import * as childProcess from 'child_process'
import * as path from 'path'
import {promisify} from 'util'
import * as ioUtil from './io-util'

const exec = promisify(childProcess.exec)

/**
 * Interface for cp/mv options
 */
export interface CopyOptions {
  /** Optional. Whether to recursively copy all subdirectories. Defaults to false */
  recursive?: boolean
  /** Optional. Whether to overwrite existing files in the destination. Defaults to true */
  force?: boolean
}

/**
 * Interface for cp/mv options
 */
export interface MoveOptions {
  /** Optional. Whether to overwrite existing files in the destination. Defaults to true */
  force?: boolean
}

/**
 * Copies a file or folder.
 * Based off of shelljs - https://github.com/shelljs/shelljs/blob/9237f66c52e5daa40458f94f9565e18e8132f5a6/src/cp.js
 *
 * @param     source    source path
 * @param     dest      destination path
 * @param     options   optional. See CopyOptions.
 */
export async function cp(
  source: string,
  dest: string,
  options: CopyOptions = {}
): Promise<void> {
  const {force, recursive} = readCopyOptions(options)

  const destStat = (await ioUtil.exists(dest)) ? await ioUtil.stat(dest) : null
  // Dest is an existing file, but not forcing
  if (destStat && destStat.isFile() && !force) {
    return
  }

  // If dest is an existing directory, should copy inside.
  const newDest: string =
    destStat && destStat.isDirectory()
      ? path.join(dest, path.basename(source))
      : dest

  if (!(await ioUtil.exists(source))) {
    throw new Error(`no such file or directory: ${source}`)
  }
  const sourceStat = await ioUtil.stat(source)

  if (sourceStat.isDirectory()) {
    if (!recursive) {
      throw new Error(
        `Failed to copy. ${source} is a directory, but tried to copy without recursive flag.`
      )
    } else {
      await cpDirRecursive(source, newDest, 0, force)
    }
  } else {
    if (path.relative(source, newDest) === '') {
      // a file cannot be copied to itself
      throw new Error(`'${newDest}' and '${source}' are the same file`)
    }

    await copyFile(source, newDest, force)
  }
}

/**
 * Moves a path.
 *
 * @param     source    source path
 * @param     dest      destination path
 * @param     options   optional. See MoveOptions.
 */
export async function mv(
  source: string,
  dest: string,
  options: MoveOptions = {}
): Promise<void> {
  if (await ioUtil.exists(dest)) {
    let destExists = true
    if (await ioUtil.isDirectory(dest)) {
      // If dest is directory copy src into dest
      dest = path.join(dest, path.basename(source))
      destExists = await ioUtil.exists(dest)
    }

    if (destExists) {
      if (options.force == null || options.force) {
        await rmRF(dest)
      } else {
        throw new Error('Destination already exists')
      }
    }
  }
  await mkdirP(path.dirname(dest))
  await ioUtil.rename(source, dest)
}

/**
 * Remove a path recursively with force
 *
 * @param inputPath path to remove
 */
export async function rmRF(inputPath: string): Promise<void> {
  if (ioUtil.IS_WINDOWS) {
    // Node doesn't provide a delete operation, only an unlink function. This means that if the file is being used by another
    // program (e.g. antivirus), it won't be deleted. To address this, we shell out the work to rd/del.
    try {
      if (await ioUtil.isDirectory(inputPath, true)) {
        await exec(`rd /s /q "${inputPath}"`)
      } else {
        await exec(`del /f /a "${inputPath}"`)
      }
    } catch (err) {
      // if you try to delete a file that doesn't exist, desired result is achieved
      // other errors are valid
      if (err.code !== 'ENOENT') throw err
    }

    // Shelling out fails to remove a symlink folder with missing source, this unlink catches that
    try {
      await ioUtil.unlink(inputPath)
    } catch (err) {
      // if you try to delete a file that doesn't exist, desired result is achieved
      // other errors are valid
      if (err.code !== 'ENOENT') throw err
    }
  } else {
    let isDir = false
    try {
      isDir = await ioUtil.isDirectory(inputPath)
    } catch (err) {
      // if you try to delete a file that doesn't exist, desired result is achieved
      // other errors are valid
      if (err.code !== 'ENOENT') throw err
      return
    }

    if (isDir) {
      await exec(`rm -rf "${inputPath}"`)
    } else {
      await ioUtil.unlink(inputPath)
    }
  }
}

/**
 * Make a directory.  Creates the full path with folders in between
 * Will throw if it fails
 *
 * @param   fsPath        path to create
 * @returns Promise<void>
 */
export async function mkdirP(fsPath: string): Promise<void> {
  await ioUtil.mkdirP(fsPath)
}

