package gui

import (
	"bytes"
	"io"
	"math"
	"sync"

	// "io"
	// "io/ioutil"

	"io/ioutil"
	"os"
	"os/exec"
	"time"

	"github.com/go-errors/errors"

	// "strings"

	"github.com/jesseduffield/gocui"
	"github.com/jesseduffield/lazydocker/pkg/commands"
	"github.com/jesseduffield/lazydocker/pkg/config"
	"github.com/jesseduffield/lazydocker/pkg/i18n"
	"github.com/jesseduffield/lazydocker/pkg/updates"
	"github.com/jesseduffield/lazydocker/pkg/utils"
	"github.com/sirupsen/logrus"
)

// OverlappingEdges determines if panel edges overlap
var OverlappingEdges = false

// SentinelErrors are the errors that have special meaning and need to be checked
// by calling functions. The less of these, the better
type SentinelErrors struct {
	ErrSubProcess   error
	ErrNoContainers error
}

// GenerateSentinelErrors makes the sentinel errors for the gui. We're defining it here
// because we can't do package-scoped errors with localization, and also because
// it seems like package-scoped variables are bad in general
// https://dave.cheney.net/2017/06/11/go-without-package-scoped-variables
// In the future it would be good to implement some of the recommendations of
// that article. For now, if we don't need an error to be a sentinel, we will just
// define it inline. This has implications for error messages that pop up everywhere
// in that we'll be duplicating the default values. We may need to look at
// having a default localisation bundle defined, and just using keys-only when
// localising things in the code.
func (gui *Gui) GenerateSentinelErrors() {
	gui.Errors = SentinelErrors{
		ErrSubProcess:   errors.New(gui.Tr.SLocalize("RunningSubprocess")),
		ErrNoContainers: errors.New(gui.Tr.SLocalize("NoChangedContainers")),
	}
}

// Teml is short for template used to make the required map[string]interface{} shorter when using gui.Tr.SLocalize and gui.Tr.TemplateLocalize
type Teml i18n.Teml

// Gui wraps the gocui Gui object which handles rendering and events
type Gui struct {
	g             *gocui.Gui
	Log           *logrus.Entry
	DockerCommand *commands.DockerCommand
	OSCommand     *commands.OSCommand
	SubProcess    *exec.Cmd
	State         guiState
	Config        config.AppConfigurer
	Tr            *i18n.Localizer
	Errors        SentinelErrors
	Updater       *updates.Updater
	statusManager *statusManager
	waitForIntro  sync.WaitGroup
}

type containerPanelState struct {
	SelectedLine int
}

type menuPanelState struct {
	SelectedLine int
}

type panelStates struct {
	Containers *containerPanelState
	Menu       *menuPanelState
}

type guiState struct {
	Containers       []*commands.Container
	MenuItemCount    int // can't store the actual list because it's of interface{} type
	PreviousView     string
	Platform         commands.Platform
	Updating         bool
	Panels           *panelStates
	SubProcessOutput string
}

// NewGui builds a new gui handler
func NewGui(log *logrus.Entry, dockerCommand *commands.DockerCommand, oSCommand *commands.OSCommand, tr *i18n.Localizer, config config.AppConfigurer, updater *updates.Updater) (*Gui, error) {

	initialState := guiState{
		Containers:   make([]*commands.Container, 0),
		PreviousView: "containers",
		Platform:     *oSCommand.Platform,
		Panels: &panelStates{
			Containers: &containerPanelState{SelectedLine: -1},
			Menu:       &menuPanelState{SelectedLine: 0},
		},
	}

	gui := &Gui{
		Log:           log,
		DockerCommand: dockerCommand,
		OSCommand:     oSCommand,
		State:         initialState,
		Config:        config,
		Tr:            tr,
		Updater:       updater,
		statusManager: &statusManager{},
	}

	gui.GenerateSentinelErrors()

	return gui, nil
}

func (gui *Gui) scrollUpMain(g *gocui.Gui, v *gocui.View) error {
	mainView, _ := g.View("main")
	ox, oy := mainView.Origin()
	newOy := int(math.Max(0, float64(oy-gui.Config.GetUserConfig().GetInt("gui.scrollHeight"))))
	return mainView.SetOrigin(ox, newOy)
}

func (gui *Gui) scrollDownMain(g *gocui.Gui, v *gocui.View) error {
	mainView, _ := g.View("main")
	ox, oy := mainView.Origin()
	y := oy
	if !gui.Config.GetUserConfig().GetBool("gui.scrollPastBottom") {
		_, sy := mainView.Size()
		y += sy
	}
	if y < len(mainView.BufferLines()) {
		return mainView.SetOrigin(ox, oy+gui.Config.GetUserConfig().GetInt("gui.scrollHeight"))
	}
	return nil
}

