package app

import (
	"context"
	"errors"
	"fmt"

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

type IntentKind int

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

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 Result struct {
	Snapshot Snapshot
	Notice   string
	Err      error
}

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

type Application struct {
	store       profile.Store
	state       profile.State
	targets     []target.Target
	inspections map[string]target.Inspection
}

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

func NewWithTargets(store profile.Store, targets []target.Target) (*Application, error) {
	state, err := store.Load()
	if err != nil {
		return nil, err
	}
	a := &Application{store: store, state: state, targets: append([]target.Target(nil), targets...), inspections: make(map[string]target.Inspection)}
	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 := adapter.Availability(context.Background())
		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 {
	if intent.Kind == SetTargetDesired {
		return a.setTargetDesired(intent)
	}
	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 ActivateProfile:
			current, notice, mutationErr = activate(current, intent.Name)
		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.refreshTargets()
	} 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) 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.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")}
	}
	result := selected.SetDesired(context.Background(), intent.Enabled, active)
	a.inspections[selected.ID()] = result.Inspection
	notice := ""
	if result.Err == nil {
		notice = fmt.Sprintf("%s Target is now %s", selected.Description().Name, result.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
}