#!/bin/bash

# BBeOS Kernel Build Script for MSM8960
# Builds Linux kernel for BlackBerry Classic Q20

set -e

SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
PROJECT_ROOT="$(dirname "$SCRIPT_DIR")"
KERNEL_DIR="$PROJECT_ROOT/vendor/kernel-source"
BUILD_DIR="$PROJECT_ROOT/build/kernel"
TOOLCHAIN_DIR="$PROJECT_ROOT/toolchain"

# Colors for output
RED='\033[0;31m'
GREEN='\033[0;32m'
YELLOW='\033[1;33m'
BLUE='\033[0;34m'
NC='\033[0m'

# Logging functions
log_info() {
    echo -e "${BLUE}[INFO]${NC} $1"
}

log_success() {
    echo -e "${GREEN}[SUCCESS]${NC} $1"
}

log_warning() {
    echo -e "${YELLOW}[WARNING]${NC} $1"
}

log_error() {
    echo -e "${RED}[ERROR]${NC} $1"
}

# Configuration
KERNEL_VERSION="6.1"
KERNEL_SOURCE="linux-$KERNEL_VERSION"
KERNEL_URL="https://cdn.kernel.org/pub/linux/kernel/v6.x/$KERNEL_SOURCE.tar.xz"
TOOLCHAIN_URL="https://developer.arm.com/-/media/Files/downloads/gnu-a/10.3-2021.07/binrel/gcc-arm-10.3-2021.07-x86_64-arm-none-linux-gnueabihf.tar.xz"
ARCH="arm"
CROSS_COMPILE="arm-none-linux-gnueabihf-"
DEFCONFIG="msm8960_defconfig"

# Check dependencies
check_dependencies() {
    log_info "Checking build dependencies..."
    
    local deps=("wget" "tar" "make" "gcc" "g++" "flex" "bison" "libssl-dev" "libncurses5-dev" "bc")
    local missing_deps=()
    
    for dep in "${deps[@]}"; do
        if ! command -v "$dep" &> /dev/null; then
            missing_deps+=("$dep")
        fi
    done
    
    if [ ${#missing_deps[@]} -ne 0 ]; then
        log_error "Missing dependencies: ${missing_deps[*]}"
        log_info "Please install the missing packages:"
        log_info "sudo apt-get install ${missing_deps[*]}"
        exit 1
    fi
    
    log_success "All dependencies found"
}

# Setup build environment
setup_build_env() {
    log_info "Setting up build environment..."
    
    mkdir -p "$BUILD_DIR"
    mkdir -p "$TOOLCHAIN_DIR"
    
    # Set environment variables
    export ARCH="$ARCH"
    export CROSS_COMPILE="$CROSS_COMPILE"
    export PATH="$TOOLCHAIN_DIR/gcc-arm-10.3-2021.07-x86_64-arm-none-linux-gnueabihf/bin:$PATH"
    
    log_success "Build environment configured"
}

# Download and setup toolchain
setup_toolchain() {
    log_info "Setting up ARM toolchain..."
    
    local toolchain_file="gcc-arm-10.3-2021.07-x86_64-arm-none-linux-gnueabihf.tar.xz"
    local toolchain_path="$TOOLCHAIN_DIR/$toolchain_file"
    
    if [ ! -d "$TOOLCHAIN_DIR/gcc-arm-10.3-2021.07-x86_64-arm-none-linux-gnueabihf" ]; then
        if [ ! -f "$toolchain_path" ]; then
            log_info "Downloading ARM toolchain..."
            wget -O "$toolchain_path" "$TOOLCHAIN_URL"
        fi
        
        log_info "Extracting toolchain..."
        tar -xf "$toolchain_path" -C "$TOOLCHAIN_DIR"
    fi
    
    log_success "Toolchain setup completed"
}

# Download kernel source
download_kernel() {
    log_info "Setting up kernel source..."
    
    local kernel_file="$KERNEL_SOURCE.tar.xz"
    local kernel_path="$BUILD_DIR/$kernel_file"
    
    if [ ! -d "$BUILD_DIR/$KERNEL_SOURCE" ]; then
        if [ ! -f "$kernel_path" ]; then
            log_info "Downloading kernel source..."
            wget -O "$kernel_path" "$KERNEL_URL"
        fi
        
        log_info "Extracting kernel source..."
        tar -xf "$kernel_path" -C "$BUILD_DIR"
    fi
    
    log_success "Kernel source setup completed"
}

# Apply patches and configuration
setup_kernel_config() {
    log_info "Setting up kernel configuration..."
    
    local kernel_build_dir="$BUILD_DIR/$KERNEL_SOURCE"
    
