Merge pull request #24 from RedisLabsModules/NotExists-suggested

NotExists -- suggested

Author: gkorland

src/lib.rs

@@ -1,7 +1,7 @@
 #[macro_use]
 extern crate redismodule;
 
-use redismodule::{Context, RedisResult, NextArg, REDIS_OK};
+use redismodule::{Context, RedisResult, NextArg, REDIS_OK, RedisError};
 use redismodule::native_types::RedisType;
 
 mod redisjson;
@@ -10,26 +10,45 @@ use crate::redisjson::RedisJSON;
 
 static REDIS_JSON_TYPE: RedisType = RedisType::new("RedisJSON");
 
+#[derive(Debug, PartialEq)]
+pub enum SetOptions {
+    NotExists,
+    AlreadyExists,
+}
+
 fn json_set(ctx: &Context, args: Vec<String>) -> RedisResult {
     let mut args = args.into_iter().skip(1);
 
     let key = args.next_string()?;
     let _path = args.next_string()?; // TODO handle this path
     let value = args.next_string()?;
 
+    let set_option = args.next()
+        .map(|op| {
+            match op.to_uppercase().as_str() {
+                "NX" => Ok(SetOptions::NotExists),
+                "XX" => Ok(SetOptions::AlreadyExists),
+                _ => Err(RedisError::Str("ERR syntax error")),
+            }
+        })
+        .transpose()?;
+
     let key = ctx.open_key_writable(&key);
+    let current = key.get_value::<RedisJSON>(&REDIS_JSON_TYPE)?;
 
-    match key.get_value::<RedisJSON>(&REDIS_JSON_TYPE)? {
-        Some(doc) => {
+    match (current, set_option) {
+        (Some(_), Some(SetOptions::NotExists)) => Ok(().into()),
+        (Some(ref mut doc), _) => {
             doc.set_value(&value)?;
+            REDIS_OK
         }
-        None => {
+        (None, Some(SetOptions::AlreadyExists)) => Ok(().into()),
+        (None, _) => {
             let doc = RedisJSON::from_str(&value)?;
             key.set_value(&REDIS_JSON_TYPE, doc)?;
+            REDIS_OK
         }
     }
-
-    REDIS_OK
 }
 
 fn json_get(ctx: &Context, args: Vec<String>) -> RedisResult {