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get-page-table-of-contents.ts
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get-page-table-of-contents.ts
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import * as types from 'notion-types'
import { getTextContent } from './get-text-content'
export interface TableOfContentsEntry {
id: types.ID
type: types.BlockType
text: string
indentLevel: number
}
const indentLevels = {
header: 0,
sub_header: 1,
sub_sub_header: 2
}
/**
* Gets the metadata for a table of contents block by parsing the page's
* H1, H2, and H3 elements.
*/
export const getPageTableOfContents = (
page: types.PageBlock,
recordMap: types.ExtendedRecordMap
): Array<TableOfContentsEntry> => {
const toc = (page.content ?? [])
.map((blockId: string) => {
const block = recordMap.block[blockId]?.value
if (block) {
const { type } = block
if (
type === 'header' ||
type === 'sub_header' ||
type === 'sub_sub_header'
) {
return {
id: blockId,
type,
text: getTextContent(block.properties?.title),
indentLevel: indentLevels[type]
}
}
}
return null
})
.filter(Boolean) as Array<TableOfContentsEntry>
const indentLevelStack = [
{
actual: -1,
effective: -1
}
]
// Adjust indent levels to always change smoothly.
// This is a little tricky, but the key is that when increasing indent levels,
// they should never jump more than one at a time.
for (const tocItem of toc) {
const { indentLevel } = tocItem
const actual = indentLevel
do {
const prevIndent = indentLevelStack[indentLevelStack.length - 1]
const { actual: prevActual, effective: prevEffective } = prevIndent
if (actual > prevActual) {
tocItem.indentLevel = prevEffective + 1
indentLevelStack.push({
actual,
effective: tocItem.indentLevel
})
} else if (actual === prevActual) {
tocItem.indentLevel = prevEffective
break
} else {
indentLevelStack.pop()
}
// eslint-disable-next-line no-constant-condition
} while (true)
}
return toc
}