#!/bin/bash
# Complete build script for SoraOS with 2-stage bootloader

set -e  # Exit on any error

echo "==================================="
echo "    SoraOS Build System v1.0"
echo "==================================="
echo ""

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

# Shared compiler flags (single source of truth for both real compiles AND compile_commands.json)
CFLAGS="-ffreestanding -mcmodel=large -mno-red-zone -fno-pic -fno-pie -static -fno-stack-protector -nostdlib -mno-mmx -mno-sse -mno-sse2 -m64"
INCLUDE="-I./include"

# compile_commands.json setup (for clangd/nvim LSP support)
CCJ_OUTPUT="compile_commands.json"
PROJECT_DIR="$(pwd)"

append_ccj_entry() {
    local src_file="$1"
    local full_cmd="$2"
    if [ "$ccj_first" = true ]; then
        ccj_first=false
    else
        echo "," >> "$CCJ_OUTPUT"
    fi
    printf '  {\n' >> "$CCJ_OUTPUT"
    printf '    "directory": "%s",\n' "$PROJECT_DIR" >> "$CCJ_OUTPUT"
    printf '    "file": "%s",\n' "$src_file" >> "$CCJ_OUTPUT"
    printf '    "command": "%s"\n' "$full_cmd" >> "$CCJ_OUTPUT"
    printf '  }' >> "$CCJ_OUTPUT"
}

echo "[" > "$CCJ_OUTPUT"
ccj_first=true

# Prepare build environment 
echo -e "Preparing build environment...${NC}" 
echo -e "Creating Folders${NC}"
mkdir -p bin obj boot include
echo -e "${GREEN}✓${NC} Folders created.${NC}"

# Step 1: Assemble Stage 1 bootloader (MBR - 512 bytes)
echo -e "${BLUE}[1/7]${NC} Assembling Stage 1 bootloader (MBR)..."
nasm -f bin ./boot/boot.asm -o ./bin/boot.bin

# Step 1.5: Compile C source files
echo -e "${BLUE}[2/7]${NC} Compiling C source files..."
COUNT=$(ls src/*.c 2>/dev/null | wc -l)
if [ "$COUNT" -eq 0 ]; then
    echo -e "${YELLOW}No C source files found in src/. Skipping compilation.${NC}"
else
COUNTER=1
    for file in src/*.c; do
        echo -e "${BLUE}[$COUNTER/$COUNT]${NC} Compiling $file..."
        ((COUNTER++))
        name=$(basename "$file")
        gcc $CFLAGS $INCLUDE -c "$file" -o "obj/${name}.o"
        append_ccj_entry "$file" "gcc $CFLAGS $INCLUDE -c $file -o obj/${name}.o"
    done
    echo -e "${GREEN}✓${NC} C source files compiled.${NC}"
fi


# Step 2: Compile kernel C code
echo -e "${BLUE}[3/7]${NC} Compiling kernel..."
gcc $CFLAGS $INCLUDE -c kernel.c -o ./obj/kernel.c.o
append_ccj_entry "kernel.c" "gcc $CFLAGS $INCLUDE -c kernel.c -o ./obj/kernel.c.o"

# Close compile_commands.json now that all C compiling is done
echo "" >> "$CCJ_OUTPUT"
echo "]" >> "$CCJ_OUTPUT"

# Step 3: Assemble kernel entry point
echo -e "${BLUE}[4/7]${NC} Assembling kernel entry..."
nasm -f elf64 ./boot/kernel.asm -o ./obj/kernel.asm.o

# Step 4: Link kernel
echo -e "${BLUE}[5/7]${NC} Linking kernel..."
ld -T linker.ld -o ./bin/kernel.bin ./obj/*.o --oformat binary --nostdlib
# Debug build (optional)
ld -T linker.ld -o ./bin/kernel_debug.elf ./obj/*.o --oformat elf64-x86-64 --nostdlib

# Step 4.5: Calculate kernel size in sectors 
KERNEL_SIZE=$(stat -f%z ./bin/kernel.bin 2>/dev/null || stat -c%s ./bin/kernel.bin 2>/dev/null)
SECTORS=$(( (KERNEL_SIZE + 511) / 512 ))  #Round up to nearest sector
echo -e "${YELLOW}Kernel size: ${KERNEL_SIZE} bytes, which is ${SECTORS} sectors.${NC}"

# Step 5: Assemble Stage 2 bootloader (extended loader)
echo -e "${BLUE}[6/7]${NC} Assembling Stage 2 bootloader..."
nasm -f bin ./boot/elevator.asm -D KERNEL_SECTORS=$SECTORS -o ./bin/elevator.bin

# Step 6: Create OS image
echo -e "${BLUE}[7/7]${NC} Creating OS image..."
cat ./bin/boot.bin ./bin/elevator.bin ./bin/kernel.bin > os.bin

# Pad to floppy size (1.44MB)
# FIX: Uncomment the line below if you want to ensure the image is exactly 1.44MB 
truncate -s 1440K os.bin



echo ""
echo -e "${GREEN}✓ Build complete!${NC}"
echo ""
echo "==================================="
echo "File Layout:"
echo "==================================="
echo "Sector 1:    Stage 1 (MBR)"
echo "Sectors 2-6: Stage 2 (Extended Bootloader)"
echo "Sectors 7+:  Kernel"
echo ""

# Show sizes
echo "File Sizes:"
printf "%-15s %10s\n" "File" "Size"
printf "%-15s %10s\n" "----" "----"
printf "%-15s %10d bytes\n" "boot.bin" $(stat -f%z ./bin/boot.bin 2>/dev/null || stat -c%s ./bin/boot.bin 2>/dev/null)
printf "%-15s %10d bytes\n" "elevator.bin" $(stat -f%z ./bin/elevator.bin 2>/dev/null || stat -c%s ./bin/elevator.bin 2>/dev/null)
printf "%-15s %10d bytes\n" "kernel.bin" $(stat -f%z ./bin/kernel.bin 2>/dev/null || stat -c%s ./bin/kernel.bin 2>/dev/null)
printf "%-15s %10d bytes\n" "os.bin" $(stat -f%z os.bin 2>/dev/null || stat -c%s os.bin 2>/dev/null)
echo ""

echo -e "${YELLOW}Running QEMU...${NC}"
echo "==================================="
echo "Press Ctrl+C to exit QEMU"
echo ""

qemu-system-x86_64 -drive format=raw,file=os.bin -no-reboot

echo -e "${GREEN}Done!${NC}"