package api

import (
	"context"
	"database/sql"
	"errors"
	"net/http"
	"strconv"
	"strings"
	"time"

	"git.ryuvia.com/niklas/terdut-server/internal/models"
	"github.com/go-chi/chi/v5"
)

// SettingSignupMode says who may create an account. It lives in the settings
// table with the other behaviour settings, so an administrator changes it in
// the admin page rather than in a chart.
//
// Two modes, not three. A domain-restricted mode was considered and dropped:
// with no email in this server there is nothing to verify an address against,
// so it would check the domain of a string somebody typed — a speed bump
// dressed as a control.
const (
	SettingSignupMode = "signup_mode"

	SignupInviteOnly = "invite_only"
	SignupOpen       = "open"
)

// defaultSignupMode is invite-only. An install that gets a public hostname
// before anybody has thought about sign-up should not be collecting accounts
// from the internet by default.
const defaultSignupMode = SignupInviteOnly

// inviteTTL is how long a new invite link lives. Long enough to send it and be
// read tomorrow, short enough that a link in an old chat log stops working.
const inviteTTL = 7 * 24 * time.Hour

// signupMode reads the current mode, falling back to invite-only for a missing
// or unrecognised value: the failure mode of a typo in this setting should be
// the closed door, not the open one.
func signupMode(ctx context.Context, db *sql.DB) string {
	var raw string
	if err := db.QueryRowContext(ctx,
		"SELECT value FROM settings WHERE key = $1", SettingSignupMode).Scan(&raw); err != nil {
		return defaultSignupMode
	}
	if raw != SignupOpen && raw != SignupInviteOnly {
		return defaultSignupMode
	}
	return raw
}

// handleSignupInfo tells the sign-up page what it may offer, without requiring
// a session: whether open sign-up is on, and whether the invite in the URL is
// any good. A bad invite is better reported before somebody picks a password.
func handleSignupInfo(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		out := map[string]any{"mode": signupMode(r.Context(), db)}

		if token := r.URL.Query().Get("invite"); token != "" {
			inv, err := loadInvite(r.Context(), db, token)
			switch {
			case err == nil:
				out["invite_valid"] = true
				out["invite_team"] = inv.teamName
			default:
				// Deliberately one answer for expired, revoked, used up and
				// never existed. Telling a stranger which it was tells them
				// something about links they do not hold.
				out["invite_valid"] = false
			}
		}
		respond(w, http.StatusOK, out)
	}
}

type invite struct {
	id       int64
	teamID   int64
	teamName string
	role     string
}

// loadInvite resolves a raw token to a usable invite, or an error. Usable means
// it exists, has not been revoked, has not expired and has uses left.
func loadInvite(ctx context.Context, q querier, token string) (invite, error) {
	var inv invite
	err := q.QueryRowContext(ctx, `
		SELECT i.id, i.team_id, t.name, i.role
		FROM   invites i
		JOIN   teams t ON t.id = i.team_id
		WHERE  i.token_hash = $1
		  AND  i.revoked_at IS NULL
		  AND  i.expires_at > `+nowEpoch+`
		  AND  i.uses < i.max_uses`, hashToken(token)).
		Scan(&inv.id, &inv.teamID, &inv.teamName, &inv.role)
	if errors.Is(err, sql.ErrNoRows) {
		return invite{}, errInviteUnusable
	}
	return inv, err
}

var errInviteUnusable = errors.New("invite is not usable")

// handleSignup creates an account, and puts it somewhere.
//
// Rate-limited on the same limiter as login, by address: sign-up is the other
// unauthenticated endpoint that writes, and an open install without this is a
// way to fill somebody's user table.
func handleSignup(db *sql.DB, limiter *loginLimiter, publicURL string) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		addr := clientAddr(r)
		if limiter.blocked("signup:"+addr, maxSignupsPerAddr) {
			respond(w, http.StatusTooManyRequests, errResp("too many sign-ups from this address"))
			return
		}

		var req struct {
			Username string `json:"username"`
			Email    string `json:"email"`
			Password string `json:"password"`
			Invite   string `json:"invite"`
			TeamName string `json:"team_name"`
		}
		if err := decodeJSON(r, &req); err != nil {
			respond(w, http.StatusBadRequest, errResp("invalid request body"))
			return
		}
		req.Username = strings.TrimSpace(req.Username)
		req.Email = strings.TrimSpace(req.Email)
		req.TeamName = strings.TrimSpace(req.TeamName)

		if req.Username == "" || req.Email == "" {
			respond(w, http.StatusBadRequest, errResp("username and email are required"))
			return
		}
		if msg := validatePassword(req.Password); msg != "" {
			respond(w, http.StatusBadRequest, errResp(msg))
			return
		}

