import { promises as fsp, existsSync } from 'fs'
import { fileURLToPath } from 'url'
import { basename, dirname, resolve, join, normalize, isAbsolute } from 'pathe'
import { globby } from 'globby'
import { useNuxt } from './context'
import { tryResolveModule } from '.'

export interface ResolvePathOptions {
  /** Base for resolving paths from. Default is Nuxt rootDir. */
  cwd?: string

  /** An object of aliases. Default is Nuxt configured aliases. */
  alias?: Record<string, string>

  /** The file extensions to try. Default is Nuxt configured extensions. */
  extensions?: string[]
}

/**
 * Resolve full path to a file or directory respecting Nuxt alias and extensions options
 *
 * If path could not be resolved, normalized input path will be returned
 */
export async function resolvePath (path: string, opts: ResolvePathOptions = {}): Promise<string> {
  // Always normalize input
  const _path = path
  path = normalize(path)

  // Fast return if the path exists
  if (isAbsolute(path) && existsSync(path)) {
    return path
  }

  // Use current nuxt options
  const nuxt = useNuxt()
  const cwd = opts.cwd || (nuxt ? nuxt.options.rootDir : process.cwd())
  const extensions = opts.extensions || (nuxt ? nuxt.options.extensions : ['.ts', '.mjs', '.cjs', '.json'])
  const modulesDir = nuxt ? nuxt.options.modulesDir : []

  // Resolve aliases
  path = resolveAlias(path)

  // Resolve relative to cwd
  if (!isAbsolute(path)) {
    path = resolve(cwd, path)
  }

  // Check if resolvedPath is a file
  let isDirectory = false
  if (existsSync(path)) {
    isDirectory = (await fsp.lstat(path)).isDirectory()
    if (!isDirectory) {
      return path
    }
  }

  // Check possible extensions
  for (const ext of extensions) {
    // path.[ext]
    const pathWithExt = path + ext
    if (!isDirectory && existsSync(pathWithExt)) {
      return pathWithExt
    }
    // path/index.[ext]
    const pathWithIndex = join(path, 'index' + ext)
    if (isDirectory && existsSync(pathWithIndex)) {
      return pathWithIndex
    }
  }

  // Try to resolve as module id
  const resolveModulePath = tryResolveModule(_path, { paths: [cwd, ...modulesDir] })
  if (resolveModulePath) {
    return resolveModulePath
  }

  // Return normalized input
  return path
}

/**
 * Try to resolve first existing file in paths
 */
export async function findPath (paths: string[], opts?: ResolvePathOptions): Promise<string|null> {
  for (const path of paths) {
    const rPath = await resolvePath(path, opts)
    if (await existsSensitive(rPath)) {
      return rPath
    }
  }
  return null
}

/**
 * Resolve path aliases respecting Nuxt alias options
 */
export function resolveAlias (path: string, alias?: Record<string, string>): string {
  if (!alias) {
    alias = useNuxt()?.options.alias || {}
  }
  for (const key in alias) {
    if (key === '@' && !path.startsWith('@/')) { continue } // Don't resolve @foo/bar
    if (path.startsWith(key)) {
      path = alias[key] + path.slice(key.length)
    }
  }
  return path
}

export interface Resolver {
  resolve(...path): string
  resolvePath(path: string, opts?: ResolvePathOptions): Promise<string>
}

/**
 * Create a relative resolver
 */
export function createResolver (base: string | URL): Resolver {
  if (!base) {
    throw new Error('`base` argument is missing for createResolver(base)!')
  }

  base = base.toString()
  if (base.startsWith('file://')) {
    base = dirname(fileURLToPath(base))
  }

  return {
    resolve: (...path) => resolve(base as string, ...path),
    resolvePath: (path, opts) => resolvePath(path, { cwd: base as string, ...opts })
  }
}

// --- Internal ---

async function existsSensitive (path: string) {
  if (!existsSync(path)) { return false }
  const dirFiles = await fsp.readdir(dirname(path))
  return dirFiles.includes(basename(path))
}

export async function resolveFiles (path: string, pattern: string | string[]) {
  const files = await globby(pattern, { cwd: path, followSymbolicLinks: true })
  return files.map(p => resolve(path, p))
}