import { existsSync, realpathSync } from 'fs'
import { resolveFrom } from './resolve-from'
import { dirname, join, relative } from 'path'

export interface MissingDependency {
  file: string
  /**
   * The package's package.json (e.g. require(`${pkg}/package.json`)) MUST resolve.
   * If `exportsRestrict` is false, `${file}` MUST also resolve.
   */
  pkg: string
  /**
   * If true, the pkg's package.json needs to be resolvable.
   * If true, will resolve `file` relative to the real path of the package.json.
   *
   * For example, `{ file: '@types/react/index.d.ts', pkg: '@types/react', exportsRestrict: true }`
   * will try to resolve '@types/react/package.json' first and then assume `@types/react/index.d.ts`
   * resolves to `path.join(dirname(resolvedPackageJsonPath), 'index.d.ts')`.
   *
   * If false, will resolve `file` relative to the baseDir.
   * ForFor example, `{ file: '@types/react/index.d.ts', pkg: '@types/react', exportsRestrict: true }`
   * will try to resolve `@types/react/index.d.ts` directly.
   */
  exportsRestrict: boolean
}

export type NecessaryDependencies = {
  resolved: Map<string, string>
  missing: MissingDependency[]
}

export function hasNecessaryDependencies(
  baseDir: string,
  requiredPackages: MissingDependency[]
): NecessaryDependencies {
  let resolutions = new Map<string, string>()
  const missingPackages: MissingDependency[] = []

  for (const p of requiredPackages) {
    try {
      const pkgPath = realpathSync(
        resolveFrom(baseDir, `${p.pkg}/package.json`)
      )
      const pkgDir = dirname(pkgPath)

      resolutions.set(join(p.pkg, 'package.json'), pkgPath)

      if (p.exportsRestrict) {
        const fileNameToVerify = relative(p.pkg, p.file)
        if (fileNameToVerify) {
          const fileToVerify = join(pkgDir, fileNameToVerify)
          if (existsSync(fileToVerify)) {
            resolutions.set(p.pkg, fileToVerify)
          } else {
            missingPackages.push(p)
            continue
          }
        } else {
          resolutions.set(p.pkg, pkgPath)
        }
      } else {
        resolutions.set(p.pkg, resolveFrom(baseDir, p.file))
      }
    } catch (_) {
      missingPackages.push(p)
      continue
    }
  }

  return {
    resolved: resolutions,
    missing: missingPackages,
  }
}