bambuddy/backend/app/services/usage_tracker.py

"""Automatic filament consumption tracking.

Captures AMS tray remain% at print start, then computes consumption
deltas at print complete to update spool weight_used and last_used.

Primary tracking uses 3MF slicer estimates (precise per-filament data).
AMS remain% delta is the fallback for trays not covered by 3MF data.
"""

import json
import logging
from dataclasses import dataclass, field
from datetime import datetime, timezone

from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

from backend.app.models.spool import Spool
from backend.app.models.spool_assignment import SpoolAssignment
from backend.app.models.spool_usage_history import SpoolUsageHistory

logger = logging.getLogger(__name__)


def _decode_mqtt_mapping(mapping_raw: list | None) -> list[int] | None:
    """Decode MQTT mapping field (snow-encoded) to bambuddy global tray IDs.

    The printer's MQTT mapping field is an array indexed by slicer filament slot
    (0-based). Each value uses snow encoding: ams_hw_id * 256 + local_slot.
    65535 means unmapped.

    Returns a list of bambuddy global tray IDs (or -1 for unmapped), or None if
    no valid mappings found.
    """
    if not isinstance(mapping_raw, list) or not mapping_raw:
        return None

    result = []
    for value in mapping_raw:
        if not isinstance(value, int) or value >= 65535:
            result.append(-1)
            continue

        ams_hw_id = value >> 8
        slot = value & 0xFF

        if 0 <= ams_hw_id <= 3:
            # Regular AMS: sequential global ID
            result.append(ams_hw_id * 4 + (slot & 0x03))
        elif 128 <= ams_hw_id <= 135:
            # AMS-HT: global ID is the hardware ID (one slot per unit)
            result.append(ams_hw_id)
        elif ams_hw_id in (254, 255):
            # External spool
            result.append(254 if slot != 255 else 255)
        else:
            result.append(-1)

    # Only return if at least one valid mapping exists
    if all(v < 0 for v in result):
        return None

    return result


def _match_slots_by_color(
    filament_usage: list[dict],
    ams_raw: dict | list | None,
) -> list[int] | None:
    """Match 3MF filament slots to AMS trays by color.

    Fallback mapping for printers that don't provide the MQTT mapping field
    or request topic subscription (e.g. A1, A1 Mini, P1S, P2S).

    Compares the 3MF slicer filament color (per slot) against each AMS tray's
    color to find a unique match. Only returns a mapping if every used slot
    matches exactly one tray (no ambiguity).

    Args:
        filament_usage: List of 3MF slot dicts with 'slot_id', 'color', 'type'
        ams_raw: raw_data["ams"] dict or list from printer state

    Returns:
        List of global tray IDs indexed by slicer slot (0-based), or None.
    """
    if not filament_usage or not ams_raw:
        return None

    ams_data = ams_raw.get("ams", []) if isinstance(ams_raw, dict) else ams_raw if isinstance(ams_raw, list) else []
    if not ams_data:
        return None

    # Build map of normalized color → list of global tray IDs
    color_to_trays: dict[str, list[int]] = {}
    for ams_unit in ams_data:
        ams_id = int(ams_unit.get("id", 0))
        for tray in ams_unit.get("tray", []):
            tray_id = int(tray.get("id", 0))
            tray_color = tray.get("tray_color", "")
            tray_type = tray.get("tray_type", "")
            if not tray_color or not tray_type:
                continue
            # Normalize AMS color: strip alpha (last 2 chars), lowercase
            norm = tray_color[:6].lower() if len(tray_color) >= 6 else tray_color.lower()
            if ams_id >= 128:
                global_id = ams_id  # AMS-HT
            else:
                global_id = ams_id * 4 + tray_id
            color_to_trays.setdefault(norm, []).append(global_id)

    if not color_to_trays:
        return None

    # Find max slot_id to size the result array
    max_slot = max(u.get("slot_id", 0) for u in filament_usage)
    if max_slot <= 0:
        return None

    result = [-1] * max_slot
    used_trays: set[int] = set()

    for usage in filament_usage:
        slot_id = usage.get("slot_id", 0)
        if slot_id <= 0:
            continue
        slot_color = usage.get("color", "").lstrip("#").lower()
        if len(slot_color) < 6:
            return None  # Can't match without a valid color

        slot_color = slot_color[:6]  # Strip alpha if present
        candidates = color_to_trays.get(slot_color, [])
        # Filter out trays already claimed by another slot
        available = [t for t in candidates if t not in used_trays]

        if len(available) != 1:
            # Ambiguous (multiple trays with same color) or no match
            return None

        result[slot_id - 1] = available[0]
        used_trays.add(available[0])

