/*
Copyright 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 config

import (
	"fmt"
	"io"
	"os"
	"time"

	"gopkg.in/yaml.v3"
)

const (
	defaultSerialTimeout           = 5 * time.Second
	defaultHealthInterval          = 30 * time.Second
	defaultHealthStart             = 2 * time.Second
	defaultFetchCRLInterval        = 5 * time.Minute
	defaultFetchCRLStart           = 5 * time.Second
	defaultResponseAnnounceTimeout = 30 * time.Second
	defaultResponseDataTimeout     = 2 * time.Second
	defaultCRLDirectory            = "crls"
)

type SettingsError struct {
	msg string
}

func (se SettingsError) Error() string {
	return fmt.Sprintf("invalid Settings %s", se.msg)
}

type Serial struct {
	Device  string        `yaml:"device"`
	Baud    int           `yaml:"baud"`
	Timeout time.Duration `yaml:"timeout"`
}

type ClientConfig struct {
	Serial                  Serial        `yaml:"serial"`
	HealthInterval          time.Duration `yaml:"health-interval"`
	HealthStart             time.Duration `yaml:"health-start"`
	FetchCRLStart           time.Duration `yaml:"fetch-crl-start"`
	FetchCRLInterval        time.Duration `yaml:"fetch-crl-interval"`
	ResponseAnnounceTimeout time.Duration `yaml:"response-announce-timeout"`
	ResponseDataTimeout     time.Duration `yaml:"response-data-timeout"`
	CRLDirectory            string        `yaml:"crl-directory"`
}

func (c *ClientConfig) UnmarshalYAML(n *yaml.Node) error {
	data := struct {
		Serial                  Serial        `yaml:"serial"`
		HealthInterval          time.Duration `yaml:"health-interval"`
		HealthStart             time.Duration `yaml:"health-start"`
		FetchCRLStart           time.Duration `yaml:"fetch-crl-start"`
		FetchCRLInterval        time.Duration `yaml:"fetch-crl-interval"`
		ResponseAnnounceTimeout time.Duration `yaml:"response-announce-timeout"`
		ResponseDataTimeout     time.Duration `yaml:"response-data-timeout"`
		CRLDirectory            string        `yaml:"crl-directory"`
	}{}

	err := n.Decode(&data)
	if err != nil {
		return fmt.Errorf("could not decode YAML: %w", err)
	}

	if data.Serial.Device == "" {
		return SettingsError{"you must specify a serial 'device'"}
	}

	if data.Serial.Baud == 0 {
		data.Serial.Baud = 115200
	}

	if data.Serial.Timeout == 0 {
		data.Serial.Timeout = defaultSerialTimeout
	}

	c.Serial = data.Serial

	if data.HealthInterval == 0 {
		data.HealthInterval = defaultHealthInterval
	}

	c.HealthInterval = data.HealthInterval

	if data.HealthStart == 0 {
		data.HealthStart = defaultHealthStart
	}

	c.HealthStart = data.HealthStart

	if data.FetchCRLInterval == 0 {
		data.FetchCRLInterval = defaultFetchCRLInterval
	}

	c.FetchCRLInterval = data.FetchCRLInterval

	if data.FetchCRLStart == 0 {
		data.FetchCRLStart = defaultFetchCRLStart
	}

	c.FetchCRLStart = data.FetchCRLStart

	if data.ResponseAnnounceTimeout == 0 {
		data.ResponseAnnounceTimeout = defaultResponseAnnounceTimeout
	}

	c.ResponseAnnounceTimeout = data.ResponseAnnounceTimeout

	if data.ResponseDataTimeout == 0 {
		data.ResponseDataTimeout = defaultResponseDataTimeout
	}

	c.ResponseDataTimeout = data.ResponseDataTimeout

	if data.CRLDirectory == "" {
		data.CRLDirectory = defaultCRLDirectory
	}

	c.CRLDirectory = data.CRLDirectory

	return nil
}

func New(clientConfigFile string) (*ClientConfig, error) {
	configFile, err := os.Open(clientConfigFile)
	if err != nil {
		return nil, fmt.Errorf("could not open signer client configuration file %s: %w", clientConfigFile, err)
	}

	defer func() { _ = configFile.Close() }()

	clientConfig, err := LoadConfiguration(configFile)
	if err != nil {
		return nil, fmt.Errorf("could not load client configuration from %s: %w", clientConfigFile, err)
	}

	return clientConfig, nil
}

func LoadConfiguration(r io.Reader) (*ClientConfig, error) {
	var config *ClientConfig

	decoder := yaml.NewDecoder(r)
	err := decoder.Decode(&config)

	if err != nil {
		return nil, fmt.Errorf("could not parse YAML configuration: %w", err)
	}

	return config, nil
}