prop/nix/shell.nix

{
  lib,
  stdenv,
  mkShell,
  writeShellScriptBin,
  # Elixir/Erlang
  elixir,
  # Database
  postgresql_16,
  # Rust toolchain
  rustup,
  rust-analyzer,
  # Development tools
  git-lfs,
  inotify-tools,
  # LSPs and formatters
  elixir-ls,
  nixfmt,
  shellcheck,
  # Pre-commit hooks
  pre-commit-hooks,
}:

let
  # PostgreSQL data directory (local to project)
  pgDataDir = ".nix-postgres";
  pgPort = "5432";
  pgHost = "localhost";

  # Service management flag
  servicesFlag = ".nix-services-started";

  # Script to start PostgreSQL
  startServices = writeShellScriptBin "start-services" ''
        set -e

        echo "Starting development services..."

        # Check if already started
        if [ -f "${servicesFlag}" ]; then
          echo "Services already running (remove ${servicesFlag} to force restart)"
          exit 0
        fi

        # Initialize PostgreSQL if needed
        if [ ! -d "${pgDataDir}" ]; then
          echo "Initializing PostgreSQL database..."
          ${postgresql_16}/bin/initdb -D ${pgDataDir} -U $USER --encoding=UTF8 --locale=en_US.UTF-8

          # Configure PostgreSQL for development (fast but unsafe for production)
          cat >> ${pgDataDir}/postgresql.conf << EOF
    # Development configuration
    max_connections = 100
    shared_buffers = 128MB
    fsync = off
    synchronous_commit = off
    full_page_writes = off
    EOF
        fi

        # Check if PostgreSQL is already running on this port
        if ${postgresql_16}/bin/pg_isready -h ${pgHost} -p ${pgPort} > /dev/null 2>&1; then
          echo "PostgreSQL already running on port ${pgPort}"
        else
          # Start PostgreSQL
          echo "Starting PostgreSQL on port ${pgPort}..."
          ${postgresql_16}/bin/pg_ctl -D ${pgDataDir} -l ${pgDataDir}/logfile -o "-p ${pgPort}" start

          # Wait for PostgreSQL to be ready
          for i in {1..30}; do
            if ${postgresql_16}/bin/pg_isready -h ${pgHost} -p ${pgPort} > /dev/null 2>&1; then
              break
            fi
            if [ $i -eq 30 ]; then
              echo "PostgreSQL failed to start within 30 seconds"
              echo "Check ${pgDataDir}/logfile for details"
              exit 1
            fi
            sleep 1
          done
          echo "PostgreSQL started successfully"
        fi

        # Create postgres role if it doesn't exist (needed by some tools)
        ${postgresql_16}/bin/psql -h ${pgHost} -p ${pgPort} -U $USER -d postgres -tc \
          "SELECT 1 FROM pg_roles WHERE rolname='postgres'" | grep -q 1 || \
          ${postgresql_16}/bin/psql -h ${pgHost} -p ${pgPort} -U $USER -d postgres -c \
            "CREATE ROLE postgres WITH SUPERUSER LOGIN;"

        # Create development and test databases
        for db in prop_dev prop_test; do
          ${postgresql_16}/bin/psql -h ${pgHost} -p ${pgPort} -U $USER -d postgres -tc \
            "SELECT 1 FROM pg_database WHERE datname='$db'" | grep -q 1 || \
            ${postgresql_16}/bin/createdb -h ${pgHost} -p ${pgPort} -U $USER $db
        done

        # Mark services as started
        touch ${servicesFlag}

        echo ""
        echo "Development environment ready!"
        echo ""
        echo "PostgreSQL: ${pgHost}:${pgPort} (databases: prop_dev, prop_test)"
        echo ""
  '';

  # Script to stop PostgreSQL
  stopServices = writeShellScriptBin "stop-services" ''
    set -e

    echo "Stopping development services..."

