markdown.go

package goeditorjs

import (
	"fmt"
	"strings"
)

// MarkdownEngine is the engine that creates the HTML from EditorJS blocks
type MarkdownEngine struct {
	BlockHandlers map[string]MarkdownBlockHandler
}

// MarkdownBlockHandler is an interface for a plugable EditorJS HTML generator
type MarkdownBlockHandler interface {
	Type() string // Type returns the type the block handler supports as a string
	GenerateMarkdown(editorJSBlock EditorJSBlock) (string, error)
}

// NewMarkdownEngine creates a new MarkdownEngine
func NewMarkdownEngine() *MarkdownEngine {
	bhs := make(map[string]MarkdownBlockHandler)
	return &MarkdownEngine{BlockHandlers: bhs}
}

// RegisterBlockHandlers registers or overrides a block handlers for blockType given by MarkdownBlockHandler.Type()
func (markdownEngine *MarkdownEngine) RegisterBlockHandlers(handlers ...MarkdownBlockHandler) {
	for _, bh := range handlers {
		markdownEngine.BlockHandlers[bh.Type()] = bh
	}
}

// GenerateMarkdown generates markdown from the editorJS using configured set of markdown handlers
func (markdownEngine *MarkdownEngine) GenerateMarkdown(editorJSData string) (string, error) {
	results := []string{}
	ejs, err := parseEditorJSON(editorJSData)
	if err != nil {
		return "", err
	}
	for _, block := range ejs.Blocks {
		if generator, ok := markdownEngine.BlockHandlers[block.Type]; ok {
			md, err := generator.GenerateMarkdown(block)
			if err != nil {
				return "", err
			}
			results = append(results, md)
		} else {
			return "", fmt.Errorf("%w, Block Type: %s", ErrBlockHandlerNotFound, block.Type)
		}
	}

	return strings.Join(results, "\n\n"), nil
}