#!/usr/bin/env bash

# Runs the command given in a Nix environment, and create it if it doesn't exist.
# Useful for environments where nix isn't installed / you do not have root access

# If you need a fresh slate:
# chmod +w .nix -R
# rm -rf .nix .nix-defexpr .nix-profile .config/nix .local/state/nix .local/share/nix .cache/nix

set -euo pipefail
SCRIPT_DIR=$( cd -- "$( dirname -- "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )

if [ ! -d /nix ]
then
    # Doesn't support architectures other than x86_64
    NIX_USER_CHROOT_URL=https://github.com/nix-community/nix-user-chroot/releases/download/1.2.2/nix-user-chroot-bin-1.2.2-x86_64-unknown-linux-musl
    NIX_USER_CHROOT_SHA256SUM=e11aff604bb8d3ffd1d9c0c68cd636816d7eb8da540de18ee3a41ccad7ac0972

    nix_user_chroot="$HOME/.local/bin/nix-user-chroot"
    mkdir -p "$(dirname "$nix_user_chroot")"

    nix_directory="$HOME/.nix"
    mkdir -p "$nix_directory"

    if [ ! -x "$nix_user_chroot" ] || ! echo "$NIX_USER_CHROOT_SHA256SUM $nix_user_chroot" | sha256sum --check --status
    then
        wget "$NIX_USER_CHROOT_URL" -O "$nix_user_chroot"
        echo "$NIX_USER_CHROOT_SHA256SUM $nix_user_chroot" | sha256sum --check --status
        chmod +x "$nix_user_chroot"
    fi
    exec "$nix_user_chroot" "$nix_directory" "$0" "$@"
    exit 1
fi

nix_profile_path="$HOME/.nix-profile/etc/profile.d/nix.sh"

if [ ! -f "$nix_profile_path" ]
then
    NIX_INSTALLER_URL=https://releases.nixos.org/nix/nix-2.19.2/install
    NIX_INSTALLER_SHA256SUM=435f0d7e11f7c7dffeeab0ec9cc55723f6d3c03352379d785633cf4ddb5caf90

    nix_installer="$(mktemp)"

    wget "$NIX_INSTALLER_URL" -O "$nix_installer"
    echo "$NIX_INSTALLER_SHA256SUM $nix_installer" | sha256sum --check --status
    chmod +x "$nix_installer"

    "$nix_installer" --no-daemon --yes --no-channel-add --no-modify-profile
fi

# TODO This installs nix in nix-env, which conflicts with home-manager activation.
# Workaround is temporarily set /nix/store-xxx-nix/bin in PATH

. "$nix_profile_path"

# TODO Useful the first time, but it becomes a bit long after a while
# "${SCRIPT_DIR}/add_channels.sh"

exec "$@"