package api

import (
	"context"
	"encoding/json"
	"errors"
	"net/http"
	"os"
	"strings"
	"sync"
	"time"

	"codeberg.org/SquidSE/ClusterCanvas/service/internal/auth"
	"codeberg.org/SquidSE/ClusterCanvas/service/internal/runner"
	"codeberg.org/SquidSE/ClusterCanvas/service/internal/settings"
)

type contextKey string

const (
	contextUserKey    contextKey = "user"
	contextSessionKey contextKey = "session"
)

type setupStatusResponse struct {
	Completed bool   `json:"completed"`
	ClientIP  string `json:"client_ip"`
}

type setupTOTPBeginRequest struct {
	Username string `json:"username"`
}

type setupTOTPBeginResponse struct {
	Secret    string `json:"secret"`
	OTPAuthURL string `json:"otpauth_url"`
}

type setupTOTPVerifyRequest struct {
	Secret string `json:"secret"`
	Code   string `json:"code"`
}

type setupCompleteRequest struct {
	Username      string                    `json:"username"`
	Password      string                    `json:"password"`
	TOTPSecret    string                    `json:"totp_secret"`
	TOTPConfirmed bool                      `json:"totp_confirmed"`
	Network       settings.NetworkSettings  `json:"network"`
	Security      settings.SecuritySettings `json:"security"`
}

type setupPreviewRequest struct {
	Network settings.NetworkSettings `json:"network"`
}

type setupPreviewResponse struct {
	WouldLockOut bool   `json:"would_lock_out"`
	Reason       string `json:"reason,omitempty"`
	ClientIP     string `json:"client_ip"`
}

type loginRequest struct {
	Username string `json:"username"`
	Password string `json:"password"`
	TOTPCode string `json:"totp_code"`
}

type meResponse struct {
	UserID        string   `json:"user_id"`
	Username      string   `json:"username"`
	Groups        []string `json:"groups"`
	TOTPConfirmed bool     `json:"totp_confirmed"`
	TOTPEnabled   bool     `json:"totp_enabled"`
	Permissions   []string `json:"permissions"`
}

// App holds shared API dependencies.
type App struct {
	ConfigDir string
	Key       []byte
	Sessions  *auth.SessionManager
	Executor  *runner.Executor

	pendingTOTPMu sync.Mutex
	pendingTOTP   map[string]string // username -> secret (setup only)
}

func newApp(configDir string) (*App, error) {
	key, err := settings.KeyFromEnv()
	if err != nil {
		// Key is required for setup complete / auth; status still works without it.
		app := &App{
			ConfigDir:   configDir,
			pendingTOTP: map[string]string{},
			Executor:    runner.NewExecutor(configDir, nil),
		}
		return app, nil
	}
	app := &App{
		ConfigDir:   configDir,
		Key:         key,
		Sessions:    auth.NewSessionManager(configDir, key),
		pendingTOTP: map[string]string{},
		Executor:    runner.NewExecutor(configDir, key),
	}
	return app, nil
}

func (app *App) requireKey() error {
	if len(app.Key) == 0 {
		return fmtErrorfKeyMissing()
	}
	return nil
}

func fmtErrorfKeyMissing() error {
	return errors.New(settings.ConfigKeyEnvVar + " is not set")
}

func (app *App) setupStatusHandler(writer http.ResponseWriter, request *http.Request) {
	completed, err := settings.IsSetupCompleted(app.ConfigDir)
	if err != nil {
		writeJSON(writer, http.StatusInternalServerError, apiErrorResponse{Error: err.Error()})
		return
	}
	writeJSON(writer, http.StatusOK, setupStatusResponse{
		Completed: completed,
		ClientIP:  auth.ClientIP(request),
	})
}

func (app *App) setupTOTPBeginHandler(writer http.ResponseWriter, request *http.Request) {
	completed, err := settings.IsSetupCompleted(app.ConfigDir)
	if err != nil {
		writeJSON(writer, http.StatusInternalServerError, apiErrorResponse{Error: err.Error()})
		return
	}
	if completed {
		writeJSON(writer, http.StatusConflict, apiErrorResponse{Error: "setup already completed"})
		return
	}

	var payload setupTOTPBeginRequest
	if err := json.NewDecoder(request.Body).Decode(&payload); err != nil {
		writeJSON(writer, http.StatusBadRequest, apiErrorResponse{Error: "invalid JSON body"})
		return
	}
	username := strings.TrimSpace(payload.Username)
	if username == "" {
		username = "Admin"
	}

	key, err := auth.GenerateTOTPSecret(username)
	if err != nil {
		writeJSON(writer, http.StatusInternalServerError, apiErrorResponse{Error: err.Error()})
		return
	}

	app.pendingTOTPMu.Lock()
	app.pendingTOTP[strings.ToLower(username)] = key.Secret()
	app.pendingTOTPMu.Unlock()