func (gui *Gui) handleRefresh(g *gocui.Gui, v *gocui.View) error {
	return gui.refreshSidePanels(g)
}

func max(a, b int) int {
	if a > b {
		return a
	}
	return b
}

// getFocusLayout returns a manager function for when view gain and lose focus
func (gui *Gui) getFocusLayout() func(g *gocui.Gui) error {
	var previousView *gocui.View
	return func(g *gocui.Gui) error {
		newView := gui.g.CurrentView()
		if err := gui.onFocusChange(); err != nil {
			return err
		}
		// for now we don't consider losing focus to a popup panel as actually losing focus
		if newView != previousView && !gui.isPopupPanel(newView.Name()) {
			if err := gui.onFocusLost(previousView, newView); err != nil {
				return err
			}
			if err := gui.onFocus(newView); err != nil {
				return err
			}
			previousView = newView
		}
		return nil
	}
}

func (gui *Gui) onFocusChange() error {
	currentView := gui.g.CurrentView()
	for _, view := range gui.g.Views() {
		view.Highlight = view == currentView
	}
	return nil
}

func (gui *Gui) onFocusLost(v *gocui.View, newView *gocui.View) error {
	if v == nil {
		return nil
	}
	gui.Log.Info(v.Name() + " focus lost")
	return nil
}

func (gui *Gui) onFocus(v *gocui.View) error {
	if v == nil {
		return nil
	}
	gui.Log.Info(v.Name() + " focus gained")
	return nil
}

// layout is called for every screen re-render e.g. when the screen is resized
func (gui *Gui) layout(g *gocui.Gui) error {
	g.Highlight = true
	width, height := g.Size()

	information := gui.Config.GetVersion()

	minimumHeight := 9
	minimumWidth := 10
	if height < minimumHeight || width < minimumWidth {
		v, err := g.SetView("limit", 0, 0, width-1, height-1, 0)
		if err != nil {
			if err.Error() != "unknown view" {
				return err
			}
			v.Title = gui.Tr.SLocalize("NotEnoughSpace")
			v.Wrap = true
			_, _ = g.SetViewOnTop("limit")
		}
		return nil
	}

	currView := gui.g.CurrentView()
	currentCyclebleView := gui.State.PreviousView
	if currView != nil {
		viewName := currView.Name()
		usePreviouseView := true
		for _, view := range cyclableViews {
			if view == viewName {
				currentCyclebleView = viewName
				usePreviouseView = false
				break
			}
		}
		if usePreviouseView {
			currentCyclebleView = gui.State.PreviousView
		}
	}

	usableSpace := height - 7
	extraSpace := usableSpace - (usableSpace/3)*3

	vHeights := map[string]int{
		"status":     3,
		"containers": (usableSpace / 3) + extraSpace,
		"options":    1,
	}

	if height < 28 {
		defaultHeight := 3
		if height < 21 {
			defaultHeight = 1
		}
		vHeights = map[string]int{
			"status":     defaultHeight,
			"containers": defaultHeight,
			"options":    defaultHeight,
		}
		vHeights[currentCyclebleView] = height - defaultHeight*4 - 1
	}

	optionsVersionBoundary := width - max(len(utils.Decolorise(information)), 1)
	leftSideWidth := width / 3

	appStatus := gui.statusManager.getStatusString()
	appStatusOptionsBoundary := 0
	if appStatus != "" {
		appStatusOptionsBoundary = len(appStatus) + 2
	}

	_, _ = g.SetViewOnBottom("limit")
	g.DeleteView("limit")

	v, err := g.SetView("main", leftSideWidth+1, 0, width-1, height-2, gocui.LEFT)
	if err != nil {
		if err.Error() != "unknown view" {
			return err
		}
		v.Title = gui.Tr.SLocalize("DiffTitle")
		v.Wrap = true
		v.FgColor = gocui.ColorWhite
	}

	if v, err := g.SetView("status", 0, 0, leftSideWidth, vHeights["status"]-1, gocui.BOTTOM|gocui.RIGHT); err != nil {
		if err.Error() != "unknown view" {
			return err
		}
		v.Title = gui.Tr.SLocalize("StatusTitle")
		v.FgColor = gocui.ColorWhite
	}

	containersView, err := g.SetViewBeneath("containers", "status", vHeights["containers"])
	if err != nil {
		if err.Error() != "unknown view" {
			return err
		}
		containersView.Highlight = true
		containersView.Title = gui.Tr.SLocalize("ContainersTitle")
		v.FgColor = gocui.ColorWhite
	}

	if v, err := g.SetView("options", appStatusOptionsBoundary-1, height-2, optionsVersionBoundary-1, height, 0); err != nil {
		if err.Error() != "unknown view" {
			return err
		}
		v.Frame = false
		if v.FgColor, err = gui.GetOptionsPanelTextColor(); err != nil {
			return err
		}
	}

