"""Assemble the IIGS SHR boot/viewer with `xa` (origin $0800, raw bytes)."""
from __future__ import annotations

import os
import shutil
import subprocess
import tempfile

VIEWER_DIR = os.path.dirname(os.path.abspath(__file__))


class AssemblerError(RuntimeError):
    pass


def have_xa() -> bool:
    return shutil.which("xa") is not None


def assemble_boot() -> bytes:
    """Return the boot0 sector (<=256 bytes) that loads the SHR block + shows it."""
    if not have_xa():
        raise AssemblerError("The 'xa' assembler was not found on PATH.")
    with tempfile.TemporaryDirectory() as td:
        out = os.path.join(td, "v.bin")
        proc = subprocess.run(["xa", "-w", "-o", out, "iigs.s"],
                              capture_output=True, text=True, cwd=VIEWER_DIR)
        if proc.returncode != 0:
            raise AssemblerError(f"xa failed:\n{proc.stdout}{proc.stderr}")
        with open(out, "rb") as f:
            boot = f.read()
    if len(boot) > 256:
        raise AssemblerError(f"boot sector is {len(boot)} bytes (>256)")
    return boot


SS_WAITMODE = {"key": 1, "seconds": 2, "both": 3}


def _xa_wrapper(wrapper: str, what: str) -> bytes:
    if not have_xa():
        raise AssemblerError("The 'xa' assembler was not found on PATH.")
    with tempfile.TemporaryDirectory() as td:
        out = os.path.join(td, "v.bin")
        fd, wrap = tempfile.mkstemp(suffix=".s", prefix="_wrap_", dir=VIEWER_DIR)
        try:
            with os.fdopen(fd, "w") as f:
                f.write(wrapper)
            proc = subprocess.run(["xa", "-w", "-o", out, os.path.basename(wrap)],
                                  capture_output=True, text=True, cwd=VIEWER_DIR)
            if proc.returncode != 0:
                raise AssemblerError(f"xa failed for {what}:\n{proc.stdout}{proc.stderr}")
            with open(out, "rb") as f:
                return f.read()
        finally:
            os.unlink(wrap)


def build_slideshow(n_images: int, advance: str = "both", seconds: int = 10,
                    loop: bool = True, video: str = "ntsc"):
    """Assemble the two-stage IIGS SHR slideshow.

    Returns (boot_sector<=256B, stage2_bytes, stage2_pages).  The boot reads
    stage2 (stage2_pages sectors) into $0900, then the images into bank-0 $2000
    and banks them; stage2 cycles them onto the SHR screen.
    """
    speed = 8 if video != "pal" else 7          # ~1s delay outer count (fast IIGS)
    stage2 = _xa_wrapper(
        f"#define WAITMODE {SS_WAITMODE[advance]}\n"
        f"#define WAITSECS {max(0, min(255, int(seconds)))}\n"
        f"#define SPEED {speed}\n"
        f"#define NIMAGES {n_images}\n"
        f"#define LOOPFLAG {1 if loop else 0}\n"
        '#include "slideshow_stage2.s"\n', "iigs stage2")
    s2_pages = max(1, (len(stage2) + 255) // 256)
    boot = _xa_wrapper(
        f"#define NIMAGES {n_images}\n"
        f"#define S2END ${0x09 + s2_pages:02X}\n"
        '#include "slideshow_boot.s"\n', "iigs boot")
    if len(boot) > 256:
        raise AssemblerError(f"IIGS slideshow boot is {len(boot)} bytes (>256)")
    return boot, stage2, s2_pages