# ETL

## Introduction

We are going to do the `Transform` step of an Extract-Transform-Load.

#### ETL

Extract-Transform-Load (ETL) is a fancy way of saying, "We have some crufty, legacy data over in this system, and now we need it in this shiny new system over here, so we're going to migrate this."

(Typically, this is followed by, "We're only going to need to run this once." That's then typically followed by much forehead slapping and moaning about how stupid we could possibly be.)

#### The goal

We're going to extract some scrabble scores from a legacy system.

The old system stored a list of letters per score:

* 1 point: "A", "E", "I", "O", "U", "L", "N", "R", "S", "T",
* 2 points: "D", "G",
* 3 points: "B", "C", "M", "P",
* 4 points: "F", "H", "V", "W", "Y",
* 5 points: "K",
* 8 points: "J", "X",
* 10 points: "Q", "Z",

The shiny new scrabble system instead stores the score per letter, which makes it much faster and easier to calculate the score for a word. It also stores the letters in lower-case regardless of the case of the input letters:

* "a" is worth 1 point.
* "b" is worth 3 points.
* "c" is worth 3 points.
* "d" is worth 2 points.
* Etc.

Your mission, should you choose to accept it, is to transform the legacy data format to the shiny new format.

{% tabs %}
{% tab title="Version 1" %}
```go
package etl

import "strings"

func Transform(input map[int][]string) map[string]int {
	result := make(map[string]int)
	for i1, s1 := range input {
		for _, s2 := range s1 {
			result[strings.ToLower(s2)] = i1
		}
	}
	return result
}

```
{% endtab %}
{% endtabs %}

### Point

* Before you add data to the map, Remember you **initialize your map**. If you use var `result = map[string]int` . you can't pass the value to result.
