#!/usr/bin/env python3
"""Generates the app icons and the splash screen.

Written against nothing but the standard library on purpose: the icons are
part of the package, so regenerating them must not depend on Pillow being
installed or on a checked-in binary nobody can edit.

    python3 tools/make-assets.py

Everything is drawn supersampled and boxed down, which is what gives the
rounded corners and bar tops their edges.
"""

import os
import struct
import sys
import zlib

HERE = os.path.dirname(os.path.abspath(__file__))
ASSETS = os.path.join(HERE, os.pardir, "frontend", "assets")

# Same palette as the UI.
BACKDROP = (11, 14, 19)
TILE_TOP = (18, 32, 52)
TILE_BOTTOM = (13, 17, 25)
BAR_TOP = (74, 163, 255)
BAR_BOTTOM = (31, 77, 118)
ACCENT = (87, 217, 138)
TEXT = (200, 214, 232)

# Fraction of the drawing height each bar reaches. Reads as a level meter
# caught mid-song rather than a generic equaliser.
BARS = [0.34, 0.62, 0.95, 0.48, 0.78, 0.40]


class Canvas:
    """RGBA pixel buffer with the handful of primitives this needs."""

    def __init__(self, width, height, fill=(0, 0, 0, 0)):
        self.w = width
        self.h = height
        self.px = bytearray(fill * width * height) if len(fill) == 4 else None
        if self.px is None:
            self.px = bytearray((fill + (255,)) * width * height)

    def blend(self, x, y, colour, alpha=255):
        if x < 0 or y < 0 or x >= self.w or y >= self.h or alpha <= 0:
            return
        i = (y * self.w + x) * 4
        if alpha >= 255:
            self.px[i:i + 4] = bytes(colour) + b"\xff"
            return
        a = alpha / 255.0
        for c in range(3):
            self.px[i + c] = int(self.px[i + c] * (1 - a) + colour[c] * a)
        self.px[i + 3] = max(self.px[i + 3], alpha)

    def rect(self, x0, y0, x1, y1, colour):
        for y in range(max(0, int(y0)), min(self.h, int(y1))):
            for x in range(max(0, int(x0)), min(self.w, int(x1))):
                self.blend(x, y, colour)

    def rounded_rect(self, x0, y0, x1, y1, radius, top, bottom=None):
        """Filled rounded rectangle, optionally with a vertical gradient."""
        bottom = bottom if bottom is not None else top
        height = max(1, y1 - y0 - 1)
        for y in range(max(0, int(y0)), min(self.h, int(y1))):
            # Fractional edges mean y can sit just outside the span; clamping
            # keeps the gradient from extrapolating past either colour.
            t = min(1.0, max(0.0, (y - y0) / height))
            colour = tuple(int(top[c] + (bottom[c] - top[c]) * t) for c in range(3))
            for x in range(max(0, int(x0)), min(self.w, int(x1))):
                # Only the corners need the distance test.
                cx = None
                if x < x0 + radius and y < y0 + radius:
                    cx, cy = x0 + radius, y0 + radius
                elif x >= x1 - radius and y < y0 + radius:
                    cx, cy = x1 - radius - 1, y0 + radius
                elif x < x0 + radius and y >= y1 - radius:
                    cx, cy = x0 + radius, y1 - radius - 1
                elif x >= x1 - radius and y >= y1 - radius:
                    cx, cy = x1 - radius - 1, y1 - radius - 1
                if cx is not None:
                    dx, dy = x - cx, y - cy
                    if dx * dx + dy * dy > radius * radius:
                        continue
                self.blend(x, y, colour)

    def downsample(self, factor):
        """Box filter. This is the whole anti-aliasing strategy."""
        w, h = self.w // factor, self.h // factor
        out = Canvas(w, h)
        area = factor * factor
        for y in range(h):
            for x in range(w):
                r = g = b = a = 0
                for sy in range(factor):
                    row = ((y * factor + sy) * self.w + x * factor) * 4
                    for sx in range(factor):
                        i = row + sx * 4
                        r += self.px[i]
                        g += self.px[i + 1]
                        b += self.px[i + 2]
                        a += self.px[i + 3]
                i = (y * w + x) * 4
                out.px[i] = r // area
                out.px[i + 1] = g // area
                out.px[i + 2] = b // area
                out.px[i + 3] = a // area
        return out

