chorus/internal/config/config.go

package config

import (
	"crypto/rand"
	"encoding/base64"
	"errors"
	"fmt"
	"os"
	"strconv"
	"strings"
	"time"
)

type Environment string

const (
	Development Environment = "development"
	Test        Environment = "test"
	Production  Environment = "production"
)

type Config struct {
	Environment              Environment
	DBDSN                    string
	ListenAddress            string
	StorageRoot              string
	SessionKey               string
	SessionTTL               time.Duration
	LoginAttempts            int
	LoginWindow              time.Duration
	MaxPromptBytes           int
	MaxImages                int
	MaxImageBytes            int64
	MaxUploadBytes           int64
	MaxImagePixels           uint64
	HistoryLimit             int
	WorkerLeaseDuration      time.Duration
	WorkerPollInterval       time.Duration
	ProviderHTTPTimeout      time.Duration
	ProviderMaxResponseBytes int64
	TestDisableWorker        bool
}

func Load() (Config, error) {
	return LoadFromLookup(os.LookupEnv)
}

func LoadFromLookup(lookup func(string) (string, bool)) (Config, error) {
	read := func(name string) string {
		value, _ := lookup(name)
		return strings.TrimSpace(value)
	}

	environment := Environment(read("CHORUS_ENV"))
	if environment == "" {
		environment = Development
	}
	if environment != Development && environment != Test && environment != Production {
		return Config{}, fmt.Errorf("CHORUS_ENV must be development, test, or production")
	}

	cfg := Config{
		Environment:   environment,
		DBDSN:         read("CHORUS_DSN"),
		ListenAddress: read("CHORUS_LISTEN_ADDRESS"),
		StorageRoot:   read("CHORUS_STORAGE_ROOT"),
		SessionKey:    read("CHORUS_SESSION_KEY"),
	}
	if environment != Production {
		if cfg.StorageRoot == "" {
			cfg.StorageRoot = "var/storage"
		}
		if cfg.SessionKey == "" {
			generated := make([]byte, 32)
			if _, err := rand.Read(generated); err != nil {
				return Config{}, fmt.Errorf("generate development session key")
			}
			cfg.SessionKey = base64.RawURLEncoding.EncodeToString(generated)
		}
	}
	if cfg.ListenAddress == "" {
		cfg.ListenAddress = "127.0.0.1:8080"
	}