    # Stop PostgreSQL
    if [ -d "${pgDataDir}" ]; then
      ${postgresql_16}/bin/pg_ctl -D ${pgDataDir} stop -m fast 2>/dev/null || true
      echo "PostgreSQL stopped"
    fi

    # Remove services flag
    rm -f ${servicesFlag}

    echo "Services stopped successfully"
  '';

  # Pre-commit hooks configuration
  pre-commit-check = pre-commit-hooks.run {
    src = ../.;
    hooks = {
      # Elixir formatting
      mix-format = {
        enable = true;
        name = "mix format";
        entry = "mix format --check-formatted";
        files = "\\.(ex|exs)$";
        pass_filenames = false;
      };

      # Credo linting
      credo = {
        enable = true;
        name = "credo";
        entry = "mix credo --strict";
        files = "\\.(ex|exs)$";
        pass_filenames = false;
      };

      # Rust formatting and linting
      cargo-fmt = {
        enable = true;
        name = "cargo fmt";
        entry = "cargo fmt --all --check";
        files = "\\.rs$";
        pass_filenames = false;
      };

      cargo-clippy = {
        enable = true;
        name = "cargo clippy";
        entry = "cargo clippy --all-targets -- -D warnings";
        files = "\\.rs$";
        pass_filenames = false;
      };

      # Nix formatting
      nixfmt = {
        enable = true;
        entry = "${nixfmt}/bin/nixfmt";
      };

      # Shellcheck for shell scripts
      shellcheck.enable = true;
    };
  };

in
mkShell {
  name = "prop-dev";

  # Development tools
  buildInputs = [
    # Elixir/Erlang
    elixir

    # Database
    postgresql_16

    # Rust toolchain
    rustup
    rust-analyzer

    # Development tools
    git-lfs

    # LSPs and formatters
    elixir-ls
    nixfmt
    shellcheck

    # Service management scripts
    startServices
    stopServices
  ]
  ++ lib.optionals stdenv.isLinux [
    # Linux-only tools
    inotify-tools # For Mix file watching
  ];

  # Environment variables
  shellHook = ''
    # Set Mix and Hex home to local directories (avoid polluting $HOME)
    export MIX_HOME="$PWD/.nix-mix"
    export HEX_HOME="$PWD/.nix-hex"
    mkdir -p "$MIX_HOME" "$HEX_HOME"

    # PostgreSQL connection
    export PGHOST="${pgHost}"
    export PGPORT="${pgPort}"
    export PGUSER="$USER"
    export DATABASE_URL="ecto://$USER@${pgHost}:${pgPort}/prop_dev"

    # Development secrets (DO NOT use in production)
    export SECRET_KEY_BASE="dev_secret_key_base_at_least_64_bytes_long_for_phoenix_to_accept_it_safely"
    export RELEASE_COOKIE="dev_release_cookie_for_distributed_erlang"

    # Development environment
    export MIX_ENV=dev
    export PHX_HOST=localhost
    export PORT=4000

    # Ensure Erlang can find NIF libraries
    export ERL_AFLAGS="-kernel shell_history enabled"

    # Rust: set up stable toolchain if not already installed
    if ! rustup show active-toolchain 2>/dev/null | grep -q stable; then
      rustup default stable 2>/dev/null || true
    fi

    # Install Hex and Rebar3 if not already installed
    mix local.hex --force --if-missing > /dev/null 2>&1
    mix local.rebar --force --if-missing > /dev/null 2>&1

    # Auto-start services on first shell entry
    if [ ! -f "${servicesFlag}" ]; then
      ${startServices}/bin/start-services

      # Run migrations if databases exist and Mix deps are available
      if [ -d "deps" ] && mix ecto.migrate 2>/dev/null; then
        echo "Database migrations applied"
      fi
    fi

    # Install pre-commit hooks
    ${pre-commit-check.shellHook}

    # Welcome message
    echo ""
    echo "╔═══════════════════════════════════════════════════════════╗"
    echo "║                                                           ║"
    echo "║  Prop — Microwave Propagation Prediction                  ║"
    echo "║                                                           ║"
    echo "╚═══════════════════════════════════════════════════════════╝"
    echo ""
    echo "Available commands:"
    echo "  mix phx.server       - Start Phoenix development server"
    echo "  mix test             - Run test suite"
    echo "  mix precommit        - Run pre-commit checks (format, credo, test)"
    echo "  start-services       - Start PostgreSQL"
    echo "  stop-services        - Stop PostgreSQL"
    echo "  mix ecto.reset       - Reset database (drop, create, migrate, seed)"
    echo "  cargo build          - Build Rust crates (cd rust/prop_grid_rs)"
    echo "  cargo test           - Run Rust tests"
    echo ""
    echo "Services:"
    echo "  PostgreSQL: ${pgHost}:${pgPort}"
    echo ""
    echo "Documentation:"
    echo "  See CLAUDE.md and nix.md for more information"
    echo ""
  '';
}