;;; lisp/cli/env.el --- envvar file generator -*- lexical-binding: t; -*-
;;; Commentary:
;;; Code:

;;
;;; Variables

(defvar doom-env-file (doom-path doom-profile-data-dir "env")
  "The location of your envvar file, generated by `doom env`.

This file contains environment variables scraped from your shell environment,
which is loaded at startup (if it exists). This is helpful if Emacs can't
\(easily) be launched from the correct shell session (particularly for MacOS
users).")

(defvar doom-env-deny
  '(;; Unix/shell state that shouldn't be persisted
    "^HOME$" "^\\(OLD\\)?PWD$" "^SHLVL$" "^PS1$" "^R?PROMPT$" "^TERM\\(CAP\\)?$"
    "^USER$" "^GIT_CONFIG" "^INSIDE_EMACS$"
    ;; X server or services' variables that shouldn't be persisted
    "^DISPLAY$" "^DBUS_SESSION_BUS_ADDRESS$" "^XAUTHORITY$" "^XDG_SESSION_TYPE$"
    ;; Windows+WSL envvars that shouldn't be persisted
    "^WSL_INTEROP$"
    ;; ssh and gpg variables (likely to become stale)
    "^SSH_\\(AUTH_SOCK\\|AGENT_PID\\)$" "^\\(SSH\\|GPG\\)_TTY$"
    "^GPG_AGENT_INFO$"
    ;; Internal Doom envvars
    "^DEBUG$" "^INSECURE$" "^\\(EMACS\\|DOOM\\)DIR$" "^__")
  "Environment variables to omit from envvar files.

Each string is a regexp, matched against variable names to omit from
`doom-env-file'.")

(defvar doom-env-allow '()
  "Environment variables to include in envvar files.

This overrules `doom-env-deny'. Each string is a regexp, matched against
variable names to omit from `doom-env-file'.")


;;
;;; Commands

(defcli! env
    ((allow-only  ("--allow-all"))
     (deny-only   ("--deny-all"))
     (output-file ("-o" path) "Write envvar file to non-standard PATH.")
     ;; TODO (refresh?    ("-r" "--refresh"))
     &multiple
     (rules ("-a" "--allow" "-d" "--deny" regexp) "Allow/deny envvars that match REGEXP"))
  "(Re)generates envvars file from your shell environment.

The envvars file is created by scraping the current shell environment into
newline-delimited KEY=VALUE pairs. Typically by running '$SHELL -ic env' (or
'$SHELL -c set' on windows). Doom loads this file at startup (if it exists) to
ensure Emacs mirrors your shell environment (particularly to ensure PATH and
SHELL are correctly set).

This is useful in cases where you cannot guarantee that Emacs (or the daemon)
will be launched from the correct environment (e.g. on MacOS or through certain
app launchers on Linux).

This file is automatically regenerated when you run this command or 'doom sync'.
However, 'doom sync' will only regenerate this file if it exists.

Why this over exec-path-from-shell?

  1. `exec-path-from-shell' spawns (at least) one process at startup to scrape
     your shell environment. This can be arbitrarily slow depending on the
     user's shell configuration. A single program (like pyenv or nvm) or config
     framework (like oh-my-zsh) could undo all of Doom's startup optimizations
     in one fell swoop.

  2. `exec-path-from-shell' only scrapes some state from your shell. You have to
     be proactive in order to get it to capture all the envvars relevant to your
     development environment.

     I'd rather it inherit your shell environment /correctly/ (and /completely/)
     or not at all. It frontloads the debugging process rather than hiding it
     until you least want to deal with it."
  (let ((env-file (doom-path (or output-file doom-env-file))))
    (with-temp-file env-file
      (setq-local coding-system-for-write 'utf-8-unix)
      (print! (start "%s envvars file")
              (if (file-exists-p env-file)
                  "Regenerating"
                "Generating"))
      (print-group!
       (goto-char (point-min))
       (insert
        ";; -*- mode: lisp-interaction; coding: utf-8-unix; -*-\n"
        ";; ---------------------------------------------------------------------------\n"
        ";; This file was auto-generated by `doom env'. It contains a list of environment\n"
        ";; variables scraped from your default shell (based on your settings for \n"
        ";; `doom-env-allow' and `doom-env-deny').\n"
        ";;\n"
        (if (file-equal-p env-file doom-env-file)
            (concat ";; It is NOT safe to edit this file. Changes will be overwritten next time you\n"
                    ";; run 'doom sync'. To create a safe-to-edit envvar file use:\n;;\n"
                    ";;   doom env -o ~/.doom.d/myenv\n;;\n"
                    ";; And load it with (doom-load-envvars-file \"~/.doom.d/myenv\").\n")
          (concat ";; This file is safe to edit by hand, but needs to be loaded manually with:\n;;\n"
                  ";;   (doom-load-envvars-file \"path/to/this/file\")\n;;\n"
                  ";; Use 'doom env -o path/to/this/file' to regenerate it."))
        "\n")
       ;; We assume that this noninteractive session was spawned from the user's
       ;; interactive shell, so simply dump `process-environment' to a file.
       ;;
       ;; This should be well-formatted, in case humans want to hand-modify it.
       (let* ((denylist  (remq nil (append (if deny-only  '(".")) (list allow-only) doom-env-deny)))
              (allowlist (remq nil (append (if allow-only '(".")) (list deny-only) doom-env-allow))))
         (dolist (rule rules)
           (push (cdr rule) (if (member (car rule) '("-a" "--allow"))
                                allowlist
                              denylist)))
         (insert "(")
         (dolist (env (get 'process-environment 'initial-value))
           (catch 'skip
             (let* ((var  (car (split-string env "=")))
                    (pred (doom-rpartial #'string-match-p var)))
               (when (seq-find pred denylist)
                 (if (seq-find pred allowlist)
                     (doom-log "Whitelisted %s" var)
                   (doom-log "Ignored %s" var)
                   (throw 'skip t)))
               (insert (prin1-to-string env) "\n "))))
         (insert ")"))
       (print! (success "Generated %s") (path env-file))
       t))))

(defcli! (env (clear c)) ()
  "Deletes the default envvar file."
  (let ((env-file (abbreviate-file-name doom-env-file)))
    (unless (file-exists-p env-file)
      (user-error "No envvar file to delete: %s" env-file))
    (delete-file env-file)
    (print! (success "Deleted %s") (path env-file))))

(provide 'doom-cli-env)
;;; env.el ends here