runCode.ts

// deno-lint-ignore-file no-explicit-any
import { loadPyodide, type PyodideInterface } from 'pyodide'
import { preparePythonCode } from './prepareEnvCode.ts'
import type { LoggingLevel } from '@modelcontextprotocol/sdk/types.js'

export interface CodeFile {
  name: string
  content: string
}

interface PrepResult {
  pyodide: PyodideInterface
  preparePyEnv: PreparePyEnv
  sys: any
  prepareStatus: PrepareSuccess | PrepareError
}

export class RunCode {
  private output: string[] = []
  private pyodide?: PyodideInterface
  private preparePyEnv?: PreparePyEnv
  private prepPromise?: Promise<PrepResult>

  async run(
    dependencies: string[],
    indexUrls: string[],
    log: (level: LoggingLevel, data: string) => void,
    file?: CodeFile,
    globals?: Record<string, any>,
    alwaysReturnJson: boolean = false,
  ): Promise<RunSuccess | RunError> {
    let pyodide: PyodideInterface
    let sys: any
    let prepareStatus: PrepareSuccess | PrepareError | undefined
    let preparePyEnv: PreparePyEnv
    if (this.pyodide && this.preparePyEnv) {
      pyodide = this.pyodide
      preparePyEnv = this.preparePyEnv
      sys = pyodide.pyimport('sys')
    } else {
      if (!this.prepPromise) {
        this.prepPromise = this.prepEnv(dependencies, indexUrls, log)
      }
      // TODO is this safe if the promise has already been accessed? it seems to work fine
      const prep = await this.prepPromise
      pyodide = prep.pyodide
      preparePyEnv = prep.preparePyEnv
      sys = prep.sys
      prepareStatus = prep.prepareStatus
    }

    if (prepareStatus && prepareStatus.kind == 'error') {
      return {
        status: 'install-error',
        output: this.takeOutput(sys),
        error: prepareStatus.message,
      }
    } else if (file) {
      try {
        const rawValue = await pyodide.runPythonAsync(file.content, {
          globals: pyodide.toPy({ ...(globals || {}), __name__: '__main__' }),
          filename: file.name,
        })
        return {
          status: 'success',
          output: this.takeOutput(sys),
          returnValueJson: preparePyEnv.dump_json(rawValue, alwaysReturnJson),
        }
      } catch (err) {
        return {
          status: 'run-error',
          output: this.takeOutput(sys),
          error: formatError(err),
        }
      }
    } else {
      return {
        status: 'success',
        output: this.takeOutput(sys),
        returnValueJson: null,
      }
    }
  }

  async prepEnv(
    dependencies: string[],
    indexUrls: string[],
    log: (level: LoggingLevel, data: string) => void,
  ): Promise<PrepResult> {
    const pyodide = await loadPyodide({
      stdout: (msg) => {
        log('info', msg)
        this.output.push(msg)
      },
      stderr: (msg) => {
        log('warning', msg)
        this.output.push(msg)
      },
    })

    // see https://github.com/pyodide/pyodide/discussions/5512
    const origLoadPackage = pyodide.loadPackage
    pyodide.loadPackage = (pkgs, options) =>
      origLoadPackage(pkgs, {
        // stop pyodide printing to stdout/stderr
        messageCallback: (msg: string) => log('debug', msg),
        errorCallback: (msg: string) => {
          log('error', msg)
          this.output.push(`install error: ${msg}`)
        },
        ...options,
      })

    await pyodide.loadPackage(['micropip', 'pydantic'])
    const sys = pyodide.pyimport('sys')

    const dirPath = '/tmp/mcp_run_python'
    sys.path.append(dirPath)
    const pathlib = pyodide.pyimport('pathlib')
    pathlib.Path(dirPath).mkdir()
    const moduleName = '_prepare_env'

    pathlib.Path(`${dirPath}/${moduleName}.py`).write_text(preparePythonCode)

    const preparePyEnv: PreparePyEnv = pyodide.pyimport(moduleName)

    const prepareStatus = await preparePyEnv.prepare_env(
      pyodide.toPy(dependencies),
      pyodide.toPy(indexUrls),
    )
    return {
      pyodide,
      preparePyEnv,
      sys,
      prepareStatus,
    }
  }

  private takeOutput(sys: any): string[] {
    sys.stdout.flush()
    sys.stderr.flush()
    const output = this.output
    this.output = []
    return output
  }
}

interface RunSuccess {
  status: 'success'
  // we could record stdout and stderr separately, but I suspect simplicity is more important
  output: string[]
  returnValueJson: string | null
}

interface RunError {
  status: 'install-error' | 'run-error'
  output: string[]
  error: string
}

export function asXml(runResult: RunSuccess | RunError): string {
  const xml = [`<status>${runResult.status}</status>`]
  if (runResult.output.length) {
    xml.push('<output>')
    const escapeXml = escapeClosing('output')
    xml.push(...runResult.output.map(escapeXml))
    xml.push('</output>')
  }
  if (runResult.status == 'success') {
    if (runResult.returnValueJson) {
      xml.push('<return_value>')
      xml.push(escapeClosing('return_value')(runResult.returnValueJson))
      xml.push('</return_value>')
    }
  } else {
    xml.push('<error>')
    xml.push(escapeClosing('error')(runResult.error))
    xml.push('</error>')
  }
  return xml.join('\n')
}

export function asJson(runResult: RunSuccess | RunError): string {
  const { status, output } = runResult
  const json: Record<string, any> = { status, output }
  if (runResult.status == 'success') {
    json.return_value = JSON.parse(runResult.returnValueJson || 'null')
  } else {
    json.error = runResult.error
  }
  return JSON.stringify(json)
}

function escapeClosing(closingTag: string): (str: string) => string {
  const regex = new RegExp(`</?\\s*${closingTag}(?:.*?>)?`, 'gi')
  const onMatch = (match: string) => {
    return match.replace(/</g, '&lt;').replace(/>/g, '&gt;')
  }
  return (str) => str.replace(regex, onMatch)
}

function formatError(err: any): string {
  let errStr = err.toString()
  errStr = errStr.replace(/^PythonError: +/, '')
  // remove frames from inside pyodide
  errStr = errStr.replace(
    / {2}File "\/lib\/python\d+\.zip\/_pyodide\/.*\n {4}.*\n(?: {4}.*\n)*/g,
    '',
  )
  return errStr
}

interface PrepareSuccess {
  kind: 'success'
  dependencies?: string[]
}
interface PrepareError {
  kind: 'error'
  message: string
}
interface PreparePyEnv {
  prepare_env: (dependencies: any, index_urls: any) => Promise<PrepareSuccess | PrepareError>
  dump_json: (value: any, always_return_json: boolean) => string | null
}