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

# Install Nix package manager and set up unstable channel.

# Detect OS.
os=""
if [[ -f /etc/os-release ]]; then
    source /etc/os-release
    os="${ID,,}"
else
    os="$(uname -s | tr '[:upper:]' '[:lower:]')"
fi

# Install Nix if not already installed.
if ! command -v nix &>/dev/null; then
    case "$os" in
    darwin)
        echo "Installing Nix..."
        sh <(curl --proto '=https' --tlsv1.2 -L https://nixos.org/nix/install)
        ;;
    fedora)
        echo "Nix should be installed via dnf: sudo dnf install nix"
        exit 1
        ;;
    *)
        echo "Nix installation is not supported on this OS ($os)."
        exit 1
        ;;
    esac
fi

# Enable nix-daemon on Fedora (if installed via dnf).
if [[ "$os" == "fedora" ]]; then
    echo "Enabling nix-daemon service..."
    sudo systemctl enable --now nix-daemon
fi

# Set up nixpkgs unstable channel (works on all systems with Nix).
echo "Setting up nixpkgs unstable channel..."
nix registry add nixpkgs github:NixOS/nixpkgs/nixpkgs-unstable
nix registry pin nixpkgs