"""CUPS service management, USB fallback, and consumable state tracking."""

from __future__ import annotations

import contextlib
import fcntl
import importlib
import json
import logging
import os
from pathlib import Path
import re
import shutil
import subprocess
import time
from typing import TYPE_CHECKING

from python_pkg.brother_printer._query import (
    printer_info_from_cups,
    run_command_text,
)
from python_pkg.brother_printer.constants import (
    _CUPS_REASONS_TO_STATUS,
    _CUPS_STATE_TO_STATUS,
    _ERROR_REASON_MAP,
    BROTHER_USB_VENDOR_ID,
    CONSUMABLE_STATE_DIR,
    CUPS_PAGE_LOG_PATH,
    DERIVED_CUPS_ERROR,
    DERIVED_TONER_END,
    DERIVED_TONER_LOW,
    DRUM_RATED_PAGES,
    GREEN,
    PAGE_DROP_WARN_THRESHOLD,
    RESET,
    TONER_RATED_PAGES,
    _out,
)
from python_pkg.brother_printer.data_classes import (
    PageCountEstimate,
    PageDeliveryCheck,
    USBPortStatus,
    USBResult,
)

if TYPE_CHECKING:
    import types

logger = logging.getLogger(__name__)

CUPS_PAGE_LOG = Path(CUPS_PAGE_LOG_PATH)
CONSUMABLE_STATE_FILE = Path.home() / CONSUMABLE_STATE_DIR / "state.json"

# state.json schema versions. Version 1 (implicit, no "schema" key) recorded
# replacement baselines as CUPS page-log counts; version 2 records them on the
# printer's own lifetime counter. See _migrate_state_to_printer_scale.
STATE_SCHEMA_CUPS_SCALE = 1
STATE_SCHEMA_PRINTER_SCALE = 2

# Directory holding the usblp device nodes, and the ioctl that reads the
# printer's IEEE 1284 status byte from one without disturbing the device.
USB_PRINTER_DEV_GLOB_DIR = "/dev/usb"
LPGETSTATUS = 0x060B


def _import_or_raise(name: str) -> types.ModuleType:
    """Import a module or raise ImportError with a helpful message."""
    try:
        return importlib.import_module(name)
    except ImportError as e:
        msg = f"{name} is required but not installed"
        raise ImportError(msg) from e


# ── pyusb device info ────────────────────────────────────────────────


def _get_pyusb_device_info() -> dict[str, str]:
    """Get Brother USB printer info via pyusb (no interface claim needed)."""
    try:
        usb_core = _import_or_raise("usb.core")

        dev = usb_core.find(idVendor=BROTHER_USB_VENDOR_ID)
        if dev is None:
            return {}
    except (ImportError, OSError, ValueError):
        return {}
    return {
        "product": dev.product or "",
        "serial": dev.serial_number or "",
    }


# ── CUPS service control ────────────────────────────────────────────


def is_cups_scheduler_running() -> bool:
    """Check if the CUPS scheduler is currently running."""
    lpstat = shutil.which("lpstat")
    if not lpstat:
        return False
    try:
        r = subprocess.run(
            [lpstat, "-r"],
            capture_output=True,
            text=True,
            timeout=3,
            check=False,
        )
        return (
            "is running" in r.stdout.lower() and "not running" not in r.stdout.lower()
        )
    except (subprocess.TimeoutExpired, OSError):
        return False


def start_cups() -> bool:
    """Start CUPS service, socket, and path units. Returns True on success."""
    systemctl = shutil.which("systemctl")
    if not systemctl:
        return False
    try:
        subprocess.run(
            [systemctl, "start", "cups.service", "cups.socket", "cups.path"],
            timeout=15,
            check=True,
        )
    except (subprocess.TimeoutExpired, subprocess.CalledProcessError, OSError):
        return False
    for _ in range(10):
        if is_cups_scheduler_running():
            return True
        time.sleep(1)
    return False


def _ensure_cups_running() -> bool:
    """Make sure CUPS is running, starting it if necessary."""
    if is_cups_scheduler_running():
        return True
    return start_cups()


# ── USB port status via pyusb ────────────────────────────────────────


def _port_status_from_byte(port_byte: int) -> USBPortStatus:
    """Decode a USB printer-class port status byte."""
    return USBPortStatus(
        paper_empty=bool(port_byte & 0x20),
        online=bool(port_byte & 0x10),
        # nFault is active low: the bit is set when there is NO fault.
        error=not bool(port_byte & 0x08),
        raw_byte=port_byte,
    )


def _port_status_via_usblp() -> USBPortStatus | None:
    """Read port status through the usblp device node. No side effects.

