package main

import (
	"encoding/gob"
	"errors"
	"flag"
	"fmt"
	"os"
	"strings"
	"time"

	ws "git.spacehb.net/ws.git"
)

var (
	// Stack of active tasks
	Tags []ws.Tag
	// Active tasks
	Tasks []ws.Task
	// Completed tasks
	TasksDone []ws.TaskDone
	// Persistent storage for Tasks
)

func AddTask(tagName string, taskText string) {
	if taskText == "" {
		fmt.Println("Task text is required.")
		os.Exit(1)
	}

	if tagName == "" {
		Tasks = append(Tasks, ws.Task{Text: taskText})
		return
	}

	tag := ws.Tag(tagName)

	// Validate tag
	found := false
	for _, v := range Tags {
		if tag == v {
			found = true
			break
		}
	}
	if !found {
		fmt.Printf("No tag '%s' found.\n", tagName)
		os.Exit(1)
	}
	Tasks = append(Tasks, ws.Task{Text: taskText, Tag: tag})
}

func DeleteTask(n int) {
	Tasks = append(Tasks[:n-1], Tasks[n:]...)
}

// save, delete and append task
func ProcrastinateTask(n int) {
	t := Tasks[n-1]
	Tasks = append(Tasks[:n-1], Tasks[n:]...)
	Tasks = append(Tasks, t)
}

func TopTask(n int) {
	var NewTasks []ws.Task

	NewTasks = append(NewTasks, Tasks[n-1])
	NewTasks = append(NewTasks, Tasks[:n-1]...)
	if n < len(Tasks) {
		NewTasks = append(NewTasks, Tasks[n:]...)
	}

	Tasks = NewTasks
}

func DoneTask(n int) {
	TasksDone = append(TasksDone, ws.TaskDone{
		Task: Tasks[n-1],
		Date: time.Now(),
	})
	Tasks = append(Tasks[:n-1], Tasks[n:]...)
}

func UndoneTask(n int) {
	Tasks = append(Tasks, TasksDone[n-1].Task)
	TasksDone = append(TasksDone[:n-1], TasksDone[n:]...)
}

func ListTasks(showDone bool) {
	if len(Tasks) == 0 && len(TasksDone) == 0 {
		fmt.Println("No tasks.")
		return
	}

	if showDone && len(TasksDone) <= 0 {
		showDone = false
	}

	if len(Tasks) > 0 {
		if showDone {
			fmt.Println("Active:")
		}
		for i, t := range Tasks {
			fmt.Printf("% 2d. %s\n", i+1, t)
		}
	}

	if showDone {
		fmt.Println("Done:")
		for i, t := range TasksDone {
			fmt.Printf("% 2d. %s\n", i+1, t)
		}
	}
}

func LsTasks() {
	if len(Tasks) == 0 {
		fmt.Println("No tasks.")
		return
	}
	for i := 0; i < len(Tasks) && i < ws.TASK_LIST_COUNT; i++ {
		fmt.Printf("%2d. %s\n", i+1, Tasks[i])
	}
}

func AddTag(tagName ws.Tag) {
	for i := 0; i < len(Tags); i++ {
		if tagName == Tags[i] {
			fmt.Printf("Tag '%s' already exists.\n", tagName)
			os.Exit(1)
		}
	}
	Tags = append(Tags, tagName)
}

func DeleteTag(n int) {
	Tags = append(Tags[:n-1], Tags[n:]...)
}

func ListTags() {
	if len(Tags) == 0 {
		fmt.Println("No tags.")
	}
	for i := 0; i < len(Tags); i++ {
		fmt.Printf("%2d. %s\n", i+1, Tags[i])
	}
}

func wsTagUsage() {
	fmt.Println(`usage: ws tag <command>
COMMANDS
    add     Add a new tag
    del     Delete a tag
    list    List tags`)
}

func wsUsage() {
	fmt.Println(`usage: ws <command> [flag]
COMMANDS
    task    Add a new task
    done    Mark an active task as done
    undone  Undo a done task
    del     Delete an active task
    pc      Procrastinate an active task
    top     Put a task to the top of the stack
    ls      Short list of active tasks
    list    List all active and done tasks`)
}

func main() {
	var (
		dec         *gob.Decoder
		f           *os.File
		err         error
		gobdataPath string = ws.GetGobdataPath()
	)

	// Open/Create gob data file if not exist
	{
		f, err = os.Open(gobdataPath)
		if errors.Is(err, os.ErrNotExist) {
			// Do nothing
		} else if err != nil {
			panic(err)
		} else {
			dec = gob.NewDecoder(f)
			err = dec.Decode(&Tasks)
			if err != nil {
				panic(err)
			}
			err = dec.Decode(&TasksDone)
			if err != nil {
				panic(err)
			}
			err = dec.Decode(&Tags)
			if err != nil {
				panic(err)
			}
		}
	}

