hatmill/internal/codegen/codegen.go

package main

import (
	"bytes"
	"encoding/json"
	"flag"
	"fmt"
	"go/format"
	"io/ioutil"
	"log"
	"strings"
)

func identifier(s string) string {
	words := strings.Split(s, "-")
	for i, word := range words {
		words[i] = strings.Title(word)
	}
	return strings.Join(words, "")
}

var attribTypes = map[string]string {
	"string":  `// %[1]s creates a "%[2]s" attribute
	func %[1]s(value string) hatmill.Attrib {
		return hatmill.Attrib{
			Key: "%[2]s",
			Value: value,
		}
	}
	`,

	"bool": `// %[1]s creates a "%[2]s" attribute
	func %[1]s() hatmill.Attrib {
		return hatmill.Attrib{
			Key: "%[2]s",
		}
	}
	`,
}

type AttribSpec struct {
	Name string     `json:"name"`
	Type string `json:"type"`
}

type AttribSpecs []AttribSpec

func (a AttribSpecs) Code() Code {
	var c Code
	const hatmillImport = "gitlab.codemonkeysoftware.net/b/hatmill"

	c.Imports = append(c.Imports, hatmillImport)
	for _, spec := range a {
		c.Defs = append(c.Defs, spec.Generate())
	}
	return c
}

type ElemSpecs []ElemSpec

func (e ElemSpecs) Code() Code {
	var c Code
	const hatmillImport = "gitlab.codemonkeysoftware.net/b/hatmill"

	c.Imports = append(c.Imports, hatmillImport)
	for _, spec := range e {
		c.Defs = append(c.Defs, spec.Generate())
	}
	return c
}

func (def AttribSpec) Generate() string {
	template := attribTypes[def.Type]
	return fmt.Sprintf(template, identifier(def.Name), def.Name)
}

type ElemSpec struct {
	Name string `json:"name"`
	Void bool   `json:"void"`
}

func (def ElemSpec) Generate() string {
	const (
		parentTemplate = `// %[1]s creates a <%[2]s> element.
        func %[1]s(attribs ...hatmill.Attrib) func(children ...hatmill.Term) hatmill.ParentElement {
            return func(children ...hatmill.Term) hatmill.ParentElement {
                return hatmill.ParentElement{
                    VoidElement: hatmill.VoidElement{
                        TagName: "%[2]s",
                        Attribs: attribs,
                    },
                    Children: children,
                }
            }
        }
        `
		voidTemplate = `// %[1]s creates a <%[2]s> element.
        func %[1]s(attribs ...hatmill.Attrib) hatmill.VoidElement {
            return hatmill.VoidElement{
                TagName: "%[2]s",
                Attribs: attribs,
            }
        }
        `
	)

	template := parentTemplate
	if def.Void {
		template = voidTemplate
	}
	return fmt.Sprintf(template, identifier(def.Name), def.Name)
}

type Specs struct {
	Attributes AttribSpecs `json:"attributes"`
	Elements   ElemSpecs   `json:"elements"`
}

// Code is a very slight abstraction of a source code file.
type Code struct {
	Package string
	Imports []string
	Defs []string
}

func (c Code) Bytes() ([]byte, error) {
	buf := new(bytes.Buffer)
	buf.WriteString(`// GENERATED BY gitlab.codemonkeysoftware.net/b/hatmill/internal/codegen
	// DO NOT EDIT!

	`)
	fmt.Fprintln(buf, "package ", c.Package)
	for _, imp := range c.Imports {
		fmt.Fprintf(buf, "import \"%s\"\n", imp)
	}
	for _, def := range c.Defs {
		buf.WriteString(def)
	}
	return format.Source(buf.Bytes())
}

type Coder interface {
	Code() Code
}

func WriteCodeFile(c Coder, path, pkg string) error {
	code := c.Code()
	code.Package = pkg
	b, err := code.Bytes()
	if err != nil {
		return err
	}
	return ioutil.WriteFile(path, b, 0644)
}

func main() {
	inputPath := flag.String("input", "", "JSON input file")
	elemPath := flag.String("elemfile", "", "generated element .go file")
	elemPkg := flag.String("elempkg", "", "generated element package name")
	attribPath := flag.String("attribfile", "", "generated attribute .go file")
	attribPkg := flag.String("attribpkg", "", "generated attribute package name")
	flag.Parse()

	input, err := ioutil.ReadFile(*inputPath)
	if err != nil {
		log.Fatal(err)
	}

	var specs Specs
	err = json.Unmarshal(input, &specs)
	if err != nil {
		log.Fatal(err)
	}

	err = WriteCodeFile(specs.Attributes, *attribPath, *attribPkg)
	if err != nil {
		log.Fatal(err)
	}

	err = WriteCodeFile(specs.Elements, *elemPath, *elemPkg)
	if err != nil {
		log.Fatal(err)
	}
}