package tui

import (
	"context"
	"fmt"

	tea "github.com/charmbracelet/bubbletea"

	"proxyctl/internal/app"
	"proxyctl/internal/probe"
	"proxyctl/internal/profile"
)

type page int

const (
	mainPage page = iota
	profilesPage
	formPage
)

type Model struct {
	application             app.InteractiveModule
	presentation            terminalPresentation
	snapshot                app.Snapshot
	page                    page
	width                   int
	height                  int
	selected                int
	selectedProfileName     string
	profileViewportOffset   int
	profileDetailsOffset    int
	profileDelete           *profileDeleteConfirmation
	selectedTargetID        string
	dashboardFocus          dashboardPane
	showUnavailable         bool
	detailsOffset           int
	driftResolutionTargetID string
	picker                  profilePickerState
	form                    formState
	formSequence            uint64
	help                    helpDialogState
	status                  string
	operation               operationCoordinator
	detect                  func(context.Context, string) (probe.Capabilities, error)
}

// probeDone carries only detector output and formState's opaque typed token.
// Source data and all validation/application rules remain owned by formState.
type probeDone struct {
	caps  probe.Capabilities
	err   error
	token probeToken
}

type profileDeleteConfirmation struct {
	name   string
	dialog confirmationDialog
}

func NewModel(application app.InteractiveModule, configure ...ModelOption) Model {
	options := defaultModelOptions()
	for _, option := range configure {
		option(&options)
	}
	snapshot := application.Snapshot()
	model := Model{
		application:      application,
		presentation:     terminalPresentation{theme: newSemanticTheme(options.theme, options.output)},
		snapshot:         snapshot,
		selectedTargetID: newTargetCatalog(snapshot, false, "").firstID(),
		width:            80,
		height:           24,
		operation:        newOperationCoordinator(),
		picker:           newProfilePickerState(),
		detect:           probe.Detect,
	}
	model.retainProfileSelection("", 0)
	if targetsChecking(snapshot) {
		model.startOperation(app.Intent{Kind: app.RefreshTargets})
	}
	return model
}

func targetsChecking(snapshot app.Snapshot) bool {
	for _, item := range snapshot.Targets {
		if item.DetectionPhase == app.TargetChecking {
			return true
		}
	}
	return false
}

func (m Model) Init() tea.Cmd {
	if m.operation.updates != nil {
		return waitForOperation(m.operation.updates)
	}
	return nil
}

// busy is the single-operation guard for asynchronous Application work. Every
// operation start checks it, so a completion can only belong to the one current
// operation rather than racing another operation for shared model state.
func (m Model) busy() bool { return m.operation.busy() }

func (m Model) operationInFlight() bool { return m.operation.active }

func (m Model) dashboardNavigationAvailable() bool {
	// A deferred exit rejects new work, not read-only browsing. Selection,
	// details, and Help remain useful until the current mutation is safe.
	return true
}

func (m Model) Update(message tea.Msg) (tea.Model, tea.Cmd) {
	if size, ok := message.(tea.WindowSizeMsg); ok {
		m.width = size.Width
		m.height = size.Height
		m.ensureProfileSelectionVisible()
		return m, nil
	}

	// A deferred tea.Quit is queued only after the in-flight completion has
	// been consumed. Until Bubble Tea processes that QuitMsg, keep the model
	// terminal so intervening input cannot cancel a confirmation or start a
	// second mutation.
	if m.operation.quitRequested && !m.operationInFlight() {
		return m, nil
	}
	if key, ok := message.(tea.KeyMsg); ok {
		// Ctrl+C is global. q exits only the dashboard when no dialog obscures it;
		// otherwise the top dialog or child page owns q.
		if key.String() == "ctrl+c" || (key.String() == "q" && m.dashboardQuitAvailable()) {
			return m, m.operation.requestQuit()
		}
		// Help is available from every page and dialog. Opening it explicitly
		// places it above the current dialog without changing state underneath.
		if key.String() == "?" {
			if !m.help.top(m.operation.confirmation) {
				m.help.show()
			}
			return m, nil
		}
	}
	if progress, ok := message.(operationProgress); ok {
		if !m.operation.active || progress.updates != m.operation.updates {
			return m, nil
		}
		if progress.closed {
			m.snapshot = m.application.Snapshot()
			m.retainTargetSelection()
			m.retainProfileSelection(m.selectedProfileName, m.selected)
			m.operation.unexpectedClose()
			return m, m.operation.deferredQuit()
		}
		m.snapshot = progress.update.Snapshot
		m.retainTargetSelection()
		m.retainProfileSelection(m.selectedProfileName, m.selected)
		if firstFailed := m.operation.apply(progress.update); firstFailed != "" {
			m.selectedTargetID = firstFailed
			m.detailsOffset = 0
		}
		if m.operation.confirmation != nil {
			m.page = mainPage
			if m.help.open {
				// A safety confirmation requested after Help was opened is the new
				// top dialog. Cancelling it reveals the unchanged Help beneath.
				m.help.confirmationAbove = true
			}
		}
		if progress.update.IsTerminal() {
			return m, m.operation.deferredQuit()
		}
		return m, waitForOperation(progress.updates)
	}
	if done, ok := message.(probeDone); ok {
		return m, m.form.applyProbeResult(done.token, done.caps, done.err)
	}
	key, ok := message.(tea.KeyMsg)
	if !ok {
		return m, nil
	}
	if m.help.top(m.operation.confirmation) {
		m.help.update(key.String())
		return m, nil
	}
	switch m.page {
	case mainPage:
		return m.updateMain(key)
	case profilesPage:
		return m.updateProfiles(key)
	case formPage:
		return m.updateForm(key)
	default:
		return m, nil
	}
}

