@accordproject/markdown-common
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A framework for transforming markdown
296 lines (246 loc) • 9.3 kB
JavaScript
/*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
;
/**
* Converts a CommonMark DOM to a markdown string.
*
* Note that there are multiple ways of representing the same CommonMark DOM as text,
* so this transformation is not guaranteed to equivalent if you roundtrip
* markdown content. For example an H1 can be specified using either '#' or '='
* notation.
*
* The resulting AST *should* be equivalent however.
*/
class ToMarkdownStringVisitor {
/**
* Construct the visitor.
* @param {object} [options] configuration options
* @param {boolean} [options.noIndex] do not index ordered list (i.e., use 1. everywhere)
*/
constructor(options) {
this.options = options;
}
/**
* Visits a sub-tree and return the markdown
* @param {*} visitor - the visitor to use
* @param {*} thing - the node to visit
* @param {*} parameters - the current parameters
* @param {*} paramsFun - function to construct the parameters for children
* @returns {string} the markdown for the sub tree
*/
static visitChildren(visitor, thing, parameters, paramsFun) {
const paramsFunActual = paramsFun ? paramsFun : ToMarkdownStringVisitor.mkParameters;
const parametersIn = paramsFunActual(parameters);
if (thing.nodes) {
thing.nodes.forEach(node => {
node.accept(visitor, parametersIn);
});
}
return parametersIn.result;
}
/**
* Set parameters for general blocks
* @param {*} parametersOut - the current parameters
* @return {*} the new parameters with block quote level incremented
*/
static mkParameters(parametersOut) {
let parameters = {};
parameters.result = '';
parameters.first = false;
parameters.stack = parametersOut.stack.slice();
return parameters;
}
/**
* Set parameters for block quote
* @param {*} parametersOut - the current parameters
* @return {*} the new parameters with block quote level incremented
*/
static mkParametersInBlockQuote(parametersOut) {
let parameters = {};
parameters.result = '';
parameters.first = false;
parameters.stack = parametersOut.stack.slice();
parameters.stack.push('block');
return parameters;
}
/**
* Set parameters for inner list
* @param {*} parametersOut - the current parameters
* @return {*} the new parameters with first set to true
*/
static mkParametersInList(parametersOut) {
let parameters = {};
parameters.result = '';
parameters.first = true;
parameters.stack = parametersOut.stack.slice();
parameters.stack.push('list');
return parameters;
}
/**
* Create prefix
* @param {*} parameters - the parameters
* @param {*} newlines - number of newlines
* @return {string} the prefix
*/
static mkPrefix(parameters, newlines) {
const stack = parameters.stack;
const newlinesFix = parameters.first ? 0 : newlines;
let prefix = '';
for (let i = 0; i < stack.length; i++) {
if (stack[i] === 'list') {
prefix += ' ';
} else if (stack[i] === 'block') {
prefix += '> ';
}
}
return ('\n' + prefix).repeat(newlinesFix);
}
/**
* Create Setext heading
* @param {number} level - the heading level
* @return {string} the markup for the heading
*/
static mkSetextHeading(level) {
if (level === 1) {
return '====';
} else {
return '----';
}
}
/**
* Create ATX heading
* @param {number} level - the heading level
* @return {string} the markup for the heading
*/
static mkATXHeading(level) {
return Array(level).fill('#').join('');
}
/**
* Adding escapes for code blocks
* @param {string} input - unescaped
* @return {string} escaped
*/
static escapeCodeBlock(input) {
return input.replace(/`/g, '\\`');
}
/**
* Adding escapes for text nodes
* @param {string} input - unescaped
* @return {string} escaped
*/
static escapeText(input) {
return input.replace(/[*`#&]/g, '\\$&') // Replaces special characters
.replace(/^(\d+)\./g, '$1\\.') // Replaces ordered lists
