#!/usr/bin/env python3
import os
import glob
import shutil
import subprocess
import yaml
import sys
from PIL import Image

# --- 1. Load Configuration ---
def load_config(config_path="config.yml"):
    if not os.path.exists(config_path):
        print(f"❌ Error: Configuration file '{config_path}' not found.")
        sys.exit(1)
    
    with open(config_path, 'r') as file:
        return yaml.safe_load(file)

# --- 2. System Checks ---
def check_dependencies():
    tools = ["ffmpeg", "pdftoppm"]
    missing = []
    for tool in tools:
        if not shutil.which(tool):
            missing.append(tool)
    
    if missing:
        print(f"❌ Error: Missing required tools: {', '.join(missing)}")
        print("   Please install them: apt install ffmpeg poppler-utils")
        sys.exit(1)

def main():
    print("🚀 Starting PDF to Scroll Video Converter...")
    
    # Load settings
    cfg = load_config()
    
    INPUT_DIR = cfg['input_folder']
    CACHE_DIR = cfg['cache_folder']
    OUTPUT_FILE = cfg['output_filename']
    WIDTH = cfg['resolution']['width']
    HEIGHT = cfg['resolution']['height']
    SEC_PER_SLIDE = cfg['timing']['seconds_per_slide']
    FPS = cfg['timing']['fps']
    
    check_dependencies()
    
    # Clean and create directories
    if os.path.exists(CACHE_DIR):
        shutil.rmtree(CACHE_DIR)
    os.makedirs(CACHE_DIR)
    
    # Find PDFs
    pdf_files = sorted(glob.glob(os.path.join(INPUT_DIR, "*.pdf")))
    if not pdf_files:
        print("❌ No PDF files found in the input folder.")
        sys.exit(1)
    
    print(f"📂 Found {len(pdf_files)} PDF(s). Processing...")
    
    # --- Step 1: Convert PDFs to Images ---
    global_counter = 0
    
    for pdf in pdf_files:
        print(f"   📄 Processing: {os.path.basename(pdf)}")
        cmd = f"pdftoppm -png -r 150 \"{pdf}\" \"{CACHE_DIR}/temp\""
        subprocess.run(cmd, shell=True, check=True, 
                      stderr=subprocess.DEVNULL, stdout=subprocess.DEVNULL)
        
        temp_files = sorted(glob.glob(os.path.join(CACHE_DIR, "temp-*.png")))
        for temp_img in temp_files:
            new_name = os.path.join(CACHE_DIR, f"slide_{global_counter:05d}.png")
            os.rename(temp_img, new_name)
            global_counter += 1
    
    # --- Step 2: Process Images ---
    print("📐 Processing images...")
    
    all_images = sorted(glob.glob(os.path.join(CACHE_DIR, "slide_*.png")))
    processed_dir = os.path.join(CACHE_DIR, "processed")
    os.makedirs(processed_dir, exist_ok=True)
    
    # Resize all images to target width
    processed_images = []
    total_height = 0
    
    for i, img_path in enumerate(all_images):
        img = Image.open(img_path)
        
        # Resize to target width while maintaining aspect ratio
        aspect_ratio = img.height / img.width
        new_height = int(WIDTH * aspect_ratio)
        img_resized = img.resize((WIDTH, new_height), Image.LANCZOS)
        
        output_path = os.path.join(processed_dir, f"frame_{i:05d}.png")
        img_resized.save(output_path, "PNG", optimize=True)
        
        processed_images.append(output_path)
        total_height += new_height
        
        img.close()
        
        if (i + 1) % 10 == 0:
            print(f"   ... Processed {i + 1}/{len(all_images)} images")
    
    total_slides = len(processed_images)
    total_duration = total_slides * SEC_PER_SLIDE
    
    print(f"\n📊 Statistics:")
    print(f"   Total Slides: {total_slides}")
    print(f"   Combined Height: {total_height:,}px")
    print(f"   Video Duration: {total_duration} seconds")
    print(f"   Viewport: {WIDTH}x{HEIGHT}px")
    
    # --- Step 3: Create Stitched Image in Chunks ---
    print("\n🧩 Creating scrollable canvas...")
    
    # For very long documents, we need to split into manageable chunks
    MAX_CHUNK_HEIGHT = 65000  # Safe limit for PNG
    
    chunk_images = []
    current_chunk = []
    current_chunk_height = 0
    chunk_num = 0
    
    for img_path in processed_images:
        with Image.open(img_path) as img:
            img_height = img.height
            
            # Check if adding this image would exceed chunk limit
            if current_chunk_height + img_height > MAX_CHUNK_HEIGHT and current_chunk:
                # Save current chunk
                chunk_path = os.path.join(CACHE_DIR, f"chunk_{chunk_num:03d}.png")
                
