# ----------------------------------------------------------------------
# IMPORTS
# ----------------------------------------------------------------------
import io
import time
import requests
from PIL import Image, ImageOps
from typing import List
from requests.adapters import HTTPAdapter
from urllib3.util.retry import Retry
from src.utils import ProcessingContext, create_pipeline_step, LOG_LEVEL_MAP, EMOJI_MAP

# ----------------------------------------------------------------------
# GLOBAL CONSTANTS
# ----------------------------------------------------------------------
BATCH_DOWNLOAD_TIMEOUT = 30
MAX_RETRIES = 3
RETRY_DELAY = 2
BACKOFF_MULTIPLIER = 1.5
MAX_RETRIES_PER_REQUEST = 2

# ----------------------------------------------------------------------
# SESSION CONFIGURATION
# ----------------------------------------------------------------------
session = requests.Session()
session.headers.update({
    'User-Agent': 'Mozilla/5.0 (compatible; ImageProcessor/1.0)',
    'Accept': 'image/*',
    'Accept-Encoding': 'gzip, deflate',
    'Connection': 'keep-alive'
})

retry_strategy = Retry(
    total=MAX_RETRIES_PER_REQUEST,
    status_forcelist=[429, 500, 502, 503, 504],
    backoff_factor=1,
    allowed_methods=["GET"]
)
adapter = HTTPAdapter(max_retries=retry_strategy)
session.mount("http://", adapter)
session.mount("https://", adapter)

# ----------------------------------------------------------------------
# CORE IMPLEMENTATION
# ----------------------------------------------------------------------
def download_image_with_retry(url, max_retries=MAX_RETRIES, timeout=BATCH_DOWNLOAD_TIMEOUT):
    last_exception = None
    
    for attempt in range(max_retries + 1):
        try:
            delay = RETRY_DELAY * (BACKOFF_MULTIPLIER ** attempt) if attempt > 0 else 0
            if delay > 0:
                time.sleep(delay)
                
            resp = session.get(url, timeout=timeout)
            resp.raise_for_status()
            
            if "image" not in resp.headers.get("Content-Type", ""):
                raise ValueError("Non-image content received")
                
            return resp.content, attempt + 1
            
        except Exception as e:
            last_exception = e
            if attempt < max_retries:
                continue
            else:
                raise last_exception

def download_images_batch(contexts, batch_logs):
    function_name = "download_images_batch"
    start_time = time.perf_counter()
    downloaded_count = 0
    skipped_count = 0
    error_count = 0
    
    for ctx in contexts:
        log_item = {
            "image_url": ctx.url,
            "function": function_name,
            "data": {}
        }
        
        if ctx.skip_run or ctx.skip_processing:
            log_item["status"] = "skipped"
            log_item["data"]["reason"] = "marked_for_skip"
            batch_logs.append(log_item)
            skipped_count += 1
            continue
            
        try:
            download_start = time.perf_counter()
            content, attempts = download_image_with_retry(ctx.url)
            download_time = time.perf_counter() - download_start
            
            content_type = session.head(ctx.url, timeout=5).headers.get("Content-Type", "unknown")
            content_size = len(content)
            
            img = Image.open(io.BytesIO(content))
            original_size = img.size
            
            ctx._download_content = content
            
            log_item["status"] = "ok"
            log_item["data"].update({
                "download_time": round(download_time, 4),
                "attempts": attempts,
                "content_size": content_size,
                "content_type": content_type,
                "image_size": original_size
            })
            downloaded_count += 1
            
        except Exception as e:
            log_item["status"] = "error"
            log_item["exception"] = str(e)
            log_item["data"]["download_time"] = round(time.perf_counter() - download_start, 4) if 'download_start' in locals() else 0
            ctx.skip_run = True
            error_count += 1
            
        batch_logs.append(log_item)
    
    processing_time = time.perf_counter() - start_time
    download_summary = {
        "function": "download_summary",
        "status": "info",
        "data": {
            "total_time": round(processing_time, 4),
            "downloaded_count": downloaded_count,
            "skipped_count": skipped_count,
            "error_count": error_count,
            "success_rate": f"{downloaded_count/(downloaded_count+error_count):.2%}" if (downloaded_count + error_count) > 0 else "N/A"
        }
    }
    batch_logs.append(download_summary)
    
    if error_count > 0:
        batch_abort_log = {
            "function": "batch_abort_due_to_download_failures",
            "status": "error", 
            "data": {
                "reason": "One or more images failed to download",
                "total_contexts": len(contexts),
                "download_errors": error_count,
                "downloaded_successfully": downloaded_count,
                "action": "Aborting entire batch processing"
            }
        }
        batch_logs.append(batch_abort_log)
        
        for ctx in contexts:
            ctx.skip_run = True
    
    return batch_logs, downloaded_count, skipped_count, error_count

def image_download_batch_implementation(contexts, batch_logs):
    batch_logs, downloaded, skipped, errors = download_images_batch(contexts, batch_logs)
    return batch_logs

# ----------------------------------------------------------------------
# MAIN PIPELINE FUNCTION
# ----------------------------------------------------------------------
def _ensure_models_loaded():
    import app
    app.ensure_models_loaded()

pipeline_step = create_pipeline_step(_ensure_models_loaded)

@pipeline_step
def image_download(
    contexts: List[ProcessingContext],
    batch_logs: List[dict] | None = None
):
    import logging
    
    if batch_logs is None:
        batch_logs = []
        
    calibration_info = {
        "function": "image_download_calibration_info",
        "status": "info",
        "data": {
            "download_timeout": BATCH_DOWNLOAD_TIMEOUT,
            "max_retries": MAX_RETRIES,
            "retry_delay": RETRY_DELAY,
            "backoff_multiplier": BACKOFF_MULTIPLIER,
            "max_retries_per_request": MAX_RETRIES_PER_REQUEST
        }
    }
    batch_logs.append(calibration_info)
    
    start_time = time.perf_counter()
    logging.log(LOG_LEVEL_MAP["INFO"], f"{EMOJI_MAP['INFO']} Starting image_download for {len(contexts)} items")
    
    image_download_batch_implementation(contexts, batch_logs)
    
    processing_time = time.perf_counter() - start_time
    logging.log(LOG_LEVEL_MAP["SUCCESS"], f"{EMOJI_MAP['SUCCESS']} Completed image_download for {len(contexts)} items in {processing_time:.3f}s")
    
    return batch_logs