package main

import (
	"sort"
	"strings"
	"time"

	todotxt "github.com/br0xen/go-todotxt"
)

// diskListChanged returns true if the task list in todo.txt
// is different than what we have previously loaded.
func (a *AppState) diskListChanged() bool {
	if !a.taskListLoaded {
		return false
	}
	curr, err := todotxt.LoadFromFilename(a.getTodoFile())
	if err != nil {
		return false
	}
	return curr.String() != a.TaskList.String()
}

// diskDoneListChanged returns true if the task list in done.txt
// is different than what we have previously loaded.
func (a *AppState) diskDoneListChanged() bool {
	if !a.doneListLoaded {
		return false
	}
	curr, err := todotxt.LoadFromFilename(a.getDoneFile())
	if err != nil {
		return false
	}
	return curr.String() != a.DoneList.String()
}

func (a *AppState) addTask(taskString string) error {
	if a.diskListChanged() {
		return a.e(ResStrListChanged)
	}
	t, err := todotxt.ParseTask(taskString)
	if err != nil {
		return err
	}
	if t.CreatedDate.IsZero() {
		t.CreatedDate = time.Now()
	}
	a.TaskList.AddTask(t)
	return a.WriteList()
}

func (a *AppState) saveTask(t *todotxt.Task) error {
	lt, err := a.TaskList.GetTask(t.Id)
	if err != nil {
		return err
	}
	lt.Todo = t.Todo
	lt.Priority = t.Priority
	lt.Projects = t.Projects
	lt.Contexts = t.Contexts
	lt.AdditionalTags = t.AdditionalTags
	return a.WriteList()
}

func (a *AppState) toggleTaskComplete(id int) error {
	if a.diskListChanged() {
		return a.e(ResStrListChanged)
	}
	var task *todotxt.Task
	var err error
	if task, err = a.TaskList.GetTask(id); err != nil {
		return err
	}
	if task.Completed {
		task.Reopen()
	} else {
		task.Complete()
	}
	return a.WriteList()
}

func (a *AppState) archiveTask(id int) error {
	if a.diskListChanged() {
		return a.e(ResStrListChanged)
	}
	var err error
	var task *todotxt.Task
	if task, err = a.TaskList.GetTask(id); err != nil {
		return err
	}
	if err := a.TaskList.ArchiveTaskToFile(*task, a.getDoneFile()); err != nil {
		return err
	}
	a.TaskList.RemoveTask(*task)
	return a.WriteList()
}

func (a *AppState) unarchiveTask(id int) error {
	if a.diskListChanged() {
		return a.e(ResStrListChanged)
	}
	var err error
	var task *todotxt.Task
	if task, err = a.DoneList.GetTask(id); err != nil {
		return err
	}
	a.TaskList.AddTask(task)
	if err = a.WriteList(); err != nil {
		return err
	}
	a.DoneList.RemoveTask(*task)
	return a.WriteDoneList()
}

func (a *AppState) getFilterPredicate(filter string) func(todotxt.Task) bool {
	var predicates []func(todotxt.Task) bool
	// If none of the 'filter' is in upper-case, do a case-insensitive filter
	checkCase := true
	if strings.ToLower(filter) == filter {
		checkCase = false
	}
	filterParts := strings.Split(filter, " ")
	for _, part := range filterParts {
		if strings.HasPrefix(part, "@") {
			predicates = append(predicates, func(t todotxt.Task) bool {
				for _, v := range t.Contexts {
					if "@"+v == part {
						return true
					}
				}
				return false
			})
		} else if strings.HasPrefix(part, "+") {
			predicates = append(predicates, func(t todotxt.Task) bool {
				for _, v := range t.Projects {
					if "+"+v == part {
						return true
					}
				}
				return false
			})
		} else {
			predicates = append(predicates, func(t todotxt.Task) bool {
				val := t.Original
				if !checkCase {
					val = strings.ToLower(t.Original)
				}
				return strings.Contains(val, part)
			})
		}
	}
	return func(t todotxt.Task) bool {
		for _, v := range predicates {
			if v(t) {
				return true
			}
		}
		return false
	}
}

func (a *AppState) LoadTaskList() error {
	var err error
	var tl todotxt.TaskList
	tl, err = todotxt.LoadFromFilename(a.getTodoFile())
	a.TaskList = &tl
	a.taskListLoaded = true
	return err
}

func (a *AppState) LoadDoneList() error {
	var err error
	var tl todotxt.TaskList
	tl, err = todotxt.LoadFromFilename(a.getDoneFile())
	a.DoneList = &tl
	a.doneListLoaded = true
	return err
}

func (a *AppState) WriteList() error {
	if !a.taskListLoaded {
		return a.e(ResStrTaskListNotLoaded)
	}
	return a.TaskList.WriteToFilename(a.getTodoFile())
}

func (a *AppState) WriteDoneList() error {
	if !a.doneListLoaded {
		return a.e(ResStrDoneListNotLoaded)
	}
	return a.DoneList.WriteToFilename(a.getDoneFile())
}

func (a *AppState) AdvancedPrioritySort(t1, t2 *todotxt.Task) bool {
	if t1.HasPriority() && t2.HasPriority() {
		return t1.Priority < t2.Priority
	} else if t1.HasPriority() && !t2.HasPriority() {
		return t1.Priority <= "Y"
	} else if !t1.HasPriority() && t2.HasPriority() {
		return "Y" <= t2.Priority
	}
	return t1.HasPriority()
}

type customSort struct {
	list todotxt.TaskList
	by   func(t1, t2 *todotxt.Task) bool
}

func (c *customSort) Len() int {
	return len(c.list)
}

func (c *customSort) Swap(l, r int) {
	c.list[l], c.list[r] = c.list[r], c.list[l]
}

func (c *customSort) Less(l, r int) bool {
	return c.by(&c.list[l], &c.list[r])
}

type By func(t1, t2 *todotxt.Task) bool

func (by By) Sort(list []todotxt.Task) {
	ts := &customSort{
		list: list,
		by:   by,
	}
	sort.Sort(ts)
}