package api

import (
	"log"
	"net/http"
	"time"

	"geniusrun/backend/internal/auth"
)

// SessionConfig configures how the app-login session cookie is minted and
// validated. Secure should mirror config.Config.SessionSecure (true once
// the app is served over HTTPS).
type SessionConfig struct {
	Secret   []byte
	Duration time.Duration
	Secure   bool
	// BackendURL is this app's own externally reachable origin (e.g.
	// "https://geniusrun.example.com", no trailing slash) -- derives
	// OIDCRedirectURL (config.Config), the only thing that must stay pointed
	// at the backend itself, since that's where /api/session/callback is
	// actually served.
	BackendURL string
	// FrontendURL is the origin the browser should land on after any
	// user-facing redirect: the OIDC callback (success or failure) and the
	// post_logout_redirect_uri sent to the identity provider on logout. Some
	// providers, including Keycloak, require an absolute URL matching one
	// registered on the client, not a bare relative path -- see
	// config.Config.FrontendURL for why this can differ from BackendURL in a
	// split-origin deployment.
	FrontendURL string
}

type sessionMeResponse struct {
	Name        string `json:"name"`
	Email       string `json:"email"`
	HasProfile  bool   `json:"has_profile"`
	DisplayName string `json:"display_name,omitempty"`
}

func (s *Server) handleSessionLogin(w http.ResponseWriter, r *http.Request) {
	authURL, txn, err := s.Auth.BeginLogin()
	if err != nil {
		writeError(w, http.StatusBadGateway, err.Error())
		return
	}
	cookie, err := auth.MintTxnCookie(txn, s.Session.Secret, s.Session.Secure)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	http.SetCookie(w, cookie)
	http.Redirect(w, r, authURL, http.StatusFound)
}

func (s *Server) handleSessionCallback(w http.ResponseWriter, r *http.Request) {
	txnCookie, err := r.Cookie(auth.TxnCookieName)
	if err != nil {
		log.Printf("session callback: missing txn cookie: %v", err)
		http.Redirect(w, r, s.Session.FrontendURL+"/?auth_error=failed", http.StatusFound)
		return
	}
	http.SetCookie(w, auth.ClearCookie(auth.TxnCookieName, s.Session.Secure))

	txn, err := auth.ParseTxnCookie(txnCookie, s.Session.Secret)
	if err != nil {
		log.Printf("session callback: failed to parse txn cookie: %v", err)
		http.Redirect(w, r, s.Session.FrontendURL+"/?auth_error=failed", http.StatusFound)
		return
	}

	result, err := s.Auth.HandleCallback(r.Context(), txn, r.URL.Query())
	if err != nil {
		log.Printf("session callback: HandleCallback failed (state mismatch, code exchange, or ID-token verification): %v", err)
		http.Redirect(w, r, s.Session.FrontendURL+"/?auth_error=failed", http.StatusFound)
		return
	}
	if !result.Authorized {
		http.Redirect(w, r, s.Session.FrontendURL+"/?auth_error=forbidden", http.StatusFound)
		return
	}

	sessionCookie, err := auth.MintSessionCookie(result.Claims, s.Session.Secret, s.Session.Duration, s.Session.Secure)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	http.SetCookie(w, sessionCookie)
	http.Redirect(w, r, s.Session.FrontendURL+"/", http.StatusFound)
}

// handleSessionLogout clears geniusrun's own session cookie and redirects
// through Keycloak's end-session endpoint, passing the session's ID token
// as id_token_hint (see auth.Claims.IDToken) so Keycloak can skip its own
// logout-confirmation prompt -- otherwise a user could cancel out of it and
// land back on the app with a Keycloak SSO session but no geniusrun profile
// (already deleted, in the profile-deletion case this exists for).
func (s *Server) handleSessionLogout(w http.ResponseWriter, r *http.Request) {
	claims, _ := auth.ClaimsFromContext(r.Context())
	http.SetCookie(w, auth.ClearCookie(auth.SessionCookieName, s.Session.Secure))
	http.Redirect(w, r, s.Auth.EndSessionURL(s.Session.FrontendURL+"/", claims.IDToken), http.StatusFound)
}

func (s *Server) handleSessionMe(w http.ResponseWriter, r *http.Request) {
	claims, ok := auth.ClaimsFromContext(r.Context())
	if !ok {
		// Unreachable in practice -- RequireSession already 401s before this
		// handler runs -- but fail closed rather than panic if that ever changes.
		writeError(w, http.StatusUnauthorized, "not authenticated")
		return
	}
	resp := sessionMeResponse{Name: claims.Name, Email: claims.Email}
	if u, found := userFromContext(r.Context()); found {
		resp.HasProfile = true
		resp.DisplayName = u.DisplayName
	}
	writeJSON(w, http.StatusOK, resp)
}