"""
Sopel plugin: salvador

Converts an image URL to mIRC colour art using half-block characters.

  !draw <url>          - render at default height (6 lines)
  !draw <lines> <url>  - render at custom height (4-12 lines)
"""

import time
import urllib.request
from io import BytesIO

from PIL import Image, ImageFile

ImageFile.LOAD_TRUNCATED_IMAGES = True
from sopel import plugin


MAX_WIDTH      = 60
DEFAULT_HEIGHT = 6
MIN_HEIGHT     = 4
MAX_HEIGHT     = 12
FLOOD_DELAY    = 0.4
MAX_BYTES      = 5 * 1024 * 1024  # 5 MB

# IRC monospace character cells are approximately twice as tall as they are wide.
# _fit multiplies the image aspect ratio by this factor so the rendered output
# uses enough character columns to compensate for the tall cells.
CHAR_RATIO = 2.0

USAGE = f'usage: salvador [<lines>] <url>  (lines: {MIN_HEIGHT}-{MAX_HEIGHT}, default {DEFAULT_HEIGHT})'

# Full mIRC 99-colour palette (indices 0-98)
MIRC = [
    (0xff,0xff,0xff),(0x00,0x00,0x00),(0x00,0x00,0x7f),(0x00,0x93,0x00),
    (0xff,0x00,0x00),(0x7f,0x00,0x00),(0x9c,0x00,0x9c),(0xfc,0x7f,0x00),
    (0xff,0xff,0x00),(0x00,0xfc,0x00),(0x00,0x93,0x93),(0x00,0xff,0xff),
    (0x00,0x00,0xfc),(0xff,0x00,0xff),(0x55,0x55,0x55),(0xaa,0xaa,0xaa),
    (0x47,0x00,0x00),(0x47,0x21,0x00),(0x47,0x47,0x00),(0x32,0x47,0x00),
    (0x00,0x47,0x00),(0x00,0x47,0x2c),(0x00,0x47,0x47),(0x00,0x27,0x47),
    (0x00,0x00,0x47),(0x2e,0x00,0x47),(0x47,0x00,0x47),(0x47,0x00,0x2a),
    (0x74,0x00,0x00),(0x74,0x3a,0x00),(0x74,0x74,0x00),(0x51,0x74,0x00),
    (0x00,0x74,0x00),(0x00,0x74,0x49),(0x00,0x74,0x74),(0x00,0x40,0x74),
    (0x00,0x00,0x74),(0x4b,0x00,0x74),(0x74,0x00,0x74),(0x74,0x00,0x45),
    (0xb5,0x00,0x00),(0xb5,0x63,0x00),(0xb5,0xb5,0x00),(0x7d,0xb5,0x00),
    (0x00,0xb5,0x00),(0x00,0xb5,0x71),(0x00,0xb5,0xb5),(0x00,0x63,0xb5),
    (0x00,0x00,0xb5),(0x75,0x00,0xb5),(0xb5,0x00,0xb5),(0xb5,0x00,0x6b),
    (0xff,0x00,0x00),(0xff,0x8c,0x00),(0xff,0xff,0x00),(0xb2,0xff,0x00),
    (0x00,0xff,0x00),(0x00,0xff,0xa0),(0x00,0xff,0xff),(0x00,0x8c,0xff),
    (0x00,0x00,0xff),(0xa5,0x00,0xff),(0xff,0x00,0xff),(0xff,0x00,0x98),
    (0xff,0x59,0x59),(0xff,0xb4,0x59),(0xff,0xff,0x71),(0xcf,0xff,0x60),
    (0x6f,0xff,0x6f),(0x65,0xff,0xc9),(0x6d,0xff,0xff),(0x59,0xb4,0xff),
    (0x59,0x59,0xff),(0xc4,0x59,0xff),(0xff,0x66,0xff),(0xff,0x59,0xbc),
    (0xff,0x9c,0x9c),(0xff,0xd3,0x9c),(0xff,0xff,0x9c),(0xe2,0xff,0x9c),
    (0x9c,0xff,0x9c),(0x9c,0xff,0xdb),(0x9c,0xff,0xff),(0x9c,0xd3,0xff),
    (0x9c,0x9c,0xff),(0xdc,0x9c,0xff),(0xff,0x9c,0xff),(0xff,0x94,0xd3),
    (0x00,0x00,0x00),(0x13,0x13,0x13),(0x28,0x28,0x28),(0x36,0x36,0x36),
    (0x4d,0x4d,0x4d),(0x65,0x65,0x65),(0x81,0x81,0x81),(0x9f,0x9f,0x9f),
    (0xbc,0xbc,0xbc),(0xe2,0xe2,0xe2),(0xff,0xff,0xff),
]


