package server

import (
	"errors"
	"fmt"
	"html/template"
	"net/http"
	"net/url"
	"sort"
	"strings"
	"time"

	"cc.tiredsysadmin.keeporg/internal/store"
	"cc.tiredsysadmin.keeporg/internal/totp"
)

// The settings page at /web/account: who you are, how you sign in, and every
// device and browser signed in as you, each of which can be signed out from
// here. The rules are the functions in account.go, shared with the API.

// webAccount is what the settings page shows.
type webAccount struct {
	Username    string
	Email       string
	ServerAdmin bool
	Since       string
	Groups      []webMembership
	HasPassword bool
	SSO         string // the identity provider's host, when linked
	TOTPOn      bool
	// TOTPKey and TOTPLink are set while an enrolment awaits its first code.
	TOTPKey  string
	TOTPLink template.URL
	Sessions []webSessionRow
	// SSOLink starts linking single sign-on to this account, when the
	// server has a provider and the account is not linked yet.
	SSOLink string
}

type webMembership struct {
	Name string
	Role string
}

type webSessionRow struct {
	ID       string
	Label    string
	Browser  bool
	Current  bool
	Created  string
	LastSeen string
	Expires  string
}

func (s *Server) accountView(sess *webSession) webAccount {
	var v webAccount
	s.st.Read(func(st *store.State) {
		u := st.Users[sess.user.ID]
		if u == nil {
			return
		}
		v = webAccount{
			Username: u.Username, Email: u.Email, ServerAdmin: u.ServerAdmin,
			Since:       u.CreatedAt.UTC().Format("2006-01-02"),
			HasPassword: u.PassHash != "", TOTPOn: u.TOTPConfirmed,
		}
		if s.oidc != nil && u.OIDCSubject == "" && !u.Disabled {
			v.SSOLink = "/oidc/login?link=1&csrf=" + url.QueryEscape(sess.csrf)
		}
		if u.OIDCIssuer != "" {
			v.SSO = u.OIDCIssuer
			if iss, err := url.Parse(u.OIDCIssuer); err == nil && iss.Host != "" {
				v.SSO = iss.Host
			}
		}
		if u.TOTPSecret != "" && !u.TOTPConfirmed {
			v.TOTPKey = groupKey(u.TOTPSecret)
			// The otpauth: scheme is what authenticator apps register for;
			// html/template would neutralise it, and the URI is built here
			// from our own values.
			v.TOTPLink = template.URL(totp.URI("KeepOrg", u.Username, u.TOTPSecret))
		}
		for _, m := range st.Memberships {
			if m.UserID != u.ID {
				continue
			}
			if g := st.Groups[m.GroupID]; g != nil {
				v.Groups = append(v.Groups, webMembership{Name: g.Name, Role: string(m.Role)})
			}
		}
		sort.Slice(v.Groups, func(i, j int) bool { return v.Groups[i].Name < v.Groups[j].Name })
		for _, sv := range sessionsOf(st, u.ID, sess.token) {
			v.Sessions = append(v.Sessions, webSessionRow{
				ID: sv.ID, Label: sv.Label, Browser: sv.Browser, Current: sv.Current,
				Created:  sv.CreatedAt.UTC().Format("2006-01-02 15:04 UTC"),
				LastSeen: ago(sv.LastSeenAt),
				Expires:  sv.ExpiresAt.UTC().Format("2006-01-02"),
			})
		}
	})
	return v
}

// groupKey spaces a base32 secret in fours, for typing into an app by hand.
func groupKey(k string) string {
	var b strings.Builder
	for i, r := range k {
		if i > 0 && i%4 == 0 {
			b.WriteByte(' ')
		}
		b.WriteRune(r)
	}
	return b.String()
}

// ago says how long ago t was, coarsely.
func ago(t time.Time) string {
	d := time.Since(t)
	switch {
	case d < 2*time.Minute:
		return "just now"
	case d < time.Hour:
		return fmt.Sprintf("%d minutes ago", int(d.Minutes()))
	case d < 2*time.Hour:
		return "an hour ago"
	case d < 24*time.Hour:
		return fmt.Sprintf("%d hours ago", int(d.Hours()))
	case d < 48*time.Hour:
		return "yesterday"
	case d < 30*24*time.Hour:
		return fmt.Sprintf("%d days ago", int(d.Hours()/24))
	}
	return t.UTC().Format("2006-01-02")
}

func (s *Server) handleWebAccount(w http.ResponseWriter, r *http.Request, sess *webSession) {
	s.renderAccount(w, sess, "", "")
}