func (m *Model) startOperation(intent app.Intent) tea.Cmd {
	snapshot, command, started := m.operation.start(m.application, intent)
	if started {
		m.snapshot = snapshot
		m.retainTargetSelection()
	}
	return command
}

type mutationAvailability struct {
	available     bool
	reason        string
	compactReason string
}

// targetMutationAvailability consumes the Application's structured action
// policy. It adds only Model-owned serialization state and never derives an
// action from Target state or display text.
func targetMutationAvailability(selected app.TargetSnapshot, selectedOK bool, operationBlocked bool) mutationAvailability {
	switch {
	case !selectedOK:
		return mutationAvailability{reason: "Target mutation is disabled because no Target is selected", compactReason: "no Target selected"}
	case !selected.PrimaryAction.Available:
		reason := selected.PrimaryAction.DisabledReason
		if reason == "" {
			reason = "This Target action is unavailable"
		}
		return mutationAvailability{reason: reason, compactReason: "unavailable"}
	case operationBlocked:
		return mutationAvailability{reason: "Wait for the current mutation to finish before starting another modification", compactReason: "mutation in progress"}
	default:
		return mutationAvailability{available: true}
	}
}

func driftResolutionAction(selected app.TargetSnapshot, kind app.TargetActionKind) (app.TargetAction, bool) {
	for _, action := range selected.DriftResolutionActions {
		if action.Kind == kind {
			return action, true
		}
	}
	return app.TargetAction{Kind: kind}, false
}