		mode := signupMode(r.Context(), db)
		var inv invite
		hasInvite := false
		if req.Invite != "" {
			var err error
			inv, err = loadInvite(r.Context(), db, req.Invite)
			if err != nil {
				limiter.fail("signup:" + addr)
				respond(w, http.StatusForbidden, errResp("this invite link is not usable"))
				return
			}
			hasInvite = true
		}
		if !hasInvite && mode != SignupOpen {
			// No invite and the door is shut. Not 404: the endpoint exists and
			// saying so is how somebody knows to ask for a link.
			respond(w, http.StatusForbidden,
				errResp("sign-up is invite-only on this server"))
			return
		}
		if !hasInvite && req.TeamName == "" {
			// Open sign-up with no team would create an account that sees an
			// empty queue and can be paged by nobody.
			respond(w, http.StatusBadRequest, errResp("team_name is required"))
			return
		}

		hash, err := hashPassword(req.Password)
		if err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}

		tx, err := db.BeginTx(r.Context(), nil)
		if err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		defer tx.Rollback() //nolint:errcheck

		var userID int64
		var invitedVia *int64
		if hasInvite {
			invitedVia = &inv.id
		}
		if err := tx.QueryRowContext(r.Context(), `
			INSERT INTO users (username, email, password_hash, invited_via)
			VALUES ($1, $2, $3, $4) RETURNING id`,
			req.Username, req.Email, hash, invitedVia).Scan(&userID); err != nil {
			if isUniqueViolation(err) {
				respond(w, http.StatusConflict, errResp("username or email already exists"))
				return
			}
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}

		teamID, role := inv.teamID, inv.role
		if !hasInvite {
			// Open sign-up makes a team, and its creator owns it.
			if err := tx.QueryRowContext(r.Context(),
				"INSERT INTO teams (name) VALUES ($1) RETURNING id", req.TeamName).Scan(&teamID); err != nil {
				if isUniqueViolation(err) {
					respond(w, http.StatusConflict, errResp("a team with that name already exists"))
					return
				}
				respond(w, http.StatusInternalServerError, errResp("internal error"))
				return
			}
			role = models.RoleOwner
		}

		if _, err := tx.ExecContext(r.Context(),
			"INSERT INTO team_members (team_id, user_id, role) VALUES ($1, $2, $3)",
			teamID, userID, role); err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}

		if hasInvite {
			// Counted inside the transaction, so two people redeeming the last
			// use of a link at once cannot both get in.
			res, err := tx.ExecContext(r.Context(),
				"UPDATE invites SET uses = uses + 1 WHERE id = $1 AND uses < max_uses", inv.id)
			if err != nil {
				respond(w, http.StatusInternalServerError, errResp("internal error"))
				return
			}
			if n, _ := res.RowsAffected(); n == 0 {
				respond(w, http.StatusForbidden, errResp("this invite link is not usable"))
				return
			}
		}

		if err := tx.Commit(); err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}

		// Signed in immediately: the alternative is a form that says "now go
		// and log in", which is the same credential typed twice.
		if err := startSession(w, r, db, userID, publicURL); err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		user, _ := fetchUser(r.Context(), db, userID)
		respond(w, http.StatusCreated, meResponse{User: user, HasPassword: true})
	}
}

// maxSignupsPerAddr is looser than the login limit: several people joining from
// one office share an address, and the thing being limited is account creation
// rather than password guessing.
const maxSignupsPerAddr = 10

// ---------------------------------------------------------------------------
// Invites
// ---------------------------------------------------------------------------

type inviteJSON struct {
	ID        int64     `json:"id"`
	TeamID    int64     `json:"team_id"`
	Role      string    `json:"role"`
	CreatedAt time.Time `json:"created_at"`
	ExpiresAt time.Time `json:"expires_at"`
	MaxUses   int64     `json:"max_uses"`
	Uses      int64     `json:"uses"`
	Revoked   bool      `json:"revoked"`

	// URL is the whole link, returned once when the invite is created. Like an
	// integration key, only its hash is stored.
	URL string `json:"url,omitempty"`
}

func handleListInvites(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		teamID, ok := teamParam(w, r)
		if !ok {
			return
		}
		if !requireTeamOwner(w, r, teamID) {
			return
		}

		rows, err := db.QueryContext(r.Context(), `
			SELECT id, team_id, role, created_at, expires_at, max_uses, uses, revoked_at
			FROM   invites
			WHERE  team_id = $1
			ORDER  BY id DESC`, teamID)
		if err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		defer rows.Close()

		out := []inviteJSON{}
		for rows.Next() {
			var i inviteJSON
			var created, expires int64
			var revoked *int64
			if err := rows.Scan(&i.ID, &i.TeamID, &i.Role, &created, &expires,
				&i.MaxUses, &i.Uses, &revoked); err != nil {
				respond(w, http.StatusInternalServerError, errResp("internal error"))
				return
			}
			i.CreatedAt = time.Unix(created, 0).UTC()
			i.ExpiresAt = time.Unix(expires, 0).UTC()
			i.Revoked = revoked != nil
			out = append(out, i)
		}
		if err := rows.Err(); err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		respond(w, http.StatusOK, out)
	}
}

