package itashi

import (
	"bytes"
	"fmt"
	"log"
	"os"
	"strconv"
	"strings"
	"text/template"
	"time"

	tea "github.com/charmbracelet/bubbletea"
)

const SHELF_LINE_DELIM = "\n----    ----    ----    ----\n"
const SHELF_COL_DELIM = "    "
const TIME_FORMAT = "2006-01-02T15:04:05 -07:00:00"
const FS_SAVE_LOCATION = "./todo.ta"
const SHELF_TEMPLATE = "{{.Id}}    {{.Title}}    {{.Desc}}    {{.Due}}    {{.Done}}    {{.Priority}}"

type Task struct {
	Id       int
	Title    string
	Desc     string
	Due      time.Time
	Done     bool
	Priority int
}

func GetDefualtSave() string {
	return fmt.Sprintf("%s/.config/itashi/todo.ta", os.Getenv("HOME"))
}

// lets make Task implement the tea.Model interface
func (t Task) Init() tea.Cmd {
	return nil

}

func (t Task) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
	return t, nil
}

func (t Task) View() string {
	return ""
}

type TaskShelf interface {
	// Modify the due date of an existing task
	ModifyDue(id int, due time.Time)
	// Modify the description field of an existing task
	ModifyDesc(id int, desc string)
	// Modify the priority of an existing task
	ModifyPriority(id int, pri int)
	// modify the title of an existing task
	ModifyTitle(id int, title string)
	// delete an existing task from the shelf
	DeleteTask(id int)
	// Mark a task as complete
	MarkDone(id int)
	// hopefully you dont need to call this! ;)
	ResetDone(id int)
	// Add a task to the shelf
	AddTask(t Task)
	// Retrieve all tasks in the shelf
	GetAll() []Task
	// Render a task to a task template
	RenderTask(task Task) string
}

/*
Retrieve all the tasks from the designated TaskShelf
*/
func GetTaskList(taskio TaskShelf) []Task {
	return taskio.GetAll()
}

/*
Grab all of the names of the tasks from the TaskShelf

	    :param t: a list of Task structs
		:returns: A list of the task names
*/
func GetTaskNames(t []Task) []string {
	var taskn []string
	for i := range t {
		taskn = append(taskn, t[i].Title)
	}
	return taskn
}

type FilesystemShelf struct {
	SaveLocation string
	Template     *template.Template
	TaskTempl    *template.Template
	Tasks        []Task
}

func (t *FilesystemShelf) RenderTask(task Task) string {
	var bw bytes.Buffer
	err := t.TaskTempl.Execute(&bw, task)
	if err != nil {
		log.Fatal("Had a problem rendering this task.", task, err)
	}
	return bw.String()
}

/*
Create a new filesystem shelf struct to reflect the filesystem shelf

	    :param save: the save location to store the shelf in
		:returns: a pointer to a FilesystemShelf struct
*/
func NewFilesystemShelf(save string) *FilesystemShelf {
	tmpl, err := template.New("task").Parse(SHELF_TEMPLATE)
	if err != nil {
		log.Fatal("Could not parse the shelf template! ", err)
	}
	tasktmpl, err := template.New("task").Parse(TASK_ITEM)
	if err != nil {
		log.Fatal("Couldnt parse task template. ", err)
	}

	shelf := &FilesystemShelf{
		SaveLocation: save,
		Template:     tmpl,
		TaskTempl:    tasktmpl,
		Tasks:        []Task{},
	}
	shelf.Tasks = shelf.GetAll()
	return shelf

}

// Retrieve all the tasks from the filesystem shelf
func (f *FilesystemShelf) GetAll() []Task {
	b, err := os.ReadFile(f.SaveLocation)
	if err != nil {
		log.Fatal(err)
	}
	return parseFilesystemShelf(b)
}

/*
Add a task to the filesystem shelf

	:param t: the Task struct to add
*/
func (f *FilesystemShelf) AddTask(t Task) {
	f.Tasks = append(f.Tasks, t)

	err := os.WriteFile(f.SaveLocation, marshalTaskToShelf(f.Tasks, f.Template), os.ModePerm)
	if err != nil {
		log.Fatal("Need to fix later, error writing to fs ", err)
	}
}

// Boiler plate so i can implement later
func (f *FilesystemShelf) ModifyDue(id int, due time.Time)  {}
func (f *FilesystemShelf) ModifyDesc(id int, desc string)   {}
func (f *FilesystemShelf) ModifyPriority(id int, pri int)   {}
func (f *FilesystemShelf) ModifyTitle(id int, title string) {}
func (f *FilesystemShelf) DeleteTask(id int)                {}
func (f *FilesystemShelf) MarkDone(id int)                  {}
func (f *FilesystemShelf) ResetDone(id int)                 {}

// private function for parsing the byte stream from the filesystem
func parseFilesystemShelf(data []byte) []Task {
	var filestring string
	filestring = string(data)
	items := strings.Split(filestring, SHELF_LINE_DELIM)
	var shelf []Task
	for i := range items {
		sect := strings.Split(items[i], SHELF_COL_DELIM)
		if len(sect) < 6 {
			continue
		}
		var id int
		var due time.Time
		var done bool
		var pri int
		var err error
		id, err = strconv.Atoi(sect[0])
		due, err = time.Parse(TIME_FORMAT, sect[3])
		done, err = strconv.ParseBool(sect[4])
		pri, err = strconv.Atoi(sect[5])
		if err != nil {
			log.Fatal("Couldnt parse from filesystem shelf", err)
		}

		shelf = append(shelf, Task{
			Id:       id,
			Title:    sect[1],
			Desc:     sect[2],
			Due:      due,
			Done:     done,
			Priority: pri,
		})

	}
	return shelf

}

/*
Helper function to marshal the tasks to the custom format

	     :param tasks: an array of Task structs
		 :returns: a byte array
*/
func marshalTaskToShelf(tasks []Task, templ *template.Template) []byte {
	var bw bytes.Buffer
	for i := range tasks {
		err := templ.Execute(&bw, tasks[i])
		if err != nil {
			log.Fatal("Error parsing data into template: ", err)
		}
		// dynamically allocating, no need for the read delim
		_, err = bw.Write([]byte(SHELF_LINE_DELIM))
		if err != nil {
			log.Fatal("Error parsing data into template: ", err)
		}

	}
	return bw.Bytes()
}