From 8e763b1b9e34626f9a28fa0b06d39d679682646a Mon Sep 17 00:00:00 2001
From: Simon Bruder <simon@sbruder.de>
Date: Tue, 5 Jan 2021 12:11:06 +0100
Subject: [PATCH] evaluator: Load bangs at build time (go generate)

---
 .gitignore                        |  1 +
 evaluator/evaluator.go            | 21 ++-----------
 evaluator/scripts/includebangs.go | 51 +++++++++++++++++++++++++++++++
 3 files changed, 54 insertions(+), 19 deletions(-)
 create mode 100644 evaluator/scripts/includebangs.go

diff --git a/.gitignore b/.gitignore
index 4257fef..4338bf7 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,2 @@
 /evaluator/vendor/
+/evaluator/bangs.go
diff --git a/evaluator/evaluator.go b/evaluator/evaluator.go
index b9c1ebc..37ca6f7 100644
--- a/evaluator/evaluator.go
+++ b/evaluator/evaluator.go
@@ -1,17 +1,14 @@
 package main
 
 import (
-	"io/ioutil"
 	"log"
 	"net/http"
 	"net/url"
 	"regexp"
 	"strings"
-
-	"gopkg.in/yaml.v2"
 )
 
-var bangs = loadBangs()
+//go:generate go run scripts/includebangs.go
 
 func main() {
 	http.HandleFunc("/eval", func(w http.ResponseWriter, r *http.Request) {
@@ -32,20 +29,6 @@ func main() {
 	log.Fatalf("Failed to start http server: %v", http.ListenAndServe(":8081", nil))
 }
 
-func loadBangs() (bangs map[string]string) {
-	data, err := ioutil.ReadFile("bangs.yml")
-	if err != nil {
-		log.Fatalf("Failed to read bangs: %v", err)
-	}
-
-	err = yaml.Unmarshal(data, &bangs)
-	if err != nil {
-		log.Fatalf("Failed to decode bangs: %v", err)
-	}
-
-	return
-}
-
 func buildSearchURL(template string, query string) (searchUrl string) {
 	searchUrl = strings.Replace(template, "%s", url.QueryEscape(query), 1)
 	searchUrl = strings.Replace(searchUrl, "%S", query, 1)
@@ -74,7 +57,7 @@ func parseBang(searchQuery string) (bang string, query string) {
 
 func evaluateBang(searchQuery string, searchEngine string) (query string, engine string) {
 	bang, query := parseBang(searchQuery)
-	engine = bangs[bang]
+	engine = getBang(bang)
 
 	if bang == "" || engine == "" {
 		return searchQuery, searchEngine
diff --git a/evaluator/scripts/includebangs.go b/evaluator/scripts/includebangs.go
new file mode 100644
index 0000000..5c00c62
--- /dev/null
+++ b/evaluator/scripts/includebangs.go
@@ -0,0 +1,51 @@
+package main
+
+import (
+	"fmt"
+	"io/ioutil"
+	"os"
+	"sort"
+
+	"gopkg.in/yaml.v2"
+)
+
+func loadBangs() (bangs map[string]string) {
+	data, err := ioutil.ReadFile("../bangs.yml")
+	if err != nil {
+		panic(fmt.Sprintf("Failed to load bangs.yml: %v", err))
+	}
+
+	err = yaml.Unmarshal(data, &bangs)
+	if err != nil {
+		panic(fmt.Sprintf("Failed to decode bangs: %v", err))
+	}
+
+	return
+}
+
+func main() {
+	bangs := loadBangs()
+
+	// generating sorted keys to have stable generated code
+	// this is not optimal, performance-wise but it runs only once at build
+	// time, so it doesn’t matter that much)
+	bangNames := []string{}
+	for bang := range bangs {
+		bangNames = append(bangNames, bang)
+	}
+	sort.Strings(bangNames)
+
+	out, err := os.Create("bangs.go")
+	if err != nil {
+		panic(fmt.Sprintf("Failed to create bangs.go: %v", err))
+	}
+
+	out.Write([]byte("// Code generated from ../../bangs.yml DO NOT EDIT.\n"))
+	out.Write([]byte("package main \n\nfunc getBang(name string) string {\n\tswitch name {\n"))
+
+	for _, bangName := range bangNames {
+		out.Write([]byte("\t\tcase `" + bangName + "`: return `" + bangs[bangName] + "`\n"))
+	}
+	out.Write([]byte("\t\tdefault: return \"\"\n"))
+	out.Write([]byte("\t}\n}\n"))
+}