#!/usr/bin/env bash
set -euo pipefail

REPO_DIR="$(cd "$(dirname "$0")/.." && pwd)"
ISO_DIR="$REPO_DIR/iso"
DOWNLOAD_DIR="$REPO_DIR/download"
BASE_URL="https://cdimage.debian.org/debian-cd/current/amd64/iso-dvd"

# --- Subcommands ---

cmd_download() {
    mkdir -p "$DOWNLOAD_DIR"

    echo "Fetching SHA256SUMS..."
    local sums_file="$DOWNLOAD_DIR/SHA256SUMS"
    curl -fsSL -o "$sums_file" "$BASE_URL/SHA256SUMS"

    local iso_name expected_hash
    iso_name=$(grep 'debian-.*-amd64-DVD-1\.iso' "$sums_file" | awk '{print $2}')
    expected_hash=$(grep 'debian-.*-amd64-DVD-1\.iso' "$sums_file" | awk '{print $1}')

    if [[ -z "$iso_name" || -z "$expected_hash" ]]; then
        echo "Error: Could not find DVD-1 ISO in SHA256SUMS." >&2
        exit 1
    fi

    local iso_path="$DOWNLOAD_DIR/$iso_name"

    if [[ -f "$iso_path" ]]; then
        echo "ISO already exists, verifying checksum..."
        local actual_hash
        actual_hash=$(shasum -a 256 "$iso_path" | awk '{print $1}')
        if [[ "$actual_hash" == "$expected_hash" ]]; then
            echo "Checksum OK. Skipping download."
            echo "  $iso_path"
            return
        fi
        echo "Checksum mismatch, re-downloading..."
    fi

    echo "Downloading $iso_name..."
    curl -C - -fL -o "$iso_path" "$BASE_URL/$iso_name"

    echo "Verifying checksum..."
    local actual_hash
    actual_hash=$(shasum -a 256 "$iso_path" | awk '{print $1}')
    if [[ "$actual_hash" != "$expected_hash" ]]; then
        echo "Error: Checksum verification failed." >&2
        echo "  Expected: $expected_hash" >&2
        echo "  Got:      $actual_hash" >&2
        exit 1
    fi

    echo "Checksum OK."
    echo "  $iso_path"
}

cmd_build() {
    if ! command -v xorriso &>/dev/null; then
        echo "Error: xorriso not found." >&2
        echo "Install it with: brew install xorriso" >&2
        exit 1
    fi

    # Find source ISO
    local src_iso
    src_iso=$(find "$DOWNLOAD_DIR" -maxdepth 1 -name 'debian-*-amd64-DVD-1.iso' -print -quit 2>/dev/null || true)
    if [[ -z "$src_iso" || ! -f "$src_iso" ]]; then
        echo "Error: No Debian DVD-1 ISO found in $DOWNLOAD_DIR" >&2
        echo "Run 'yino-iso download' first." >&2
        exit 1
    fi
    echo "Source ISO: $src_iso"

    # Create temp working directory (not local — trap needs access after function returns)
    work_dir=$(mktemp -d "${TMPDIR:-/tmp}/yino-iso.XXXXXX")
    trap 'rm -rf "$work_dir"' EXIT

    local extract_dir="$work_dir/iso"

    # Extract ISO
    echo "Extracting ISO..."
    xorriso -osirrox on -indev "$src_iso" -extract / "$extract_dir"
    chmod -R u+w "$extract_dir"

    # Inject preseed into initrd
    echo "Injecting preseed into initrd..."
    gunzip "$extract_dir/install.amd/initrd.gz"
    (cd "$ISO_DIR" && echo preseed.cfg | cpio -o --format newc) >> "$extract_dir/install.amd/initrd"
    gzip "$extract_dir/install.amd/initrd"

    # Modify boot configs — add preseed boot parameters
    local boot_params="auto=true priority=critical locale=en_US.UTF-8 keymap=us console=ttyS0,115200n8"

    echo "Modifying boot configuration..."

