FROM --platform=linux/amd64 debian:bookworm-slim

# ============================================================
# Layer 1: System dependencies (cached unless packages change)
# ============================================================
RUN apt-get update && apt-get install -y --no-install-recommends \
    curl git unzip xz-utils zip python3 python3-venv wget \
    libgtk-3-dev ninja-build libglu1-mesa \
    && rm -rf /var/lib/apt/lists/* \
    && apt-get clean

# ============================================================
# Layer 2: Non-root user (cached)
# ============================================================
ARG USERNAME=vscode
ARG USER_UID=1000
ARG USER_GID=1000
RUN groupadd --gid $USER_GID $USERNAME \
 && useradd --uid $USER_UID --gid $USER_GID -m -s /bin/bash $USERNAME

# ============================================================
# Layer 3: Flutter SDK (tarball — ~150MB vs 500MB+ git clone)
# Uses pre-built release tarball instead of cloning the repo.
# This alone saves 10-15 minutes on first build.
# ============================================================
ENV FLUTTER_VERSION=3.41.8
ENV FLUTTER_HOME=/opt/flutter
ENV PATH="$FLUTTER_HOME/bin:$PATH"

# Download pre-built Flutter SDK tarball (much faster than git clone)
RUN curl -fsSL "https://storage.googleapis.com/download.flutter.io/flutter_linux_${FLUTTER_VERSION}-stable.tar.xz" \
    -o /tmp/flutter.tar.xz \
    && tar -xf /tmp/flutter.tar.xz -C /opt \
    && rm /tmp/flutter.tar.xz \
    && flutter precache --android --ios \
    && chown -R $USER_UID:$USER_GID $FLUTTER_HOME

# ============================================================
# Layer 4: Android SDK (only what's needed for Flutter builds)
# Parallel downloads where possible, minimal packages.
# ============================================================
ENV ANDROID_HOME=/opt/android-sdk
ENV PATH="$PATH:$ANDROID_HOME/cmdline-tools/latest/bin:$ANDROID_HOME/platform-tools"

RUN curl -fsSL "https://dl.google.com/android/repository/commandlinetools-linux-13114758_latest.zip" \
    -o /tmp/cmdline-tools.zip \
    && mkdir -p $ANDROID_HOME/cmdline-tools \
    && unzip -q /tmp/cmdline-tools.zip -d $ANDROID_HOME/cmdline-tools \
    && mv $ANDROID_HOME/cmdline-tools/cmdline-tools $ANDROID_HOME/cmdline-tools/latest \
    && rm /tmp/cmdline-tools.zip \
    # Accept licenses + install ONLY the packages Flutter needs
    && yes | sdkmanager --licenses \
    && sdkmanager \
        "platform-tools" \
        "platforms;android-36" \
        "build-tools;36.0.0" \
    && rm -rf "$ANDROID_HOME/.android" \
    && chown -R $USER_UID:$USER_GID $ANDROID_HOME

# ============================================================
# Layer 5: Java (only needed for Android builds)
# Use JRE instead of JDK — smaller footprint.
# ============================================================
RUN apt-get update && apt-get install -y --no-install-recommends \
    openjdk-17-jre-headless \
    && rm -rf /var/lib/apt/lists/* \
    && apt-get clean

USER $USERNAME
ENV HOME=/home/$USERNAME