#!/usr/bin/env bash
# Deploy the unified dots for this machine using GNU Stow.
#
#   ./install.sh [host]       host defaults to $(hostname -s)
#   ./install.sh -n [host]    dry-run (preview, no changes)
#   ./install.sh -a [host]    first run on a machine that still has real config files:
#                             --adopt them into the repo, then review `git diff` and
#                             `git restore .` to keep the repo (merged) versions.
#   ./install.sh -D [host]    revert: unstow this host's symlinks (repo + real files untouched)
#   ./install.sh -h           show all options
#
# Layering (later wins): common -> gui -> <host>
#   - common : shared everywhere
#   - gui    : GUI configs (skipped on headless machines — see the marker below)
#   - <host> : per-machine overrides (top-level package), stowed last with --override
# All packages live at the repo root so they share one stow dir — required for
# --override to let a host file take over a common/gui file of the same path.
# --no-folding: every file is symlinked individually (dirs stay real) so a host can
# override a single file in a shared dir without shadowing the rest.
#
# Idempotent: re-run any time. Adding/removing files in the repo needs a re-run
# (editing an existing file does not — symlinks point straight at the repo file).
set -uo pipefail

# --- headless (terminal-only, no GUI) machines skip the gui package ---
# A machine is "headless" if this marker file exists. It's machine-local (not tracked by the repo)
# and hostname-independent, so the same terminal-only setup replicates across any number of machines
# — run once on each tty-only box:   touch ~/.config/dots-headless
HEADLESS_MARKER="${XDG_CONFIG_HOME:-$HOME/.config}/dots-headless"

usage() {
  cat <<'EOF'
Deploy this machine's dotfiles with GNU Stow.

Usage: ./install.sh [options] [host]

  host             profile to deploy (default: `hostname -s`)
  -n, --dry-run    preview stow actions; change nothing
  -a, --adopt      first run on a machine with existing real config files: adopt
                   them into the repo, then review `git diff` and `git restore .`
  -D, --unstow     revert: remove this host's stow symlinks (repo + real files kept)
  -h, --help       show this help and exit

Layering (later wins): common -> gui -> <host>. A machine with ~/.config/dots-headless
skips gui (and has any stray gui unstowed). Run from inside the repo (~/.dots).
EOF
}

# --- args ---
DRY=""
ADOPT=""
UNSTOW=0
ARGS=()
for a in "$@"; do
  case "$a" in
    -n|--dry-run) DRY="-n" ;;
    -a|--adopt)   ADOPT="--adopt" ;;
    -D|--unstow|--delete) UNSTOW=1 ;;
    -h|--help)    usage; exit 0 ;;
    -*) echo "unknown option: $a" >&2; usage >&2; exit 2 ;;
    *) ARGS+=("$a") ;;
  esac
done
HOST="${ARGS[0]:-$(hostname -s)}"

DOTS="$(cd "$(dirname "$(readlink -f "${BASH_SOURCE[0]}")")" && pwd)"
command -v stow >/dev/null 2>&1 || { echo "error: GNU stow is not installed (pacman -S stow)" >&2; exit 1; }

gui=true
[ -e "$HEADLESS_MARKER" ] && gui=false

echo "host=$HOST  dots=$DOTS  gui=$gui${DRY:+  (dry-run)}"

# --- revert mode: unstow this host's packages (reverse of deploy), leave repo + real files intact ---
if [ "$UNSTOW" -eq 1 ]; then
  verb="unstowed"; [ -n "$DRY" ] && verb="would unstow"
  for p in "$HOST" gui common; do
    [ -d "$DOTS/$p" ] || continue
    if stow $DRY -d "$DOTS" -t "$HOME" -D "$p" 2>/dev/null; then
      echo "  $verb $p"
    fi
    # prune the now-empty dirs this package created under ~/.config (empty only — never real files)
    if [ -z "$DRY" ] && [ -d "$DOTS/$p/.config" ]; then
      for d in "$DOTS/$p"/.config/*/; do
        t="$HOME/.config/$(basename "$d")"
        [ -d "$t" ] && find "$t" -type d -empty -delete 2>/dev/null || true
      done
    fi
  done
  if [ -n "$DRY" ]; then
    echo "(dry-run) nothing changed."
  else
    echo "reverted — removed this host's stow symlinks. ~/.dots and any real files are untouched."
    echo "note: ~/.claude/* links (from link.sh) are separate; remove by hand if you want those gone too."
  fi
  exit 0
fi

