<!-- retryCount is specified in Named Values. -->
<policies>
    <inbound>
        <base />
        <set-variable name="retryCount" value="@(int.Parse("{{retryCount}}"))" />
        <set-variable name="maxRetryCount" value="@((int)context.Variables["retryCount"] -1)" />
        <authentication-managed-identity resource="https://cognitiveservices.azure.com" />
    </inbound>
    <backend>
        <retry condition="@(context.Response.StatusCode >= 300)"
               count="@((int)context.Variables["maxRetryCount"])" 
               interval="1" max-interval="10" delta="1" first-fast-retry="false">
            <!-- forward request and request body is stored for retry -->
            <forward-request buffer-request-body="true" />
        </retry>
    </backend>
    <outbound>
        <base />
    </outbound>
    <on-error>
        <base />
    </on-error>
</policies>

<policies>
    <inbound>
        <base />
        ...
        <set-backend-service base-url="Base URL" />
    </inbound>
    ...
</policies>

<retry
    condition="Boolean expression or literal"
    count="number of retry attempts"
    interval="retry interval in seconds"
    max-interval="maximum retry interval in seconds"
    delta="retry interval delta in seconds"
    first-fast-retry="boolean expression or literal">
    <!-- One or more child policies. No restrictions. -->
</retry>

<forward-request buffer-request-body="true" />

<!-- URLs and retryCount are retrieved from Named values -->
<policies>
    <inbound>
        <base />
        <!-- URLs retrieved from Named values -->
        <set-variable name="URL" value="@(JArray.FromObject("{{URLs}}".Split(',')))" />
        <!-- # of URLs retrieved from Named values -->
        <set-variable name="urlCount" value="@(((JArray)context.Variables["URL"]).Count)" />
        <!-- Max # of retries for each URL -->
        <set-variable name="retryCount" value="@(int.Parse("{{retryCount}}"))" />
        <!-- Max # of retries in retry policy -->
        <set-variable name="maxRetryCount" value="@((int)context.Variables["retryCount"] * (int)context.Variables["urlCount"]) - 1" />
        <!-- Loop Counter for URLs -->
        <set-variable name="urlLoop" value="@(0)" />
        <!-- Invoked URL for visibility -->
        <set-variable name="OpenAI-Instance-Invoked" value="@{
            JArray jarray = (JArray)context.Variables["URL"];
            return jarray[(int)context.Variables["urlLoop"]].ToString();
        }" />
        <!-- Initialize backend service URL -->
        <set-backend-service base-url="@((string)context.Variables["OpenAI-Instance-Invoked"])" />
        <set-variable name="attempt" value="@(0)" />
        <set-variable name="continue" value="@(true)" />
        <!-- Bearer token for authentication, retrieved from Managed Identity -->
        <authentication-managed-identity resource="https://cognitiveservices.azure.com" />
    </inbound>
    <backend>
        <!-- Condition: HTTP Status >= 300 and continue == true -->
        <retry condition="@(context.Response.StatusCode >= 300 && ((bool)context.Variables["continue"]))" count="@((int)context.Variables["maxRetryCount"])" interval="1" max-interval="10" delta="1" first-fast-retry="false">
            <!-- forward request and request body is stored for retry -->
            <forward-request buffer-request-body="true" />
            <!-- Increment # of attempts -->
            <set-variable name="attempt" value="@((int)context.Variables["attempt"] + 1)" />
            <choose>
                <!-- In case of 429 -->
                <when condition="@(context.Response.StatusCode == 429)">
                    <set-variable name="attempt" value="@(0)" />
                </when>
                <!-- In other cases, no operation. -->
                <otherwise />
            </choose>
            <choose>
                <!-- If # of attempts can be divided by 3, URL should be changed. -->
                <when condition="@((int)context.Variables["attempt"] % (int)context.Variables["retryCount"] == 0)">
                    <set-variable name="urlLoop" value="@((int)context.Variables["urlLoop"] + 1)" />
                    <choose>
                        <!-- If at least one URL for trial exists -->
                        <when condition="@((int)context.Variables["urlLoop"] < (int)context.Variables["urlCount"])">
                            <set-variable name="OpenAI-Instance-Invoked" value="@{
                                JArray jarray = (JArray)context.Variables["URL"];
                                return jarray[(int)context.Variables["urlLoop"]].ToString();
                            }" />
                            <set-backend-service base-url="@((string)context.Variables["OpenAI-Instance-Invoked"])" />
                            <set-variable name="attempt" value="@(0)" />
                        </when>
                        <!-- If no URL for trial exists -->
                        <otherwise>
                            <set-variable name="OpenAI-Instance-Invoked" value="All URLs were called but no response." />
                            <set-variable name="continue" value="@(false)" />
                        </otherwise>
                    </choose>
                </when>
                <!-- In other cases, no operation. -->
                <otherwise />
            </choose>
        </retry>
    </backend>
    <outbound>
        <base />
    </outbound>
    <on-error>
        <base />
    </on-error>
</policies>