package httpapi

import (
	"context"
	"crypto/rand"
	"crypto/subtle"
	"encoding/hex"
	"errors"
	"net/http"
	"strings"

	"github.com/alexedwards/scs/v2"
	"github.com/descrybe/descrybe-v2/apps/api/internal/auth"
	"github.com/google/uuid"
)

type ctxKey string

const (
	ctxUserID      ctxKey = "user_id"
	ctxCompanyID   ctxKey = "company_id"
	ctxRole        ctxKey = "role"
	ctxStaffAccess ctxKey = "staff_access"
)

func UserIDFromContext(ctx context.Context) (uuid.UUID, bool) {
	v, ok := ctx.Value(ctxUserID).(uuid.UUID)
	return v, ok
}

func CompanyIDFromContext(ctx context.Context) (uuid.UUID, bool) {
	v, ok := ctx.Value(ctxCompanyID).(uuid.UUID)
	return v, ok
}

func RoleFromContext(ctx context.Context) (string, bool) {
	v, ok := ctx.Value(ctxRole).(string)
	return v, ok
}

// CompanyAdminAllowed reports whether the caller may perform company-admin
// mutations. Session role "admin" and API-key auth role "api" (admin-owned keys
// only — see apiKeyContextRole) are allowed; members are not.
func CompanyAdminAllowed(ctx context.Context) bool {
	role, _ := RoleFromContext(ctx)
	return role == "admin" || role == "api"
}

// apiKeyContextRole maps the key owner's membership role onto the request role.
// Admin-owned keys keep legacy "api" privileges (CompanyAdminAllowed). Non-admin
// owners keep membership role so product reset / admin-gated deletes stay closed.
// Full scopes + expiry are deferred: api_keys has no scopes/expires_at columns yet;
// dashboard creation remains admin-only (allowCompanyAdminOrPlatform).
func apiKeyContextRole(membershipRole string) string {
	if auth.NormalizeMembershipRole(membershipRole) == "admin" {
		return "api"
	}
	return auth.NormalizeMembershipRole(membershipRole)
}

func requireCompanyAdmin(w http.ResponseWriter, r *http.Request) bool {
	if CompanyAdminAllowed(r.Context()) {
		return true
	}
	Error(w, http.StatusForbidden, "admin required")
	return false
}

// allowCompanyAdminOrPlatform allows company admins, API keys, or platform admins.
// Platform admins can manage team after migration when all memberships are still "member".
func (s *Server) allowCompanyAdminOrPlatform(w http.ResponseWriter, r *http.Request) bool {
	if CompanyAdminAllowed(r.Context()) {
		return true
	}
	uid, ok := UserIDFromContext(r.Context())
	if !ok {
		Error(w, http.StatusUnauthorized, "unauthorized")
		return false
	}
	isAdmin, err := s.checkPlatformAdmin(r.Context(), uid)
	if err != nil {
		Error(w, http.StatusInternalServerError, "authorization check failed")
		return false
	}
	if isAdmin {
		return true
	}
	Error(w, http.StatusForbidden, "admin required")
	return false
}

// allowCompanyOwnerOrPlatform allows the company billing owner or a platform admin.
// When owner_user_id is unset (pre-backfill), falls back to company admin so billing is not locked out.
func (s *Server) allowCompanyOwnerOrPlatform(w http.ResponseWriter, r *http.Request) bool {
	uid, ok := UserIDFromContext(r.Context())
	if !ok {
		Error(w, http.StatusUnauthorized, "unauthorized")
		return false
	}
	isAdmin, err := s.checkPlatformAdmin(r.Context(), uid)
	if err != nil {
		Error(w, http.StatusInternalServerError, "authorization check failed")
		return false
	}
	if isAdmin {
		return true
	}
	cid, ok := CompanyIDFromContext(r.Context())
	if !ok {
		Error(w, http.StatusForbidden, "company required")
		return false
	}
	if s.Auth != nil {
		ownerID, hasOwner, err := s.Auth.CompanyOwnerID(r.Context(), cid)
		if err != nil {
			Error(w, http.StatusInternalServerError, "authorization check failed")
			return false
		}
		if hasOwner {
			if ownerID == uid {
				return true
			}
			Error(w, http.StatusForbidden, "company owner required")
			return false
		}
	}
	// Legacy fallback before owner backfill, or unit tests without Auth wired.
	if CompanyAdminAllowed(r.Context()) {
		return true
	}
	Error(w, http.StatusForbidden, "company owner required")
	return false
}

