#!/usr/bin/env bash
# Bumps the NixOS release branch this flake tracks — flake.nix's
# `nixpkgs.url` and `home-manager.url` — in one place, via targeted
# substitution of just those two lines. Deliberately does NOT touch any
# `system.stateVersion` anywhere in the repo: per NixOS's own docs, that
# value must stay fixed at whatever it was on a host's first install (it
# pins on-disk data-format defaults, not "which nixpkgs release am I on"),
# so it's never something a channel bump should follow.
#
# scripts/codex-maintenance.sh's own `nixos-25.11` pin (used only to fetch
# nixpkgs-fmt/statix — see CLAUDE.md) is a separate, independently-versioned
# reference on purpose: it doesn't have to track the flake's own nixpkgs
# input, since the tooling just needs to build, not match. Bump it with
# --tooling if you want it moved too; the default run leaves it alone.
set -euo pipefail

repo_root="$(cd "$(dirname "$0")/.." && pwd)"
flake_nix="${repo_root}/flake.nix"
maintenance_sh="${repo_root}/scripts/codex-maintenance.sh"
claude_md="${repo_root}/CLAUDE.md"

usage() {
  cat <<EOF
Usage: $0 <release> [--tooling <release>]

  <release>            New NixOS release for flake.nix's nixpkgs.url and
                        home-manager.url, e.g. 26.11
  --tooling <release>  Also bump scripts/codex-maintenance.sh's separate
                        nixpkgs-fmt/statix pin (and its mention in
                        CLAUDE.md) to this release. Independent of the
                        first argument — pass the same value if you want
                        both in sync, a different one if you don't.

Examples:
  $0 26.11
  $0 26.11 --tooling 26.11
EOF
}

release_re='^[0-9]{2}\.(05|11)$'

if [[ $# -eq 0 || "$1" == "-h" || "$1" == "--help" ]]; then
  usage
  exit 0
fi

new_release="$1"
shift

tooling_release=""
while [[ $# -gt 0 ]]; do
  case "$1" in
  --tooling)
    tooling_release="${2:?--tooling requires a release argument}"
    shift 2
    ;;
  *)
    echo "Unknown argument: $1" >&2
    usage >&2
    exit 1
    ;;
  esac
done

check_release_format() {
  local release="$1"
  if [[ ! "$release" =~ $release_re ]]; then
    echo "ERROR: '$release' doesn't look like a NixOS release (expected e.g. 26.11)" >&2
    exit 1
  fi
}

check_branch_exists() {
  local repo_url="$1" branch="$2"
  echo "Checking '$branch' exists on $repo_url..."
  if ! git ls-remote --exit-code --heads "$repo_url" "$branch" >/dev/null; then
    echo "ERROR: branch '$branch' not found on $repo_url. Typo, or not cut yet?" >&2
    exit 1
  fi
}

check_release_format "$new_release"

current_release="$(grep -oE 'nixos-[0-9]{2}\.[0-9]{2}' "$flake_nix" | head -1 | sed 's/^nixos-//')"
if [[ -z "$current_release" ]]; then
  echo "ERROR: couldn't find flake.nix's current nixpkgs release" >&2
  exit 1
fi

if [[ "$current_release" == "$new_release" ]]; then
  echo "flake.nix is already on $new_release."
else
  echo "Bumping flake.nix's nixpkgs/home-manager release: $current_release -> $new_release"
  check_branch_exists "https://github.com/NixOS/nixpkgs.git" "nixos-$new_release"
  check_branch_exists "https://github.com/nix-community/home-manager.git" "release-$new_release"

  sed -i \
    -e "s|github:NixOS/nixpkgs/nixos-${current_release}|github:NixOS/nixpkgs/nixos-${new_release}|" \
    -e "s|github:nix-community/home-manager/release-${current_release}|github:nix-community/home-manager/release-${new_release}|" \
    "$flake_nix"

  echo "Updated:"
  grep -n "nixos-${new_release}\|release-${new_release}" "$flake_nix"
fi

if [[ -n "$tooling_release" ]]; then
  check_release_format "$tooling_release"

  current_tooling_release="$(grep -oE 'nixos-[0-9]{2}\.[0-9]{2}' "$maintenance_sh" | head -1 | sed 's/^nixos-//')"

  if [[ "$current_tooling_release" == "$tooling_release" ]]; then
    echo "codex-maintenance.sh's tooling pin is already on $tooling_release."
  else
    echo "Bumping codex-maintenance.sh's nixpkgs-fmt/statix pin: $current_tooling_release -> $tooling_release"
    check_branch_exists "https://github.com/NixOS/nixpkgs.git" "nixos-$tooling_release"

    sed -i "s|github:NixOS/nixpkgs/nixos-${current_tooling_release}|github:NixOS/nixpkgs/nixos-${tooling_release}|g" \
      "$maintenance_sh"
    sed -i "s|nixos-${current_tooling_release}|nixos-${tooling_release}|g" \
      "$claude_md"

    echo "Updated:"
    grep -n "nixos-${tooling_release}" "$maintenance_sh" "$claude_md"
  fi
fi

echo
echo "flake.lock still points at the old input revisions until refreshed. Either:"
echo "  nix flake update nixpkgs home-manager   # just these two inputs"
echo "  nix flake update                        # everything — see docs/flake-lock-automation.md"
echo
echo "Then run 'bash scripts/codex-maintenance.sh --full-check --dry-run' before"
echo "committing — a channel bump can shift option defaults across every host,"
echo "and only --dry-run actually builds anything to catch that."