package api

import (
	"encoding/json"
	"errors"
	"net/http"
	"os"
	"strings"

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

type groupsResponse struct {
	Groups []settings.Group `json:"groups"`
}

type apiErrorResponse struct {
	Error string `json:"error"`
}

type upsertGroupRequest struct {
	Group settings.Group `json:"group"`
}

var allowedPermissions = map[string]struct{}{
	"nodes.read":      {},
	"nodes.exec":      {},
	"nodes.update":    {},
	"jobs.read":       {},
	"jobs.run":        {},
	"users.manage":    {},
	"secrets.manage":  {},
	"roles.manage":    {},
}

func groupsGetHandler(configDir string) http.HandlerFunc {
	return func(writer http.ResponseWriter, request *http.Request) {
		settingsPayload, err := loadSettingsOrDefault(configDir)
		if err != nil {
			writeJSON(writer, http.StatusInternalServerError, apiErrorResponse{Error: err.Error()})
			return
		}

		writeJSON(writer, http.StatusOK, groupsResponse{Groups: settingsPayload.Groups})
	}
}

func groupsUpsertHandler(configDir string) http.HandlerFunc {
	return func(writer http.ResponseWriter, request *http.Request) {
		if err := authorizeGroupsWrite(request); err != nil {
			writeJSON(writer, http.StatusForbidden, apiErrorResponse{Error: err.Error()})
			return
		}

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

		if err := validateGroup(payload.Group); err != nil {
			writeJSON(writer, http.StatusBadRequest, apiErrorResponse{Error: err.Error()})
			return
		}

		settingsPayload, err := loadSettingsOrDefault(configDir)
		if err != nil {
			writeJSON(writer, http.StatusInternalServerError, apiErrorResponse{Error: err.Error()})
			return
		}

		updated := false
		for index := range settingsPayload.Groups {
			if settingsPayload.Groups[index].Name == payload.Group.Name {
				settingsPayload.Groups[index] = payload.Group
				updated = true
				break
			}
		}
		if !updated {
			settingsPayload.Groups = append(settingsPayload.Groups, payload.Group)
		}

		if err := settings.SaveSettings(configDir, settingsPayload); err != nil {
			writeJSON(writer, http.StatusInternalServerError, apiErrorResponse{Error: err.Error()})
			return
		}

		writeJSON(writer, http.StatusOK, groupsResponse{Groups: settingsPayload.Groups})
	}
}

func groupsDeleteHandler(configDir string) http.HandlerFunc {
	return func(writer http.ResponseWriter, request *http.Request) {
		if err := authorizeGroupsWrite(request); err != nil {
			writeJSON(writer, http.StatusForbidden, apiErrorResponse{Error: err.Error()})
			return
		}

		name := strings.TrimSpace(request.URL.Query().Get("name"))
		if name == "" {
			writeJSON(writer, http.StatusBadRequest, apiErrorResponse{Error: "missing group name"})
			return
		}

		settingsPayload, err := loadSettingsOrDefault(configDir)
		if err != nil {
			writeJSON(writer, http.StatusInternalServerError, apiErrorResponse{Error: err.Error()})
			return
		}

		remaining := make([]settings.Group, 0, len(settingsPayload.Groups))
		for _, group := range settingsPayload.Groups {
			if group.Name != name {
				remaining = append(remaining, group)
			}
		}

		if len(remaining) == len(settingsPayload.Groups) {
			writeJSON(writer, http.StatusNotFound, apiErrorResponse{Error: "group not found"})
			return
		}

		settingsPayload.Groups = remaining
		if err := settings.SaveSettings(configDir, settingsPayload); err != nil {
			writeJSON(writer, http.StatusInternalServerError, apiErrorResponse{Error: err.Error()})
			return
		}

		writeJSON(writer, http.StatusOK, groupsResponse{Groups: settingsPayload.Groups})
	}
}

func authorizeGroupsWrite(_ *http.Request) error {
	// TODO: integrate authz middleware.
	return nil
}

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{}}, nil
		}
		return settings.Settings{}, err
	}
	if payload.Groups == nil {
		payload.Groups = []settings.Group{}
	}
	return payload, nil
}

func validateGroup(group settings.Group) error {
	if strings.TrimSpace(group.Name) == "" {
		return errors.New("group.name is required")
	}

	switch group.ScopeKind {
	case settings.GroupScopeNode, settings.GroupScopeGroup:
		// ok
	default:
		return errors.New("group.scope_kind must be \"node\" or \"group\"")
	}

	if strings.TrimSpace(group.ScopeName) == "" {
		return errors.New("group.scope_name is required")
	}

	if len(group.Permissions) == 0 {
		return errors.New("group.permissions must be non-empty")
	}

	for _, permission := range group.Permissions {
		if strings.TrimSpace(permission) == "" {
			return errors.New("permission strings must be non-empty")
		}
		if _, ok := allowedPermissions[permission]; !ok {
			return errors.New("permission is not in the built-in permission catalog")
		}
	}

	return nil
}