#!/bin/bash
#
# script/stow-package <package>
#
# Wrapper around `stow --restow --no-folding` that handles pre-existing files
# in $HOME by moving them into a timestamped backup dir before stowing.
# Intended for the first-time install / migration case where $HOME already
# contains real config files or foreign symlinks (from a previous dotfile
# manager or hand-authored) that would otherwise make stow abort.
#
# Behavior:
#   1. Scans the package for target paths in $HOME that are already occupied.
#   2. Moves every conflicting real file into
#      ~/.dotfiles-backup/<timestamp>/<relative-path>/, preserving structure.
#   3. Runs the real stow.
#
# Conflicting user files are never deleted — if the new setup is wrong you can
# rsync the backup dir back over $HOME. Restowing only removes obsolete
# symlinks owned by this package. Invoked by the Makefile's stow targets and
# by script/install-darwin.

set -euo pipefail

pkg="${1:?usage: script/stow-package <package>}"

REPO_ROOT="$(cd "$(dirname "$0")/.." && pwd)"
cd "$REPO_ROOT"

if [ ! -d "$pkg" ]; then
    echo "stow-package: no such package: $pkg" >&2
    exit 1
fi

# Enumerate conflicts by inspecting the filesystem directly. With
# --no-folding every file in the package becomes its own symlink in $HOME,
# so a conflict is simply: something already occupies a target path and it
# isn't what we're about to put there. Deriving this ourselves keeps the
# script independent of stow's human-readable diagnostics, whose wording
# differs between stow 2.3.x (Debian/Ubuntu) and 2.4+ (Homebrew) and is not
# a stable interface in any case.
conflicts=$(
    find "$pkg" -mindepth 1 -print0 | while IFS= read -r -d '' src; do
        rel="${src#"$pkg"/}"
        target="$HOME/$rel"
	# Stow always ignores its package-local ignore file. Runtime paths in
	# that file are mirrored in the repository's .gitignore, so skip them
	# here too instead of moving aside host-local state Stow will not link.
	[ "$rel" = ".stow-local-ignore" ] && continue
	git check-ignore -q -- "$src" 2>/dev/null && continue
        # -e is false for a dangling symlink, so test -L too: a broken link
        # still occupies the path and still has to be moved aside.
        [ -e "$target" ] || [ -L "$target" ] || continue
        if [ -d "$src" ] && [ ! -L "$src" ]; then
	    if [ -L "$target" ]; then
		# An owned folded directory is safe: --restow combined with
		# --no-folding will replace it with real target directories.
		# A link to any other directory is a migration conflict.
		[ "$target" -ef "$src" ] || printf '%s\n' "$rel"
	    else
		# stow just needs a real directory here; anything else blocks it.
		[ -d "$target" ] || printf '%s\n' "$rel"
	    fi
        else
            # -ef compares device+inode through symlinks, so this is true
            # when the target is already the very file the package provides
            # — a re-stow, not a conflict.
            [ "$target" -ef "$src" ] || printf '%s\n' "$rel"
        fi
    done
)

if [ -n "$conflicts" ]; then
    ts=$(date +%Y%m%d-%H%M%S)
    backup_root="$HOME/.dotfiles-backup/$ts"
    echo "stow-package: $pkg has conflicts; moving aside to $backup_root"
    while IFS= read -r rel; do
        [ -n "$rel" ] || continue
        src="$HOME/$rel"
        dst="$backup_root/$rel"
        mkdir -p "$(dirname "$dst")"
        mv "$src" "$dst"
        echo "  moved $rel"
    done <<< "$conflicts"
fi

stow --restow --no-folding -t "$HOME" "$pkg"
echo "stow-package: stowed $pkg"