    # Only return if at least one valid mapping exists
    if all(v < 0 for v in result):
        return None

    logger.info("[UsageTracker] Color-matched slot_to_tray: %s", result)
    return result


@dataclass
class PrintSession:
    printer_id: int
    print_name: str
    started_at: datetime
    tray_remain_start: dict[tuple[int, int], int] = field(default_factory=dict)
    # tray_now at print start (correct value, unlike at completion where it's 255)
    tray_now_at_start: int = -1
    # Snapshot of spool assignments at print start: {(ams_id, tray_id): spool_id}
    # Prevents usage loss when on_ams_change unlinks a spool mid-print
    spool_assignments: dict[tuple[int, int], int] = field(default_factory=dict)


# Module-level storage, keyed by printer_id
_active_sessions: dict[int, PrintSession] = {}


def _to_epoch_seconds(value: datetime | None) -> float | None:
    """Convert datetime to epoch seconds, assuming UTC for naive values."""
    if value is None:
        return None
    dt = value
    if dt.tzinfo is None:
        dt = dt.replace(tzinfo=timezone.utc)
    return dt.timestamp()


async def _resolve_spool_id_for_tray(
    printer_id: int,
    ams_id: int,
    tray_id: int,
    db: AsyncSession,
    spool_assignments_snapshot: dict[tuple[int, int], int] | None = None,
    print_started_at: datetime | None = None,
) -> int | None:
    """Resolve spool ID for a tray with safe support for mid-print reassignment.

    Resolution order:
    1. If snapshot exists and live assignment changed *during this print*, use live spool.
    2. Otherwise use snapshot spool when available.
    3. Fall back to live assignment.
    """
    key = (ams_id, tray_id)
    snapshot_spool_id = spool_assignments_snapshot.get(key) if spool_assignments_snapshot else None

    # Backward-compatible fast path: if we have a snapshot but no print-start
    # timestamp, preserve legacy behavior and avoid extra DB lookups.
    if snapshot_spool_id is not None and print_started_at is None:
        return snapshot_spool_id

    result = await db.execute(
        select(SpoolAssignment).where(
            SpoolAssignment.printer_id == printer_id,
            SpoolAssignment.ams_id == ams_id,
            SpoolAssignment.tray_id == tray_id,
        )
    )
    live_assignment = result.scalar_one_or_none()

    if snapshot_spool_id is not None:
        if live_assignment and live_assignment.spool_id != snapshot_spool_id:
            live_created_ts = _to_epoch_seconds(getattr(live_assignment, "created_at", None))
            started_ts = _to_epoch_seconds(print_started_at)
            if live_created_ts is not None and started_ts is not None and live_created_ts >= started_ts:
                logger.info(
                    "[UsageTracker] Assignment changed during print for printer %d AMS%d-T%d: snapshot spool %d -> live spool %d",
                    printer_id,
                    ams_id,
                    tray_id,
                    snapshot_spool_id,
                    live_assignment.spool_id,
                )
                return live_assignment.spool_id
        return snapshot_spool_id

    if live_assignment:
        return live_assignment.spool_id

    return None


async def on_print_start(printer_id: int, data: dict, printer_manager, db: AsyncSession | None = None) -> None:
    """Capture AMS tray remain% and spool assignments at print start."""
    state = printer_manager.get_status(printer_id)
    if not state or not state.raw_data:
        logger.debug("[UsageTracker] No state for printer %d, skipping", printer_id)
        return

    ams_raw = state.raw_data.get("ams", [])
    ams_data = ams_raw.get("ams", []) if isinstance(ams_raw, dict) else ams_raw if isinstance(ams_raw, list) else []
    if not ams_data:
        logger.debug("[UsageTracker] No AMS data for printer %d, skipping", printer_id)
        return

    tray_remain_start: dict[tuple[int, int], int] = {}
    for ams_unit in ams_data:
        ams_id = int(ams_unit.get("id", 0))
        for tray in ams_unit.get("tray", []):
            tray_id = int(tray.get("id", 0))
            remain = tray.get("remain", -1)
            if isinstance(remain, int) and 0 <= remain <= 100:
                tray_remain_start[(ams_id, tray_id)] = remain

    print_name = data.get("subtask_name", "") or data.get("filename", "unknown")

    # Capture tray_now at print start (reliable, unlike at completion where it's 255)
    tray_now_at_start = state.tray_now if state else -1

