/** Select source or built bootstrap assets in the mounted execution world. */
import { dirname, isAbsolute, resolve } from 'node:path'
import { fileURLToPath, pathToFileURL } from 'node:url'
import type { FileSystem } from '@deepseek-ai/dsh-fs'
import { assertNever } from '@deepseek-ai/dsh-util-values'

/** Deployment-owned worker invocation in the subprocess execution world. */
export type LaunchConfig = {
  /** Start a separately installed Node executable and JavaScript bootstrap. */
  kind: 'node-script'
  /** Executable name or path resolved by the subprocess provider. */
  executable: string
  /** Absolute preinstalled bootstrap; omitted maps this package's bootstrap into the execution world. */
  bootstrapPath?: string
} | {
  /** Start the private PTC worker embedded in a packaged executable. */
  kind: 'embedded'
  /** Packaged executable name or path resolved by the subprocess provider. */
  executable: string
}

/**
 * Resolve the local carrier default or validate an explicit execution-world invocation.
 * @param config - explicit remote or local worker configuration; omitted selects this carrier.
 * @returns the worker invocation without guessing from the execution world's paths.
 */
export function resolveLaunch(config?: LaunchConfig): LaunchConfig {
  const launch: LaunchConfig = config ?? { kind: 'pkg' in process ? 'embedded' : 'node-script', executable: process.execPath }
  if (launch.executable.length === 0) throw new Error('ptc-runtime-node: launch.executable must be non-empty')
  if (launch.kind === 'node-script' && launch.bootstrapPath !== undefined && !isAbsolute(launch.bootstrapPath)) {
    throw new Error('ptc-runtime-node: launch.bootstrapPath must be absolute')
  }
  return launch
}

/**
 * Select explicit arguments without inheriting host loader or inspector flags.
 * @param fs - Filesystem mapping host bootstrap assets into the process world.
 * @param config - resolved worker invocation.
 * @param maxMessageBytes - Validated message and queued-write limit.
 * @param persistent - Select the in-memory REPL bootstrap instead of the one-shot evaluator.
 * @returns Arguments following the resolved Node executable.
 */
export function bootstrapArgs(fs: Pick<FileSystem, 'processPathFromHostPath'>, config: LaunchConfig, maxMessageBytes: number, persistent = false): string[] {
  switch (config.kind) {
    case 'embedded':
      if (persistent) throw new Error('Persistent PTC requires a node-script launch')
      return [String(maxMessageBytes)]
    case 'node-script': return scriptBootstrapArgs(fs, config.bootstrapPath, maxMessageBytes, persistent)
    /* v8 ignore next -- Callers supply the resolved, closed LaunchConfig union. */
    default: return assertNever(config)
  }
}

function scriptBootstrapArgs(
  fs: Pick<FileSystem, 'processPathFromHostPath'>, bootstrapPath: string | undefined, maxMessageBytes: number, persistent: boolean,
): string[] {
  const moduleName = persistent ? 'persistent-process' : 'process'
  if (bootstrapPath !== undefined) return [bootstrapPath, String(maxMessageBytes)]
  const mapped = (path: string): string => {
    const result = fs.processPathFromHostPath(path)
    if (result === undefined) throw new Error(`PTC runtime bootstrap is unavailable in the subprocess execution world: ${path}`)
    return result
  }
  /* v8 ignore next 3 -- built-lib.e2e.ts executes the bundled provider and sibling process.js under plain Node. */
  if (!new URL(import.meta.url).pathname.endsWith('.ts')) {
    return [mapped(fileURLToPath(new URL(`./${moduleName}.js`, import.meta.url))), String(maxMessageBytes)]
  }
  const entry = mapped(fileURLToPath(new URL(`./${moduleName}.ts`, import.meta.url)))
  const subprocess = dirname(fileURLToPath(import.meta.resolve('@deepseek-ai/dsh-subprocess/package.json')))
  const helper = mapped(resolve(subprocess, 'src/control.ts'))
  const main = persistent ? 'runPersistentMain' : 'runNodeMain'
  const source = `const {openInheritedControlChannel}=await import(${JSON.stringify(pathToFileURL(helper).href)});const {${main}}=await import(${JSON.stringify(pathToFileURL(entry).href)});await ${main}(openInheritedControlChannel(),${maxMessageBytes},process);`
  return ['--input-type=module', '--eval', source]
}