package app

import (
	"context"
	"errors"
	"fmt"
	"strings"
	"time"

	"proxyctl/internal/profile"
	"proxyctl/internal/target"
)

type IntentKind int

const (
	CreateProfile IntentKind = iota + 1
	UpdateProfile
	DeleteProfile
	ActivateProfile
	SetTargetDesired
	RefreshTargets
)

type Intent struct {
	Kind     IntentKind
	Name     string
	Profile  profile.Profile
	Confirm  bool
	TargetID string
	Enabled  bool
}

type TargetSnapshot struct {
	ID                   string
	Description          target.Description
	Available            bool
	AvailabilityEvidence string
	State                target.State
	Evidence             string
}

type Snapshot struct {
	Profiles      []profile.Profile
	ActiveProfile string
	Targets       []TargetSnapshot
}

type TargetProgress struct {
	TargetID string
	Applying bool
	State    target.State
	Evidence string
	Err      error
}

type Result struct {
	Snapshot     Snapshot
	Notice       string
	Confirmation string
	Progress     []TargetProgress
	Complete     bool
	Err          error
}

type Module interface {
	Snapshot() Snapshot
	Dispatch(Intent) Result
}

// ProgressiveModule is implemented by Applications that can expose each
// coordinated Target update while an Active Profile transition is running.
// The final Result has Complete set and closes the stream.
type ProgressiveModule interface {
	DispatchProgress(Intent) <-chan Result
}

type Application struct {
	store          profile.Store
	state          profile.State
	targets        []target.Target
	availabilities map[string]target.Availability
	inspections    map[string]target.Inspection
	mutationLock   MutationLock
	logger         OperationLogger
}

func New(store profile.Store) (*Application, error) {
	return NewWithTargets(store, nil)
}

func NewWithTargets(store profile.Store, targets []target.Target) (*Application, error) {
	return NewWithTargetsAndLock(store, targets, nil)
}

// NewWithTargetsAndLock configures the cross-process lock used by every
// Profile or Target mutation. A nil lock is intended only for isolated tests.
func NewWithTargetsAndLock(store profile.Store, targets []target.Target, mutationLock MutationLock) (*Application, error) {
	return NewWithTargetsAndRuntime(store, targets, mutationLock, nil)
}

// NewWithTargetsAndRuntime configures shared mutation serialization and local
// operation diagnostics for production callers.
func NewWithTargetsAndRuntime(store profile.Store, targets []target.Target, mutationLock MutationLock, logger OperationLogger) (*Application, error) {
	state, err := store.Load()
	if err != nil {
		return nil, err
	}
	a := &Application{
		store:          store,
		state:          state,
		targets:        append([]target.Target(nil), targets...),
		availabilities: make(map[string]target.Availability),
		inspections:    make(map[string]target.Inspection),
		mutationLock:   mutationLock,
		logger:         logger,
	}
	a.refreshTargets()
	return a, nil
}

func (a *Application) Snapshot() Snapshot {
	profiles := append([]profile.Profile(nil), a.state.Profiles...)
	snapshot := Snapshot{Profiles: profiles, ActiveProfile: a.state.ActiveProfile}
	for _, adapter := range a.targets {
		availability := a.availabilities[adapter.ID()]
		inspection := a.inspections[adapter.ID()]
		snapshot.Targets = append(snapshot.Targets, TargetSnapshot{ID: adapter.ID(), Description: adapter.Description(), Available: availability.Available, AvailabilityEvidence: availability.Evidence, State: inspection.State, Evidence: inspection.Evidence})
	}
	return snapshot
}

func (a *Application) Dispatch(intent Intent) Result {
	return a.dispatch(intent, nil)
}

func (a *Application) DispatchProgress(intent Intent) <-chan Result {
	results := make(chan Result, 2*len(a.targets)+1)
	go func() {
		defer close(results)
		final := a.dispatch(intent, func(update Result) { results <- update })
		final.Complete = true
		results <- final
	}()
	return results
}

func (a *Application) dispatch(intent Intent, publish func(Result)) Result {
	if a.mutationLock != nil {
		unlock, err := a.mutationLock.Lock(context.Background())
		if err != nil {
			return Result{Snapshot: a.Snapshot(), Err: fmt.Errorf("lock proxyctl mutation: %w", err)}
		}
		defer unlock()
	}
	if intent.Kind == SetTargetDesired {
		return a.setTargetDesired(intent)
	}
	if intent.Kind == RefreshTargets {
		a.refreshTargets()
		return Result{Snapshot: a.Snapshot(), Notice: "Refreshed Target availability and state"}
	}
	if intent.Kind == ActivateProfile {
		return a.activateProfile(intent, publish)
	}
	var notice string
	next, err := a.store.Mutate(func(current profile.State) (profile.State, error) {
		var mutationErr error
		switch intent.Kind {
		case CreateProfile:
			current, notice, mutationErr = create(current, intent.Profile)
		case UpdateProfile:
			current, notice, mutationErr = update(current, intent.Name, intent.Profile)
		case DeleteProfile:
			current, notice, mutationErr = deleteProfile(current, intent.Name, intent.Confirm)
		default:
			mutationErr = errors.New("unsupported Profile action")
		}
		return current, mutationErr
	})
	if err == nil {
		a.state = next
		a.refreshInspections()
	} else {
		var committed *profile.CommitError
		if errors.As(err, &committed) {
			// Rename committed next before directory durability reporting failed.
			// Prefer that state even if the required verification reload also fails.
			a.state = next
			reloaded, loadErr := a.store.Load()
			if loadErr != nil {
				err = errors.Join(err, fmt.Errorf("reload committed Profile configuration: %w", loadErr))
			} else {
				a.state = reloaded
			}
		}
	}
	return Result{Snapshot: a.Snapshot(), Notice: notice, Err: err}
}

