use itertools::Itertools;

use super::common::CodeNotFound;
use super::VirtFS;
use crate::intern::Token;
use crate::name::{PathSlice, VPath};
use crate::proj_error::ErrorSansOrigin;

/// Modify the prefix of a nested file tree
pub struct PrefixFS<'a> {
  remove: VPath,
  add: VPath,
  wrapped: Box<dyn VirtFS + 'a>,
}
impl<'a> PrefixFS<'a> {
  /// Modify the prefix of a file tree
  pub fn new(wrapped: impl VirtFS + 'a, remove: impl AsRef<str>, add: impl AsRef<str>) -> Self {
    Self {
      wrapped: Box::new(wrapped),
      remove: VPath::parse(remove.as_ref()),
      add: VPath::parse(add.as_ref()),
    }
  }
  fn proc_path(&self, path: &[Tok<String>]) -> Option<Vec<Tok<String>>> {
    let path = path.strip_prefix(self.remove.as_slice())?;
    Some(self.add.0.iter().chain(path).cloned().collect_vec())
  }
}
impl<'a> VirtFS for PrefixFS<'a> {
  fn get(&self, path: &[Tok<String>], full_path: &PathSlice) -> super::FSResult {
    let path =
      self.proc_path(path).ok_or_else(|| CodeNotFound::new(full_path.to_vpath()).pack())?;
    self.wrapped.get(&path, full_path)
  }
  fn display(&self, path: &[Tok<String>]) -> Option<String> {
    self.wrapped.display(&self.proc_path(path)?)
  }
}