import filepath
import ftpasta/ftp_error.{type FTPError, DirParseError, LocalFileError}
import ftpasta/internal
import ftpasta/tls_config.{type TLSConfig}
import gleam/erlang/process.{type Pid}
import gleam/int
import gleam/list
import gleam/option
import gleam/regex
import gleam/result
import gleam/string
import simplifile

/// Type representing an FTP connection.
pub opaque type Connection {
  Connection(pid: Pid)
}

/// Remote file type.
pub type Listing {
  Directory(name: String)
  File(name: String, size: Int)
  Link(name: String, target: String)
}

// Misc functions:

/// Convert an FTPError into a descriptive string.
pub fn describe_error(error) {
  case error {
    DirParseError -> "Parsing directory contents failed."
    LocalFileError(e) -> "Local file error: " <> simplifile.describe_error(e)
    _ -> internal.formaterror(error)
  }
}

// FTP configuration:

/// Configuration struct for building FTP connections.
pub type Config {
  Config(
    host: String,
    port: Int,
    tls: TLSConfig,
    username: String,
    password: String,
  )
}

/// Start building an FTP connection.
pub fn new(host) {
  Config(
    host: host,
    port: 21,
    tls: tls_config.Plaintext,
    username: "anonymous",
    password: "",
  )
}

/// Connect to the server.
pub fn connect(config: Config) -> Result(Connection, FTPError) {
  use pid <- result.try(internal.open(config.host, config.port, config.tls))
  use _ <- result.map(internal.user(pid, config.username, config.password))
  Connection(pid)
}

/// Provide a username and password.
pub fn auth(config: Config, username, password) {
  Config(..config, username:, password:)
}

/// Use a non-default port.
pub fn port(config: Config, port) {
  Config(..config, port:)
}

/// Use encryption.
pub fn encryption(config: Config, tls: TLSConfig) {
  Config(..config, tls:)
}

// FTP operations

/// Append some data onto a file on the server.
pub fn append_bytes(connection: Connection, data, remote_file) {
  internal.append_bin(connection.pid, data, remote_file)
}

/// Append a file to another file on the server.
pub fn append_file(connection: Connection, local_file, remote_file) {
  use _ <- result.try(reset_local_dir(connection))
  internal.append(connection.pid, local_file, remote_file)
}

/// Change directories on the remote server.
pub fn change_working_dir(connection: Connection, remote_dir) {
  internal.cd(connection.pid, remote_dir)
}

/// Close the connection.
pub fn close(connection: Connection) {
  internal.close(connection.pid)
}

/// Create a new directory on the server.
pub fn create_dir(connection: Connection, remote_dir) {
  internal.mkdir(connection.pid, remote_dir)
}

/// Remove an empty directory from the server.
pub fn delete_dir(connection: Connection, remote_dir) {
  internal.rmdir(connection.pid, remote_dir)
}

/// Remove a file from the server.
pub fn delete_file(connection: Connection, remote_file) {
  internal.delete(connection.pid, remote_file)
}

/// Remove a directory and all contents from the server.
pub fn delete_recursive(connection: Connection, remote_dir) {
  use current_dir <- result.try(get_working_dir(connection))
  use _ <- result.try(change_working_dir(connection, remote_dir))
  use items <- result.try(list(connection, ""))
  use _ <- result.try(
    list.try_map(items, fn(item) {
      case item {
        File(name, ..) | Link(name, ..) -> delete_file(connection, name)
        Directory(name) -> delete_recursive(connection, name)
      }
    }),
  )
  use _ <- result.try(change_working_dir(connection, current_dir))
  delete_dir(connection, remote_dir)
}

/// Fetch a file from the server, and return it as a BitArray.
pub fn download_bytes(connection: Connection, remote_file) {
  internal.recv_bin(connection.pid, remote_file)
}

/// Fetch a file from the server.
pub fn download_file(connection: Connection, remote_file, local_file) {
  use _ <- result.try(reset_local_dir(connection))
  internal.recv(connection.pid, remote_file, local_file)
}

