"""
utils/image_utils.py
--------------------
Image I/O, mask manipulation, and debug-image helpers.
"""

import os
import math
import zipfile
import requests
import urllib.request
from pathlib import Path
from typing import List, Tuple, Optional, Union

import cv2
import numpy as np
from PIL import Image
from tqdm import tqdm
import matplotlib
matplotlib.use("Agg")
import matplotlib.pyplot as plt
import matplotlib.patches as mpatches


# -- Image I/O -----------------------------------------------------------------

def load_image_pil(path: str) -> Image.Image:
    """Load image as PIL RGB."""
    return Image.open(path).convert("RGB")


def load_image_cv2(path: str) -> np.ndarray:
    """Load image as OpenCV BGR numpy array."""
    img = cv2.imread(path)
    if img is None:
        raise FileNotFoundError(f"Cannot read image: {path}")
    return img


def pil_to_cv2(img: Image.Image) -> np.ndarray:
    return cv2.cvtColor(np.array(img), cv2.COLOR_RGB2BGR)


def cv2_to_pil(img: np.ndarray) -> Image.Image:
    return Image.fromarray(cv2.cvtColor(img, cv2.COLOR_BGR2RGB))


# Alias for compatibility
load_image = load_image_pil


def show_mask(mask, ax, random_color=False):
    """Stub for SAM visualization."""
    pass


def show_box(box, ax):
    """Stub for SAM visualization."""
    pass


def dilate_mask_with_sam_prediction(mask, dilation_px):
    """Stub for SAM-based dilation."""
    return mask


def save_image(img: Union[Image.Image, np.ndarray], path: str) -> None:
    os.makedirs(os.path.dirname(path) or ".", exist_ok=True)
    if isinstance(img, np.ndarray):
        cv2.imwrite(path, img)
    else:
        img.save(path)


def list_images(directory: str) -> List[str]:
    """Return sorted list of image file paths in a directory."""
    exts = {".jpg", ".jpeg", ".png", ".bmp", ".webp", ".tiff"}
    paths = sorted(
        str(p) for p in Path(directory).iterdir()
        if p.suffix.lower() in exts
    )
    return paths


# -- Mask operations -----------------------------------------------------------

def boxes_to_mask(
    boxes: List[Tuple[int, int, int, int]],
    h: int,
    w: int,
    dilation_px: int = 0,
) -> np.ndarray:
    """
    Convert list of (x1,y1,x2,y2) boxes to a binary uint8 mask (HW).
    Optionally dilate the mask by `dilation_px` pixels.
    """
    mask = np.zeros((h, w), dtype=np.uint8)
    for x1, y1, x2, y2 in boxes:
        x1, y1 = max(0, x1), max(0, y1)
        x2, y2 = min(w, x2), min(h, y2)
        mask[y1:y2, x1:x2] = 255

    if dilation_px > 0:
        kernel = cv2.getStructuringElement(
            cv2.MORPH_ELLIPSE, (dilation_px * 2 + 1, dilation_px * 2 + 1)
        )
        mask = cv2.dilate(mask, kernel)

    return mask


def combine_masks(masks: List[np.ndarray]) -> np.ndarray:
    """OR-combine a list of binary uint8 masks."""
    if not masks:
        raise ValueError("Empty mask list")
    out = np.zeros_like(masks[0])
    for m in masks:
        out = cv2.bitwise_or(out, m)
    return out


def refine_mask_with_sam_prediction(
    raw_mask: np.ndarray,
    sam_masks: List[np.ndarray],
) -> np.ndarray:
    """
    Given SAM predicted masks (each boolean HW), pick the one with the
    highest IoU against the raw_mask and return it as uint8.
    """
    best_mask = raw_mask
    best_iou  = 0.0
    raw_bool  = raw_mask.astype(bool)

    for m in sam_masks:
        m_bool = m.astype(bool)
        intersection = (raw_bool & m_bool).sum()
        union        = (raw_bool | m_bool).sum()
        iou = intersection / (union + 1e-8)
        if iou > best_iou:
            best_iou  = iou
            best_mask = (m_bool.astype(np.uint8)) * 255

    return best_mask


def dilate_mask(mask: np.ndarray, px: int) -> np.ndarray:
    if px <= 0:
        return mask
    kernel = cv2.getStructuringElement(
        cv2.MORPH_ELLIPSE, (px * 2 + 1, px * 2 + 1)
    )
    return cv2.dilate(mask, kernel)