                # Stitch current chunk
                total_h = sum(Image.open(p).height for p in current_chunk)
                canvas = Image.new('RGB', (WIDTH, total_h), (255, 255, 255))
                
                y_offset = 0
                for chunk_img_path in current_chunk:
                    with Image.open(chunk_img_path) as ci:
                        canvas.paste(ci, (0, y_offset))
                        y_offset += ci.height
                
                canvas.save(chunk_path, "PNG", optimize=True)
                canvas.close()
                
                chunk_images.append(chunk_path)
                print(f"   ... Created chunk {chunk_num + 1} ({current_chunk_height:,}px)")
                
                # Reset for next chunk
                current_chunk = []
                current_chunk_height = 0
                chunk_num += 1
            
            current_chunk.append(img_path)
            current_chunk_height += img_height
    
    # Save final chunk
    if current_chunk:
        chunk_path = os.path.join(CACHE_DIR, f"chunk_{chunk_num:03d}.png")
        
        total_h = sum(Image.open(p).height for p in current_chunk)
        canvas = Image.new('RGB', (WIDTH, total_h), (255, 255, 255))
        
        y_offset = 0
        for chunk_img_path in current_chunk:
            with Image.open(chunk_img_path) as ci:
                canvas.paste(ci, (0, y_offset))
                y_offset += ci.height
        
        canvas.save(chunk_path, "PNG", optimize=True)
        canvas.close()
        
        chunk_images.append(chunk_path)
        print(f"   ... Created chunk {chunk_num + 1} ({current_chunk_height:,}px)")
    
    # --- Step 4: Create Video from Chunks ---
    print("\n🎥 Encoding video with smooth scroll effect...")
    
    if len(chunk_images) == 1:
        # Simple case: one chunk
        big_image = chunk_images[0]
        
        ffmpeg_cmd = (
            f"ffmpeg -y -v error -stats "
            f"-loop 1 -i \"{big_image}\" "
            f"-vf \"crop={WIDTH}:{HEIGHT}:0:'min(ih-oh,(ih-oh)*t/{total_duration})',format=yuv420p\" "
            f"-t {total_duration} "
            f"-c:v libx264 -preset medium -crf 23 -r {FPS} "
            f"\"{OUTPUT_FILE}\""
        )
        
        result = os.system(ffmpeg_cmd)
        
    else:
        # Multiple chunks: process each and concatenate
        print(f"   Processing {len(chunk_images)} chunks...")
        
        chunk_videos = []
        time_per_chunk = total_duration / len(chunk_images)
        
        for i, chunk_path in enumerate(chunk_images):
            chunk_video = os.path.join(CACHE_DIR, f"chunk_video_{i:03d}.mp4")
            
            ffmpeg_cmd = (
                f"ffmpeg -y -v error -stats "
                f"-loop 1 -i \"{chunk_path}\" "
                f"-vf \"crop={WIDTH}:{HEIGHT}:0:'min(ih-oh,(ih-oh)*t/{time_per_chunk})',format=yuv420p\" "
                f"-t {time_per_chunk} "
                f"-c:v libx264 -preset medium -crf 23 -r {FPS} "
                f"\"{chunk_video}\""
            )
            
            print(f"   ... Encoding chunk {i + 1}/{len(chunk_images)}")
            result = os.system(ffmpeg_cmd)
            if result != 0:
                print(f"❌ Error encoding chunk {i + 1}")
                sys.exit(1)
            
            chunk_videos.append(chunk_video)
        
        # Concatenate chunks
        print("   ... Concatenating chunks...")
        concat_file = os.path.join(CACHE_DIR, "concat_list.txt")
        with open(concat_file, 'w') as f:
            for cv in chunk_videos:
                f.write(f"file '{os.path.abspath(cv)}'\n")
        
        ffmpeg_cmd = (
            f"ffmpeg -y -v error -stats "
            f"-f concat -safe 0 -i \"{concat_file}\" "
            f"-c copy "
            f"\"{OUTPUT_FILE}\""
        )
        
        result = os.system(ffmpeg_cmd)
    
    if result != 0:
        print("❌ Error during ffmpeg encoding.")
        sys.exit(1)
    
    print("\n" + "="*60)
    print(f"✅ SUCCESS! Video saved as: {OUTPUT_FILE}")
    print(f"   Duration: {total_duration}s | Resolution: {WIDTH}x{HEIGHT}")
    print(f"   Frames: {total_duration * FPS:,.0f} | Size: {os.path.getsize(OUTPUT_FILE) / 1024 / 1024:.1f} MB")
    print("="*60)
    
    # Optional: cleanup
    print("\n💡 Tip: Delete the './tmp' folder to free up disk space")

if __name__ == "__main__":
    main()