LE003: KEY-VALUE DATABASE (MAPS + PERSISTANCE SIMULATION + RESULT + OPTION)

---
{
  "@context": "https://nxdlang.org/schema",
  "doc_id": "LE003",
  "title": "",
  "description": "",
  "layer": "Examples",
  "category": "Large Examples",
  "keywords": [],
  "doc_version": "1.0",
  "status": "active"
}
---

# LE003: KEY-VALUE DATABASE (MAPS + PERSISTANCE SIMULATION + RESULT + OPTION)

### NXD
```nxd
MODULE db.core

TYPE OPTION UNION { SOME(any), NONE }
TYPE RESULT UNION { OK(any), ERR(string) }

LET STORE SET MAP<string, string> {}

FUNC PUT(KEY: string, VAL: string): RESULT:
    STORE[KEY] SET VAL
    RETURN OK("stored")

FUNC GET(KEY: string): OPTION:
    IF STORE HAS KEY:
        RETURN SOME(STORE[KEY])
    RETURN NONE

FUNC DELETE(KEY: string): RESULT:
    IF STORE HAS KEY:
        REMOVE STORE[KEY]
        RETURN OK("deleted")
    RETURN ERR("missing key")


MODULE db.admin
IMPORT db.core

FUNC DUMP():
    LOOP K IN KEYS(STORE):
        PRINTLN(K ADD "=" ADD STORE[K])
    RETURN NONE


MODULE app.main
IMPORT db.core
IMPORT db.admin

FUNC MAIN():
    PRINTLN(PUT("host", "localhost"))
    PRINTLN(PUT("port", "8080"))

    MATCH GET("host"):
        CASE SOME(V): PRINTLN("host=" ADD V)
        CASE NONE: PRINTLN("missing host")

    PRINTLN(DELETE("port"))
    PRINTLN(DELETE("port"))

    DUMP()

    RETURN NONE
```