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1 from enum import Enum
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2 import utils.general_utils as utils
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3 from typing import List, Union, Optional
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4
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5 class RuleErr(utils.CustomErr):
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6 """
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7 CustomErr subclass for rule syntax errors.
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8 """
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9 errName = "Rule Syntax Error"
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10 def __init__(self, rule :str, msg = "no further details provided") -> None:
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11 super().__init__(
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12 f"rule \"{rule}\" is malformed, {msg}",
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13 "please verify your input follows the validity guidelines")
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14
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15 class RuleOp(Enum):
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16 """
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17 Encodes all operators valid in gene rules.
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18 """
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19 OR = "or"
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20 AND = "and"
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21
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22 @classmethod
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23 def isOperator(cls, op :str) -> bool:
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24 return op.upper() in cls.__members__
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25
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26 def __str__(self) -> str: return self.value
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27
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28 class OpList(List[Union[str, "OpList"]]):
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29 """
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30 Represents a parsed rule and each of its nesting levels, including the operator that level uses.
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31 """
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32 def __init__(self, op :Optional[RuleOp] = None) -> None:
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33 """
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34 (Private) Initializes an instance of OpList.
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35
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36 Args:
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37 op (str): Operator to be assigned to the OpList. Defaults to "".
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38
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39 Returns:
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40 None : practically, an OpList instance.
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41 """
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42 self.op = op
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43
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44 def setOpIfMissing(self, op :RuleOp) -> None:
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45 """
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46 Sets the operator of the OpList if it's missing.
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47
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48 Args:
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49 op (str): Operator to be assigned to the OpList.
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50
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51 Returns:
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52 None
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53 """
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54 if not self.op: self.op = op
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55
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56 def __repr__(self, indent = "") -> str:
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57 """
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58 (Private) Returns a string representation of the current OpList instance.
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59
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60 Args:
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61 indent (str): Indentation level . Defaults to "".
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62
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63 Returns:
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64 str: A string representation of the current OpList instance.
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65 """
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66 nextIndent = indent + " "
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67 return f"<{self.op}>[\n" + ",\n".join([
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68 f"{nextIndent}{item.__repr__(nextIndent) if isinstance(item, OpList) else item}"
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69 for item in self ]) + f"\n{indent}]"
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70
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71 class RuleStack:
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72 """
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73 FILO stack structure to save the intermediate representation of a Rule during parsing, with the
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74 current nesting level at the top of the stack.
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75 """
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76 def __init__(self) -> None:
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77 """
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78 (Private) initializes an instance of RuleStack.
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79
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80 Returns:
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81 None : practically, a RuleStack instance.
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82 """
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83 self.__stack = [OpList()] # the stack starts out with the result list already allocated
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84 self.__updateCurrent()
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85
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86 def pop(self) -> None:
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87 """
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88 Removes the OpList on top of the stack, also flattening it once when possible.
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89
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90 Side Effects:
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91 self : mut
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92
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93 Returns:
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94 None
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95 """
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96 oldTop = self.__stack.pop()
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97 if len(oldTop) == 1 and isinstance(oldTop[0], OpList): self.__stack[-1][-1] = oldTop[0]
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98 self.__updateCurrent()
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99
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100 def push(self, operator = "") -> None:
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101 """
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102 Adds a new nesting level, in the form of a new OpList on top of the stack.
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103
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104 Args:
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105 operator : the operator assigned to the new OpList.
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106
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107 Side Effects:
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108 self : mut
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109
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110 Returns:
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111 None
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112 """
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113 newLevel = OpList(operator)
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114 self.current.append(newLevel)
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115 self.__stack.append(newLevel)
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116 self.__updateCurrent()
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117
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118 def popForward(self) -> None:
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119 """
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120 Moves the last "actual" item from the 2nd to last list to the beginning of the top list, as per
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121 the example below:
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122 stack : [list_a, list_b]
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123 list_a : [item1, item2, list_b] --> [item1, list_b]
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124 list_b : [item3, item4] --> [item2, item3, item4]
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125
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126 This is essentially a "give back as needed" operation.
