// Package control runs the proxy's connection to T5DE's hub, and lets the client's T5DE settings page see and
// change it: requests to http://t5de-proxy.local/ (only the client can make them: they need the proxy's token)
// are answered here.
//
//	GET  /hub          {signedIn, hub, username, signingIn, code, page, error, choice, default, fixed, restart}
//	POST /hub/signin   starts signing in to this run's hub: opens the hub's page for the code in the browser
//	POST /hub/signout  signs this computer out
//	POST /hub/server   hub=<URL>, or empty for the install's default: the hub from the next start on (restart)
//	POST /badges       {"imvuIds": [...]} -> {"badges": [...]}: which of those IMVU accounts show the T5 badge (their
//	                   T5DE users opted in), from the hub, remembered for a while
package control

import (
	"context"
	"encoding/json"
	"errors"
	"log"
	"net/url"
	"os"
	"strings"
	"sync"
	"time"

	"git.t5de.dev/t5de/t5de-proxy/internal/hub"
	"git.t5de.dev/t5de/t5de-proxy/internal/proxy"
)

// Host is the address the client uses for the proxy itself.
const Host = "t5de-proxy.local"

// Manager keeps the hub connection running and answers the client's settings page.
type Manager struct {
	Path string // hub.json, in the hub's state folder (StateDir)
	// Hub is this run's hub (Server); Default the install's (ChannelDefault); ChoicePath where the person's
	// choice is kept. Fixed means $T5DE_HUB chose it, so the choice can't.
	Hub, Default, ChoicePath string
	Fixed                    bool
	Log                      *log.Logger
	// Attach is called with each new hub client before it runs (to connect it to the rest of the proxy).
	Attach func(c *hub.Client)
	// OpenBrowser opens a page in the person's browser.
	OpenBrowser func(page string)

	mu       sync.Mutex
	client   *hub.Client
	saved    *hub.Saved
	stop     context.CancelFunc
	username string
	signin   *signin
	badges   map[int64]badgeAnswer
}

// badgeAnswer is whether an IMVU account shows the T5 badge, as the hub said at a time.
type badgeAnswer struct {
	shows bool
	at    time.Time
}

// badgeFor is how long an answer about a badge is kept.
var badgeFor = 10 * time.Minute

// Badges is which of the IMVU accounts show the T5 badge: remembered answers, and the hub asked about the rest.
// Signed out, none do.
func (m *Manager) Badges(ctx context.Context, ids []int64) []int64 {
	m.mu.Lock()
	c := m.client
	if m.badges == nil {
		m.badges = map[int64]badgeAnswer{}
	}
	var out, ask []int64
	seen := map[int64]bool{}
	for _, id := range ids {
		if id <= 0 || seen[id] {
			continue
		}
		seen[id] = true
		if a, ok := m.badges[id]; ok && time.Since(a.at) < badgeFor {
			if a.shows {
				out = append(out, id)
			}
		} else {
			ask = append(ask, id)
		}
	}
	m.mu.Unlock()
	if c == nil || len(ask) == 0 {
		return out
	}
	for len(ask) > 0 {
		batch := ask[:min(len(ask), 200)]
		ask = ask[len(batch):]
		var r struct {
			Badges []int64 `json:"badges"`
		}
		if err := c.Call(ctx, "POST", "/api/v1/badges", map[string]any{"imvuIds": batch}, &r); err != nil {
			m.Log.Printf("hub: badges: %v", err)
			return out
		}
		shows := map[int64]bool{}
		for _, id := range r.Badges {
			shows[id] = true
		}
		now := time.Now()
		m.mu.Lock()
		for _, id := range batch {
			m.badges[id] = badgeAnswer{shows[id], now}
			if shows[id] {
				out = append(out, id)
			}
		}
		m.mu.Unlock()
	}
	return out
}

type signin struct {
	code, page, err string
	running         bool
	cancel          context.CancelFunc
}

// Start connects to the hub if the proxy is signed in.
func (m *Manager) Start() {
	saved, err := hub.Load(m.Path)
	if err != nil {
		if !errors.Is(err, hub.ErrSignedOut) {
			m.Log.Printf("hub: %v", err)
		}
		return
	}
	if saved.URL != m.Hub {
		// Signed in to another hub (by an older proxy, before hubs had their own folders): not this run's.
		m.Log.Printf("hub: the sign-in is for %s, not %s; signed out", saved.URL, m.Hub)
		return
	}
	m.run(saved)
}

func (m *Manager) run(saved *hub.Saved) {
	c := hub.New(m.Path, saved, m.Log)
	if m.Attach != nil {
		m.Attach(c)
	}
	ctx, cancel := context.WithCancel(context.Background())
	m.mu.Lock()
	if m.stop != nil {
		m.stop()
	}
	m.client, m.saved, m.stop, m.username = c, saved, cancel, ""
	m.mu.Unlock()
	go c.Run(ctx)
	go m.lookUpName(ctx, c)
}

func (m *Manager) lookUpName(ctx context.Context, c *hub.Client) {
	var me struct {
		Person struct {
			Username string `json:"username"`
		} `json:"person"`
	}
	if err := c.Call(ctx, "GET", "/api/v1/me", nil, &me); err != nil {
		return
	}
	m.mu.Lock()
	if m.client == c {
		m.username = me.Person.Username
	}
	m.mu.Unlock()
}

