| 1 | 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vm from 'vm';\nimport url from 'url';\n\nimport request from 'request';\nimport cheerio from 'cheerio';\n\n/**\n * A request promise wrapper.\n *\n * @param req Request function.\n * @param options Request options.\n * @returns Request response and body.\n */\nasync function requestP(\n\treq: typeof request,\n\toptions: request.OptionsWithUrl\n) {\n\tconst r = await new Promise<{\n\n\t\t/**\n\t\t * Response object.\n\t\t */\n\t\tresponse: request.Response;\n\n\t\t/**\n\t\t * Response body.\n\t\t */\n\t\tbody: any;\n\t}>((resolve, reject) => {\n\t\treq(options, (error, response, body) => {\n\t\t\tif (error) {\n\t\t\t\treject(error);\n\t\t\t\treturn;\n\t\t\t}\n\t\t\tresolve({\n\t\t\t\tresponse,\n\t\t\t\tbody\n\t\t\t});\n\t\t});\n\t});\n\treturn r;\n}\n\n/**\n * Extract script code from HTML code.\n *\n * @param html HTML code.\n * @returns Script code.\n */\nfunction extractScripts(html: string) {\n\tconst r: string[] = [];\n\tconst $ = cheerio.load(html);\n\t$('script').each((elI, el) => {\n\t\tconst data = $(el).html();\n\t\tif (data) {\n\t\t\tr.push(data);\n\t\t}\n\t});\n\treturn r;\n}\n\n/**\n * Attempt to extract info from script.\n *\n * @param script Script code.\n * @returns Result object or null.\n */\nfunction extractScript(script: string) {\n\tlet result: object | null = null;\n\tif (!script.includes('dlbutton')) {\n\t\treturn result;\n\t}\n\n\t// Create a context with wich to run code in\n\t// Creating the object with a null prototype is very important.\n\t// Prevents host variables from leaking into the sanbox.\n\tconst ctx = vm.createContext(Object.create(null));\n\tconst runOpts = {\n\t\ttimeout: 1000\n\t};\n\n\t// Setup environment.\n\tconst codePre = [\n\t\t/* eslint-disable @typescript-eslint/indent */\n\t\t'window = this;',\n\t\t'document = (function(r) {',\n\t\t\t'var elements = {',\n\t\t\t\t'\"dlbutton\": {},',\n\t\t\t\t'\"fimage\": {}',\n\t\t\t'};',\n\t\t\t'r.getElementById = function(id) {',\n\t\t\t\t'return elements[id];',\n\t\t\t'}',\n\t\t\t'return r;',\n\t\t'})({});'\n\t\t/* eslint-enable @typescript-eslint/indent */\n\t].join('\\n');\n\n\t// Extract info from environment.\n\tconst codePost = [\n\t\t/* eslint-disable @typescript-eslint/indent */\n\t\t'JSON.stringify({',\n\t\t\t'\"dlbutton\": document.getElementById(\"dlbutton\").href',\n\t\t'})'\n\t\t/* eslint-enable @typescript-eslint/indent */\n\t].join('\\n');\n\n\t// Attempt to run code in sanbox and extract the info.\n\ttry {\n\t\t// Run the pre script.\n\t\tvm.runInContext(codePre, ctx, runOpts);\n\n\t\t// Run the script code.\n\t\tvm.runInContext(script, ctx, runOpts);\n\n\t\t// Run the post script.\n\t\t// Force return value to be string, with concatenation, NOT casting.\n\t\t// This prevents any funny business from sandboxed code.\n\t\t// eslint-disable-next-line\n\t\tresult = JSON.parse('' + vm.runInContext(codePost, ctx, runOpts));\n\t}\n\tcatch (err) {\n\t\t// Ignore failure.\n\t}\n\treturn result;\n}\n\n/**\n * Extract file info from a URL.\n *\n * @param uri The URI to extract info from.\n * @param req Optional custom request function or null.\n * @returns File info.\n */\nexport async function extract(\n\turi: string,\n\treq: typeof request | null = null\n) {\n\tconst requester = req || request;\n\tconst {response, body} = await requestP(requester, {\n\t\turl: uri\n\t});\n\tconst {statusCode} = response;\n\tif (statusCode !== 200) {\n\t\tthrow new Error(`Invalid status code: ${statusCode}`);\n\t}\n\tconst bodyType = typeof body;\n\tif (bodyType !== 'string') {\n\t\tthrow new Error(`Invalid body type: ${bodyType}`);\n\t}\n\n\tconst scripts = extractScripts(body);\n\tlet result: any | null = null;\n\tfor (const script of scripts) {\n\t\tresult = extractScript(script);\n\t\tif (result) {\n\t\t\tbreak;\n\t\t}\n\t}\n\tif (!result || !result.dlbutton) {\n\t\tthrow new Error('Failed to extract info');\n\t}\n\n\tconst download = url.resolve(uri, result.dlbutton);\n\tconst filename = decodeURI(\n\t\t(url.parse(download).pathname || '').split('/').pop() || ''\n\t) || null;\n\n\treturn {\n\t\tdownload,\n\t\tfilename\n\t};\n}\n"],"file":"extract.js","sourceRoot":"../src"} |