/// Fetch a directory and all contents recursively from the server.
pub fn download_recursive(connection: Connection, remote_dir, local_dir) {
  use _ <- result.try(
    simplifile.create_directory(local_dir)
    |> result.map_error(LocalFileError),
  )
  use items <- result.try(list(connection, remote_dir))
  list.try_map(items, fn(item) {
    let local_path = filepath.join(local_dir, item.name)
    let remote_path = remote_dir <> "/" <> item.name
    case item {
      File(..) | Link(..) -> download_file(connection, remote_path, local_path)
      Directory(..) -> download_recursive(connection, remote_path, local_path)
    }
  })
  |> result.replace(Nil)
}

/// Get the current remote path used for the connection.
pub fn get_working_dir(connection: Connection) {
  internal.pwd(connection.pid)
}

/// List all files, symlinks, and subdirectories in a directory.
pub fn list(
  connection: Connection,
  remote_dir,
) -> Result(List(Listing), FTPError) {
  let assert Ok(re) = regex.from_string("[\\r\\n]+")
  let arg = case remote_dir {
    "" -> "-Al"
    dir -> "-Al " <> dir
  }
  use text <- result.try(internal.ls(connection.pid, arg))
  regex.split(re, text)
  |> list.filter(fn(s) { !string.is_empty(s) })
  |> list.try_map(parse_ls_line)
}

/// Rename a file or directory on the server.
pub fn rename(connection: Connection, old_path, new_path) {
  internal.rename(connection.pid, old_path, new_path)
}

/// Send a data in memory to the server.
pub fn upload_bytes(connection: Connection, data, remote_file) {
  internal.send_bin(connection.pid, data, remote_file)
}

/// Send a file to the server.
pub fn upload_file(connection: Connection, local_file, remote_file) {
  use _ <- result.try(reset_local_dir(connection))
  internal.send(connection.pid, local_file, remote_file)
}

/// Send a directory and all contents to the server.
pub fn upload_recursive(connection: Connection, local_dir, remote_dir) {
  use _ <- result.try(create_dir(connection, remote_dir))
  use items <- result.try(
    simplifile.read_directory(local_dir)
    |> result.map_error(LocalFileError),
  )
  list.try_map(items, fn(name) {
    let local_path = filepath.join(local_dir, name)
    let remote_path = remote_dir <> "/" <> name
    case simplifile.is_file(local_path) {
      Ok(True) -> upload_file(connection, local_path, remote_path)
      Ok(False) -> upload_recursive(connection, local_path, remote_path)
      Error(e) -> Error(LocalFileError(e))
    }
  })
  |> result.replace(Nil)
}

// Other functions

/// Parse a line from the output of "ls".
/// This is obviously gross, but FTP lacks better options without extensions.
fn parse_ls_line(text) -> Result(Listing, FTPError) {
  let assert Ok(whitespace) = regex.from_string(" +")
  let assert Ok(filename) = regex.from_string("(?:\\S+ +){8}(.+)")

  use name <- result.try(case regex.scan(filename, text) {
    [regex.Match(submatches: [option.Some(x)], ..)] -> Ok(x)
    _ -> Error(DirParseError)
  })

  case regex.split(whitespace, text) {
    ["d" <> _, ..] -> {
      Ok(Directory(name:))
    }
    ["-" <> _, _, _, _, size_text, ..] -> {
      case int.parse(size_text) {
        Ok(size) -> Ok(File(name:, size:))
        Error(_) -> Error(DirParseError)
      }
    }
    ["l" <> _, ..] -> {
      // This fails on links with " -> " in their name.
      case string.split_once(name, " -> ") {
        Ok(#(name, target)) -> Ok(Link(name:, target:))
        Error(_) -> Error(DirParseError)
      }
    }
    _ -> Error(DirParseError)
  }
}

/// Update the local path stored in the FTP library.
fn reset_local_dir(connection: Connection) {
  case simplifile.current_directory() {
    Ok(path) -> internal.lcd(connection.pid, path)
    Error(e) -> Error(LocalFileError(e))
  }
}