@quenk/facets-parser NPM

facets-parser

Parser for a DSL for defining faceted search terms.

Installation

npm install --save-dev @quenk/facets

Usage

By itself, this module only provides functions and primitives for creating a compiler for the DSL. (See facets-mysql for an implementation example.)

The Language

The parser recognizes filters in a string that look like:

<field> <colon> <operator>? <value>

Example:

var source = 'name:"jon" or name:"jon\'s" age:>=12';

Where operator is <optional> and if not specified defaults to 'default'. The <field> part roughly matches the javascript syntax for variable identifiers, operators are currently one of >,<,>=,<=,=,!= and values are one of string, number, boolean, list (array) or a dictionary (object).

Strings are specified using double quotes ". Strings that are also valid Javascript identifiers can be specified without double quotes.o

Parsing

There is a curried function exported called parse that takes an object of key Node constructor mappings followed by the source text that produces an abstract syntax tree. The partially applied parse$ can be used instead for parsing with defaults.

parse returns an Either with the left hand side representing an error and the right the AST.

Compiling

Once you have an AST, (see src/ast for nodes) it can be compiled using the curried function compile. compile takes a Context followed by a record of Policy descriptions.

The Context provides needed functions for compile and and or expressions as well as other options. Policy descriptions are used during compilation to determine what fields are excepted and how to treat them.

You can supply the whole policy in the record or use a string to indicate it should be retrieved from the Context's policies property.