"""Generate the floor texture and music used by exercises/basics.py (no licensed sources)."""
import array
import binascii
import math
from pathlib import Path
import random
import struct
import wave
import zlib

ROOT = Path(__file__).resolve().parents[1]


def save_png(path, size, pixels):
    def chunk(kind, data):
        return struct.pack(">I", len(data)) + kind + data + struct.pack(">I", binascii.crc32(kind + data) & 0xffffffff)
    path.parent.mkdir(parents=True, exist_ok=True)
    path.write_bytes(b"\x89PNG\r\n\x1a\n" +
                     chunk(b"IHDR", struct.pack(">IIBBBBB", size, size, 8, 2, 0, 0, 0)) +
                     chunk(b"IDAT", zlib.compress(pixels, 9)) + chunk(b"IEND", b""))


def floor_tiles(path, size=512, tiles=4, grout=5):
    """Slate tiles that repeat seamlessly: 4x4 in one texture, each with its own shade."""
    rng = random.Random(7)
    step = size // tiles
    shades = [[rng.uniform(0.75, 1.15) for _ in range(tiles)] for _ in range(tiles)]
    pixels = bytearray()
    for y in range(size):
        pixels.append(0)
        for x in range(size):
            if x % step < grout or y % step < grout:
                pixels += bytes((24, 24, 26))
            else:
                shade = shades[y // step][x // step] * rng.uniform(0.94, 1.06)
                pixels += bytes(min(255, int(value * shade)) for value in (92, 100, 112))
    save_png(path, size, bytes(pixels))


def music(path, seconds=8.0, rate=44100):
    """Minor-key pad, bass and arpeggio: two bars at 120 BPM, fading out at the end."""
    chords = [(220.00, 261.63, 329.63), (174.61, 220.00, 261.63),
              (261.63, 329.63, 392.00), (196.00, 246.94, 293.66)]
    beat = 0.5
    samples = array.array("h")
    for index in range(int(seconds * rate)):
        time = index / rate
        chord = chords[int(time / (beat * 4)) % len(chords)]
        pad = sum(math.sin(2 * math.pi * frequency * time) for frequency in chord) / 3
        bass = math.sin(2 * math.pi * chord[0] / 2 * time)
        step = int(time / (beat / 2))
        note = chord[step % 3] * 2
        arpeggio = math.sin(2 * math.pi * note * time) * math.exp(-6 * (time - step * beat / 2))
        kick_time = time % beat if int(time / beat) % 2 == 0 else 1.0
        kick = math.sin(2 * math.pi * 60 * kick_time) * math.exp(-18 * kick_time)
        fade = min(1.0, time / 0.3, (seconds - time) / 1.0)
        value = 0.28 * pad + 0.22 * bass + 0.2 * arpeggio + 0.3 * kick
        samples.append(int(32767 * 0.8 * fade * max(-1.0, min(1.0, value))))
    path.parent.mkdir(parents=True, exist_ok=True)
    with wave.open(str(path), "wb") as target:
        target.setnchannels(1)
        target.setsampwidth(2)
        target.setframerate(rate)
        target.writeframes(samples.tobytes())


if __name__ == "__main__":
    floor_tiles(ROOT / "source_assets/textures/floor_tiles.png")
    music(ROOT / "source_assets/audio/basics_music.wav")