Fix: parse exists ENV variable value if included in ENV value. (#31)

README.md

@@ -23,8 +23,10 @@ Create your "env" file. Name it whatever you want. Most common is `.env`.
 The file is created with key/value pairs separated by `=`.
 
 ```text
+APP_NAME=my_app
 LUCKY_ENV=development
 DEV_PORT=3002
+DB_NAME=${APP_NAME}_${LUCKY_ENV}
 ```
 
 ### Crystal code

spec/parser_spec.cr

@@ -60,6 +60,9 @@ describe LuckyEnv::Parser do
       data["SECRET_KEY_BASE"].should eq "j5I0VrpzT1Of7dhCA="
       data["ASSET_HOST"].should eq "https://luckyframework.org"
       data["ENV_WITH_SPACE"].should eq "start_end"
+      data["APP_NAME"].should eq "my_app"
+      data["DB_NAME"].should eq "my_app_development"
+      data["LITERAL"].should eq "${NOT_EXISTS_ENV}"
     end
   end
 end

spec/support/.env

@@ -3,4 +3,7 @@ LUCKY_ENV=development
 DEV_PORT=3500
 SECRET_KEY_BASE=j5I0VrpzT1Of7dhCA=
 ASSET_HOST="https://luckyframework.org"
-ENV_WITH_SPACE= start_end 
+ENV_WITH_SPACE= start_end
+APP_NAME=my_app
+DB_NAME=${APP_NAME}_${LUCKY_ENV}
+LITERAL=${NOT_EXISTS_ENV}

src/lucky_env/parser.cr

@@ -33,7 +33,19 @@ module LuckyEnv
           hash[key] = value
         end
 
-        hash
+        keys = hash.keys
+
+        hash.transform_values do |value|
+          keys.each do |key|
+            if value =~ /\$\{#{key}\}/
+              value = value.sub("${#{key}}", hash[key])
+            else
+              value
+            end
+          end
+
+          value
+        end
       else
         raise MissingFileError.new <<-ERROR
         The file #{file_path} could not be found.