#! /usr/bin/env bash

set -e

dest="/nix"
self="$(dirname "$0")"
nix="@nix@"

if ! [ -e $self/.reginfo ]; then
    echo "$0: incomplete installer (.reginfo is missing)" >&2
    exit 1
fi

if [ -z "$USER" ]; then
    echo "$0: \$USER is not set" >&2
    exit 1
fi

if [ "$(id -u)" -eq 0 ]; then
    echo "warning: installing Nix as root is not recommended" >&2
    exit 1
fi

echo "performing a single-user installation of Nix..." >&2

if ! [ -e $dest ]; then
    cmd="mkdir -m 0755 $dest && chown $USER $dest"
    echo "directory $dest does not exist; creating it by running \`$cmd' using sudo" >&2
    if ! sudo sh -c "$cmd"; then
        echo "$0: please manually run \`$cmd' as root to create $dest" >&2
        exit 1
    fi
fi

if ! [ -w $dest ]; then
    echo "$0: directory $dest exists, but is not writable by you; please run \`chown -R $USER $dest' as root" >&2
    exit 1
fi

mkdir -p $dest/store

echo -n "copying Nix to $dest/store..." >&2

for i in $(cd $self/store && echo *); do
    echo -n "." >&2
    i_tmp="$dest/store/$i.$$"
    if [ -e "$i_tmp" ]; then
        rm -rf "$i_tmp"
    fi
    if ! [ -e "$dest/store/$i" ]; then
        cp -Rp "$self/store/$i" "$i_tmp"
        mv "$i_tmp" "$dest/store/$i"
    fi
done
echo "" >&2

echo "initialising Nix database..." >&2
if ! $nix/bin/nix-store --init; then
    echo "$0: failed to initialize the Nix database" >&2
    exit 1
fi

if ! $nix/bin/nix-store --load-db < $self/.reginfo; then
    echo "$0: unable to register valid paths" >&2
    exit 1
fi

. $nix/etc/profile.d/nix.sh

if ! $nix/bin/nix-env -i $nix; then
    echo "$0: unable to install Nix into your default profile" >&2
    exit 1
fi

# Subscribe the user to the Nixpkgs channel and fetch it.
if ! $nix/bin/nix-channel --list | grep -q "^nixpkgs "; then
    $nix/bin/nix-channel --add http://nixos.org/channels/nixpkgs-unstable
fi
$nix/bin/nix-channel --update nixpkgs

# Make the shell source nix.sh during login.
p=$NIX_LINK/etc/profile.d/nix.sh

added=
for i in .bash_profile .bash_login .profile; do
    fn="$HOME/$i"
    if [ -e "$fn" ]; then
        if ! grep -q "$p" "$fn"; then
            echo "modifying $fn..." >&2
            echo "if [ -e $p ]; then . $p; fi # added by Nix installer" >> $fn
        fi
        added=1
        break
    fi
done

if [ -z "$added" ]; then
    cat >&2 <<EOF

Installation finished!  To ensure that the necessary environment
variables are set, please add the line

  . $p

to your shell profile (e.g. ~/.profile).
EOF
else
    cat >&2 <<EOF

Installation finished!  To ensure that the necessary environment
variables are set, either log in again, or type

  . $p

in your shell.
EOF
fi