.replace(/^-/g, '\\-'); // Replaces unordered lists
}
/**
* Visit a node
* @param {*} thing the object being visited
* @param {*} parameters the parameters
*/
visit(thing, parameters) {
const nodeText = thing.text ? thing.text : '';
switch (thing.getType()) {
case 'CodeBlock':
parameters.result += ToMarkdownStringVisitor.mkPrefix(parameters, 2);
parameters.result += "```".concat(thing.info ? ' ' + thing.info : '', "\n").concat(ToMarkdownStringVisitor.escapeCodeBlock(thing.text), "```");
break;
case 'Code':
parameters.result += "`".concat(nodeText, "`");
break;
case 'HtmlInline':
parameters.result += nodeText;
break;
case 'Emph':
parameters.result += "*".concat(ToMarkdownStringVisitor.visitChildren(this, thing, parameters), "*");
break;
case 'Strong':
parameters.result += "**".concat(ToMarkdownStringVisitor.visitChildren(this, thing, parameters), "**");
break;
case 'BlockQuote':
parameters.result += ToMarkdownStringVisitor.visitChildren(this, thing, parameters, ToMarkdownStringVisitor.mkParametersInBlockQuote);
break;
case 'Heading':
{
const level = parseInt(thing.level);
if (level < 3) {
parameters.result += ToMarkdownStringVisitor.mkPrefix(parameters, 2);
parameters.result += ToMarkdownStringVisitor.visitChildren(this, thing, parameters);
parameters.result += ToMarkdownStringVisitor.mkPrefix(parameters, 1);
parameters.result += ToMarkdownStringVisitor.mkSetextHeading(level);
} else {
parameters.result += ToMarkdownStringVisitor.mkPrefix(parameters, 2);
parameters.result += ToMarkdownStringVisitor.mkATXHeading(level);
parameters.result += ' ';
parameters.result += ToMarkdownStringVisitor.visitChildren(this, thing, parameters);
}
}
break;
case 'ThematicBreak':
parameters.result += ToMarkdownStringVisitor.mkPrefix(parameters, 2);
parameters.result += '---';
break;
case 'Linebreak':
parameters.result += '\\';
parameters.result += ToMarkdownStringVisitor.mkPrefix(parameters, 1);
break;
case 'Softbreak':
parameters.result += ToMarkdownStringVisitor.mkPrefix(parameters, 1);
break;
case 'Link':
parameters.result += "[".concat(ToMarkdownStringVisitor.visitChildren(this, thing, parameters), "](").concat(thing.destination, " \"").concat(thing.title ? thing.title : '', "\")");
break;
case 'Image':
parameters.result += "![".concat(ToMarkdownStringVisitor.visitChildren(this, thing, parameters), "](").concat(thing.destination, " \"").concat(thing.title ? thing.title : '', "\")");
break;
case 'Paragraph':
parameters.result += ToMarkdownStringVisitor.mkPrefix(parameters, 2);
parameters.result += "".concat(ToMarkdownStringVisitor.visitChildren(this, thing, parameters));
break;
case 'HtmlBlock':
parameters.result += ToMarkdownStringVisitor.mkPrefix(parameters, 2);
parameters.result += nodeText;
break;
case 'Text':
parameters.result += ToMarkdownStringVisitor.escapeText(nodeText);
break;
case 'List':
{
const first = thing.start ? parseInt(thing.start) : 1;
let index = first;
thing.nodes.forEach(item => {
if (thing.tight === 'false' && index !== first) {
parameters.result += '\n';
}
if (thing.type === 'ordered') {
parameters.result += "".concat(ToMarkdownStringVisitor.mkPrefix(parameters, 1)).concat(this.options.noIndex ? 1 : index, ". ").concat(ToMarkdownStringVisitor.visitChildren(this, item, parameters, ToMarkdownStringVisitor.mkParametersInList));
} else {
parameters.result += "".concat(ToMarkdownStringVisitor.mkPrefix(parameters, 1), "- ").concat(ToMarkdownStringVisitor.visitChildren(this, item, parameters, ToMarkdownStringVisitor.mkParametersInList));
}
index++;
});
}
break;
case 'Item':
throw new Error('Item node should not occur outside of List nodes');
case 'Document':
parameters.result += ToMarkdownStringVisitor.visitChildren(this, thing, parameters);
break;
default:
throw new Error("Unhandled type ".concat(thing.getType()));
}
parameters.first = false;
}
}
module.exports = ToMarkdownStringVisitor;