# Map Transformation Service

Transforms the input by mapping it to another string. It expects the mappings to be read from a file which is stored under the `transform` folder.
The file name must have the `.map` extension. 

This file should be in property syntax, i.e. simple lines with "key=value" pairs. 
The file format is documented [here](https://docs.oracle.com/javase/8/docs/api/java/util/Properties.html#load-java.io.Reader-).
To organize the various transformations one might use subfolders.

A default value can be provided if no matching entry is found by using "=value" syntax

## Example

transform/binary.map:

```properties
key=value
1=ON
0=OFF
ON=1
OFF=0
=default
```

| input      | output    |
|------------|-----------|
| `1`        | `ON`      |
| `OFF`      | `0`       |
| `key`      | `value`   |
| `anything` | `default` |

## Usage as a Profile

The functionality of this `TransformationService` can be used in a `Profile` on an `ItemChannelLink` too.
To do so, it can be configured in the `.items` file as follows:

```java
String <itemName> { channel="<channelUID>"[profile="transform:MAP", function="<filename>", sourceFormat="<valueFormat>"]}
```

The mapping filename (within the `transform` folder) has to be set in the `function` parameter.
The parameter `sourceFormat` is optional and can be used to format the input value **before** the transformation, i.e. `%.3f`.
If omitted the default is `%s`, so the input value will be put into the transformation without any format changes.

Please note: This profile is a one-way transformation, i.e. only values from a device towards the item are changed, the other direction is left untouched.