    The LPGETSTATUS ioctl returns the same byte as the USB control transfer
    but costs nothing: no stopping CUPS, no device reset, no driver detach.
    Returns None when the node is absent or busy.
    """
    dev_path = Path(USB_PRINTER_DEV_GLOB_DIR)
    devices = sorted(dev_path.glob("lp*")) if dev_path.is_dir() else []
    if not devices:
        return None
    try:
        # O_NONBLOCK: never hang here, the printer may be mid-job.
        fd = os.open(str(devices[0]), os.O_RDONLY | os.O_NONBLOCK)
    except OSError:
        logger.debug("opening %s failed", devices[0], exc_info=True)
        return None
    try:
        buf = bytearray(4)
        fcntl.ioctl(fd, LPGETSTATUS, buf)
    except OSError:
        logger.debug("usblp LPGETSTATUS failed", exc_info=True)
        return None
    finally:
        os.close(fd)
    return _port_status_from_byte(int.from_bytes(buf, "little") & 0xFF)


def _cups_is_busy(cups_state: str) -> bool:
    """Report whether CUPS is currently driving the printer."""
    return "processing" in cups_state.lower() or "printing" in cups_state.lower()


def _query_usb_port_status_raw(cups_state: str = "") -> USBPortStatus | None:
    """Query the printer's port status without disturbing it.

    Prefers the usblp ioctl, which is free. Falls back to a pyusb control
    transfer only when CUPS is idle: claiming the USB interface mid-job kills
    the print, and an earlier version of this function did exactly that - it
    stopped CUPS and reset the device just to read a status byte, destroying
    the job it was trying to report on.

    Args:
        cups_state: CUPS printer-state text, used to detect an active job.

    Returns:
        The port status, or None when it cannot be read harmlessly.
    """
    status = _port_status_via_usblp()
    if status is not None:
        return status

    if _cups_is_busy(cups_state):
        # A job is running and owns the device. Reading the status is not worth
        # killing the job for; the caller falls back to what CUPS reports.
        logger.debug("skipping USB probe: CUPS is printing")
        return None

    try:
        usb_core = _import_or_raise("usb.core")
        usb_util = _import_or_raise("usb.util")
    except ImportError:
        return None

    dev = usb_core.find(idVendor=BROTHER_USB_VENDOR_ID)
    if dev is None:
        return None

    detached = False
    try:
        try:
            if dev.is_kernel_driver_active(0):
                dev.detach_kernel_driver(0)
                detached = True
        except (usb_core.USBError, NotImplementedError):
            pass

        usb_util.claim_interface(dev, 0)
        try:
            # USB Printer Class GET_PORT_STATUS (bRequest=0x01)
            raw = dev.ctrl_transfer(0xA1, 0x01, 0, 0, 1, timeout=5000)
            return _port_status_from_byte(raw[0])
        finally:
            usb_util.release_interface(dev, 0)
            if detached:
                # Give usblp its device back, or /dev/usb/lp* stays missing and
                # every later run is stuck in this fallback path.
                with contextlib.suppress(Exception):
                    dev.attach_kernel_driver(0)
            usb_util.dispose_resources(dev)
    except (OSError, ValueError):
        logger.debug("USB port status query failed", exc_info=True)
        return None


# ── Consumable state management ──────────────────────────────────────


def _get_cups_total_pages() -> int:
    """Parse CUPS page_log to get total pages printed (deduplicated by job)."""
    if not CUPS_PAGE_LOG.exists():
        return 0
    try:
        text = CUPS_PAGE_LOG.read_text(encoding="utf-8", errors="replace")
    except OSError:
        return 0
    jobs: dict[str, int] = {}
    for line in text.splitlines():
        match = re.search(r"\s(\d+)\s+\[.*?\]\s+total\s+(\d+)", line)
        if match:
            job_id = match.group(1)
            pages = int(match.group(2))
            jobs[job_id] = max(jobs.get(job_id, 0), pages)
    return sum(jobs.values())


