package config

import (
	"fmt"
	"os"
	"slices"
	"strconv"
)

const (
	StorageDriverLocal = "local"
	StorageDriverS3    = "s3"

	DefaultStorageDriver = StorageDriverLocal
	DefaultS3Region      = "us-east-1"
	DefaultS3PathStyle   = "false"
	DefaultS3TLS         = "true"
	EnvStorageDriver     = "STORAGE_DRIVER"
	envS3Bucket          = "S3_BUCKET"
	envS3Region          = "S3_REGION"
	envS3Endpoint        = "S3_ENDPOINT"
	envS3AccessKeyID     = "S3_ACCESS_KEY_ID"
	envS3SecretKey       = "S3_SECRET_ACCESS_KEY"
	envS3KeyPrefix       = "S3_KEY_PREFIX"
	envS3PathStyle       = "S3_PATH_STYLE"
	envS3TLS             = "S3_TLS"
)

var s3RequiredEnvVars = []string{envS3Bucket}

type S3Settings struct {
	Bucket          string
	Region          string
	Endpoint        string
	AccessKeyID     string
	SecretAccessKey string
	KeyPrefix       string
	PathStyle       bool
	TLS             bool
}

type StorageSettings struct {
	Driver string
	S3     S3Settings
}

func StorageRequiredEnvVars(driver string) []string {
	if driver == StorageDriverS3 {
		return slices.Clone(s3RequiredEnvVars)
	}
	return nil
}

func storageSettingsFromEnv() (StorageSettings, error) {
	driver := envOrDefault(EnvStorageDriver, DefaultStorageDriver)
	switch driver {
	case StorageDriverLocal:
		return StorageSettings{Driver: driver}, nil
	case StorageDriverS3:
		s3, err := s3SettingsFromEnv()
		if err != nil {
			return StorageSettings{}, err
		}
		return StorageSettings{Driver: driver, S3: s3}, nil
	default:
		return StorageSettings{}, fmt.Errorf("unsupported storage driver %q", driver)
	}
}

func s3SettingsFromEnv() (S3Settings, error) {
	if err := MissingEnvVarError(s3RequiredEnvVars, nonEmptyEnvLookup); err != nil {
		return S3Settings{}, err
	}
	accessKeyID := os.Getenv(envS3AccessKeyID)
	secretKey := os.Getenv(envS3SecretKey)
	if accessKeyID != "" && secretKey == "" {
		return S3Settings{}, fmt.Errorf("Environment variable %s is not set (it is required when %s is set)", envS3SecretKey, envS3AccessKeyID)
	}
	if secretKey != "" && accessKeyID == "" {
		return S3Settings{}, fmt.Errorf("Environment variable %s is not set (it is required when %s is set)", envS3AccessKeyID, envS3SecretKey)
	}
	pathStyle, err := boolEnv(envS3PathStyle, DefaultS3PathStyle)
	if err != nil {
		return S3Settings{}, err
	}
	tls, err := boolEnv(envS3TLS, DefaultS3TLS)
	if err != nil {
		return S3Settings{}, err
	}
	return S3Settings{
		Bucket:          os.Getenv(envS3Bucket),
		Region:          envOrDefault(envS3Region, DefaultS3Region),
		Endpoint:        os.Getenv(envS3Endpoint),
		AccessKeyID:     accessKeyID,
		SecretAccessKey: secretKey,
		KeyPrefix:       os.Getenv(envS3KeyPrefix),
		PathStyle:       pathStyle,
		TLS:             tls,
	}, nil
}

func nonEmptyEnvLookup(name string) (string, bool) {
	value := os.Getenv(name)
	return value, value != ""
}

func boolEnv(name string, fallback string) (bool, error) {
	raw := envOrDefault(name, fallback)
	value, err := strconv.ParseBool(raw)
	if err != nil {
		return false, fmt.Errorf("%s must be true or false, got %q", name, raw)
	}
	return value, nil
}