#!/usr/bin/env bash
set -euo pipefail

ROOT="${1:-../Modules}"   # pass root dir, defaults to Modules

# Generate module boilerplate for each .nix (excluding default.nix)
gen_module_boilerplate() {
  local file="$1"
  local module
  module="$(basename "$file" .nix)"

  # skip if non-empty
  if [[ -s "$file" ]]; then
    echo "Skipping non-empty $file"
    return
  fi

  local ns target
  if [[ "$file" == *"/Home/"* ]]; then
    ns="home"
    target="home.packages"
  else
    ns="system"
    target="environment.systemPackages"
  fi

  cat > "$file" <<EOF
{ config, lib, pkgs, ... }:

let
  cfg = config.nyx-module.${ns}.${module};
in
{
  options.nyx-module.${ns}.${module} = {
    enable = lib.mkEnableOption "Enable ${module} (${ns}) module";

    package = lib.mkOption {
      type = lib.types.package;
      default = pkgs.${module};
      description = "Package to install for ${module}.";
    };
  };

  config = lib.mkIf cfg.enable {
    ${target} = [ cfg.package ];
  };
}
EOF
  echo "Wrote boilerplate for $file"
}

gen_default_for_dir() {
  local dir="$1"
  local file="${dir}/default.nix"

  # collect non-default nix files in this directory
  local local_modules=()
  for f in "$dir"/*.nix; do
    [[ -f "$f" && "$(basename "$f")" != "default.nix" ]] && local_modules+=("./$(basename "$f")")
  done

  # if no local nix files, collect subdirs that contain default.nix
  if (( ${#local_modules[@]} > 0 )); then
    new_imports=("${local_modules[@]}")
  else
    local subdirs=()
    for sub in "$dir"/*/; do
      [[ -d "$sub" && -f "$sub/default.nix" ]] && subdirs+=("./$(basename "$sub")")
    done
    new_imports=("${subdirs[@]}")
  fi

  mkdir -p "$dir"

  if [[ -f "$file" ]]; then
    # Replace imports block in place
    awk -v n="${#new_imports[@]}" -v imports="$(printf '%s\n' "${new_imports[@]}")" '
      BEGIN {
        split(imports, arr, "\n")
        printing=1
      }
      /imports = \[/ {
        print "  imports = ["
        for (i=1; i<=n; i++) {
          print "    " arr[i]
        }
        print "  ];"
        # skip until closing bracket
        while (getline > 0) {
          if ($0 ~ /\];/) break
        }
        next
      }
      { print }
    ' "$file" > "$file.tmp" && mv "$file.tmp" "$file"
    echo "Updated imports in $file"
  else
    # brand new default.nix
    {
      echo "{ config, lib, pkgs, ... }:"
      echo
      echo "{"
      echo "  imports = ["
      for imp in "${new_imports[@]}"; do
        echo "    $imp"
      done
      echo "  ];"
      echo "}"
    } > "$file"
    echo "Created $file"
  fi
}

# Walk the tree
echo "Generating nix module boilerplates under $ROOT ..."

# 1. Generate boilerplate for all non-default modules
find "$ROOT" -type f -name "*.nix" ! -name "default.nix" | while read -r f; do
  gen_module_boilerplate "$f"
done

# 2. Generate default.nix in every directory
find "$ROOT" -type d | while read -r d; do
  gen_default_for_dir "$d"
done

echo "Done! All modules + defaults generated."