// handleCreateInvite mints a link into this team. Owner-only, like the rest of
// a team's configuration: deciding who joins is configuring the team.
func handleCreateInvite(db *sql.DB, publicURL string) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		teamID, ok := teamParam(w, r)
		if !ok {
			return
		}
		if !requireTeamOwner(w, r, teamID) {
			return
		}

		var req struct {
			Role    string `json:"role"`
			MaxUses int64  `json:"max_uses"`
		}
		if err := decodeJSON(r, &req); err != nil {
			respond(w, http.StatusBadRequest, errResp("invalid request body"))
			return
		}
		if req.Role == "" {
			req.Role = models.RoleMember
		}
		if req.Role != models.RoleOwner && req.Role != models.RoleMember {
			respond(w, http.StatusBadRequest, errResp("role must be owner or member"))
			return
		}
		if req.MaxUses == 0 {
			req.MaxUses = 1
		}
		if req.MaxUses < 1 || req.MaxUses > 100 {
			respond(w, http.StatusBadRequest, errResp("max_uses must be between 1 and 100"))
			return
		}

		raw, hash, err := randomToken()
		if err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		caller, _ := userFromContext(r.Context())
		expires := time.Now().Add(inviteTTL)

		var out inviteJSON
		var created, expiresAt int64
		if err := db.QueryRowContext(r.Context(), `
			INSERT INTO invites (token_hash, team_id, role, created_by, expires_at, max_uses)
			VALUES ($1, $2, $3, $4, $5, $6)
			RETURNING id, team_id, role, created_at, expires_at, max_uses, uses`,
			hash, teamID, req.Role, caller.ID, expires.Unix(), req.MaxUses).
			Scan(&out.ID, &out.TeamID, &out.Role, &created, &expiresAt, &out.MaxUses, &out.Uses); err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		out.CreatedAt = time.Unix(created, 0).UTC()
		out.ExpiresAt = time.Unix(expiresAt, 0).UTC()
		out.URL = strings.TrimSuffix(publicURL, "/") + "/signup?invite=" + raw
		respond(w, http.StatusCreated, out)
	}
}

// handleRevokeInvite stops a link working without waiting for it to expire.
func handleRevokeInvite(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		teamID, ok := teamParam(w, r)
		if !ok {
			return
		}
		if !requireTeamOwner(w, r, teamID) {
			return
		}
		id, err := strconv.ParseInt(chi.URLParam(r, "inviteID"), 10, 64)
		if err != nil {
			respond(w, http.StatusBadRequest, errResp("invalid invite id"))
			return
		}

		res, err := db.ExecContext(r.Context(),
			"UPDATE invites SET revoked_at = "+nowEpoch+
				" WHERE id = $1 AND team_id = $2 AND revoked_at IS NULL", id, teamID)
		if err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		if n, _ := res.RowsAffected(); n == 0 {
			respond(w, http.StatusNotFound, errResp("not found"))
			return
		}
		w.WriteHeader(http.StatusNoContent)
	}
}

// ---------------------------------------------------------------------------
// Onboarding
// ---------------------------------------------------------------------------

// handleTestNotification publishes one push to the caller's own topic.
//
// The point of the first-run checklist's notification step is not that a topic
// string has been typed but that a phone buzzes, and only the person holding it
// can tell whether it did. Published directly rather than through the outbox:
// the outbox row requires an incident, and this deliberately belongs to no
// incident.
func handleTestNotification(cfg NotifyConfig, db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		if cfg.BaseURL == "" {
			respond(w, http.StatusServiceUnavailable,
				errResp("this server has no ntfy configured, so it can send nothing"))
			return
		}
		caller, _ := userFromContext(r.Context())

		var topic *string
		if err := db.QueryRowContext(r.Context(),
			"SELECT ntfy_topic FROM users WHERE id = $1", caller.ID).Scan(&topic); err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		if topic == nil || *topic == "" {
			respond(w, http.StatusBadRequest, errResp("set a notification topic first"))
			return
		}

		if err := publish(r.Context(), cfg, ntfyMessage{
			Topic:   *topic,
			Title:   "terdut test",
			Message: "If this arrived, your notifications work.",
			Tags:    []string{"white_check_mark"},
		}); err != nil {
			// The failure is the useful part here: a wrong topic, a token the
			// ntfy server rejects, or an ntfy that is down all look the same
			// from the phone, which is silence.
			respond(w, http.StatusBadGateway, errResp("ntfy rejected the test: "+err.Error()))
			return
		}
		w.WriteHeader(http.StatusNoContent)
	}
}

// handleDismissOnboarding hides the first-run checklist, or brings it back.
// Stored per user rather than in the browser: somebody who finishes setting up
// on a laptop should not be nagged again on their phone.
func handleDismissOnboarding(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		var req struct {
			Dismissed *bool `json:"dismissed"`
		}
		if err := decodeJSON(r, &req); err != nil || req.Dismissed == nil {
			respond(w, http.StatusBadRequest, errResp("dismissed is required"))
			return
		}
		caller, _ := userFromContext(r.Context())

		var err error
		if *req.Dismissed {
			_, err = db.ExecContext(r.Context(),
				"UPDATE users SET onboarding_dismissed_at = "+nowEpoch+" WHERE id = $1", caller.ID)
		} else {
			_, err = db.ExecContext(r.Context(),
				"UPDATE users SET onboarding_dismissed_at = NULL WHERE id = $1", caller.ID)
		}
		if err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		w.WriteHeader(http.StatusNoContent)
	}
}