"""Pipeline management for SDXL Model Merger."""

import torch
from diffusers import (
    StableDiffusionXLPipeline,
    AutoencoderKL,
    DPMSolverSDEScheduler,
)

from . import config
from .config import device, dtype, CACHE_DIR, device_description, is_running_on_spaces, set_download_cancelled
from .downloader import get_safe_filename_from_url, download_file_with_progress
from .gpu_decorator import GPU


@GPU(duration=300)
def _load_and_setup_pipeline(checkpoint_path, vae_path, lora_paths_and_strengths, load_kwargs):
    """GPU-decorated helper that performs all GPU-intensive pipeline setup."""
    _pipe = StableDiffusionXLPipeline.from_single_file(
        str(checkpoint_path),
        **load_kwargs,
    )
    print("  ✅ Text encoders loaded")

    # Move to device (unless using device_map='auto' which handles this automatically)
    if not is_running_on_spaces() or device != "cpu":
        print(f"  ⚙️ Moving pipeline to device: {device_description}...")
        _pipe = _pipe.to(device=device, dtype=dtype)

    # Load custom VAE if provided
    if vae_path is not None:
        print("  ⚙️ Loading VAE weights...")
        vae = AutoencoderKL.from_single_file(
            str(vae_path),
            torch_dtype=dtype,
        )
        print("  ⚙️ Setting custom VAE...")
        _pipe.vae = vae.to(device=device, dtype=torch.float32)

    # Load and fuse each LoRA
    if lora_paths_and_strengths:
        # Ensure pipeline is on device for LoRA fusion
        _pipe = _pipe.to(device=device, dtype=dtype)

        for i, (lora_path, strength) in enumerate(lora_paths_and_strengths):
            adapter_name = f"lora_{i}"
            print(f"  ⚙️ Loading LoRA {i+1}/{len(lora_paths_and_strengths)}...")
            _pipe.load_lora_weights(str(lora_path), adapter_name=adapter_name)
            print(f"  ⚙️ Fusing LoRA {i+1} with strength={strength}...")
            _pipe.fuse_lora(adapter_names=[adapter_name], lora_scale=strength)
            _pipe.unload_lora_weights()
    else:
        # Move pipeline to device even without LoRAs
        _pipe = _pipe.to(device=device, dtype=dtype)

    # Set scheduler
    print("  ⚙️ Configuring scheduler...")
    _pipe.scheduler = DPMSolverSDEScheduler.from_config(
        _pipe.scheduler.config,
        algorithm_type="sde-dpmsolver++",
        use_karras_sigmas=False,
    )

    # Keep VAE in float32 to prevent colorful static output
    _pipe.vae.to(dtype=torch.float32)

    return _pipe


def load_pipeline(
    checkpoint_url: str,
    vae_url: str,
    lora_urls_str: str,
    lora_strengths_str: str,
    progress=None
) -> tuple[str, str]:
    """
    Load SDXL pipeline with checkpoint, VAE, and LoRAs.

    Args:
        checkpoint_url: URL to base model .safetensors file
        vae_url: Optional URL to VAE .safetensors file
        lora_urls_str: Newline-separated URLs for LoRA models
        lora_strengths_str: Comma-separated strength values for each LoRA
        progress: Optional gr.Progress() object for UI updates

    Yields:
        Tuple of (status_message, progress_text) at each loading stage.

    Returns:
        Final yielded tuple of (final_status_message, progress_text)
    """
    # Clear any previously loaded pipeline so the UI reflects loading state
    config.set_pipe(None)

    try:
        set_download_cancelled(False)

        print("=" * 60)
        print("🔄 Loading SDXL Pipeline...")
        print("=" * 60)

        checkpoint_filename = get_safe_filename_from_url(checkpoint_url, type_prefix="model")
        checkpoint_path = CACHE_DIR / checkpoint_filename

        # Check if checkpoint is already cached
        checkpoint_cached = checkpoint_path.exists() and checkpoint_path.stat().st_size > 0

        # Validate cache file before using it
        if checkpoint_cached:
            is_valid, msg = config.validate_cache_file(checkpoint_path)
            if not is_valid:
                print(f"  ⚠️ Cache invalid: {msg}")
                checkpoint_path.unlink(missing_ok=True)
                checkpoint_cached = False

        # VAE: Use suffix="_vae" and default to "vae.safetensors" for proper caching/dropdown matching
        vae_filename = get_safe_filename_from_url(vae_url, default_name="vae.safetensors", suffix="_vae") if vae_url.strip() else None
        vae_path = CACHE_DIR / vae_filename if vae_filename else None
        vae_cached = vae_url.strip() and vae_path and vae_path.exists() and vae_path.stat().st_size > 0

        # Validate VAE cache file before using it
        if vae_cached:
            is_valid, msg = config.validate_cache_file(vae_path)
            if not is_valid:
                print(f"  ⚠️ VAE Cache invalid: {msg}")
                vae_path.unlink(missing_ok=True)
                vae_cached = False

        # Download checkpoint (skips if already cached)
        if progress:
            progress(0.1, desc="Downloading base model..." if not checkpoint_cached else "Loading base model...")

