package middleware

import (
	"context"
	"errors"
	"strings"
	"sync"

	"github.com/gofiber/fiber/v2"
	"gitlab.com/mbugroup/lti-api.git/internal/apikeys"
	"gitlab.com/mbugroup/lti-api.git/internal/config"
	entity "gitlab.com/mbugroup/lti-api.git/internal/entities"
	"gitlab.com/mbugroup/lti-api.git/internal/modules/sso/session"
	sso "gitlab.com/mbugroup/lti-api.git/internal/modules/sso/verifier"
	service "gitlab.com/mbugroup/lti-api.git/internal/modules/users/services"
	"gitlab.com/mbugroup/lti-api.git/internal/utils"
)

const (
	authContextLocalsKey = "auth.context"
	authUserLocalsKey    = "auth.user"
)

var (
	verifyAccessTokenFunc = sso.VerifyAccessToken
	fetchProfileFunc      = sso.FetchProfile

	apiKeyAuthMu        sync.RWMutex
	apiKeyAuthenticator apikeys.Authenticator
)

// AuthContext keeps authentication details captured by the middleware.
type AuthContext struct {
	Token           string
	Verification    *sso.VerificationResult
	User            *entity.User
	PrincipalType   string
	PrincipalName   string
	Roles           []sso.Role
	Permissions     map[string]struct{}
	UserAreaIDs     []uint
	UserLocationIDs []uint
	UserAllArea     bool
	UserAllLocation bool
}

func SetAPIKeyAuthenticator(authenticator apikeys.Authenticator) {
	apiKeyAuthMu.Lock()
	defer apiKeyAuthMu.Unlock()

	apiKeyAuthenticator = authenticator
}

// Auth validates the incoming request against the central SSO access token and
// loads the corresponding local user. Optional scopes can be provided to enforce
// fine-grained authorization using the SSO access token scopes.
func Auth(userService service.UserService, requiredScopes ...string) fiber.Handler {
	return func(c *fiber.Ctx) error {
		token := bearerToken(c)
		tokenSource := ""
		if token != "" {
			tokenSource = "header"
		} else {
			primaryName := strings.TrimSpace(config.SSOAccessCookieName)
			if primaryName != "" {
				token = strings.TrimSpace(c.Cookies(primaryName))
				if token != "" {
					tokenSource = "cookie:" + primaryName
				}
			}
			if token == "" {
				for _, name := range config.SSOAccessCookieFallback {
					name = strings.TrimSpace(name)
					if name == "" || name == primaryName {
						continue
					}
					token = strings.TrimSpace(c.Cookies(name))
					if token != "" {
						tokenSource = "cookie:" + name
						break
					}
				}
			}
		}
		if token == "" {
			if c.Method() == fiber.MethodGet {
				if err := authenticateAPIKey(c); err == nil {
					if len(requiredScopes) > 0 {
						return fiber.NewError(fiber.StatusForbidden, "Insufficient scope")
					}
					return c.Next()
				} else if err != nil && !errors.Is(err, apikeys.ErrInvalidAPIKey) && !errors.Is(err, apikeys.ErrInactiveKey) {
					return err
				}
			}
			return fiber.NewError(fiber.StatusUnauthorized, "Please authenticate")
		}

		verification, err := verifyAccessTokenFunc(token)
		if err != nil {
			if sso.IsSignatureError(err) {
				logSignatureError("auth", tokenSource, token, err)
			} else {
				utils.Log.WithError(err).Warn("auth: token verification failed")
			}
			return fiber.NewError(fiber.StatusUnauthorized, "Please authenticate")
		}

		if verification.UserID == 0 {
			return fiber.NewError(fiber.StatusForbidden, "Service authentication is not permitted for this endpoint")
		}

		if err := ensureNotRevoked(c, token, verification); err != nil {
			return err
		}

		user, err := userService.GetBySSOUserID(c, verification.UserID)
		if err != nil || user == nil {
			utils.Log.WithError(err).Warn("auth: failed to resolve user from repository")
			return fiber.NewError(fiber.StatusUnauthorized, "Please authenticate")
		}

		if len(requiredScopes) > 0 {
			if verification.Claims == nil || !hasAllScopes(verification.Claims.Scopes(), requiredScopes) {
				return fiber.NewError(fiber.StatusForbidden, "Insufficient scope")
			}
		}

