sub2api/backend/internal/service/gateway_model_availability.go

package service

import (
	"context"
	"strings"
)

// ModelAvailabilityDiagnosis describes whether the requested model can be
// served by any configured account in the group, ignoring transient state
// (rate limits, quota auto-pause, runtime blocks). Handlers use this on the
// "no available accounts" error path to distinguish 404 model_not_found from
// 503 service_unavailable.
type ModelAvailabilityDiagnosis struct {
	// HasAccountsInPool is true if the group has at least one schedulable
	// account on the queried platform (or, for Anthropic/Gemini, on the
	// platform plus mixed-scheduled Antigravity accounts).
	HasAccountsInPool bool
	// HasModelSupport is true if at least one account's model mapping admits
	// the requested model.
	HasModelSupport bool
}

// ModelAvailabilityDiagnoser is implemented by gateway services that can
// report whether the requested model is configured to be served by any
// account. Both *GatewayService and *OpenAIGatewayService implement this so
// handlers in either package can share a single classifier.
type ModelAvailabilityDiagnoser interface {
	DiagnoseModelAvailabilityForPlatform(
		ctx context.Context,
		groupID *int64,
		requestedModel string,
		platform string,
	) ModelAvailabilityDiagnosis
}

// DiagnoseModelAvailabilityForPlatform inspects schedulable accounts of the
// given platform and returns whether the requested model is configured to be
// served by any of them. It deliberately ignores schedulability, rate limits,
// quotas, and runtime blocks — those are transient.
//
// Safe to call on the error path: returns {true,true} on any internal failure
// or when the inputs preclude meaningful diagnosis (empty model, etc.), so
// callers stay on the 503 fallback branch.
func (s *GatewayService) DiagnoseModelAvailabilityForPlatform(
	ctx context.Context,
	groupID *int64,
	requestedModel string,
	platform string,
) ModelAvailabilityDiagnosis {
	if s == nil {
		return ModelAvailabilityDiagnosis{HasAccountsInPool: true, HasModelSupport: true}
	}
	requestedModel = strings.TrimSpace(requestedModel)
	if requestedModel == "" {
		// No model specified — cannot decide model_not_found. Caller falls back to 503.
		return ModelAvailabilityDiagnosis{HasAccountsInPool: true, HasModelSupport: true}
	}
	if strings.TrimSpace(platform) == "" {
		// Without a platform we cannot scope the lookup; bail out to the
		// 503 branch rather than make an unscoped scan.
		return ModelAvailabilityDiagnosis{HasAccountsInPool: true, HasModelSupport: true}
	}

	// hasForcePlatform=false so Anthropic/Gemini also surface mixed-scheduled
	// Antigravity accounts, matching what selection would consider.
	accounts, _, err := s.listSchedulableAccounts(ctx, groupID, platform, false)
	if err != nil {
		// Conservative fallback: pretend everything is fine so the caller
		// returns 503 (we don't want to flip to 404 just because a lookup
		// hiccup'd).
		return ModelAvailabilityDiagnosis{HasAccountsInPool: true, HasModelSupport: true}
	}

	diag := ModelAvailabilityDiagnosis{}
	for i := range accounts {
		diag.HasAccountsInPool = true
		if s.isModelSupportedByAccountWithContext(ctx, &accounts[i], requestedModel) {
			diag.HasModelSupport = true
			return diag
		}
	}
	return diag
}