package parser

import (
	"bufio"
	"errors"
	"fmt"
    "io"
	"regexp"
	"strconv"
	"strings"
	"time"
)

type QEntry struct {
	id         string
	status     string
	date       time.Time
	size       int
	sender     string
	recipients []string
	reason     string
}

func (m QEntry) String() string {
	return fmt.Sprintf("ID: %s, Status: %s, Size: %d bytes, Sender: %s, Recipients: %d", m.id, m.status, m.size, m.sender, len(m.recipients))
}

func ParseMailQ(dataSource io.Reader) ([]QEntry, error) {
	const dateFormat = "2006 Mon Jan _2 15:04:05"
	var messageIdStart = regexp.MustCompile("^[0-9A-Za-z]+[*!]? ")
	scanner := bufio.NewScanner(dataSource)
	scanner.Scan()
	line := scanner.Text()
	if strings.HasPrefix(line, "Mail queue is empty") {
		// If mail queue is empty, there is nothing to do
		return nil, errors.New(line)
	} else if strings.HasPrefix(line, "-Queue ID-") == false {
		// Abort if input does not look like output from mailq(1)
		return nil, errors.New("Sorry, this does not look like output from mailq(1).")
	}
	var currentMail QEntry
	var queueEntries []QEntry

	for scanner.Scan() {
		// Read input line by line
		line := scanner.Text()
		fields := strings.Fields(line)
		if strings.HasPrefix(line, "--") {
			// Handle the summary line at the end of mailq output
			break
		} else if messageIdStart.MatchString(line) {
			// Handle line starting next mail in queue
			messageId := fields[0]
			if strings.HasSuffix(messageId, "*") {
				currentMail.status = "active"
			} else if strings.HasSuffix(messageId, "!") {
				currentMail.status = "hold"
			} else {
				currentMail.status = "deferred"
			}
			dateString := strconv.Itoa(time.Now().Year()) + " " + strings.Join(fields[2:6], " ")
			mailDate, _ := time.Parse(dateFormat, dateString)
			currentMail.id = strings.TrimRight(messageId, "*!")
			currentMail.size, _ = strconv.Atoi(fields[1])
			currentMail.date = mailDate
			currentMail.sender = fields[6]
			continue
		} else if strings.HasPrefix(line, "(") && strings.HasSuffix(line, ")") {
			// Handle reason for deferred status (if deferred at all, may be missing)
			currentMail.reason = strings.Trim(strings.TrimSpace(line), "()")
			continue
		} else if len(fields) == 1 {
			// Handle line with one of the mail recipients
			currentMail.recipients = append(currentMail.recipients, fields[0])
			continue
		} else if len(fields) == 0 {
			// If the next line is empty, make sure to push current mail to list
			// and create a new struct for the next mail to process
			queueEntries = append(queueEntries, currentMail)
			currentMail = QEntry{}
		}
	}
	if scanner.Err() != nil {
		// If the scanner failed, let our caller know.
		return nil, errors.New("Something went wrong with reading from stdin. Sorry!")
	}
	return queueEntries, nil
}