"""Assemble the BBC 6502 viewer with `xa` and patch in per-image parameters."""

from __future__ import annotations

import os
import shutil
import subprocess
import tempfile

VIEWER_DIR = os.path.dirname(os.path.abspath(__file__))
LOAD_ADDR = 0x1900               # DFS PAGE
WAIT_MODES = {"forever": 0, "key": 1, "seconds": 2}


class AssemblerError(RuntimeError):
    pass


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


def _xa(wrapper: str) -> bytes:
    if not have_xa():
        raise AssemblerError("The 'xa' (xa65) assembler was not found on PATH.\n"
                             "Install it with:  sudo apt install xa65")
    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:
                return f.read()
        finally:
            os.unlink(wrap)


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


def build_slideshow_viewer(bbc_mode: int, ncol: int, base: int, palettes,
                           advance: str = "both", seconds: int = 10,
                           loop: bool = True, video: str = "pal") -> bytes:
    """Return the multi-image BBC loader (origin $1900).

    ``palettes`` is one physical-colour list per image (each truncated/padded to
    ncol) -- emitted as the ss_pal table the loader indexes by slide; the screen
    base hex is patched into the OSCLI *LOAD string.
    """
    if not palettes:
        raise AssemblerError("a slideshow needs at least one image")
    rate = 60 if video == "ntsc" else 50
    flat = []
    for p in palettes:
        row = list(p[:ncol])
        flat += row + [0] * (ncol - len(row))
    table = ",".join(str(b & 0xFF) for b in flat)
    wrapper = (f"#define WAITMODE {SS_WAITMODE[advance]}\n"
               f"#define WAITSECS {max(0, int(seconds))}\n"
               f"#define RATE {rate}\n"
               f"#define NIMAGES {len(palettes)}\n"
               f"#define LOOPFLAG {1 if loop else 0}\n"
               f"#define MODE {bbc_mode}\n"
               f"#define NCOL {ncol}\n"
               '#include "slideshow.s"\n'
               "ss_pal:\n"
               f"        .byte {table}\n")
    raw = bytearray(_xa(wrapper))
    off = raw.find(b"LOAD 00 ")
    if off < 0:
        raise AssemblerError("could not locate the OSCLI string to patch")
    raw[off + 8:off + 12] = f"{base:04X}".encode("ascii")   # screen-base hex
    return bytes(raw)


def build_viewer(bbc_mode: int, ncol: int, physicals, base: int,
                 display: str = "forever", seconds: int = 0,
                 video: str = "pal") -> bytes:
    """Return the assembled loader (origin $1900) with the mode/palette/screen-base
    parameters patched in."""
    waitmode = WAIT_MODES.get(display, 0)
    rate = 60 if video == "ntsc" else 50         # bbcb is PAL (50 Hz)
    wrapper = (f"#define WAITMODE {waitmode}\n"
               f"#define WAITSECS {max(0, int(seconds))}\n"
               f"#define RATE {rate}\n"
               '#include "bbc.s"\n')
    raw = bytearray(_xa(wrapper))

    off = raw.find(b"LOAD IMG ")
    if off < 0:
        raise AssemblerError("could not locate the OSCLI string to patch")
    raw[off + 9:off + 13] = f"{base:04X}".encode("ascii")   # screen-base hex
    raw[off + 14] = bbc_mode & 0xFF                          # p_mode
    raw[off + 15] = ncol & 0xFF                              # p_ncol
    for i, p in enumerate(physicals[:8]):                    # p_pal
        raw[off + 16 + i] = p & 0xFF
    return bytes(raw)