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

REPO_SLUG="${DOTFILES_REPO:-KAJdev/dotfiles}"
BRANCH="${DOTFILES_BRANCH:-main}"
SOURCE_OVERRIDE="${DOTFILES_SOURCE:-}"
BACKUP_BASE="${DOTFILES_BACKUP_DIR:-$HOME/.dotfiles-backups}"
INSTALL_PI=1
INSTALL_NVIM=1
DRY_RUN=0
TEMP_DIR=""
BACKUP_CREATED=0
TIMESTAMP="$(date +%Y%m%d-%H%M%S)"
BACKUP_DIR="$BACKUP_BASE/$TIMESTAMP"
if [[ -e "$BACKUP_DIR" ]]; then BACKUP_DIR="${BACKUP_DIR}-$$"; fi

if [[ -t 1 ]]; then
	BOLD=$'\033[1m'
	DIM=$'\033[2m'
	GREEN=$'\033[32m'
	YELLOW=$'\033[33m'
	RESET=$'\033[0m'
else
	BOLD=""
	DIM=""
	GREEN=""
	YELLOW=""
	RESET=""
fi

log() { printf '%s\n' "${BOLD}==>${RESET} $*" >&2; }
ok() { printf '%s\n' "${GREEN}  ✓${RESET} $*"; }
warn() { printf '%s\n' "${YELLOW}  !${RESET} $*" >&2; }
die() { printf 'error: %s\n' "$*" >&2; exit 1; }

usage() {
	cat <<'EOF'
Usage: install.sh [options]

Options:
  --pi-only       Install only Pi configuration
  --nvim-only     Install only Neovim configuration
  --no-pi         Skip Pi configuration
  --no-nvim       Skip Neovim configuration
  --source PATH   Install from an existing checkout
  --dry-run       Show changes without writing files
  -h, --help      Show this help

Environment:
  DOTFILES_SOURCE, DOTFILES_REPO, DOTFILES_BRANCH,
  DOTFILES_BACKUP_DIR, PI_AGENT_DIR, NVIM_CONFIG_DIR
EOF
}

while (($# > 0)); do
	case "$1" in
		--pi-only) INSTALL_PI=1; INSTALL_NVIM=0 ;;
		--nvim-only) INSTALL_PI=0; INSTALL_NVIM=1 ;;
		--no-pi) INSTALL_PI=0 ;;
		--no-nvim) INSTALL_NVIM=0 ;;
		--source)
			(($# >= 2)) || die "--source requires a path"
			SOURCE_OVERRIDE="$2"
			shift
			;;
		--dry-run) DRY_RUN=1 ;;
		-h|--help) usage; exit 0 ;;
		*) die "unknown option: $1" ;;
	esac
	shift
done

((INSTALL_PI || INSTALL_NVIM)) || die "nothing selected to install"

cleanup() {
	if [[ -n "$TEMP_DIR" && -d "$TEMP_DIR" ]]; then
		rm -rf "$TEMP_DIR"
	fi
}
trap cleanup EXIT

absolute_dir() {
	(cd "$1" 2>/dev/null && pwd -P)
}

find_local_source() {
	local candidate=""
	if [[ -n "$SOURCE_OVERRIDE" ]]; then
		candidate="$SOURCE_OVERRIDE"
	elif [[ -n "${BASH_SOURCE[0]:-}" && -f "${BASH_SOURCE[0]}" ]]; then
		candidate="$(dirname "${BASH_SOURCE[0]}")"
	fi

	if [[ -n "$candidate" && -f "$candidate/pi/settings.json" && -f "$candidate/nvim/init.lua" ]]; then
		absolute_dir "$candidate"
		return 0
	fi
	return 1
}

download_source() {
	TEMP_DIR="$(mktemp -d 2>/dev/null || mktemp -d -t dotfiles)"
	if command -v git >/dev/null 2>&1; then
		log "Downloading $REPO_SLUG@$BRANCH with git"
		git clone --quiet --depth 1 --branch "$BRANCH" "https://github.com/$REPO_SLUG.git" "$TEMP_DIR/repo"
		SOURCE_DIR="$TEMP_DIR/repo"
		return
	fi

	command -v curl >/dev/null 2>&1 || die "git or curl is required"
	command -v tar >/dev/null 2>&1 || die "tar is required when git is unavailable"
	log "Downloading $REPO_SLUG@$BRANCH archive"
	curl -fsSL "https://github.com/$REPO_SLUG/archive/refs/heads/$BRANCH.tar.gz" -o "$TEMP_DIR/repo.tar.gz"
	mkdir -p "$TEMP_DIR/archive"
	tar -xzf "$TEMP_DIR/repo.tar.gz" -C "$TEMP_DIR/archive"
	local candidate
	for candidate in "$TEMP_DIR"/archive/*; do
		if [[ -d "$candidate" && -f "$candidate/pi/settings.json" ]]; then
			SOURCE_DIR="$candidate"
			return
		fi
	done
	die "downloaded archive did not contain the expected files"
}