    # --- Diagnostic logging: dump mapping-related MQTT fields at print start ---
    # This helps us understand what each printer model reports for slot-to-tray mapping.
    mapping_field = state.raw_data.get("mapping")
    logger.info(
        "[UsageTracker] PRINT START printer %d: mapping=%s, tray_now=%d, last_loaded_tray=%s",
        printer_id,
        mapping_field,
        tray_now_at_start,
        getattr(state, "last_loaded_tray", "N/A"),
    )
    # Log all raw_data keys containing "map" or "ams" for discovery
    map_keys = {k: state.raw_data[k] for k in state.raw_data if "map" in k.lower()}
    if map_keys:
        logger.info("[UsageTracker] PRINT START printer %d: mapping-related keys: %s", printer_id, map_keys)
    # Log per-tray summary: tray_now, tray_tar, tray_type, tray_color for each slot
    for ams_unit in ams_data:
        ams_id = int(ams_unit.get("id", 0))
        tray_summary = []
        for tray in ams_unit.get("tray", []):
            tray_summary.append(
                f"T{tray.get('id', '?')}(type={tray.get('tray_type', '')}, "
                f"color={tray.get('tray_color', '')}, "
                f"now={ams_raw.get('tray_now', '?') if isinstance(ams_raw, dict) else '?'}, "
                f"tar={ams_raw.get('tray_tar', '?') if isinstance(ams_raw, dict) else '?'})"
            )
        logger.info("[UsageTracker] PRINT START printer %d AMS %d: %s", printer_id, ams_id, ", ".join(tray_summary))

    # Snapshot spool assignments so usage isn't lost if on_ams_change unlinks mid-print
    spool_assignments: dict[tuple[int, int], int] = {}
    if db:
        assign_result = await db.execute(select(SpoolAssignment).where(SpoolAssignment.printer_id == printer_id))
        for assignment in assign_result.scalars().all():
            spool_assignments[(assignment.ams_id, assignment.tray_id)] = assignment.spool_id
        if spool_assignments:
            logger.info(
                "[UsageTracker] Snapshotted %d spool assignments for printer %d: %s",
                len(spool_assignments),
                printer_id,
                {f"{k[0]}-{k[1]}": v for k, v in spool_assignments.items()},
            )

    # Always create session (even without valid remain data) so print_name
    # is available at completion for 3MF-based tracking
    session = PrintSession(
        printer_id=printer_id,
        print_name=print_name,
        started_at=datetime.now(timezone.utc),
        tray_remain_start=tray_remain_start,
        tray_now_at_start=tray_now_at_start,
        spool_assignments=spool_assignments,
    )
    _active_sessions[printer_id] = session

    if tray_remain_start:
        logger.info(
            "[UsageTracker] Captured start remain%% for printer %d (%d trays): %s",
            printer_id,
            len(tray_remain_start),
            {f"{k[0]}-{k[1]}": v for k, v in tray_remain_start.items()},
        )
    else:
        logger.debug("[UsageTracker] No valid remain%% for printer %d, 3MF fallback available", printer_id)


async def on_print_complete(
    printer_id: int,
    data: dict,
    printer_manager,
    db: AsyncSession,
    archive_id: int | None = None,
    ams_mapping: list[int] | None = None,
) -> list[dict]:
    """Compute consumption deltas and update spool weight_used/last_used.

    Uses two tracking strategies in priority order:
    1. 3MF per-filament estimates (primary) — precise slicer data for all spools
    2. AMS remain% delta (fallback) — only for trays not already handled by 3MF

    Returns a list of dicts describing what was logged (for WebSocket broadcast).
    """
    from sqlalchemy import select

    from backend.app.api.routes.settings import get_setting
    from backend.app.models.spool_usage_history import SpoolUsageHistory

    session = _active_sessions.pop(printer_id, None)
    status = data.get("status", "completed")
    results = []
    handled_trays: set[tuple[int, int]] = set()

    # Fetch default filament cost from settings for fallback
    default_cost_str = await get_setting(db, "default_filament_cost")
    default_filament_cost = float(default_cost_str) if default_cost_str else 0.0

    logger.info(
        "[UsageTracker] on_print_complete: printer=%d, archive=%s, session=%s, ams_mapping=%s",
        printer_id,
        archive_id,
        "yes" if session else "no",
        ams_mapping,
    )

    # --- Diagnostic logging: dump mapping-related MQTT fields at print completion ---
    state = printer_manager.get_status(printer_id)
    if state and state.raw_data:
        logger.info(
            "[UsageTracker] PRINT COMPLETE printer %d: mapping=%s, tray_now=%s, last_loaded_tray=%s",
            printer_id,
            state.raw_data.get("mapping"),
            state.tray_now,
            getattr(state, "last_loaded_tray", "N/A"),
        )

