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

usage() {
    cat <<'EOF'
Quicksh arch 0.1.0 — Arch Linux developer essentials
Usage: bash arch.sh [--help|-h|--version|--packages|--install]

Default: report OS, kernel, architecture, pacman, and basic developer tools.
--packages  List the recommended packages without making changes.
--install   Preview pacman -S --needed, then require a terminal and typed yes.

Packages: base-devel git bash curl ca-certificates
Only genuine Arch Linux (ID=arch) is supported, not derivatives.
Installation may install dependencies and update requested packages. pacman
shows its transaction and asks for confirmation too. No database refresh,
full upgrade, package removal, or unattended confirmation is performed here.
EOF
}

install_packages() {
    local -a packages=(base-devel git bash curl ca-certificates)
    local -a elevate=()
    if (( EUID != 0 )); then
        if ! command -v sudo >/dev/null 2>&1; then
            printf 'quicksh arch: sudo is required for --install as a non-root user.\n' >&2
            return 1
        fi
        elevate=(sudo --)
    fi
    printf '\nProposed command:\n  '
    printf '%s ' "${elevate[@]}" pacman -S --needed "${packages[@]}"
    printf '\nThis installs essentials and dependencies, and may update requested packages.\n'
    printf 'Package databases are NOT refreshed; no full system upgrade is run.\n'
    printf 'On a stale system, cancel and review a full pacman -Syu separately first.\n'
    printf 'Do not work around stale databases by running pacman -Sy alone.\n'
    if [[ ! -t 0 || ! -t 1 ]]; then
        printf 'quicksh arch: --install requires interactive stdin and stdout; no changes made.\n' >&2
        return 1
    fi
    local answer
    printf 'Proceed to the pacman transaction? Type yes to continue: '
    if ! IFS= read -r answer; then
        printf '\nquicksh arch: confirmation could not be read; no changes made.\n' >&2
        return 1
    fi
    if [[ "$answer" != yes ]]; then
        printf 'Cancelled; no changes made.\n'
        return 0
    fi
    if ! "${elevate[@]}" pacman -S --needed "${packages[@]}"; then
        printf 'quicksh arch: pacman failed or was cancelled. Review its output; no automatic retry.\n' >&2
        return 1
    fi
    printf 'Package command completed.\n'
}

main() {
    if (( $# > 1 )); then
        printf 'quicksh arch: expected at most one option. Use --help.\n' >&2
        return 2
    fi
    case "${1:-}" in
        --help|-h) usage; return ;;
        --version) printf 'Quicksh arch 0.1.0\n'; return ;;
        ''|--packages|--install) ;;
        *) printf 'quicksh arch: unsupported option: %s. Use --help.\n' "$1" >&2; return 2 ;;
    esac
    local ID=unknown PRETTY_NAME='Unknown system'
    if [[ ! -r /etc/os-release ]]; then
        printf 'quicksh arch: cannot identify the OS; expected /etc/os-release.\n' >&2
        return 1
    fi
    # shellcheck disable=SC1091
    if ! . /etc/os-release; then
        printf 'quicksh arch: could not read OS identification.\n' >&2
        return 1
    fi
    if [[ "$ID" != arch ]]; then
        printf 'quicksh arch: unsupported OS: %s. Requires ID=arch; no changes made.\n' "$ID" >&2
        return 1
    fi
    printf 'Quicksh arch 0.1.0\nOS: %s\n' "$PRETTY_NAME"
    if [[ "${1:-}" == --packages ]]; then
        printf 'Recommended: base-devel git bash curl ca-certificates\n'
        printf 'Compiler/build tools, Git, Bash, HTTPS downloads, and trusted CA certificates.\n'
        printf 'Review --install to opt in; listing packages makes no changes.\n'
        return 0
    fi
    if ! command -v pacman >/dev/null 2>&1; then
        printf 'quicksh arch: pacman is not available in PATH.\n' >&2
        return 1
    fi
    if [[ "${1:-}" == --install ]]; then
        install_packages
        return
    fi
    local system tool
    if ! system=$(uname -srmo); then
        printf 'quicksh arch: could not read kernel and architecture information.\n' >&2
        return 1
    fi
    printf 'System: %s\n\nTool availability:\n' "$system"
    for tool in pacman git bash curl make cc; do
        if command -v "$tool" >/dev/null 2>&1; then
            printf '  [ok]      %s\n' "$tool"
        else
            printf '  [missing] %s\n' "$tool"
        fi
    done
    printf '\nUse --packages for recommendations or --install for an interactive opt-in.\n'
}

main "$@"