/**
 * Returns path of a tool had the tool actually been invoked.  Resolves via paths.
 * If you check and the tool does not exist, it will throw.
 *
 * @param     tool              name of the tool
 * @param     check             whether to check if tool exists
 * @returns   Promise<string>   path to tool
 */
export async function which(tool: string, check?: boolean): Promise<string> {
  if (!tool) {
    throw new Error("parameter 'tool' is required")
  }

  // recursive when check=true
  if (check) {
    const result: string = await which(tool, false)

    if (!result) {
      if (ioUtil.IS_WINDOWS) {
        throw new Error(
          `Unable to locate executable file: ${tool}. Please verify either the file path exists or the file can be found within a directory specified by the PATH environment variable. Also verify the file has a valid extension for an executable file.`
        )
      } else {
        throw new Error(
          `Unable to locate executable file: ${tool}. Please verify either the file path exists or the file can be found within a directory specified by the PATH environment variable. Also check the file mode to verify the file is executable.`
        )
      }
    }
  }

  try {
    // build the list of extensions to try
    const extensions: string[] = []
    if (ioUtil.IS_WINDOWS && process.env.PATHEXT) {
      for (const extension of process.env.PATHEXT.split(path.delimiter)) {
        if (extension) {
          extensions.push(extension)
        }
      }
    }

    // if it's rooted, return it if exists. otherwise return empty.
    if (ioUtil.isRooted(tool)) {
      const filePath: string = await ioUtil.tryGetExecutablePath(
        tool,
        extensions
      )

      if (filePath) {
        return filePath
      }

      return ''
    }

    // if any path separators, return empty
    if (tool.includes('/') || (ioUtil.IS_WINDOWS && tool.includes('\\'))) {
      return ''
    }

    // build the list of directories
    //
    // Note, technically "where" checks the current directory on Windows. From a toolkit perspective,
    // it feels like we should not do this. Checking the current directory seems like more of a use
    // case of a shell, and the which() function exposed by the toolkit should strive for consistency
    // across platforms.
    const directories: string[] = []

    if (process.env.PATH) {
      for (const p of process.env.PATH.split(path.delimiter)) {
        if (p) {
          directories.push(p)
        }
      }
    }

    // return the first match
    for (const directory of directories) {
      const filePath = await ioUtil.tryGetExecutablePath(
        directory + path.sep + tool,
        extensions
      )
      if (filePath) {
        return filePath
      }
    }

    return ''
  } catch (err) {
    throw new Error(`which failed with message ${err.message}`)
  }
}

function readCopyOptions(options: CopyOptions): Required<CopyOptions> {
  const force = options.force == null ? true : options.force
  const recursive = Boolean(options.recursive)
  return {force, recursive}
}

async function cpDirRecursive(
  sourceDir: string,
  destDir: string,
  currentDepth: number,
  force: boolean
): Promise<void> {
  // Ensure there is not a run away recursive copy
  if (currentDepth >= 255) return
  currentDepth++

  await mkdirP(destDir)

  const files: string[] = await ioUtil.readdir(sourceDir)

  for (const fileName of files) {
    const srcFile = `${sourceDir}/${fileName}`
    const destFile = `${destDir}/${fileName}`
    const srcFileStat = await ioUtil.lstat(srcFile)

    if (srcFileStat.isDirectory()) {
      // Recurse
      await cpDirRecursive(srcFile, destFile, currentDepth, force)
    } else {
      await copyFile(srcFile, destFile, force)
    }
  }

  // Change the mode for the newly created directory
  await ioUtil.chmod(destDir, (await ioUtil.stat(sourceDir)).mode)
}

// Buffered file copy
async function copyFile(
  srcFile: string,
  destFile: string,
  force: boolean
): Promise<void> {
  if ((await ioUtil.lstat(srcFile)).isSymbolicLink()) {
    // unlink/re-link it
    try {
      await ioUtil.lstat(destFile)
      await ioUtil.unlink(destFile)
    } catch (e) {
      // Try to override file permission
      if (e.code === 'EPERM') {
        await ioUtil.chmod(destFile, '0666')
        await ioUtil.unlink(destFile)
      }
      // other errors = it doesn't exist, no work to do
    }

    // Copy over symlink
    const symlinkFull: string = await ioUtil.readlink(srcFile)
    await ioUtil.symlink(
      symlinkFull,
      destFile,
      ioUtil.IS_WINDOWS ? 'junction' : null
    )
  } else if (!(await ioUtil.exists(destFile)) || force) {
    await ioUtil.copyFile(srcFile, destFile)
  }
}