// Copyright (c) 2026 Probo Inc <hello@probo.com>.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

package connect_v1

import (
	"context"
	"errors"
	"net"
	"net/http"

	"github.com/elimity-com/scim"
	scimerrors "github.com/elimity-com/scim/errors"
	"github.com/elimity-com/scim/optional"
	"github.com/elimity-com/scim/schema"
	scimfilter "github.com/scim2/filter-parser/v2"
	"go.gearno.de/kit/httpserver"
	"go.gearno.de/kit/log"
	"go.probo.inc/probo/pkg/bearertoken"
	"go.probo.inc/probo/pkg/coredata"
	"go.probo.inc/probo/pkg/gid"
	"go.probo.inc/probo/pkg/iam"
	scimservice "go.probo.inc/probo/pkg/iam/scim"
	"go.probo.inc/probo/pkg/server/api/clientip"
)

type (
	ctxKey struct{ name string }

	SCIMHandler struct {
		iam    *iam.Service
		logger *log.Logger
	}

	scimResourceHandler struct {
		handler *SCIMHandler
	}

	scimRequestContext struct {
		ctx       context.Context
		config    *coredata.SCIMConfiguration
		ipAddress net.IP
		method    string
		path      string
		userName  string
		handler   *scimResourceHandler
	}
)

var (
	scimConfigCtxKey = &ctxKey{name: "scim_config"}
)

func NewSCIMHandler(iam *iam.Service, logger *log.Logger) *SCIMHandler {
	return &SCIMHandler{iam: iam, logger: logger}
}

func scimConfigFromContext(ctx context.Context) *coredata.SCIMConfiguration {
	config, _ := ctx.Value(scimConfigCtxKey).(*coredata.SCIMConfiguration)
	return config
}

// NewSCIMServer creates a new SCIM server using elimity-com/scim
func NewSCIMServer(h *SCIMHandler) http.Handler {
	schema.SetAllowStringValues(true)

	resourceTypes := []scim.ResourceType{
		{
			ID:          optional.NewString("User"),
			Name:        "User",
			Endpoint:    "/Users",
			Description: optional.NewString("User Account"),
			Schema:      scimservice.UserSchema(),
			SchemaExtensions: []scim.SchemaExtension{
				{Schema: scimservice.EnterpriseUserSchema()},
			},
			Handler: &scimResourceHandler{handler: h},
		},
	}

	serverConfig := scim.ServiceProviderConfig{
		SupportFiltering: true,
		SupportPatch:     true,
		AuthenticationSchemes: []scim.AuthenticationScheme{
			{
				Type:        scim.AuthenticationTypeOauthBearerToken,
				Name:        "OAuth Bearer Token",
				Description: "Authentication using OAuth Bearer Token",
			},
		},
	}

	server, err := scim.NewServer(
		&scim.ServerArgs{
			ServiceProviderConfig: &serverConfig,
			ResourceTypes:         resourceTypes,
		},
	)
	if err != nil {
		panic(err)
	}

	return server
}

// BearerTokenMiddleware validates the bearer token and sets the SCIM configuration in context
func (h *SCIMHandler) BearerTokenMiddleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		authHeader := r.Header.Get("Authorization")
		if authHeader == "" {
			httpserver.RenderError(w, http.StatusUnauthorized, errors.New("authorization header required"))
			return
		}

		token, err := bearertoken.Parse(authHeader)
		if err != nil {
			httpserver.RenderError(w, http.StatusUnauthorized, errors.New("invalid authorization header"))
			return
		}

		config, err := h.iam.SCIMService.ValidateToken(r.Context(), token)
		if err != nil {
			if _, ok := errors.AsType[*scimservice.ErrSCIMInvalidToken](err); ok {
				httpserver.RenderError(w, http.StatusUnauthorized, errors.New("invalid token"))
				return
			}

			h.logger.ErrorCtx(r.Context(), "SCIM token validation error", log.Error(err))
			httpserver.RenderError(w, http.StatusInternalServerError, errors.New("internal server error"))

			return
		}

		ctx := context.WithValue(r.Context(), scimConfigCtxKey, config)
		next.ServeHTTP(w, r.WithContext(ctx))
	})
}

func (rc *scimRequestContext) logAndWrapError(err error, logMsg string) error {
	if scimErr, ok := errors.AsType[scimerrors.ScimError](err); ok {
		errMsg := scimErr.Detail

		// Don't reference profileID for 404 errors - the resource doesn't exist
		userName := rc.userName
		if scimErr.Status == http.StatusNotFound {
			userName = ""
		}

		rc.handler.handler.iam.SCIMService.LogEvent(rc.ctx, rc.config, rc.method, rc.path, userName, rc.ipAddress, scimErr.Status, &errMsg)

		return err
	}

	rc.handler.handler.logger.ErrorCtx(rc.ctx, logMsg, log.Error(err))

	errMsg := "internal server error"
	rc.handler.handler.iam.SCIMService.LogEvent(rc.ctx, rc.config, rc.method, rc.path, rc.userName, rc.ipAddress, 500, &errMsg)

	return scimerrors.ScimErrorInternal
}

func (rc *scimRequestContext) logSuccess(statusCode int) {
	rc.handler.handler.iam.SCIMService.LogEvent(rc.ctx, rc.config, rc.method, rc.path, rc.userName, rc.ipAddress, statusCode, nil)
}