	writeJSON(writer, http.StatusOK, setupTOTPBeginResponse{
		Secret:     key.Secret(),
		OTPAuthURL: key.URL(),
	})
}

func (app *App) setupTOTPVerifyHandler(writer http.ResponseWriter, request *http.Request) {
	completed, err := settings.IsSetupCompleted(app.ConfigDir)
	if err != nil {
		writeJSON(writer, http.StatusInternalServerError, apiErrorResponse{Error: err.Error()})
		return
	}
	if completed {
		writeJSON(writer, http.StatusConflict, apiErrorResponse{Error: "setup already completed"})
		return
	}

	var payload setupTOTPVerifyRequest
	if err := json.NewDecoder(request.Body).Decode(&payload); err != nil {
		writeJSON(writer, http.StatusBadRequest, apiErrorResponse{Error: "invalid JSON body"})
		return
	}
	if !auth.VerifyTOTPCode(payload.Secret, payload.Code) {
		writeJSON(writer, http.StatusBadRequest, apiErrorResponse{Error: "invalid TOTP code"})
		return
	}
	writeJSON(writer, http.StatusOK, map[string]bool{"verified": true})
}

func (app *App) setupPreviewHandler(writer http.ResponseWriter, request *http.Request) {
	var payload setupPreviewRequest
	if err := json.NewDecoder(request.Body).Decode(&payload); err != nil {
		writeJSON(writer, http.StatusBadRequest, apiErrorResponse{Error: "invalid JSON body"})
		return
	}
	clientIP := auth.ClientIP(request)
	wouldLockOut, reason := auth.WouldLockOut(clientIP, payload.Network)
	writeJSON(writer, http.StatusOK, setupPreviewResponse{
		WouldLockOut: wouldLockOut,
		Reason:       reason,
		ClientIP:     clientIP,
	})
}

func (app *App) setupCompleteHandler(writer http.ResponseWriter, request *http.Request) {
	if err := app.requireKey(); err != nil {
		writeJSON(writer, http.StatusServiceUnavailable, apiErrorResponse{Error: err.Error()})
		return
	}

	completed, err := settings.IsSetupCompleted(app.ConfigDir)
	if err != nil {
		writeJSON(writer, http.StatusInternalServerError, apiErrorResponse{Error: err.Error()})
		return
	}
	if completed {
		writeJSON(writer, http.StatusConflict, apiErrorResponse{Error: "setup already completed"})
		return
	}

	var payload setupCompleteRequest
	if err := json.NewDecoder(request.Body).Decode(&payload); err != nil {
		writeJSON(writer, http.StatusBadRequest, apiErrorResponse{Error: "invalid JSON body"})
		return
	}

	username := strings.TrimSpace(payload.Username)
	if username == "" {
		username = "Admin"
	}
	if err := auth.ValidatePassword(payload.Password, username); err != nil {
		writeJSON(writer, http.StatusBadRequest, apiErrorResponse{Error: err.Error()})
		return
	}
	if err := auth.ValidateListenAddress(payload.Network.ListenAddress); err != nil {
		writeJSON(writer, http.StatusBadRequest, apiErrorResponse{Error: err.Error()})
		return
	}
	if err := auth.ValidateHostname(payload.Network.PublicHostname); err != nil {
		writeJSON(writer, http.StatusBadRequest, apiErrorResponse{Error: err.Error()})
		return
	}
	if err := auth.ValidateAccessRules(payload.Network.Rules); err != nil {
		writeJSON(writer, http.StatusBadRequest, apiErrorResponse{Error: err.Error()})
		return
	}
	switch payload.Network.AccessMode {
	case settings.AccessModeOpen, settings.AccessModeWhitelist, settings.AccessModeBlacklist:
	default:
		writeJSON(writer, http.StatusBadRequest, apiErrorResponse{Error: "network.access_mode must be open, whitelist, or blacklist"})
		return
	}
	if err := validateSecuritySettings(payload.Security); err != nil {
		writeJSON(writer, http.StatusBadRequest, apiErrorResponse{Error: err.Error()})
		return
	}

	if payload.TOTPConfirmed {
		if strings.TrimSpace(payload.TOTPSecret) == "" {
			writeJSON(writer, http.StatusBadRequest, apiErrorResponse{Error: "totp_secret is required when totp_confirmed is true"})
			return
		}
		payload.Security.TotpEnabled = true
	}

	passwordHash, err := auth.HashPassword(payload.Password)
	if err != nil {
		writeJSON(writer, http.StatusInternalServerError, apiErrorResponse{Error: err.Error()})
		return
	}

	now := time.Now().UTC()
	userID, err := newUserID()
	if err != nil {
		writeJSON(writer, http.StatusInternalServerError, apiErrorResponse{Error: err.Error()})
		return
	}