        if not checkpoint_cached:
            status_msg = f"📥 Downloading {checkpoint_path.name}..."
            print(f"  📥 Downloading: {checkpoint_path.name}")
        else:
            status_msg = f"✅ Using cached {checkpoint_path.name}"
            print(f"  ✅ Using cached: {checkpoint_path.name}")

        yield status_msg, "Starting download..."

        if not checkpoint_cached:
            download_file_with_progress(checkpoint_url, checkpoint_path)

        # Download VAE if provided (loading happens in _load_and_setup_pipeline)
        if vae_url and vae_url.strip():
            if vae_path:
                status_msg = f"📥 Downloading {vae_path.name}..." if not vae_cached else f"✅ Using cached {vae_path.name}"
                print(f"  📥 VAE: {vae_path.name}" if not vae_cached else f"  ✅ VAE (cached): {vae_path.name}")

                if progress:
                    progress(0.2, desc="Downloading VAE..." if not vae_cached else "Loading VAE...")

                yield status_msg, f"Downloading VAE: {vae_path.name}" if not vae_cached else f"Using cached VAE: {vae_path.name}"

                if not vae_cached:
                    download_file_with_progress(vae_url, vae_path)

        # For CPU/low-memory environments on Spaces, use device_map for better RAM management
        load_kwargs = {
            "torch_dtype": dtype,
            "use_safetensors": True,
        }

        if is_running_on_spaces() and device == "cpu":
            print("  ℹ️ CPU mode detected: enabling device_map='auto' for better RAM management")
            load_kwargs["device_map"] = "auto"

        # Parse LoRA URLs & ensure strengths list matches
        lora_urls = [u.strip() for u in lora_urls_str.split("\n") if u.strip()]
        strengths_raw = [s.strip() for s in lora_strengths_str.split(",")]
        strengths = []
        for i, url in enumerate(lora_urls):
            try:
                val = float(strengths_raw[i]) if i < len(strengths_raw) else 1.0
                strengths.append(val)
            except ValueError:
                strengths.append(1.0)

        # Download LoRAs (CPU-bound downloads, before GPU work)
        lora_paths_and_strengths = []
        if lora_urls:
            for i, (lora_url, strength) in enumerate(zip(lora_urls, strengths)):
                lora_filename = get_safe_filename_from_url(lora_url, suffix="_lora")
                lora_path = CACHE_DIR / lora_filename
                lora_cached = lora_path.exists() and lora_path.stat().st_size > 0

                # Validate LoRA cache file before using it
                if lora_cached:
                    is_valid, msg = config.validate_cache_file(lora_path)
                    if not is_valid:
                        print(f"  ⚠️ LoRA Cache invalid: {msg}")
                        lora_path.unlink(missing_ok=True)
                        lora_cached = False

                if not lora_cached:
                    print(f"  📥 LoRA {i+1}/{len(lora_urls)}: Downloading {lora_path.name}...")
                    status_msg = f"📥 Downloading LoRA {i+1}/{len(lora_urls)}: {lora_path.name}..."
                else:
                    print(f"  ✅ LoRA {i+1}/{len(lora_urls)}: Using cached {lora_path.name}")
                    status_msg = f"✅ Using cached LoRA {i+1}/{len(lora_urls)}: {lora_path.name}"

                yield (
                    status_msg,
                    f"Downloading LoRA {i+1}/{len(lora_urls)} ({lora_path.name})..." if not lora_cached
                    else f"Using cached LoRA {i+1}/{len(lora_urls)} ({lora_path.name})"
                )

                if not lora_cached:
                    download_file_with_progress(lora_url, lora_path)

                lora_paths_and_strengths.append((lora_path, strength))

        # All downloads complete — now do GPU-intensive setup in one decorated call
        yield "⚙️ Loading SDXL pipeline...", "Loading model weights into memory..."

        if progress:
            progress(0.5, desc="Loading pipeline...")

        _pipe = _load_and_setup_pipeline(
            checkpoint_path, vae_path, lora_paths_and_strengths, load_kwargs
        )

        if progress:
            progress(0.95, desc="Finalizing...")

        # ✅ Only publish the pipeline globally AFTER all steps succeed
        config.set_pipe(_pipe)

        print("  ✅ Pipeline ready!")
        yield "✅ Pipeline ready!", f"Ready! Loaded {len(lora_urls)} LoRA(s)"

    except KeyboardInterrupt:
        set_download_cancelled(False)
        config.set_pipe(None)
        print("\n⚠️ Download cancelled by user")
        return ("⚠️ Download cancelled by user", "Cancelled")
    except Exception as e:
        import traceback
        config.set_pipe(None)
        error_msg = f"❌ Error loading pipeline: {str(e)}"
        print(f"\n{error_msg}")
        print(traceback.format_exc())
        return (error_msg, f"Error: {str(e)}")


def cancel_download():
    """Set the global cancellation flag to stop any ongoing downloads."""
    set_download_cancelled(True)


def get_pipeline() -> StableDiffusionXLPipeline | None:
    """Get the currently loaded pipeline."""
    return config.get_pipe()