func (a *Application) activateProfile(intent Intent, publish func(Result)) Result {
	if index(a.state, intent.Name) < 0 {
		return Result{Snapshot: a.Snapshot(), Err: fmt.Errorf("Profile %q does not exist", intent.Name)}
	}
	if a.state.ActiveProfile == intent.Name {
		return Result{Snapshot: a.Snapshot(), Notice: fmt.Sprintf("Profile %q is already Active", intent.Name)}
	}

	var enabled []target.Target
	var warnings []string
	for _, adapter := range a.targets {
		if a.inspections[adapter.ID()].State != target.Enabled {
			continue
		}
		enabled = append(enabled, adapter)
		if warning := adapter.Confirmation(true); warning != "" {
			warnings = append(warnings, adapter.Description().Name+": "+warning)
		}
	}
	if len(warnings) > 0 && !intent.Confirm {
		return Result{Snapshot: a.Snapshot(), Confirmation: "Changing the Active Profile requires confirmation:\n" + strings.Join(warnings, "\n")}
	}

	next, err := a.store.Mutate(func(current profile.State) (profile.State, error) {
		next, _, mutationErr := activate(current, intent.Name)
		return next, mutationErr
	})
	if err != nil {
		var committed *profile.CommitError
		if errors.As(err, &committed) {
			a.state = next
			if reloaded, loadErr := a.store.Load(); loadErr != nil {
				err = errors.Join(err, fmt.Errorf("reload committed Profile configuration: %w", loadErr))
			} else {
				a.state = reloaded
			}
		}
		return Result{Snapshot: a.Snapshot(), Err: err}
	}
	a.state = next
	active := a.activeProfile()
	// The Active Profile has changed before any Target write begins. Re-inspect
	// immediately so rows not yet updated are truthfully Drifted rather than
	// appearing Enabled against stale managed values.
	for _, adapter := range a.targets {
		a.inspections[adapter.ID()] = adapter.Inspect(context.Background(), active)
	}
	var progress []TargetProgress
	var failures []error
	for _, adapter := range enabled {
		if publish != nil {
			publish(Result{Snapshot: a.Snapshot(), Progress: []TargetProgress{{TargetID: adapter.ID(), Applying: true, State: a.inspections[adapter.ID()].State}}, Notice: "Updating " + adapter.Description().Name + " Target"})
		}
		operation := adapter.SetDesired(context.Background(), true, active)
		inspection := operation.Inspection
		var safeErr error
		if operation.Err != nil {
			// A failure-returned inspection may predate a partial write. Always
			// inspect explicitly against the new Active Profile before publishing.
			inspection = adapter.Inspect(context.Background(), active)
			safeErr = fmt.Errorf("%s (fresh inspection: %s — %s)", profile.RedactText(operation.Err.Error()), inspection.State, profile.RedactText(inspection.Evidence))
		}
		a.inspections[adapter.ID()] = inspection
		item := TargetProgress{TargetID: adapter.ID(), State: inspection.State, Evidence: inspection.Evidence, Err: safeErr}
		progress = append(progress, item)
		if publish != nil {
			publish(Result{Snapshot: a.Snapshot(), Progress: []TargetProgress{item}, Notice: adapter.Description().Name + " Target update completed", Err: safeErr})
		}
		if a.logger != nil {
			outcome, detail := "success", inspection.Evidence
			if safeErr != nil {
				outcome, detail = "failure", safeErr.Error()
			}
			_ = a.logger.Write(LogEntry{Time: time.Now(), Operation: "switch-Active-Profile", Target: adapter.ID(), Result: outcome, Detail: RedactLogDetail(detail)})
		}
		if safeErr != nil {
			failures = append(failures, fmt.Errorf("%s Target: %w", adapter.Description().Name, safeErr))
		}
	}
	// Re-inspect Targets which were not part of the transition so any managed
	// configuration is interpreted against the new Active Profile as well.
	updated := make(map[string]bool, len(enabled))
	for _, adapter := range enabled {
		updated[adapter.ID()] = true
	}
	for _, adapter := range a.targets {
		if !updated[adapter.ID()] {
			a.inspections[adapter.ID()] = adapter.Inspect(context.Background(), active)
		}
	}
	result := Result{Snapshot: a.Snapshot(), Progress: progress, Notice: fmt.Sprintf("Activated Profile %q", intent.Name)}
	if len(failures) > 0 {
		result.Err = errors.Join(failures...)
		result.Notice = fmt.Sprintf("Activated Profile %q with %d Target update failure(s); successful updates were kept and no global rollback was attempted", intent.Name, len(failures))
	}
	return result
}

