open Core;
module Unix = Core_unix;

module Util = Flake_env__util;
module Watches = Flake_env__watches;
module Versions = Flake_env__versions;

let print_cur_cache = (profile_rc) => {
  In_channel.read_all(profile_rc) |> Printf.printf("%s")
};

let clean_old_gcroots = (layout_dir) => {
  Util.rmrf(layout_dir ++ "/flake-inputs/");
  Util.rmrf(layout_dir);
  Unix.mkdir_p(layout_dir ++ "/flake-inputs/");
};

let add_gcroot = (store_path, symlink) => {
  switch (Util.nix(["build", "--out-link", symlink, store_path])) {
  | (Ok(), _) => Ok()
  | (err, _) => err
  }
};

let freshen_cache = (layout_dir, hash, flake_specifier, other_args) => {
    clean_old_gcroots(layout_dir);
    let tmp_profile = layout_dir ++ "flake-tmp-profile."  ++ Core.Pid.to_string(Core_unix.getpid());

    let pde_args = ["print-dev-env", "--profile", tmp_profile, flake_specifier, ...other_args];
    let (exit_code, stdout_content) = Util.nix(pde_args);

    let profile = layout_dir ++ "/flake-profile-" ++ hash;
    let profile_rc = profile ++ ".rc";

    switch (exit_code) {
    | Ok() => {
        Out_channel.with_file(~f=f=> Out_channel.output_string(f, stdout_content), profile_rc);
        switch (add_gcroot(tmp_profile, profile)) {
        | Ok() => {
            Sys_unix.remove(tmp_profile);
            let flake_input_cache_path = layout_dir ++ "/flake-inputs/"
              let flake_inputs = Watches.get_input_paths();
            flake_inputs |> List.iter(~f=(inpt) => {
                switch (add_gcroot("/nix/store/" ++ inpt, flake_input_cache_path ++ inpt)) {
                | Ok() => ()
                | err => Printf.eprintf("Failed creating flake-input gcroot: %s\n", Core_unix.Exit_or_signal.to_string_hum(err));
                };
              });
            print_cur_cache(profile_rc);
          }
        | err => {
            Printf.eprintf("Failed creating gcroot: %s\n", Core_unix.Exit_or_signal.to_string_hum(err));
            exit(1);
          }
        };
      }
    | err => {
        Printf.eprintf("Failed evaluating flake: %s\n", Core_unix.Exit_or_signal.to_string_hum(err));
        exit(1);
      }
    };
  };

let preflight = (layout_directory) => {
  switch (Versions.preflight_versions(), Sys_unix.is_directory(layout_directory)) {
  | (Ok(_), `Yes) => Ok()
  | (Ok(_), _) => {
      Unix.mkdir_p(layout_directory);
      Ok()
    }
  | (err, _) => err
  }
}