    # --- Path 1 (PRIMARY): 3MF per-filament estimates ---
    if archive_id:
        print_name = (
            (session.print_name if session else None) or data.get("subtask_name", "") or data.get("filename", "unknown")
        )
        threemf_results = await _track_from_3mf(
            printer_id,
            archive_id,
            status,
            print_name,
            handled_trays,
            printer_manager,
            db,
            ams_mapping=ams_mapping,
            tray_now_at_start=session.tray_now_at_start if session else -1,
            last_progress=data.get("last_progress", 0.0),
            last_layer_num=data.get("last_layer_num", 0),
            default_filament_cost=default_filament_cost,
            spool_assignments=session.spool_assignments if session else None,
            print_started_at=session.started_at if session else None,
        )
        results.extend(threemf_results)

    # --- Path 2 (FALLBACK): AMS remain% delta (only for trays not handled by 3MF) ---
    if session and session.tray_remain_start:
        state = printer_manager.get_status(printer_id)
        if state and state.raw_data:
            ams_raw = state.raw_data.get("ams", [])
            ams_data = (
                ams_raw.get("ams", []) if isinstance(ams_raw, dict) else ams_raw if isinstance(ams_raw, list) else []
            )

            for ams_unit in ams_data:
                ams_id = int(ams_unit.get("id", 0))
                for tray in ams_unit.get("tray", []):
                    tray_id = int(tray.get("id", 0))
                    key = (ams_id, tray_id)

                    if key in handled_trays:
                        continue  # Already tracked via 3MF

                    if key not in session.tray_remain_start:
                        continue

                    current_remain = tray.get("remain", -1)
                    if not isinstance(current_remain, int) or current_remain < 0 or current_remain > 100:
                        continue

                    start_remain = session.tray_remain_start[key]
                    delta_pct = start_remain - current_remain

                    if delta_pct <= 0:
                        continue  # No consumption or tray was refilled

                    spool_id = await _resolve_spool_id_for_tray(
                        printer_id=printer_id,
                        ams_id=ams_id,
                        tray_id=tray_id,
                        db=db,
                        spool_assignments_snapshot=session.spool_assignments,
                        print_started_at=session.started_at,
                    )
                    if spool_id is None:
                        continue

                    # Load spool
                    spool_result = await db.execute(select(Spool).where(Spool.id == spool_id))
                    spool = spool_result.scalar_one_or_none()
                    if not spool:
                        continue

                    # Compute weight consumed
                    weight_grams = (delta_pct / 100.0) * spool.label_weight

                    # Update spool
                    spool.weight_used = (spool.weight_used or 0) + weight_grams
                    spool.last_used = datetime.now(timezone.utc)

                    # Calculate cost for this usage
                    cost = None
                    cost_per_kg = spool.cost_per_kg if spool.cost_per_kg is not None else default_filament_cost
                    if cost_per_kg > 0:
                        cost = round((weight_grams / 1000.0) * cost_per_kg, 2)

                    # Insert usage history record
                    history = SpoolUsageHistory(
                        spool_id=spool.id,
                        printer_id=printer_id,
                        print_name=session.print_name,
                        weight_used=round(weight_grams, 1),
                        percent_used=delta_pct,
                        status=status,
                        cost=cost,
                        archive_id=archive_id,
                    )
                    db.add(history)

                    handled_trays.add(key)
                    results.append(
                        {
                            "spool_id": spool.id,
                            "weight_used": round(weight_grams, 1),
                            "percent_used": delta_pct,
                            "ams_id": ams_id,
                            "tray_id": tray_id,
                            "material": spool.material,
                            "cost": cost,
                        }
                    )

                    logger.info(
                        "[UsageTracker] Spool %d consumed %.1fg (%d%%) on printer %d AMS%d-T%d (AMS fallback, %s)",
                        spool.id,
                        weight_grams,
                        delta_pct,
                        printer_id,
                        ams_id,
                        tray_id,
                        status,
                    )

    if results:
        await db.commit()

    # --- Update PrintArchive.cost from THIS print session only ---

    if archive_id and results:
        from sqlalchemy import select

        from backend.app.models.archive import PrintArchive

        archive_result = await db.execute(select(PrintArchive).where(PrintArchive.id == archive_id))
        archive = archive_result.scalar_one_or_none()
        if archive:
            total_cost = sum(r.get("cost", 0) or 0 for r in results)
            if total_cost > 0:
                archive.cost = round(total_cost, 2)
                await db.commit()

    return results


async def _track_from_3mf(
    printer_id: int,
    archive_id: int,
    status: str,
    print_name: str,
    handled_trays: set[tuple[int, int]],
    printer_manager,
    db: AsyncSession,
    ams_mapping: list[int] | None = None,
    tray_now_at_start: int = -1,
    last_progress: float = 0.0,
    last_layer_num: int = 0,
    default_filament_cost: float = 0.0,
    spool_assignments: dict[tuple[int, int], int] | None = None,
    print_started_at: datetime | None = None,
) -> list[dict]:
    """Track usage from 3MF per-filament slicer data (primary path).

