/*
Copyright 2022-2023 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.Minute
	defaultResponseAnnounceTimeout = 30 * time.Second
	defaultResponseDataTimeout     = 2 * time.Second
	defaultFilesDirectory          = "public"
	defaultCommandChannelCapacity  = 100
	defaultDatabaseConnMaxLiveTime = 3 * time.Minute
	defaultDatabaseMaxOpenConns    = 10
	defaultDatabaseMaxIdleConns    = 10
)

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 Database struct {
	DSN             string        `yaml:"dsn"`
	ConnMaxLiveTime time.Duration `yaml:"conn-max-live-time"`
	MaxOpenConns    int           `yaml:"max-open-conns"`
	MaxIdleConns    int           `yaml:"max-idle-conns"`
}

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"`
	PublicCRLDirectory         string        `yaml:"public-crl-directory"`
	PublicCertificateDirectory string        `yaml:"public-certificate-directory"`
	CommandChannelCapacity     int           `yaml:"command-channel-capacity"`
	Database                   Database      `yaml:"database"`
}

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"`
		PublicCRLDirectory         string        `yaml:"public-crl-directory"`
		PublicCertificateDirectory string        `yaml:"public-certificate-directory"`
		CommandChannelCapacity     int           `yaml:"command-channel-capacity"`
		Database                   Database      `yaml:"database"`
	}{}

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

	if err := checkSerialConfig(&data.Serial); err != nil {
		return err
	}

	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.PublicCRLDirectory == "" {
		data.PublicCRLDirectory = defaultFilesDirectory
	}

	c.PublicCRLDirectory = data.PublicCRLDirectory

	if data.PublicCertificateDirectory == "" {
		data.PublicCertificateDirectory = defaultFilesDirectory
	}

	if data.CommandChannelCapacity == 0 {
		data.CommandChannelCapacity = defaultCommandChannelCapacity
	}

	c.CommandChannelCapacity = data.CommandChannelCapacity

	c.PublicCertificateDirectory = data.PublicCRLDirectory

	if err := checkDatabaseConfig(&data.Database); err != nil {
		return err
	}

	c.Database = data.Database

	c.Database = data.Database

	return nil
}

func checkDatabaseConfig(d *Database) error {
	if d.DSN == "" {
		return SettingsError{"you must specify a database 'dsn'"}
	}

	if d.ConnMaxLiveTime == 0 {
		d.ConnMaxLiveTime = defaultDatabaseConnMaxLiveTime
	}

	if d.MaxOpenConns == 0 {
		d.MaxOpenConns = defaultDatabaseMaxOpenConns
	}

	if d.MaxIdleConns == 0 {
		d.MaxIdleConns = defaultDatabaseMaxIdleConns
	}

	return nil
}

func checkSerialConfig(s *Serial) error {
	if s.Device == "" {
		return SettingsError{"you must specify a serial 'device'"}
	}

	if s.Baud == 0 {
		s.Baud = 115200
	}

	if s.Timeout == 0 {
		s.Timeout = defaultSerialTimeout
	}

	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
}