#!/usr/bin/env bash
# dotsync — sync dotfiles with the least churn.
#
# Deployed configs are symlinks into this repo, so `git pull` makes edits LIVE instantly
# with no re-stow — meaning no symlink churn and no app reloads (kitty etc. keep their
# runtime state). Re-stowing (install.sh) is only needed when files are ADDED / REMOVED,
# to create or prune symlinks. dotsync does the minimum: pull, and re-link ONLY if the
# pull added/removed/renamed files.
#
#   dotsync            pull, then relink only if the file set changed
#   dotsync -n         preview incoming changes (fetch only; no pull, no relink)
#   dotsync <host>     as above, forcing the host package (normally unnecessary: install.sh
#                      reuses the host recorded in ~/.config/dots-host)
set -uo pipefail
DOTS="$(cd "$(dirname "$(readlink -f "${BASH_SOURCE[0]}")")/.." && pwd)"
cd "$DOTS" || exit 1

if [ "${1:-}" = "-n" ] || [ "${1:-}" = "--dry-run" ]; then
  git fetch -q 2>/dev/null || {
    echo "fetch failed (offline?)"
    exit 1
  }
  up="$(git rev-parse --abbrev-ref '@{u}' 2>/dev/null)" || {
    echo "no upstream set"
    exit 1
  }
  # rev-list, not diff: a plain diff also fires when the LOCAL side is ahead, mislabelling
  # your own unpushed commits as incoming. Count commits that exist only on the upstream.
  n="$(git rev-list --count "HEAD..$up")"
  if [ "$n" -eq 0 ]; then echo "already up to date with $up."; else
    echo "incoming from $up ($n commit(s)):"
    git --no-pager diff --stat "HEAD...$up"
  fi
  exit 0
fi

before="$(git rev-parse HEAD)"
if ! git pull --ff-only; then
  echo "pull not fast-forward (local commits or conflicts) — commit/stash, then retry." >&2
  exit 1
fi
after="$(git rev-parse HEAD)"

if [ "$before" = "$after" ]; then
  echo "already up to date — nothing to sync."
  exit 0
fi

# Services that read config ONCE at startup don't pick up pulled edits — nudge loudly.
# (Symlinked edits are live for everything else; these are the exceptions that bit us.)
if git diff --name-only "$before" "$after" | grep -q '\.config/llamacpp/' \
  && systemctl cat llama.service &>/dev/null; then
  echo ""
  echo "⚠⚠  llamacpp presets changed — the router reads them only at startup. Apply with:"
  echo "      sudo systemctl restart llama.service"
  echo ""
fi

# A unit file is read from /etc, not through the stow symlink — needs daemon-reload as well.
if git diff --name-only "$before" "$after" | grep -q '\.config/whisper/' \
  && systemctl cat whisper.service &>/dev/null; then
  echo ""
  echo "⚠⚠  whisper unit changed — apply with:"
  echo "      sudo systemctl daemon-reload && sudo systemctl restart whisper.service"
  echo ""
fi

# Modified files (M) are live only through INTACT symlinks — a live file severed by an
# atomic rewrite (the recurring claude/settings.json class) swallows pulled edits silently,
# so verify that premise per modified file instead of assuming it. Added/Deleted/Renamed
# always need (un)linking. The diff is captured once, not piped into `grep -q`: its early
# exit can SIGPIPE git under pipefail and turn the whole condition falsely negative.
changes="$(git diff --name-status "$before" "$after")"
need_restow=""
if printf '%s\n' "$changes" | grep -qE '^(A|D|R)'; then
  need_restow="files added/removed/renamed"
else
  # map each modified repo path (package/.dotpath) to its live counterpart; a real file
  # (not a symlink) sitting there means the pulled edit did NOT land
  while IFS= read -r rel; do
    live="$HOME/$rel"
    if [ -e "$live" ] && [ ! -L "$live" ]; then
      echo "note: ~/$rel is a real file, not a symlink into the repo — the pulled edit has NOT landed there."
      need_restow="severed symlink(s)"
    fi
  done < <(printf '%s\n' "$changes" | awk -F'\t' '$1 ~ /^M/ && $2 ~ /^[^\/]+\/\./ { sub(/^[^\/]+\//, "", $2); print $2 }')
fi

if [ -n "$need_restow" ]; then
  echo "$need_restow — re-linking via install.sh (this may reload some apps)…"
  # Normally called with no argument, so install.sh resolves the host from ~/.config/dots-host —
  # the one recorded by the last install.sh run here. That is exactly why the host must not be
  # derived from `hostname -s`: this path is automatic and has nothing to pass. An explicit
  # `dotsync <host>` is forwarded through for the rare override.
  exec "$DOTS/install.sh" "$@"
else
  echo "edits only — already live through the symlinks; no re-stow, no reload needed."
fi