    Uses slicer-estimated filament weight for all spools (BL and non-BL).
    For partial prints (failed/aborted), tries per-layer gcode data first,
    then falls back to linear scaling by progress.

    Slot-to-tray mapping priority:
    1. Stored ams_mapping from print command (reprints/direct prints)
    2. MQTT mapping field from printer state (universal, all print sources)
    3. Queue item ams_mapping (for queue-initiated prints)
    4. tray_now from printer state (for single-filament non-queue prints)
    5. Position-based default using sorted available tray IDs (handles external spools)
    6. Default mapping: slot_id - 1 = global_tray_id (last resort)
    """
    from backend.app.core.config import settings as app_settings
    from backend.app.models.archive import PrintArchive
    from backend.app.models.print_queue import PrintQueueItem
    from backend.app.utils.threemf_tools import extract_filament_usage_from_3mf

    result = await db.execute(select(PrintArchive).where(PrintArchive.id == archive_id))
    archive = result.scalar_one_or_none()
    if not archive or not archive.file_path:
        logger.info("[UsageTracker] 3MF: archive %s has no file_path, skipping", archive_id)
        return []

    file_path = app_settings.base_dir / archive.file_path
    if not file_path.exists():
        logger.info("[UsageTracker] 3MF: file not found: %s", file_path)
        return []

    filament_usage = extract_filament_usage_from_3mf(file_path)
    if not filament_usage:
        logger.info("[UsageTracker] 3MF: no filament usage data in %s", file_path)
        return []

    logger.info("[UsageTracker] 3MF: archive %s, filament_usage=%s", archive_id, filament_usage)

    # --- Resolve slot-to-tray mapping ---
    mapping_source = None

    # 1. Use stored ams_mapping from the print command (reprints/direct prints)
    slot_to_tray = ams_mapping
    if slot_to_tray:
        mapping_source = "print_cmd"

    # 2. Try MQTT mapping field from printer state (universal, all print sources)
    if not slot_to_tray:
        state = printer_manager.get_status(printer_id)
        raw_data = getattr(state, "raw_data", None) if state else None
        if raw_data:
            mqtt_mapping = raw_data.get("mapping")
            decoded = _decode_mqtt_mapping(mqtt_mapping)
            if decoded:
                slot_to_tray = decoded
                mapping_source = "mqtt"

    # 3. Try queue item ams_mapping (queue-initiated prints store the exact mapping)
    if not slot_to_tray:
        queue_result = await db.execute(
            select(PrintQueueItem)
            .where(PrintQueueItem.archive_id == archive_id)
            .where(PrintQueueItem.status.in_(["printing", "completed", "failed"]))
        )
        queue_item = queue_result.scalar_one_or_none()
        if queue_item and queue_item.ams_mapping:
            try:
                slot_to_tray = json.loads(queue_item.ams_mapping)
                mapping_source = "queue"
            except (json.JSONDecodeError, TypeError):
                pass

    # 4. Color-match 3MF filament slots to AMS trays (for printers without mapping field)
    if not slot_to_tray:
        state = printer_manager.get_status(printer_id)
        raw_data = getattr(state, "raw_data", None) if state else None
        if raw_data:
            matched = _match_slots_by_color(filament_usage, raw_data.get("ams"))
            if matched:
                slot_to_tray = matched
                mapping_source = "color_match"

    logger.info(
        "[UsageTracker] 3MF: slot_to_tray=%s (source: %s)",
        slot_to_tray,
        mapping_source or "none",
    )

