#!/usr/bin/env bash
# ==========================================================
# install-docker.sh
# Install latest Docker Engine + Docker Compose plugin on
# Ubuntu (20.04 / 22.04 / 24.04). Follows the official
# Docker install guide at:
#   https://docs.docker.com/engine/install/ubuntu/
#
# Run:
#   sudo bash scripts/install-docker.sh
# ==========================================================
set -euo pipefail

# -- Color helpers
info()  { printf "\033[34m[INFO]\033[0m  %s\n" "$*"; }
ok()    { printf "\033[32m[OK]\033[0m    %s\n" "$*"; }
warn()  { printf "\033[33m[WARN]\033[0m  %s\n" "$*"; }
err()   { printf "\033[31m[ERROR]\033[0m %s\n" "$*"; }

# -- Must run as root
if [[ $EUID -ne 0 ]]; then
    err "This script must be run as root (use sudo)."
    exit 1
fi

# -- Must be Ubuntu
if ! grep -qi 'ubuntu' /etc/os-release 2>/dev/null; then
    err "This script only supports Ubuntu. Detected:"
    cat /etc/os-release 2>/dev/null || echo "(unknown)"
    exit 1
fi

# ==========================================================
# 1. Uninstall old, potentially-conflicting packages
# ==========================================================
info "Removing old Docker packages (it's fine if none were installed)…"
for pkg in docker.io docker-doc docker-compose docker-compose-v2 \
           podman-docker containerd runc; do
    if dpkg -s "$pkg" &>/dev/null; then
        apt-get remove -y "$pkg"
    fi
done
ok "Old packages removed."

# ==========================================================
# 2. Install prerequisites
# ==========================================================
info "Installing prerequisites…"
apt-get update -qq
apt-get install -y -qq ca-certificates curl
ok "Prerequisites installed."

# ==========================================================
# 3. Add Docker's official GPG key
# ==========================================================
info "Adding Docker GPG key…"
install -m 0755 -d /etc/apt/keyrings
curl -fsSL https://download.docker.com/linux/ubuntu/gpg \
    -o /etc/apt/keyrings/docker.asc
chmod a+r /etc/apt/keyrings/docker.asc
ok "GPG key added."

# ==========================================================
# 4. Add Docker apt repository
# ==========================================================
info "Adding Docker apt repository…"
# Derive codename from /etc/os-release (e.g. noble, jammy, focal)
. /etc/os-release
echo \
  "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.asc] \
  https://download.docker.com/linux/ubuntu ${VERSION_CODENAME} stable" \
  | tee /etc/apt/sources.list.d/docker.list > /dev/null
apt-get update -qq
ok "Docker repository added."

# ==========================================================
# 5. Install Docker Engine + CLI + containerd + Compose plugin
# ==========================================================
info "Installing Docker Engine, CLI, containerd, and Compose plugin…"
apt-get install -y -qq docker-ce docker-ce-cli containerd.io \
    docker-buildx-plugin docker-compose-plugin
ok "Docker packages installed."

# ==========================================================
# 6. Optional: add current non-root user to docker group
# ==========================================================
if [[ -n "${SUDO_USER:-}" ]]; then
    info "Adding user '$SUDO_USER' to the docker group…"
    usermod -aG docker "$SUDO_USER"
    ok "User '$SUDO_USER' added to docker group."
    warn "Log out and back in (or run 'newgrp docker') for group change to take effect."
fi

# ==========================================================
# 7. Verify installation
# ==========================================================
info "Verifying installation…"
docker --version
docker compose version

# Start & enable Docker daemon
systemctl enable docker --now 2>/dev/null || true

# Quick smoke test
if docker run --rm hello-world &>/dev/null; then
    ok "Docker is working — hello-world ran successfully."
else
    warn "hello-world check skipped (no network or daemon not ready)."
fi

ok "Installation complete!"