feat(npm-zod): handle discriminatedUnion

packages/npm-zod/README.md

@@ -30,3 +30,9 @@ export const model = reatomZod(User, {
   initState: JSON.parse(localStorage.getItem(KEY) || '{}'),
 })
 ```
+
+## Mapping
+
+This section describes how types coverts to a specific atoms.
+
+`union` type creates an atom with all possible state variants and `discriminatedUnion` creates an atom with all possible atoms variants.

packages/npm-zod/src/index.ts

@@ -8,6 +8,7 @@ import {
   __count,
   action,
   Action,
+  throwReatomError,
 } from '@reatom/core'
 import { isCausedBy } from '@reatom/effects'
 import {
@@ -251,13 +252,37 @@ export const reatomZod = <Schema extends z.ZodFirstPartySchemaTypes>(
       break
     }
     case z.ZodFirstPartyTypeKind.ZodUnion: {
-      // TODO @artalar not sure about this logic
       state =
         def.options.find(
           (type: z.ZodDefault<any>) => type._def.defaultValue?.(),
         ) ?? initState
       break
     }
+    case z.ZodFirstPartyTypeKind.ZodDiscriminatedUnion: {
+      const getState = (initState: any) => {
+        const state = def.options.find(
+          (type: z.ZodDiscriminatedUnionOption<string>) => {
+            try {
+              type.parse(initState);
+            } catch {
+              return undefined;
+            }
+
+            return type;
+          },
+        );
+
+        throwReatomError(!state, 'Missed init state for discriminated union');
+
+        return reatomZod(state, { sync, initState, name });
+      };
+
+      const originAtom = atom(getState(initState), name);
+      theAtom = Object.assign((ctx: Ctx, value: any) => {
+        originAtom(ctx, getState(value));
+      }, originAtom);
+      break;
+    }
     case z.ZodFirstPartyTypeKind.ZodOptional: {
       // TODO @artalar allow `undefined` in innerType
       return reatomZod(def.innerType, { sync, initState, name })