package api

import (
	"context"
	"encoding/json"
	"errors"
	"io"
	"net/http"
	"strconv"
	"strings"

	"bat-api/internal/backendrpc"
)

const adminControlMaxBodyBytes = 1024
const adminScheduleMaxBodyBytes = 64 * 1024

type adminControlRequest struct {
	Force bool `json:"force"`
}

func (s *Server) handleAdminIndex(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet && r.Method != http.MethodHead {
		writeErrorJSON(w, http.StatusMethodNotAllowed, "method_not_allowed", "method not allowed")
		return
	}
	body := AdminIndexResponse{
		Service: "bat-api",
		Panel:   "admin",
		Status:  "available",
		Links: []string{
			"/healthz",
			"/readyz",
			"/v1/bootstrap",
			"/v1/release",
			"/v1/resources",
			"/openapi.yaml",
			"/admin/schedules",
		},
		Controls: []string{
			"/admin/control/reload",
			"/admin/control/refresh",
			"/admin/control/restart",
			"/admin/control/sync",
			"/admin/control/verify",
			"/admin/control/repair",
			"/admin/control/catalog-refresh",
			"/admin/control/schedule-add",
			"/admin/control/schedule-update",
			"/admin/control/schedule-remove",
			"/admin/control/schedule-run",
			"/admin/control/translation-task-update",
		},
	}
	if r.Method == http.MethodHead {
		w.Header().Set("Cache-Control", "no-store")
		w.WriteHeader(http.StatusOK)
		return
	}
	writeNoStoreJSON(w, http.StatusOK, body)
}

func (s *Server) handleAdminControl(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		writeErrorJSON(w, http.StatusMethodNotAllowed, "method_not_allowed", "method not allowed")
		return
	}
	if !s.requireAdminToken(w, r) {
		return
	}
	action := strings.TrimPrefix(r.URL.Path, "/admin/control/")
	if action == "" || strings.Contains(action, "/") {
		writeErrorJSON(w, http.StatusNotFound, "control_not_found", "unknown control action")
		return
	}
	if strings.HasPrefix(action, "schedule-") {
		s.handleAdminScheduleControl(w, r, action)
		return
	}
	if action == "translation-task-update" {
		s.handleAdminTranslationTaskUpdate(w, r)
		return
	}
	request, ok := decodeAdminControlRequest(w, r)
	if !ok {
		return
	}
	backend, ok := s.backend.(ControlBackend)
	if !ok || backend == nil {
		writeErrorJSON(w, http.StatusServiceUnavailable, "control_backend_unavailable", "Rust bat control backend is unavailable")
		return
	}

	var (
		method string
		result any
		err    error
	)
	switch action {
	case "reload":
		if request.Force {
			writeErrorJSON(w, http.StatusBadRequest, "invalid_control_params", "reload does not accept force")
			return
		}
		method = "daemon.reload"
		result, err = backend.DaemonReload(r.Context())
	case "refresh":
		method = "daemon.refresh"
		result, err = backend.DaemonRefresh(r.Context(), request.Force)
	case "restart":
		if request.Force {
			writeErrorJSON(w, http.StatusBadRequest, "invalid_control_params", "restart does not accept force")
			return
		}
		method = "daemon.restart"
		result, err = backend.DaemonRestart(r.Context())
	case "sync":
		method = "resource.sync"
		result, err = backend.ResourceSync(r.Context(), request.Force)
	case "verify":
		if request.Force {
			writeErrorJSON(w, http.StatusBadRequest, "invalid_control_params", "verify does not accept force")
			return
		}
		method = "resource.verify"
		result, err = backend.ResourceVerify(r.Context())
	case "repair":
		if request.Force {
			writeErrorJSON(w, http.StatusBadRequest, "invalid_control_params", "repair does not accept force")
			return
		}
		method = "resource.repair"
		result, err = backend.ResourceRepair(r.Context())
	case "catalog-refresh":
		method = "catalog.refresh"
		result, err = backend.CatalogRefresh(r.Context(), request.Force)
	case "stop", "clean-stable":
		writeErrorJSON(w, http.StatusForbidden, "control_not_allowed", "control action is not exposed by bat-api")
		return
	default:
		writeErrorJSON(w, http.StatusNotFound, "control_not_found", "unknown control action")
		return
	}
	if err != nil {
		s.writeControlBackendError(w, action, err)
		return
	}
	writeNoStoreJSON(w, http.StatusAccepted, AdminControlResponse{
		Service:   "bat-api",
		Action:    action,
		RPCMethod: method,
		Status:    "accepted",
		Result:    result,
	})
}