	user := settings.UserCredential{
		ID:                userID,
		Username:          username,
		PasswordHash:      passwordHash,
		TOTPSecret:        payload.TOTPSecret,
		TOTPConfirmed:     payload.TOTPConfirmed,
		Enabled:           true,
		GroupNames:        []string{settings.AdministratorsGroupName},
		CreatedAt:         now,
		PasswordChangedAt: now,
	}

	passwordStore := settings.PasswordStore{Users: []settings.UserCredential{user}}
	if err := settings.SavePasswords(app.ConfigDir, passwordStore, app.Key); err != nil {
		writeJSON(writer, http.StatusInternalServerError, apiErrorResponse{Error: err.Error()})
		return
	}

	if err := settings.SaveSessions(app.ConfigDir, settings.SessionStore{Sessions: []settings.SessionRecord{}}, app.Key); err != nil {
		writeJSON(writer, http.StatusInternalServerError, apiErrorResponse{Error: err.Error()})
		return
	}

	adminGroup := settings.Group{
		Name:        settings.AdministratorsGroupName,
		ScopeKind:   settings.GroupScopeGroup,
		ScopeName:   "Admin Group",
		Permissions: allPermissionList(),
	}

	network := settings.EffectiveNetwork(payload.Network)
	settingsPayload := settings.Settings{
		SetupCompleted: true,
		Groups:         []settings.Group{adminGroup},
		Security:       payload.Security,
		Network:        network,
	}
	if err := settings.SaveSettings(app.ConfigDir, settingsPayload); err != nil {
		writeJSON(writer, http.StatusInternalServerError, apiErrorResponse{Error: err.Error()})
		return
	}

	writeJSON(writer, http.StatusOK, map[string]any{
		"completed": true,
		"username":  username,
	})
}

func (app *App) loginHandler(writer http.ResponseWriter, request *http.Request) {
	if err := app.requireKey(); err != nil {
		writeJSON(writer, http.StatusServiceUnavailable, apiErrorResponse{Error: err.Error()})
		return
	}
	if app.Sessions == nil {
		app.Sessions = auth.NewSessionManager(app.ConfigDir, app.Key)
	}

	completed, err := settings.IsSetupCompleted(app.ConfigDir)
	if err != nil {
		writeJSON(writer, http.StatusInternalServerError, apiErrorResponse{Error: err.Error()})
		return
	}
	if !completed {
		writeJSON(writer, http.StatusConflict, apiErrorResponse{Error: "setup is not completed"})
		return
	}

	var payload loginRequest
	if err := json.NewDecoder(request.Body).Decode(&payload); err != nil {
		writeJSON(writer, http.StatusBadRequest, apiErrorResponse{Error: "invalid JSON body"})
		return
	}

	store, err := settings.LoadPasswords(app.ConfigDir, app.Key)
	if err != nil {
		writeJSON(writer, http.StatusInternalServerError, apiErrorResponse{Error: err.Error()})
		return
	}

	var matched *settings.UserCredential
	for index := range store.Users {
		user := &store.Users[index]
		if strings.EqualFold(user.Username, strings.TrimSpace(payload.Username)) {
			matched = user
			break
		}
	}
	attemptedUsername := strings.TrimSpace(payload.Username)
	if matched == nil || !matched.Enabled {
		appendAuthAudit(
			app.ConfigDir,
			"login",
			settings.AuthAuditOutcomeFailure,
			settings.AuthAuditCategoryAuth,
			attemptedUsername,
			attemptedUsername,
			"invalid credentials",
		)
		writeJSON(writer, http.StatusUnauthorized, apiErrorResponse{Error: "invalid credentials"})
		return
	}

	ok, err := auth.VerifyPassword(payload.Password, matched.PasswordHash)
	if err != nil || !ok {
		appendAuthAudit(
			app.ConfigDir,
			"login",
			settings.AuthAuditOutcomeFailure,
			settings.AuthAuditCategoryAuth,
			attemptedUsername,
			matched.Username,
			"invalid credentials",
		)
		writeJSON(writer, http.StatusUnauthorized, apiErrorResponse{Error: "invalid credentials"})
		return
	}

	settingsPayload, err := loadSettingsOrDefault(app.ConfigDir)
	if err != nil {
		writeJSON(writer, http.StatusInternalServerError, apiErrorResponse{Error: err.Error()})
		return
	}
	security := effectiveSecurity(settingsPayload.Security)

	requiresTOTP := security.TotpEnabled && matched.TOTPConfirmed && matched.TOTPSecret != ""
	if requiresTOTP {
		if !auth.VerifyTOTPCode(matched.TOTPSecret, payload.TOTPCode) {
			appendAuthAudit(
				app.ConfigDir,
				"login",
				settings.AuthAuditOutcomeFailure,
				settings.AuthAuditCategoryAuth,
				matched.Username,
				matched.Username,
				"invalid or missing TOTP code",
			)
			writeJSON(writer, http.StatusUnauthorized, apiErrorResponse{Error: "invalid or missing TOTP code"})
			return
		}
	}

