/*
	httpprocwatchd provides HTTP interface to a list of process' statuses
	formatted as JSON.
	Copyright (c) 2021 Alexander "Arav" Andreev <me@arav.top>

	This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <https://www.gnu.org/licenses/>.
*/

package main

import (
	"encoding/json"
	"io/ioutil"
)

// Configuration holds a list of process names to be tracked and a listen address.
type Configuration struct {
	ListenAddress string   `json:"listen_address"`
	Processes     []string `json:"processes"`
}

// LoadConfiguration loads configuration from a JSON file.
func LoadConfiguration(path string) (conf *Configuration, err error) {
	conf = &Configuration{}

	file, err := ioutil.ReadFile(path)
	if err != nil {
		return nil, err
	}

	if err := json.Unmarshal(file, conf); err != nil {
		return nil, err
	}

	return conf, nil
}

// StoreConfiguration writes Configuration into a JSON file.
func StoreConfiguration(path string, conf *Configuration) (err error) {
	config, err := json.Marshal(*conf)
	if err != nil {
		return err
	}

	err = ioutil.WriteFile(path, config, 0644)
	if err != nil {
		return err
	}

	return nil
}

// AddProcessToList appends a new given process into a configuration file.
func AddProcessToList(process string, conf *Configuration, configPath string) error {
	for _, v := range conf.Processes {
		if v == process {
			return ErrIsOnList
		}
	}

	conf.Processes = append(conf.Processes, process)
	if err := StoreConfiguration(configPath, conf); err != nil {
		return err
	}

	return nil
}

// RemoveProcessFromList removes a given process from a configuration file.
func RemoveProcessFromList(process string, conf *Configuration, configPath string) error {
	for k, v := range conf.Processes {
		if v == process {
			newlist := make([]string, len(conf.Processes)-1)
			newlist = append(conf.Processes[:k], conf.Processes[k+1:]...)
			conf.Processes = newlist
			if err := StoreConfiguration(configPath, conf); err != nil {
				return err
			}

			return nil
		}
	}

	return ErrNotFound
}