func (h *scimResourceHandler) Create(r *http.Request, attributes scim.ResourceAttributes) (scim.Resource, error) {
	rc := &scimRequestContext{
		ctx:       r.Context(),
		config:    scimConfigFromContext(r.Context()),
		ipAddress: getIPAddress(r),
		method:    "POST",
		path:      "/Users",
		handler:   h,
	}

	resource, err := h.handler.iam.SCIMService.CreateUser(rc.ctx, rc.config, attributes)
	if err != nil {
		return scim.Resource{}, rc.logAndWrapError(err, "cannot create user")
	}

	rc.userName = resource.Attributes["userName"].(string)

	rc.logSuccess(201)

	return resource, nil
}

func (h *scimResourceHandler) Get(r *http.Request, id string) (scim.Resource, error) {
	rc := &scimRequestContext{
		ctx:       r.Context(),
		config:    scimConfigFromContext(r.Context()),
		ipAddress: getIPAddress(r),
		method:    "GET",
		path:      "/Users/" + id,
		handler:   h,
	}

	profileID, err := gid.ParseGID(id)
	if err != nil {
		return scim.Resource{}, rc.logAndWrapError(scimerrors.ScimErrorResourceNotFound(id), "invalid profile ID")
	}

	resource, err := h.handler.iam.SCIMService.GetUser(rc.ctx, rc.config, profileID)
	if err != nil {
		return scim.Resource{}, rc.logAndWrapError(err, "cannot get user")
	}

	rc.userName = resource.Attributes["userName"].(string)

	rc.logSuccess(200)

	return resource, nil
}

func (h *scimResourceHandler) GetAll(r *http.Request, params scim.ListRequestParams) (scim.Page, error) {
	path := "/Users"
	if r.URL.RawQuery != "" {
		path += "?" + r.URL.RawQuery
	}

	rc := &scimRequestContext{
		ctx:       r.Context(),
		config:    scimConfigFromContext(r.Context()),
		ipAddress: getIPAddress(r),
		method:    "GET",
		path:      path,
		handler:   h,
	}

	var filterExpr scimfilter.Expression

	if params.FilterValidator != nil {
		if err := params.FilterValidator.Validate(); err != nil {
			return scim.Page{}, rc.logAndWrapError(scimerrors.ScimErrorBadRequest(err.Error()), "invalid filter")
		}

		filterExpr = params.FilterValidator.GetFilter()
	}

	resources, totalCount, err := h.handler.iam.SCIMService.ListUsers(rc.ctx, rc.config, filterExpr, params.StartIndex, params.Count)
	if err != nil {
		return scim.Page{}, rc.logAndWrapError(err, "cannot list users")
	}

	rc.logSuccess(200)

	return scim.Page{
		TotalResults: totalCount,
		Resources:    resources,
	}, nil
}

func (h *scimResourceHandler) Replace(r *http.Request, id string, attributes scim.ResourceAttributes) (scim.Resource, error) {
	rc := &scimRequestContext{
		ctx:       r.Context(),
		config:    scimConfigFromContext(r.Context()),
		ipAddress: getIPAddress(r),
		method:    "PUT",
		path:      "/Users/" + id,
		handler:   h,
	}

	profileID, err := gid.ParseGID(id)
	if err != nil {
		return scim.Resource{}, rc.logAndWrapError(scimerrors.ScimErrorResourceNotFound(id), "invalid profile ID")
	}

	resource, err := h.handler.iam.SCIMService.ReplaceUser(rc.ctx, rc.config, profileID, attributes)
	if err != nil {
		return scim.Resource{}, rc.logAndWrapError(err, "cannot update user")
	}

	rc.userName = resource.Attributes["userName"].(string)

	rc.logSuccess(200)

	return resource, nil
}

func (h *scimResourceHandler) Patch(r *http.Request, id string, operations []scim.PatchOperation) (scim.Resource, error) {
	rc := &scimRequestContext{
		ctx:       r.Context(),
		config:    scimConfigFromContext(r.Context()),
		ipAddress: getIPAddress(r),
		method:    "PATCH",
		path:      "/Users/" + id,
		handler:   h,
	}

	profileID, err := gid.ParseGID(id)
	if err != nil {
		return scim.Resource{}, rc.logAndWrapError(scimerrors.ScimErrorResourceNotFound(id), "invalid profile ID")
	}

	resource, err := h.handler.iam.SCIMService.PatchUser(rc.ctx, rc.config, profileID, operations)
	if err != nil {
		return scim.Resource{}, rc.logAndWrapError(err, "cannot patch user")
	}

	rc.userName = resource.Attributes["userName"].(string)

	rc.logSuccess(200)

	return resource, nil
}

func (h *scimResourceHandler) Delete(r *http.Request, id string) error {
	rc := &scimRequestContext{
		ctx:       r.Context(),
		config:    scimConfigFromContext(r.Context()),
		ipAddress: getIPAddress(r),
		method:    "DELETE",
		path:      "/Users/" + id,
		handler:   h,
	}

	profileID, err := gid.ParseGID(id)
	if err != nil {
		return rc.logAndWrapError(scimerrors.ScimErrorResourceNotFound(id), "invalid profile ID")
	}

	err = h.handler.iam.SCIMService.DeleteUser(rc.ctx, rc.config, profileID)
	if err != nil {
		return rc.logAndWrapError(err, "cannot delete user")
	}

	rc.userName = ""

	rc.logSuccess(204)

	return nil
}

func getIPAddress(r *http.Request) net.IP {
	if ip := net.ParseIP(clientip.Extract(r)); ip != nil {
		return ip
	}

	return net.IPv4(127, 0, 0, 1)
}