// Copyright (c) 2025-2026 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"
	"fmt"
	"net/http"
	"net/url"

	"github.com/go-chi/chi/v5"
	"go.gearno.de/kit/httpserver"
	"go.gearno.de/kit/log"
	"go.probo.inc/probo/pkg/baseurl"
	"go.probo.inc/probo/pkg/gid"
	"go.probo.inc/probo/pkg/iam"
	"go.probo.inc/probo/pkg/saferedirect"
	"go.probo.inc/probo/pkg/securecookie"
	"go.probo.inc/probo/pkg/server/api/authn"
)

type SAMLHandler struct {
	iam           *iam.Service
	sessionCookie *authn.Cookie
	baseURL       *baseurl.BaseURL
	logger        *log.Logger
	safeRedirect  *saferedirect.SafeRedirect
}

func NewSAMLHandler(iam *iam.Service, cookieConfig securecookie.Config, baseURL *baseurl.BaseURL, logger *log.Logger) *SAMLHandler {
	return &SAMLHandler{
		iam:           iam,
		sessionCookie: authn.NewCookie(&cookieConfig),
		baseURL:       baseURL,
		logger:        logger,
		safeRedirect:  saferedirect.New(saferedirect.StaticHosts(baseURL.Host())),
	}
}

func (h *SAMLHandler) renderInternalServerError(w http.ResponseWriter) {
	httpserver.RenderError(w, http.StatusInternalServerError, errors.New("internal server error"))
}

func (h *SAMLHandler) continueURLFromRelayState(ctx context.Context, relayState string) string {
	if len(relayState) <= gid.EncodedGIDSize {
		return ""
	}

	unescapedContinueURL, err := url.QueryUnescape(relayState[gid.EncodedGIDSize:])
	if err != nil {
		return ""
	}

	safeContinue, ok := h.safeRedirect.Validate(ctx, unescapedContinueURL)
	if !ok {
		return ""
	}

	return safeContinue
}

func (h *SAMLHandler) renderAssertionError(w http.ResponseWriter, r *http.Request, relayState string, err error) {
	h.logger.ErrorCtx(r.Context(), "cannot handle SAML assertion", log.Error(err))
	continueURL := h.continueURLFromRelayState(r.Context(), relayState)
	redirectAuthError(w, r, authErrorAuthenticationFailed, continueURL)
}

func (h *SAMLHandler) MetadataHandler(w http.ResponseWriter, r *http.Request) {
	metadataXML, err := h.iam.SAMLService.GenerateSpMetadata()
	if err != nil {
		panic(fmt.Errorf("cannot generate metadata: %w", err))
	}

	w.Header().Set("Content-Type", "application/samlmetadata+xml")
	w.WriteHeader(http.StatusOK)
	_, _ = w.Write(metadataXML)
}

func (h *SAMLHandler) ConsumeHandler(w http.ResponseWriter, r *http.Request) {
	ctx := r.Context()

	err := r.ParseForm()
	if err != nil {
		httpserver.RenderError(w, http.StatusBadRequest, errors.New("cannot parse form"))
		return
	}

	samlResponse := r.FormValue("SAMLResponse")
	relayState := r.FormValue("RelayState")

	if len(relayState) < gid.EncodedGIDSize {
		httpserver.RenderError(w, http.StatusBadRequest, errors.New("invalid relay state"))
		return
	}

	configIDStr := relayState[:gid.EncodedGIDSize]
	if configIDStr == "" {
		httpserver.RenderError(w, http.StatusBadRequest, errors.New("missing config ID"))
		return
	}

	configID, err := gid.ParseGID(configIDStr)
	if err != nil {
		httpserver.RenderError(w, http.StatusBadRequest, errors.New("invalid config ID"))
		return
	}

	user, membership, err := h.iam.SAMLService.HandleAssertion(ctx, samlResponse, configID)
	if err != nil {
		h.renderAssertionError(w, r, relayState, err)

		return
	}

	continueURL := "/organizations/" + membership.OrganizationID.String()

	if len(relayState) > gid.EncodedGIDSize {
		unescapedContinueURL, err := url.QueryUnescape(relayState[gid.EncodedGIDSize:])
		if err != nil {
			h.logger.WarnCtx(ctx, "cannot unescape continue URL from RelayState", log.Error(err))
		} else {
			continueURL = unescapedContinueURL
		}
	}

	rootSession := authn.SessionFromContext(ctx)

	switch {
	case rootSession == nil:
		rootSession, err = h.iam.AuthService.OpenSessionWithSAML(ctx, user.ID)
		if err != nil {
			h.logger.ErrorCtx(ctx, "cannot open root session", log.Error(err))
			h.renderInternalServerError(w)

			return
		}
	case rootSession.IdentityID != user.ID:
		err = h.iam.SessionService.CloseSession(ctx, rootSession.ID)
		if err != nil {
			h.logger.ErrorCtx(ctx, "cannot close session", log.Error(err))
			h.renderInternalServerError(w)

			return
		}

		rootSession, err = h.iam.AuthService.OpenSessionWithSAML(ctx, user.ID)
		if err != nil {
			h.logger.ErrorCtx(ctx, "cannot open root session", log.Error(err))
			h.renderInternalServerError(w)

			return
		}
	}

	_, _, err = h.iam.SessionService.OpenSAMLChildSessionForOrganization(ctx, rootSession.ID, membership.OrganizationID)
	if err != nil {
		h.logger.ErrorCtx(ctx, "cannot open SAML child session", log.Error(err))
		h.renderInternalServerError(w)

		return
	}

	h.sessionCookie.Set(w, rootSession)

	h.safeRedirect.Redirect(w, r, continueURL, "/organizations/"+membership.OrganizationID.String(), http.StatusFound)
}

func (h *SAMLHandler) LoginHandler(w http.ResponseWriter, r *http.Request) {
	ctx := r.Context()

	samlConfigIDParam := chi.URLParam(r, "samlConfigID")
	if samlConfigIDParam == "" {
		httpserver.RenderError(w, http.StatusBadRequest, errors.New("missing SAML config ID"))
		return
	}

	continueURLQueryParam := r.URL.Query().Get("continue")

	samlConfigID, err := gid.ParseGID(samlConfigIDParam)
	if err != nil {
		httpserver.RenderError(w, http.StatusBadRequest, errors.New("invalid SAML config ID"))
		return
	}

	url, err := h.iam.SAMLService.InitiateLogin(ctx, samlConfigID, continueURLQueryParam)
	if err != nil {
		panic(fmt.Errorf("cannot initiate SAML login: %w", err))
	}

	http.Redirect(w, r, url.String(), http.StatusFound)
}