    # 5. For single-filament non-queue prints, use tray_now from printer state
    #    Priority: tray_change_log (multi-tray split) > tray_now_at_start > current tray_now
    #              > last_loaded_tray > vt_tray check
    nonzero_slots = [u for u in filament_usage if u.get("used_g", 0) > 0]
    tray_now_override: int | None = None
    tray_changes: list[tuple[int, int]] = []  # [(global_tray_id, layer_num), ...]
    if not slot_to_tray and len(nonzero_slots) == 1:
        state = printer_manager.get_status(printer_id)
        tray_changes = getattr(state, "tray_change_log", []) if state else []

        if len(tray_changes) > 1:
            # Multi-tray usage detected — will split in per-slot loop using per-layer gcode
            logger.info("[UsageTracker] 3MF: tray change log: %s (will split weight)", tray_changes)
        elif 0 <= tray_now_at_start <= 254:
            # Try tray_now_at_start first (captured at print start)
            tray_now_override = tray_now_at_start
            logger.info("[UsageTracker] 3MF: using tray_now_at_start=%d (single-filament fallback)", tray_now_at_start)
        elif state and 0 <= state.tray_now <= 254:
            # Current state is valid (printer didn't retract yet)
            tray_now_override = state.tray_now
            logger.info("[UsageTracker] 3MF: using current tray_now=%d", state.tray_now)
        elif state and 0 <= state.last_loaded_tray <= 253:
            # Last valid tray before retract (H2D retracts before completion callback)
            tray_now_override = state.last_loaded_tray
            logger.info("[UsageTracker] 3MF: using last_loaded_tray=%d (post-retract fallback)", state.last_loaded_tray)
        elif state and state.tray_now == 255:
            # 255 = "no filament" on legacy printers, but valid 2nd external spool on H2-series
            vt_tray = state.raw_data.get("vt_tray") or []
            if any(int(vt.get("id", 0)) == 255 for vt in vt_tray if isinstance(vt, dict)):
                tray_now_override = state.tray_now
                logger.info("[UsageTracker] 3MF: using tray_now=255 (H2-series external spool)")
        if tray_now_override is None and len(tray_changes) <= 1:
            logger.info(
                "[UsageTracker] 3MF: no valid tray_now (at_start=%d, current=%s, last_loaded=%s)",
                tray_now_at_start,
                state.tray_now if state else "N/A",
                state.last_loaded_tray if state else "N/A",
            )

    # Scale factor for partial prints (failed/aborted)
    if status == "completed":
        scale = 1.0
    else:
        state = printer_manager.get_status(printer_id)
        progress = state.progress if state else 0
        # Firmware resets progress to 0 on cancel — use last valid progress captured during print
        if progress <= 0 and last_progress > 0:
            progress = last_progress
            logger.info("[UsageTracker] 3MF: using last_progress=%.1f (firmware reset current to 0)", last_progress)
        scale = max(0.0, min(progress / 100.0, 1.0))

    # Per-layer gcode accuracy for partial prints
    layer_grams: dict[int, float] | None = None
    if status != "completed":
        state = printer_manager.get_status(printer_id)
        current_layer = state.layer_num if state else 0
        # Firmware resets layer_num to 0 on cancel — use last valid layer captured during print
        if current_layer <= 0 and last_layer_num > 0:
            current_layer = last_layer_num
            logger.info("[UsageTracker] 3MF: using last_layer_num=%d (firmware reset current to 0)", last_layer_num)
        if current_layer > 0:
            try:
                from backend.app.utils.threemf_tools import (
                    extract_filament_properties_from_3mf,
                    extract_layer_filament_usage_from_3mf,
                    get_cumulative_usage_at_layer,
                    mm_to_grams,
                )

                layer_usage = extract_layer_filament_usage_from_3mf(file_path)
                if layer_usage:
                    cumulative_mm = get_cumulative_usage_at_layer(layer_usage, current_layer)
                    filament_props = extract_filament_properties_from_3mf(file_path)
                    layer_grams = {}
                    for filament_id, mm_used in cumulative_mm.items():
                        slot_id = filament_id + 1  # 0-based to 1-based
                        props = filament_props.get(slot_id, {})
                        density = props.get("density", 1.24)
                        diameter = props.get("diameter", 1.75)
                        layer_grams[slot_id] = mm_to_grams(mm_used, diameter, density)
            except Exception:
                pass  # Fall back to linear scaling

    results = []

    for usage in filament_usage:
        slot_id = usage.get("slot_id", 0)
        used_g = usage.get("used_g", 0)
        if used_g <= 0:
            continue