// handleWebAccountAction applies one control of the settings page.
func (s *Server) handleWebAccountAction(w http.ResponseWriter, r *http.Request, sess *webSession) {
	var notice string
	// Changes that need the password and code are proven outside the
	// store's lock, then applied inside it.
	switch r.FormValue("action") {
	case "password", "totp-begin", "totp-disable":
		err := s.accountReconfirmed(r, sess, &notice)
		s.finishAccountAction(w, r, sess, err, notice)
		return
	}
	err := s.st.Update(func(st *store.State) error {
		switch r.FormValue("action") {
		case "revoke":
			if err := revokeSession(st, sess.user.ID, r.FormValue("session")); err != nil {
				return err
			}
			notice = "That device is signed out. It has to sign in again to sync."
		case "revoke-others":
			n := revokeOtherSessions(st, sess.user.ID, sess.token)
			notice = fmt.Sprintf("Signed out %d other %s.", n, plural(n, "session", "sessions"))
		case "totp-confirm":
			if err := confirmTOTP(st, sess.user.ID, r.FormValue("code")); err != nil {
				return err
			}
			notice = "Two-factor authentication is on. Signing in now asks for a one-time code."
		case "totp-cancel":
			cancelTOTP(st, sess.user.ID)
			notice = "Setup cancelled. Nothing changed."
		default:
			return errBadAction
		}
		return nil
	})
	s.finishAccountAction(w, r, sess, err, notice)
}

// accountReconfirmed applies the settings changes that need the password,
// and the one-time code when one is on.
func (s *Server) accountReconfirmed(r *http.Request, sess *webSession, notice *string) error {
	switch r.FormValue("action") {
	case "password":
		next := r.FormValue("new_password")
		if next != r.FormValue("new_password2") {
			return errors.New("the two new passwords do not match")
		}
		if err := s.changePassword(r, sess.user, r.FormValue("current_password"),
			r.FormValue("totp"), next, sess.token); err != nil {
			return err
		}
		*notice = "Password changed. Your other sessions were signed out."
	case "totp-begin":
		if err := s.reconfirm(r, sess.user, r.FormValue("password"), r.FormValue("totp"),
			func(st *store.State, u *store.User) error { _, err := beginTOTP(st, u.ID); return err }); err != nil {
			return err
		}
		*notice = "Add the key below to your authenticator app, then enter the code it shows."
	case "totp-disable":
		if err := s.reconfirm(r, sess.user, r.FormValue("password"), r.FormValue("totp"),
			func(st *store.State, u *store.User) error { return disableTOTP(st, u.ID) }); err != nil {
			return err
		}
		*notice = "Two-factor authentication is off."
	}
	return nil
}

func (s *Server) finishAccountAction(w http.ResponseWriter, r *http.Request, sess *webSession, err error, notice string) {
	if err != nil {
		s.renderAccount(w, sess, accountError(err), "")
		return
	}
	// Signing out one's own browser from the list ends this session too.
	if s.webUser(r) == nil {
		s.setWebCookie(w, "", -time.Second)
		http.Redirect(w, r, "/web", http.StatusFound)
		return
	}
	s.renderAccount(w, sess, "", notice)
}

func accountError(err error) string {
	var throttled *errThrottled
	switch {
	case errors.As(err, &throttled):
		return throttled.Error()
	case errors.Is(err, errReauth), errors.Is(err, errTOTPRequired):
		return "Confirm with your password and your current one-time code."
	case errors.Is(err, errTOTPInvalid):
		return "That one-time code was rejected. Check the clock on the device that shows it."
	case errors.Is(err, errBadCredentials):
		return "The password or the one-time code is wrong."
	case errors.Is(err, errNoSuchSession):
		return "That session is already signed out."
	}
	return humanError(err)
}

func plural(n int, one, many string) string {
	if n == 1 {
		return one
	}
	return many
}

func (s *Server) renderAccount(w http.ResponseWriter, sess *webSession, errMsg, notice string) {
	d := s.shell(sess, "Account", "Account")
	d["A"], d["Error"], d["Notice"] = s.accountView(sess), errMsg, notice
	render(w, accountTmpl, d)
}

var accountTmpl = template.Must(template.Must(pages.Clone()).Parse(`
{{define "body"}}
<h1>Account</h1>
<p class="sub">How you sign in, and everywhere you are signed in.</p>
{{if .Error}}<p class="err">{{.Error}}</p>{{end}}
{{if .Notice}}<p class="ok">{{.Notice}}</p>{{end}}
{{with .A}}
<fieldset><legend>You</legend>
<table><tbody>
<tr><th>Username</th><td class="name">{{.Username}}</td></tr>
{{if .Email}}<tr><th>Email</th><td>{{.Email}}</td></tr>{{end}}
<tr><th>Signs in with</th><td>
  {{if .HasPassword}}<span class="tag">password</span>{{end}}
  {{if .TOTPOn}}<span class="tag">one-time code</span>{{end}}
  {{if .SSO}}<span class="tag">single sign-on</span> <small>via {{.SSO}}</small>{{end}}
  {{if .SSOLink}}<br><a href="{{.SSOLink}}">Link single sign-on to this account</a>{{end}}
</td></tr>
<tr><th>Role</th><td>{{if .ServerAdmin}}server administrator{{else}}member{{end}}</td></tr>
<tr><th>Groups</th><td>{{range $i, $g := .Groups}}{{if $i}}, {{end}}{{$g.Name}} <small>({{$g.Role}})</small>{{else}}none{{end}}</td></tr>
<tr><th>Member since</th><td>{{.Since}}</td></tr>
</tbody></table>
</fieldset>

