craftBlockToMarkdown

/**
  Craft's markdown api has the following problems.
    1. Nested lists are not supported.
    2. The order of Nested blockquote and is incorrectly.
    3. only the latter will be recognized as a reference block.
    4. urlBlock (may called 'bookmark'?) will be recognized as a link（in this function, you can custom render tag of jekyll, you can modify this as you wish)
  Note:
    1. not support toggle/formula, because markdown not support those too, but you can make it.
    2. I use this function for may jekyll blog workflow, you can modify it to fit your workflow.
    3. caption（#####） is used for image caption if it is right next to the image(in my case, it not render as `###### xxx`).
  Usage: use `craft.dataApi.getCurrentPage()` first, get the result, then invoke `result.subblocks.map(craftBlockToMarkdown).filter(Boolean).join('\n')` to get the markdown
*/
const inlineText = (content = []) => {
    return content.reduce((pre, curr) => {
        let result = '';
        if (curr.link) {
            result += '['
        }
        if (curr.isCode) {
            result += '`';
        }
        if (curr.isBold) {
            result += '**';
        }
        if (curr.isStrikethrough) {
            result += '~~';
        }
        if (curr.isItalic) {
            result += '*';
        }
        result += curr.text;
        if (curr.isItalic) {
            result += '*';
        }
        if (curr.isStrikethrough) {
            result += '~~';
        }
        if (curr.isBold) {
            result += '**';
        }
        if (curr.isCode) {
            result += '`';
        }
        if (curr.link) {
            result += `](${curr.link.url})`;
        }
        return `${pre}${result}`
    }, '') || ''
}

const craftBlockToMarkdown = (block, key, blocks) => {
    let indent = '';
    for (let i = 0; i < block.indentationLevel; i++) {
        indent += `    `;
    }
    switch (block.type) {
        case 'textBlock': {
            if (!block.content) {
                console.log(`no content in ${key}`)
                return;
            }
            let symbol = '';
            if (block.listStyle?.type && block.listStyle.type !== 'none') {
                let blockquote = '';
                if (block.hasBlockDecoration || block.hasFocusDecoration) {
                    blockquote = '> '
                }
                switch (block.listStyle?.type) {
                    case 'todo': {
                        symbol = block.listStyle.state === 'checked' ? '- [x] ' : '- [ ] ';
                        break;
                    }
                    case 'toggle': {
                        break;
                    }
                    case 'bullet': {
                        symbol = '* '
                        break;
                    }
                    case 'numbered': {
                        symbol = '1. ';
                    }
                }
                return indent + blockquote + symbol + inlineText(block.content) + '\n';
            }
            if (block.hasBlockDecoration || block.hasFocusDecoration) {
                return indent + `> ${inlineText(block.content)}\n`
            }
            switch (block.style?.textStyle) {
                case 'title': {
                    return `${indent}# ${inlineText(block.content)}\n`;
                }
                case 'subtitle': {
                    return `${indent}## ${inlineText(block.content)}\n`;
                }
                case 'heading': {
                    return `${indent}### ${inlineText(block.content)}\n`;
                }
                case 'strong': {
                    return `${indent}#### ${inlineText(block.content)}\n`;
                }
                case 'body': {
                    return `${indent}${inlineText(block.content)}\n`;
                }
                // used for image caption
                case 'caption': {
                    return '';
                }
                case 'page':
                case 'card': {
                    return `${indent}${inlineText(block.content)}\n\n${block.subblocks?.map(craftBlockToMarkdown).filter(Boolean).join('\n')}`;
                }
            }
        }
        case 'horizontalLineBlock': {
            return '---\n' 
        }
        case 'tableBlock': {
            return craft.markdown.craftBlockToMarkdown([block], 'common', {
                tableSupported: true,
            }) + '\n';
        }
        case 'imageBlock': {
            const next = blocks[key + 1];
            if (next?.style?.textStyle === 'caption') {
                return `{% render_caption caption="${next.content[0]?.text}" %}\n![${block.filename || '__Unsplash__'}](${block.url}){% endrender_caption %}\n`
            }
            return `![${block.filename || 'Unsplash'}](${block.url})\n`;
        }
        case 'codeBlock': {
            if (block.language === 'math_formula') {
                // Note: markdown not support formula
            }
            return indent + `\`\`\`${block.language}\n${indent}${block.code}\n${indent}\`\`\`\n`;
        }
        case 'urlBlock': {
            // render as jekyll custom tag, you can modify this as you wish
            return `{% render_bookmark url="${block.url}" title="${block.title}" img="${block.imageUrl || '__no__img__'}" %}\n${block.pageDescription || ''}\n{% endrender_bookmark %}\n`;
        }
        case 'urlBlock': {
            // Note: render as jekyll custom tag, you can modify this as you wish
            // youtube and bilibili link support
            // urlBlock has 'url' which the url may redirect  and the 'originalUrl' has the original url.
            let url = new URL(block.url || block.originalUrl);
            let yid = '';
            let bid = '';
            if (url.hostname === 'www.youtube.com') {
                for (let i of url.searchParams) {
                    if (i[0] === 'v') {
                        yid = i[1];
                    }
                }
            } else if (url.hostname === 'www.bilibili.com') {
                bid = url.pathname.split('/').filter(Boolean)[1];
            }
            return `{% render_bookmark url="${block.url}" title="${block.title || ''}" img="${block.imageUrl || ''}" yid="${yid}" bid="${bid}" %}\n${block.pageDescription || ''}\n{% endrender_bookmark %}\n`;
        }
        case 'fileBlock': {
          // file attachment not support in markdown
          return ''
        }
        case 'videoBlock': {
            if (block.filename) {
                let filename = block.filename;
                let suffix = '';
                let arr = filename.split('.');
                if (arr.length > 1) {
                    filename = arr.slice(0, arr.length - 1).join('');
                    suffix = arr[arr.length - 1];
                }
                return `{% render_video caption="${filename}" img="${block.url}" suffix="${suffix}" %}\n![${filename}](${block.url})\n{% endrender_video %}\n`
            }
        }
    };
};