# Multi-stage Alpine Zero-OS Builder with Smart Caching
# Stage 1: Base build environment (cached until Alpine version changes)
FROM alpine:3.22 AS base-builder

# Install build dependencies (expensive, cache this layer)
RUN apk add --no-cache \
    # Build tools
    build-base \
    linux-headers \
    cmake \
    git \
    wget \
    curl \
    cpio \
    xz \
    gzip \
    bc \
    perl \
    python3 \
    # Kernel build dependencies
    linux-lts-dev \
    linux-lts \
    elfutils-dev \
    openssl-dev \
    flex \
    bison \
    # Archive tools
    tar \
    bzip2 \
    unzip \
    # Text processing
    sed \
    grep \
    findutils \
    jq \
    diffutils \
    # Go for source compilation
    go \
    # Rustup for proper Rust musl builds
    rustup

# Setup Rust toolchain for musl builds
RUN rustup-init -y --default-toolchain stable && \
    . ~/.cargo/env && \
    rustup target add x86_64-unknown-linux-musl

# Create standard directories
RUN mkdir -p /build/initramfs /build/kernel /build/output /build/github /build/configs/zinit /mnt/zinit /build/source /build/cache

WORKDIR /build

# Stage 2: Zero-OS components (cached until source repos change)
FROM base-builder AS components-builder

# Copy component compilation script
COPY scripts/compile-components.sh /build/scripts/
RUN chmod +x /build/scripts/compile-components.sh

# Create a marker file to track component compilation
RUN echo "$(date)" > /build/components-build-time

# This stage will be cached unless we explicitly rebuild components

# Stage 3: Kernel builder (cached until kernel version/config changes)  
FROM components-builder AS kernel-builder

# Copy kernel configuration and version
COPY configs/kernel-version /build/configs/
COPY configs/kernel-config-generic /build/configs/
COPY scripts/build-kernel.sh /build/scripts/
RUN chmod +x /build/scripts/build-kernel.sh

# Create kernel build marker
RUN echo "Kernel: $(cat /build/configs/kernel-version)" > /build/kernel-build-marker

# This stage caches kernel source download and basic setup

# Stage 4: Final builder (lightweight layer for initramfs assembly)
FROM kernel-builder AS final-builder

# Copy all scripts and configs
COPY scripts/ /build/scripts/
COPY configs/ /build/configs/

# Make all scripts executable
RUN chmod +x /build/scripts/*.sh

# Set build arguments
ARG TARGETARCH=amd64
ARG BUILDMODE=debug
ARG MINIMAL_MODE=false

# Set environment variables
ENV BUILDMODE=${BUILDMODE}
ENV TARGETARCH=${TARGETARCH}
ENV MINIMAL_MODE=${MINIMAL_MODE}

# Create build configuration
RUN echo "BUILDMODE=${BUILDMODE}" > /build/build.conf && \
    echo "TARGETARCH=${TARGETARCH}" >> /build/build.conf && \
    echo "MINIMAL_MODE=${MINIMAL_MODE}" >> /build/build.conf && \
    echo "INITRAMFS_ROOT=/build/initramfs" >> /build/build.conf && \
    echo "KERNEL_DIR=/build/kernel" >> /build/build.conf && \
    echo "OUTPUT_DIR=/build/output" >> /build/build.conf && \
    echo "CONFIG_DIR=/build/configs" >> /build/build.conf

# Default command
CMD ["/build/scripts/build-initramfs.sh"]