<fieldset><legend>Signed-in devices</legend>
<p class="sub">Every browser and KeepOrg client signed in as you. Signing one out
stops it syncing at once; it has to sign in again.</p>
<div class="scroll"><table>
<thead><tr><th>Device</th><th>Last active</th><th>Signed in</th><th>Expires</th><th></th></tr></thead>
<tbody>
{{range .Sessions}}<tr>
  <td class="name">{{if .Label}}{{.Label}}{{else}}unnamed{{end}}<br>
    <span class="tag">{{if .Browser}}browser{{else}}app{{end}}</span>
    {{if .Current}}<span class="tag">this browser</span>{{end}}</td>
  <td>{{.LastSeen}}</td>
  <td>{{.Created}}</td>
  <td>{{.Expires}}</td>
  <td>{{if not .Current}}<form method="post" action="/web/account">
    <input type="hidden" name="csrf" value="{{$.CSRF}}">
    <input type="hidden" name="action" value="revoke">
    <input type="hidden" name="session" value="{{.ID}}">
    <button class="danger" type="submit">Sign out</button>
  </form>{{end}}</td>
</tr>{{end}}
</tbody></table></div>
{{if gt (len .Sessions) 1}}
<form method="post" action="/web/account">
<input type="hidden" name="csrf" value="{{$.CSRF}}">
<input type="hidden" name="action" value="revoke-others">
<button class="destroy" type="submit">Sign out every other device</button>
</form>
{{end}}
</fieldset>

{{if .HasPassword}}
<fieldset><legend>Two-factor authentication</legend>
{{if .TOTPOn}}
<p class="sub">On. Signing in with your password also asks for a one-time code
from your authenticator app.</p>
<form method="post" action="/web/account">
<input type="hidden" name="csrf" value="{{$.CSRF}}">
<div class="inline">
<div><label for="tf_password">Password</label>
<input id="tf_password" name="password" type="password" autocomplete="current-password" required></div>
<div><label for="tf_totp">Current one-time code</label>
<input id="tf_totp" name="totp" inputmode="numeric" autocomplete="one-time-code" required></div>
</div>
<div class="inline">
<button type="submit" name="action" value="totp-begin">Move to a new authenticator</button>
<button class="destroy" type="submit" name="action" value="totp-disable">Turn off</button>
</div>
</form>
{{else if .TOTPKey}}
<p class="sub">Add this key to an authenticator app such as Aegis, 2FAS or
Google Authenticator, then enter the six-digit code it shows.</p>
<p><code>{{.TOTPKey}}</code></p>
<p><a href="{{.TOTPLink}}">Open in an authenticator app on this device</a></p>
<form method="post" action="/web/account">
<input type="hidden" name="csrf" value="{{$.CSRF}}">
<input type="hidden" name="action" value="totp-confirm">
<label for="code">Code from the app</label>
<input id="code" name="code" inputmode="numeric" autocomplete="one-time-code" required>
<button type="submit">Turn on</button>
</form>
<form method="post" action="/web/account">
<input type="hidden" name="csrf" value="{{$.CSRF}}">
<input type="hidden" name="action" value="totp-cancel">
<button class="secondary" type="submit">Cancel</button>
</form>
{{else}}
<p class="sub">Off. With it on, a stolen password is not enough to sign in:
each sign-in also needs a code from an app on your phone.</p>
<form method="post" action="/web/account">
<input type="hidden" name="csrf" value="{{$.CSRF}}">
<input type="hidden" name="action" value="totp-begin">
<label for="tb_password">Your password</label>
<input id="tb_password" name="password" type="password" autocomplete="current-password" required>
<button type="submit">Set up two-factor authentication</button>
</form>
{{end}}
</fieldset>

<fieldset><legend>Password</legend>
<p class="sub">The password you sign in with, not any vault's password.
Changing it signs out your other devices.</p>
<form method="post" action="/web/account">
<input type="hidden" name="csrf" value="{{$.CSRF}}">
<input type="hidden" name="action" value="password">
<label for="current_password">Current password</label>
<input id="current_password" name="current_password" type="password" autocomplete="current-password" required>
{{if .TOTPOn}}<label for="cp_totp">One-time code</label>
<input id="cp_totp" name="totp" inputmode="numeric" autocomplete="one-time-code" required>{{end}}
<label for="new_password">New password</label>
<input id="new_password" name="new_password" type="password" autocomplete="new-password" minlength="10" required>
<label for="new_password2">Repeat new password</label>
<input id="new_password2" name="new_password2" type="password" autocomplete="new-password" minlength="10" required>
<button type="submit">Change password</button>
</form>
</fieldset>
{{else}}
<p class="note">You sign in through single sign-on{{if .SSO}} at {{.SSO}}{{end}},
so your password and second factor are managed there, not here.</p>
{{end}}
{{end}}
{{end}}`))