"""Cirq sampler for HIQ.

This module implements Cirq's Sampler interface, allowing users to execute
Arvak circuits through Cirq's sampling API.
"""

from typing import List, Optional, Union, TYPE_CHECKING, Dict, Sequence
import warnings

if TYPE_CHECKING:
    import cirq


class ArvakSampler:
    """HIQ sampler implementing Cirq's Sampler interface.

    This sampler allows Cirq programs to execute on HIQ backends using
    Cirq's standard sampling API.

    Example:
        >>> from arvak.integrations.cirq import ArvakSampler
        >>> import cirq
        >>>
        >>> qubits = cirq.LineQubit.range(2)
        >>> circuit = cirq.Circuit(
        ...     cirq.H(qubits[0]),
        ...     cirq.CNOT(qubits[0], qubits[1]),
        ...     cirq.measure(*qubits, key='result')
        ... )
        >>>
        >>> sampler = ArvakSampler('sim')
        >>> result = sampler.run(circuit, repetitions=1000)
        >>> print(result)
    """

    def __init__(self, backend_name: str = 'sim'):
        """Initialize the HIQ sampler.

        Args:
            backend_name: Name of the backend to use (default: 'sim')
        """
        self.backend_name = backend_name
        self.name = f'hiq_{backend_name}'

    def run(self, program: 'cirq.Circuit',
            repetitions: int = 1,
            param_resolver: Optional['cirq.ParamResolver'] = None) -> 'cirq.Result':
        """Run the supplied Circuit, mimicking Cirq's Sampler interface.

        Args:
            program: Cirq Circuit to execute
            repetitions: Number of times to execute the circuit
            param_resolver: Parameters to resolve in the circuit (unused)

        Returns:
            Cirq Result object with measurement outcomes

        Note:
            This is a mock implementation. For actual execution, use the HIQ CLI:
            'hiq run circuit.qasm --backend sim --shots 1000'
        """
        warnings.warn(
            "HIQ backend execution through Cirq is not yet fully implemented. "
            "For now, please use HIQ CLI for execution: "
            "'hiq run circuit.qasm --backend sim --shots 1000'. "
            "This sampler will return mock results.",
            RuntimeWarning
        )

        # Convert to Arvak format
        from .converter import cirq_to_arvak
        import arvak

        hiq_circuit = cirq_to_arvak(program)

        # Create mock results
        return self._mock_result(program, hiq_circuit, repetitions)

    def run_sweep(self, program: 'cirq.Circuit',
                  params: 'cirq.Sweepable',
                  repetitions: int = 1) -> Sequence['cirq.Result']:
        """Run the supplied Circuit for various parameter sweeps.

        Args:
            program: Cirq Circuit to execute
            params: Parameters to sweep over
            repetitions: Number of times to execute each circuit

        Returns:
            List of Cirq Result objects

        Note:
            This is a mock implementation.
        """
        warnings.warn(
            "Parameter sweeps not yet implemented in HIQ backend.",
            RuntimeWarning
        )

        # For now, just run once
        return [self.run(program, repetitions=repetitions)]

    def _mock_result(self, cirq_circuit, hiq_circuit, repetitions: int) -> 'HIQResult':
        """Generate mock results for demonstration.

        Args:
            cirq_circuit: Original Cirq circuit
            hiq_circuit: Converted Arvak circuit
            repetitions: Number of repetitions

        Returns:
            Mock Result object
        """
        import cirq
        import numpy as np

        # Get measurement keys from circuit
        measurements = list(cirq.protocols.measurement_key_names(cirq_circuit))

        if not measurements:
            measurements = ['result']

        # Generate mock data (Bell state results)
        # For 2-qubit Bell state: 50% |00⟩, 50% |11⟩
        num_qubits = len(cirq_circuit.all_qubits())
        mock_data = {}

        for key in measurements:
            # Create mock measurements
            # For simplicity, return random bits that match Bell state distribution
            samples = np.random.choice([0, num_qubits - 1], size=repetitions)
            bitstrings = np.zeros((repetitions, num_qubits), dtype=int)

            for i, val in enumerate(samples):
                if val > 0:
                    bitstrings[i] = [1] * num_qubits

            mock_data[key] = bitstrings

        return HIQResult(
            params=cirq.ParamResolver({}),
            measurements=mock_data,
            repetitions=repetitions
        )

    def __repr__(self) -> str:
        """String representation of the sampler."""
        return f"<ArvakSampler('{self.name}')>"


class HIQResult:
    """Mock result for HIQ sampler execution.

    This mimics Cirq's Result object but returns mock data.
    In a real implementation, this would parse actual HIQ execution results.
    """

    def __init__(self, params, measurements: Dict[str, np.ndarray], repetitions: int):
        """Initialize the result.

        Args:
            params: Parameter resolver used
            measurements: Dictionary of measurement outcomes
            repetitions: Number of repetitions
        """
        import cirq
        import numpy as np

        self.params = params
        self.measurements = measurements
        self.repetitions = repetitions

    def histogram(self, key: str = 'result') -> Dict[int, int]:
        """Get histogram of measurement outcomes.

        Args:
            key: Measurement key

        Returns:
            Dictionary mapping outcomes to counts
        """
        if key not in self.measurements:
            return {}

        import numpy as np

        # Convert bitstrings to integers and count
        data = self.measurements[key]
        outcomes = [''.join(map(str, row)) for row in data]

        from collections import Counter
        counts = Counter(outcomes)

        # Convert binary strings to integers
        return {int(k, 2): v for k, v in counts.items()}

    def multi_measurement_histogram(self, keys: Optional[List[str]] = None) -> Dict:
        """Get histograms for multiple measurements.

        Args:
            keys: List of measurement keys (None = all)

        Returns:
            Dictionary of histograms
        """
        if keys is None:
            keys = list(self.measurements.keys())

        return {key: self.histogram(key) for key in keys}

    def __repr__(self) -> str:
        """String representation of the result."""
        return f"<HIQResult(repetitions={self.repetitions}, keys={list(self.measurements.keys())})>"


class ArvakEngine:
    """HIQ engine for Cirq.

    Provides access to Arvak backends through Cirq's Engine interface.
    """

    def __init__(self, backend_name: str = 'sim'):
        """Initialize the HIQ engine.

        Args:
            backend_name: Name of the backend to use
        """
        self.backend_name = backend_name
        self._sampler = ArvakSampler(backend_name)

    def get_sampler(self, processor_id: Optional[str] = None) -> ArvakSampler:
        """Get a sampler for this engine.

        Args:
            processor_id: Optional processor ID (unused)

        Returns:
            ArvakSampler instance
        """
        return self._sampler

    def __repr__(self) -> str:
        """String representation of the engine."""
        return f"<ArvakEngine(backend='{self.backend_name}')>"