    def paste(self, other, x0, y0):
        for y in range(other.h):
            for x in range(other.w):
                i = (y * other.w + x) * 4
                self.blend(x0 + x, y0 + y, tuple(other.px[i:i + 3]), other.px[i + 3])

    def write_png(self, path):
        raw = bytearray()
        stride = self.w * 4
        for y in range(self.h):
            raw.append(0)  # filter: none
            raw += self.px[y * stride:(y + 1) * stride]

        def chunk(kind, data):
            head = struct.pack(">I", len(data)) + kind + data
            return head + struct.pack(">I", zlib.crc32(kind + data) & 0xFFFFFFFF)

        png = b"\x89PNG\r\n\x1a\n"
        png += chunk(b"IHDR", struct.pack(">IIBBBBB", self.w, self.h, 8, 6, 0, 0, 0))
        png += chunk(b"IDAT", zlib.compress(bytes(raw), 9))
        png += chunk(b"IEND", b"")
        with open(path, "wb") as fh:
            fh.write(png)


# 5x7, only the letters the splash needs.
GLYPHS = {
    "A": ["01110", "10001", "10001", "11111", "10001", "10001", "10001"],
    "C": ["01110", "10001", "10000", "10000", "10000", "10001", "01110"],
    "D": ["11110", "10001", "10001", "10001", "10001", "10001", "11110"],
    "I": ["11111", "00100", "00100", "00100", "00100", "00100", "11111"],
    "O": ["01110", "10001", "10001", "10001", "10001", "10001", "01110"],
    "P": ["11110", "10001", "10001", "11110", "10000", "10000", "10000"],
    "U": ["10001", "10001", "10001", "10001", "10001", "10001", "01110"],
    " ": ["00000"] * 7,
}


def text_width(text, scale, spacing):
    return len(text) * (5 * scale + spacing) - spacing


def draw_text(canvas, text, x0, y0, scale, spacing, colour):
    x = x0
    for ch in text:
        rows = GLYPHS[ch]
        for ry, row in enumerate(rows):
            for rx, on in enumerate(row):
                if on == "1":
                    canvas.rect(x + rx * scale, y0 + ry * scale,
                                x + (rx + 1) * scale, y0 + (ry + 1) * scale, colour)
        x += 5 * scale + spacing


def render_tile(size, supersample=4):
    """The logo: a rounded tile with a level meter on it."""
    s = size * supersample
    c = Canvas(s, s)
    radius = int(s * 0.22)
    c.rounded_rect(0, 0, s, s, radius, TILE_TOP, TILE_BOTTOM)

    margin = s * 0.18
    inner_w = s - margin * 2
    inner_h = s - margin * 2
    gap = inner_w / (len(BARS) * 4)
    bar_w = (inner_w - gap * (len(BARS) - 1)) / len(BARS)
    bar_radius = max(1, int(bar_w * 0.35))
    base = s - margin

    for i, height in enumerate(BARS):
        x0 = margin + i * (bar_w + gap)
        top = base - inner_h * height
        colour_top = ACCENT if height > 0.9 else BAR_TOP
        c.rounded_rect(x0, top, x0 + bar_w, base, bar_radius, colour_top, BAR_BOTTOM)

    return c.downsample(supersample)


def render_splash(width=1920, height=1080):
    c = Canvas(width, height, BACKDROP)
    tile = render_tile(300, supersample=2)
    c.paste(tile, (width - tile.w) // 2, height // 2 - 260)

    scale, spacing = 10, 10
    label = "AUDIO CAP"
    draw_text(c, label, (width - text_width(label, scale, spacing)) // 2,
              height // 2 + 120, scale, spacing, TEXT)
    return c


def main():
    os.makedirs(ASSETS, exist_ok=True)
    targets = [
        ("icon.png", lambda: render_tile(80)),
        ("largeIcon.png", lambda: render_tile(130)),
        ("splash.png", render_splash),
    ]
    for name, build in targets:
        path = os.path.join(ASSETS, name)
        build().write_png(path)
        print("wrote %s (%d bytes)" % (os.path.relpath(path), os.path.getsize(path)))
    return 0


if __name__ == "__main__":
    sys.exit(main())