package views

import (
	"fmt"
	"strings"
	"time"

	"github.com/charmbracelet/bubbles/textinput"
	tea "github.com/charmbracelet/bubbletea"
	"github.com/charmbracelet/lipgloss"

	"task/internal/ticket"
)

// Time edit field indices.
const (
	FieldTimeStart = iota
	FieldTimeEnd
	TimeEditFieldCount
)

const timeEditLayout = "2006-01-02 15:04"

// TimeEditStyles styles the time-entry edit form.
type TimeEditStyles struct {
	Label   lipgloss.Style
	Focused lipgloss.Style
	Blurred lipgloss.Style
	Hint    lipgloss.Style
	Title   lipgloss.Style
}

// DefaultTimeEditStyles returns sensible defaults.
func DefaultTimeEditStyles() TimeEditStyles {
	return TimeEditStyles{
		Label:   lipgloss.NewStyle().Foreground(lipgloss.Color("245")),
		Focused: lipgloss.NewStyle().Foreground(lipgloss.Color("205")),
		Blurred: lipgloss.NewStyle().Foreground(lipgloss.Color("240")),
		Hint:    lipgloss.NewStyle().Foreground(lipgloss.Color("241")),
		Title:   lipgloss.NewStyle().Bold(true),
	}
}

// TimeEditForm edits start and end of a time entry.
type TimeEditForm struct {
	Inputs []textinput.Model
	Focus  int
	Styles TimeEditStyles
	Width  int
}

// NewTimeEditForm builds a form prefilled from an entry.
func NewTimeEditForm(e ticket.TimeEntry, width int) TimeEditForm {
	styles := DefaultTimeEditStyles()
	inputs := make([]textinput.Model, TimeEditFieldCount)

	mk := func(placeholder string) textinput.Model {
		ti := textinput.New()
		ti.Placeholder = placeholder
		ti.CharLimit = 16
		ti.Width = max(20, width-10)
		return ti
	}

	inputs[FieldTimeStart] = mk(timeEditLayout)
	inputs[FieldTimeEnd] = mk(timeEditLayout)
	if !e.Start.IsZero() {
		inputs[FieldTimeStart].SetValue(e.Start.Local().Format(timeEditLayout))
	}
	if !e.End.IsZero() {
		inputs[FieldTimeEnd].SetValue(e.End.Local().Format(timeEditLayout))
	} else if !e.Start.IsZero() && e.Duration > 0 {
		inputs[FieldTimeEnd].SetValue(e.Start.Add(e.Duration).Local().Format(timeEditLayout))
	}

	f := TimeEditForm{
		Inputs: inputs,
		Focus:  FieldTimeStart,
		Styles: styles,
		Width:  width,
	}
	f.focusIndex(FieldTimeStart)
	return f
}

func (f *TimeEditForm) focusIndex(i int) {
	f.Focus = i
	for idx := range f.Inputs {
		if idx == i {
			f.Inputs[idx].Focus()
			f.Inputs[idx].PromptStyle = f.Styles.Focused
			f.Inputs[idx].TextStyle = f.Styles.Focused
		} else {
			f.Inputs[idx].Blur()
			f.Inputs[idx].PromptStyle = f.Styles.Blurred
			f.Inputs[idx].TextStyle = f.Styles.Blurred
		}
	}
}

// NextField moves focus to the next field.
func (f *TimeEditForm) NextField() {
	f.focusIndex((f.Focus + 1) % TimeEditFieldCount)
}

// PrevField moves focus to the previous field.
func (f *TimeEditForm) PrevField() {
	f.focusIndex((f.Focus - 1 + TimeEditFieldCount) % TimeEditFieldCount)
}

// Update forwards a message to the focused text input.
func (f *TimeEditForm) Update(msg tea.Msg) tea.Cmd {
	var cmd tea.Cmd
	f.Inputs[f.Focus], cmd = f.Inputs[f.Focus].Update(msg)
	return cmd
}

// Parse returns start and end in UTC, or an error.
func (f TimeEditForm) Parse() (start, end time.Time, err error) {
	startRaw := strings.TrimSpace(f.Inputs[FieldTimeStart].Value())
	endRaw := strings.TrimSpace(f.Inputs[FieldTimeEnd].Value())
	if startRaw == "" || endRaw == "" {
		return time.Time{}, time.Time{}, fmt.Errorf("start and end are required")
	}
	start, err = time.ParseInLocation(timeEditLayout, startRaw, time.Local)
	if err != nil {
		return time.Time{}, time.Time{}, fmt.Errorf("start: use %s", timeEditLayout)
	}
	end, err = time.ParseInLocation(timeEditLayout, endRaw, time.Local)
	if err != nil {
		return time.Time{}, time.Time{}, fmt.Errorf("end: use %s", timeEditLayout)
	}
	if !end.After(start) {
		return time.Time{}, time.Time{}, fmt.Errorf("end must be after start")
	}
	return start.UTC(), end.UTC(), nil
}

// View renders the form.
func (f TimeEditForm) View() string {
	var b strings.Builder
	b.WriteString(f.Styles.Title.Render("Edit time entry"))
	b.WriteString("\n\n")
	labels := []string{"Start", "End"}
	for i, label := range labels {
		b.WriteString(f.Styles.Label.Render(label+":"))
		b.WriteString(" ")
		b.WriteString(f.Inputs[i].View())
		b.WriteString("\n")
	}
	b.WriteString("\n")
	b.WriteString(f.Styles.Hint.Render("format " + timeEditLayout + " · tab fields · enter save · esc cancel"))
	return b.String()
}