core/render/blocknote.go

package render

import (
	"encoding/json"
	"fmt"
	"html"
	"strings"
)

// BlockNoteToHTML converts a BlockNote document (map with "blocks" key) to HTML.
func BlockNoteToHTML(doc map[string]any) string {
	blocks := blocksFromRaw(doc["blocks"])
	if len(blocks) == 0 {
		return ""
	}
	return renderBlocks(blocks)
}

func renderBlocks(blocks []any) string {
	var sb strings.Builder
	var currentListType string
	var listItems []map[string]any

	flushList := func() {
		if len(listItems) == 0 {
			return
		}
		tag := "ul"
		listStyle := "list-disc"
		if currentListType == "numberedListItem" {
			tag = "ol"
			listStyle = "list-decimal"
		}
		fmt.Fprintf(&sb, "<%s class=\"my-4 pl-6 space-y-2 %s\">\n", tag, listStyle)
		for _, item := range listItems {
			content := inlineContentFromRaw(item["content"])
			childrenHTML := renderChildren(item["children"])
			sb.WriteString("<li>")
			sb.WriteString(renderInlineContent(content))
			if childrenHTML != "" {
				sb.WriteString(childrenHTML)
			}
			sb.WriteString("</li>\n")
		}
		fmt.Fprintf(&sb, "</%s>\n", tag)
		listItems = nil
		currentListType = ""
	}

	for _, block := range blocks {
		blockMap, ok := block.(map[string]any)
		if !ok {
			continue
		}
		blockType, _ := blockMap["type"].(string)

		if blockType == "bulletListItem" || blockType == "numberedListItem" {
			if currentListType != "" && currentListType != blockType {
				flushList()
			}
			currentListType = blockType
			listItems = append(listItems, blockMap)
			continue
		}

		flushList()
		sb.WriteString(renderBlock(blockMap))
	}

	flushList()
	return sb.String()
}

func inlineContentFromRaw(raw any) []any {
	switch v := raw.(type) {
	case []any:
		return v
	case []map[string]any:
		items := make([]any, 0, len(v))
		for _, item := range v {
			items = append(items, item)
		}
		return items
	case string:
		if v == "" {
			return nil
		}
		return []any{map[string]any{"type": "text", "text": v}}
	default:
		return nil
	}
}

func blocksFromRaw(raw any) []any {
	switch v := raw.(type) {
	case []any:
		return v
	case []map[string]any:
		items := make([]any, 0, len(v))
		for _, item := range v {
			items = append(items, item)
		}
		return items
	default:
		return nil
	}
}

func renderBlock(block map[string]any) string {
	blockType, _ := block["type"].(string)
	props, _ := block["props"].(map[string]any)
	content := inlineContentFromRaw(block["content"])
	childrenHTML := renderChildren(block["children"])

	var sb strings.Builder

	switch blockType {
	case "paragraph":
		sb.WriteString("<p class=\"my-4\">")
		sb.WriteString(renderInlineContent(content))
		if childrenHTML != "" {
			sb.WriteString(childrenHTML)
		}
		sb.WriteString("</p>\n")

	case "heading":
		level := 2
		if l, ok := props["level"].(float64); ok {
			level = int(l)
		} else if l, ok := props["level"].(int); ok {
			level = l
		}
		if level < 1 {
			level = 1
		}
		if level > 6 {
			level = 6
		}
		fmt.Fprintf(&sb, "<h%d class=\"mt-8 mb-4 font-bold\">", level)
		sb.WriteString(renderInlineContent(content))
		if childrenHTML != "" {
			sb.WriteString(childrenHTML)
		}
		fmt.Fprintf(&sb, "</h%d>\n", level)

	case "quote":
		sb.WriteString("<blockquote class=\"my-4 border-l-4 border-border pl-4 text-muted-foreground\">")
		sb.WriteString(renderInlineContent(content))
		if childrenHTML != "" {
			sb.WriteString(childrenHTML)
		}
		sb.WriteString("</blockquote>\n")

	case "codeBlock":
		lang := ""
		if l, ok := props["language"].(string); ok {
			lang = l
		}
		fmt.Fprintf(&sb, `<pre class="my-4"><code class="language-%s">`, html.EscapeString(lang))
		sb.WriteString(renderInlineContent(content))
		sb.WriteString("</code></pre>\n")

	case "image":
		url := ""
		caption := ""
		alt := ""
		if u, ok := props["url"].(string); ok {
			url = u
		}
		if c, ok := props["caption"].(string); ok {
			caption = c
		}
		if a, ok := props["alt"].(string); ok {
			alt = a
		}
		if alt == "" {
			alt = caption
		}
		sb.WriteString(`<figure class="my-6">`)
		fmt.Fprintf(&sb, `<img src="%s" alt="%s" />`, html.EscapeString(url), html.EscapeString(alt))
		if caption != "" {
			fmt.Fprintf(&sb, "<figcaption>%s</figcaption>", html.EscapeString(caption))
		}
		sb.WriteString("</figure>\n")

