package main

import (
	"flag"
	"fmt"
	"io"
	"os"
	"os/exec"
	"strconv"
	"text/tabwriter"
)

import (
	"mailq-inspector/parser"
)

var settings = make(map[string]string)

func main() {
	parseArguments()
	if settings["interactive"] == "false" {
		showQueue()
	}
	if settings["interactive"] == "true" {
		interactiveShell()
	}
	fmt.Printf("I am done.\n")
}

func parseArguments() {
	mailqCommandPtr := flag.String("mailqCommand", "mailq", "Command to use for getting mailq output")
	mailqCommandArgsPtr := flag.String("mailqCommandArgs", "", "Optional arguments to pass to mailqCommand")
	interactivePtr := flag.Bool("interactive", false, "Set to true for shell mode")
	flag.Parse()
	settings["mailqCommand"] = *mailqCommandPtr
	settings["mailqCommandArgs"] = *mailqCommandArgsPtr
	settings["interactive"] = strconv.FormatBool(*interactivePtr)
}

func interactiveShell() {

}

func showQueue() {
	entries, err := fetchQueueEntries()
	if err != nil {
		fmt.Printf("Could not fetch queue entries: %s\n", err.Error())
		os.Exit(1)
	}
	pagerReader, pagerWriter := io.Pipe()
	pagerDone := make(chan bool)
	go launchPager(pagerReader, pagerDone)
	printQueueEntries(entries, pagerWriter)
	pagerWriter.Close()
	// Wait for pager to be closed before continuing the main program
	<-pagerDone
}

func fetchQueueEntries() ([]parser.QEntry, error) {
	var entries []parser.QEntry
	var err error
	if settings["mailqCommandArgs"] == "" {
		entries, err = readFromCmd(exec.Command(settings["mailqCommand"]))
	} else {
		entries, err = readFromCmd(exec.Command(settings["mailqCommand"], settings["mailqCommandArgs"]))
	}
	return entries, err
}

func printQueueEntries(entries []parser.QEntry, writer io.Writer) {
	tabWriter := tabwriter.NewWriter(writer, 0, 2, 1, ' ', tabwriter.TabIndent)
	fmt.Fprintf(tabWriter, "%s\t%s\t%s\t%s\t%s\t%s\n", "Date", "Id", "Size", "Sender", "#", "First Recipient")
	for _, entry := range entries {
		_, writeError := fmt.Fprintf(tabWriter, "%s\t%s\t%d\t%s\t{%d}\t%s\n", entry.Date, entry.Id, entry.Size, entry.Sender, len(entry.Recipients), entry.Recipients[0])
		if writeError != nil {
			// A writeError is expected once the reader was closed
			// This happens when the pager application got terminated
			fmt.Printf("Error writing!: %s\n", writeError.Error())
			break
		}
	}
	tabWriter.Flush()
}

func launchPager(reader *io.PipeReader, pagerDone chan<- bool) {
	cmd := exec.Command("less")
	cmd.Stdin = reader
	cmd.Stdout = os.Stdout
	if err := cmd.Start(); err != nil {
		fmt.Printf("Error launching pager: %s\n", err.Error())
	}
	if err := cmd.Wait(); err != nil {
		fmt.Printf("Error terminating pager: %s\n", err.Error())
	} else {
		reader.Close()
		pagerDone <- true
	}
}

func readFromCmd(cmd *exec.Cmd) ([]parser.QEntry, error) {
	stdout, err := cmd.StdoutPipe()
	if err != nil {
		return nil, err
	}
	if err := cmd.Start(); err != nil {
		return nil, err
	}
	result, resultError := parser.ParseMailQ(stdout)
	if err := cmd.Wait(); err != nil {
		return nil, err
	}
	return result, resultError
}