func (m Model) updateMain(key tea.KeyMsg) (tea.Model, tea.Cmd) {
	if m.picker.open {
		switch key.String() {
		case "esc":
			m.picker.close()
			return m, nil
		case "enter":
			selected, ok := m.picker.selected(m.snapshot)
			if !ok {
				return m, nil
			}
			m.picker.close()
			return m.beginProfileActivation(app.Intent{Kind: app.ActivateProfile, Name: selected.Name})
		default:
			return m, m.picker.update(key, m.snapshot)
		}
	}
	if m.operation.confirmation != nil {
		switch m.operation.confirmationDialog.update(key.String()) {
		case confirmationAccepted:
			confirmed, ok := m.operation.confirmedIntent()
			if !ok {
				return m, nil
			}
			m.status = ""
			return m, m.startOperation(confirmed)
		case confirmationCancelled:
			m.operation.cancelConfirmation()
		}
		return m, nil
	}
	if m.driftResolutionTargetID != "" {
		switch key.String() {
		case "enter", "esc", "n", "q":
			m.driftResolutionTargetID = ""
			return m, nil
		case "r", "o":
			kind := app.ReapplyActiveProfileAction
			if key.String() == "o" {
				kind = app.RestoreOriginalAction
			}
			selected, ok := newTargetCatalog(m.snapshot, true, m.driftResolutionTargetID).selected(m.driftResolutionTargetID)
			if !ok {
				m.driftResolutionTargetID = ""
				m.operation.status = app.OperationStatus{Kind: app.StatusBlocked, Summary: "Drift Resolution is unavailable because the Target is no longer present"}
				return m, nil
			}
			action, ok := driftResolutionAction(selected, kind)
			if !ok || !action.Available {
				reason := action.DisabledReason
				if reason == "" {
					reason = "This Drift Resolution action is unavailable"
				}
				m.operation.status = app.OperationStatus{Kind: app.StatusBlocked, Summary: reason}
				return m, nil
			}
			intent, _ := kind.Intent(selected.ID)
			m.driftResolutionTargetID = ""
			return m, m.startOperation(intent)
		}
		return m, nil
	}
	if key.String() == "e" && m.operation.currentError != nil {
		m.operation.errorExpanded = !m.operation.errorExpanded
		m.operation.errorOffset = 0
		return m, nil
	}
	if key.String() == "x" && m.operation.currentError != nil {
		m.operation.acknowledgeError()
		return m, nil
	}
	if m.operation.errorExpanded {
		switch key.String() {
		case "pgup":
			m.operation.errorOffset = max(0, m.operation.errorOffset-5)
			return m, nil
		case "pgdown":
			m.operation.errorOffset += 5
			return m, nil
		}
	}
	catalog := newTargetCatalog(m.snapshot, m.showUnavailable, m.selectedTargetID)
	switch key.String() {
	case "p":
		if m.operation.active || m.operation.quitRequested {
			m.operation.status = app.OperationStatus{Kind: app.StatusBlocked, Summary: "Wait for the current mutation to finish before changing the Active Profile"}
		} else {
			return m, m.picker.show(m.snapshot)
		}
	case "m":
		if m.operation.active || m.operation.quitRequested {
			m.operation.status = app.OperationStatus{Kind: app.StatusBlocked, Summary: "Profile management disabled: wait for the current mutation to finish"}
		} else {
			m.page = profilesPage
			m.retainProfileSelection(m.selectedProfileName, m.selected)
			m.status = ""
			if m.operation.status.Kind != app.StatusError {
				m.operation.status = app.OperationStatus{}
			}
		}
	case "r":
		if m.operation.active || m.operation.quitRequested {
			m.operation.status = app.OperationStatus{Kind: app.StatusBlocked, Summary: "Wait for the current mutation to finish before refreshing Targets"}
		} else {
			return m, m.startOperation(app.Intent{Kind: app.RefreshTargets})
		}
	case "tab":
		if m.dashboardNavigationAvailable() {
			if m.dashboardFocus == targetListPane {
				m.dashboardFocus = targetDetailsPane
			} else {
				m.dashboardFocus = targetListPane
			}
		}
	case "u":
		if m.dashboardNavigationAvailable() {
			formerIndex := catalog.index(m.selectedTargetID)
			m.showUnavailable = !m.showUnavailable
			m.selectedTargetID = newTargetCatalog(m.snapshot, m.showUnavailable, m.selectedTargetID).retain(m.selectedTargetID, formerIndex)
			m.detailsOffset = 0
		}
	case "up", "k":
		if m.dashboardNavigationAvailable() {
			if m.dashboardFocus == targetDetailsPane {
				m.detailsOffset = max(0, m.detailsOffset-1)
			} else {
				m.selectedTargetID = catalog.move(m.selectedTargetID, -1)
				m.detailsOffset = 0
			}
		}
	case "down", "j":
		if m.dashboardNavigationAvailable() {
			if m.dashboardFocus == targetDetailsPane {
				m.detailsOffset++
			} else {
				m.selectedTargetID = catalog.move(m.selectedTargetID, 1)
				m.detailsOffset = 0
			}
		}
	case "pgup":
		if m.dashboardNavigationAvailable() && m.dashboardFocus == targetDetailsPane {
			m.detailsOffset = max(0, m.detailsOffset-5)
		}
	case "pgdown":
		if m.dashboardNavigationAvailable() && m.dashboardFocus == targetDetailsPane {
			m.detailsOffset += 5
		}
	case " ":
		selected, ok := catalog.selected(m.selectedTargetID)
		availability := targetMutationAvailability(selected, ok, m.operation.active || m.operation.quitRequested)
		if !availability.available {
			m.operation.status = app.OperationStatus{Kind: app.StatusBlocked, Summary: availability.reason}
			break
		}
		if selected.PrimaryAction.Kind == app.ResolveDriftTargetAction {
			m.driftResolutionTargetID = selected.ID
			break
		}
		intent, ok := selected.PrimaryAction.Kind.Intent(selected.ID)
		if !ok {
			m.operation.status = app.OperationStatus{Kind: app.StatusBlocked, Summary: "This Target action is unavailable"}
			break
		}
		return m, m.startOperation(intent)
	}

	return m, nil
}

func (m Model) updateProfiles(key tea.KeyMsg) (tea.Model, tea.Cmd) {
	if m.profileDelete != nil {
		switch m.profileDelete.dialog.update(key.String()) {
		case confirmationAccepted:
			name := m.profileDelete.name
			m.profileDelete = nil
			m.applyProfileMutation(app.Intent{Kind: app.DeleteProfile, Name: name, Confirm: true}, "")
		case confirmationCancelled:
			m.profileDelete = nil
		}
		return m, nil
	}

