feat(eval): implements basic eval filtering

4 files changed, 36 insertions, 2 deletions

diff --git a/src/eval/index.ts b/src/eval/index.ts
new file mode 100644
index 0000000..e88b583
--- /dev/null
+++ b/src/eval/index.ts
@@ -0,0 +1,24 @@
+import {pipe} from 'fp-ts/function';
+import { Expr, ListExpr } from '../types'
+import {match} from '../utils';
+
+export const find = <T>([startO, exprs, endO]: ListExpr, list: T[]): any => {
+  const check = (e: Expr) => <T>(x: T, _i: number, _l: T[]): boolean => {
+    return pipe(
+      e.tag as any,
+      match({
+        AnyItem: () => true,
+        AnyNumber: () => typeof x === 'number',
+        AnyString: () => typeof x === 'string',
+        AnyBool: () => typeof x === 'boolean',
+        Truthy: () => !!x,
+        Falsey: () => !x,
+        _: () => false,
+      })
+    )
+  };
+  
+  const cs = exprs.map(check)
+
+  return list.filter((x, i, ls) => cs.every(c => c(x, i, ls)))
+}
diff --git a/src/parser/index.ts b/src/parser/index.ts
index b8e6764..4ad3e7b 100644
--- a/src/parser/index.ts
+++ b/src/parser/index.ts
@@ -12,7 +12,7 @@ import {
   symbol,
   tuple3,
 } from './utils'
-import { Expr } from '../types'
+import { Expr, ListExpr } from '../types'
 
 export const start = mapTo(symbol('^'), _ => Expr.Start(null))
 export const end = mapTo(symbol('$'), _ => Expr.End(null))
@@ -67,7 +67,7 @@ export const expressionP: Parser<Expr> = (input: string) =>
     wrapAlt,
   )
 
-export const parser = tuple3(optional(start), many1(expressionP), optional(end))
+export const parser: Parser<ListExpr> = tuple3(optional(start), many1(expressionP), optional(end))
 
 /*
 
diff --git a/src/types.ts b/src/types.ts
index 7f6546f..979745f 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -1,3 +1,4 @@
+import {Option} from "fp-ts/lib/Option"
 import { constructors, Union } from "./utils"
 
 type ExprT = {
@@ -21,3 +22,9 @@ export type Expr = Union<ExprT>
 
 export const Expr = constructors<ExprT>()
 
+export type ListExpr = [
+  Option<Expr>,
+  Expr[],
+  Option<Expr>,
+]
+
diff --git a/src/utils.ts b/src/utils.ts
index 7e3009f..8e3abb9 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -22,3 +22,6 @@ export const constructors = <T extends Record<string, any>>(): {
       },
     },
   ) as any
+
+export const jlog = (x: any) => console.log(JSON.stringify(x, null, 2))
+