# Build stage
FROM golang:1.21-alpine AS builder

WORKDIR /app

COPY go.mod go.sum ./
RUN go mod download

COPY main.go ./
RUN CGO_ENABLED=0 GOOS=linux go build -ldflags="-s -w" -o nats-ui main.go

# Runtime stage
FROM alpine:3.19

RUN apk --no-cache add ca-certificates tzdata && \
    adduser -D -u 1000 -h /app appuser

WORKDIR /app

COPY --from=builder /app/nats-ui .
COPY index.html ./

# config.yaml is in .gitignore; create default in image (override via volume at runtime)
RUN printf '%s\n' \
    'nats_url: "nats://localhost:4222"' \
    'subjects: ">"' \
    'port: "8080"' \
    'max_messages: 1000' \
    > config.yaml

RUN chmod +x nats-ui && chown -R appuser:appuser /app

EXPOSE 8080

USER appuser

ENTRYPOINT ["./nats-ui"]
CMD ["config.yaml"]