func (s *Server) RequireSession(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		uidStr := s.Sessions.GetString(r.Context(), auth.SessionUserIDKey)
		if uidStr == "" {
			Error(w, http.StatusUnauthorized, "unauthorized")
			return
		}
		uid, err := uuid.Parse(uidStr)
		if err != nil {
			Error(w, http.StatusUnauthorized, "unauthorized")
			return
		}
		sessionVersion := s.Sessions.GetInt(r.Context(), auth.SessionVersionKey)
		if active, checked, err := s.sessionUserIsActive(r.Context(), uid, sessionVersion); err != nil || (checked && !active) {
			_ = s.Sessions.Destroy(r.Context())
			Error(w, http.StatusUnauthorized, "unauthorized")
			return
		}
		ctx := context.WithValue(r.Context(), ctxUserID, uid)
		next.ServeHTTP(w, r.WithContext(ctx))
	})
}

// sessionUserIsActive reports whether the session user may continue.
// checked=false means the active flag could not be verified (unit tests without a DB pool).
// sessionVersion must match users.session_version (bumped on password reset).
func (s *Server) sessionUserIsActive(ctx context.Context, userID uuid.UUID, sessionVersion int) (active bool, checked bool, err error) {
	if s != nil && s.testUserSessionState != nil {
		st, err := s.testUserSessionState(ctx, userID)
		if err != nil {
			return false, true, err
		}
		if !st.Active || st.Version != sessionVersion {
			return false, true, nil
		}
		return true, true, nil
	}
	if s != nil && s.testUserActive != nil {
		ok, err := s.testUserActive(ctx, userID)
		return ok, true, err
	}
	if s == nil || s.Auth == nil || s.Auth.Pool == nil {
		return true, false, nil
	}
	st, err := s.Auth.UserSessionState(ctx, userID)
	if err != nil {
		return false, true, err
	}
	if !st.Active || st.Version != sessionVersion {
		return false, true, nil
	}
	return true, true, nil
}

func (s *Server) RequireCompany(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		uid, ok := UserIDFromContext(r.Context())
		if !ok {
			Error(w, http.StatusUnauthorized, "unauthorized")
			return
		}
		cidStr := s.Sessions.GetString(r.Context(), auth.SessionCompanyIDKey)
		if cidStr == "" {
			Error(w, http.StatusBadRequest, "company not selected")
			return
		}
		cid, err := uuid.Parse(cidStr)
		if err != nil {
			Error(w, http.StatusBadRequest, "invalid company")
			return
		}
		m, err := s.Auth.EnsureMembership(r.Context(), uid, cid)
		if err != nil {
			if errors.Is(err, auth.ErrNotCompanyMember) && s.staffMayActAsCompany(r.Context(), uid) {
				ctx := context.WithValue(r.Context(), ctxCompanyID, cid)
				ctx = context.WithValue(ctx, ctxRole, "admin")
				next.ServeHTTP(w, r.WithContext(ctx))
				return
			}
			Error(w, http.StatusForbidden, "forbidden")
			return
		}
		ctx := context.WithValue(r.Context(), ctxCompanyID, cid)
		ctx = context.WithValue(ctx, ctxRole, m.Role)
		next.ServeHTTP(w, r.WithContext(ctx))
	})
}

