package main

import (
	"bufio"
	"io/ioutil"
	"log"
	"os"
	"strconv"
	"strings"
)

// Configuration holds a list of process names to be tracked and a listen address.
type Configuration struct {
	ListenAddress  string
	IndentedOutput bool
	Processes      []string
}

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

	file, err := os.Open(path)
	if err != nil {
		return nil, err
	}
	defer file.Close()

	s := bufio.NewScanner(file)
	s.Split(bufio.ScanLines)

	for s.Scan() {
		kv := strings.Split(s.Text(), " = ")
		switch kv[0] {
		case "listen_address":
			conf.ListenAddress = kv[1]
		case "indented_output":
			v, err := strconv.ParseBool(kv[1])
			if err != nil {
				log.Printf("WARN: could not parse \"indented_output\", valid values are true or false. Defaulted to false.\n")
			}
			conf.IndentedOutput = v
		case "processes":
			if kv[1] != "" {
				conf.Processes = append(conf.Processes, strings.Split(kv[1], " ")...)
			} else {
				log.Printf("WARN: \"processes\" list is empty.\n")
			}
		}
	}

	return conf, nil
}

// StoreConfiguration writes Configuration into a file.
func (conf *Configuration) StoreConfiguration(path string) (err error) {
	var config strings.Builder

	config.WriteString("listen_address = ")
	config.WriteString(conf.ListenAddress)
	config.WriteByte('\n')
	config.WriteString("indented_output = ")
	config.WriteString(strconv.FormatBool(conf.IndentedOutput))
	config.WriteByte('\n')
	config.WriteString("processes = ")
	config.WriteString(strings.Join(conf.Processes, " "))

	if err := ioutil.WriteFile(path, []byte(config.String()), 0644); err != nil {
		return err
	}

	return nil
}

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

	conf.Processes = append(conf.Processes, process)
	return nil
}

// RemoveProcess removes a given process from a configuration file.
func (conf *Configuration) RemoveProcess(process string, 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
			return nil
		}
	}

	return ErrNotFound
}