	if _, err := app.Sessions.CreateSession(writer, matched.ID, security); err != nil {
		writeJSON(writer, http.StatusInternalServerError, apiErrorResponse{Error: err.Error()})
		return
	}

	appendAuthAudit(
		app.ConfigDir,
		"login",
		settings.AuthAuditOutcomeSuccess,
		settings.AuthAuditCategoryAuth,
		matched.Username,
		matched.Username,
		"",
	)
	writeJSON(writer, http.StatusOK, app.buildMeResponse(*matched, settingsPayload))
}

func (app *App) logoutHandler(writer http.ResponseWriter, request *http.Request) {
	actor := actorUsernameFromRequest(request)
	if app.Sessions != nil {
		_ = app.Sessions.DestroySession(writer, request)
	}
	if actor != "" {
		appendAuthAudit(
			app.ConfigDir,
			"logout",
			settings.AuthAuditOutcomeSuccess,
			settings.AuthAuditCategoryAuth,
			actor,
			actor,
			"",
		)
	}
	writeJSON(writer, http.StatusOK, map[string]bool{"ok": true})
}

func (app *App) meHandler(writer http.ResponseWriter, request *http.Request) {
	user, ok := UserFromContext(request.Context())
	if !ok {
		writeJSON(writer, http.StatusUnauthorized, apiErrorResponse{Error: "not authenticated"})
		return
	}
	settingsPayload, err := loadSettingsOrDefault(app.ConfigDir)
	if err != nil {
		writeJSON(writer, http.StatusInternalServerError, apiErrorResponse{Error: err.Error()})
		return
	}
	writeJSON(writer, http.StatusOK, app.buildMeResponse(user, settingsPayload))
}

func (app *App) buildMeResponse(user settings.UserCredential, settingsPayload settings.Settings) meResponse {
	security := effectiveSecurity(settingsPayload.Security)
	groups := user.GroupNames
	if groups == nil {
		groups = []string{}
	}
	permissions := permissionList(user, settingsPayload.Groups)
	if permissions == nil {
		permissions = []string{}
	}
	return meResponse{
		UserID:        user.ID,
		Username:      user.Username,
		Groups:        groups,
		TOTPConfirmed: user.TOTPConfirmed,
		TOTPEnabled:   security.TotpEnabled,
		Permissions:   permissions,
	}
}

func UserFromContext(ctx context.Context) (settings.UserCredential, bool) {
	user, ok := ctx.Value(contextUserKey).(settings.UserCredential)
	return user, ok
}

func allPermissionList() []string {
	list := make([]string, 0, len(allowedPermissions))
	for permission := range allowedPermissions {
		list = append(list, permission)
	}
	// Stable-ish order for tests: sort manually via known catalog order.
	ordered := []string{
		"nodes.read",
		"nodes.exec",
		"nodes.update",
		"nodes.delete",
		"jobs.read",
		"jobs.run",
		"actions.create",
		"actions.update",
		"actions.delete",
		"users.manage",
		"secrets.manage",
		"roles.manage",
		"logs.read",
	}
	_ = list
	return ordered
}

func newUserID() (string, error) {
	return auth.NewRandomID()
}

func loadSettingsOrDefault(configDir string) (settings.Settings, error) {
	payload, err := settings.LoadSettings(configDir)
	if err != nil {
		if errors.Is(err, os.ErrNotExist) {
			return settings.Settings{
				Groups:   []settings.Group{},
				Security: settings.DefaultSecuritySettings(),
				Network:  settings.DefaultNetworkSettings(),
			}, nil
		}
		return settings.Settings{}, err
	}
	if payload.Groups == nil {
		payload.Groups = []settings.Group{}
	}
	payload.Network = settings.EffectiveNetwork(payload.Network)
	if migrateLogsReadPermission(&payload) {
		if err := settings.SaveSettings(configDir, payload); err != nil {
			return settings.Settings{}, err
		}
	}
	return payload, nil
}

// migrateLogsReadPermission grants logs.read to groups that previously could
// view logs via nodes.read or users.manage. Returns true when settings changed.
func migrateLogsReadPermission(payload *settings.Settings) bool {
	changed := false
	for index := range payload.Groups {
		group := &payload.Groups[index]
		hasLogsRead := false
		hadLogAccess := false
		for _, permission := range group.Permissions {
			switch permission {
			case "logs.read":
				hasLogsRead = true
			case "nodes.read", "users.manage":
				hadLogAccess = true
			}
		}
		if hasLogsRead || !hadLogAccess {
			continue
		}
		group.Permissions = append(group.Permissions, "logs.read")
		changed = true
	}
	return changed
}