"""Assemble the Apple II 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__))
SOURCES = {"hgr": "hgr.s", "dhgr": "dhgr.s"}
_cache: dict[tuple, bytes] = {}

# How long the viewer holds the picture (see apple/viewer/awyt.i).
WAIT_MODES = {"forever": 0, "key": 1, "seconds": 2}
SS_WAITMODE = {"key": 1, "seconds": 2, "both": 3}


def build_slideshow_stub(n_images: int, advance: str = "both", seconds: int = 10,
                         loop: bool = True) -> bytes:
    """Assemble the Apple HGR slideshow boot loader (one 256-byte boot sector).

    Reads NIMAGES * 32 sectors into the $4000 buffer and cycles them; must fit a
    single boot sector since the Disk II ROM only loads sector 0.
    """
    import shutil as _sh
    if not _sh.which("xa"):
        raise AssemblerError("The 'xa' assembler was not found on PATH.")
    end_page = 0x40 + n_images * 0x20
    wrapper = (f"#define WAITMODE {SS_WAITMODE[advance]}\n"
               f"#define WAITSECS {max(0, min(255, int(seconds)))}\n"
               f"#define NIMAGES {n_images}\n"
               f"#define LOOPFLAG {1 if loop else 0}\n"
               f"#define ENDPAGE ${end_page:02X}\n"
               '#include "slideshow.s"\n')
    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", "-o", out, os.path.basename(wrap)],
                                  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:
                raw = f.read()
        finally:
            os.unlink(wrap)
    if len(raw) > 256:
        raise AssemblerError(
            f"Apple slideshow boot loader is {len(raw)} bytes, over the 256-byte "
            "boot sector")
    return raw


class AssemblerError(RuntimeError):
    pass


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


def assemble_stub(viewer_key: str, display: str = "forever", seconds: int = 0) -> bytes:
    waitmode = WAIT_MODES.get(display, 0)
    secs = max(0, min(255, int(seconds)))           # 8-bit delay counter
    key = (viewer_key, waitmode, secs)
    if key in _cache:
        return _cache[key]
    if not have_xa():
        raise AssemblerError("The 'xa' assembler was not found on PATH.")
    if not os.path.exists(os.path.join(VIEWER_DIR, SOURCES[viewer_key])):
        raise AssemblerError(f"viewer source missing: {SOURCES[viewer_key]}")

    # Wrapper sets options then includes the real source; run from VIEWER_DIR so
    # the source's #include "awyt.i" resolves (xa looks relative to cwd).
    wrapper = (f"#define WAITMODE {waitmode}\n"
               f"#define WAITSECS {secs}\n"
               f'#include "{SOURCES[viewer_key]}"\n')
    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", "-o", out, os.path.basename(wrap)],
                                  capture_output=True, text=True, cwd=VIEWER_DIR)
            if proc.returncode != 0:
                raise AssemblerError(
                    f"xa failed for {viewer_key}:\n{proc.stdout}{proc.stderr}")
            with open(out, "rb") as f:
                raw = f.read()
        finally:
            os.unlink(wrap)
    _cache[key] = raw
    return raw