package idgen

import (
	"crypto/rand"
	"encoding/hex"
	"fmt"
	"io"

	"inbox/internal/base/slug"
	"inbox/internal/base/timeutil"
)

type Generator struct {
	Clock      timeutil.Clock
	Random     io.Reader
	SuffixSize int
}

func NewGenerator(clock timeutil.Clock, random io.Reader) Generator {
	if clock == nil {
		clock = timeutil.SystemClock{}
	}
	if random == nil {
		random = rand.Reader
	}
	return Generator{
		Clock:      clock,
		Random:     random,
		SuffixSize: 6,
	}
}

func (g Generator) New(kind string) (string, error) {
	prefix := slug.NormalizeWithLimit(kind, 24)
	if prefix == "" {
		prefix = "id"
	}
	size := g.SuffixSize
	if size <= 0 {
		size = 6
	}
	buf := make([]byte, size)
	if _, err := io.ReadFull(g.Random, buf); err != nil {
		return "", fmt.Errorf("generate id suffix: %w", err)
	}
	return fmt.Sprintf("%s-%s-%s", prefix, timeutil.TimestampIDPart(g.Clock.Now()), hex.EncodeToString(buf)), nil
}

func New(kind string) (string, error) {
	return NewGenerator(timeutil.SystemClock{}, rand.Reader).New(kind)
}