter.go

// Copyright 2015 The Hugo Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package parser

// TODO(bep) archetype remove unused from this package.

import (
	"bytes"
	"encoding/json"
	"errors"
	"io"
	"strings"

	"github.com/gohugoio/hugo/parser/metadecoders"

	"github.com/BurntSushi/toml"

	"gopkg.in/yaml.v2"
)

// FrontmatterType represents a type of frontmatter.
type FrontmatterType struct {
	// Parse decodes content into a Go interface.
	Parse func([]byte) (map[string]interface{}, error)

	markstart, markend []byte // starting and ending delimiters
	includeMark        bool   // include start and end mark in output
}

// InterfaceToConfig encodes a given input based upon the mark and writes to w.
func InterfaceToConfig(in interface{}, mark rune, w io.Writer) error {
	if in == nil {
		return errors.New("input was nil")
	}

	switch mark {
	case rune(YAMLLead[0]):
		b, err := yaml.Marshal(in)
		if err != nil {
			return err
		}

		_, err = w.Write(b)
		return err

	case rune(TOMLLead[0]):
		return toml.NewEncoder(w).Encode(in)
	case rune(JSONLead[0]):
		b, err := json.MarshalIndent(in, "", "   ")
		if err != nil {
			return err
		}

		_, err = w.Write(b)
		if err != nil {
			return err
		}

		_, err = w.Write([]byte{'\n'})
		return err

	default:
		return errors.New("Unsupported Format provided")
	}
}

func InterfaceToConfig2(in interface{}, format metadecoders.Format, w io.Writer) error {
	if in == nil {
		return errors.New("input was nil")
	}

	switch format {
	case metadecoders.YAML:
		b, err := yaml.Marshal(in)
		if err != nil {
			return err
		}

		_, err = w.Write(b)
		return err

	case metadecoders.TOML:
		return toml.NewEncoder(w).Encode(in)
	case metadecoders.JSON:
		b, err := json.MarshalIndent(in, "", "   ")
		if err != nil {
			return err
		}

		_, err = w.Write(b)
		if err != nil {
			return err
		}

		_, err = w.Write([]byte{'\n'})
		return err

	default:
		return errors.New("Unsupported Format provided")
	}
}

func InterfaceToFrontMatter2(in interface{}, format metadecoders.Format, w io.Writer) error {
	if in == nil {
		return errors.New("input was nil")
	}

	switch format {
	case metadecoders.YAML:
		_, err := w.Write([]byte(YAMLDelimUnix))
		if err != nil {
			return err
		}

		err = InterfaceToConfig2(in, format, w)
		if err != nil {
			return err
		}

		_, err = w.Write([]byte(YAMLDelimUnix))
		return err

	case metadecoders.TOML:
		_, err := w.Write([]byte(TOMLDelimUnix))
		if err != nil {
			return err
		}

		err = InterfaceToConfig2(in, format, w)

		if err != nil {
			return err
		}

		_, err = w.Write([]byte("\n" + TOMLDelimUnix))
		return err

	default:
		return InterfaceToConfig2(in, format, w)
	}
}

// InterfaceToFrontMatter encodes a given input into a frontmatter
// representation based upon the mark with the appropriate front matter delimiters
// surrounding the output, which is written to w.
func InterfaceToFrontMatter(in interface{}, mark rune, w io.Writer) error {
	if in == nil {
		return errors.New("input was nil")
	}

	switch mark {
	case rune(YAMLLead[0]):
		_, err := w.Write([]byte(YAMLDelimUnix))
		if err != nil {
			return err
		}

		err = InterfaceToConfig(in, mark, w)
		if err != nil {
			return err
		}

		_, err = w.Write([]byte(YAMLDelimUnix))
		return err

	case rune(TOMLLead[0]):
		_, err := w.Write([]byte(TOMLDelimUnix))
		if err != nil {
			return err
		}

		err = InterfaceToConfig(in, mark, w)

		if err != nil {
			return err
		}

		_, err = w.Write([]byte("\n" + TOMLDelimUnix))
		return err

	default:
		return InterfaceToConfig(in, mark, w)
	}
}

// FormatToLeadRune takes a given format kind and return the leading front
// matter delimiter.
func FormatToLeadRune(kind string) rune {
	switch FormatSanitize(kind) {
	case "yaml":
		return rune([]byte(YAMLLead)[0])
	case "json":
		return rune([]byte(JSONLead)[0])
	case "org":
		return '#'
	default:
		return rune([]byte(TOMLLead)[0])
	}
}

// FormatSanitize returns the canonical format name for a given kind.
//
// TODO(bep) move to helpers
func FormatSanitize(kind string) string {
	switch strings.ToLower(kind) {
	case "yaml", "yml":
		return "yaml"
	case "toml", "tml":
		return "toml"
	case "json", "js":
		return "json"
	case "org":
		return kind
	default:
		return "toml"
	}
}

// removeTOMLIdentifier removes, if necessary, beginning and ending TOML
// frontmatter delimiters from a byte slice.
func removeTOMLIdentifier(datum []byte) []byte {
	ld := len(datum)
	if ld < 8 {
		return datum
	}

	b := bytes.TrimPrefix(datum, []byte(TOMLDelim))
	if ld-len(b) != 3 {
		// No TOML prefix trimmed, so bail out
		return datum
	}

	b = bytes.Trim(b, "\r\n")
	return bytes.TrimSuffix(b, []byte(TOMLDelim))
}