resolve_nvim_dir() {
	if [[ -n "${NVIM_CONFIG_DIR:-}" ]]; then
		printf '%s\n' "$NVIM_CONFIG_DIR"
		return
	fi

	case "$(uname -s 2>/dev/null || printf unknown)" in
		MINGW*|MSYS*|CYGWIN*)
			if [[ -n "${LOCALAPPDATA:-}" ]]; then
				if command -v cygpath >/dev/null 2>&1; then
					printf '%s/nvim\n' "$(cygpath -u "$LOCALAPPDATA")"
				else
					printf '%s/nvim\n' "$LOCALAPPDATA"
				fi
				return
			fi
			;;
	esac
	printf '%s/nvim\n' "${XDG_CONFIG_HOME:-$HOME/.config}"
}

ensure_backup_dir() {
	if ((BACKUP_CREATED)); then return; fi
	if ((DRY_RUN)); then
		warn "would create backup directory $BACKUP_DIR"
	else
		mkdir -p "$BACKUP_DIR"
	fi
	BACKUP_CREATED=1
}

backup_item() {
	local path="$1" label="$2" target="$BACKUP_DIR/$label"
	ensure_backup_dir
	if ((DRY_RUN)); then
		warn "would back up $path -> $target"
		return
	fi
	mkdir -p "$(dirname "$target")"
	mv "$path" "$target"
	ok "Backed up $path"
}

install_file() {
	local source="$1" destination="$2" label="$3"
	[[ -f "$source" ]] || die "missing source file: $source"

	if [[ -f "$destination" ]] && cmp -s "$source" "$destination"; then
		ok "Unchanged $destination"
		return
	fi
	if [[ -e "$destination" || -L "$destination" ]]; then
		backup_item "$destination" "$label"
	fi
	if ((DRY_RUN)); then
		log "Would install $destination"
		return
	fi
	mkdir -p "$(dirname "$destination")"
	cp -p "$source" "$destination"
	ok "Installed $destination"
}

directories_equal() {
	[[ -d "$1" && -d "$2" ]] || return 1
	command -v diff >/dev/null 2>&1 || return 1
	diff -qr "$1" "$2" >/dev/null 2>&1
}

install_directory() {
	local source="$1" destination="$2" label="$3"
	[[ -d "$source" ]] || die "missing source directory: $source"

	if directories_equal "$source" "$destination"; then
		ok "Unchanged $destination"
		return
	fi
	if [[ -e "$destination" || -L "$destination" ]]; then
		backup_item "$destination" "$label"
	fi
	if ((DRY_RUN)); then
		log "Would install $destination"
		return
	fi
	mkdir -p "$(dirname "$destination")"
	cp -R "$source" "$destination"
	ok "Installed $destination"
}

SOURCE_DIR=""
if LOCAL_SOURCE="$(find_local_source)"; then
	SOURCE_DIR="$LOCAL_SOURCE"
else
	download_source
fi
[[ -f "$SOURCE_DIR/pi/settings.json" ]] || die "invalid source directory: $SOURCE_DIR"

log "Installing KAJdev dotfiles"
printf '%s\n' "${DIM}source: $SOURCE_DIR${RESET}"

if ((INSTALL_PI)); then
	PI_DIR="${PI_AGENT_DIR:-$HOME/.pi/agent}"
	log "Pi configuration"
	install_file "$SOURCE_DIR/pi/settings.json" "$PI_DIR/settings.json" "pi/settings.json"
	install_file "$SOURCE_DIR/pi/models.json" "$PI_DIR/models.json" "pi/models.json"
	install_directory "$SOURCE_DIR/pi/extensions" "$PI_DIR/extensions" "pi/extensions"
	install_directory "$SOURCE_DIR/pi/themes" "$PI_DIR/themes" "pi/themes"
fi

if ((INSTALL_NVIM)); then
	NVIM_DIR="$(resolve_nvim_dir)"
	log "Neovim configuration"
	install_directory "$SOURCE_DIR/nvim" "$NVIM_DIR" "nvim"
fi

if ((DRY_RUN)); then
	log "Dry run complete; nothing was changed"
else
	log "Installation complete"
	if ((BACKUP_CREATED)); then
		printf 'Backups: %s\n' "$BACKUP_DIR"
	fi
	if ((INSTALL_PI)); then
		printf '%s\n' "Run /reload in an existing pi session."
	fi
	if ((INSTALL_NVIM)) && ! command -v nvim >/dev/null 2>&1; then
		warn "Neovim is not installed; configuration is ready for when it is installed."
	fi
fi