// Copyright 2022 - Offen Authors <hioffen@posteo.de>
// SPDX-License-Identifier: MPL-2.0

package main

import (
	"crypto/x509"
	"encoding/pem"
	"fmt"
	"os"
	"regexp"
	"strconv"
	"time"
)

// Config holds all configuration values that are expected to be set
// by users.
type Config struct {
	AwsS3BucketName               string          `split_words:"true"`
	AwsS3Path                     string          `split_words:"true"`
	AwsEndpoint                   string          `split_words:"true" default:"s3.amazonaws.com"`
	AwsEndpointProto              string          `split_words:"true" default:"https"`
	AwsEndpointInsecure           bool            `split_words:"true"`
	AwsEndpointCACert             CertDecoder     `envconfig:"AWS_ENDPOINT_CA_CERT"`
	AwsStorageClass               string          `split_words:"true"`
	AwsAccessKeyID                string          `envconfig:"AWS_ACCESS_KEY_ID"`
	AwsAccessKeyIDFile            string          `envconfig:"AWS_ACCESS_KEY_ID_FILE"`
	AwsSecretAccessKey            string          `split_words:"true"`
	AwsSecretAccessKeyFile        string          `split_words:"true"`
	AwsIamRoleEndpoint            string          `split_words:"true"`
	AwsPartSize                   int64           `split_words:"true"`
	BackupCompression             CompressionType `split_words:"true" default:"gz"`
	BackupSources                 string          `split_words:"true" default:"/backup"`
	BackupFilename                string          `split_words:"true" default:"backup-%Y-%m-%dT%H-%M-%S.{{ .Extension }}"`
	BackupFilenameExpand          bool            `split_words:"true"`
	BackupLatestSymlink           string          `split_words:"true"`
	BackupArchive                 string          `split_words:"true" default:"/archive"`
	BackupRetentionDays           int32           `split_words:"true" default:"-1"`
	BackupPruningLeeway           time.Duration   `split_words:"true" default:"1m"`
	BackupPruningPrefix           string          `split_words:"true"`
	BackupStopContainerLabel      string          `split_words:"true" default:"true"`
	BackupFromSnapshot            bool            `split_words:"true"`
	BackupExcludeRegexp           RegexpDecoder   `split_words:"true"`
	GpgPassphrase                 string          `split_words:"true"`
	NotificationURLs              []string        `envconfig:"NOTIFICATION_URLS"`
	NotificationLevel             string          `split_words:"true" default:"error"`
	EmailNotificationRecipient    string          `split_words:"true"`
	EmailNotificationSender       string          `split_words:"true" default:"noreply@nohost"`
	EmailSMTPHost                 string          `envconfig:"EMAIL_SMTP_HOST"`
	EmailSMTPPort                 int             `envconfig:"EMAIL_SMTP_PORT" default:"587"`
	EmailSMTPUsername             string          `envconfig:"EMAIL_SMTP_USERNAME"`
	EmailSMTPPassword             string          `envconfig:"EMAIL_SMTP_PASSWORD"`
	WebdavUrl                     string          `split_words:"true"`
	WebdavUrlInsecure             bool            `split_words:"true"`
	WebdavPath                    string          `split_words:"true" default:"/"`
	WebdavUsername                string          `split_words:"true"`
	WebdavPassword                string          `split_words:"true"`
	SSHHostName                   string          `split_words:"true"`
	SSHPort                       string          `split_words:"true" default:"22"`
	SSHUser                       string          `split_words:"true"`
	SSHPassword                   string          `split_words:"true"`
	SSHIdentityFile               string          `split_words:"true" default:"/root/.ssh/id_rsa"`
	SSHIdentityPassphrase         string          `split_words:"true"`
	SSHRemotePath                 string          `split_words:"true"`
	ExecLabel                     string          `split_words:"true"`
	ExecForwardOutput             bool            `split_words:"true"`
	LockTimeout                   time.Duration   `split_words:"true" default:"60m"`
	AzureStorageAccountName       string          `split_words:"true"`
	AzureStoragePrimaryAccountKey string          `split_words:"true"`
	AzureStorageContainerName     string          `split_words:"true"`
	AzureStoragePath              string          `split_words:"true"`
	AzureStorageEndpoint          string          `split_words:"true" default:"https://{{ .AccountName }}.blob.core.windows.net/"`
	DropboxEndpoint               string          `split_words:"true" default:"https://api.dropbox.com/"`
	DropboxOAuth2Endpoint         string          `envconfig:"DROPBOX_OAUTH2_ENDPOINT" default:"https://api.dropbox.com/"`
	DropboxRefreshToken           string          `split_words:"true"`
	DropboxAppKey                 string          `split_words:"true"`
	DropboxAppSecret              string          `split_words:"true"`
	DropboxRemotePath             string          `split_words:"true"`
	DropboxConcurrencyLevel       NaturalNumber   `split_words:"true" default:"6"`
}

func (c *Config) resolveSecret(envVar string, secretPath string) (string, error) {
	if secretPath == "" {
		return envVar, nil
	}
	data, err := os.ReadFile(secretPath)
	if err != nil {
		return "", fmt.Errorf("resolveSecret: error reading secret path: %w", err)
	}
	return string(data), nil
}

type CompressionType string

func (c *CompressionType) Decode(v string) error {
	switch v {
	case "gz", "zst":
		*c = CompressionType(v)
		return nil
	default:
		return fmt.Errorf("config: error decoding compression type %s", v)
	}
}

func (c *CompressionType) String() string {
	return string(*c)
}

type CertDecoder struct {
	Cert *x509.Certificate
}

func (c *CertDecoder) Decode(v string) error {
	if v == "" {
		return nil
	}
	content, err := os.ReadFile(v)
	if err != nil {
		content = []byte(v)
	}
	block, _ := pem.Decode(content)
	cert, err := x509.ParseCertificate(block.Bytes)
	if err != nil {
		return fmt.Errorf("config: error parsing certificate: %w", err)
	}
	*c = CertDecoder{Cert: cert}
	return nil
}

type RegexpDecoder struct {
	Re *regexp.Regexp
}

func (r *RegexpDecoder) Decode(v string) error {
	if v == "" {
		return nil
	}
	re, err := regexp.Compile(v)
	if err != nil {
		return fmt.Errorf("config: error compiling given regexp `%s`: %w", v, err)
	}
	*r = RegexpDecoder{Re: re}
	return nil
}

type NaturalNumber int

func (n *NaturalNumber) Decode(v string) error {
	asInt, err := strconv.Atoi(v)
	if err != nil {
		return fmt.Errorf("config: error converting %s to int", v)
	}
	if asInt <= 0 {
		return fmt.Errorf("config: expected a natural number, got %d", asInt)
	}
	*n = NaturalNumber(asInt)
	return nil
}

func (n *NaturalNumber) Int() int {
	return int(*n)
}