package classes

import (
	"context"
	"errors"
	"fmt"
	"net/http"
	"slices"
	"strconv"
	"strings"
	"time"

	"git.golem15.com/golem15/sm-user-plugin/models"
	"git.golem15.com/golem15/summercms/modules/backpack"
	"git.golem15.com/golem15/summercms/modules/bouncer"
	"gorm.io/gorm"
)

// sessionCookieNames are the cookies the plugin's "jwt" guard reads after
// the Authorization header, in the same order (plugin.go Boot).
var sessionCookieNames = []string{"token", "auth_token"}

// RequestUser returns the signed-in user of r for handlers that run without
// the jwt.auth middleware and must also serve anonymous requests (an OAuth
// provider's authorize page, for example). The token is read and checked
// exactly as the plugin's "jwt" guard does: the Authorization bearer header
// first, then the token and auth_token cookies; the plugin's JWT secret;
// the published bouncer.BlacklistStore when there is one; and the user's
// tokens_valid_after cutoff. A soft-deleted user is not returned.
//
// An anonymous request, or a token that is invalid, expired, blacklisted or
// names no user, returns (nil, nil). Only an infrastructure failure (no
// database handle, a failing query or blacklist lookup) returns an error.
func RequestUser(ctx context.Context, app *backpack.App, r *http.Request) (*models.User, error) {
	if r == nil {
		return nil, nil
	}
	raw := sessionToken(r)
	if raw == "" {
		return nil, nil
	}
	secret, err := JWTSecret(app)
	if err != nil {
		return nil, err
	}
	sub, iat, _, jti, err := bouncer.VerifyClaims(raw, secret)
	if err != nil {
		return nil, nil
	}
	id, err := strconv.ParseUint(sub, 10, 64)
	if err != nil || id == 0 {
		return nil, nil
	}
	gdb, ok := app.Lookup[*gorm.DB]()
	if !ok || gdb == nil {
		return nil, fmt.Errorf("golem15.user: gorm handle is missing")
	}
	var user models.User
	err = gdb.WithContext(ctx).Where("id = ?", uint(id)).Take(&user).Error
	if errors.Is(err, gorm.ErrRecordNotFound) {
		return nil, nil
	}
	if err != nil {
		return nil, err
	}
	if bl, ok := app.Lookup[bouncer.BlacklistStore](); ok && bl != nil {
		blocked, err := bl.IsBlacklisted(ctx, jti)
		if err != nil {
			return nil, err
		}
		if blocked {
			return nil, nil
		}
	}
	if user.TokensValidAfter != nil && iat.Before(*user.TokensValidAfter) {
		return nil, nil
	}
	return &user, nil
}

// EndSession signs the request out; POST /logout runs it. Every session JWT
// r carries (the Authorization bearer header and the token and auth_token
// cookies the "jwt" guard reads) that verifies is added to the published
// bouncer.BlacklistStore, so the guard, RequestUser and POST /refresh refuse
// it from then on. A token verifies while it is unexpired, and a token with
// the user audience also after its access lifetime while its refresh window
// is open (it could still be refreshed). The row is kept until the later of
// the token's exp and its iat plus the refresh window
// (golem15.user.jwt.refresh_ttl), plus one minute, as bouncer.Refresh keeps
// a rotated jti: a row that ended at exp would let /refresh revive the
// logged-out token for the rest of its window.
//
// When w is not nil the response gets the forget cookie of
// bouncer.LoadCookieConfig(app.Config), with the name, path, domain,
// SameSite and Secure of the token cookie a login writes, and one with the
// same attributes for each other session cookie r carries. It writes no
// status or body.
//
// It returns the subject of the token the guard would read (the bearer
// header first, then the cookies in order), or "" when r carries none or it
// does not verify. Only a failing blacklist write is an error; the cookies
// are forgotten and the other tokens revoked in any case. Without a
// published blacklist nothing is revoked.
func EndSession(ctx context.Context, app *backpack.App, w http.ResponseWriter, r *http.Request) (string, error) {
	if w != nil {
		forgetSessionCookies(app, w, r)
	}
	if r == nil || app == nil {
		return "", nil
	}
	secret, err := JWTSecret(app)
	if err != nil {
		return "", nil
	}
	bl, _ := app.Lookup[bouncer.BlacklistStore]()
	window := refreshWindow(app)
	subject := ""
	var firstErr error
	for i, raw := range sessionTokens(r) {
		sub, iat, exp, jti, ok := verifySessionToken(raw, secret, window)
		if !ok {
			continue
		}
		if i == 0 {
			subject = sub
		}
		if bl == nil {
			continue
		}
		if err := bl.Add(ctx, jti, revokedUntil(iat, exp, window), time.Now()); err != nil && firstErr == nil {
			firstErr = err
		}
	}
	return subject, firstErr
}