def _load_consumable_state() -> dict[str, int]:
    """Load consumable replacement state from disk."""
    defaults: dict[str, int] = {
        "toner_replaced_at": 0,
        "drum_replaced_at": 0,
        "schema": STATE_SCHEMA_CUPS_SCALE,
        # Snapshot of both counters at the last successful printer read, used to
        # spot dropped pages and to place a CUPS-log figure on the printer's
        # scale when the printer cannot be reached.
        "last_printer_count": 0,
        "last_cups_total": 0,
    }
    if not CONSUMABLE_STATE_FILE.exists():
        return defaults
    try:
        data = json.loads(
            CONSUMABLE_STATE_FILE.read_text(encoding="utf-8"),
        )
        return {
            "toner_replaced_at": int(data.get("toner_replaced_at", 0)),
            "drum_replaced_at": int(data.get("drum_replaced_at", 0)),
            "schema": int(data.get("schema", STATE_SCHEMA_CUPS_SCALE)),
            "last_printer_count": int(data.get("last_printer_count", 0)),
            "last_cups_total": int(data.get("last_cups_total", 0)),
        }
    except (OSError, json.JSONDecodeError, ValueError, TypeError):
        return defaults


def _migrate_state_to_printer_scale(
    state: dict[str, int],
    printer_total: int,
) -> dict[str, int]:
    """Rebase replacement baselines from the CUPS page log onto the printer's counter.

    Baselines written before this migration counted pages the CUPS log had seen,
    which undercounts the printer's own lifetime counter by however many pages
    were printed without CUPS logging them.  Shift each baseline by the gap
    measured now, so "pages since replacement" - and therefore the reported
    percentages - stay put across the switch.

    A zero baseline means "never replaced" rather than "replaced at page zero",
    so it is left alone: on the printer's scale it already means "as old as the
    printer", which is the truthful reading.

    Args:
        state: Loaded state, possibly still on the CUPS page-log scale.
        printer_total: Lifetime page count from the printer's own counter.

    Returns:
        State on the printer's scale, migrated at most once.
    """
    if state.get("schema", STATE_SCHEMA_CUPS_SCALE) >= STATE_SCHEMA_PRINTER_SCALE:
        return state
    offset = printer_total - _get_cups_total_pages()
    migrated = dict(state)
    migrated["schema"] = STATE_SCHEMA_PRINTER_SCALE
    if offset > 0:
        for key in ("toner_replaced_at", "drum_replaced_at"):
            if state[key] > 0:
                migrated[key] = state[key] + offset
    _save_consumable_state(migrated)
    return migrated


def _save_consumable_state(state: dict[str, int]) -> None:
    """Persist consumable replacement state to disk."""
    CONSUMABLE_STATE_FILE.parent.mkdir(parents=True, exist_ok=True)
    CONSUMABLE_STATE_FILE.write_text(
        json.dumps(state, indent=2) + "\n",
        encoding="utf-8",
    )


def reset_consumable(name: str, printer_total: int = 0) -> None:
    """Record current page count as replacement point for a consumable.

    Args:
        name: Consumable to reset, "toner" or "drum".
        printer_total: Lifetime count from the printer's own counter. Falls back
            to the CUPS page log when zero, i.e. the printer was unreachable.
    """
    total = printer_total if printer_total > 0 else _get_cups_total_pages()
    state = _load_consumable_state()
    key = f"{name}_replaced_at"
    state[key] = total
    # Baselines written here are already on the printer's scale, so mark the
    # state migrated to stop the rebase shifting them a second time.
    if printer_total > 0:
        state["schema"] = STATE_SCHEMA_PRINTER_SCALE
    _save_consumable_state(state)
    _out(f"{GREEN}✓ {name.capitalize()} counter reset at page count {total}.{RESET}")
    _out(f"  State saved to {CONSUMABLE_STATE_FILE}")


def _cups_total_on_printer_scale(state: dict[str, int]) -> int:
    """Express the CUPS page-log count on the printer's counter scale.

    Replacement baselines are stored against the printer's lifetime counter, so
    comparing a raw CUPS figure against them subtracts two different scales. The
    CUPS log runs behind the printer (it only sees jobs it printed itself), so
    the raw number reads too low - low enough to go negative and clamp to zero,
    which reported a spent cartridge as 100% full.

    Shift by the gap measured at the last successful printer read. It is an
    approximation, which is why callers flag the estimate as approximate.

    Args:
        state: Loaded consumable state holding the last counter snapshot.

    Returns:
        The CUPS total shifted onto the printer's scale, or the raw total when
        no snapshot exists to shift it by.
    """
    cups_total = _get_cups_total_pages()
    if cups_total <= 0:
        return 0
    offset = state["last_printer_count"] - state["last_cups_total"]
    if state["last_printer_count"] <= 0 or offset <= 0:
        return cups_total
    return cups_total + offset


def check_page_delivery(printer_total: int, *, queue_idle: bool) -> PageDeliveryCheck:
    """Compare pages CUPS logged against pages the printer actually counted.

    Only meaningful between jobs: mid-job, CUPS has logged pages the printer has
    not yet pulled off the wire, which would look identical to dropping them.
    Records a fresh snapshot of both counters whenever it runs cleanly.

