package todotxt

import (
	"bufio"
	"errors"
	"fmt"
	"io/ioutil"
	"os"
	"sort"
	"strings"
)

type TodoList struct {
	Todos    []*Todo `json:"todos"`
	SortFlag int     `json:"sortFlag"`
}

// Newtodolist creates a new empty todolist.
func NewTodoList() *TodoList                     { return &TodoList{Todos: []*Todo{}} }
func (todolist *TodoList) Size() int             { return len(todolist.Todos) }
func (todolist *TodoList) GetTaskSlice() []*Todo { return todolist.Todos }

func (todolist *TodoList) Contains(t *Todo) bool {
	for _, tsk := range todolist.Todos {
		if tsk == t {
			return true
		}
	}
	return false
}

func (todolist *TodoList) GetTasksWithContext(context string) *TodoList {
	return todolist.Filter(func(t *Todo) bool {
		return t.HasContext(context)
	})
}

func (todolist *TodoList) GetTasksWithProject(project string) *TodoList {
	return todolist.Filter(func(t *Todo) bool {
		return t.HasProject(project)
	})
}

func (todolist *TodoList) GetContexts() []string {
	var ret []string
	added := make(map[string]bool)
	for _, tsk := range todolist.Todos {
		for _, c := range tsk.Contexts {
			if !added[c] {
				ret = append(ret, c)
				added[c] = true
			}
		}
	}
	sort.Strings(ret)
	return ret
}
func (todolist *TodoList) GetProjects() []string {
	var ret []string
	added := make(map[string]bool)
	for _, tsk := range todolist.Todos {
		for _, p := range tsk.Projects {
			if !added[p] {
				ret = append(ret, p)
				added[p] = true
			}
		}
	}
	sort.Strings(ret)
	return ret
}
func (todolist *TodoList) GetTagKVList() []string {
	var ret []string
	added := make(map[string]bool)
	for _, tsk := range todolist.Todos {
		for k, v := range tsk.AdditionalTags {
			tag := fmt.Sprintf("%s:%s", k, v)
			if !added[tag] {
				ret = append(ret, tag)
				added[tag] = true
			}
		}
	}
	sort.Strings(ret)
	return ret
}
func (todolist *TodoList) GetTagKeys() []string {
	var ret []string
	added := make(map[string]bool)
	for _, tsk := range todolist.Todos {
		for k := range tsk.AdditionalTags {
			if !added[k] {
				ret = append(ret, k)
				added[k] = true
			}
		}
	}
	sort.Strings(ret)
	return ret
}
func (todolist *TodoList) GetTagValuesForKey(key string) []string {
	var ret []string
	added := make(map[string]bool)
	for _, tsk := range todolist.Todos {
		if v, ok := tsk.AdditionalTags[key]; ok && !added[v] {
			ret = append(ret, v)
			added[v] = true
		}
	}
	sort.Strings(ret)
	return ret
}

func (todolist *TodoList) GetIncompleteTasks() *TodoList {
	t := *NewTodoList()
	for _, v := range todolist.Todos {
		if !v.Completed {
			t.Todos = append(t.Todos, v)
		}
	}
	return &t
}

func (todolist *TodoList) GetNextId() int {
	nextId := 0
	for _, v := range todolist.Todos {
		if v.Id > nextId {
			nextId = v.Id
		}
	}
	return nextId + 1
}

// String returns a complete list of tasks in todo.txt format.
func (todolist *TodoList) String() string {
	var ret string
	for _, todo := range todolist.Todos {
		ret += fmt.Sprintf("%s\n", todo.String())
	}
	return ret
}

// AddTodo prepends a Todo to the current TodoList and takes care to set the Todo.Id correctly
func (todolist *TodoList) AddTodo(todo *Todo) {
	todo.Id = todolist.GetNextId()
	todolist.Todos = append(todolist.Todos, todo)
	todolist.refresh()
}

// AddTimers adds all passed in timers to the list, sorts the list, then updates the Timer.Id values.
func (todolist *TodoList) AddTodos(todos []*Todo) {
	for _, v := range todos {
		todolist.AddTodo(v)
	}
}
func (todolist *TodoList) Combine(other *TodoList) { todolist.AddTodos(other.Todos) }

// GetTodo returns the Todo with the given todo 'id' from the TodoList.
// Returns an error if Todo could not be found.
func (todolist *TodoList) GetTodo(id int) (*Todo, error) {
	for i := range todolist.Todos {
		if todolist.Todos[i].Id == id {
			return todolist.Todos[i], nil
		}
	}
	return nil, errors.New("todo not found")
}