func (s *Server) handleAdminTranslationTaskUpdate(w http.ResponseWriter, r *http.Request) {
	backend, ok := s.backend.(TranslationBackend)
	if !ok || backend == nil {
		writeErrorJSON(w, http.StatusServiceUnavailable, "translation_backend_unavailable", "Rust bat translation backend is unavailable")
		return
	}
	var params backendrpc.TranslationTaskUpdateParams
	if !decodeAdminTranslationJSON(w, r, &params) {
		return
	}
	if strings.TrimSpace(params.TaskID) == "" || strings.TrimSpace(params.Status) == "" {
		writeErrorJSON(w, http.StatusBadRequest, "invalid_translation_params", "translation task update requires task_id and status")
		return
	}
	result, err := backend.TranslationTaskUpdate(r.Context(), params)
	if err != nil {
		s.writeControlBackendError(w, "translation-task-update", err)
		return
	}
	writeNoStoreJSON(w, http.StatusAccepted, AdminControlResponse{
		Service:   "bat-api",
		Action:    "translation-task-update",
		RPCMethod: "translation.task.update",
		Status:    "accepted",
		Result:    result,
	})
}

func (s *Server) handleAdminSchedules(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet && r.Method != http.MethodHead {
		writeErrorJSON(w, http.StatusMethodNotAllowed, "method_not_allowed", "method not allowed")
		return
	}
	if !s.requireAdminToken(w, r) {
		return
	}
	backend, ok := s.backend.(ScheduleBackend)
	if !ok || backend == nil {
		writeErrorJSON(w, http.StatusServiceUnavailable, "schedule_backend_unavailable", "Rust bat schedule backend is unavailable")
		return
	}
	params, err := scheduleListParams(r)
	if err != nil {
		writeErrorJSON(w, http.StatusBadRequest, "invalid_schedule_query", err.Error())
		return
	}
	result, err := backend.ScheduleList(r.Context(), params)
	if err != nil {
		s.writeControlBackendError(w, "schedule-list", err)
		return
	}
	if r.Method == http.MethodHead {
		w.Header().Set("Cache-Control", "no-store")
		w.WriteHeader(http.StatusOK)
		return
	}
	writeNoStoreJSON(w, http.StatusOK, result)
}

func scheduleListParams(r *http.Request) (backendrpc.ScheduleListParams, error) {
	query := r.URL.Query()
	params := backendrpc.ScheduleListParams{
		ID:    query.Get("id"),
		Group: query.Get("group"),
	}
	if raw := query.Get("enabled"); raw != "" {
		enabled, err := strconv.ParseBool(raw)
		if err != nil {
			return backendrpc.ScheduleListParams{}, errors.New("enabled must be a boolean")
		}
		params.Enabled = &enabled
	}
	return params, nil
}

func (s *Server) handleAdminScheduleControl(w http.ResponseWriter, r *http.Request, action string) {
	backend, ok := s.backend.(ScheduleBackend)
	if !ok || backend == nil {
		writeErrorJSON(w, http.StatusServiceUnavailable, "schedule_backend_unavailable", "Rust bat schedule backend is unavailable")
		return
	}

	var (
		method string
		result json.RawMessage
		err    error
	)
	switch action {
	case "schedule-add", "schedule-update", "schedule-remove":
		var params backendrpc.ScheduleMutationParams
		if !decodeAdminScheduleJSON(w, r, &params) {
			return
		}
		switch action {
		case "schedule-add":
			method = "schedule.add"
			result, err = backend.ScheduleAdd(r.Context(), params)
		case "schedule-update":
			method = "schedule.update"
			result, err = backend.ScheduleUpdate(r.Context(), params)
		default:
			method = "schedule.remove"
			result, err = backend.ScheduleRemove(r.Context(), params)
		}
	case "schedule-run":
		var params backendrpc.ScheduleRunParams
		if !decodeAdminScheduleJSON(w, r, &params) {
			return
		}
		method = "schedule.run"
		result, err = backend.ScheduleRun(r.Context(), params)
	default:
		writeErrorJSON(w, http.StatusNotFound, "control_not_found", "unknown control action")
		return
	}
	if err != nil {
		s.writeControlBackendError(w, action, err)
		return
	}
	writeNoStoreJSON(w, http.StatusAccepted, AdminControlResponse{
		Service:   "bat-api",
		Action:    action,
		RPCMethod: method,
		Status:    "accepted",
		Result:    result,
	})
}

