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, "")
}

type AttribTypeInfo struct {
	Template string
	Imports  []string
}

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

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

	"int": {
		Template: `// %[1]s creates a "%[2]s" attribute
		func %[1]s(value int) hatmill.Attrib {
			return hatmill.Attrib{
				Key: "%[2]s",
				Value: strconv.FormatInt(int64(value), 10),
			}
		}
		`,
		Imports: []string{"strconv"},
	},
}

// Def represents a top-level definition and its required imports.
type Def struct {
	Source  string
	Imports []string
}

type Spec interface {
	Generate() Def
}

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

func (spec AttribSpec) Generate() Def {
	template := attribTypes[spec.Type].Template
	return Def{
		Source:  fmt.Sprintf(template, identifier(spec.Name), spec.Name),
		Imports: attribTypes[spec.Type].Imports,
	}
}

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

func (spec ElemSpec) Generate() Def {
	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 spec.Void {
		template = voidTemplate
	}
	return Def{
		Source: fmt.Sprintf(template, identifier(spec.Name), spec.Name),
	}
}

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

	`)
	fmt.Fprintln(buf, "package ", pkgName)
	buf.WriteString(`import "gitlab.codemonkeysoftware.net/b/hatmill"
	`)

	// Print each import only once.
	imports := make(map[string]struct{})
	for _, def := range defs {
		for _, imp := range def.Imports {
			imports[imp] = struct{}{}
		}
	}
	for imp := range imports {
		fmt.Fprintf(buf, "import \"%s\"\n", imp)
	}

	for _, def := range defs {
		buf.WriteString(def.Source)
	}

	formatted, err := format.Source(buf.Bytes())
	if err != nil {
		err = fmt.Errorf("generated invalid code: %s\nSource code:\n%s", err, buf)
	}
	return formatted, err
}

func WriteCodeFile(specs []Spec, path, pkgName string) error {
	var defs []Def
	for _, spec := range specs {
		defs = append(defs, spec.Generate())
	}
	b, err := Render(defs, pkgName)
	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 struct {
		AttribSpecs []AttribSpec `json:"attributes"`
		ElemSpecs   []ElemSpec   `json:"elements"`
	}

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

	var attribSpecs []Spec
	for _, spec := range specs.AttribSpecs {
		attribSpecs = append(attribSpecs, spec)
	}
	err = WriteCodeFile(attribSpecs, *attribPath, *attribPkg)
	if err != nil {
		log.Fatal(err)
	}

	var elemSpecs []Spec
	for _, spec := range specs.ElemSpecs {
		elemSpecs = append(elemSpecs, spec)
	}
	err = WriteCodeFile(elemSpecs, *elemPath, *elemPkg)
	if err != nil {
		log.Fatal(err)
	}

}