// staffMayActAsCompany is true only for platform staff_role=admin (or legacy
// is_platform_admin → admin). Developers and support_staff cannot tenant-switch.
func (s *Server) staffMayActAsCompany(ctx context.Context, userID uuid.UUID) bool {
	access, err := s.checkStaffAccess(ctx, userID)
	if err != nil || !access.FullAdmin {
		return false
	}
	return access.Role == auth.StaffRoleAdmin
}

func (s *Server) CSRF(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		// Public API-key and token export routes do not use cookie CSRF.
		// Match path segments only (/api/v1, /api/v1/...) — not prefixes like /api/v10.
		if csrfExemptPath(r.URL.Path) {
			next.ServeHTTP(w, r)
			return
		}

		cookie, err := r.Cookie(s.Config.CSRFCookieName)
		token := ""
		if err == nil {
			token = cookie.Value
		}
		if token == "" {
			b := make([]byte, 16)
			if _, err := rand.Read(b); err != nil {
				Error(w, http.StatusInternalServerError, "csrf token unavailable")
				return
			}
			token = hex.EncodeToString(b)
			http.SetCookie(w, &http.Cookie{
				Name:     s.Config.CSRFCookieName,
				Value:    token,
				Path:     "/",
				HttpOnly: false, // readable by SPA for X-CSRF-Token double-submit
				Secure:   s.Config.CookieSecure(),
				SameSite: http.SameSiteLaxMode,
				MaxAge:   7 * 24 * 60 * 60,
			})
		}
		// Expose for cross-origin SPAs (api.* vs app host): document.cookie cannot
		// read host-only API cookies; the client seeds via GET and mirrors this header.
		w.Header().Set("X-CSRF-Token", token)

		if r.Method == http.MethodGet || r.Method == http.MethodHead || r.Method == http.MethodOptions {
			next.ServeHTTP(w, r)
			return
		}
		header := r.Header.Get("X-CSRF-Token")
		if header == "" || subtle.ConstantTimeCompare([]byte(header), []byte(token)) != 1 {
			Error(w, http.StatusForbidden, "csrf token mismatch")
			return
		}
		next.ServeHTTP(w, r)
	})
}

// csrfExemptPath is true for public API-key / token / webhook surfaces that
// authenticate without cookie CSRF (Bearer/HMAC/signature).
func csrfExemptPath(path string) bool {
	switch {
	case path == "/api/v1", strings.HasPrefix(path, "/api/v1/"):
		return true
	case path == "/api/public", strings.HasPrefix(path, "/api/public/"):
		return true
	case path == "/api/webhooks", strings.HasPrefix(path, "/api/webhooks/"):
		return true
	default:
		return false
	}
}

// extractAPIKey reads the raw key from Authorization Bearer or X-API-Key.
// Preference matches legacy Descrybe: Bearer first, then X-API-Key / X-Api-Key
// (Go canonicalizes header names; both spellings resolve).
func extractAPIKey(r *http.Request) string {
	authz := strings.TrimSpace(r.Header.Get("Authorization"))
	if authz != "" {
		const bearer = "Bearer "
		if len(authz) > len(bearer) && strings.EqualFold(authz[:len(bearer)], bearer) {
			if key := strings.TrimSpace(authz[len(bearer):]); key != "" {
				return key
			}
		}
	}
	if k := strings.TrimSpace(r.Header.Get("X-API-Key")); k != "" {
		return k
	}
	return ""
}

// RequireAPIKey authenticates via Bearer or X-API-Key and binds company/user context.
func (s *Server) RequireAPIKey(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		raw := extractAPIKey(r)
		if raw == "" {
			CodedError(w, http.StatusUnauthorized, "unauthorized", "Unauthorized")
			return
		}
		id, err := s.Auth.AuthenticateAPIKey(r.Context(), raw)
		if err != nil {
			if errors.Is(err, auth.ErrInvalidAPIKey) {
				CodedError(w, http.StatusUnauthorized, "unauthorized", "Unauthorized")
				return
			}
			CodedError(w, http.StatusInternalServerError, "auth_failed", "Authentication failed")
			return
		}
		ctx := context.WithValue(r.Context(), ctxUserID, id.UserID)
		ctx = context.WithValue(ctx, ctxCompanyID, id.CompanyID)
		ctx = context.WithValue(ctx, ctxRole, apiKeyContextRole(id.MembershipRole))
		next.ServeHTTP(w, r.WithContext(ctx))
	})
}

func LoadSession(sm *scs.SessionManager) func(http.Handler) http.Handler {
	return sm.LoadAndSave
}

