package api

import (
	"crypto/rand"
	"encoding/hex"
	"encoding/json"
	"net/http"
	"strings"
	"time"

	"github.com/go-chi/chi/v5"
	"github.com/kindredsystems/silo/internal/auth"
)

// HandleAuthConfig returns public auth configuration for the login page.
func (s *Server) HandleAuthConfig(w http.ResponseWriter, r *http.Request) {
	writeJSON(w, http.StatusOK, map[string]any{
		"oidc_enabled":  s.oidc != nil,
		"local_enabled": s.authConfig != nil && s.authConfig.Local.Enabled,
	})
}

// HandleLoginPage redirects to the SPA (React handles the login UI).
func (s *Server) HandleLoginPage(w http.ResponseWriter, r *http.Request) {
	http.Redirect(w, r, "/", http.StatusSeeOther)
}

// HandleLogin processes the login form submission.
func (s *Server) HandleLogin(w http.ResponseWriter, r *http.Request) {
	if s.authConfig == nil || !s.authConfig.Enabled {
		http.Redirect(w, r, "/", http.StatusSeeOther)
		return
	}

	username := strings.TrimSpace(r.FormValue("username"))
	password := r.FormValue("password")

	if username == "" || password == "" {
		writeError(w, http.StatusBadRequest, "invalid_request", "Username and password are required")
		return
	}

	user, err := s.auth.Authenticate(r.Context(), username, password)
	if err != nil {
		s.logger.Warn().Str("username", username).Err(err).Msg("login failed")
		writeError(w, http.StatusUnauthorized, "invalid_credentials", "Invalid username or password")
		return
	}

	// Create session
	if err := s.sessions.RenewToken(r.Context()); err != nil {
		s.logger.Error().Err(err).Msg("failed to renew session token")
		writeError(w, http.StatusInternalServerError, "internal_error", "Internal error, please try again")
		return
	}
	s.sessions.Put(r.Context(), "user_id", user.ID)
	s.sessions.Put(r.Context(), "username", user.Username)

	s.logger.Info().Str("username", username).Str("source", user.AuthSource).Msg("user logged in")

	// Redirect to original destination or home
	next := r.URL.Query().Get("next")
	if next == "" || !strings.HasPrefix(next, "/") {
		next = "/"
	}
	http.Redirect(w, r, next, http.StatusSeeOther)
}

// HandleLogout destroys the session and redirects to login.
func (s *Server) HandleLogout(w http.ResponseWriter, r *http.Request) {
	if s.sessions != nil {
		_ = s.sessions.Destroy(r.Context())
	}
	http.Redirect(w, r, "/login", http.StatusSeeOther)
}

// HandleOIDCLogin initiates the OIDC redirect to Keycloak.
func (s *Server) HandleOIDCLogin(w http.ResponseWriter, r *http.Request) {
	if s.oidc == nil {
		http.Redirect(w, r, "/login", http.StatusSeeOther)
		return
	}

	state, err := generateRandomState()
	if err != nil {
		s.logger.Error().Err(err).Msg("failed to generate OIDC state")
		http.Redirect(w, r, "/login", http.StatusSeeOther)
		return
	}

	s.sessions.Put(r.Context(), "oidc_state", state)
	http.Redirect(w, r, s.oidc.AuthCodeURL(state), http.StatusSeeOther)
}

// HandleOIDCCallback processes the OIDC redirect from Keycloak.
func (s *Server) HandleOIDCCallback(w http.ResponseWriter, r *http.Request) {
	if s.oidc == nil {
		http.Error(w, "OIDC not configured", http.StatusNotFound)
		return
	}

	// Verify state
	expectedState := s.sessions.GetString(r.Context(), "oidc_state")
	actualState := r.URL.Query().Get("state")
	if expectedState == "" || actualState != expectedState {
		s.logger.Warn().Msg("OIDC state mismatch")
		http.Redirect(w, r, "/login", http.StatusSeeOther)
		return
	}
	s.sessions.Remove(r.Context(), "oidc_state")

	// Check for error from IdP
	if errParam := r.URL.Query().Get("error"); errParam != "" {
		desc := r.URL.Query().Get("error_description")
		s.logger.Warn().Str("error", errParam).Str("description", desc).Msg("OIDC error from IdP")
		http.Redirect(w, r, "/login", http.StatusSeeOther)
		return
	}

	// Exchange code for token
	code := r.URL.Query().Get("code")
	user, err := s.oidc.Exchange(r.Context(), code)
	if err != nil {
		s.logger.Error().Err(err).Msg("OIDC exchange failed")
		http.Redirect(w, r, "/login", http.StatusSeeOther)
		return
	}

	// Upsert user into DB
	if err := s.auth.UpsertOIDCUser(r.Context(), user); err != nil {
		s.logger.Error().Err(err).Msg("failed to upsert OIDC user")
		http.Redirect(w, r, "/login", http.StatusSeeOther)
		return
	}