	case "table":
		sb.WriteString(`<div class="overflow-x-auto my-6"><table class="min-w-full border-collapse border border-border">`)
		if tableContent, ok := block["content"].(map[string]any); ok {
			if rows, ok := tableContent["rows"].([]any); ok && len(rows) > 0 {
				renderTableRow := func(row any, isHeader bool) {
					if rowMap, ok := row.(map[string]any); ok {
						if cells, ok := rowMap["cells"].([]any); ok {
							for _, cell := range cells {
								cellTag := "td"
								cellClass := "px-4 py-2 text-sm"
								if isHeader {
									cellTag = "th"
									cellClass = "px-4 py-3 text-left text-sm font-semibold"
								}
								fmt.Fprintf(&sb, "<%s class=\"%s\">", cellTag, cellClass)
								sb.WriteString(renderInlineContent(inlineContentFromRaw(cell)))
								fmt.Fprintf(&sb, "</%s>", cellTag)
							}
						}
					}
				}
				sb.WriteString("<thead><tr class=\"bg-muted\">")
				renderTableRow(rows[0], true)
				sb.WriteString("</tr></thead>")
				if len(rows) > 1 {
					sb.WriteString("<tbody>")
					for _, row := range rows[1:] {
						sb.WriteString("<tr class=\"border-b border-border\">")
						renderTableRow(row, false)
						sb.WriteString("</tr>")
					}
					sb.WriteString("</tbody>")
				}
			}
		}
		sb.WriteString("</table></div>\n")

	case "references":
		sb.WriteString("<div class=\"bn-references\">\n")
		sb.WriteString("<div class=\"bn-references-label\">References</div>\n")
		sb.WriteString("<ol>\n")
		if itemsJSON, ok := props["items"].(string); ok && itemsJSON != "" {
			var items []map[string]string
			if err := json.Unmarshal([]byte(itemsJSON), &items); err == nil {
				for _, item := range items {
					text := html.EscapeString(item["text"])
					url := item["url"]
					if text == "" {
						continue
					}
					if url != "" {
						fmt.Fprintf(&sb, "<li><a href=\"%s\">%s</a></li>\n", html.EscapeString(url), text)
					} else {
						fmt.Fprintf(&sb, "<li>%s</li>\n", text)
					}
				}
			}
		}
		sb.WriteString("</ol>\n</div>\n")

	default:
		if len(content) > 0 || childrenHTML != "" {
			sb.WriteString("<div>")
			sb.WriteString(renderInlineContent(content))
			if childrenHTML != "" {
				sb.WriteString(childrenHTML)
			}
			sb.WriteString("</div>\n")
		}
	}

	return sb.String()
}

func renderChildren(children any) string {
	blocks := blocksFromRaw(children)
	if len(blocks) == 0 {
		return ""
	}
	return renderBlocks(blocks)
}

func renderInlineContent(content []any) string {
	var sb strings.Builder
	for _, item := range content {
		itemMap, ok := item.(map[string]any)
		if !ok {
			continue
		}

		itemType, _ := itemMap["type"].(string)
		text, _ := itemMap["text"].(string)
		styles, _ := itemMap["styles"].(map[string]any)

		switch itemType {
		case "text":
			rendered := html.EscapeString(text)
			if styles != nil {
				if bold, ok := styles["bold"].(bool); ok && bold {
					rendered = "<strong>" + rendered + "</strong>"
				}
				if italic, ok := styles["italic"].(bool); ok && italic {
					rendered = "<em>" + rendered + "</em>"
				}
				if underline, ok := styles["underline"].(bool); ok && underline {
					rendered = "<u>" + rendered + "</u>"
				}
				if strike, ok := styles["strike"].(bool); ok && strike {
					rendered = "<s>" + rendered + "</s>"
				}
				if strike, ok := styles["strikethrough"].(bool); ok && strike {
					rendered = "<s>" + rendered + "</s>"
				}
				if code, ok := styles["code"].(bool); ok && code {
					rendered = "<code>" + rendered + "</code>"
				}
			}
			sb.WriteString(rendered)

		case "link":
			href, _ := itemMap["href"].(string)
			linkContent := inlineContentFromRaw(itemMap["content"])
			if href == "" {
				sb.WriteString(renderInlineContent(linkContent))
				break
			}
			fmt.Fprintf(&sb, `<a href="%s">`, html.EscapeString(href))
			sb.WriteString(renderInlineContent(linkContent))
			sb.WriteString("</a>")

		case "hardBreak":
			sb.WriteString("<br />")

		default:
			if text != "" {
				sb.WriteString(html.EscapeString(text))
				break
			}
			if rawContent, ok := itemMap["content"]; ok {
				sb.WriteString(renderInlineContent(inlineContentFromRaw(rawContent)))
			}
		}
	}
	return sb.String()
}