import base64
import io
import math
from typing import List, Literal
from PIL import Image


def stitch_images(images: List[str], direction: Literal["horizontal", "vertical", "grid"] = "horizontal",
                  columns: int = 2, spacing: int = 0, background_color: str = "#FFFFFF",
                  resize_mode: Literal["none", "fit_width", "fit_height"] = "none") -> dict:
    if len(images) < 2:
        raise ValueError("至少需要 2 张图片")
    
    pil_images = [Image.open(io.BytesIO(base64.b64decode(img_b64))).convert("RGB") for img_b64 in images]
    
    if resize_mode == "fit_width":
        w = max(img.width for img in pil_images)
        pil_images = [img.resize((w, int(img.height * w / img.width)), Image.LANCZOS) if img.width != w else img for img in pil_images]
    elif resize_mode == "fit_height":
        h = max(img.height for img in pil_images)
        pil_images = [img.resize((int(img.width * h / img.height), h), Image.LANCZOS) if img.height != h else img for img in pil_images]
    
    if direction == "horizontal":
        w = sum(img.width for img in pil_images) + spacing * (len(pil_images) - 1)
        h = max(img.height for img in pil_images)
        result = Image.new("RGB", (w, h), background_color)
        x = 0
        for img in pil_images:
            result.paste(img, (x, 0))
            x += img.width + spacing
    elif direction == "vertical":
        w = max(img.width for img in pil_images)
        h = sum(img.height for img in pil_images) + spacing * (len(pil_images) - 1)
        result = Image.new("RGB", (w, h), background_color)
        y = 0
        for img in pil_images:
            result.paste(img, (0, y))
            y += img.height + spacing
    else:
        rows = math.ceil(len(pil_images) / columns)
        max_w, max_h = max(img.width for img in pil_images), max(img.height for img in pil_images)
        w = max_w * columns + spacing * (columns - 1)
        h = max_h * rows + spacing * (rows - 1)
        result = Image.new("RGB", (w, h), background_color)
        for i, img in enumerate(pil_images):
            x = (i % columns) * (max_w + spacing)
            y = (i // columns) * (max_h + spacing)
            result.paste(img, (x, y))
    
    buf = io.BytesIO()
    result.save(buf, format="PNG")
    return {"image": base64.b64encode(buf.getvalue()).decode(), "width": result.width, "height": result.height}