#!/usr/bin/env bash
# deploy.sh — stow-equivalent deployment of the dotfiles/ packages in this repo.
#
# Model: the repo checkout IS the deployment. Packages are home-relative trees
# under dotfiles/<pkg>/; deploying replaces live files with symlinks into the
# repo so `git pull` + `deploy.sh` is the whole propagation story.
#
# Modes:
#   deploy.sh              sync (default): adopt identicals, link new, quarantine-and-replace divergents
#   deploy.sh --check      dry-run report only; writes nothing
#   deploy.sh --adopt      like sync but divergents are reported and SKIPPED, not quarantined
#
# Host divergence: a package named zz-$(hostname) is stowed LAST with override
# semantics (its files replace symlinks from base packages).
#
# Special cases:
#   - dconf package: dump.txt is loaded via `dconf load /` instead of symlinked.
#   - systemd-user: after linking, daemon-reload + enable --now units whose
#     ExecStart binary resolves on THIS machine (silent no-op elsewhere).
set -euo pipefail

REPO="$(git -C "$(dirname "$(realpath "$0")")" rev-parse --show-toplevel 2>/dev/null || true)"
REPO="${DEPLOY_REPO:-$REPO}"
PKGS_DIR="$REPO/dotfiles"
HOST="${DEPLOY_HOST:-$(hostname)}"
QUAR="$REPO/.quarantine"

MODE="sync"
case "${1:-}" in
  --check) MODE="check" ;;
  --adopt) MODE="adopt" ;;
  ""|sync) MODE="sync" ;;
  *) echo "usage: deploy.sh [--check|--adopt|sync]" >&2; exit 2 ;;
esac

[ -d "$PKGS_DIR" ] || { echo "deploy.sh: no dotfiles/ under $REPO" >&2; exit 1; }

# packages = all dirs in dotfiles/, override package last
mapfile -t PKGS < <(find "$PKGS_DIR" -maxdepth 1 -mindepth 1 -type d ! -name "zz-*" | sort)
OVR="$PKGS_DIR/zz-$HOST"
[ -d "$OVR" ] && PKGS+=("$OVR")

actions=0; quarantined=0; skipped=0

deploy_file() { # $1 = repo file path, $2 = home-relative target path
  local src="$1" tgt="$HOME/$2"
  if [ -L "$tgt" ]; then
    if [ "$(realpath "$tgt")" = "$(realpath "$src")" ]; then return 0; fi # already deployed
    case "$MODE" in
      check) echo "RELINK $2 (managed symlink changing owners)" ;;
      adopt) echo "SKIP   $2 (foreign symlink, --adopt does not overwrite)" ; skipped=$((skipped+1)) ;;
      sync)
        if [[ "$(realpath "$tgt")" == "$REPO/"* ]]; then
          # managed file changing owners between packages: silent relink, nothing to quarantine
          ln -sfn "$(realpath "$src")" "$tgt"; actions=$((actions+1))
        else
          ts="$(date +%Y%m%d-%H%M%S)-$$"
          dest="$QUAR/$HOST/$ts/$2"
          mkdir -p "$(dirname "$dest")"
          mv -- "$tgt" "$dest"
          ln -sfn "$(realpath "$src")" "$tgt"
          actions=$((actions+1)); quarantined=$((quarantined+1))
          echo "QUAR   $2 -> .quarantine/$HOST/$ts/$2"
        fi
        ;;
    esac
    return 0
  fi
  if [ -e "$tgt" ]; then
    if cmp -s "$src" "$tgt"; then
      if [ "$MODE" = "check" ]; then echo "ADOPT  $2 (identical, will symlink)"; return 0; fi
      ln -sfn "$(realpath "$src")" "$tgt"; actions=$((actions+1)); return 0
    fi
    case "$MODE" in
      check) echo "DRIFT  $2 (differs from repo; sync would quarantine)" ;;
      adopt) echo "SKIP   $2 (divergent, --adopt does not overwrite)" ; skipped=$((skipped+1)) ;;
      sync)
        ts="$(date +%Y%m%d-%H%M%S)-$$"
        dest="$QUAR/$HOST/$ts/$2"
        mkdir -p "$(dirname "$dest")"
        mv -- "$tgt" "$dest"
        ln -sfn "$(realpath "$src")" "$tgt"
        actions=$((actions+1)); quarantined=$((quarantined+1))
        echo "QUAR   $2 -> .quarantine/$HOST/$ts/$2"
        ;;
    esac
    return 0
  fi
  if [ "$MODE" = "check" ]; then echo "LINK   $2 (missing, will symlink)"; return 0; fi
  mkdir -p "$(dirname "$tgt")"
  ln -sfn "$(realpath "$src")" "$tgt"; actions=$((actions+1))
}

for pkg in "${PKGS[@]}"; do
  pkgname="$(basename "$pkg")"
  # dconf package: load dump instead of symlinking
  if [ "$pkgname" = "dconf" ] && [ -f "$pkg/dump.txt" ]; then
    if [ "$MODE" != "check" ]; then
      if command -v dconf >/dev/null; then dconf load / < "$pkg/dump.txt" && echo "LOAD   $pkgname/dump.txt -> dconf"; fi
    else
      echo "LOAD   $pkgname/dump.txt (dconf load / would run on sync)"
    fi
    continue
  fi
  while IFS= read -r -d '' f; do
    rel="${f#"$pkg"/}"
    # override packages nest base-package dirs internally: strip that segment for targets
    if [ "${pkgname#zz-}" != "$pkgname" ]; then case "$rel" in */*) [ -d "$PKGS_DIR/${rel%%/*}" ] && rel="${rel#*/}";; esac; fi
    deploy_file "$f" "$rel"
  done < <(find "$pkg" \( -type f -o -type l \) ! -name 'dump.txt' ! -path '*/.AGENTTRASH/*' -print0)
done

if [ "$MODE" != "check" ] && [ -d "$PKGS_DIR/systemd-user/.config/systemd/user" ]; then
  systemctl --user daemon-reload || true
  for unit in "$PKGS_DIR"/systemd-user/.config/systemd/user/*.service; do
    [ -e "$unit" ] || continue
    bin="$(sed -n 's/^ExecStart=\([^ ]*\).*/\1/p' "$unit" | head -1)"
    if [ -n "$bin" ] && command -v "$bin" >/dev/null 2>&1; then
      systemctl --user enable --now "$(basename "$unit")" || true
      echo "ENABLE $(basename "$unit") (ExecStart resolves here)"
    else
      echo "SKIP   $(basename "$unit") (ExecStart '$bin' absent on this host)"
    fi
  done
fi

# keep the secret gate armed on every machine that deploys
git -C "$REPO" config core.hooksPath .githooks

echo "deploy.sh [$MODE] host=$HOST repo=$REPO — actions=$actions quarantined=$quarantined skipped=$skipped"