	if appStatusView, err := g.SetView("appStatus", -1, height-2, width, height, 0); err != nil {
		if err.Error() != "unknown view" {
			return err
		}
		appStatusView.BgColor = gocui.ColorDefault
		appStatusView.FgColor = gocui.ColorCyan
		appStatusView.Frame = false
		if _, err := g.SetViewOnBottom("appStatus"); err != nil {
			return err
		}
	}

	if v, err := g.SetView("information", optionsVersionBoundary-1, height-2, width, height, 0); err != nil {
		if err.Error() != "unknown view" {
			return err
		}
		v.BgColor = gocui.ColorDefault
		v.FgColor = gocui.ColorGreen
		v.Frame = false
		if err := gui.renderString(g, "information", information); err != nil {
			return err
		}

		// doing this here because it'll only happen once
		if err := gui.loadNewRepo(); err != nil {
			return err
		}
	}

	if gui.g.CurrentView() == nil {
		if _, err := gui.g.SetCurrentView(gui.getContainersView().Name()); err != nil {
			return err
		}

		if err := gui.switchFocus(gui.g, nil, gui.getContainersView()); err != nil {
			return err
		}
	}

	if gui.State.SubProcessOutput != "" {
		output := gui.State.SubProcessOutput
		gui.State.SubProcessOutput = ""
		x, y := gui.g.Size()
		// if we just came back from vim, we don't want vim's output to show up in our popup
		if float64(len(output))*1.5 < float64(x*y) {
			return gui.createMessagePanel(gui.g, nil, "Output", output)
		}
	}

	type listViewState struct {
		selectedLine int
		lineCount    int
	}

	listViews := map[*gocui.View]listViewState{
		containersView: {selectedLine: gui.State.Panels.Containers.SelectedLine, lineCount: len(gui.State.Containers)},
	}

	// menu view might not exist so we check to be safe
	if menuView, err := gui.g.View("menu"); err == nil {
		listViews[menuView] = listViewState{selectedLine: gui.State.Panels.Menu.SelectedLine, lineCount: gui.State.MenuItemCount}
	}
	for view, state := range listViews {
		// check if the selected line is now out of view and if so refocus it
		if err := gui.focusPoint(0, state.selectedLine, state.lineCount, view); err != nil {
			return err
		}
	}

	// here is a good place log some stuff
	// if you download humanlog and do tail -f development.log | humanlog
	// this will let you see these branches as prettified json
	// gui.Log.Info(utils.AsJson(gui.State.Branches[0:4]))
	return gui.resizeCurrentPopupPanel(g)
}

func (gui *Gui) loadNewRepo() error {
	gui.Updater.CheckForNewUpdate(gui.onBackgroundUpdateCheckFinish, false)

	gui.waitForIntro.Done()

	if err := gui.refreshSidePanels(gui.g); err != nil {
		return err
	}

	if gui.Config.GetUserConfig().GetString("reporting") == "undetermined" {
		if err := gui.promptAnonymousReporting(); err != nil {
			return err
		}
	}
	return nil
}

func (gui *Gui) promptAnonymousReporting() error {
	return gui.createConfirmationPanel(gui.g, nil, gui.Tr.SLocalize("AnonymousReportingTitle"), gui.Tr.SLocalize("AnonymousReportingPrompt"), func(g *gocui.Gui, v *gocui.View) error {
		gui.waitForIntro.Done()
		return gui.Config.WriteToUserConfig("reporting", "on")
	}, func(g *gocui.Gui, v *gocui.View) error {
		gui.waitForIntro.Done()
		return gui.Config.WriteToUserConfig("reporting", "off")
	})
}

func (gui *Gui) renderAppStatus() error {
	appStatus := gui.statusManager.getStatusString()
	if appStatus != "" {
		return gui.renderString(gui.g, "appStatus", appStatus)
	}
	return nil
}

func (gui *Gui) renderGlobalOptions() error {
	return gui.renderOptionsMap(map[string]string{
		"PgUp/PgDn": gui.Tr.SLocalize("scroll"),
		"← → ↑ ↓":   gui.Tr.SLocalize("navigate"),
		"esc/q":     gui.Tr.SLocalize("close"),
		"x":         gui.Tr.SLocalize("menu"),
	})
}

func (gui *Gui) goEvery(interval time.Duration, function func() error) {
	go func() {
		for range time.Tick(interval) {
			_ = function()
		}
	}()
}

