Added element function generator

internal/elementgen/main.go

@@ -0,0 +1,93 @@
+package main
+
+import (
+    "bufio"
+    "bytes"
+    "fmt"
+    "go/format"
+    "io/ioutil"
+    "log"
+    "os"
+    "strings"
+)
+
+const (
+    inputPath = "elements.txt"
+    outputPath = "elements.go"
+    packageName = "hatmill"
+
+    parentType = "parent"
+    emptyType = "empty"
+
+    parentTemplate = `func %s(attribs ...Attrib) func(children ...Term) *ParentElement {
+        return func(children ...Term) *ParentElement {
+            return &ParentElement{
+    			EmptyElement: EmptyElement{
+    				TagName: "%s",
+    				Attribs: attribs,
+    			},
+    			Children: children,
+    		}
+        }
+    }
+    `
+    emptyTemplate = `func %s(attribs ...Attrib) EmptyElement {
+        return EmptyElement{
+			TagName: "%s",
+			Attribs: attribs,
+		}
+    }
+    `
+)
+
+func main() {
+    inputFile, err := os.Open(inputPath)
+    if err != nil {
+        log.Fatal(err)
+    }
+    defer inputFile.Close()
+
+    var output bytes.Buffer
+
+    fmt.Fprintln(&output, "// GENERATED BY gitlab.codemonkeysoftware.net/b/hatmill/internal/elementgen")
+    fmt.Fprintln(&output, "// DO NOT EDIT!\n")
+    fmt.Fprintln(&output, "package ", packageName, "\n")
+
+    scanner := bufio.NewScanner(inputFile)
+    for scanner.Scan() {
+        line := scanner.Text()
+        if line == "" {
+            continue
+        }
+
+        var tagName, elemType string
+        _, err = fmt.Sscanf(line, "%s %s", &tagName, &elemType)
+        if err != nil {
+            log.Fatalf("error parsing input line: %s", err)
+        }
+
+        var template string
+        switch elemType {
+        case parentType:
+            template = parentTemplate
+        case emptyType:
+            template = emptyTemplate
+        default:
+            log.Fatal("unknown element type: ", elemType)
+        }
+        fmt.Fprintf(&output, template, strings.Title(tagName), tagName)
+    }
+    if err := scanner.Err(); err != nil {
+        log.Fatalf("error scanning input: %s", err)
+    }
+
+    formatted, err := format.Source(output.Bytes())
+    if err != nil {
+        log.Fatalf("error formatting output: %s", err)
+    }
+
+    err = ioutil.WriteFile(outputPath, formatted, 0644)
+    if err != nil {
+        log.Fatalf("error writing output: %s", err)
+    }
+}