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127
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128 Side Effects:
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129 self : mut
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130
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131 Returns:
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132 None
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133 """
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134 self.current.insert(0, self.__stack[-2].pop(-2))
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135
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136 def currentIsAnd(self) -> bool:
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137 """
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138 Checks if the current OpList's assigned operator is "and".
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139
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140 Returns:
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141 bool : True if the current OpList's assigned operator is "and", False otherwise.
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142 """
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143 return self.current.op is RuleOp.AND
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144
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145 def obtain(self, err :Optional[utils.CustomErr] = None) -> Optional[OpList]:
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146 """
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147 Obtains the first OpList on the stack, only if it's the only element.
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148
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149 Args:
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150 err : The error to raise if obtaining the result is not possible.
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151
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152 Side Effects:
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153 self : mut
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154
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155 Raises:
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156 err: If given, otherwise None is returned.
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157
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158 Returns:
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159 Optional[OpList]: The first OpList on the stack, only if it's the only element.
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160 """
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161
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162 if len(self.__stack) == 1: return self.__stack.pop()
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163 if err: raise err
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164 return None
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165
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166 def __updateCurrent(self) -> None:
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167 """
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168 (Private) Updates the current OpList to the one on top of the stack.
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169
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170 Side Effects:
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171 self : mut
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172
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173 Returns:
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174 None
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175 """
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176 self.current = self.__stack[-1]
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177
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178 def parseRuleToNestedList(rule :str) -> OpList:
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179 """
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180 Parse a single rule from its string representation to an OpList, making all priority explicit
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181 through nesting levels.
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182
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183 Args:
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184 rule : the string representation of a rule to be parsed.
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185
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186 Raises:
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187 RuleErr : whenever something goes wrong during parsing.
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188
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189 Returns:
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190 OpList : the parsed rule.
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191 """
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192 source = iter(rule
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193 .replace("(", "( ").replace(")", " )") # Single out parens as words
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194 .strip() # remove whitespace at extremities
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195 .split()) # split by spaces
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196
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197 stack = RuleStack()
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198 nestingErr = RuleErr(rule, "mismatch between open and closed parentheses")
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199 try:
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200 while True: # keep reading until source ends
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201 while True:
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202 operand = next(source, None) # expected name or rule opening
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203 if operand is None: raise RuleErr(rule, "found trailing open parentheses")
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204 if operand == "and" or operand == "or" or operand == ")": # found operator instead, panic
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205 raise RuleErr(rule, f"found \"{operand}\" in unexpected position")
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206
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207 if operand != "(": break # found name
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208
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209 # found rule opening, we add new nesting level but don't know the operator
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210 stack.push()
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211
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212 stack.current.append(operand)
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213
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214 while True: # keep reading until operator is found or source ends
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215 operator = next(source, None) # expected operator or rule closing
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216 if operator and operator != ")": break # found operator
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217
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218 if stack.currentIsAnd(): stack.pop() # we close the "and" chain
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219
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220 if not operator: break
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221 stack.pop() # we close the parentheses
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222
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223 # we proceed with operator:
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224 if not operator: break # there is no such thing as a double loop break.. yet
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225
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226 if not RuleOp.isOperator(operator): raise RuleErr(
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227 rule, f"found \"{operator}\" in unexpected position, expected operator")
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228
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229 operator = RuleOp(operator)
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230 if operator is RuleOp.OR and stack.currentIsAnd():
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231 stack.pop()
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232
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233 elif operator is RuleOp.AND and not stack.currentIsAnd():
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234 stack.push(operator)
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235 stack.popForward()
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236
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237 stack.current.setOpIfMissing(operator) # buffer now knows what operator its data had
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238
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239 except RuleErr as err: raise err # bubble up proper errors
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240 except: raise nestingErr # everything else is interpreted as a nesting error.
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241
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242 parsedRule = stack.obtain(nestingErr)
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243 return parsedRule[0] if len(parsedRule) == 1 and isinstance(parsedRule[0], list) else parsedRule |
