hatmill/internal/attribgen/main.go

package main

import (
	"bufio"
	"bytes"
	"fmt"
	"go/format"
	"io/ioutil"
	"log"
	"os"
	"strings"
)

const (
	inputPath   = "attribs.txt"
	outputPath  = "attribs.go"
	packageName = "hatmill"

	boolType   = "bool"
	stringType = "string"

	stringTemplate = `func %s(value string) Attrib {
        return Attrib{
            Key: "%s",
            Value: value,
        }
    }
    `
	boolTemplate = `func %s() Attrib {
        return Attrib{
            Key: "%s",
        }
    }
    `
)

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/attribgen")
	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 attribName, attribType string
		_, err = fmt.Sscanf(line, "%s %s", &attribName, &attribType)
		if err != nil {
			log.Fatalf("error parsing input line: %s", err)
		}

		var template string
		switch attribType {
		case boolType:
			template = boolTemplate
		case stringType:
			template = stringTemplate
		default:
			log.Fatal("unknown attribute type: ", attribType)
		}
		fmt.Fprintf(&output, template, strings.Title(attribName), attribName)
	}
	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)
	}
}