    Args:
        printer_total: Lifetime count from the printer's own counter.
        queue_idle: False when a job is queued or printing, which makes any
            comparison meaningless.

    Returns:
        The comparison. suspected is True only when CUPS claims materially more
        pages than the printer recorded.
    """
    check = PageDeliveryCheck()
    if printer_total <= 0 or not queue_idle:
        return check
    state = _load_consumable_state()
    cups_total = _get_cups_total_pages()
    last_printer = state["last_printer_count"]
    last_cups = state["last_cups_total"]

    _snapshot_counters(state, printer_total, cups_total)

    if last_printer <= 0 or last_cups <= 0:
        # No baseline yet: this run establishes one.
        return check
    printer_delta = printer_total - last_printer
    cups_delta = cups_total - last_cups
    if printer_delta < 0 or cups_delta < 0:
        # Counter reset or the page log rotated; nothing to conclude.
        return check
    check.cups_pages = cups_delta
    check.printer_pages = printer_delta
    check.dropped = cups_delta - printer_delta
    check.suspected = check.dropped >= PAGE_DROP_WARN_THRESHOLD
    return check


def _snapshot_counters(
    state: dict[str, int],
    printer_total: int,
    cups_total: int,
) -> None:
    """Persist where both counters stood, for the next run to compare against."""
    if (
        state["last_printer_count"] == printer_total
        and state["last_cups_total"] == cups_total
    ):
        return
    updated = dict(state)
    updated["last_printer_count"] = printer_total
    updated["last_cups_total"] = cups_total
    _save_consumable_state(updated)


def estimate_consumable_life(printer_total: int = 0) -> PageCountEstimate:
    """Estimate toner/drum life from pages printed since the last replacement.

    Args:
        printer_total: Lifetime count from @PJL INFO PAGECOUNT. When zero the
            printer could not be asked, so the CUPS page log stands in and the
            estimate is flagged approximate.

    Returns:
        The estimate; total_pages is zero when no counter could be read at all.
    """
    approximate = printer_total <= 0
    state = _load_consumable_state()
    total = _cups_total_on_printer_scale(state) if approximate else printer_total
    if total <= 0:
        return PageCountEstimate()
    if not approximate:
        state = _migrate_state_to_printer_scale(state, total)
    toner_pages = max(0, total - state["toner_replaced_at"])
    drum_pages = max(0, total - state["drum_replaced_at"])
    toner_pct = max(0, 100 - (toner_pages * 100 // TONER_RATED_PAGES))
    drum_pct = max(0, 100 - (drum_pages * 100 // DRUM_RATED_PAGES))
    return PageCountEstimate(
        total_pages=total,
        toner_pages=toner_pages,
        drum_pages=drum_pages,
        toner_pct_remaining=toner_pct,
        drum_pct_remaining=drum_pct,
        approximate=approximate,
        toner_exhausted=toner_pages >= TONER_RATED_PAGES,
        toner_low=toner_pages >= TONER_RATED_PAGES * 80 // 100,
        drum_near_end=drum_pages >= DRUM_RATED_PAGES * 90 // 100,
    )


# ── IPP / CUPS attribute queries ────────────────────────────────────


def _parse_ipp_attributes(output: str) -> dict[str, str]:
    """Parse ipptool verbose output into an attribute dict."""
    attrs: dict[str, str] = {}
    for line in output.splitlines():
        match = re.match(r"\s+(\S+)\s+\([^)]+\)\s+=\s+(.*)", line)
        if match:
            attrs[match.group(1)] = match.group(2).strip()
    return attrs


def _get_cups_ipp_status(printer_name: str) -> dict[str, str]:
    """Query printer attributes via CUPS IPP using ipptool."""
    ipptool_path = shutil.which("ipptool")
    if not ipptool_path:
        return {}
    uri = f"ipp://localhost/printers/{printer_name}"
    try:
        r = subprocess.run(
            [ipptool_path, "-tv", uri, "get-printer-attributes.test"],
            capture_output=True,
            text=True,
            timeout=10,
            check=False,
        )
        return _parse_ipp_attributes(r.stdout)
    except (subprocess.TimeoutExpired, subprocess.SubprocessError, OSError):
        return {}


def _get_cups_economode(printer_name: str) -> str:
    """Query toner save mode setting via lpoptions."""
    lpoptions_path = shutil.which("lpoptions")
    if not lpoptions_path:
        return ""
    command = [lpoptions_path, "-p", printer_name, "-l"]
    for line in run_command_text(command).splitlines():
        if "conomode" in line.lower():
            match = re.search(r"\*(\w+)", line)
            if match:
                return "ON" if match.group(1).lower() == "true" else "OFF"
    return ""


