// Package ui contains the tview user interface.
package ui

import (
	"context"
	"fmt"
	"os"
	"strings"
	"time"

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

	"git.stinnesbeck.com/nils/arr-tui/internal/config"
	"git.stinnesbeck.com/nils/arr-tui/internal/radarr"
	"git.stinnesbeck.com/nils/arr-tui/internal/sabnzbd"
	"git.stinnesbeck.com/nils/arr-tui/internal/sonarr"
)

type view struct {
	key  rune
	name string
	body tview.Primitive
	// Optional hooks, called when the view becomes visible / hidden.
	onShow, onHide func()
	// hints lists the keys that work in this view (shown in the status bar).
	hints func() string
}

// App is the top-level arr-tui application.
type App struct {
	app    *tview.Application
	tabs   *tview.TextView
	pages  *tview.Pages
	status *tview.TextView
	views  []view
	active int

	toasts   []toast
	logs     *logView
	overlays []overlay // dialogs and full-screen views stacked above the pages

	services *tview.TextView
	state    map[string]serviceState // keyed by service name
	probes   []probe

	screen     tcell.Screen // remembered at the first draw, for the bell
	sab        *sabnzbd.Client
	notifyDone bool // announce finished downloads
	bell       bool
	covers     bool // poster thumbnails enabled
	coverStyle coverStyle
	coverCache *coverCache
}

// probe checks that one service answers; it returns its version.
type probe struct {
	name  string
	check func(ctx context.Context) (string, error)
}

// heartbeat is how often the connection indicators are refreshed in the
// background, so a service shows up as connected without visiting its view.
const heartbeat = 30 * time.Second

// serviceState is the last known connection state of a backend service.
type serviceState struct {
	known   bool
	version string
	err     error
}

// serviceNames fixes the order of the connection indicators.
var serviceNames = []string{"Radarr", "Sonarr", "SABnzbd"}

// overlay is a page stacked above the main views; focus is restored on close.
// hints replaces the view's key hints in the status bar while it is open.
type overlay struct {
	page  string
	focus tview.Primitive
	hints string
	full  bool   // full-screen view (can be left with F1-F5), as opposed to a dialog
	close func() // optional cleanup when the overlay is removed
}

// New builds the application shell: a tab bar, one page per view and a status bar.
func New(cfg *config.Config) *App {
	a := &App{
		app:    tview.NewApplication(),
		tabs:   tview.NewTextView().SetDynamicColors(true),
		pages:  tview.NewPages(),
		status: tview.NewTextView().SetDynamicColors(true),

		services: tview.NewTextView().SetDynamicColors(true).SetTextAlign(tview.AlignRight),
		state:    map[string]serviceState{},

		notifyDone: cfg.UI.ShouldNotifyDownloads(),
		bell:       cfg.UI.Bell,
		covers:     cfg.UI.ShowCovers(),
		coverStyle: coverStyleFor(cfg.UI.CoverStyle, os.Getenv),
		coverCache: newCoverCache(),
	}

	radarrClient := radarr.NewClient(cfg.Radarr.URL, cfg.Radarr.APIKey)
	sonarrClient := sonarr.NewClient(cfg.Sonarr.URL, cfg.Sonarr.APIKey)
	a.logs = newLogView(a)
	sabClient := sabnzbd.NewClient(cfg.SABnzbd.URL, cfg.SABnzbd.APIKey)
	a.sab = sabClient
	a.probes = []probe{
		{"Radarr", func(ctx context.Context) (string, error) {
			st, err := radarrClient.SystemStatus(ctx)
			return st.Version, err
		}},
		{"Sonarr", func(ctx context.Context) (string, error) {
			st, err := sonarrClient.SystemStatus(ctx)
			return st.Version, err
		}},
		{"SABnzbd", sabClient.Version},
	}
	library := newLibraryView(a, radarrClient, sonarrClient)
	downloads := newDownloadsView(a, sabClient,
		[]arrSource{
			{name: "Radarr", queue: radarrClient.Queue, remove: radarrClient.RemoveQueueItem},
			{name: "Sonarr", queue: sonarrClient.Queue, remove: sonarrClient.RemoveQueueItem},
		},
		time.Duration(cfg.UI.RefreshSeconds)*time.Second)
	a.views = []view{
		{key: '1', name: "Movies", body: newSearchView(a, radarrBackend{radarrClient}, cfg.Radarr).root, hints: searchHints},
		{key: '2', name: "Series", body: newSearchView(a, sonarrBackend{sonarrClient}, cfg.Sonarr).root, hints: searchHints},
		{key: '3', name: "Library", body: library.root, onShow: library.activate, hints: libraryHints},
		{key: '4', name: "Downloads", body: downloads.root, onShow: downloads.activate, onHide: downloads.deactivate, hints: downloads.hints},
		{key: '5', name: "Log", body: a.logs.root, onShow: a.logs.onShow, hints: logHints},
	}
	for i, v := range a.views {
		a.pages.AddPage(v.name, v.body, true, i == 0)
	}

