package redisactivity

import (
	"context"
	"time"

	"proxy-pool/internal/domain/activitypool"
)

var _ activitypool.ProxyUpstreamReader = (*Adapter)(nil)

// UpstreamForProxy is a Controller-only metadata lookup. It returns neither
// the proxy record nor its credentials and is never used by the Gateway path.
func (a *Adapter) UpstreamForProxy(ctx context.Context, proxyID string, now time.Time) (string, error) {
	if ctx == nil {
		return "", activitypool.ErrInvalidProxyLookup
	}
	if err := ctx.Err(); err != nil {
		return "", err
	}
	if a == nil || proxyID == "" || now.IsZero() {
		return "", activitypool.ErrInvalidProxyLookup
	}
	result, err := runScript(ctx, a.client, upstreamLookupScript, []string{a.keys.records}, now.UnixMilli(), proxyID)
	if err != nil {
		return "", err
	}
	var reply upstreamLookupScriptReply
	if err := decodeScriptResult(result, &reply); err != nil {
		return "", err
	}
	switch reply.Status {
	case scriptOK:
		if reply.Upstream == "" {
			return "", invalidScriptReply("upstream lookup reply omitted upstream")
		}
		return reply.Upstream, nil
	case scriptNotFound:
		return "", activitypool.ErrActivityNotFound
	case scriptInvalid:
		return "", activitypool.ErrInvalidProxyLookup
	default:
		return "", invalidScriptReply("unexpected upstream lookup status")
	}
}