"""Pure-Python ports of DitherForge core text effects."""

from __future__ import annotations
import numpy as np
from PIL import Image

DEFAULT_ASCII_CHARSET = " .:-=+*#%@"

BRAILLE_BASE = 0x2800
DOT_BITS = [
    [0x01, 0x08],
    [0x02, 0x10],
    [0x04, 0x20],
    [0x40, 0x80],
]


def image_to_gray(img: Image.Image) -> np.ndarray:
    """Convert PIL Image to 2D grayscale numpy array (0-255)."""
    return np.array(img.convert("L"), dtype=np.uint8)


def binary_effect(gray: np.ndarray, cols: int = 80, threshold: int = 128) -> str:
    """Convert grayscale image to binary (0/1) text."""
    h, w = gray.shape
    cols = max(1, min(cols, w))
    block_w = w / cols
    block_h = block_w * 2
    rows = max(1, int(h / block_h))

    lines = []
    for row in range(rows):
        line = ""
        for col in range(cols):
            x0 = int(col * block_w)
            x1 = int((col + 1) * block_w)
            y0 = int(row * block_h)
            y1 = min(int((row + 1) * block_h), h)
            avg = gray[y0:y1, x0:x1].mean()
            line += "1" if avg >= threshold else "0"
        lines.append(line)
    return "\n".join(lines)


def ascii_effect(
    gray: np.ndarray, cols: int = 80, charset: str = DEFAULT_ASCII_CHARSET
) -> str:
    """Convert grayscale image to ASCII art."""
    h, w = gray.shape
    cols = max(1, min(cols, w))
    block_w = w / cols
    block_h = block_w * 2
    rows = max(1, int(h / block_h))

    lines = []
    for row in range(rows):
        line = ""
        for col in range(cols):
            x0 = int(col * block_w)
            x1 = int((col + 1) * block_w)
            y0 = int(row * block_h)
            y1 = min(int((row + 1) * block_h), h)
            avg = gray[y0:y1, x0:x1].mean()
            idx = min(int((avg / 255) * len(charset)), len(charset) - 1)
            line += charset[idx]
        lines.append(line)
    return "\n".join(lines)


def braille_effect(
    gray: np.ndarray, cols: int = 40, threshold: int = 128
) -> str:
    """Convert grayscale image to Unicode braille art."""
    h, w = gray.shape
    cols = max(1, min(cols, w // 2))
    pix_w = cols * 2
    scale = w / pix_w
    pix_h = int(h / scale)
    rows = max(1, pix_h // 4)

    lines = []
    for row in range(rows):
        line = ""
        for col in range(cols):
            cp = 0
            for dy in range(4):
                for dx in range(2):
                    sx = min(int((col * 2 + dx) * scale), w - 1)
                    sy = min(int((row * 4 + dy) * scale), h - 1)
                    if gray[sy, sx] < threshold:
                        cp |= DOT_BITS[dy][dx]
            line += chr(BRAILLE_BASE + cp)
        lines.append(line)
    return "\n".join(lines)