	var missing []string
	if cfg.DBDSN == "" {
		missing = append(missing, "CHORUS_DSN")
	}
	if environment == Production {
		for name, value := range map[string]string{
			"CHORUS_SESSION_KEY":  cfg.SessionKey,
			"CHORUS_STORAGE_ROOT": cfg.StorageRoot,
		} {
			if value == "" {
				missing = append(missing, name)
			}
		}
		for _, name := range []string{"CHORUS_SESSION_TTL_MINUTES", "CHORUS_LOGIN_ATTEMPTS", "CHORUS_LOGIN_WINDOW_SECONDS", "CHORUS_MAX_PROMPT_BYTES", "CHORUS_MAX_IMAGES", "CHORUS_MAX_IMAGE_BYTES", "CHORUS_MAX_UPLOAD_BYTES", "CHORUS_MAX_IMAGE_PIXELS", "CHORUS_HISTORY_LIMIT", "CHORUS_WORKER_LEASE_SECONDS", "CHORUS_WORKER_POLL_MILLISECONDS", "CHORUS_PROVIDER_HTTP_TIMEOUT_SECONDS", "CHORUS_PROVIDER_MAX_RESPONSE_BYTES"} {
			if read(name) == "" {
				missing = append(missing, name)
			}
		}
	}
	if len(missing) > 0 {
		return Config{}, fmt.Errorf("missing required configuration: %s", strings.Join(missing, ", "))
	}
	var err error
	if cfg.SessionTTL, err = durationConfig(read("CHORUS_SESSION_TTL_MINUTES"), 480, time.Minute); err != nil {
		return Config{}, fmt.Errorf("CHORUS_SESSION_TTL_MINUTES is invalid")
	}
	if cfg.LoginWindow, err = durationConfig(read("CHORUS_LOGIN_WINDOW_SECONDS"), 60, time.Second); err != nil {
		return Config{}, fmt.Errorf("CHORUS_LOGIN_WINDOW_SECONDS is invalid")
	}
	if cfg.LoginAttempts, err = intConfig(read("CHORUS_LOGIN_ATTEMPTS"), 5); err != nil {
		return Config{}, fmt.Errorf("CHORUS_LOGIN_ATTEMPTS is invalid")
	}
	if cfg.MaxPromptBytes, err = intConfig(read("CHORUS_MAX_PROMPT_BYTES"), 8000); err != nil {
		return Config{}, fmt.Errorf("CHORUS_MAX_PROMPT_BYTES is invalid")
	}
	if cfg.MaxImages, err = intConfig(read("CHORUS_MAX_IMAGES"), 8); err != nil {
		return Config{}, fmt.Errorf("CHORUS_MAX_IMAGES is invalid")
	}
	maxImageBytes, err := intConfig(read("CHORUS_MAX_IMAGE_BYTES"), 10<<20)
	if err != nil {
		return Config{}, fmt.Errorf("CHORUS_MAX_IMAGE_BYTES is invalid")
	}
	cfg.MaxImageBytes = int64(maxImageBytes)
	maxUploadBytes, err := intConfig(read("CHORUS_MAX_UPLOAD_BYTES"), 32<<20)
	if err != nil {
		return Config{}, fmt.Errorf("CHORUS_MAX_UPLOAD_BYTES is invalid")
	}
	cfg.MaxUploadBytes = int64(maxUploadBytes)
	maxPixels, err := intConfig(read("CHORUS_MAX_IMAGE_PIXELS"), 40_000_000)
	if err != nil {
		return Config{}, fmt.Errorf("CHORUS_MAX_IMAGE_PIXELS is invalid")
	}
	cfg.MaxImagePixels = uint64(maxPixels)
	if cfg.HistoryLimit, err = intConfig(read("CHORUS_HISTORY_LIMIT"), 50); err != nil {
		return Config{}, fmt.Errorf("CHORUS_HISTORY_LIMIT is invalid")
	}
	if cfg.WorkerLeaseDuration, err = durationConfig(read("CHORUS_WORKER_LEASE_SECONDS"), 60, time.Second); err != nil {
		return Config{}, fmt.Errorf("CHORUS_WORKER_LEASE_SECONDS is invalid")
	}
	if cfg.WorkerPollInterval, err = durationConfig(read("CHORUS_WORKER_POLL_MILLISECONDS"), 250, time.Millisecond); err != nil {
		return Config{}, fmt.Errorf("CHORUS_WORKER_POLL_MILLISECONDS is invalid")
	}
	if cfg.ProviderHTTPTimeout, err = durationConfig(read("CHORUS_PROVIDER_HTTP_TIMEOUT_SECONDS"), 45, time.Second); err != nil {
		return Config{}, fmt.Errorf("CHORUS_PROVIDER_HTTP_TIMEOUT_SECONDS is invalid")
	}
	providerMaxResponseBytes, err := intConfig(read("CHORUS_PROVIDER_MAX_RESPONSE_BYTES"), 32<<20)
	if err != nil {
		return Config{}, fmt.Errorf("CHORUS_PROVIDER_MAX_RESPONSE_BYTES is invalid")
	}
	cfg.ProviderMaxResponseBytes = int64(providerMaxResponseBytes)
	if value := read("CHORUS_TEST_DISABLE_WORKER"); value != "" {
		if cfg.TestDisableWorker, err = strconv.ParseBool(value); err != nil {
			return Config{}, fmt.Errorf("CHORUS_TEST_DISABLE_WORKER is invalid")
		}
		if cfg.TestDisableWorker && environment != Test {
			return Config{}, fmt.Errorf("CHORUS_TEST_DISABLE_WORKER is only allowed in test")
		}
	}
	if cfg.MaxUploadBytes < cfg.MaxImageBytes || cfg.MaxImages > 32 || cfg.HistoryLimit > 200 {
		return Config{}, fmt.Errorf("portal limits are inconsistent")
	}
	if cfg.WorkerLeaseDuration <= cfg.ProviderHTTPTimeout+5*time.Second {
		return Config{}, fmt.Errorf("worker lease must exceed provider HTTP timeout by more than 5 seconds")
	}
	return cfg, nil
}

func (c Config) ValidateProduction() error {
	if c.Environment != Production {
		return nil
	}
	if c.DBDSN == "" || len(c.SessionKey) < 32 || c.StorageRoot == "" || c.SessionTTL <= 0 || c.MaxImageBytes <= 0 || c.MaxUploadBytes < c.MaxImageBytes || c.WorkerLeaseDuration <= c.ProviderHTTPTimeout+5*time.Second || c.ProviderMaxResponseBytes <= 0 {
		return errors.New("production configuration is incomplete")
	}
	return nil
}

func intConfig(value string, fallback int) (int, error) {
	if value == "" {
		return fallback, nil
	}
	parsed, err := strconv.Atoi(value)
	if err != nil || parsed <= 0 {
		return 0, errors.New("invalid positive integer")
	}
	return parsed, nil
}
func durationConfig(value string, fallback int, unit time.Duration) (time.Duration, error) {
	parsed, err := intConfig(value, fallback)
	if err != nil {
		return 0, err
	}
	return time.Duration(parsed) * unit, nil
}