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Refactor flows endpoint processing #291

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Merged
kzu merged 1 commit into from
Aug 21, 2025
Merged

Refactor flows endpoint processing #291

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140 changes: 73 additions & 67 deletions src/WhatsApp/AzureFunctionsWebhook.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -44,73 +44,7 @@ public async Task<IActionResult> Message([HttpTrigger(AuthorizationLevel.Anonymo
// Detect encrypted flow request setup for flows endpoints
if (JsonSerializer.Deserialize<EncryptedFlowData>(json) is { Data.Length: > 0, IV.Length: > 0, Key.Length: > 0 } encrypted)
{
if (string.IsNullOrEmpty(metaOptions.Value.PrivateKey))
return new StatusCodeResult(421);

var crypto = new FlowCryptography(metaOptions.Value.PrivateKey);
if (!crypto.TryDecrypt(encrypted, out var data) || data is null)
return new StatusCodeResult(421);

if (data.Data.TryGetProperty("action", out var action) &&
action.ValueKind == JsonValueKind.String &&
action.GetString() == "ping")
{
// This satisfies the flow publishing requirement that the endpoint is active.
return new OkObjectResult(crypto.Encrypt(data.With(
new { data = new { status = "active" } })));
}

if (!data.Data.TryGetProperty("flow_token", out var t) ||
t.ValueKind != JsonValueKind.String || t.GetString() is not { Length: > 0 } value ||
!FlowToken.TryDecode(value, out var token))
{
logger.LogWarning("Received flow request without a valid flow_token.");
return new BadRequestObjectResult("Missing or invalid flow_token.");
}

var node = JsonObject.Create(data.Data);
Debug.Assert(node != null, "Node should not be null after decryption.");

node.Add("service", token.ServiceId);
node.Add("user", token.UserNumber);

var flow = JsonSerializer.Deserialize<FlowDataRequest>(node, JsonContext.DefaultOptions);
if (flow?.Flow is null)
{
logger.LogWarning("Failed to deserialize flow message from: {Json}", json);
return new BadRequestObjectResult("Invalid flow message format.");
}

FlowDataResponse? flowResponse = default;

await foreach (var response in handler.HandleAsync([flow]))
{
if (response is FlowDataResponse fdr)
{
if (flowResponse is not null)
{
logger.LogWarning("At most one flow data response can be provided for {Token}", token.RawToken);
return new ConflictObjectResult("Multiple flow data responses are not allowed.");
}
else
{
flowResponse = fdr;
}
}
}

if (flowResponse is null)
{
logger.LogWarning("No flow data response provided for {Token}", token.RawToken);
return new NotFoundObjectResult("No flow data response provided.");
}

return new OkObjectResult(crypto.Encrypt(data.With(
new
{
screen = flowResponse.Screen,
data = flowResponse.Data
})));
return await ProcessFlowDataAsync(json, encrypted);
}

if (await WhatsApp.Message.DeserializeAsync(json) is { } message)
Expand Down Expand Up @@ -161,6 +95,78 @@ public async Task<IActionResult> Message([HttpTrigger(AuthorizationLevel.Anonymo
return new OkResult();
}


async Task<IActionResult> ProcessFlowDataAsync(string json, EncryptedFlowData encrypted)
{
if (string.IsNullOrEmpty(metaOptions.Value.PrivateKey))
return new StatusCodeResult(421);

var crypto = new FlowCryptography(metaOptions.Value.PrivateKey);
if (!crypto.TryDecrypt(encrypted, out var data) || data is null)
return new StatusCodeResult(421);

if (data.Data.TryGetProperty("action", out var action) &&
action.ValueKind == JsonValueKind.String &&
action.GetString() == "ping")
{
// This satisfies the flow publishing requirement that the endpoint is active.
return new OkObjectResult(crypto.Encrypt(data.With(
new { data = new { status = "active" } })));
}

if (!data.Data.TryGetProperty("flow_token", out var t) ||
t.ValueKind != JsonValueKind.String || t.GetString() is not { Length: > 0 } value ||
!FlowToken.TryDecode(value, out var token))
{
logger.LogWarning("Received flow request without a valid flow_token.");
return new BadRequestObjectResult("Missing or invalid flow_token.");
}

var node = JsonObject.Create(data.Data);
Debug.Assert(node != null, "Node should not be null after decryption.");

node.Add("service", token.ServiceId);
node.Add("user", token.UserNumber);

var flow = JsonSerializer.Deserialize<FlowDataRequest>(node, JsonContext.DefaultOptions);
if (flow?.Flow is null)
{
logger.LogWarning("Failed to deserialize flow message from: {Json}", json);
return new BadRequestObjectResult("Invalid flow message format.");
}

FlowDataResponse? flowResponse = default;

await foreach (var response in handler.HandleAsync([flow]))
{
if (response is FlowDataResponse fdr)
{
if (flowResponse is not null)
{
logger.LogWarning("At most one flow data response can be provided for {Token}", token.RawToken);
return new ConflictObjectResult("Multiple flow data responses are not allowed.");
}
else
{
flowResponse = fdr;
}
}
}

if (flowResponse is null)
{
logger.LogWarning("No flow data response provided for {Token}", token.RawToken);
return new NotFoundObjectResult("No flow data response provided.");
}

return new OkObjectResult(crypto.Encrypt(data.With(
new
{
screen = flowResponse.Screen,
data = flowResponse.Data
})));
}

[Function("whatsapp_register")]
public IActionResult Register([HttpTrigger(AuthorizationLevel.Anonymous, "get", Route = "whatsapp")] HttpRequest req)
{
Expand Down
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