Backend: implement alerting query (#847)

* Unit tests for backend

* minor change

* Implemented querNumericItems in backend

* Added query type

* Set alerting to true

* Return TimeSeries from History

* Updated alerting feature

* Fix params marshal error

* Fix params more

* Update zabbixAPIConnector.js

* Numbers, I guess

* Params Output Type

* Output marshaling

* Unmarshal and decoder error catch

* HistoryPoint and Unmarshal fixes

* Unmarshal to History

* Revert "Update zabbixAPIConnector.js"

This reverts commit e0ffdff859b6f920893a47a709493f8076e38ef4.

* Fix unmarshaling for real

* Time range integer

* Use more zabbix.Items

* Update response_models.go

* Update zabbix_api.go

* Update models.go

* Update zabbix_api.go

* Tests

* Adding more unit tests and cleaning up additional logging

* Make history request param a pointer

* Actually store datasource in cache

* Debug logs and timings

* Handle panics gracefully

* Updated Regex filter parsing

* Removed must compile

* Clean up regex filter

pkg/models.go

@@ -1,5 +1,10 @@
 package main
 
+import (
+	"encoding/json"
+	"fmt"
+)
+
 type connectionTestResponse struct {
 	ZabbixVersion     string              `json:"zabbixVersion"`
 	DbConnectorStatus *dbConnectionStatus `json:"dbConnectorStatus"`
@@ -9,3 +14,77 @@ type dbConnectionStatus struct {
 	DsType string `json:"dsType"`
 	DsName string `json:"dsName"`
 }
+
+type requestModel struct {
+	Target queryRequest `json:"target,omitempty"`
+}
+
+type queryRequest struct {
+	Method string       `json:"method,omitempty"`
+	Params zabbixParams `json:"params,omitempty"`
+}
+
+type zabbixParamOutput struct {
+	Mode   string
+	Fields []string
+}
+
+func (p *zabbixParamOutput) MarshalJSON() ([]byte, error) {
+	if p.Mode != "" {
+		return json.Marshal(p.Mode)
+	}
+
+	return json.Marshal(p.Fields)
+}
+
+func (p *zabbixParamOutput) UnmarshalJSON(data []byte) error {
+	if p == nil {
+		return fmt.Errorf("zabbixParamOutput: UnmarshalJSON on nil pointer")
+	}
+
+	var strArray []string
+	err := json.Unmarshal(data, &strArray)
+	if err == nil {
+		p.Fields = strArray
+		return nil
+	}
+
+	var str string
+	err = json.Unmarshal(data, &str)
+	if err == nil {
+		p.Mode = str
+		return nil
+	}
+
+	return fmt.Errorf("Unsupported type: %w", err)
+
+}
+
+type zabbixParams struct {
+	Output    *zabbixParamOutput `json:"output,omitempty"`
+	SortField string             `json:"sortfield,omitempty"`
+	SortOrder string             `json:"sortorder,omitempty"`
+	Filter    map[string][]int   `json:"filter,omitempty"`
+
+	// Login
+	User     string `json:"user,omitempty"`
+	Password string `json:"password,omitempty"`
+
+	// Item GET
+	WebItems    bool     `json:"webitems,omitempty"`
+	SelectHosts []string `json:"selectHosts,omitempty"`
+	ItemIDs     []string `json:"itemids,omitempty"`
+	GroupIDs    []string `json:"groupids,omitempty"`
+	HostIDs     []string `json:"hostids,omitempty"`
+	AppIDs      []string `json:"applicationids,omitempty"`
+
+	// Host Group GET
+	RealHosts bool `json:"real_hosts,omitempty"`
+
+	// History GET
+	History *int `json:"history,omitempty,string"`
+
+	// History/Trends GET
+	TimeFrom int64 `json:"time_from,omitempty"`
+	TimeTill int64 `json:"time_till,omitempty"`
+}