Alerting: Refactoring in api_prometheus.go to allow code reuse. (#86575)

Preparing these functions to be used by some other part of the codebase,
which does not have a `contextmodel.ReqContext`, only the normal request
structure (`url.Values`, etc). This is slightly messy because of how
Grafana allows url parameters to be in the URL or in the request body,
so we need to make sure to invoke the form parsing logic in `ReqContext`.

pkg/services/ngalert/api/api_prometheus.go

@@ -5,6 +5,7 @@ import (
 	"errors"
 	"fmt"
 	"net/http"
+	"net/url"
 	"sort"
 	"strconv"
 	"strings"
@@ -33,7 +34,33 @@ type PrometheusSrv struct {
 
 const queryIncludeInternalLabels = "includeInternalLabels"
 
+func getBoolWithDefault(vals url.Values, field string, d bool) bool {
+	f := vals.Get(field)
+	if f == "" {
+		return d
+	}
+
+	v, _ := strconv.ParseBool(f)
+	return v
+}
+
+func getInt64WithDefault(vals url.Values, field string, d int64) int64 {
+	f := vals.Get(field)
+	if f == "" {
+		return d
+	}
+
+	v, err := strconv.ParseInt(f, 10, 64)
+	if err != nil {
+		return d
+	}
+	return v
+}
+
 func (srv PrometheusSrv) RouteGetAlertStatuses(c *contextmodel.ReqContext) response.Response {
+	// As we are using req.Form directly, this triggers a call to ParseForm() if needed.
+	c.Query("")
+
 	alertResponse := apimodels.AlertResponse{
 		DiscoveryBase: apimodels.DiscoveryBase{
 			Status: "success",
@@ -44,7 +71,7 @@ func (srv PrometheusSrv) RouteGetAlertStatuses(c *contextmodel.ReqContext) respo
 	}
 
 	var labelOptions []ngmodels.LabelOption
-	if !c.QueryBoolWithDefault(queryIncludeInternalLabels, false) {
+	if !getBoolWithDefault(c.Req.Form, queryIncludeInternalLabels, false) {
 		labelOptions = append(labelOptions, ngmodels.WithoutInternalLabels())
 	}
 
@@ -145,6 +172,9 @@ func getStatesFromRequest(r *http.Request) ([]eval.State, error) {
 }
 
 func (srv PrometheusSrv) RouteGetRuleStatuses(c *contextmodel.ReqContext) response.Response {
+	// As we are using req.Form directly, this triggers a call to ParseForm() if needed.
+	c.Query("")
+
 	dashboardUID := c.Query("dashboard_uid")
 	panelID, err := getPanelIDFromRequest(c.Req)
 	if err != nil {
@@ -154,9 +184,9 @@ func (srv PrometheusSrv) RouteGetRuleStatuses(c *contextmodel.ReqContext) respon
 		return ErrResp(http.StatusBadRequest, errors.New("panel_id must be set with dashboard_uid"), "")
 	}
 
-	limitGroups := c.QueryInt64WithDefault("limit", -1)
+	limitGroups := getInt64WithDefault(c.Req.Form, "limit", -1)
-	limitRulesPerGroup := c.QueryInt64WithDefault("limit_rules", -1)
+	limitRulesPerGroup := getInt64WithDefault(c.Req.Form, "limit_rules", -1)
-	limitAlertsPerRule := c.QueryInt64WithDefault("limit_alerts", -1)
+	limitAlertsPerRule := getInt64WithDefault(c.Req.Form, "limit_alerts", -1)
 	matchers, err := getMatchersFromRequest(c.Req)
 	if err != nil {
 		return ErrResp(http.StatusBadRequest, err, "")
@@ -180,7 +210,7 @@ func (srv PrometheusSrv) RouteGetRuleStatuses(c *contextmodel.ReqContext) respon
 	}
 
 	var labelOptions []ngmodels.LabelOption
-	if !c.QueryBoolWithDefault(queryIncludeInternalLabels, false) {
+	if !getBoolWithDefault(c.Req.Form, queryIncludeInternalLabels, false) {
 		labelOptions = append(labelOptions, ngmodels.WithoutInternalLabels())
 	}