        # --- Mid-print tray switch: split weight across trays ---
        if len(tray_changes) > 1:
            # Compute total weight for this slot (same logic as normal path)
            if layer_grams and slot_id in layer_grams:
                total_weight = layer_grams[slot_id]
            else:
                total_weight = used_g * scale

            if total_weight <= 0:
                continue

            # Extract per-layer gcode for segment splitting
            split_layer_usage = None
            split_props: dict = {}
            try:
                from backend.app.utils.threemf_tools import (
                    extract_filament_properties_from_3mf,
                    extract_layer_filament_usage_from_3mf,
                    get_cumulative_usage_at_layer,
                    mm_to_grams,
                )

                split_layer_usage = extract_layer_filament_usage_from_3mf(file_path)
                filament_props = extract_filament_properties_from_3mf(file_path)
                split_props = filament_props.get(slot_id, {})
            except Exception:
                pass  # Fall back to linear splitting

            density = split_props.get("density", 1.24)
            diameter = split_props.get("diameter", 1.75)
            filament_id = slot_id - 1  # 0-based for gcode

            sum_previous = 0.0
            for seg_idx, (tray_global, seg_start_layer) in enumerate(tray_changes):
                is_last = seg_idx + 1 >= len(tray_changes)

                if is_last:
                    # Last segment: remainder to avoid rounding drift
                    segment_grams = total_weight - sum_previous
                elif split_layer_usage:
                    seg_end_layer = tray_changes[seg_idx + 1][1]
                    mm_at_start = get_cumulative_usage_at_layer(split_layer_usage, seg_start_layer).get(filament_id, 0)
                    mm_at_end = get_cumulative_usage_at_layer(split_layer_usage, seg_end_layer).get(filament_id, 0)
                    segment_grams = mm_to_grams(mm_at_end - mm_at_start, diameter, density)
                else:
                    # No per-layer data: linear fallback by layer ratio
                    seg_end_layer = tray_changes[seg_idx + 1][1]
                    total_layers = state.total_layers if state else 0
                    if total_layers > 0:
                        segment_grams = total_weight * (seg_end_layer - seg_start_layer) / total_layers
                    else:
                        # Can't compute ratio — assign all to last segment
                        segment_grams = 0.0

                sum_previous += segment_grams
                if segment_grams <= 0:
                    continue

                # Convert global tray ID to (ams_id, tray_id)
                if tray_global >= 254:
                    seg_ams_id = 255
                    seg_tray_id = tray_global - 254
                elif tray_global >= 128:
                    seg_ams_id = tray_global
                    seg_tray_id = 0
                else:
                    seg_ams_id = tray_global // 4
                    seg_tray_id = tray_global % 4

                seg_key = (seg_ams_id, seg_tray_id)
                if seg_key in handled_trays:
                    continue

                logger.info(
                    "[UsageTracker] 3MF split: segment %d tray=%d (AMS%d-T%d) layers %d-%s -> %.1fg",
                    seg_idx,
                    tray_global,
                    seg_ams_id,
                    seg_tray_id,
                    seg_start_layer,
                    tray_changes[seg_idx + 1][1] if not is_last else "end",
                    segment_grams,
                )

                seg_spool_id = await _resolve_spool_id_for_tray(
                    printer_id=printer_id,
                    ams_id=seg_ams_id,
                    tray_id=seg_tray_id,
                    db=db,
                    spool_assignments_snapshot=spool_assignments,
                    print_started_at=print_started_at,
                )
                if seg_spool_id is None:
                    logger.info(
                        "[UsageTracker] 3MF split: no spool at printer %d AMS%d-T%d, skipping segment",
                        printer_id,
                        seg_ams_id,
                        seg_tray_id,
                    )
                    continue

                spool_result = await db.execute(select(Spool).where(Spool.id == seg_spool_id))
                spool = spool_result.scalar_one_or_none()
                if not spool:
                    continue

                spool.weight_used = (spool.weight_used or 0) + segment_grams
                spool.last_used = datetime.now(timezone.utc)

                percent = round(segment_grams / (spool.label_weight or 1000) * 100)

                cost = None
                cost_per_kg = spool.cost_per_kg if spool.cost_per_kg is not None else default_filament_cost
                if cost_per_kg > 0:
                    cost = round((segment_grams / 1000.0) * cost_per_kg, 2)

                history = SpoolUsageHistory(
                    spool_id=spool.id,
                    printer_id=printer_id,
                    print_name=print_name,
                    weight_used=round(segment_grams, 1),
                    percent_used=percent,
                    status=status,
                    cost=cost,
                    archive_id=archive_id,
                )
                db.add(history)

                handled_trays.add(seg_key)
                results.append(
                    {
                        "spool_id": spool.id,
                        "weight_used": round(segment_grams, 1),
                        "percent_used": percent,
                        "ams_id": seg_ams_id,
                        "tray_id": seg_tray_id,
                        "material": spool.material,
                        "cost": cost,
                    }
                )

                logger.info(
                    "[UsageTracker] Spool %d consumed %.1fg (3MF split seg%d) on printer %d AMS%d-T%d (%s)",
                    spool.id,
                    segment_grams,
                    seg_idx,
                    printer_id,
                    seg_ams_id,
                    seg_tray_id,
                    status,
                )