// Run setup the gui with keybindings and start the mainloop
func (gui *Gui) Run() error {
	g, err := gocui.NewGui(gocui.OutputNormal, OverlappingEdges)
	if err != nil {
		return err
	}
	defer g.Close()

	if gui.Config.GetUserConfig().GetBool("gui.mouseEvents") {
		g.Mouse = true
	}

	gui.g = g // TODO: always use gui.g rather than passing g around everywhere

	if err := gui.SetColorScheme(); err != nil {
		return err
	}

	if gui.Config.GetUserConfig().GetString("reporting") == "undetermined" {
		gui.waitForIntro.Add(2)
	} else {
		gui.waitForIntro.Add(1)
	}

	go func() {
		gui.waitForIntro.Wait()
		// TODO: see if this is right
		gui.goEvery(time.Second*10, gui.refreshContainers)
		gui.goEvery(time.Millisecond*50, gui.renderAppStatus)
	}()

	g.SetManager(gocui.ManagerFunc(gui.layout), gocui.ManagerFunc(gui.getFocusLayout()))

	if err = gui.keybindings(g); err != nil {
		return err
	}

	err = g.MainLoop()
	return err
}

// RunWithSubprocesses loops, instantiating a new gocui.Gui with each iteration
// if the error returned from a run is a ErrSubProcess, it runs the subprocess
// otherwise it handles the error, possibly by quitting the application
func (gui *Gui) RunWithSubprocesses() error {
	for {
		if err := gui.Run(); err != nil {
			if err == gocui.ErrQuit {
				break
			} else if err == gui.Errors.ErrSubProcess {
				gui.SubProcess.Stdin = os.Stdin
				output, err := gui.runCommand(gui.SubProcess)
				if err != nil {
					return err
				}
				gui.State.SubProcessOutput = output
				gui.SubProcess.Stdout = ioutil.Discard
				gui.SubProcess.Stderr = ioutil.Discard
				gui.SubProcess.Stdin = nil
				gui.SubProcess = nil
			} else {
				return err
			}
		}
	}
	return nil
}

// adapted from https://blog.kowalczyk.info/article/wOYk/advanced-command-execution-in-go-with-osexec.html
func (gui *Gui) runCommand(cmd *exec.Cmd) (string, error) {
	var stdoutBuf bytes.Buffer
	stdoutIn, _ := cmd.StdoutPipe()
	stderrIn, _ := cmd.StderrPipe()

	stdout := io.MultiWriter(os.Stdout, &stdoutBuf)
	stderr := io.MultiWriter(os.Stderr, &stdoutBuf)
	err := cmd.Start()
	if err != nil {
		return "", err
	}

	var wg sync.WaitGroup
	wg.Add(1)

	go func() {
		if _, err := io.Copy(stdout, stdoutIn); err != nil {
			gui.Log.Error(err)
		}

		wg.Done()
	}()

	if _, err := io.Copy(stderr, stderrIn); err != nil {
		return "", err
	}

	wg.Wait()

	if err := cmd.Wait(); err != nil {
		// not handling the error explicitly because usually we're going to see it
		// in the output anyway
		gui.Log.Error(err)
	}

	outStr := stdoutBuf.String()
	return outStr, nil
}

func (gui *Gui) quit(g *gocui.Gui, v *gocui.View) error {
	if gui.State.Updating {
		return gui.createUpdateQuitConfirmation(g, v)
	}
	if gui.Config.GetUserConfig().GetBool("confirmOnQuit") {
		return gui.createConfirmationPanel(g, v, "", gui.Tr.SLocalize("ConfirmQuit"), func(g *gocui.Gui, v *gocui.View) error {
			return gocui.ErrQuit
		}, nil)
	}
	return gocui.ErrQuit
}

func (gui *Gui) handleDonate(g *gocui.Gui, v *gocui.View) error {
	if !gui.g.Mouse {
		return nil
	}

	cx, _ := v.Cursor()
	if cx > len(gui.Tr.SLocalize("Donate")) {
		return nil
	}
	return gui.OSCommand.OpenLink("https://donorbox.org/lazydocker")
}

func (gui *Gui) editFile(filename string) error {
	_, err := gui.runSyncOrAsyncCommand(gui.OSCommand.EditFile(filename))
	return err
}

func (gui *Gui) openFile(filename string) error {
	if err := gui.OSCommand.OpenFile(filename); err != nil {
		return gui.createErrorPanel(gui.g, err.Error())
	}
	return nil
}

// runSyncOrAsyncCommand takes the output of a command that may have returned
// either no error, an error, or a subprocess to execute, and if a subprocess
// needs to be set on the gui object, it does so, and then returns the error
// the bool returned tells us whether the calling code should continue
func (gui *Gui) runSyncOrAsyncCommand(sub *exec.Cmd, err error) (bool, error) {
	if err != nil {
		if err != gui.Errors.ErrSubProcess {
			return false, gui.createErrorPanel(gui.g, err.Error())
		}
	}
	if sub != nil {
		gui.SubProcess = sub
		return false, gui.Errors.ErrSubProcess
	}
	return true, nil
}