From f17cf6bb0966fd41e5077a0acb207e7a99f2e876 Mon Sep 17 00:00:00 2001
From: Chris Goller <goller@gmail.com>
Date: Wed, 19 Apr 2017 11:03:53 -0500
Subject: [PATCH] Add InfluxQL template rendering

---
 influx/templates.go      |  53 +++++++++++++++
 influx/templates_test.go | 139 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 192 insertions(+)
 create mode 100644 influx/templates.go
 create mode 100644 influx/templates_test.go

diff --git a/influx/templates.go b/influx/templates.go
new file mode 100644
index 0000000000..24f5338baa
--- /dev/null
+++ b/influx/templates.go
@@ -0,0 +1,53 @@
+package influx
+
+import "strings"
+
+// TempValue is a value use to replace a template in an InfluxQL query
+type TempValue struct {
+	Value string `json:"value"`
+	Type  string `json:"type"`
+}
+
+// TempVar is a named variable within an InfluxQL query to be replaced with Values
+type TempVar struct {
+	Var    string      `json:"tempVar"`
+	Values []TempValue `json:"values"`
+}
+
+// String converts the template variable into a correct InfluxQL string based
+// on its type
+func (t TempVar) String() string {
+	if len(t.Values) == 0 {
+		return ""
+	}
+	switch t.Values[0].Type {
+	case "tagKey", "fieldKey":
+		return `"` + t.Values[0].Value + `"`
+	case "tagValue":
+		return `'` + t.Values[0].Value + `'`
+	case "csv":
+		return t.Values[0].Value
+	default:
+		return ""
+	}
+}
+
+// TempVars are template variables to replace within an InfluxQL query
+type TempVars struct {
+	Vars []TempVar `json:"tempVars"`
+}
+
+// TemplateReplace replaces templates with values within the query string
+func TemplateReplace(query string, templates TempVars) string {
+	replacements := []string{}
+	for _, v := range templates.Vars {
+		newVal := v.String()
+		if newVal != "" {
+			replacements = append(replacements, v.Var, newVal)
+		}
+	}
+
+	replacer := strings.NewReplacer(replacements...)
+	replaced := replacer.Replace(query)
+	return replaced
+}
diff --git a/influx/templates_test.go b/influx/templates_test.go
new file mode 100644
index 0000000000..ba0ba26407
--- /dev/null
+++ b/influx/templates_test.go
@@ -0,0 +1,139 @@
+package influx
+
+import (
+	"testing"
+)
+
+func TestTemplateReplace(t *testing.T) {
+	tests := []struct {
+		name  string
+		query string
+		vars  TempVars
+		want  string
+	}{
+		{
+			name:  "select with parameters",
+			query: "$METHOD field1, $field FROM $measurement WHERE temperature > $temperature",
+			vars: TempVars{
+				Vars: []TempVar{
+					{
+						Var: "$temperature",
+						Values: []TempValue{
+							{
+								Type:  "csv",
+								Value: "10",
+							},
+						},
+					},
+					{
+						Var: "$field",
+						Values: []TempValue{
+							{
+								Type:  "fieldKey",
+								Value: "field2",
+							},
+						},
+					},
+					{
+						Var: "$METHOD",
+						Values: []TempValue{
+							{
+								Type:  "csv",
+								Value: "SELECT",
+							},
+						},
+					},
+					{
+						Var: "$measurement",
+						Values: []TempValue{
+							{
+								Type:  "csv",
+								Value: `"cpu"`,
+							},
+						},
+					},
+				},
+			},
+			want: `SELECT field1, "field2" FROM "cpu" WHERE temperature > 10`,
+		},
+		{
+			name:  "select with parameters and aggregates",
+			query: `SELECT mean($field) FROM "cpu" WHERE $tag = $value GROUP BY $tag`,
+			vars: TempVars{
+				Vars: []TempVar{
+					{
+						Var: "$value",
+						Values: []TempValue{
+							{
+								Type:  "tagValue",
+								Value: "howdy.com",
+							},
+						},
+					},
+					{
+						Var: "$tag",
+						Values: []TempValue{
+							{
+								Type:  "tagKey",
+								Value: "host",
+							},
+						},
+					},
+					{
+						Var: "$field",
+						Values: []TempValue{
+							{
+								Type:  "fieldKey",
+								Value: "field",
+							},
+						},
+					},
+				},
+			},
+			want: `SELECT mean("field") FROM "cpu" WHERE "host" = 'howdy.com' GROUP BY "host"`,
+		},
+		{
+			name:  "Non-existant parameters",
+			query: `SELECT $field FROM "cpu"`,
+			want:  `SELECT $field FROM "cpu"`,
+		},
+		{
+			name:  "var without a value",
+			query: `SELECT $field FROM "cpu"`,
+			vars: TempVars{
+				Vars: []TempVar{
+					{
+						Var: "$field",
+					},
+				},
+			},
+			want: `SELECT $field FROM "cpu"`,
+		},
+		{
+			name:  "var with unknown type",
+			query: `SELECT $field FROM "cpu"`,
+			vars: TempVars{
+				Vars: []TempVar{
+					{
+						Var: "$field",
+						Values: []TempValue{
+							{
+								Type:  "who knows?",
+								Value: "field",
+							},
+						},
+					},
+				},
+			},
+			want: `SELECT $field FROM "cpu"`,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := TemplateReplace(tt.query, tt.vars)
+			if got != tt.want {
+				t.Errorf("TestParse %s =\n%s\nwant\n%s", tt.name, got, tt.want)
+			}
+		})
+	}
+}