package emulator

import (
	"bufio"
	"fmt"
	"os"
)

type commandHistory struct {
	file    *os.File
	history []string
}

// Create new commandHistory struct.
// Opens specified file and reads its contents into a string array
func newCommandHistory(filepath string) (commandHistory, error) {
	f, err := os.OpenFile(filepath, os.O_RDWR|os.O_CREATE|os.O_APPEND, 0644)
	if err != nil {
		return commandHistory{}, fmt.Errorf("could not open file")
	}
	ch := commandHistory{file: f, history: []string{}}
	err = ch.readFromFile()
	if err != nil {
		return commandHistory{}, fmt.Errorf("error reading from file")
	}
	return ch, nil
}

func (ch *commandHistory) readFromFile() error {
	scanner := bufio.NewScanner(ch.file)
	for scanner.Scan() {
		ch.history = append(ch.history, scanner.Text())
	}
	return scanner.Err()
}

// Update both history and file with new input
func (ch *commandHistory) updateHistory(in string, limit int) error {
	if len(ch.history) == 0 || in != ch.history[len(ch.history)-1] {
		ch.history = append(ch.history, in)
		// Truncate ch.history to only the most recent commands within size limit
		if len(ch.history) > limit {
			diff := len(ch.history) - limit
			ch.history = ch.history[diff:]
		}
		// Write new line to file
		_, err := ch.file.WriteString(in + "\n")
		if err != nil {
			return err
		}
	}
	return nil
}

func (ch *commandHistory) close() {
	ch.file.Close()
}