    # Copy our defconfig
    cp "$KERNEL_DIR/msm8960-defconfig" "$kernel_build_dir/arch/arm/configs/$DEFCONFIG"
    
    # Copy device tree
    cp "$KERNEL_DIR/q20.dts" "$kernel_build_dir/arch/arm/boot/dts/"
    
    # Apply any patches
    if [ -d "$KERNEL_DIR/patches" ]; then
        log_info "Applying kernel patches..."
        for patch in "$KERNEL_DIR/patches"/*.patch; do
            if [ -f "$patch" ]; then
                log_info "Applying patch: $(basename "$patch")"
                patch -d "$kernel_build_dir" -p1 < "$patch"
            fi
        done
    fi
    
    log_success "Kernel configuration setup completed"
}

# Build kernel
build_kernel() {
    log_info "Building kernel..."
    
    local kernel_build_dir="$BUILD_DIR/$KERNEL_SOURCE"
    cd "$kernel_build_dir"
    
    # Clean previous build
    make clean
    
    # Configure kernel
    make "$DEFCONFIG"
    
    # Build kernel
    make -j$(nproc) zImage dtbs modules
    
    # Build device tree blob
    dtc -I dts -O dtb -o "$BUILD_DIR/q20.dtb" "$KERNEL_DIR/q20.dts"
    
    log_success "Kernel build completed"
}

# Create boot image
create_boot_image() {
    log_info "Creating boot image..."
    
    local kernel_build_dir="$BUILD_DIR/$KERNEL_SOURCE"
    local boot_dir="$BUILD_DIR/boot"
    
    mkdir -p "$boot_dir"
    
    # Copy kernel image
    cp "$kernel_build_dir/arch/arm/boot/zImage" "$boot_dir/"
    
    # Copy device tree
    cp "$BUILD_DIR/q20.dtb" "$boot_dir/"
    
    # Create initramfs (minimal)
    create_initramfs
    
    # Create boot.img (Android format)
    create_android_boot_image
    
    log_success "Boot image created"
}

# Create minimal initramfs
create_initramfs() {
    log_info "Creating minimal initramfs..."
    
    local initramfs_dir="$BUILD_DIR/initramfs"
    local initramfs_file="$BUILD_DIR/initramfs.cpio.gz"
    
    mkdir -p "$initramfs_dir"
    
    # Create basic initramfs structure
    cat > "$initramfs_dir/init" << 'EOF'
#!/bin/sh
mount -t proc none /proc
mount -t sysfs none /sys
mount -t devtmpfs none /dev
exec /bin/sh
EOF
    
    chmod +x "$initramfs_dir/init"
    
    # Create initramfs archive
    cd "$initramfs_dir"
    find . | cpio -o -H newc | gzip > "$initramfs_file"
    
    log_success "Initramfs created"
}

# Create Android boot image
create_android_boot_image() {
    log_info "Creating Android boot image..."
    
    local boot_dir="$BUILD_DIR/boot"
    local boot_img="$BUILD_DIR/boot.img"
    
    # This is a placeholder - you'd need mkbootimg tool
    log_warning "Android boot image creation requires mkbootimg tool"
    log_info "Manual steps required:"
    log_info "1. Install mkbootimg tool"
    log_info "2. Run: mkbootimg --kernel $boot_dir/zImage --dtb $boot_dir/q20.dtb --ramdisk $BUILD_DIR/initramfs.cpio.gz --output $boot_img"
}

# Main build process
main() {
    log_info "Starting BBeOS kernel build for MSM8960..."
    
    check_dependencies
    setup_build_env
    setup_toolchain
    download_kernel
    setup_kernel_config
    build_kernel
    create_boot_image
    
    log_success "Kernel build completed successfully!"
    log_info "Build artifacts:"
    log_info "  Kernel: $BUILD_DIR/$KERNEL_SOURCE/arch/arm/boot/zImage"
    log_info "  Device Tree: $BUILD_DIR/q20.dtb"
    log_info "  Initramfs: $BUILD_DIR/initramfs.cpio.gz"
    log_info "  Boot Directory: $BUILD_DIR/boot/"
}

# Run main function
main "$@"