"""Virtual digital multimeter (DMM) simulator.

This module implements a SCPI-based virtual multimeter that interfaces
with the physics engine to measure DUT electrical parameters.
"""

from __future__ import annotations

from enum import Enum
from typing import TYPE_CHECKING

from py_dvt_ate.instruments.scpi import SCPICommand
from py_dvt_ate.simulation.virtual.base import BaseInstrument

if TYPE_CHECKING:
    from py_dvt_ate.simulation.physics.engine import PhysicsEngine


class MeasurementFunction(Enum):
    """Available measurement functions."""

    VOLTAGE_DC = "VOLT:DC"
    CURRENT_DC = "CURR:DC"


class MultimeterSim(BaseInstrument):
    """Virtual digital multimeter simulator.

    Simulates a digital multimeter with SCPI control interface. The DMM
    measures DUT output voltage and load current via the physics engine.

    SCPI Commands:
        MEAS:VOLT:DC?      - Measure DC voltage (shortcut)
        MEAS:CURR:DC?      - Measure DC current (shortcut)
        CONF:VOLT:DC       - Configure for DC voltage measurement
        CONF:CURR:DC       - Configure for DC current measurement
        CONF?              - Query current configuration
        READ?              - Take measurement with current configuration

    Attributes:
        manufacturer: "PyDVTATE"
        model: "DMM-SIM-001"
    """

    manufacturer = "PyDVTATE"
    model = "DMM-SIM-001"
    serial_number = "DMMSIM001"
    firmware_version = "1.0.0"

    def __init__(self, physics_engine: PhysicsEngine | None = None) -> None:
        """Initialise the multimeter simulator.

        Args:
            physics_engine: Reference to physics engine for measurement values.
        """
        self._function = MeasurementFunction.VOLTAGE_DC
        super().__init__(physics_engine)

    def _setup_commands(self) -> None:
        """Register multimeter SCPI commands."""
        self.register_command("MEAS:VOLT:DC", self._handle_meas_volt_dc)
        self.register_command("MEAS:CURR:DC", self._handle_meas_curr_dc)
        self.register_command("CONF:VOLT:DC", self._handle_conf_volt_dc)
        self.register_command("CONF:CURR:DC", self._handle_conf_curr_dc)
        self.register_command("CONF", self._handle_conf)
        self.register_command("READ", self._handle_read)

    def reset(self) -> None:
        """Reset multimeter to default state."""
        self._function = MeasurementFunction.VOLTAGE_DC

    def _handle_meas_volt_dc(self, command: SCPICommand) -> str:
        """Handle MEAS:VOLT:DC? query.

        Configures for DC voltage and takes measurement in one command.

        Args:
            command: Parsed SCPI command.

        Returns:
            Measured DC voltage.

        Raises:
            ValueError: If used as command (not query).
        """
        if not command.is_query:
            raise ValueError("MEAS:VOLT:DC is query only")

        self._function = MeasurementFunction.VOLTAGE_DC
        return self._measure_voltage_dc()

    def _handle_meas_curr_dc(self, command: SCPICommand) -> str:
        """Handle MEAS:CURR:DC? query.

        Configures for DC current and takes measurement in one command.

        Args:
            command: Parsed SCPI command.

        Returns:
            Measured DC current.

        Raises:
            ValueError: If used as command (not query).
        """
        if not command.is_query:
            raise ValueError("MEAS:CURR:DC is query only")

        self._function = MeasurementFunction.CURRENT_DC
        return self._measure_current_dc()

    def _handle_conf_volt_dc(self, command: SCPICommand) -> str:
        """Handle CONF:VOLT:DC command.

        Configures multimeter for DC voltage measurement.

        Args:
            command: Parsed SCPI command.

        Returns:
            Empty string (no response for configuration).

        Raises:
            ValueError: If used as query.
        """
        if command.is_query:
            raise ValueError("CONF:VOLT:DC is command only")

        self._function = MeasurementFunction.VOLTAGE_DC
        return ""

    def _handle_conf_curr_dc(self, command: SCPICommand) -> str:
        """Handle CONF:CURR:DC command.

        Configures multimeter for DC current measurement.

        Args:
            command: Parsed SCPI command.

        Returns:
            Empty string (no response for configuration).

        Raises:
            ValueError: If used as query.
        """
        if command.is_query:
            raise ValueError("CONF:CURR:DC is command only")

        self._function = MeasurementFunction.CURRENT_DC
        return ""

    def _handle_conf(self, command: SCPICommand) -> str:
        """Handle CONF? query.

        Args:
            command: Parsed SCPI command.

        Returns:
            Current measurement configuration.

        Raises:
            ValueError: If used as command without subcommand.
        """
        if not command.is_query:
            raise ValueError("CONF requires a function (e.g., CONF:VOLT:DC)")

        return f'"{self._function.value}"'

    def _handle_read(self, command: SCPICommand) -> str:
        """Handle READ? query.

        Takes measurement using current configuration.

        Args:
            command: Parsed SCPI command.

        Returns:
            Measured value.

        Raises:
            ValueError: If used as command (not query).
        """
        if not command.is_query:
            raise ValueError("READ is query only")

        if self._function == MeasurementFunction.VOLTAGE_DC:
            return self._measure_voltage_dc()
        else:
            return self._measure_current_dc()

    def _measure_voltage_dc(self) -> str:
        """Measure DC voltage from physics engine.

        Returns:
            Formatted voltage reading.
        """
        if self._physics_engine is None:
            return "0.000000"

        electrical_state = self._physics_engine.get_electrical_state()
        return f"{electrical_state.output_voltage:.6f}"

    def _measure_current_dc(self) -> str:
        """Measure DC current from physics engine.

        Returns:
            Formatted current reading.
        """
        if self._physics_engine is None:
            return "0.000000"

        electrical_state = self._physics_engine.get_electrical_state()
        return f"{electrical_state.load_current:.6f}"