    # Insert preseed params before the "---" separator in boot entries
    if [[ -f "$extract_dir/isolinux/txt.cfg" ]]; then
        sed -i.bak "s|--- |${boot_params} --- |" "$extract_dir/isolinux/txt.cfg"
        rm -f "$extract_dir/isolinux/txt.cfg.bak"
        # Set text installer as default boot entry (prepend with proper newline)
        { echo "default install"; cat "$extract_dir/isolinux/txt.cfg"; } > "$extract_dir/isolinux/txt.cfg.tmp"
        mv "$extract_dir/isolinux/txt.cfg.tmp" "$extract_dir/isolinux/txt.cfg"
    fi

    # Fix isolinux: enable serial console, disable graphical menu, set short timeout
    if [[ -f "$extract_dir/isolinux/isolinux.cfg" ]]; then
        # Prepend serial directive (BSD sed '1i' doesn't insert newlines reliably)
        { echo "serial 0 115200"; cat "$extract_dir/isolinux/isolinux.cfg"; } > "$extract_dir/isolinux/isolinux.cfg.tmp"
        mv "$extract_dir/isolinux/isolinux.cfg.tmp" "$extract_dir/isolinux/isolinux.cfg"
        sed -i.bak 's|^default vesamenu.c32|#default vesamenu.c32|' "$extract_dir/isolinux/isolinux.cfg"
        rm -f "$extract_dir/isolinux/isolinux.cfg.bak"
        sed -i.bak 's|^timeout .*|timeout 50|' "$extract_dir/isolinux/isolinux.cfg"
        rm -f "$extract_dir/isolinux/isolinux.cfg.bak"
    fi

    if [[ -f "$extract_dir/boot/grub/grub.cfg" ]]; then
        sed -i.bak "s|--- |${boot_params} --- |" "$extract_dir/boot/grub/grub.cfg"
        rm -f "$extract_dir/boot/grub/grub.cfg.bak"
        # Add serial console support to GRUB and select text "Install" entry (index 1)
        sed -i.bak 's|terminal_output gfxterm|terminal_output gfxterm serial|' "$extract_dir/boot/grub/grub.cfg"
        rm -f "$extract_dir/boot/grub/grub.cfg.bak"
        { printf 'serial --unit=0 --speed=115200\nterminal_input serial console\nterminal_output serial console\nset timeout=5\nset default=1\n'; cat "$extract_dir/boot/grub/grub.cfg"; } > "$extract_dir/boot/grub/grub.cfg.tmp"
        mv "$extract_dir/boot/grub/grub.cfg.tmp" "$extract_dir/boot/grub/grub.cfg"
    fi

    # Extract MBR template for hybrid boot
    echo "Extracting MBR template..."
    local mbr_template="$work_dir/isohdpfx.bin"
    dd if="$src_iso" bs=1 count=432 of="$mbr_template" 2>/dev/null

    # Regenerate checksums
    echo "Regenerating checksums..."
    (cd "$extract_dir" && find . -type f ! -name 'md5sum.txt' -exec md5sum {} + > md5sum.txt)

    # Rebuild ISO
    local output_iso="$DOWNLOAD_DIR/yino-$(date +%Y%m%d).iso"
    echo "Building ISO..."
    xorriso -as mkisofs \
        -r -V "Yino" \
        -o "$output_iso" \
        -J -joliet-long \
        -isohybrid-mbr "$mbr_template" \
        -partition_offset 16 \
        -b isolinux/isolinux.bin \
        -c isolinux/boot.cat \
        -no-emul-boot -boot-load-size 4 -boot-info-table \
        -eltorito-alt-boot \
        -e boot/grub/efi.img \
        -no-emul-boot \
        -isohybrid-gpt-basdat \
        "$extract_dir"

    echo "Done."
    echo "  $output_iso"
}

cmd_clean() {
    local yino_isos
    yino_isos=$(find "$DOWNLOAD_DIR" -maxdepth 1 -name 'yino-*.iso' 2>/dev/null || true)

    if [[ -z "$yino_isos" ]]; then
        echo "Nothing to clean."
        return
    fi

    echo "Removing built ISOs:"
    while read -r f; do
        echo "  $f"
        rm "$f"
    done <<< "$yino_isos"
}

cmd_help() {
    cat <<'EOF'
Usage: yino-iso <command>

Commands:
  download    Download Debian 13 DVD-1 ISO and verify checksum
  build       Build custom Yino ISO with preseed
  clean       Remove built ISOs
  help        Show this help

Dependencies (macOS):
  brew install xorriso
EOF
}

# --- Main ---

case "${1:-help}" in
    download) cmd_download ;;
    build)    cmd_build ;;
    clean)    cmd_clean ;;
    help|--help|-h) cmd_help ;;
    *)
        echo "Error: Unknown command: $1" >&2
        cmd_help >&2
        exit 1
        ;;
esac