	layout := tview.NewFlex().SetDirection(tview.FlexRow).
		AddItem(tview.NewFlex().
			AddItem(a.tabs, 0, 1, false).
			AddItem(a.services, 25, 0, false), 1, 0, false).
		AddItem(a.pages, 0, 1, true).
		AddItem(a.status, 1, 0, false)

	a.app.SetBeforeDrawFunc(func(s tcell.Screen) bool {
		a.screen = s
		return false
	})
	a.app.SetRoot(&toastRoot{Flex: layout, app: a}, true).EnableMouse(false)
	a.app.SetInputCapture(a.handleKey)
	a.switchTo(0)
	a.renderServices()
	return a
}

// SetService records the outcome of a request to a service and updates the
// connection indicators. UI goroutine only. A nil err means reachable.
func (a *App) SetService(name, version string, err error) {
	prev := a.state[name]
	if err == nil && version == "" {
		version = prev.version
	}
	a.state[name] = serviceState{known: true, version: version, err: err}
	// Log connection changes only, so background polling does not flood the log.
	switch {
	case err != nil && (!prev.known || prev.err == nil):
		a.logs.add(levelError, name+" unreachable: "+err.Error())
	case err == nil && (!prev.known || prev.err != nil):
		a.logs.add(levelSuccess, strings.TrimSpace(name+" "+version)+" connected")
	}
	a.renderServices()
}

func (a *App) renderServices() {
	var s string
	for _, n := range serviceNames {
		short := strings.TrimSuffix(n, "nzbd") // SABnzbd -> SAB, keeps the bar narrow
		st := a.state[n]
		switch {
		case !st.known:
			s += "[gray]○ " + short + "[-] "
		case st.err != nil:
			s += "[red]● " + short + "[-] "
		default:
			s += "[green]●[-] " + short + " "
		}
	}
	a.services.SetText(s)
}

// serviceSummary describes every service for the help screen.
func (a *App) serviceSummary() string {
	var b strings.Builder
	for _, n := range serviceNames {
		st := a.state[n]
		switch {
		case !st.known:
			fmt.Fprintf(&b, "[gray]○ %s: not contacted yet[-]\n", n)
		case st.err != nil:
			fmt.Fprintf(&b, "[red]● %s: %s[-]\n", n, tview.Escape(st.err.Error()))
		case st.version != "":
			fmt.Fprintf(&b, "[green]●[-] %s %s: connected\n", n, tview.Escape(st.version))
		default:
			fmt.Fprintf(&b, "[green]●[-] %s: connected\n", n)
		}
	}
	return b.String()
}

// post runs f on the UI goroutine and redraws. Safe to call from any goroutine.
func (a *App) post(f func()) {
	a.app.QueueUpdateDraw(f)
}

// Run starts the event loop and blocks until the application quits.
func (a *App) Run() error {
	stop := make(chan struct{})
	defer close(stop)
	go a.watchServices(stop)
	if a.notifyDone {
		ctx, cancel := context.WithCancel(context.Background())
		defer cancel()
		go a.watchDownloads(ctx, a.sab, a.bell)
	}
	return a.app.Run()
}

// watchServices checks all services now and then every heartbeat until stop is closed.
func (a *App) watchServices(stop <-chan struct{}) {
	tick := time.NewTicker(heartbeat)
	defer tick.Stop()
	for {
		for _, p := range a.probes {
			go func() {
				ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
				defer cancel()
				version, err := p.check(ctx)
				a.post(func() { a.SetService(p.name, version, err) })
			}()
		}
		select {
		case <-tick.C:
		case <-stop:
			return
		}
	}
}

func (a *App) renderStatus() {
	var hints string
	if n := len(a.overlays); n > 0 {
		hints = a.overlays[n-1].hints + " · Ctrl+C quit"
	} else {
		if h := a.views[a.active].hints; h != nil {
			hints = h() + " · "
		}
		hints += "? help · F1-F5 · q quit"
	}
	a.status.SetText("[gray]" + hints)
}

// pushOverlay stacks p above everything and focuses focus.
func (a *App) pushOverlay(p, focus tview.Primitive, hints string, full bool, onClose func()) {
	name := fmt.Sprintf("overlay-%d", len(a.overlays))
	a.overlays = append(a.overlays, overlay{page: name, focus: a.app.GetFocus(), hints: hints, full: full, close: onClose})
	a.pages.AddPage(name, p, true, true)
	a.app.SetFocus(focus)
	a.renderStatus()
}

