#!/bin/sh

# Installation script to make the dotfiles available in ~/
#
# `git` is the only dependency for this script to run (See: https://git-scm.com)
#
# See: https://code.webartifex.de/alexander/dotfiles#installation


set -eu


XDG_BIN_HOME="${XDG_BIN_HOME:-$HOME/.local/bin}"
XDG_DATA_HOME="${XDG_DATA_HOME:-$HOME/.local/share}"
XDG_STATE_HOME="${XDG_STATE_HOME:-$HOME/.local/state}"

# Each branch's first commit sets the default to its own name
# => Overridable via the environment (e.g., done by `dotfiles-update`)
DOTFILES_BRANCH="${DOTFILES_BRANCH:-main}"

DOTFILES_DIR="${DOTFILES_DIR:-$XDG_DATA_HOME/dotfiles}"
DOTFILES_HTTPS="${DOTFILES_HTTPS:-https://code.webartifex.de/alexander/dotfiles}"

BACKUPS_DIR="$XDG_STATE_HOME/dotfiles-backups"
BACKUP_DIR="$BACKUPS_DIR/$(date +%Y%m%d-%H%M%S)"


_force=0

if [ "$#" -gt 1 ]; then
    echo "Usage: $(basename "$0") [--force]" >&2
    exit 1
fi

case "${1:-}" in
    "")      ;;
    --force) _force=1 ;;
    *)
        echo "Usage: $(basename "$0") [--force]" >&2
        exit 1
        ;;
esac


if [ -d "$DOTFILES_DIR" ]; then

    if [ "$_force" -ne 1 ]; then

        echo ""
        echo "The dotfiles are already installed at: $DOTFILES_DIR"
        echo ""
        echo "Options:"
        echo "  - Run the installation again with '--force'"
        echo "  - Update with 'dotfiles pull' and continue using them"
        echo ""

        exit 0

    fi

    echo "Backing up the existing repository to: $BACKUP_DIR"
    mkdir -p "$BACKUP_DIR"
    mv "$DOTFILES_DIR" "$BACKUP_DIR/dotfiles"

fi


git clone --bare "$DOTFILES_HTTPS" "$DOTFILES_DIR"


_git() {
    git --git-dir="$DOTFILES_DIR" --work-tree="$HOME" "$@"
}


if ! _git show-ref --verify --quiet "refs/heads/$DOTFILES_BRANCH"; then

    echo "" >&2
    echo "Internal error: branch '$DOTFILES_BRANCH' missing in the repository" >&2
    echo "" >&2
    echo "Available branches:" >&2
    _git branch --format='  %(refname:short)' >&2
    echo "" >&2

    exit 1

fi


_git config remote.origin.fetch '+refs/heads/*:refs/remotes/origin/*'
_git fetch origin


# Do not checkout project documentation intended for web GUIs
#
# Note: The patterns match at every depth, like in a .gitignore,
#       which excludes the per-folder README.md files as well
_git config core.sparseCheckout true
{
    echo "/*"
    echo "!LICENSE.txt"
    echo "!README.md"
    echo "!.ssh"
} > "$DOTFILES_DIR/info/sparse-checkout"


# Back up files in the user's $HOME folder if a checkout is about to overwrite them
#
# Note: This may also back up local-only files marked sparse in the repo,
#       which is not considered a big problem because it's very unlikely
_conflicts=$(_git ls-tree -r --name-only "$DOTFILES_BRANCH" | while IFS= read -r f; do
    if [ -e "$HOME/$f" ] || [ -L "$HOME/$f" ]; then echo "$f"; fi
done)

if [ -n "$_conflicts" ]; then

    echo "Backing up pre-existing files to: $BACKUP_DIR"
    echo "$_conflicts" | while IFS= read -r f; do
        mkdir -p "$BACKUP_DIR/$(dirname "$f")"
        cp -a "$HOME/$f" "$BACKUP_DIR/$f"
    done

fi

# Put the dotfiles in the user's $HOME folder
_git checkout --force "$DOTFILES_BRANCH"

# Do not show files not tracked in the dotfiles repository because there are simply too many
_git config --local status.showUntrackedFiles no


if command -v batcat >/dev/null 2>&1 && ! command -v bat >/dev/null 2>&1; then
    ln -sf "$(command -v batcat)" "$XDG_BIN_HOME/bat"
fi


sh "$XDG_BIN_HOME/generate-shell-completions" --quieter \
    || echo "WARN: generating shell completions failed" >&2


# Keep only the most recent backups
_keep=10
if [ -d "$BACKUPS_DIR" ]; then
    # `head -n -N` is a GNU extension; fine on Debian, fails on, e.g., BSD/BusyBox
    find "$BACKUPS_DIR" -mindepth 1 -maxdepth 1 -type d | sort | head -n -"$_keep" \
        | while IFS= read -r _old; do
            rm -f -r "$_old"
        done
fi


echo ""
echo "The dotfiles were installed successfully (branch: $DOTFILES_BRANCH)"
echo ""
echo "Reload your shell to use them:"
echo "    exec \$SHELL -l"
echo ""