package service

import (
	"context"
	"encoding/json"
	"io"
	"net/http"
	"reflect"
	"strconv"

	"github.com/fleetdm/fleet/v4/server/activity/api"
	"github.com/fleetdm/fleet/v4/server/contexts/ctxerr"
	eu "github.com/fleetdm/fleet/v4/server/platform/endpointer"
	platform_http "github.com/fleetdm/fleet/v4/server/platform/http"
	"github.com/go-kit/kit/endpoint"
	kithttp "github.com/go-kit/kit/transport/http"
	"github.com/gorilla/mux"
)

const (
	// defaultPerPage is used when per_page is not specified but page is specified.
	defaultPerPage = 20

	// unlimitedPerPage is used when neither page nor per_page is specified,
	// effectively returning all results (legacy behavior for backwards compatibility).
	unlimitedPerPage = 1000000
)

// encodeResponse encodes the response as JSON.
func encodeResponse(ctx context.Context, w http.ResponseWriter, response any) error {
	return eu.EncodeCommonResponse(ctx, w, response,
		func(w http.ResponseWriter, response any) error {
			enc := json.NewEncoder(w)
			enc.SetIndent("", "  ")
			return enc.Encode(response)
		},
		nil, // no domain-specific error encoder
	)
}

// makeDecoder creates a decoder for the given request type.
func makeDecoder(iface any, requestBodySizeLimit int64) kithttp.DecodeRequestFunc {
	return eu.MakeDecoder(iface, func(body io.Reader, req any) error {
		return json.NewDecoder(body).Decode(req)
	}, parseCustomTags, nil, nil, nil, requestBodySizeLimit)
}

// parseCustomTags handles custom URL tag values for activity requests.
func parseCustomTags(urlTagValue string, r *http.Request, field reflect.Value) (bool, error) {
	if urlTagValue == "list_options" {
		opts, err := listOptionsFromRequest(r)
		if err != nil {
			return false, err
		}
		field.Set(reflect.ValueOf(opts))
		return true, nil
	}
	return false, nil
}

// listOptionsFromRequest parses list options from query parameters.
func listOptionsFromRequest(r *http.Request) (api.ListOptions, error) {
	q := r.URL.Query()

	var page int
	if val := q.Get("page"); val != "" {
		var err error
		page, err = strconv.Atoi(val)
		if err != nil {
			return api.ListOptions{}, ctxerr.Wrap(r.Context(), &platform_http.BadRequestError{Message: "non-int page value"})
		}
		if page < 0 {
			return api.ListOptions{}, ctxerr.Wrap(r.Context(), &platform_http.BadRequestError{Message: "negative page value"})
		}
	}

	var perPage int
	if val := q.Get("per_page"); val != "" {
		var err error
		perPage, err = strconv.Atoi(val)
		if err != nil {
			return api.ListOptions{}, ctxerr.Wrap(r.Context(), &platform_http.BadRequestError{Message: "non-int per_page value"})
		}
		if perPage <= 0 {
			return api.ListOptions{}, ctxerr.Wrap(r.Context(), &platform_http.BadRequestError{Message: "invalid per_page value"})
		}
	}

	orderKey := q.Get("order_key")
	orderDirectionString := q.Get("order_direction")
	if orderKey == "" && orderDirectionString != "" {
		return api.ListOptions{}, ctxerr.Wrap(r.Context(), &platform_http.BadRequestError{Message: "order_key must be specified with order_direction"})
	}

	var orderDirection api.OrderDirection
	switch orderDirectionString {
	case "desc":
		orderDirection = api.OrderDescending
	case "asc", "":
		orderDirection = api.OrderAscending
	default:
		return api.ListOptions{}, ctxerr.Wrap(r.Context(), &platform_http.BadRequestError{Message: "unknown order_direction: " + orderDirectionString})
	}

	return api.ListOptions{
		Page:           uint(page),    //nolint:gosec // dismiss G115
		PerPage:        uint(perPage), //nolint:gosec // dismiss G115
		OrderKey:       orderKey,
		OrderDirection: orderDirection,
		After:          q.Get("after"),
		ActivityType:   q.Get("activity_type"),
		StartCreatedAt: q.Get("start_created_at"),
		EndCreatedAt:   q.Get("end_created_at"),
		MatchQuery:     q.Get("query"),
	}, nil
}

// handlerFunc is the handler function type for Activity service endpoints.
type handlerFunc func(ctx context.Context, request any, svc api.Service) platform_http.Errorer

// Compile-time check to ensure endpointer implements Endpointer.
var _ eu.Endpointer[handlerFunc] = &endpointer{}

type endpointer struct {
	svc api.Service
}

func (e *endpointer) CallHandlerFunc(f handlerFunc, ctx context.Context,
	request any,
	svc any,
) (platform_http.Errorer, error) {
	return f(ctx, request, svc.(api.Service)), nil
}

func (e *endpointer) Service() any {
	return e.svc
}

func newUserAuthenticatedEndpointer(svc api.Service, authMiddleware endpoint.Middleware, opts []kithttp.ServerOption, r *mux.Router,
	versions ...string,
) *eu.CommonEndpointer[handlerFunc] {
	return &eu.CommonEndpointer[handlerFunc]{
		EP: &endpointer{
			svc: svc,
		},
		MakeDecoderFn:  makeDecoder,
		EncodeFn:       encodeResponse,
		Opts:           opts,
		AuthMiddleware: authMiddleware,
		Router:         r,
		Versions:       versions,
	}
}