package ui

import (
	"regexp"
	"strings"
	"time"

	"github.com/gdamore/tcell/v2"
	"github.com/rivo/tview"
)

type level int

const (
	levelInfo level = iota
	levelSuccess
	levelWarn
	levelError
)

func (l level) String() string {
	return [...]string{"INFO", "OK", "WARN", "ERROR"}[l]
}

func (l level) color() tcell.Color {
	return [...]tcell.Color{tcell.ColorWhite, tcell.ColorGreen, tcell.ColorYellow, tcell.ColorRed}[l]
}

// how long a toast stays on screen, and how long the end of that time fades.
func (l level) lifetime() time.Duration {
	return [...]time.Duration{3 * time.Second, 3 * time.Second, 5 * time.Second, 8 * time.Second}[l]
}

const (
	toastFade = time.Second
	maxToasts = 4
)

type toast struct {
	text    string
	level   level
	expires time.Time
}

// progress toasts ("Searching…") are replaced by the next message.
func (t toast) progress() bool { return strings.HasSuffix(t.text, "…") }

var (
	tagRe       = regexp.MustCompile(`\[([^\[\]]*)\[\]|\[[^\[\]]*\]`)
	levelPrefix = []struct {
		tag   string
		level level
	}{{"[red]", levelError}, {"[green]", levelSuccess}, {"[yellow]", levelWarn}}
)

// plainText removes tview color tags and undoes tview.Escape.
func plainText(s string) string {
	return tagRe.ReplaceAllStringFunc(s, func(m string) string {
		if strings.HasSuffix(m, "[]") {
			return m[:len(m)-2] + "]"
		}
		return ""
	})
}

// SetMessage reports something to the user: as a short-lived popup and, unless
// it is only progress ("Adding…"), as an entry in the log. A leading [red],
// [yellow] or [green] tag selects the level; an empty text dismisses progress
// popups. UI goroutine only; use post from other goroutines.
func (a *App) SetMessage(text string) {
	if text == "" {
		a.dropProgress()
		return
	}
	lvl := levelInfo
	for _, p := range levelPrefix {
		if strings.HasPrefix(text, p.tag) {
			lvl, text = p.level, strings.TrimPrefix(text, p.tag)
			break
		}
	}
	a.Notify(lvl, plainText(text))
}

// Notify shows a popup and logs the message. UI goroutine only.
func (a *App) Notify(l level, text string) {
	t := toast{text: text, level: l, expires: time.Now().Add(l.lifetime())}
	a.dropProgress()
	if !t.progress() {
		a.logs.add(l, text)
	}
	a.toasts = append(a.toasts, t)
	if len(a.toasts) > maxToasts {
		a.toasts = a.toasts[len(a.toasts)-maxToasts:]
	}
	// Redraw when the fade starts and when the toast is gone.
	for _, d := range []time.Duration{l.lifetime() - toastFade, l.lifetime() + 50*time.Millisecond} {
		time.AfterFunc(d, func() { a.post(func() {}) })
	}
}

func (a *App) dropProgress() {
	kept := a.toasts[:0]
	for _, t := range a.toasts {
		if !t.progress() {
			kept = append(kept, t)
		}
	}
	a.toasts = kept
}

// toastRoot draws the popups above the whole interface.
type toastRoot struct {
	*tview.Flex
	app *App
}

// narrowWidth is the terminal width below which the six tabs and the full
// service names no longer fit on one line.
const narrowWidth = 92

func (r *toastRoot) Draw(screen tcell.Screen) {
	w, _ := screen.Size()
	r.app.setNarrow(w < narrowWidth)
	r.Flex.Draw(screen)
	a := r.app
	now := time.Now()
	kept := a.toasts[:0]
	for _, t := range a.toasts {
		if now.Before(t.expires) {
			kept = append(kept, t)
		}
	}
	a.toasts = kept

	w, h := screen.Size()
	y := h - 3 // above the status bar
	for i := len(a.toasts) - 1; i >= 0 && y >= 1; i-- {
		t := a.toasts[i]
		text := " " + t.text + " "
		width := min(tview.TaggedStringWidth(text), w-2)
		x := w - width - 1
		fg := t.level.color()
		if t.expires.Sub(now) < toastFade {
			fg = tcell.ColorGray // fade out
		}
		style := tcell.StyleDefault.Background(tcell.NewRGBColor(30, 30, 40)).Foreground(fg)
		for cx := x; cx < x+width; cx++ {
			screen.SetContent(cx, y, ' ', nil, style)
		}
		col := x
		for _, ch := range text {
			if col >= x+width {
				break
			}
			screen.SetContent(col, y, ch, nil, style)
			col += tview.TaggedStringWidth(string(ch))
		}
		y--
	}
}