# 0. self-heal symlinks that stow would reject ("not owned by stow"), which otherwise aborts all of
#    common. Two stale-link classes a prior link.sh/heal can leave behind:
#      - hooks/skills folded into an ABSOLUTE dir-symlink (they must be real dirs) — drop it entirely.
#      - a file item re-linked with an ABSOLUTE target instead of stow's relative one — drop it.
#    Only ever removes a *symlink* here (never a real file/dir), so nothing is lost; stow then
#    recreates the correct relative link. A drifted *real* file is left for link.sh's drift guard
#    (or `-a` to adopt) to reconcile, since it may hold un-synced edits.
if [ -z "$DRY" ]; then
  for d in hooks skills; do
    t="$HOME/.config/claude/$d"
    [ -L "$t" ] && { rm -f "$t"; echo "  cleared stale folded symlink ~/.config/claude/$d"; }
  done
  for f in settings.json statusline.py keybindings.json CLAUDE.md; do
    t="$HOME/.config/claude/$f"
    case "$(readlink "$t" 2>/dev/null)" in
    /*) rm -f "$t"; echo "  cleared absolute symlink ~/.config/claude/$f (stow will relink)" ;;
    esac
  done
fi

# 1. release the host overlay first so base restows never conflict on overridden files
if [ -d "$DOTS/$HOST" ] && [ -z "$DRY" ]; then
  stow -d "$DOTS" -t "$HOME" -D "$HOST" 2>/dev/null || true
fi

# stow one package; track failures instead of silently continuing and reporting success
FAIL=0
stow_pkg() { # stow_pkg <label> <stow args...>
  local label="$1"; shift
  if stow $DRY $ADOPT --no-folding -d "$DOTS" -t "$HOME" "$@"; then
    echo "  stowed $label"
  else
    FAIL=1
  fi
}

# 2. (re)stow base layers
# In dry-run the host overlay is NOT released first (step 1 is real-run-only), so simulating
# a base restow would report conflicts on host-overridden files that a real run never hits.
# --override in the simulation makes its outcome (exit status) match the real sequence.
DRYOVR=""
[ -n "$DRY" ] && DRYOVR="--override=.*"
stow_pkg common $DRYOVR -R common
if [ "$gui" = true ]; then
  stow_pkg gui $DRYOVR -R gui
else
  # headless: ensure no stray gui is left deployed (self-heals a prior wrong run)
  if stow $DRY -d "$DOTS" -t "$HOME" -D gui 2>/dev/null; then
    test -z "$DRY" && echo "  ensured gui not deployed (headless)"
  fi
  # prune the now-empty dirs that unstowing gui leaves behind (only removes empty ones)
  if [ -z "$DRY" ] && [ -d "$DOTS/gui/.config" ]; then
    for d in "$DOTS"/gui/.config/*/; do
      t="$HOME/.config/$(basename "$d")"
      [ -d "$t" ] && find "$t" -type d -empty -delete 2>/dev/null || true
    done
  fi
fi

# 3. stow the host overlay last, overriding base files
if [ -d "$DOTS/$HOST" ]; then
  stow_pkg "$HOST" --override='.*' -S "$HOST"
else
  echo "  no '$HOST' overlay — using common only (add a top-level '$HOST/' package for host overrides)"
fi

# 4. surface Claude config into ~/.claude (only if everything stowed cleanly)
if [ "$FAIL" -eq 0 ] && [ -z "$DRY" ] && [ -f "$HOME/.config/claude/link.sh" ]; then
  bash "$HOME/.config/claude/link.sh"
  echo "  linked ~/.claude"
fi

# fail loudly with a non-zero exit so callers / re-runs can tell it did not apply
if [ "$FAIL" -ne 0 ]; then
  echo "FAILED: some packages could not be stowed (conflicts above)." >&2
  echo "  first run on a machine with existing real files? re-run with -a to adopt them." >&2
  exit 1
fi

echo "done."

if [ -n "$ADOPT" ] && [ -z "$DRY" ]; then
  echo
  echo "adopted this machine's existing files INTO the repo working tree — heads up: they can appear"
  echo "under common/ or gui/ even when they are really host-specific. Review, then normally discard:"
  echo "  git -C \"$DOTS\" diff        # inspect the adopted drift"
  echo "  git -C \"$DOTS\" restore .   # discard it, keep the merged repo versions (recommended)"
  echo "To KEEP a change, hand-copy it into the right package (common/gui/$HOST) — do not blanket-commit"
  echo "the adopted diff, or host-specific content leaks into shared packages. (restore . drops ALL"
  echo "uncommitted edits — fine on a fresh clone.)"
fi