[Task]: Implement sample Synapse API to Ballerina service mapping

[HindujaB]

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[HindujaB]

Update:
A sample implementation was done to generate a Ballerina HTTP service from synapse API with the use of following.

• synapse configuration builder APIs
• Ballarina syntax APIs

Identified concerns:

• There are some maintainability gaps in configuration builder APIs as they are no longer used by MI. Therefore some minor issues were found when parsing the synapse projects
• MI currently uses separate APIs to create different synapse components. They are parsed in multiple calls. The tool needs to incorporate this.

[HindujaB]

[Update on 08/11/2024]

• Analysing the MI message routing sample to map it to Ballerina source.
  https://mi.docs.wso2.com/en/latest/learn/integration-tutorials/routing-requests-based-on-message-content/
  A similar ballerina code would be

import ballerina/http;
import ballerina/log;

listener http:Listener HealthcareAPI = new (8290, config = {host: "localhost"});

service /healthcare on HealthcareAPI {
    resource function post categories/[string category]/reserve(http:Caller caller, http:Request req) returns error? {
        json payload = check req.getJsonPayload();
        string Hospital = check payload.hospital;
        http:Response res;
        match Hospital {
            "grand oak community hospital" => {
                log:printInfo("", message = "Routing to " + Hospital);
                http:Client GrandOakEP = check new (string `http://localhost:9090/grandoaks/categories/${category}/reserve`);
                res = check GrandOakEP->post("", req);
            }
            "pine valley community hospital" => {
                log:printInfo("", message = "Routing to " + Hospital);
                http:Client PineValleyEP = check new (string `http://localhost:9090/pinevalley/categories/${category}/reserve`);
                res = check PineValleyEP->post("", req);
            }
            "clemency medical center" => {
                log:printInfo("", message = "Routing to " + Hospital);
                http:Client ClemencyEP = check new (string `http://localhost:9090/clemency/categories/${category}/reserve`);
                res = check ClemencyEP->post("", req);
            }
            _ => {
                log:printInfo("", message = "Invalid hospital - " + Hospital);
                res = new;
                res.setPayload(payload);
            }
        }
        check caller->respond(res);
    }
}

• Verified the mappability of the Property mediator & Log mediator
• Analysed the expression configuration and equivalent Ballerina functionality

Expressions	Reference	Ballerina construct
Variables	https://mi.docs.wso2.com/en/latest/reference/synapse-properties/expressions/#variables	Ballerina variable retrieval
Functions	https://mi.docs.wso2.com/en/latest/reference/synapse-properties/expressions/#functions	Need specific library function calls
JSONPath expressions	https://mi.docs.wso2.com/en/latest/reference/synapse-properties/expressions/#jsonpath-expressions	json navigation expressions
XPath expressions	https://mi.docs.wso2.com/en/latest/reference/synapse-properties/expressions/#xpath-expressions	XML navigation expressions with query expressions

• Identified several gaps
  • Type conversion in ballerina needs to be handled ( if there is no type parameter is present)
  • Synapse scope concept is not directly mappable ( https://mi.docs.wso2.com/en/latest/reference/synapse-properties/scopes/)
  • Error handling needs to be handled separately (Fault sequence, other runtime exceptions)