#!/usr/bin/env python3
"""Turns the Launcher's icons (assets/icons/<App id>.png) into C arrays: src/ui/icons.h and icons.cpp.

An icon is 32 x 32 and one colour: a pixel is drawn where the picture is light and opaque, and left
alone where it is dark or transparent. Any image editor's PNG will do (grey, RGB, palette, with or
without alpha, 1 or 8 bits a channel, not interlaced). Run this after changing a picture:

    python3 scripts/make_icons.py

CI runs it with --check, which fails when the arrays are not what the pictures give.
"""
import os
import struct
import sys
import zlib

ROOT = os.path.join(os.path.dirname(os.path.abspath(__file__)), "..")
SOURCE = os.path.join(ROOT, "assets", "icons")
SIZE = 32


def read_png(path):
    """The picture as rows of booleans: True where a pixel is drawn."""
    data = open(path, "rb").read()
    if data[:8] != b"\x89PNG\r\n\x1a\n":
        raise ValueError("not a PNG")
    at, idat, palette, alpha = 8, b"", None, None
    while at < len(data):
        (length,), kind = struct.unpack(">I", data[at:at + 4]), data[at + 4:at + 8]
        body = data[at + 8:at + 8 + length]
        at += 12 + length
        if kind == b"IHDR":
            width, height, depth, colour, _, _, interlace = struct.unpack(">IIBBBBB", body)
        elif kind == b"PLTE":
            palette = [body[i:i + 3] for i in range(0, len(body), 3)]
        elif kind == b"tRNS":
            alpha = body
        elif kind == b"IDAT":
            idat += body
    if interlace or depth not in (1, 8) or (depth == 1 and colour not in (0, 3)):
        raise ValueError("save it as a plain 8-bit or 1-bit PNG, not interlaced")
    channels = {0: 1, 2: 3, 3: 1, 4: 2, 6: 4}[colour]
    step = channels if depth == 8 else 1  # bytes a pixel, for the filters
    stride = (width * channels * depth + 7) // 8
    raw, rows, before = zlib.decompress(idat), [], bytes(stride)
    for y in range(height):
        kind, line = raw[y * (stride + 1)], bytearray(raw[y * (stride + 1) + 1:(y + 1) * (stride + 1)])
        for i in range(stride):
            a = line[i - step] if i >= step else 0
            b, c = before[i], before[i - step] if i >= step else 0
            if kind == 1:
                line[i] = (line[i] + a) & 255
            elif kind == 2:
                line[i] = (line[i] + b) & 255
            elif kind == 3:
                line[i] = (line[i] + (a + b) // 2) & 255
            elif kind == 4:
                p = a + b - c
                pa, pb, pc = abs(p - a), abs(p - b), abs(p - c)
                line[i] = (line[i] + (a if pa <= pb and pa <= pc else b if pb <= pc else c)) & 255
        before = bytes(line)
        row = []
        for x in range(width):
            if depth == 1:
                v = (line[x // 8] >> (7 - x % 8)) & 1
                px = [v * 255] if colour == 0 else [v]
            else:
                px = line[x * channels:(x + 1) * channels]
            if colour == 3:
                opaque = alpha is None or px[0] >= len(alpha) or alpha[px[0]] > 127
                light = sum(palette[px[0]]) > 381
            elif colour in (0, 4):
                opaque, light = colour == 0 or px[1] > 127, px[0] > 127
            else:
                opaque, light = colour == 2 or px[3] > 127, sum(px[:3]) > 381
            row.append(opaque and light)
        rows.append(row)
    return rows


def main():
    names = sorted(f[:-4] for f in os.listdir(SOURCE) if f.endswith(".png"))
    header = ["// Made by scripts/make_icons.py from assets/icons/*.png: change the pictures, not this file.", "#pragma once", "",
              "#include <cstdint>", "", "namespace roro::icons {", "",
              "// One bit a pixel, the leftmost first, a row after another: what Canvas::drawBitmap takes.",
              f"constexpr int kSize = {SIZE};", ""]
    body = ["// Made by scripts/make_icons.py from assets/icons/*.png: change the pictures, not this file.", '#include "icons.h"', "",
            "namespace roro::icons {", ""]
    for name in names:
        rows = read_png(os.path.join(SOURCE, name + ".png"))
        if len(rows) != SIZE or len(rows[0]) != SIZE:
            sys.exit(f"{name}.png is {len(rows[0])} x {len(rows)}: an icon is {SIZE} x {SIZE}")
        ident = name.replace("-", "_")
        header.append(f"extern const uint8_t {ident}[{SIZE * SIZE // 8}];  // {name}.png")
        body.append(f"const uint8_t {ident}[{SIZE * SIZE // 8}] = {{")
        for row in rows:
            packed = [sum(0x80 >> i for i in range(8) if row[b * 8 + i]) for b in range(SIZE // 8)]
            body.append("    " + ", ".join(f"0x{v:02x}" for v in packed) + ",  // " + "".join("#" if v else "." for v in row))
        body += ["};", ""]
    header += ["", "}  // namespace roro::icons", ""]
    body += ["}  // namespace roro::icons", ""]
    out = {os.path.join(ROOT, "src", "ui", "icons.h"): "\n".join(header), os.path.join(ROOT, "src", "ui", "icons.cpp"): "\n".join(body)}
    if "--check" in sys.argv:
        stale = [os.path.relpath(p, ROOT) for p, text in out.items() if not os.path.exists(p) or open(p).read() != text]
        if stale:
            sys.exit("out of date: " + ", ".join(stale) + " (run scripts/make_icons.py)")
        print(f"{len(names)} icons, up to date")
        return
    for path, text in out.items():
        open(path, "w").write(text)
    print(f"{len(names)} icons written")


if __name__ == "__main__":
    main()