#!/bin/bash
# 用法: ./extract_firmware.sh <merged_bin> [output_dir]
# 从合并的 bin 文件中提取 head file (firmware), tail file (IUM), 以及生成 metadata.json
#
# 文件布局:
#   0x04000: firmware (head file)
#   0x1dc00: IUM (tail file, 256 bytes)
#   0x1dd00: metadata (blocks: uint16, last_block_size: uint8)

INPUT="$1"
OUTPUT_DIR="${2:-.}"

if [ -z "$INPUT" ]; then
    echo "用法: $0 <merged_bin> [output_dir]"
    echo "示例: $0 40_ufcs2.bin /tmp/output"
    echo "       $0 40_ufcs2.bin          # 输出到当前目录"
    echo ""
    echo "输出文件:"
    echo "  firmware.bin    - firmware 部分"
    echo "  ium.bin         - IUM 部分 (256 bytes)"
    echo "  metadata.json   - 元数据"
    exit 1
fi

if [ ! -f "$INPUT" ]; then
    echo "错误: 文件不存在: $INPUT"
    exit 1
fi

# 创建输出目录（如果不存在）
mkdir -p "$OUTPUT_DIR"

# 常量定义
FIRMWARE_OFFSET=$((0x4000))   # 16384
IUM_OFFSET=$((0x1dc00))       # 121856
METADATA_OFFSET=$((0x1dd00))  # 122112
IUM_SIZE=256

# 获取文件大小
if stat --version >/dev/null 2>&1; then
    FILE_SIZE=$(stat -c%s "$INPUT")   # Linux
else
    FILE_SIZE=$(stat -f%z "$INPUT")   # macOS
fi

echo "输入文件: $INPUT"
echo "文件大小: $FILE_SIZE bytes (0x$(printf '%x' $FILE_SIZE))"
echo ""

# 读取 metadata (位于 0x1dd00)
# 结构: uint16_t blocks (little-endian), uint8_t last_block_size
echo "读取 metadata (offset 0x1dd00)..."

METADATA=$(dd if="$INPUT" bs=1 skip=$METADATA_OFFSET count=3 2>/dev/null | xxd -p)

if [ ${#METADATA} -lt 6 ]; then
    echo "错误: 无法读取 metadata"
    exit 1
fi

# 解析 little-endian uint16 (blocks) 和 uint8 (last_block_size)
BLOCKS_LOW=$((16#${METADATA:0:2}))
BLOCKS_HIGH=$((16#${METADATA:2:2}))
BLOCKS=$(( BLOCKS_LOW + BLOCKS_HIGH * 256 ))
LAST_BLOCK_SIZE=$((16#${METADATA:4:2}))

echo "  blocks: $BLOCKS (0x$(printf '%04x' $BLOCKS))"
echo "  last_block_size: $LAST_BLOCK_SIZE (0x$(printf '%02x' $LAST_BLOCK_SIZE))"

# 计算 firmware 大小
FIRMWARE_SIZE=$(( BLOCKS * 256 + LAST_BLOCK_SIZE ))
echo "  计算出 firmware 大小: $FIRMWARE_SIZE bytes"
echo ""

# 提取 head file (firmware: 从 0x4000 开始)
HEAD_FILE="$OUTPUT_DIR/firmware.bin"
echo "提取 head file (firmware)..."
dd if="$INPUT" of="$HEAD_FILE" bs=1 skip=$FIRMWARE_OFFSET count=$FIRMWARE_SIZE status=none

if [ $? -eq 0 ]; then
    ACTUAL_HEAD_SIZE=$(stat -f%z "$HEAD_FILE" 2>/dev/null || stat -c%s "$HEAD_FILE" 2>/dev/null)
    echo "  ✓ 已保存: $HEAD_FILE ($ACTUAL_HEAD_SIZE bytes)"
else
    echo "  ✗ 提取失败"
    exit 1
fi

# 提取 tail file (IUM: 从 0x1dc00 开始, 256 bytes)
TAIL_FILE="$OUTPUT_DIR/ium.bin"
echo "提取 tail file (IUM)..."
dd if="$INPUT" of="$TAIL_FILE" bs=1 skip=$IUM_OFFSET count=$IUM_SIZE status=none

if [ $? -eq 0 ]; then
    ACTUAL_TAIL_SIZE=$(stat -f%z "$TAIL_FILE" 2>/dev/null || stat -c%s "$TAIL_FILE" 2>/dev/null)
    echo "  ✓ 已保存: $TAIL_FILE ($ACTUAL_TAIL_SIZE bytes)"
else
    echo "  ✗ 提取失败"
    exit 1
fi

# 生成 metadata.json
METADATA_FILE="$OUTPUT_DIR/metadata.json"
echo "生成 metadata.json..."

cat > "$METADATA_FILE" << EOF
{"blocks": "0x$(printf '%04x' $BLOCKS)", "lastBlockSize": "0x$(printf '%02x' $LAST_BLOCK_SIZE)"}
EOF

echo "  ✓ 已保存: $METADATA_FILE"
echo ""

# 显示结果
echo "========================================="
echo "提取完成!"
echo ""
echo "输出文件:"
echo "  Head (firmware): $HEAD_FILE ($ACTUAL_HEAD_SIZE bytes)"
echo "  Tail (IUM):      $TAIL_FILE ($ACTUAL_TAIL_SIZE bytes)"
echo "  Metadata:        $METADATA_FILE"
echo ""
echo "Metadata 内容:"
cat "$METADATA_FILE"
echo ""