	// When no arguments are provided display the first task.
	if len(os.Args) == 1 {
		LsTasks()
		os.Exit(0)
	}

	switch os.Args[1] {
	// Add a new task
	case "add":
		var tagName, taskName string

		flagSet := flag.NewFlagSet("add", flag.ExitOnError)
		flagSet.StringVar(&tagName, "t", "", "Set tag name")
		flagSet.Parse(os.Args[2:])

		taskName = strings.Join(flagSet.Args(), " ")

		AddTask(tagName, taskName)
		ListTasks(false)

	// Delete an active task
	case "del":
		var n int

		flagSet := flag.NewFlagSet("del", flag.ExitOnError)
		flagSet.IntVar(&n, "n", 1, "Set task number")
		flagSet.Parse(os.Args[2:])

		if len(Tasks) <= 0 {
			fmt.Println("No tasks to delete.")
			os.Exit(1)
		}

		if len(Tasks) < n {
			fmt.Println("Task number out of range")
			os.Exit(1)
		}

		DeleteTask(n)
		ListTasks(false)

	// Mark an active task as done
	case "done":
		var n int

		flagSet := flag.NewFlagSet("done", flag.ExitOnError)
		flagSet.IntVar(&n, "n", 1, "Set task number")
		flagSet.Parse(os.Args[2:])

		if len(Tasks) <= 0 {
			fmt.Println("No tasks to be done.")
			os.Exit(1)
		}

		if len(Tasks) < n {
			fmt.Println("Task number out of range")
			os.Exit(1)
		}

		DoneTask(n)
		ListTasks(true)

	// Undo a done task
	case "undone":
		var n int

		flagSet := flag.NewFlagSet("undone", flag.ExitOnError)
		flagSet.IntVar(&n, "n", 1, "Set task number")
		flagSet.Parse(os.Args[2:])

		if len(TasksDone) <= 0 {
			fmt.Println("No tasks to be undone.")
			os.Exit(1)
		}

		if len(TasksDone) < n {
			fmt.Println("Task number out of range")
			os.Exit(1)
		}

		UndoneTask(n)
		ListTasks(true)

	// Procrastinate an active task
	case "pc":
		var n int

		flagSet := flag.NewFlagSet("procrastinate", flag.ExitOnError)
		flagSet.IntVar(&n, "n", 1, "Set task number")
		flagSet.Parse(os.Args[2:])

		if len(Tasks) <= 0 {
			fmt.Println("No tasks to procrastinate.")
			os.Exit(1)
		}

		if len(Tasks) < n {
			fmt.Println("Task number out of range")
			os.Exit(1)
		}

		ProcrastinateTask(n)
		ListTasks(false)

	// Put a task at the top
	case "top":
		var n int

		flagSet := flag.NewFlagSet("top", flag.ExitOnError)
		flagSet.IntVar(&n, "n", 0, "Set task number")
		flagSet.Parse(os.Args[2:])

		if n == 0 {
			fmt.Println("Task number is required.")
			os.Exit(1)
		}

		if len(Tasks) <= 1 {
			fmt.Println("No tasks to put to the top.")
			os.Exit(1)
		}

		if n == 1 {
			fmt.Println("Task already at the top")
			os.Exit(1)
		}

		if len(Tasks) < n {
			fmt.Println("Task number out of range")
			os.Exit(1)
		}

		TopTask(n)
		ListTasks(false)

	// Short list of active tasks
	case "ls":
		LsTasks()

	// List all active and done tasks
	case "list":
		ListTasks(true)

	// tag subcommand
	case "tag":
		if len(os.Args) <= 2 {
			wsTagUsage()
			return
		}

		switch os.Args[2] {

		// create a new tag
		case "add":
			tagName := ws.Tag(strings.Join(os.Args[3:], " "))
			AddTag(tagName)
			ListTags()

		// delete a tag
		case "del":
			var n int

			flagSet := flag.NewFlagSet("del", flag.ExitOnError)
			flagSet.IntVar(&n, "n", 1, "Set task number")
			flagSet.Parse(os.Args[3:])

			if len(Tags) <= 0 {
				fmt.Println("No tags to delete.")
				os.Exit(1)
			}

			if len(Tags) < n {
				fmt.Println("Tag number out of range")
				os.Exit(1)
			}

			DeleteTag(n)
			ListTags()

		/* list tags */
		case "list":
			ListTags()
		default:
			wsTagUsage()
		}

	default:
		wsUsage()
	}

	// Save data to gobdata
	f, err = os.Create(gobdataPath)
	if err != nil {
		panic(err)
	}
	enc := gob.NewEncoder(f)
	err = enc.Encode(Tasks)
	if err != nil {
		panic(err)
	}
	err = enc.Encode(TasksDone)
	if err != nil {
		panic(err)
	}
	err = enc.Encode(Tags)
	if err != nil {
		panic(err)
	}

}