Add package generator

gen/main.go

@@ -0,0 +1,131 @@
+package main
+
+import (
+	"fmt"
+	"go/ast"
+	"go/parser"
+	"go/token"
+	"io/ioutil"
+	"log"
+	"net/http"
+	"strings"
+)
+
+// Update to a newer version of Go by changing this constant.
+const goTag = "go1.13.8"
+
+type Status struct {
+	Name   string
+	Status string
+}
+
+func main() {
+	// Download and parse the statuses from the Go source code file
+	statuses, err := parseFileForStatuses()
+	if err != nil {
+		log.Fatalln("unable to download and parse file:", err)
+	}
+
+	// Generate and output the statuses for erkhttp
+	file := generateFile(statuses)
+	err = ioutil.WriteFile("http_statuses.go", []byte(file), 0655)
+	if err != nil {
+		log.Fatalln("unable to write generated file:", err)
+	}
+}
+
+func parseFileForStatuses() ([]Status, error) {
+	file, err := downloadStatusFile()
+	if err != nil {
+		return nil, err
+	}
+
+	fs := token.NewFileSet()
+	f, err := parser.ParseFile(fs, "net/http/status.go", file, parser.AllErrors)
+	if err != nil {
+		return nil, err
+	}
+
+	statuses := []Status{}
+
+	log.Println("Parsing file. Most warnings can be ignored.")
+	for _, decl := range f.Decls {
+		genDecl, ok := decl.(*ast.GenDecl)
+		if !ok {
+			log.Println("WARNING: decl not *ast.GenDecl, so skipping")
+			continue
+		}
+
+		if genDecl.Tok.String() != "const" {
+			log.Println("WARNING: tok not const, so skipping")
+			continue
+		}
+
+		for _, spec := range genDecl.Specs {
+			valSpec, ok := spec.(*ast.ValueSpec)
+			if !ok {
+				log.Println("WARNING: spec not *ast.ValueSpec, so skipping")
+				continue
+			}
+
+			if len(valSpec.Names) != 1 {
+				log.Println("WARNING: names group not len 1, so skipping")
+				continue
+			}
+			name := valSpec.Names[0].String()
+
+			if !strings.HasPrefix(name, "Status") {
+				log.Printf("WARNING: name '%s' does not start with 'Status', so skipping\n", name)
+				continue
+			}
+
+			if len(valSpec.Values) != 1 {
+				log.Println("WARNING: values group not len 1, so skipping")
+				continue
+			}
+			valueDetails := valSpec.Values[0]
+
+			valueBasicLit, ok := valueDetails.(*ast.BasicLit)
+			if !ok {
+				log.Println("WARNING: value not basic literal, so skipping")
+				continue
+			}
+			value := valueBasicLit.Value
+
+			statuses = append(statuses, Status{
+				Name:   name,
+				Status: value,
+			})
+		}
+	}
+
+	return statuses, nil
+}
+
+func downloadStatusFile() (string, error) {
+	res, err := http.Get(fmt.Sprintf("https://raw.githubusercontent.com/golang/go/%s/src/net/http/status.go", goTag))
+	if err != nil {
+		return "", err
+	}
+
+	bytes, err := ioutil.ReadAll(res.Body)
+	if err != nil {
+		return "", err
+	}
+
+	return string(bytes), nil
+}
+
+func generateFile(statuses []Status) string {
+	file := "// WARNING: THIS FILE IS GENERATED USING gen/main.go. Edit that script and regenerate this file.\n\n"
+	file += "package erkhttp\n\n"
+
+	for _, status := range statuses {
+		file += fmt.Sprintf("// %s = %s\n", status.Name, status.Status)
+		file += fmt.Sprintf("type %s struct{}\n\n", status.Name)
+		file += fmt.Sprintf("func (%s) HTTPStatus() int { return %s }\n\n", status.Name, status.Status)
+		file += fmt.Sprintf("var _ HTTPStatusable = %s{}\n\n", status.Name)
+	}
+
+	return file
+}