		var roles []sso.Role
		permissions := make(map[string]struct{})
		var profile *sso.UserProfile
		if verification.UserID != 0 {
			if p, err := fetchProfileFunc(c.Context(), token, verification); err != nil {
				utils.Log.WithError(err).Warn("auth: failed to fetch sso profile")
			} else {
				profile = p
			}
		}
		if profile != nil {
			roles = profile.Roles
			for _, perm := range profile.PermissionNames() {
				if perm != "" {
					permissions[perm] = struct{}{}
				}
			}
		}

		ctx := &AuthContext{
			Token:           token,
			Verification:    verification,
			User:            user,
			PrincipalType:   "user",
			PrincipalName:   user.Name,
			Roles:           roles,
			Permissions:     permissions,
			UserAreaIDs:     nil,
			UserLocationIDs: nil,
			UserAllArea:     false,
			UserAllLocation: false,
		}
		if profile != nil {
			ctx.UserAreaIDs = profile.AreaIDs
			ctx.UserLocationIDs = profile.LocationIDs
			ctx.UserAllArea = profile.AllArea
			ctx.UserAllLocation = profile.AllLocation
		}

		c.Locals(authContextLocalsKey, ctx)
		c.Locals(authUserLocalsKey, user)
		return c.Next()
	}
}

// AuthenticatedUser returns the authenticated user populated by Auth.
func AuthenticatedUser(c *fiber.Ctx) (*entity.User, bool) {
	value := c.Locals(authUserLocalsKey)
	if user, ok := value.(*entity.User); ok && user != nil {
		return user, true
	}
	return nil, false
}

func ActorIDFromContext(c *fiber.Ctx) (uint, error) {
	user, ok := AuthenticatedUser(c)
	if !ok || user == nil || user.Id == 0 {
		return 0, fiber.NewError(fiber.StatusUnauthorized, "Please authenticate")
	}
	return user.Id, nil
}

// AuthDetails returns the full authentication context (token, claims, user).
func AuthDetails(c *fiber.Ctx) (*AuthContext, bool) {
	value := c.Locals(authContextLocalsKey)
	if ctx, ok := value.(*AuthContext); ok && ctx != nil {
		return ctx, true
	}
	return nil, false
}

// ensureNotRevoked ensures the token is not revoked or superseded by a forced logout.
func ensureNotRevoked(c *fiber.Ctx, token string, verification *sso.VerificationResult) error {
	revoker := session.GetRevocationStore()
	if revoker == nil {
		return nil
	}

	if fingerprint := session.TokenFingerprint(token); fingerprint != "" {
		revoked, err := revoker.IsRevoked(c.Context(), fingerprint)
		if err != nil {
			utils.Log.WithError(err).Warn("auth: token revocation check failed")
			return fiber.NewError(fiber.StatusUnauthorized, "Please authenticate")
		}
		if revoked {
			return fiber.NewError(fiber.StatusUnauthorized, "Please authenticate")
		}
	}

	if verification.UserID == 0 {
		return nil
	}

	logoutAt, err := revoker.UserLogoutTime(c.Context(), verification.UserID)
	if err != nil {
		utils.Log.WithError(err).Warn("auth: failed to load user logout marker")
		return fiber.NewError(fiber.StatusUnauthorized, "Please authenticate")
	}
	if logoutAt.IsZero() {
		return nil
	}

	claims := verification.Claims
	if claims == nil || claims.IssuedAt == nil {
		return fiber.NewError(fiber.StatusUnauthorized, "Please authenticate")
	}

	issuedAt := claims.IssuedAt.Time
	// Treat tokens issued at or before the forced logout timestamp as invalid.
	if !issuedAt.After(logoutAt) {
		return fiber.NewError(fiber.StatusUnauthorized, "Please authenticate")
	}

	return nil
}

// bearerToken extracts a Bearer token from the Authorization header using
// case-insensitive scheme matching and tolerant whitespace handling.
func bearerToken(c *fiber.Ctx) string {
	parts := strings.Fields(c.Get("Authorization"))
	if len(parts) == 2 && strings.EqualFold(parts[0], "Bearer") {
		return strings.TrimSpace(parts[1])
	}
	return ""
}

func authenticateAPIKey(c *fiber.Ctx) error {
	rawKey := strings.TrimSpace(c.Get("X-API-Key"))
	if rawKey == "" {
		return apikeys.ErrInvalidAPIKey
	}

	authenticator := currentAPIKeyAuthenticator()
	if authenticator == nil {
		return apikeys.ErrInvalidAPIKey
	}

