#!/usr/bin/env sh
# this script is compatible with following shells:
# ash, dash, bash, zsh

VERBOSE="${VERBOSE:-1}"

NAME="$0"

die() {
    printf '%s:' "$NAME"
    printf ' %s' "$@"
    printf '\n'
    exit 1
} >&2

backup() {
    : "${1:?missing argument}"
    printf '%s\n' "backing up $1"
    mkdir -p "${backup_dir:?backup_dir unset}/$(dirname "$1")"
    [ ! -e "$backup_dir/$1" ] || die "backup already exists"
    mv "$1" "$backup_dir/$1"
}

hardlink() {
    : "${1:?missing argument}"
    : "${2:?missing argument}"
    if [ -e "$1" ]; then
        [ ! "$1" -ef "$2" ] || return 0
        if [ -h "$1" ]; then
            printf '%s\n' "removing symbolic link $1"
            rm "$1" || die "failed to remove symbolic link"
        fi
        if [ -s "$1" ]; then
            backup "$1" || die "$1 already exists"
        fi
    fi

    ln "$2" "$1" || die "failed to hardlink $1"
}

softlink_nix() {
    : "${1:?missing argument}"
    : "${2:?missing argument}"
    if [ -e "$1" ]; then
        if [ -h "$1" ]; then
            [ "$(readlink "$1")" != "$2" ] || return 0
            printf '%s\n' "removing symbolic link $1"
            rm "$1" || die "failed to remove symbolic link"
        else
            die "$1 already exists and is not a symbolic link"
        fi
    fi

    ln -s "$2" "$1" || die "failed to symlink $1"
}

list_files() {
    find "${1:-.}" -maxdepth 1 -printf "%P\n" | while read -r f; do
        [ "${#f}" -gt 0 ] || continue
        printf "%s\n" "$f"
    done
}

softlink_pseudo() {
    : "${1:?missing argument}"
    : "${2:?missing argument}"
    [ -d "$2" ] || die "$1 is not a directory to softlink"
    [ -d "$1" ] || mkdir "$1" || die "failed to mkdir $1"

    list_files "$2" | while read -r f; do
        local d1="$1/$f"
        local d2="$2/$f"

        if [ -d "$d2" ]; then
            if [ "$d1" != ".vim/bundle" ]; then # buggy on Windows
                [ "$VERBOSE" -lt 1 ] || printf '\033[34m / \033[0m %s %s\n' "$d1" "$d2" >&2
                softlink_pseudo "$d1" "$d2" || exit
            fi
        elif [ -f "$d2" ]; then
            [ "$VERBOSE" -lt 1 ] || printf '\033[34m * \033[0m %s\n' "$d1" >&2
            hardlink "$d1" "$d2" || exit
        else
            die "i don't know how to pseudo-symlink $d2"
        fi
    done || exit
}

find_new_files() {
    : "${1:?missing argument}"
    : "${2:?missing argument}"
    list_files "$1" | while read -r f; do
        local d1="$1/$f"
        local d2="$2/$f"
        [ "$d1" != ".vim/.netrwhist" ] || continue
        [ "$d1" != ".vim/backup" ] || continue
        [ "$d1" != ".vim/bundle" ] || continue
        [ "$d1" != ".vim/swp" ] || continue
        [ "$d1" != ".vim/undo" ] || continue
        if [ -d "$d2" ]; then
            find_new_files "$d1" "$d2"
        elif [ ! "$d1" -ef "$d2" ]; then
            local ind=
            [ ! -d "$d1" ] || ind=/
            if [ "$VERBOSE" -lt 1 ]; then
                printf ' + %s%s\n' "$d1" "$ind" >&2
            else
                #printf 'new destination file. consider manually moving it:\n' >&2
                printf '\033[32m + \033[0m %s%s\n' "$d1" "$ind" >&2
            fi
        fi
    done
}

softlink() {
    if [ -n "$MSYSTEM" ]; then
        # MSYS2 does not have nor emulate symbolic links.
        softlink_pseudo "$@"
        find_new_files "$@" # to make up for git status not seeing new files
    else
        softlink_nix "$@"
    fi
}

which readlink >/dev/null || die 'failed sanity check (check your $PATH)'

rc="$(readlink -f "$(dirname "$NAME")" )"
[ -d "$rc" ] || die "failed to determine rc directory"
cd "${HOME:?HOME variable empty or unset}" || die "failed to change directory"

backup_dir="$rc/backup-$(date -u '+%s')"
[ ! -d "$backup_dir" ] || die "backup directory already exists"

for f in .bashrc .zshrc .-shrc .prezto-compinit .ls_colors \
  .vimrc .inputrc .Xresources .screenrc .tmux.conf; do
    hardlink "$f" "$rc/home/${f#.}"
done

for d in sh .vim .mpv; do
    softlink "$d" "$rc/${d#.}"
done

# ensure that .bashrc gets executed
if [ ! -e .bash_profile ] || ! grep -qF .bashrc .bash_profile; then
    echo >> .bash_profile
    printf '%s\n' '[ ! -f ~/.bashrc ] || . ~/.bashrc' >> .bash_profile
fi

is_empty() {
    local f="${1:?is_empty requires an argument}"
    find "$f" -type f | while read -r f; do
        return 1
    done || return 1 # just in case pipes mess things up
    return 0
}

# delete any directory structure that may have been included with the OS.
# note that i'm careful not to delete them if they contain even a single file,
# but you might still want to remove this if you're adapting my install script.
for d in Desktop Documents Downloads Music Pictures Public Templates Video Videos; do
    [ -d "$d" ] || continue
    if is_empty "$d"; then
        rm -r "$d" # doesn't really matter if it fails
    else
        printf '%s\n' "not removing $d because it contains files"
    fi
done

# create instead my preferred directory structure.
mkdir -p opt/local/bin src work play