def _nearest(r, g, b):
    # Perceptually-weighted RGB distance
    rmean = (r + 128) / 2
    best, best_dist = 0, float('inf')
    for i, (cr, cg, cb) in enumerate(MIRC):
        dr, dg, db = r - cr, g - cg, b - cb
        dist = (2 + rmean / 256) * dr*dr + 4*dg*dg + (2 + (255 - rmean) / 256) * db*db
        if dist < best_dist:
            best_dist = dist
            best = i
    return best


def _fetch(url):
    req = urllib.request.Request(url, headers={'User-Agent': 'salvador/1.0'})
    with urllib.request.urlopen(req, timeout=10) as resp:
        content_type = resp.headers.get('Content-Type', '')
        if 'image' not in content_type:
            raise ValueError(f'not an image ({content_type})')
        return resp.read(MAX_BYTES)


def _fit(img_w, img_h, max_w, max_h):
    aspect = (img_w / img_h) * CHAR_RATIO
    char_aspect = max_w / max_h
    if aspect >= char_aspect:
        w = max_w
        h = max(1, round(max_w / aspect))
    else:
        h = max_h
        w = max(1, round(max_h * aspect))
    return w, h


def _dither(img, w, h):
    buf = [[list(map(float, img.getpixel((x, y)))) for x in range(w)]
           for y in range(h)]
    idx = [[0] * w for _ in range(h)]
    for y in range(h):
        for x in range(w):
            r, g, b = (max(0, min(255, int(v))) for v in buf[y][x])
            c = _nearest(r, g, b)
            idx[y][x] = c
            cr, cg, cb = MIRC[c]
            er, eg, eb = r - cr, g - cg, b - cb
            for dx, dy, f in ((1, 0, 7), (-1, 1, 3), (0, 1, 5), (1, 1, 1)):
                nx, ny = x + dx, y + dy
                if 0 <= nx < w and 0 <= ny < h:
                    buf[ny][nx][0] += er * f / 16
                    buf[ny][nx][1] += eg * f / 16
                    buf[ny][nx][2] += eb * f / 16
    return idx


def _img_to_irc(url, height=DEFAULT_HEIGHT):
    data = _fetch(url)
    img = Image.open(BytesIO(data)).convert('RGB')
    char_w, char_h = _fit(img.width, img.height, MAX_WIDTH, height)
    img = img.resize((char_w, char_h * 2), Image.LANCZOS)
    idx = _dither(img, char_w, char_h * 2)

    lines = []
    for row in range(char_h):
        line = ''
        last_fg = last_bg = None
        for col in range(char_w):
            bg = idx[row * 2][col]
            fg = idx[row * 2 + 1][col]
            if fg != last_fg or bg != last_bg:
                line += f'\x03{fg:02d},{bg:02d}'
                last_fg, last_bg = fg, bg
            line += '▄'
        line += '\x0f'
        lines.append(line)
    return lines


@plugin.command("draw")
@plugin.require_chanmsg
def cmd_draw(bot, trigger):
    args = (trigger.group(2) or "").split(None, 1)
    if not args:
        bot.say(USAGE, trigger.nick)
        return

    height = DEFAULT_HEIGHT
    if len(args) == 2 and args[0].isdigit():
        n = int(args[0])
        if not (MIN_HEIGHT <= n <= MAX_HEIGHT):
            bot.say(USAGE, trigger.nick)
            return
        height = n
        url = args[1]
    else:
        url = args[0]

    url = url.rstrip('.,)>')
    if not url.startswith(('http://', 'https://')):
        bot.say(USAGE, trigger.nick)
        return

    try:
        lines = _img_to_irc(url, height=height)
    except Exception as e:
        bot.say(str(e))
        return
    for line in lines:
        bot.say(line)
        time.sleep(FLOOD_DELAY)