package main

import (
  "bufio"
  "flag"
  "fmt"

  "io"
  "os"

  "strings"

  "pragprog.com/rggo/interacting/todo"
)

// Default file name
var todoFileName = ".todo.json"

func main() {
  // Parsing command line flags
  add := flag.Bool("add", false, "Add task to the ToDo list")
  list := flag.Bool("list", false, "List all tasks")
  complete := flag.Int("complete", 0, "Item to be completed")

  flag.Usage = func() {
    fmt.Fprintf(flag.CommandLine.Output(),
      "%s tool. Developed for The Pragmatic Bookshelf\n", os.Args[0])
    fmt.Fprintf(flag.CommandLine.Output(), "Copyright 2020\n")
    fmt.Fprintln(flag.CommandLine.Output(), "Usage information:")
    flag.PrintDefaults()
  }

  flag.Parse()

  // Check if the user defined the ENV VAR for a custom file name
  if os.Getenv("TODO_FILENAME") != "" {
    todoFileName = os.Getenv("TODO_FILENAME")
  }

  // Define an items list
  l := &todo.List{}

  // Use the Get method to read to do items from file
  if err := l.Get(todoFileName); err != nil {
    fmt.Fprintln(os.Stderr, err)
    os.Exit(1)
  }

  // Decide what to do based on the provided flags
  switch {
  case *list:
    // List current to do items
    fmt.Print(l)
  case *complete > 0:
    // Complete the given item
    if err := l.Complete(*complete); err != nil {
      fmt.Fprintln(os.Stderr, err)
      os.Exit(1)
    }

    // Save the new list
    if err := l.Save(todoFileName); err != nil {
      fmt.Fprintln(os.Stderr, err)
      os.Exit(1)
    }
  case *add:
    // When any arguments (excluding flags) are provided, they will be
    // used as the new task
    t, err := getTask(os.Stdin, flag.Args()...)
    if err != nil {
      fmt.Fprintln(os.Stderr, err)
      os.Exit(1)
    }
    l.Add(t)

    // Save the new list
    if err := l.Save(todoFileName); err != nil {
      fmt.Fprintln(os.Stderr, err)
      os.Exit(1)
    }
  default:
    // Invalid flag provided
    flag.Usage()
    os.Exit(1)
  }
}

// getTask function decides where to get the description for a new
// task from: arguments or STDIN
func getTask(r io.Reader, args ...string) (string, error) {
  if len(args) > 0 {
    return strings.Join(args, " "), nil
  }

  s := bufio.NewScanner(r)
  s.Scan()
  if err := s.Err(); err != nil {
    return "", err
  }

  if len(s.Text()) == 0 {
    return "", fmt.Errorf("Task cannot be blank")
  }

  return s.Text(), nil
}