	principal, err := authenticator.Authenticate(context.Background(), rawKey, c.IP())
	if err != nil {
		if errors.Is(err, apikeys.ErrInvalidAPIKey) || errors.Is(err, apikeys.ErrInactiveKey) {
			return apikeys.ErrInvalidAPIKey
		}
		utils.Log.WithError(err).Warn("auth: api key authentication failed")
		return fiber.NewError(fiber.StatusInternalServerError, "Failed to authenticate request")
	}

	permissions := make(map[string]struct{}, len(principal.Permissions))
	for _, perm := range principal.Permissions {
		if canonical := canonicalPermission(perm); canonical != "" {
			permissions[canonical] = struct{}{}
		}
	}

	c.Locals(authContextLocalsKey, &AuthContext{
		Token:           "",
		Verification:    nil,
		User:            nil,
		PrincipalType:   "api_key",
		PrincipalName:   principal.Name,
		Roles:           nil,
		Permissions:     permissions,
		UserAreaIDs:     principal.AreaIDs,
		UserLocationIDs: principal.LocationIDs,
		UserAllArea:     principal.AllArea,
		UserAllLocation: principal.AllLocation,
	})
	c.Locals(authUserLocalsKey, nil)
	return nil
}

func currentAPIKeyAuthenticator() apikeys.Authenticator {
	apiKeyAuthMu.RLock()
	defer apiKeyAuthMu.RUnlock()

	return apiKeyAuthenticator
}

func hasAllScopes(have, required []string) bool {
	if len(required) == 0 {
		return true
	}
	set := make(map[string]struct{}, len(have))
	for _, s := range have {
		s = strings.ToLower(strings.TrimSpace(s))
		if s != "" {
			set[s] = struct{}{}
		}
	}
	for _, r := range required {
		r = strings.ToLower(strings.TrimSpace(r))
		if r == "" {
			continue
		}
		if _, ok := set[r]; !ok {
			return false
		}
	}
	return true
}

func logSignatureError(ctxLabel, tokenSource, token string, err error) {
	info := sso.ExtractTokenInfo(token)
	aud := strings.Join(info.Aud, ",")
	utils.Log.Errorf(
		"access token verification failed: %v | ctx=%s source=%s iss=%s kid=%s aud=%s sub=%s exp=%d iat=%d nbf=%d expected_iss=%s expected_aud=%v",
		err,
		ctxLabel,
		tokenSource,
		info.Iss,
		info.Kid,
		aud,
		info.Sub,
		info.Exp,
		info.Iat,
		info.Nbf,
		config.SSOIssuer,
		config.SSOAllowedAudiences,
	)
}

// RequirePermissions ensures the authenticated user possesses all specified permissions.
func RequirePermissions(perms ...string) fiber.Handler {
	required := canonicalPermissions(perms)
	return func(c *fiber.Ctx) error {
		if len(required) == 0 {
			return c.Next()
		}

		ctx, ok := AuthDetails(c)
		if !ok || ctx == nil {
			return fiber.NewError(fiber.StatusUnauthorized, "Please authenticate")
		}

		userPerms := ctx.permissionSet()
		if len(userPerms) == 0 {
			return fiber.NewError(fiber.StatusForbidden, "Insufficient permission")
		}

		for _, perm := range required {
			if _, has := userPerms[perm]; !has {
				return fiber.NewError(fiber.StatusForbidden, "Insufficient permission")
			}
		}

		return c.Next()
	}
}

// HasPermission reports whether the current request context includes the given permission.
func HasPermission(c *fiber.Ctx, perm string) bool {
	ctx, ok := AuthDetails(c)
	if !ok || ctx == nil {
		return false
	}
	perm = canonicalPermission(perm)
	if perm == "" {
		return false
	}
	_, has := ctx.permissionSet()[perm]
	return has
}

func (a *AuthContext) permissionSet() map[string]struct{} {
	if a == nil || a.Permissions == nil {
		return nil
	}
	return a.Permissions
}

func canonicalPermissions(perms []string) []string {
	out := make([]string, 0, len(perms))
	seen := make(map[string]struct{}, len(perms))
	for _, perm := range perms {
		if canonical := canonicalPermission(perm); canonical != "" {
			if _, ok := seen[canonical]; ok {
				continue
			}
			seen[canonical] = struct{}{}
			out = append(out, canonical)
		}
	}
	return out
}

func canonicalPermission(perm string) string {
	return strings.ToLower(strings.TrimSpace(perm))
}