	switch key.String() {
	case "q", "esc":
		m.page = mainPage
		m.status = ""
	case "up", "k":
		if m.selected > 0 {
			m.selected--
			m.selectedProfileName = m.snapshot.Profiles[m.selected].Name
			m.profileDetailsOffset = 0
			m.ensureProfileSelectionVisible()
		}
	case "down", "j":
		if m.selected+1 < len(m.snapshot.Profiles) {
			m.selected++
			m.selectedProfileName = m.snapshot.Profiles[m.selected].Name
			m.profileDetailsOffset = 0
			m.ensureProfileSelectionVisible()
		}
	case "pgup":
		m.profileDetailsOffset = max(0, m.profileDetailsOffset-5)
	case "pgdown":
		m.profileDetailsOffset += 5
	case "n":
		if !m.profileMutationAvailable("creating a Proxy Profile") {
			break
		}
		m.formSequence++
		m.form = newFormState(m.formSequence, "", profile.Profile{Mode: profile.SingleMode})
		m.page = formPage
		m.status = ""
	case "e", "enter":
		if !m.profileMutationAvailable("editing a Proxy Profile") {
			break
		}
		if selected, ok := m.selectedProfile(); ok {
			m.formSequence++
			m.form = newFormState(m.formSequence, selected.Name, selected)
			m.page = formPage
			m.status = ""
		}
	case "d":
		if !m.profileMutationAvailable("deleting a Proxy Profile") {
			break
		}
		if selected, ok := m.selectedProfile(); ok {
			m.profileDelete = newProfileDeleteConfirmation(selected, len(m.snapshot.Profiles) == 1, selected.Name == m.snapshot.ActiveProfile)
		}
	}
	return m, nil
}

func (m *Model) profileMutationAvailable(action string) bool {
	if !m.busy() {
		return true
	}
	m.operation.status = app.OperationStatus{Kind: app.StatusBlocked, Summary: "Cannot continue " + action + "; wait for the current mutation to finish"}
	return false
}

func newProfileDeleteConfirmation(selected profile.Profile, final, active bool) *profileDeleteConfirmation {
	details := []string{"The Proxy Profile will be removed permanently."}
	if active {
		details = append(details, "This is the Active Profile; deleting it leaves no Active Profile selected.")
	}
	if final {
		details = append(details,
			"This is the final Proxy Profile.",
			"Existing managed configuration remains in place.",
			"Affected Targets become Drifted.")
	}
	request := app.Confirmation{
		Title:        fmt.Sprintf("Delete Proxy Profile “%s”?", selected.Name),
		Summary:      "Deletion cannot be undone.",
		Details:      details,
		ConfirmLabel: "Delete",
		CancelLabel:  "Cancel",
		HighImpact:   true,
	}
	return &profileDeleteConfirmation{name: selected.Name, dialog: newConfirmationDialog(request)}
}

func (m Model) updateForm(key tea.KeyMsg) (tea.Model, tea.Cmd) {
	if m.form.currentField() == profile.BypassField {
		switch key.String() {
		case "pgup":
			m.form.scrollBypassPreview(-5)
			return m, nil
		case "pgdown":
			m.form.scrollBypassPreview(5)
			return m, nil
		}
	}
	if key.String() == "q" || key.Type == tea.KeyEsc {
		m.page = profilesPage
		m.status = ""
		m.form = formState{}
		return m, nil
	}
	switch key.Type {
	case tea.KeyCtrlS:
		m.form.invalidateProbe()
		m.form.syncFocusedValue()
		m.form.refreshValidation()
		if err := m.form.validation.Err(); err != nil || m.form.nameConflict(m.snapshot.Profiles) != "" {
			m.status = "Fix the highlighted Profile fields before saving"
			return m, nil
		}
		kind := app.CreateProfile
		if m.form.originalName != "" {
			kind = app.UpdateProfile
		}
		normalized := m.form.validation.Normalized
		intent := app.Intent{Kind: kind, Name: m.form.originalName, Profile: normalized}
		result := m.applyProfileMutation(intent, normalized.Name)
		if result.Err != nil {
			return m, nil
		}
		m.page = profilesPage
		m.form = formState{}
		return m, nil
	case tea.KeyCtrlD:
		address, token, started := m.form.startProbe()
		if !started {
			return m, nil
		}
		detect := m.detect
		return m, func() tea.Msg {
			caps, err := detect(context.Background(), address)
			return probeDone{caps: caps, err: err, token: token}
		}
	case tea.KeyCtrlT:
		return m, m.form.toggleMode()
	case tea.KeyTab, tea.KeyDown:
		return m, m.form.move(1)
	case tea.KeyShiftTab, tea.KeyUp:
		return m, m.form.move(-1)
	default:
		return m, m.form.updateInput(key)
	}
}