type status struct {
	SignedIn  bool   `json:"signedIn"`
	Hub       string `json:"hub"`
	Username  string `json:"username"`
	SigningIn bool   `json:"signingIn"`
	Code      string `json:"code"`
	Page      string `json:"page"`
	Error     string `json:"error"`
	Choice    string `json:"choice"`  // the hub chosen for the next start, "" for the default
	Default   string `json:"default"` // the install's
	Fixed     bool   `json:"fixed"`   // chosen by $T5DE_HUB
	Restart   bool   `json:"restart"` // the next start's hub isn't this run's
}

func (m *Manager) status() status {
	m.mu.Lock()
	defer m.mu.Unlock()
	s := status{Hub: m.Hub, Default: m.Default, Fixed: m.Fixed, Choice: LoadChoice(m.ChoicePath)}
	next := s.Choice
	if next == "" {
		next = m.Default
	}
	s.Restart = !m.Fixed && next != m.Hub
	if m.saved != nil {
		s.SignedIn, s.Username = true, m.username
	}
	if si := m.signin; si != nil {
		s.SigningIn, s.Code, s.Page, s.Error = si.running, si.code, si.page, si.err
	}
	return s
}

// SignIn starts signing in to this run's hub; the code to enter shows in the status, and the browser opens the
// page.
func (m *Manager) SignIn() {
	hubURL := m.Hub
	ctx, cancel := context.WithCancel(context.Background())
	si := &signin{running: true, cancel: cancel}
	m.mu.Lock()
	if m.signin != nil && m.signin.running {
		m.signin.cancel()
	}
	m.signin = si
	m.mu.Unlock()
	go func() {
		saved, err := hub.SignIn(ctx, hubURL, func(code, page string) {
			m.mu.Lock()
			si.code, si.page = code, page
			m.mu.Unlock()
			if m.OpenBrowser != nil {
				m.OpenBrowser(page)
			}
		})
		if err == nil {
			err = saved.Save(m.Path)
		}
		m.mu.Lock()
		si.running = false
		if err != nil {
			si.err = err.Error()
		}
		m.mu.Unlock()
		if err != nil {
			m.Log.Printf("hub: signing in: %v", err)
			return
		}
		m.Log.Printf("hub: signed in to %s", saved.URL)
		m.run(saved)
	}()
}

// SignOut ends this computer's sign-in: the session on the hub, the saved sign-in, and the connection.
func (m *Manager) SignOut() {
	m.mu.Lock()
	c, stop := m.client, m.stop
	m.client, m.saved, m.stop, m.username, m.signin, m.badges = nil, nil, nil, "", nil, nil
	m.mu.Unlock()
	if c != nil {
		c.Call(context.Background(), "POST", "/api/auth/sign-out", map[string]any{}, nil)
	}
	if stop != nil {
		stop()
	}
	if err := os.Remove(m.Path); err != nil && !errors.Is(err, os.ErrNotExist) {
		m.Log.Printf("hub: signing out: %v", err)
	}
	m.Log.Printf("hub: signed out")
}

// Intercept implements proxy.Interceptor: it answers requests to Host.
func (m *Manager) Intercept(x *proxy.Exchange) error {
	if !strings.EqualFold(x.URL.Hostname(), Host) {
		return nil
	}
	method := x.Request.Method
	switch {
	case x.URL.Path == "/hub" && method == "GET":
	case x.URL.Path == "/hub/signin" && method == "POST":
		m.SignIn()
	case x.URL.Path == "/hub/server" && method == "POST":
		form, _ := url.ParseQuery(string(x.Body))
		hub := form.Get("hub")
		if hub != "" {
			var err error
			if hub, err = CheckHub(hub); err != nil {
				b, _ := json.Marshal(map[string]string{"error": err.Error()})
				x.Response = proxy.LocalResponse(400, "application/json", b)
				return nil
			}
		}
		if hub == m.Default {
			hub = "" // the default stays the default, should it change
		}
		if err := SaveChoice(m.ChoicePath, hub); err != nil {
			m.Log.Printf("hub: saving the choice: %v", err)
		}
	case x.URL.Path == "/hub/signout" && method == "POST":
		m.SignOut()
	case x.URL.Path == "/badges" && method == "POST":
		var req struct {
			IDs []int64 `json:"imvuIds"`
		}
		if json.Unmarshal(x.Body, &req) != nil || len(req.IDs) > 1000 {
			x.Response = proxy.LocalResponse(400, "application/json", []byte(`{"error":"imvuIds: up to 1000 IMVU account IDs"}`))
			return nil
		}
		ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
		defer cancel()
		badges := m.Badges(ctx, req.IDs)
		if badges == nil {
			badges = []int64{}
		}
		b, _ := json.Marshal(map[string]any{"badges": badges})
		x.Response = proxy.LocalResponse(200, "application/json", b)
		return nil
	default:
		x.Response = proxy.LocalResponse(404, "application/json", []byte(`{"error":"not found"}`))
		return nil
	}
	b, _ := json.Marshal(m.status())
	x.Response = proxy.LocalResponse(200, "application/json", b)
	return nil
}