"""
Base Compiler Classes for BioQL

This module provides the base classes and interfaces for compiling BioQL IR
into backend-specific quantum circuits.
"""

from abc import ABC, abstractmethod
from typing import Any, Dict, List, Optional, Tuple, Union

# Optional loguru import
try:
    from loguru import logger
except ImportError:
    import logging
    logger = logging.getLogger(__name__)

from bioql.ir import (
    AlignmentOperation,
    BioQLOperation,
    BioQLProgram,
    BioQLResult,
    DockingOperation,
    QuantumBackend,
    QuantumOptimizationOperation,
)


class CompilationError(Exception):
    """Exception raised when compilation fails."""
    pass


class QuantumCircuitInterface(ABC):
    """Abstract interface for quantum circuits across different backends."""

    @abstractmethod
    def add_hadamard(self, qubit: int) -> None:
        """Add a Hadamard gate."""
        pass

    @abstractmethod
    def add_pauli_x(self, qubit: int) -> None:
        """Add a Pauli-X gate."""
        pass

    @abstractmethod
    def add_pauli_y(self, qubit: int) -> None:
        """Add a Pauli-Y gate."""
        pass

    @abstractmethod
    def add_pauli_z(self, qubit: int) -> None:
        """Add a Pauli-Z gate."""
        pass

    @abstractmethod
    def add_cnot(self, control: int, target: int) -> None:
        """Add a CNOT gate."""
        pass

    @abstractmethod
    def add_rotation_x(self, qubit: int, angle: float) -> None:
        """Add a rotation-X gate."""
        pass

    @abstractmethod
    def add_rotation_y(self, qubit: int, angle: float) -> None:
        """Add a rotation-Y gate."""
        pass

    @abstractmethod
    def add_rotation_z(self, qubit: int, angle: float) -> None:
        """Add a rotation-Z gate."""
        pass

    @abstractmethod
    def add_measurement(self, qubit: int, classical_bit: int) -> None:
        """Add a measurement."""
        pass

    @abstractmethod
    def get_depth(self) -> int:
        """Get circuit depth."""
        pass

    @abstractmethod
    def get_gate_count(self) -> int:
        """Get total gate count."""
        pass

    @abstractmethod
    def to_qasm(self) -> str:
        """Export circuit to OpenQASM."""
        pass


class BaseCompiler(ABC):
    """Base class for BioQL compilers."""

    def __init__(self, backend: QuantumBackend):
        self.backend = backend
        self.logger = logger.bind(compiler=self.__class__.__name__)

    @abstractmethod
    def compile_program(self, program: BioQLProgram) -> Any:
        """
        Compile a BioQL program into a backend-specific representation.

        Args:
            program: BioQL program to compile

        Returns:
            Backend-specific compiled program

        Raises:
            CompilationError: If compilation fails
        """
        pass

    @abstractmethod
    def execute(self, compiled_program: Any, shots: int = 1000, program_id: Optional[str] = None) -> BioQLResult:
        """
        Execute a compiled program.

        Args:
            compiled_program: Compiled program
            shots: Number of shots

        Returns:
            Execution results

        Raises:
            CompilationError: If execution fails
        """
        pass

    def compile_and_execute(self, program: BioQLProgram) -> BioQLResult:
        """
        Convenience method to compile and execute a program.

        Args:
            program: BioQL program

        Returns:
            Execution results
        """
        self.logger.info(f"Compiling program: {program.name}")
        compiled = self.compile_program(program)

        self.logger.info(f"Executing program with {program.shots} shots")
        return self.execute(compiled, program.shots)

    @abstractmethod
    def _compile_docking_operation(
        self,
        operation: DockingOperation,
        circuit: QuantumCircuitInterface
    ) -> None:
        """Compile a docking operation into quantum gates."""
        pass

    @abstractmethod
    def _compile_alignment_operation(
        self,
        operation: AlignmentOperation,
        circuit: QuantumCircuitInterface
    ) -> None:
        """Compile an alignment operation into quantum gates."""
        pass

    @abstractmethod
    def _compile_optimization_operation(
        self,
        operation: QuantumOptimizationOperation,
        circuit: QuantumCircuitInterface
    ) -> None:
        """Compile an optimization operation into quantum gates."""
        pass

    def _estimate_qubits_needed(self, program: BioQLProgram) -> int:
        """Estimate the number of qubits needed for a program."""
        base_qubits = 4  # Minimum qubits for any operation

        for operation in program.operations:
            if isinstance(operation, DockingOperation):
                # Estimate based on molecular complexity
                # For now, use a simple heuristic
                base_qubits += 6
            elif isinstance(operation, AlignmentOperation):
                # Estimate based on sequence length
                max_seq_len = max(len(seq.data) for seq in operation.sequences)
                base_qubits += min(max_seq_len // 10, 10)  # Cap at 10 extra qubits
            elif isinstance(operation, QuantumOptimizationOperation):
                # Estimate based on number of variables
                base_qubits += len(operation.variables) * 2

        return min(base_qubits, 50)  # Cap at 50 qubits for practical reasons

    def _create_molecular_encoding_circuit(
        self,
        circuit: QuantumCircuitInterface,
        molecule_data: str,
        start_qubit: int,
        num_qubits: int
    ) -> None:
        """
        Create a basic molecular encoding using quantum gates.

