/**
 * `wrnexus generate docker` — scaffold containerization for a WrNexus app:
 * a multi-stage Dockerfile (build with Bun → slim runtime), a .dockerignore,
 * and a docker-compose.yml (app + Postgres). Uses the app's `/healthz` endpoint
 * for the container health check.
 */

import { existsSync, writeFileSync } from "node:fs";
import { join, resolve } from "node:path";

const DOCKERFILE = `# syntax=docker/dockerfile:1
# --- build stage: install deps + produce dist/server.js ---
FROM oven/bun:1 AS build
WORKDIR /app
COPY package.json bun.lock* bun.lockb* ./
RUN bun install
COPY . .
RUN bun run build

# --- runtime stage: slim image with only the built server + migrations ---
FROM oven/bun:1-slim AS runtime
WORKDIR /app
ENV NODE_ENV=production
ENV PORT=3000
COPY --from=build /app/dist ./dist
COPY --from=build /app/app/db/migrations ./app/db/migrations
EXPOSE 3000
HEALTHCHECK --interval=30s --timeout=3s --retries=3 \\
  CMD bun -e "fetch('http://localhost:'+(process.env.PORT||3000)+'/healthz').then(r=>process.exit(r.ok?0:1)).catch(()=>process.exit(1))"
CMD ["bun", "dist/server.js"]
`;

const DOCKERIGNORE = `node_modules
dist
**/.wrnexus
.git
*.log
*.db
*.db-shm
*.db-wal
.DS_Store
`;

const COMPOSE = `services:
  app:
    build: .
    ports:
      - "3000:3000"
    environment:
      NODE_ENV: production
      PORT: "3000"
      DATABASE_URL: postgres://wrn:wrn@db:5432/app
    depends_on:
      db:
        condition: service_healthy
    restart: unless-stopped

  db:
    image: postgres:16-alpine
    environment:
      POSTGRES_USER: wrn
      POSTGRES_PASSWORD: wrn
      POSTGRES_DB: app
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U wrn -d app"]
      interval: 3s
      timeout: 3s
      retries: 20
    volumes:
      - pgdata:/var/lib/postgresql/data

volumes:
  pgdata:
`;

function writeIfAbsent(path: string, content: string, name: string): void {
  if (existsSync(path)) {
    console.warn(`  • ${name} already exists — skipped`);
    return;
  }
  writeFileSync(path, content, "utf8");
  console.log(`  ✓ ${name}`);
}

/** Scaffold Dockerfile, .dockerignore, and docker-compose.yml into `appRoot`. */
export function generateDocker(appRoot: string): void {
  const root = resolve(appRoot);
  console.log("Scaffolding containerization:");
  writeIfAbsent(join(root, "Dockerfile"), DOCKERFILE, "Dockerfile");
  writeIfAbsent(join(root, ".dockerignore"), DOCKERIGNORE, ".dockerignore");
  writeIfAbsent(join(root, "docker-compose.yml"), COMPOSE, "docker-compose.yml");
  console.log("\nBuild + run:  docker compose up --build");
}