text: # Copyright 2018 The Cirq Developers
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #      http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  
  import json
  import urllib.parse
  from typing import List, cast, Tuple, Any, Iterable
  
  from cirq import ops, circuits, line, protocols
  from cirq.contrib.quirk.linearize_circuit import linearize_circuit_qubits
  from cirq.contrib.quirk.quirk_gate import (
      quirk_gate_ext,
      QuirkOp,
      UNKNOWN_GATE,
      single_qubit_matrix_gate)
  
  
  def _try_convert_to_quirk_gate(op: ops.Operation,
                                 prefer_unknown_gate_to_failure: bool
                                 ) -> QuirkOp:
      quirk_gate = quirk_gate_ext.try_cast(QuirkOp, op)
      if quirk_gate is not None:
          return quirk_gate
      matrix_op = single_qubit_matrix_gate(protocols.unitary(op, None))
      if matrix_op is not None:
          return matrix_op
      if prefer_unknown_gate_to_failure:
          return UNKNOWN_GATE
      raise TypeError('Unrecognized operation: {!r}'.format(op))
  
  
  def _to_quirk_cols(op: ops.Operation,
                     prefer_unknown_gate_to_failure: bool
                     ) -> Iterable[Tuple[List[Any], bool]]:
      gate = _try_convert_to_quirk_gate(op, prefer_unknown_gate_to_failure)
      qubits = cast(Iterable[line.LineQubit], op.qubits)
  
      max_index = max(q.x for q in qubits)
      col = [1] * (max_index + 1)
      for i, q in enumerate(qubits):
          col[q.x] = gate.keys[min(i, len(gate.keys) - 1)]
      yield col, gate.can_merge
  
  
  def circuit_to_quirk_url(circuit: circuits.Circuit,
                           prefer_unknown_gate_to_failure: bool=False,
                           escape_url=True) -> str:
      """Returns a Quirk URL for the given circuit.
  
      Args:
          circuit: The circuit to open in Quirk.
          prefer_unknown_gate_to_failure: If not set, gates that fail to convert
              will cause this function to raise an error. If set, a URL
              containing bad gates will be generated. (Quirk will open the URL,
              and replace the bad gates with parse errors, but still get the rest
              of the circuit.)
          escape_url: If set, the generated URL will have special characters such
              as quotes escaped using %. This makes it possible to paste the URL
              into forums and the command line and etc and have it properly
              parse. If not set, the generated URL will be more compact and human
              readable (and can still be pasted directly into a browser's address
              bar).
  
      Returns:
  
      """
      circuit = circuit.copy()
      linearize_circuit_qubits(circuit)
  
      cols = []  # Type: List[List[Any]]
      for moment in circuit:
          can_merges = []
          for op in moment.operations:
              for col, can_merge in _to_quirk_cols(
                      op,
                      prefer_unknown_gate_to_failure):
                  if can_merge:
                      can_merges.append(col)
                  else:
                      cols.append(col)
          if can_merges:
              merged_col = [1] * max(len(e) for e in can_merges)
              for col in can_merges:
                  for i in range(len(col)):
                      if col[i] != 1:
                          merged_col[i] = col[i]
              cols.append(merged_col)
  
      circuit_json = json.JSONEncoder(ensure_ascii=False,
                                      separators=(',', ':'),
                                      sort_keys=True).encode({'cols': cols})
      if escape_url:
          suffix = urllib.parse.quote(circuit_json)
      else:
          suffix = circuit_json
      return 'http://algassert.com/quirk#circuit={}'.format(suffix)
  