@firehammer/jexl/dist/parser/states.js

Javascript Expression Language: Powerful context-based expression parser and evaluator

"use strict";

/*
 * Jexl
 * Copyright 2020 Tom Shawver
 */

var h = require("./handlers");

/**
 * A mapping of all states in the finite state machine to a set of instructions
 * for handling or transitioning into other states. Each state can be handled
 * in one of two schemes: a tokenType map, or a subHandler.
 *
 * Standard expression elements are handled through the tokenType object. This
 * is an object map of all legal token types to encounter in this state (and
 * any unexpected token types will generate a thrown error) to an options
 * object that defines how they're handled.  The available options are:
 *
 *      {string} toState: The name of the state to which to transition
 *          immediately after handling this token
 *      {string} handler: The handler function to call when this token type is
 *          encountered in this state.  If omitted, the default handler
 *          matching the token's "type" property will be called. If the handler
 *          function does not exist, no call will be made and no error will be
 *          generated.  This is useful for tokens whose sole purpose is to
 *          transition to other states.
 *
 * States that consume a subexpression should define a subHandler, the
 * function to be called with an expression tree argument when the
 * subexpression is complete. Completeness is determined through the
 * endStates object, which maps tokens on which an expression should end to the
 * state to which to transition once the subHandler function has been called.
 *
 * Additionally, any state in which it is legal to mark the AST as completed
 * should have a 'completable' property set to boolean true.  Attempting to
 * call {@link Parser#complete} in any state without this property will result
 * in a thrown Error.
 *
 * @type {{}}
 */
exports.states = {
  expectOperand: {
    tokenTypes: {
      literal: {
        toState: "expectBinOp"
      },
      identifier: {
        toState: "identifier"
      },
      unaryOp: {},
      openParen: {
        toState: "subExpression"
      },
      openCurl: {
        toState: "expectObjKey",
        handler: h.objStart
      },
      dot: {
        toState: "traverse"
      },
      openBracket: {
        toState: "arrayVal",
        handler: h.arrayStart
      }
    }
  },
  expectBinOp: {
    tokenTypes: {
      binaryOp: {
        toState: "expectOperand"
      },
      pipe: {
        toState: "expectTransform"
      },
      dot: {
        toState: "traverse"
      },
      question: {
        toState: "ternaryMid",
        handler: h.ternaryStart
      }
    },
    completable: true
  },
  expectTransform: {
    tokenTypes: {
      identifier: {
        toState: "postTransform",
        handler: h.transform
      }
    }
  },
  expectObjKey: {
    tokenTypes: {
      literal: {
        toState: "expectKeyValSep",
        handler: h.objKey
      },
      identifier: {
        toState: "expectKeyValSep",
        handler: h.objKey
      },
      closeCurl: {
        toState: "expectBinOp"
      }
    }
  },
  expectKeyValSep: {
    tokenTypes: {
      colon: {
        toState: "objVal"
      }
    }
  },
  postTransform: {
    tokenTypes: {
      openParen: {
        toState: "argVal"
      },
      binaryOp: {
        toState: "expectOperand"
      },
      dot: {
        toState: "traverse"
      },
      openBracket: {
        toState: "filter"
      },
      pipe: {
        toState: "expectTransform"
      }
    },
    completable: true
  },
  postArgs: {
    tokenTypes: {
      binaryOp: {
        toState: "expectOperand"
      },
      dot: {
        toState: "traverse"
      },
      openBracket: {
        toState: "filter"
      },
      pipe: {
        toState: "expectTransform"
      }
    },
    completable: true
  },
  identifier: {
    tokenTypes: {
      binaryOp: {
        toState: "expectOperand"
      },
      dot: {
        toState: "traverse"
      },
      openBracket: {
        toState: "filter"
      },
      openParen: {
        toState: "argVal",
        handler: h.functionCall
      },
      pipe: {
        toState: "expectTransform"
      },
      question: {
        toState: "ternaryMid",
        handler: h.ternaryStart
      }
    },
    completable: true
  },
  traverse: {
    tokenTypes: {
      identifier: {
        toState: "identifier"
      }
    }
  },
  filter: {
    subHandler: h.filter,
    endStates: {
      closeBracket: "identifier"
    }
  },
  subExpression: {
    subHandler: h.subExpression,
    endStates: {
      closeParen: "expectBinOp"
    }
  },
  argVal: {
    subHandler: h.argVal,
    endStates: {
      comma: "argVal",
      closeParen: "postArgs"
    }
  },
  objVal: {
    subHandler: h.objVal,
    endStates: {
      comma: "expectObjKey",
      closeCurl: "expectBinOp"
    }
  },
  arrayVal: {
    subHandler: h.arrayVal,
    endStates: {
      comma: "arrayVal",
      closeBracket: "expectBinOp"
    }
  },
  ternaryMid: {
    subHandler: h.ternaryMid,
    endStates: {
      colon: "ternaryEnd"
    }
  },
  ternaryEnd: {
    subHandler: h.ternaryEnd,
    completable: true
  }
};