package config

import (
	"encoding/base64"
	"fmt"
	"os"
	"strconv"
)

type Config struct {
	HTTPAddr          string
	DatabaseURL       string
	AuthUser          string
	AuthPass          string
	EncKey            []byte
	SessionSecret     []byte
	WorkerConcurrency int
}

func Load() (Config, error) {
	c := Config{
		HTTPAddr:          getenv("HTTP_ADDR", ":8080"),
		DatabaseURL:       os.Getenv("DATABASE_URL"),
		AuthUser:          os.Getenv("AUTH_USER"),
		AuthPass:          os.Getenv("AUTH_PASS"),
		SessionSecret:     []byte(os.Getenv("SESSION_SECRET")),
		WorkerConcurrency: 4,
	}
	if v := os.Getenv("WORKER_CONCURRENCY"); v != "" {
		n, err := strconv.Atoi(v)
		if err != nil || n < 1 {
			return Config{}, fmt.Errorf("WORKER_CONCURRENCY invalid: %q", v)
		}
		c.WorkerConcurrency = n
	}
	for k, v := range map[string]string{
		"DATABASE_URL": c.DatabaseURL, "AUTH_USER": c.AuthUser,
		"AUTH_PASS": c.AuthPass, "SESSION_SECRET": string(c.SessionSecret),
	} {
		if v == "" {
			return Config{}, fmt.Errorf("%s is required", k)
		}
	}
	key, err := base64.StdEncoding.DecodeString(os.Getenv("ENC_KEY"))
	if err != nil {
		return Config{}, fmt.Errorf("ENC_KEY must be base64: %w", err)
	}
	if len(key) != 32 {
		return Config{}, fmt.Errorf("ENC_KEY must decode to 32 bytes, got %d", len(key))
	}
	c.EncKey = key
	return c, nil
}

func getenv(k, def string) string {
	if v := os.Getenv(k); v != "" {
		return v
	}
	return def
}