"""
Fault-tolerant resource estimation for quantum circuits.

This module provides resource estimation capabilities for fault-tolerant quantum computing.
"""

from __future__ import annotations

from dataclasses import dataclass

from qiskit import QuantumCircuit


@dataclass
class ResourceEstimate:
    """Resource estimation results for fault-tolerant quantum computing."""

    physical_qubits: int = 0
    logical_qubits: int = 0
    t_gates: int = 0
    t_gate_depth: int = 0
    code_distance: int = 0
    runtime_hours: float = 0.0
    error_rate: float = 0.0


def estimate_circuit_resources(
    circuit: QuantumCircuit,
    target_error_rate: float = 1e-3,
    include_magic_states: bool = True,
    include_measurement: bool = True,
    shots: int = 1000,
) -> ResourceEstimate:
    """
    Estimate resources required for fault-tolerant execution of a quantum circuit.

    This is a simplified implementation that provides basic resource estimates.
    A full implementation would include detailed fault-tolerant overhead calculations.

    Args:
        circuit: The quantum circuit to analyze
        target_error_rate: Target logical error rate
        include_magic_states: Whether to include magic state distillation costs
        include_measurement: Whether to include measurement overhead

    Returns:
        ResourceEstimate with estimated resource requirements
    """
    # Basic estimation based on circuit size
    num_qubits = circuit.num_qubits
    depth = circuit.depth()

    # Simplified resource estimation
    # In a real implementation, this would use detailed FT protocols
    logical_qubits = num_qubits
    physical_qubits = logical_qubits * 1000  # Rough estimate for surface code
    t_gates = max(1, depth // 10)  # Estimate T gates needed
    t_gate_depth = t_gates // 100  # Parallelization factor

    return ResourceEstimate(
        physical_qubits=physical_qubits,
        logical_qubits=logical_qubits,
        t_gates=t_gates,
        t_gate_depth=t_gate_depth,
        code_distance=9,  # Typical surface code distance
        runtime_hours=float(depth) / 3600.0,  # Rough estimate
        error_rate=target_error_rate,
    )
