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import { Enum, constructors, match } from './utils/adt';
import * as P from './utils/parser-comb'
export type Expr = Enum<{
Call: { name: string, args: Expr[] }
Var: { name: string, defaultValue: Expr }
Identifier: string
Chain: { exprs: Expr[] }
LiteralString: string
}>
export const Expr = constructors<Expr>()
const whitespace = P.regex(/\s*/)
const consumeWhitespace = <A>(p: P.Parser<A>): P.Parser<A> => P.between(whitespace, p, whitespace)
const comma = consumeWhitespace(P.string(','))
const parens = <A>(p: P.Parser<A>): P.Parser<A> => P.between(P.string('('), p, P.string(')'))
const identifierParser = P.regex(/^[a-z][a-z0-9_-]*/i)
const identifierExprParser = P.map(identifierParser, ident => Expr.Identifier(ident))
const callExprParser = (input: string) => P.map(P.zip2(
consumeWhitespace(identifierParser),
parens(consumeWhitespace(P.sepBy(exprParser, comma))),
), ([name, args]) => Expr.Call({ name, args }))(input)
const exprParser: P.Parser<Expr> = P.or([
callExprParser,
identifierExprParser,
])
const multiExpr = P.many1(exprParser)
export const parse = (input: string): Array<Expr> => {
const res = multiExpr(input.trim());
return match(res, {
Ok: ({ value, input }) => {
if (input) {
throw new Error(`Input not consumed completely here brosky: "${input}"`)
}
return value
},
Err: ({ error, input }) => {
throw new Error(`${error}.\n Left input: ${input.slice(0, 20)}...`)
},
})
}
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