"""
PlatformIO pre-build script: Convert pyxis-icon.svg to RGB565 PROGMEM header.

Generates lib/tdeck_ui/Hardware/TDeck/SplashImage.h containing a 320x240
pixel splash image as a PROGMEM byte array. Skips regeneration if the
header is already newer than the source SVG.

Requires: cairosvg, Pillow (gracefully skips if not installed)
"""

Import("env")

import os
import struct

SPLASH_WIDTH = 320
SPLASH_HEIGHT = 240
SVG_FILE = "pyxis-icon.svg"
HEADER_FILE = os.path.join("lib", "tdeck_ui", "Hardware", "TDeck", "SplashImage.h")
BG_COLOR = (0x1D, 0x1A, 0x1E)  # #1D1A1E — matches fill_screen in show_splash()


def rgb888_to_rgb565(r, g, b):
    """Convert 8-bit RGB to 16-bit RGB565 (big-endian bytes)."""
    rgb565 = ((r & 0xF8) << 8) | ((g & 0xFC) << 3) | (b >> 3)
    return struct.pack(">H", rgb565)


def should_regenerate(svg_path, header_path):
    """Return True if the header needs regeneration."""
    if not os.path.exists(header_path):
        return True
    return os.path.getmtime(svg_path) > os.path.getmtime(header_path)


project_dir = env.get("PROJECT_DIR", os.getcwd())
svg_path = os.path.join(project_dir, SVG_FILE)
header_path = os.path.join(project_dir, HEADER_FILE)

if not os.path.exists(svg_path):
    print(f"[generate_splash] {SVG_FILE} not found, skipping splash generation")
elif not should_regenerate(svg_path, header_path):
    print(f"[generate_splash] {HEADER_FILE} is up-to-date, skipping")
else:
    try:
        import cairosvg
        from PIL import Image
        import io
    except ImportError as e:
        print(f"[generate_splash] Missing dependency ({e}), skipping splash generation")
        print(f"[generate_splash] Install with: pip install cairosvg Pillow")
    else:
        print(f"[generate_splash] Rendering {SVG_FILE} -> {HEADER_FILE} ({SPLASH_WIDTH}x{SPLASH_HEIGHT} RGB565)")

        # Render SVG to PNG — scale to fit height, center horizontally
        png_data = cairosvg.svg2png(
            url=svg_path,
            output_width=SPLASH_HEIGHT,   # Square SVG scaled to screen height
            output_height=SPLASH_HEIGHT,
        )

        icon = Image.open(io.BytesIO(png_data)).convert("RGBA")

        # Composite onto full-screen background (handles transparency)
        bg = Image.new("RGBA", (SPLASH_WIDTH, SPLASH_HEIGHT), BG_COLOR + (255,))
        x_offset = (SPLASH_WIDTH - icon.width) // 2
        bg.paste(icon, (x_offset, 0), icon)
        img = bg.convert("RGB")

        # Convert to RGB565 big-endian byte array
        pixels = list(img.getdata())
        rgb565_bytes = bytearray()
        for r, g, b in pixels:
            rgb565_bytes.extend(rgb888_to_rgb565(r, g, b))

        # Write C header
        os.makedirs(os.path.dirname(header_path), exist_ok=True)

        with open(header_path, "w") as f:
            f.write("// AUTO-GENERATED by generate_splash.py — do not edit\n")
            f.write("#ifndef SPLASH_IMAGE_H\n")
            f.write("#define SPLASH_IMAGE_H\n\n")
            f.write("#include <Arduino.h>\n\n")
            f.write(f"#define SPLASH_WIDTH  {SPLASH_WIDTH}\n")
            f.write(f"#define SPLASH_HEIGHT {SPLASH_HEIGHT}\n")
            f.write(f"#define HAS_SPLASH_IMAGE 1\n\n")
            f.write(f"// {SPLASH_WIDTH}x{SPLASH_HEIGHT} RGB565 big-endian ({len(rgb565_bytes)} bytes)\n")
            f.write("// WARNING: static linkage — include from exactly ONE translation unit\n")
            f.write("static const uint8_t PROGMEM splash_image[] = {\n")

            # Write bytes, 16 per line
            for i in range(0, len(rgb565_bytes), 16):
                chunk = rgb565_bytes[i:i+16]
                hex_str = ", ".join(f"0x{b:02X}" for b in chunk)
                trailing = "," if i + 16 < len(rgb565_bytes) else ""
                f.write(f"    {hex_str}{trailing}\n")

            f.write("};\n\n")
            f.write("#endif // SPLASH_IMAGE_H\n")

        print(f"[generate_splash] Generated {len(rgb565_bytes)} bytes ({SPLASH_WIDTH}x{SPLASH_HEIGHT} RGB565)")