;;; fzfa-tramp.el --- TRAMP-aware spawning for `fzfa' -*- lexical-binding: t; -*-

;; Copyright (C) 2026 James Nguyen

;; Author: James Nguyen <james@jojojames.com>

;; Version: 1.0

;; Package-Requires: ((emacs "29.1"))

;; Homepage: https://github.com/jojojames/fzfa

;; Assisted-by: Claude:claude-opus-4-7

;; SPDX-License-Identifier: GPL-3.0-or-later

;;; Commentary:

;; TRAMP support for fzfa.

;;

;; Makes fzfa's shell sources spawn transparently against TRAMP `ssh'

;; paths: for a TRAMP `ssh'-method `default-directory' the shell

;; command is wrapped as `ssh HOST 'cd LOCALNAME && CMD'' and

;; fzf-native is handed a safe local chdir target. The C-layer's

;; fork+pipe+parallel-score pipeline is unchanged; the remote binary

;; streams over ssh into the same pipe reader as a local process.

;;

;; When `tramp-use-connection-share' is non-nil (Emacs 30 default on

;; non-Windows), TRAMP has already opened a ControlMaster socket for

;; the host, so the wrapped ssh call piggybacks on that socket with

;; no handshake. With sharing off, each fzfa invocation pays one

;; handshake — acceptable for interactive use.

;;

;; Commands:

;; `fzfa-ssh' Pick a host from ~/.ssh/config and visit /ssh:HOST:.

;; `fzfa-tramp' Pick a host from ~/.ssh/config and open the browse

;; picker on it (via `fzfa-browse-files').

;;; Code:

(require 'cl-lib)

(require 'fzfa)

(declare-function tramp-dissect-file-name "tramp" (name &optional nodefault))

;; `cl-defstruct' slot accessors — check-declare can't see auto-generated

;; bodies, only literal `defun's. ARGLIST is `t' (unspecified) not `nil'

;; (which would mean "takes 0 args" and trip byte-compile on 1-arg sites).

(declare-function tramp-file-name-method "tramp" t t)

(declare-function tramp-file-name-user "tramp" t t)

(declare-function tramp-file-name-host "tramp" t t)

(declare-function tramp-file-name-port "tramp" t t)

(declare-function tramp-file-name-localname "tramp" t t)

(declare-function fzfa-browse-files "fzfa-emacs" (&optional dir))

(defcustom fzfa-tramp-safe-local-dir "/"

"Local directory handed to `fzf-native-async-start' for ssh-wrapped calls.

The C layer's `chdir' runs before the wrapped `ssh HOST cmd', so the

choice is irrelevant to the actual working directory of the remote

command (that's set inside the ssh payload). It only needs to be a

`chdir'-able local path."

:type 'directory

:group 'fzfa)

(defun fzfa-tramp--build-ssh-cmd (vec cmd)

"Build `ssh USER@HOST -p PORT \\='cd LOCALNAME && CMD\\='' for VEC.

VEC is a `tramp-file-name' struct. Returns a shell string suitable

for `fzf-native-async-start' (which execs it via /bin/sh -c)."

(let* ((user (tramp-file-name-user vec))

(host (tramp-file-name-host vec))

(port (tramp-file-name-port vec))

(localname (tramp-file-name-localname vec))

(target (if user (format "%s@%s" user host) host))

(port-args (if port (format " -p %s" port) ""))

(remote-cmd (format "cd %s && %s"

(shell-quote-argument localname)

cmd)))

(format "ssh%s %s %s"

port-args

(shell-quote-argument target)

(shell-quote-argument remote-cmd))))

(defun fzfa-tramp--transform (cmd dir)

"Spawn transform for `fzfa-source-spawn-transform-function'.

For TRAMP `ssh'-method paths, wraps CMD as

`ssh HOST \\='cd LOCALNAME && CMD\\='' and returns

`fzfa-tramp-safe-local-dir' as the chdir target. Non-`ssh' TRAMP

methods and local paths pass through unchanged."

(if (not (file-remote-p dir))

(cons cmd dir)

(require 'tramp)

(let ((vec (tramp-dissect-file-name dir)))

(if (equal (tramp-file-name-method vec) "ssh")

(cons (fzfa-tramp--build-ssh-cmd vec cmd)

fzfa-tramp-safe-local-dir)

(cons cmd dir)))))

(defun fzfa-tramp--ssh-hosts ()

"Return the list of non-wildcard `Host' entries from ~/.ssh/config."

(let ((config (expand-file-name "~/.ssh/config"))

hosts)

(when (file-readable-p config)

(with-temp-buffer

(insert-file-contents config)

(while (re-search-forward

"^[Hh]ost[[:space:]]+\\(.+\\)" nil t)

(dolist (host (split-string (match-string 1)))

(unless (string-match-p "[*?!]" host)

(push host hosts))))))

(nreverse hosts)))

(defun fzfa-tramp--pick-host ()

"Pick an SSH host from ~/.ssh/config; return the TRAMP root `/ssh:HOST:'.

Signals `user-error' when the config is missing or has no hosts."

(when-let* ((hosts (or (fzfa-tramp--ssh-hosts)

(user-error "No SSH hosts in ~/.ssh/config")))

(host (fzfa-completing-read

:candidates hosts :prompt "ssh: ")))

(concat "/ssh:" host ":")))

;;;###autoload

(defun fzfa-ssh ()

"Pick a host from ~/.ssh/config and visit `/ssh:HOST:' as a directory."

(interactive)

(when-let* ((path (fzfa-tramp--pick-host)))

(fzfa-visit-file path)))

;;;###autoload

(defun fzfa-tramp ()

"Pick a host from ~/.ssh/config and open `fzfa-browse-files' rooted there."

(interactive)

(when-let* ((path (fzfa-tramp--pick-host)))

(fzfa-browse-files path)))

;;;###autoload

(defun fzfa-tramp-setup ()

"Install fzfa's TRAMP-aware source spawn transform."

(setq fzfa-source-spawn-transform-function #'fzfa-tramp--transform))

(provide 'fzfa-tramp)

;; Local Variables:

;; package-lint-main-file: "fzfa.el"

;; End:

;;; fzfa-tramp.el ends here