func (a *Application) activeProfile() *profile.Profile {
	for i := range a.state.Profiles {
		if a.state.Profiles[i].Name == a.state.ActiveProfile {
			value := a.state.Profiles[i]
			return &value
		}
	}
	return nil
}

func (a *Application) refreshTargets() {
	active := a.activeProfile()
	for _, adapter := range a.targets {
		a.availabilities[adapter.ID()] = adapter.Availability(context.Background())
		a.inspections[adapter.ID()] = adapter.Inspect(context.Background(), active)
	}
}

func (a *Application) refreshInspections() {
	active := a.activeProfile()
	for _, adapter := range a.targets {
		a.inspections[adapter.ID()] = adapter.Inspect(context.Background(), active)
	}
}

func (a *Application) setTargetDesired(intent Intent) Result {
	var selected target.Target
	for _, adapter := range a.targets {
		if adapter.ID() == intent.TargetID {
			selected = adapter
			break
		}
	}
	if selected == nil {
		return Result{Snapshot: a.Snapshot(), Err: fmt.Errorf("Target %q does not exist", intent.TargetID)}
	}
	active := a.activeProfile()
	if intent.Enabled && active == nil {
		return Result{Snapshot: a.Snapshot(), Err: errors.New("no Active Profile; open Profile management before enabling a Target")}
	}
	if warning := selected.Confirmation(intent.Enabled); warning != "" && !intent.Confirm {
		return Result{Snapshot: a.Snapshot(), Confirmation: warning}
	}
	result := selected.SetDesired(context.Background(), intent.Enabled, active)
	inspection := result.Inspection
	if result.Err != nil {
		inspection = selected.Inspect(context.Background(), active)
	}
	a.inspections[selected.ID()] = inspection
	outcome, detail := "success", inspection.Evidence
	if result.Err != nil {
		outcome, detail = "failure", result.Err.Error()
	}
	if a.logger != nil {
		operation := "disable"
		if intent.Enabled {
			operation = "enable"
		}
		_ = a.logger.Write(LogEntry{Time: time.Now(), Operation: operation, Target: selected.ID(), Result: outcome, Detail: RedactLogDetail(detail)})
	}
	notice := ""
	if result.Err == nil {
		notice = fmt.Sprintf("%s Target is now %s", selected.Description().Name, inspection.State)
	}
	return Result{Snapshot: a.Snapshot(), Notice: notice, Err: result.Err}
}

func create(state profile.State, input profile.Profile) (profile.State, string, error) {
	p, err := profile.ValidateAndNormalize(input)
	if err != nil {
		return state, "", err
	}
	if index(state, p.Name) >= 0 {
		return state, "", fmt.Errorf("a Profile named %q already exists", p.Name)
	}
	next := cloneState(state)
	next.Profiles = append(next.Profiles, p)
	return next, fmt.Sprintf("Created Profile %q", p.Name), nil
}

func activate(state profile.State, name string) (profile.State, string, error) {
	if index(state, name) < 0 {
		return state, "", fmt.Errorf("Profile %q does not exist", name)
	}
	next := cloneState(state)
	next.ActiveProfile = name
	return next, fmt.Sprintf("Activated Profile %q", name), nil
}

func update(state profile.State, originalName string, input profile.Profile) (profile.State, string, error) {
	profileIndex := index(state, originalName)
	if profileIndex < 0 {
		return state, "", fmt.Errorf("Profile %q does not exist", originalName)
	}
	p, err := profile.ValidateAndNormalize(input)
	if err != nil {
		return state, "", err
	}
	if other := index(state, p.Name); other >= 0 && other != profileIndex {
		return state, "", fmt.Errorf("a Profile named %q already exists", p.Name)
	}
	next := cloneState(state)
	next.Profiles[profileIndex] = p
	if next.ActiveProfile == originalName {
		next.ActiveProfile = p.Name
	}
	return next, fmt.Sprintf("Updated Profile %q", p.Name), nil
}

func deleteProfile(state profile.State, name string, confirm bool) (profile.State, string, error) {
	profileIndex := index(state, name)
	if profileIndex < 0 {
		return state, "", fmt.Errorf("Profile %q does not exist", name)
	}
	if len(state.Profiles) == 1 && !confirm {
		return state, "", errors.New("deleting the final Profile requires confirmation")
	}
	next := cloneState(state)
	next.Profiles = append(next.Profiles[:profileIndex], next.Profiles[profileIndex+1:]...)
	if next.ActiveProfile == name {
		next.ActiveProfile = ""
	}
	return next, fmt.Sprintf("Deleted Profile %q", name), nil
}

func index(state profile.State, name string) int {
	for i := range state.Profiles {
		if state.Profiles[i].Name == name {
			return i
		}
	}
	return -1
}

func cloneState(state profile.State) profile.State {
	state.Profiles = append([]profile.Profile(nil), state.Profiles...)
	return state
}