// RemoveTodoById removes any Todo with the given Todo 'id' from the TodoList.
// Returns an error if no Todo was removed
func (todolist *TodoList) RemoveTodoById(id int) error {
	found := false
	var remIdx int
	var t *Todo
	for remIdx, t = range todolist.Todos {
		if t.Id == id {
			found = true
			break
		}
	}
	if !found {
		return errors.New("todo not found")
	}
	todolist.Todos = append(todolist.Todos[:remIdx], todolist.Todos[remIdx+1:]...)
	todolist.refresh()
	return nil
}

// RemoveTodo removes any Todo from the TodoList with the same String representation as the given Todo.
// Returns an error if no Todo was removed.
func (todolist *TodoList) RemoveTodo(todo Todo) error {
	found := false
	var remIdx int
	var t *Todo
	for remIdx, t = range todolist.Todos {
		if t.String() == todo.String() {
			found = true
			break
		}
	}
	if !found {
		return errors.New("todo not found")
	}
	todolist.Todos = append(todolist.Todos[:remIdx], todolist.Todos[remIdx+1:]...)
	todolist.refresh()
	return nil
}

// ArchiveTodoToFile removes the todo from the active list and concatenates it to
// the passed in filename
// Return an err if any part of that fails
func (todolist *TodoList) ArchiveTodoToFile(todo Todo, filename string) error {
	if err := todolist.RemoveTodo(todo); err != nil {
		return err
	}
	f, err := os.OpenFile(filename, os.O_APPEND|os.O_WRONLY, 0600)
	if err != nil {
		return err
	}
	defer f.Close()
	_, err = f.WriteString(todo.String() + "\n")
	return err
}

// Filter filters the current TodoList for the given predicate (a function that takes a todo as input and returns a
// bool), and returns a new TodoList. The original TodoList is not modified.
func (todolist *TodoList) Filter(predicate func(*Todo) bool) *TodoList {
	var newList TodoList
	for _, t := range todolist.Todos {
		if predicate(t) {
			newList.Todos = append(newList.Todos, t)
		}
	}
	return &newList
}

func (todolist *TodoList) ResetIds() {
	todoId := 1
	for _, v := range todolist.Todos {
		v.Id = todoId
		todoId++
	}
}

// LoadFromFile loads a TodoList from *os.File.
// Note: This will clear the current TodoList and overwrite it's contents with whatever is in *os.File.
func (todolist *TodoList) LoadFromFile(file *os.File) error {
	todolist.Todos = []*Todo{} // Empty todolist
	todoId := 1
	scanner := bufio.NewScanner(file)
	for scanner.Scan() {
		text := strings.Trim(scanner.Text(), "\t\n\r") // Read Line
		// Ignore blank lines
		if text == "" {
			continue
		}
		todo, err := ParseTodo(text)
		if err != nil {
			return err
		}
		todo.Id = todoId
		todoId++
		todolist.Todos = append(todolist.Todos, todo)
	}
	if err := scanner.Err(); err != nil {
		return err
	}
	todolist.refresh()
	return nil
}

// WriteToFile writes a TodoList to *os.File
func (todolist *TodoList) WriteToFile(file *os.File) error {
	writer := bufio.NewWriter(file)
	_, err := writer.WriteString(todolist.String())
	writer.Flush()
	if err != nil {
		return err
	}
	todolist.ResetIds()
	return nil
}

// LoadFromFilename loads a TodoList from the filename.
func (todolist *TodoList) LoadFromFilename(filename string) error {
	file, err := os.Open(filename)
	if err != nil {
		return err
	}
	defer file.Close()
	return todolist.LoadFromFile(file)
}

// WriteToFilename writes a TodoList to the specified file (most likely called "todo.txt").
func (todolist *TodoList) WriteToFilename(filename string) error {
	if err := ioutil.WriteFile(filename, []byte(todolist.String()), 0640); err != nil {
		return err
	}
	todolist.ResetIds()
	return nil
}

// LoadFromFile loads and returns a TodoList from *os.File.
func LoadFromFile(file *os.File) (*TodoList, error) {
	todolist := TodoList{}
	if err := todolist.LoadFromFile(file); err != nil {
		return nil, err
	}
	return &todolist, nil
}

// WriteToFile writes a TodoList to *os.File.
func WriteToFile(todolist *TodoList, file *os.File) error {
	return todolist.WriteToFile(file)
}

// LoadFromFilename loads and returns a TodoList from a file (most likely called "todo.txt")
func LoadFromFilename(filename string) (*TodoList, error) {
	todolist := TodoList{}
	if err := todolist.LoadFromFilename(filename); err != nil {
		return nil, err
	}
	return &todolist, nil
}

// WriteToFilename write a TodoList to the specified file (most likely called "todo.txt")
func WriteToFilename(todolist *TodoList, filename string) error {
	return todolist.WriteToFilename(filename)
}