# -- Debug visualisation -------------------------------------------------------

def save_detection_debug(
    scene_path: str,
    detections: List[dict],
    output_path: str,
) -> None:
    """
    Draw bounding boxes + labels on the scene image and save.
    `detections` is a list of dicts with keys: box (x1,y1,x2,y2), label, score.
    """
    img = load_image_pil(scene_path)
    fig, ax = plt.subplots(1, figsize=(12, 8))
    ax.imshow(img)

    colors = plt.cm.get_cmap("tab10").colors
    for i, det in enumerate(detections):
        x1, y1, x2, y2 = det["box"]
        color = colors[i % len(colors)]
        rect = mpatches.FancyBboxPatch(
            (x1, y1), x2 - x1, y2 - y1,
            boxstyle="round,pad=2",
            linewidth=2, edgecolor=color, facecolor="none",
        )
        ax.add_patch(rect)
        ax.text(
            x1, y1 - 6,
            f"{det['label']} ({det['score']:.2f})",
            color="white", fontsize=9,
            bbox=dict(facecolor=color, alpha=0.7, pad=2, edgecolor="none"),
        )

    ax.axis("off")
    plt.tight_layout()
    plt.savefig(output_path, dpi=150, bbox_inches="tight")
    plt.close()


def save_mask_debug(
    scene_path: str,
    mask: np.ndarray,
    output_path: str,
) -> None:
    """Overlay the combined mask on the scene image (red, semi-transparent)."""
    img = np.array(load_image_pil(scene_path))
    overlay = img.copy()
    overlay[mask > 0] = [255, 80, 80]
    blended = cv2.addWeighted(img, 0.55, overlay, 0.45, 0)
    save_image(Image.fromarray(blended), output_path)


def save_comparison(
    before: Union[Image.Image, np.ndarray],
    after:  Union[Image.Image, np.ndarray],
    output_path: str,
    labels: Tuple[str, str] = ("Before", "After"),
) -> None:
    """Save a side-by-side before/after comparison image."""
    if isinstance(before, np.ndarray):
        before = cv2_to_pil(before)
    if isinstance(after, np.ndarray):
        after = cv2_to_pil(after)

    w  = before.width + after.width + 20
    h  = max(before.height, after.height) + 40
    canvas = Image.new("RGB", (w, h), (30, 30, 30))
    canvas.paste(before, (0, 40))
    canvas.paste(after,  (before.width + 20, 40))

    # draw labels using matplotlib to avoid font dependency
    fig, axes = plt.subplots(1, 2, figsize=(14, 7))
    axes[0].imshow(before); axes[0].set_title(labels[0], fontsize=14); axes[0].axis("off")
    axes[1].imshow(after);  axes[1].set_title(labels[1], fontsize=14); axes[1].axis("off")
    plt.tight_layout()
    plt.savefig(output_path, dpi=150, bbox_inches="tight")
    plt.close()


# -- Checkpoint downloader -----------------------------------------------------

def download_file(url: str, dest: str, desc: str = "") -> None:
    """Download a file with a progress bar."""
    os.makedirs(os.path.dirname(dest) or ".", exist_ok=True)
    if os.path.exists(dest):
        print(f"  [DONE] Already downloaded: {os.path.basename(dest)}")
        return

    print(f"  v Downloading {desc or os.path.basename(dest)} ...")
    response = requests.get(url, stream=True, timeout=120)
    response.raise_for_status()

    total = int(response.headers.get("content-length", 0))
    with open(dest, "wb") as f, tqdm(
        total=total, unit="B", unit_scale=True, desc=desc or os.path.basename(dest)
    ) as bar:
        for chunk in response.iter_content(chunk_size=8192):
            f.write(chunk)
            bar.update(len(chunk))


def download_text_file(url: str, dest: str) -> None:
    """Download a small text/config file."""
    os.makedirs(os.path.dirname(dest) or ".", exist_ok=True)
    if os.path.exists(dest):
        return
    print(f"    Fetching config: {os.path.basename(dest)} ...")
    resp = requests.get(url, timeout=30)
    resp.raise_for_status()
    with open(dest, "w") as f:
        f.write(resp.text)


def unzip(zip_path: str, dest_dir: str) -> None:
    print(f"  -> Extracting {os.path.basename(zip_path)} ...")
    with zipfile.ZipFile(zip_path, "r") as z:
        z.extractall(dest_dir)