	// Create session
	if err := s.sessions.RenewToken(r.Context()); err != nil {
		s.logger.Error().Err(err).Msg("failed to renew session token")
		http.Redirect(w, r, "/login", http.StatusSeeOther)
		return
	}
	s.sessions.Put(r.Context(), "user_id", user.ID)
	s.sessions.Put(r.Context(), "username", user.Username)

	s.logger.Info().Str("username", user.Username).Msg("OIDC user logged in")
	http.Redirect(w, r, "/", http.StatusSeeOther)
}

// HandleGetCurrentUser returns the authenticated user as JSON.
func (s *Server) HandleGetCurrentUser(w http.ResponseWriter, r *http.Request) {
	user := auth.UserFromContext(r.Context())
	if user == nil {
		writeError(w, http.StatusUnauthorized, "unauthorized", "Not authenticated")
		return
	}
	writeJSON(w, http.StatusOK, map[string]any{
		"id":           user.ID,
		"username":     user.Username,
		"display_name": user.DisplayName,
		"email":        user.Email,
		"role":         user.Role,
		"auth_source":  user.AuthSource,
	})
}

// createTokenRequest is the request body for token creation.
type createTokenRequest struct {
	Name          string `json:"name"`
	ExpiresInDays *int   `json:"expires_in_days,omitempty"`
}

// HandleCreateToken creates a new API token (JSON API).
func (s *Server) HandleCreateToken(w http.ResponseWriter, r *http.Request) {
	user := auth.UserFromContext(r.Context())
	if user == nil {
		writeError(w, http.StatusUnauthorized, "unauthorized", "Not authenticated")
		return
	}

	var req createTokenRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid_request", "Invalid JSON body")
		return
	}
	if req.Name == "" {
		writeError(w, http.StatusBadRequest, "invalid_request", "Token name is required")
		return
	}

	var expiresAt *time.Time
	if req.ExpiresInDays != nil && *req.ExpiresInDays > 0 {
		t := time.Now().AddDate(0, 0, *req.ExpiresInDays)
		expiresAt = &t
	}

	rawToken, info, err := s.auth.GenerateToken(r.Context(), user.ID, req.Name, nil, expiresAt)
	if err != nil {
		s.logger.Error().Err(err).Msg("failed to generate token")
		writeError(w, http.StatusInternalServerError, "internal_error", "Failed to create token")
		return
	}

	writeJSON(w, http.StatusCreated, map[string]any{
		"token":        rawToken,
		"id":           info.ID,
		"name":         info.Name,
		"token_prefix": info.TokenPrefix,
		"expires_at":   info.ExpiresAt,
		"created_at":   info.CreatedAt,
	})
}

// HandleListTokens lists all tokens for the current user.
func (s *Server) HandleListTokens(w http.ResponseWriter, r *http.Request) {
	user := auth.UserFromContext(r.Context())
	if user == nil {
		writeError(w, http.StatusUnauthorized, "unauthorized", "Not authenticated")
		return
	}

	tokens, err := s.auth.ListTokens(r.Context(), user.ID)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "internal_error", "Failed to list tokens")
		return
	}

	type tokenResponse struct {
		ID          string     `json:"id"`
		Name        string     `json:"name"`
		TokenPrefix string     `json:"token_prefix"`
		LastUsedAt  *time.Time `json:"last_used_at,omitempty"`
		ExpiresAt   *time.Time `json:"expires_at,omitempty"`
		CreatedAt   time.Time  `json:"created_at"`
	}

	result := make([]tokenResponse, 0, len(tokens))
	for _, t := range tokens {
		result = append(result, tokenResponse{
			ID:          t.ID,
			Name:        t.Name,
			TokenPrefix: t.TokenPrefix,
			LastUsedAt:  t.LastUsedAt,
			ExpiresAt:   t.ExpiresAt,
			CreatedAt:   t.CreatedAt,
		})
	}

	writeJSON(w, http.StatusOK, result)
}

// HandleRevokeToken deletes an API token (JSON API).
func (s *Server) HandleRevokeToken(w http.ResponseWriter, r *http.Request) {
	user := auth.UserFromContext(r.Context())
	if user == nil {
		writeError(w, http.StatusUnauthorized, "unauthorized", "Not authenticated")
		return
	}

	tokenID := chi.URLParam(r, "id")
	if err := s.auth.RevokeToken(r.Context(), user.ID, tokenID); err != nil {
		writeError(w, http.StatusNotFound, "not_found", "Token not found")
		return
	}

	w.WriteHeader(http.StatusNoContent)
}

func generateRandomState() (string, error) {
	b := make([]byte, 16)
	if _, err := rand.Read(b); err != nil {
		return "", err
	}
	return hex.EncodeToString(b), nil
}