        This is a simplified encoding that maps molecular properties
        to quantum states using rotation gates.
        """
        # Simple hash-based encoding
        molecular_hash = hash(molecule_data) % (2**num_qubits)

        for i in range(num_qubits):
            qubit = start_qubit + i
            # Encode bit i of the hash
            if (molecular_hash >> i) & 1:
                circuit.add_pauli_x(qubit)

            # Add some superposition
            circuit.add_hadamard(qubit)

            # Add rotation based on molecular properties
            # Simple heuristic: use character codes
            if i < len(molecule_data):
                angle = (ord(molecule_data[i]) % 256) * 3.14159 / 128
                circuit.add_rotation_y(qubit, angle)

    def _create_entangling_layer(
        self,
        circuit: QuantumCircuitInterface,
        qubits: List[int]
    ) -> None:
        """Create an entangling layer between qubits."""
        for i in range(len(qubits) - 1):
            circuit.add_cnot(qubits[i], qubits[i + 1])

    def _create_variational_layer(
        self,
        circuit: QuantumCircuitInterface,
        qubits: List[int],
        parameters: List[float]
    ) -> None:
        """Create a variational layer with parameterized gates."""
        param_idx = 0
        for qubit in qubits:
            if param_idx < len(parameters):
                circuit.add_rotation_y(qubit, parameters[param_idx])
                param_idx += 1
            if param_idx < len(parameters):
                circuit.add_rotation_z(qubit, parameters[param_idx])
                param_idx += 1


class MockQuantumCircuit(QuantumCircuitInterface):
    """Mock quantum circuit for testing and fallback."""

    def __init__(self, num_qubits: int):
        self.num_qubits = num_qubits
        self.gates: List[Dict[str, Any]] = []
        self.measurements: List[Tuple[int, int]] = []

    def add_hadamard(self, qubit: int) -> None:
        self.gates.append({"type": "h", "qubit": qubit})

    def add_pauli_x(self, qubit: int) -> None:
        self.gates.append({"type": "x", "qubit": qubit})

    def add_pauli_y(self, qubit: int) -> None:
        self.gates.append({"type": "y", "qubit": qubit})

    def add_pauli_z(self, qubit: int) -> None:
        self.gates.append({"type": "z", "qubit": qubit})

    def add_cnot(self, control: int, target: int) -> None:
        self.gates.append({"type": "cnot", "control": control, "target": target})

    def add_rotation_x(self, qubit: int, angle: float) -> None:
        self.gates.append({"type": "rx", "qubit": qubit, "angle": angle})

    def add_rotation_y(self, qubit: int, angle: float) -> None:
        self.gates.append({"type": "ry", "qubit": qubit, "angle": angle})

    def add_rotation_z(self, qubit: int, angle: float) -> None:
        self.gates.append({"type": "rz", "qubit": qubit, "angle": angle})

    def add_measurement(self, qubit: int, classical_bit: int) -> None:
        self.measurements.append((qubit, classical_bit))

    def get_depth(self) -> int:
        # Simple depth calculation (could be optimized)
        return len(self.gates)

    def get_gate_count(self) -> int:
        return len(self.gates)

    def to_qasm(self) -> str:
        """Generate OpenQASM representation."""
        qasm_lines = [
            "OPENQASM 2.0;",
            'include "qelib1.inc";',
            f"qreg q[{self.num_qubits}];",
            f"creg c[{len(self.measurements)}];"
        ]

        for gate in self.gates:
            if gate["type"] == "h":
                qasm_lines.append(f"h q[{gate['qubit']}];")
            elif gate["type"] == "x":
                qasm_lines.append(f"x q[{gate['qubit']}];")
            elif gate["type"] == "y":
                qasm_lines.append(f"y q[{gate['qubit']}];")
            elif gate["type"] == "z":
                qasm_lines.append(f"z q[{gate['qubit']}];")
            elif gate["type"] == "cnot":
                qasm_lines.append(f"cx q[{gate['control']}],q[{gate['target']}];")
            elif gate["type"] == "rx":
                qasm_lines.append(f"rx({gate['angle']}) q[{gate['qubit']}];")
            elif gate["type"] == "ry":
                qasm_lines.append(f"ry({gate['angle']}) q[{gate['qubit']}];")
            elif gate["type"] == "rz":
                qasm_lines.append(f"rz({gate['angle']}) q[{gate['qubit']}];")

        for i, (qubit, cbit) in enumerate(self.measurements):
            qasm_lines.append(f"measure q[{qubit}] -> c[{i}];")

        return "\n".join(qasm_lines)


# Export main classes
__all__ = [
    "BaseCompiler",
    "CompilationError",
    "QuantumCircuitInterface",
    "MockQuantumCircuit"
]