package gen

import (
	"bytes"
	"fmt"
	"go/format"
	"strings"

	"github.com/mmcloughlin/avo/internal/inst"
)

const pkg = "github.com/mmcloughlin/avo"

type Interface interface {
	Generate([]inst.Instruction) ([]byte, error)
}

type Func func([]inst.Instruction) ([]byte, error)

func (f Func) Generate(is []inst.Instruction) ([]byte, error) {
	return f(is)
}

type Config struct {
	Name string
	Argv []string
}

func (c Config) GeneratedBy() string {
	if c.Argv == nil {
		return c.Name
	}
	return fmt.Sprintf("command: %s", strings.Join(c.Argv, " "))
}

func (c Config) GeneratedWarning() string {
	return fmt.Sprintf("Code generated by %s. DO NOT EDIT.", c.GeneratedBy())
}

type Builder func(Config) Interface

// GoFmt formats Go code produced from the given generator.
func GoFmt(i Interface) Interface {
	return Func(func(is []inst.Instruction) ([]byte, error) {
		b, err := i.Generate(is)
		if err != nil {
			return nil, err
		}
		return format.Source(b)
	})
}

type printer struct {
	buf bytes.Buffer
	err error
}

func (p *printer) Printf(format string, args ...interface{}) {
	if p.err != nil {
		return
	}
	_, p.err = fmt.Fprintf(&p.buf, format, args...)
}

func (p *printer) Result() ([]byte, error) {
	return p.buf.Bytes(), p.err
}