ccp.docs/source/methods_development/02.1_basic_docker_image.md

# Implementation of simple algorithms

Simple algorithms can be implemented using a generic unix docker image, and totally defined in the json script.

Examples of this algorithms are parametric `curl` or `wget` operations on external APIs, shell for file processing, etc

## Default ccpimage for simple algorithms

To implement methods that doesn't need any particular library or configuration, we can leave empty the `ccpimage` value, to use a basic Linux Docker image.

![ccpimage bash](../_static/imgs/methods_development/input_ccpimage_bash.png)

```json
{
    "inputs": {
        "ccpimage": {
            "id": "ccpimage",
            "title": "Runtime",
            "description": "`bash`, a basic unix docker image.",
            "minOccurs": 1,
            "maxOccurs": 1, 
            "schema": {
                "type": "string",
                "format": "url",
                "contentMediaType": "text/plain",
                "default": "",
                "readOnly": true
            }
        }
    }
}
```

## Execution Parameters

all the parameters and configurations needed for the execution of the algorithms are defined in the inputs section

```json
{
    "inputs": {
        "baseurl": {
            "id": "baseurl",
            "title": "Base URL",
            "description": "The base URL of the REST API",
            "minOccurs": 1,
            "maxOccurs": 1,
            "schema": {
                "type": "string",
                "format": "url",
                "contentMediaType": "text/plain",
                "default": "https://REST_API_URL/process/",
                "readOnly": true
            }
        },
        "service": {
            "id": "service",
            "title": "Service name",
            "description": "The name of the service",
            "minOccurs": 1,
            "maxOccurs": 1,
            "schema": {
                "type": "string",
                "format": null,
                "contentMediaType": "text/plain",
                "default": "my_custom_service"
            }
        },
        "file": {
            "id": "file",
            "title": "Input file",
            "description": "The input file to be annotated",
            "minOccurs": 1,
            "maxOccurs": 1,
            "schema": {
                "type": "string",
                "format": "file",
                "contentMediaType": "text/plain",
                "default": ""
            }
        },
        "contenttype": {
            "id": "contenttype",
            "title": "Content type",
            "description": "The content type of the input file",
            "minOccurs": 1,
            "maxOccurs": 1,
            "schema": {
                "type": "string",
                "format": null,
                "contentMediaType": "text/plain",
                "default": "text/plain",
                "enum": [
                    "text/plain",
                    "application/pdf",
                    "text/html"
                ]
            }
        },
        "credentials": {
            "id": "credentials",
            "title": "Credentials",
            "description": "The Basic auth credentials",
            "minOccurs": 1,
            "maxOccurs": 1,
            "schema": {
                "type": "string",
                "format": "secret",
                "contentMediaType": "text/plain",
                "default": "XXXYYYZZZ"
            }
        }
    }
}
``` 

the "readOnly": true/false parameter defines what is binded in the definiton of the ccp method (readonly=true, only the `baseurl` input in the given example)
and what is parametric (readonly=false, or not defined in the input schema)

the given example uses special input parameters that will be explained in next sections

* [credentials](./03_5_credentials.md)

![secret input credentials](../_static/imgs/methods_development/input_secret_credentials.png)

* [file upload](./03_1_input_file.md

![input file](../_static/imgs/methods_development/input_file.png)

## Execution

the implementation of the algorithms is totally defined in the deploy-script and in the execute-script
```json
{
    "additionalParameters": {
        "parameters": [
            {
                "name": "deploy-script",
                "value": [
                    "echo {{file}} | base64 -d > /ccp_data/input"
                ]
            },
            {
                "name": "execute-script",
                "value": [
                    "wget {{baseurl}}/{{service}}?annotations={{annotations}} --post-file /ccp_data/input --header \"Authorization: Basic {{credentials}}\" --header \"Content-Type: {{contenttype}}\" --header \"Accept: application/json\" -O /ccp_data/annotated.json"
                ]
            },
            {
                "name": "undeploy-script",
                "value": []
            }
        ]
    }
}
```


example: [bash example ](../methods_examples/Bash%20Example-1.0.0.json)