30 lines
1.2 KiB
TypeScript
30 lines
1.2 KiB
TypeScript
/**
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* Return the Markdown source used by preview renderers.
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*
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* A closed YAML frontmatter block is metadata, but the shared MarkdownText
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* parser treats its delimiters as a thematic break and a setext heading. Hide
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* only a block that starts on the first line and has its own closing `---`
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* line. Unclosed or non-leading delimiters remain byte-for-byte unchanged so
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* ordinary Markdown is never truncated. The editor and save path keep using
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* the original source; this helper is preview-only.
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*/
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export function markdownPreviewSource(source: string): string {
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const firstLineEnd = source.indexOf('\n')
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if (firstLineEnd === -1) return source
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const firstLineStart = source.charCodeAt(0) === 0xFEFF ? 1 : 0
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const firstLine = source.slice(firstLineStart, firstLineEnd).replace(/\r$/u, '')
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if (firstLine !== '---') return source
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let lineStart = firstLineEnd + 1
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while (lineStart <= source.length) {
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const newline = source.indexOf('\n', lineStart)
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const lineEnd = newline === -1 ? source.length : newline
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const line = source.slice(lineStart, lineEnd).replace(/\r$/u, '')
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if (line === '---') return newline === -1 ? '' : source.slice(newline + 1)
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if (newline === -1) return source
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lineStart = newline + 1
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}
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return source
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}
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