/*
Copyright 2017-2022 CAcert Inc.
SPDX-License-Identifier: Apache-2.0

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package main

import (
	"encoding/base64"
	"fmt"
	"io/ioutil"
	"time"

	"gopkg.in/yaml.v2"
)

const (
	cookieSecretMinLen    = 32
	csrfKeyLength         = 32
	httpIdleTimeout       = time.Minute
	httpReadHeaderTimeout = 5 * time.Second
	httpReadTimeout       = 5 * time.Second
	httpWriteTimeout      = 10 * time.Second
)

type mailConfig struct {
	SMTPHost                  string `yaml:"smtp_host"`
	SMTPPort                  int    `yaml:"smtp_port"`
	NotificationSenderAddress string `yaml:"notification_sender_address"`
	NoticeMailAddress         string `yaml:"notice_mail_address"`
	VoteNoticeMailAddress     string `yaml:"vote_notice_mail_address"`
	BaseURL                   string `yaml:"base_url"`
}

type httpTimeoutConfig struct {
	Idle       time.Duration `yaml:"idle,omitempty"`
	Read       time.Duration `yaml:"read,omitempty"`
	ReadHeader time.Duration `yaml:"read_header,omitempty"`
	Write      time.Duration `yaml:"write,omitempty"`
}

type Config struct {
	DatabaseFile         string             `yaml:"database_file"`
	ClientCACertificates string             `yaml:"client_ca_certificates"`
	ServerCert           string             `yaml:"server_certificate"`
	ServerKey            string             `yaml:"server_key"`
	CookieSecretStr      string             `yaml:"cookie_secret"`
	CsrfKeyStr           string             `yaml:"csrf_key"`
	HTTPAddress          string             `yaml:"http_address,omitempty"`
	HTTPSAddress         string             `yaml:"https_address,omitempty"`
	MailConfig           *mailConfig        `yaml:"mail_config"`
	Timeouts             *httpTimeoutConfig `yaml:"timeouts,omitempty"`
	CookieSecret         []byte             `yaml:"-"`
	CsrfKey              []byte             `yaml:"-"`
}

func parseConfig(configFile string) (*Config, error) {
	source, err := ioutil.ReadFile(configFile)
	if err != nil {
		return nil, fmt.Errorf("could not read configuration file %s: %w", configFile, err)
	}

	config := &Config{
		HTTPAddress:  "127.0.0.1:8000",
		HTTPSAddress: "127.0.0.1:8443",
		Timeouts: &httpTimeoutConfig{
			Idle:       httpIdleTimeout,
			ReadHeader: httpReadHeaderTimeout,
			Read:       httpReadTimeout,
			Write:      httpWriteTimeout,
		},
	}

	if err := yaml.Unmarshal(source, config); err != nil {
		return nil, fmt.Errorf("could not parse configuration: %w", err)
	}

	if config.CookieSecret, err = base64.StdEncoding.DecodeString(config.CookieSecretStr); err != nil {
		return nil, fmt.Errorf("could not decode cookie secret: %w", err)
	}

	if len(config.CookieSecret) < cookieSecretMinLen {
		return nil, fmt.Errorf("cookie secret is less than the minimum require %d bytes long", cookieSecretMinLen)
	}

	if config.CsrfKey, err = base64.StdEncoding.DecodeString(config.CsrfKeyStr); err != nil {
		return nil, fmt.Errorf("could not decode CSRF key: %w", err)
	}

	if len(config.CsrfKey) != csrfKeyLength {
		return nil, fmt.Errorf(
			"CSRF key must be exactly %d bytes long but is %d bytes long", csrfKeyLength, len(config.CsrfKey),
		)
	}

	return config, nil
}