func (s *Server) requireAdminToken(w http.ResponseWriter, r *http.Request) bool {
	if s.cfg.AuthToken == "" {
		writeErrorJSON(w, http.StatusForbidden, "admin_auth_required", "admin controls require BAT_API_AUTH_TOKEN")
		return false
	}
	if !constantTimeTokenEqual(s.requestToken(r), s.cfg.AuthToken) {
		w.Header().Set("WWW-Authenticate", `Bearer realm="bat-api-admin"`)
		writeErrorJSON(w, http.StatusUnauthorized, "unauthorized", "missing or invalid access token")
		return false
	}
	return true
}

func decodeAdminScheduleJSON(w http.ResponseWriter, r *http.Request, target any) bool {
	return decodeAdminJSON(w, r, target, "invalid_schedule_params", "schedule request")
}

func decodeAdminTranslationJSON(w http.ResponseWriter, r *http.Request, target any) bool {
	return decodeAdminJSON(w, r, target, "invalid_translation_params", "translation task request")
}

func decodeAdminJSON(w http.ResponseWriter, r *http.Request, target any, errorCode string, subject string) bool {
	if r.Body == nil {
		return true
	}
	decoder := json.NewDecoder(http.MaxBytesReader(w, r.Body, adminScheduleMaxBodyBytes))
	decoder.DisallowUnknownFields()
	if err := decoder.Decode(target); err != nil {
		if errors.Is(err, io.EOF) {
			return true
		}
		writeErrorJSON(w, http.StatusBadRequest, errorCode, subject+" must be a JSON object")
		return false
	}
	if err := decoder.Decode(&struct{}{}); !errors.Is(err, io.EOF) {
		writeErrorJSON(w, http.StatusBadRequest, errorCode, subject+" must contain exactly one JSON object")
		return false
	}
	return true
}

func decodeAdminControlRequest(w http.ResponseWriter, r *http.Request) (adminControlRequest, bool) {
	var request adminControlRequest
	if r.Body == nil {
		return request, true
	}
	decoder := json.NewDecoder(http.MaxBytesReader(w, r.Body, adminControlMaxBodyBytes))
	decoder.DisallowUnknownFields()
	if err := decoder.Decode(&request); err != nil {
		if errors.Is(err, io.EOF) {
			return request, true
		}
		writeErrorJSON(w, http.StatusBadRequest, "invalid_control_params", "control request must be a JSON object with an optional force boolean")
		return adminControlRequest{}, false
	}
	if err := decoder.Decode(&struct{}{}); !errors.Is(err, io.EOF) {
		writeErrorJSON(w, http.StatusBadRequest, "invalid_control_params", "control request must contain exactly one JSON object")
		return adminControlRequest{}, false
	}
	return request, true
}

func (s *Server) writeControlBackendError(w http.ResponseWriter, action string, err error) {
	status := http.StatusBadGateway
	code := "control_backend_failed"
	message := "Rust bat rejected the control request"
	switch {
	case errors.Is(err, context.DeadlineExceeded):
		status = http.StatusGatewayTimeout
		code = "control_backend_timeout"
		message = "Rust bat control request timed out"
	case errors.Is(err, context.Canceled):
		status = http.StatusRequestTimeout
		code = "control_request_canceled"
		message = "control request was canceled"
	default:
		var apiErr *backendrpc.APIError
		if errors.As(err, &apiErr) && apiErr.Kind == "not_implemented" {
			status = http.StatusNotImplemented
			code = "control_not_implemented"
			message = "Rust bat does not implement this control action"
		}
	}
	s.logger.Printf("bat-api control action=%s error=%v", action, err)
	writeErrorJSON(w, status, code, message)
}