# ── Status code mapping ──────────────────────────────────────────────


def _map_cups_to_status_code(state: str, reasons: str) -> str:
    """Map CUPS state + reasons to a Brother PJL status code string."""
    for keyword, code in _CUPS_REASONS_TO_STATUS.items():
        if keyword in reasons.lower():
            return str(code)
    clean_state = re.sub(r"\(.*\)", "", state).strip().lower()
    return str(_CUPS_STATE_TO_STATUS.get(clean_state, 10001))


def _cups_reasons_to_error(cups_reasons: str) -> tuple[str, str]:
    """Map CUPS reason keywords to a (status_code, display) pair."""
    reasons_lower = cups_reasons.lower()
    for keywords, code, display in _ERROR_REASON_MAP:
        if any(kw in reasons_lower for kw in keywords):
            return code, display
    # Nothing recognised. Show what CUPS actually said rather than a bare
    # "Printer Error", which tells the reader nothing they can act on.
    detail = cups_reasons.strip()
    if detail and detail.lower() not in {"none", ""}:
        return DERIVED_CUPS_ERROR, f"Printer Error (CUPS reports: {detail})"
    return DERIVED_CUPS_ERROR, "Printer Error (CUPS gave no reason)"


def _port_status_to_status_code(
    ps: USBPortStatus,
    cups_reasons: str,
) -> tuple[str, str]:
    """Map USB port status + CUPS reasons to (status_code, display)."""
    # The port status exposes only paper_empty/error/online bits, so anything
    # more specific than "out of paper" has to come from the CUPS reasons -
    # an error bit alone does not tell us the cover is open.
    if ps.paper_empty:
        return "41000", "No Paper"
    if ps.error:
        return _cups_reasons_to_error(cups_reasons)
    if not ps.online:
        return "10002", "Offline / Sleep"
    return "", ""


# ── CUPS printer name discovery ──────────────────────────────────────


def find_cups_printer_name() -> str:
    """Find the CUPS queue name for a Brother printer."""
    lpstat_path = shutil.which("lpstat")
    if not lpstat_path:
        return ""
    for line in run_command_text([lpstat_path, "-v"]).splitlines():
        if "brother" in line.lower():
            match = re.match(r"device for (\S+):", line)
            if match:
                return match.group(1)
    return ""


# ── CUPS-based USB fallback query ────────────────────────────────────


def query_usb_via_cups() -> USBResult:
    """Query USB printer status through CUPS when /dev/usb/lp* is unavailable."""
    _ensure_cups_running()
    printer_name = find_cups_printer_name()
    if not printer_name:
        return USBResult(
            error="No USB printer device at /dev/usb/lp*"
            " (usblp module not available)"
            " and no Brother printer found in CUPS.",
        )

    pyusb_info = _get_pyusb_device_info()
    cups_info = printer_info_from_cups()

    result = USBResult(
        device="cups",
        product=(
            pyusb_info.get("product")
            or cups_info.get("product")
            or "Brother Laser Printer"
        ),
        serial=pyusb_info.get("serial") or cups_info.get("serial", ""),
    )

    ipp = _get_cups_ipp_status(printer_name)
    state = ipp.get("printer-state", "")
    reasons = ipp.get("printer-state-reasons", "none")
    result.economode = _get_cups_economode(printer_name)

    port_status = _query_usb_port_status_raw(state)
    if port_status is not None:
        result.port_status = port_status
        hw_code, hw_display = _port_status_to_status_code(
            port_status,
            reasons,
        )
        if hw_code:
            result.status_code = hw_code
            result.display = hw_display
            result.online = "TRUE" if port_status.online else "FALSE"
            return result
        estimate = estimate_consumable_life()
        if estimate.toner_exhausted:
            result.status_code = DERIVED_TONER_END
            result.display = "Toner End (estimated from page count)"
            result.online = "TRUE"
            return result
        if estimate.toner_low:
            result.status_code = DERIVED_TONER_LOW
            result.display = "Toner Low (estimated from page count)"
            result.online = "TRUE"
            return result
        result.status_code = _map_cups_to_status_code(state, reasons)
        result.display = ipp.get("printer-state-message", "")
        result.online = "TRUE"
        return result

    result.status_code = _map_cups_to_status_code(state, reasons)
    result.display = ipp.get("printer-state-message", "")
    result.online = "TRUE" if state.lower() in {"idle", "processing"} else "FALSE"

    return result