            continue  # Skip normal single-tray processing for this slot

        # Map 3MF slot_id to physical (ams_id, tray_id) using resolved mapping
        if tray_now_override is not None:
            # Single-filament non-queue print: use actual tray from printer state
            global_tray_id = tray_now_override
        else:
            # Explicit mapping (print command, MQTT, queue, color match)
            global_tray_id = None
            if slot_to_tray and slot_id <= len(slot_to_tray):
                mapped = slot_to_tray[slot_id - 1]
                if isinstance(mapped, int) and mapped >= 0:
                    global_tray_id = mapped
            # Position-based default: sort available tray IDs so external spools (254/255)
            # naturally follow standard AMS trays, matching slicer slot numbering
            if global_tray_id is None:
                _state = printer_manager.get_status(printer_id)
                _raw = getattr(_state, "raw_data", None) if _state else None
                if _raw:
                    from backend.app.services.spoolman_tracking import build_ams_tray_lookup

                    available_trays = sorted(build_ams_tray_lookup(_raw).keys())
                    if slot_id <= len(available_trays):
                        global_tray_id = available_trays[slot_id - 1]
            # Final fallback: slot_id - 1 (legacy, works for pure AMS without external spools)
            if global_tray_id is None:
                global_tray_id = slot_id - 1

        if global_tray_id >= 254:
            # External spool: ams_id=255 (sentinel), tray_id=slot index (0 or 1)
            ams_id = 255
            tray_id = global_tray_id - 254
        elif global_tray_id >= 128:
            ams_id = global_tray_id
            tray_id = 0
        else:
            ams_id = global_tray_id // 4
            tray_id = global_tray_id % 4

        logger.info(
            "[UsageTracker] 3MF: slot_id=%d -> global_tray=%d -> AMS%d-T%d (used_g=%.1f, tray_now_override=%s)",
            slot_id,
            global_tray_id,
            ams_id,
            tray_id,
            used_g,
            tray_now_override,
        )

        key = (ams_id, tray_id)
        if key in handled_trays:
            continue

        spool_id = await _resolve_spool_id_for_tray(
            printer_id=printer_id,
            ams_id=ams_id,
            tray_id=tray_id,
            db=db,
            spool_assignments_snapshot=spool_assignments,
            print_started_at=print_started_at,
        )
        if spool_id is None:
            logger.info("[UsageTracker] 3MF: no spool assignment at printer %d AMS%d-T%d", printer_id, ams_id, tray_id)
            continue

        # Load spool
        spool_result = await db.execute(select(Spool).where(Spool.id == spool_id))
        spool = spool_result.scalar_one_or_none()
        if not spool:
            continue

        # Use per-layer grams if available, otherwise linear scale
        if layer_grams and slot_id in layer_grams:
            weight_grams = layer_grams[slot_id]
        else:
            weight_grams = used_g * scale

        if weight_grams <= 0:
            continue

        # Update spool
        spool.weight_used = (spool.weight_used or 0) + weight_grams
        spool.last_used = datetime.now(timezone.utc)

        percent = round(weight_grams / (spool.label_weight or 1000) * 100)

        # Calculate cost for this usage
        cost = None
        cost_per_kg = spool.cost_per_kg if spool.cost_per_kg is not None else default_filament_cost
        if cost_per_kg > 0:
            cost = round((weight_grams / 1000.0) * cost_per_kg, 2)

        # Insert usage history record
        history = SpoolUsageHistory(
            spool_id=spool.id,
            printer_id=printer_id,
            print_name=print_name,
            weight_used=round(weight_grams, 1),
            percent_used=percent,
            status=status,
            cost=cost,
            archive_id=archive_id,
        )
        db.add(history)

        handled_trays.add(key)
        results.append(
            {
                "spool_id": spool.id,
                "weight_used": round(weight_grams, 1),
                "percent_used": percent,
                "ams_id": ams_id,
                "tray_id": tray_id,
                "material": spool.material,
                "cost": cost,
            }
        )

        # Determine mapping source for debug logging
        if tray_now_override is not None:
            map_src = ", tray_now"
        elif mapping_source:
            map_src = f", {mapping_source}_map"
        else:
            map_src = ""
        logger.info(
            "[UsageTracker] Spool %d consumed %.1fg (3MF%s%s) on printer %d AMS%d-T%d (%s)",
            spool.id,
            weight_grams,
            " per-layer" if (layer_grams and slot_id in layer_grams) else (f" scaled {scale:.0%}" if scale < 1 else ""),
            map_src,
            printer_id,
            ams_id,
            tray_id,
            status,
        )

    return results