// EndRequestSession is the best-effort EndSession, as in the PHP provider:
// it revokes the session JWTs r carries and forgets the session cookies the
// same way, logs a blacklist failure instead of returning it, and always
// returns nil. It writes no status or body.
func EndRequestSession(ctx context.Context, app *backpack.App, w http.ResponseWriter, r *http.Request) error {
	if _, err := EndSession(ctx, app, w, r); err != nil {
		pluginLog.Warn("golem15.user: end session: blacklist token", "err", err)
	}
	return nil
}

// forgetSessionCookies expires the token cookie of
// bouncer.LoadCookieConfig(app.Config) and, with the same path, domain,
// SameSite and Secure, each other session cookie r carries.
func forgetSessionCookies(app *backpack.App, w http.ResponseWriter, r *http.Request) {
	cfg := bouncer.CookieConfig{Name: bouncer.DefaultCookieName, Path: "/", SameSite: http.SameSiteLaxMode}
	if app != nil && app.Config != nil {
		loaded, err := bouncer.LoadCookieConfig(app.Config)
		if err != nil {
			pluginLog.Warn("golem15.user: end session: cookie config", "err", err)
		} else {
			cfg = loaded
		}
	}
	http.SetCookie(w, cfg.ForgetTokenCookie())
	if r == nil {
		return
	}
	for _, name := range sessionCookieNames {
		if name == cfg.Name {
			continue
		}
		if _, err := r.Cookie(name); err != nil {
			continue
		}
		other := cfg
		other.Name = name
		http.SetCookie(w, other.ForgetTokenCookie())
	}
}

// verifySessionToken accepts raw when it is a token the "jwt" guard accepts
// or POST /refresh still rotates: a user-audience token whose refresh window
// is open (its exp may have passed), or an unexpired token, which also
// covers one without an audience (issued by the PHP backend). A token
// without a jti cannot be revoked and is refused.
func verifySessionToken(raw, secret string, window time.Duration) (sub string, iat, exp time.Time, jti string, ok bool) {
	sub, iat, exp, jti, err := bouncer.VerifyRefreshableClaimsAudience(raw, secret, bouncer.AudienceUser, window)
	if err != nil {
		sub, iat, exp, jti, err = bouncer.VerifyClaims(raw, secret)
	}
	return sub, iat, exp, jti, err == nil && jti != ""
}

// revokedUntil is the storage expiry of a revoked session jti: the later of
// exp and iat plus the refresh window, plus one minute (PHP jwt-auth's
// Blacklist::getMinutesUntilExpired, which bouncer.Refresh follows).
func revokedUntil(iat, exp time.Time, window time.Duration) time.Time {
	until := iat.Add(window)
	if exp.After(until) {
		until = exp
	}
	return until.Add(time.Minute)
}

// refreshWindow is golem15.user.jwt.refresh_ttl minutes, default 20160: the
// window POST /refresh accepts (controllers.RefreshTTL reads the same key).
func refreshWindow(app *backpack.App) time.Duration {
	mins := 20160
	if app != nil && app.Config != nil && app.Config.Int("golem15.user.jwt.refresh_ttl") > 0 {
		mins = app.Config.Int("golem15.user.jwt.refresh_ttl")
	}
	return time.Duration(mins) * time.Minute
}

// sessionToken extracts the session JWT as the "jwt" guard does: the
// Authorization bearer header, then each session cookie in order.
func sessionToken(r *http.Request) string {
	if tokens := sessionTokens(r); len(tokens) > 0 {
		return tokens[0]
	}
	return ""
}

// sessionTokens returns every distinct session JWT r carries, in the order
// the "jwt" guard tries them: the Authorization bearer header, then each
// session cookie. Empty values are skipped.
func sessionTokens(r *http.Request) []string {
	var out []string
	add := func(v string) {
		if v = strings.TrimSpace(v); v != "" && !slices.Contains(out, v) {
			out = append(out, v)
		}
	}
	h := strings.TrimSpace(r.Header.Get("Authorization"))
	if token, ok := strings.CutPrefix(h, "Bearer "); ok {
		add(token)
	}
	for _, name := range sessionCookieNames {
		if c, err := r.Cookie(name); err == nil {
			add(c.Value)
		}
	}
	return out
}