// MaintenanceGate enforces MAINTENANCE_MODE / READ_ONLY_MODE.
// /healthz and /readyz always pass so cutover rehearsal probes keep working.
func (s *Server) MaintenanceGate(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if r.URL.Path == "/healthz" || r.URL.Path == "/readyz" {
			next.ServeHTTP(w, r)
			return
		}
		if s.Config.MaintenanceMode {
			JSON(w, http.StatusServiceUnavailable, map[string]any{
				"error": "maintenance", "maintenance": true, "read_only": s.Config.ReadOnlyMode,
			})
			return
		}
		if s.Config.ReadOnlyMode {
			switch r.Method {
			case http.MethodPost, http.MethodPut, http.MethodPatch, http.MethodDelete:
				JSON(w, http.StatusServiceUnavailable, map[string]any{
					"error": "read_only", "maintenance": false, "read_only": true,
				})
				return
			}
		}
		next.ServeHTTP(w, r)
	})
}

// RequirePlatformAdmin allows full platform staff (admin/developer or legacy
// is_platform_admin with empty staff_role). support_staff is excluded.
func (s *Server) RequirePlatformAdmin(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		uid, ok := UserIDFromContext(r.Context())
		if !ok {
			Error(w, http.StatusUnauthorized, "unauthorized")
			return
		}
		access, err := s.checkStaffAccess(r.Context(), uid)
		if err != nil || !access.FullAdmin {
			Error(w, http.StatusForbidden, "platform admin required")
			return
		}
		next.ServeHTTP(w, r.WithContext(withStaffAccess(r.Context(), access)))
	})
}

// RequireSupportDesk allows full platform admin OR support_staff.
// Plan/billing/settings mutations must stay on RequirePlatformAdmin.
func (s *Server) RequireSupportDesk(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		uid, ok := UserIDFromContext(r.Context())
		if !ok {
			Error(w, http.StatusUnauthorized, "unauthorized")
			return
		}
		access, err := s.checkStaffAccess(r.Context(), uid)
		if err != nil || !access.SupportDesk {
			Error(w, http.StatusForbidden, "support desk access required")
			return
		}
		next.ServeHTTP(w, r.WithContext(withStaffAccess(r.Context(), access)))
	})
}

func withStaffAccess(ctx context.Context, access auth.StaffAccess) context.Context {
	return context.WithValue(ctx, ctxStaffAccess, access)
}

// StaffAccessFromContext returns capability flags set by RequirePlatformAdmin / RequireSupportDesk.
func StaffAccessFromContext(ctx context.Context) (auth.StaffAccess, bool) {
	v, ok := ctx.Value(ctxStaffAccess).(auth.StaffAccess)
	return v, ok
}

// checkPlatformAdmin prefers an optional test hook, otherwise Auth.IsPlatformAdmin.
func (s *Server) checkPlatformAdmin(ctx context.Context, userID uuid.UUID) (bool, error) {
	if s != nil && s.testPlatformAdmin != nil {
		return s.testPlatformAdmin(ctx, userID)
	}
	if s == nil || s.Auth == nil {
		return false, nil
	}
	return s.Auth.IsPlatformAdmin(ctx, userID)
}

// checkStaffAccess prefers test hooks, otherwise Auth.GetStaffAccess.
func (s *Server) checkStaffAccess(ctx context.Context, userID uuid.UUID) (auth.StaffAccess, error) {
	if s != nil && s.testStaffAccess != nil {
		return s.testStaffAccess(ctx, userID)
	}
	if s != nil && s.testPlatformAdmin != nil {
		ok, err := s.testPlatformAdmin(ctx, userID)
		if err != nil {
			return auth.StaffAccess{}, err
		}
		return auth.ResolveStaffAccess(ok, ""), nil
	}
	if s == nil || s.Auth == nil {
		return auth.StaffAccess{}, nil
	}
	return s.Auth.GetStaffAccess(ctx, userID)
}