func (m Model) beginProfileActivation(intent app.Intent) (tea.Model, tea.Cmd) {
	if m.busy() {
		m.operation.status = app.OperationStatus{Kind: app.StatusBlocked, Summary: "Wait for the current mutation to finish before changing the Active Profile"}
		return m, nil
	}
	m.page = mainPage
	return m, m.startOperation(intent)
}

func (m *Model) applyProfileMutation(intent app.Intent, preferredName string) app.Result {
	formerName, formerIndex := m.selectedProfileName, m.selected
	result := m.application.Dispatch(intent)
	m.snapshot = result.Snapshot
	if preferredName == "" {
		preferredName = formerName
	}
	m.retainProfileSelection(preferredName, formerIndex)
	if result.Err != nil {
		m.status = "Error: " + result.Err.Error()
	} else {
		m.status = result.Notice
	}
	return result
}

func (m Model) selectedProfile() (profile.Profile, bool) {
	if m.selectedProfileName != "" {
		for i := range m.snapshot.Profiles {
			if m.snapshot.Profiles[i].Name == m.selectedProfileName {
				return m.snapshot.Profiles[i], true
			}
		}
	}
	return profileAt(m.snapshot, m.selected)
}

func (m *Model) retainProfileSelection(name string, fallbackIndex int) {
	if len(m.snapshot.Profiles) == 0 {
		m.selected = 0
		m.selectedProfileName = ""
		m.profileViewportOffset = 0
		m.profileDetailsOffset = 0
		return
	}
	for i := range m.snapshot.Profiles {
		if name != "" && m.snapshot.Profiles[i].Name == name {
			m.selected = i
			m.selectedProfileName = name
			m.ensureProfileSelectionVisible()
			return
		}
	}
	m.selected = min(max(0, fallbackIndex), len(m.snapshot.Profiles)-1)
	m.selectedProfileName = m.snapshot.Profiles[m.selected].Name
	m.profileDetailsOffset = 0
	m.ensureProfileSelectionVisible()
}

func (m *Model) ensureProfileSelectionVisible() {
	if len(m.snapshot.Profiles) == 0 {
		m.profileViewportOffset = 0
		return
	}
	// The details pane and footer consume variable height. A conservative
	// capacity keeps the selected identity visible without coupling Model state
	// to Lip Gloss measurements, while retaining the viewport top across resize.
	capacity := max(1, m.height/2)
	if m.selected < m.profileViewportOffset {
		m.profileViewportOffset = m.selected
	}
	if m.selected >= m.profileViewportOffset+capacity {
		m.profileViewportOffset = m.selected - capacity + 1
	}
	maximum := max(0, len(m.snapshot.Profiles)-capacity)
	m.profileViewportOffset = min(maximum, max(0, m.profileViewportOffset))
}

func (m Model) View() string {
	return m.presentation.Render(presentationState{
		snapshot:                m.snapshot,
		page:                    m.page,
		width:                   m.width,
		height:                  m.height,
		selected:                m.selected,
		profileOffset:           m.profileViewportOffset,
		profileDetails:          m.profileDetailsOffset,
		profileDelete:           m.profileDelete,
		selectedTargetID:        m.selectedTargetID,
		dashboardFocus:          m.dashboardFocus,
		showUnavailable:         m.showUnavailable,
		detailsOffset:           m.detailsOffset,
		driftResolutionTargetID: m.driftResolutionTargetID,
		picker:                  m.picker,
		form:                    m.form,
		help:                    m.help,
		confirmation:            m.operation.confirmation,
		confirmationDialog:      &m.operation.confirmationDialog,
		status:                  m.status,
		operationStatus:         m.operation.status,
		currentError:            m.operation.currentError,
		errorExpanded:           m.operation.errorExpanded,
		errorOffset:             m.operation.errorOffset,
		exitDeferred:            m.operation.quitRequested && m.operationInFlight(),
		operationActive:         m.operation.active,
		operationProgress:       m.operation.progress,
	})
}

func (m Model) availableTargets() []app.TargetSnapshot {
	return availableTargets(m.snapshot)
}

func (m *Model) retainTargetSelection() {
	catalog := newTargetCatalog(m.snapshot, m.showUnavailable, m.selectedTargetID)
	m.selectedTargetID = catalog.retain(m.selectedTargetID, catalog.index(m.selectedTargetID))
}