// openModal shows p centered above the current view.
func (a *App) openModal(p tview.Primitive, width, height int) {
	box := tview.NewFlex().
		AddItem(nil, 0, 1, false).
		AddItem(tview.NewFlex().SetDirection(tview.FlexRow).
			AddItem(nil, 0, 1, false).
			AddItem(p, height, 0, true).
			AddItem(nil, 0, 1, false), width, 0, true).
		AddItem(nil, 0, 1, false)
	a.pushOverlay(box, p, "↑↓ move · ←→ change · Enter select · Esc cancel", false, nil)
}

// openSidePanel shows p at the top right so most of the view behind it stays
// visible, for dialogs whose changes are applied live.
func (a *App) openSidePanel(p tview.Primitive, width, height int, hints string, onClose func()) {
	box := tview.NewFlex().
		AddItem(nil, 0, 1, false).
		AddItem(tview.NewFlex().SetDirection(tview.FlexRow).
			AddItem(p, height, 0, true).
			AddItem(nil, 0, 1, false), width, 0, true)
	a.pushOverlay(box, p, hints, false, onClose)
}

// openFull shows p above the whole view area (the tab bar and status bar stay visible).
func (a *App) openFull(p tview.Primitive, hints string, onClose func()) {
	a.pushOverlay(p, p, hints, true, onClose)
}

// closeModal removes the topmost overlay and restores the previous focus.
func (a *App) closeModal() {
	if len(a.overlays) == 0 {
		return
	}
	top := a.overlays[len(a.overlays)-1]
	a.overlays = a.overlays[:len(a.overlays)-1]
	a.pages.RemovePage(top.page)
	if top.close != nil {
		top.close()
	}
	if top.focus != nil {
		a.app.SetFocus(top.focus)
	}
	a.renderStatus()
}

// confirm asks a yes/no question; yes runs only if the user picks Delete/Yes.
func (a *App) confirm(text string, yes func()) {
	lines := strings.Count(text, "\n") + 1 + len([]rune(text))/44
	m := tview.NewModal().
		SetText(text).
		AddButtons([]string{"Cancel", "Confirm"}). // Cancel first so a stray Enter is safe
		SetDoneFunc(func(i int, _ string) {
			a.closeModal()
			if i == 1 {
				yes()
			}
		})
	a.openModal(m, 60, 7+min(lines, 10))
}

// onlyFullOverlays is true when no dialog is open (full-screen views may be).
func (a *App) onlyFullOverlays() bool {
	for _, o := range a.overlays {
		if !o.full {
			return false
		}
	}
	return true
}

// typing reports whether keystrokes belong to a text field or dialog and must
// not trigger global shortcuts.
func (a *App) typing() bool {
	if len(a.overlays) > 0 {
		return true
	}
	_, isInput := a.app.GetFocus().(*tview.InputField)
	return isInput
}

func (a *App) handleKey(ev *tcell.EventKey) *tcell.EventKey {
	if ev.Key() == tcell.KeyCtrlC {
		a.app.Stop()
		return nil
	}
	// Shortcuts that also work while typing in a search box. Dialogs block them;
	// full-screen views (release list, episodes) are closed by a view switch.
	if a.onlyFullOverlays() {
		if ev.Key() == tcell.KeyF9 && len(a.overlays) == 0 {
			a.showHelp()
			return nil
		}
		if i := a.viewShortcut(ev); i >= 0 && i < len(a.views) {
			for len(a.overlays) > 0 {
				a.closeModal()
			}
			a.switchTo(i)
			return nil
		}
	}
	if a.typing() {
		return ev
	}
	switch ev.Key() {
	case tcell.KeyRune:
		if ev.Rune() == 'q' {
			a.app.Stop()
			return nil
		}
	}
	return ev
}

// viewShortcut returns the view index for F1-F5, or -1.
func (a *App) viewShortcut(ev *tcell.EventKey) int {
	if ev.Key() >= tcell.KeyF1 && ev.Key() <= tcell.KeyF12 {
		return int(ev.Key() - tcell.KeyF1)
	}
	return -1
}

func (a *App) switchTo(i int) {
	if hide := a.views[a.active].onHide; hide != nil && i != a.active {
		hide()
	}
	if show := a.views[i].onShow; show != nil && i != a.active {
		show()
	}
	a.active = i
	a.pages.SwitchToPage(a.views[i].name)
	a.renderTabs()
	a.renderStatus()
}

func (a *App) renderTabs() {
	var s string
	for i, v := range a.views {
		if i == a.active {
			s += fmt.Sprintf("[black:white] %c %s [-:-] ", v.key, v.name)
		} else {
			s += fmt.Sprintf("[gray] %c %s [-]", v.key, v.name)
		}
	}
	a.tabs.SetText(s)
}

func searchHints() string {
	return "/ search · Tab list/search · Enter add · i releases"
}

func libraryHints() string {
	return "Tab list · f status · F props · / text · t monitor · s search · d remove"
}

func logHints() string { return "↑↓ scroll · G follow · c clear" }