package internalhttp

import (
	"context"
	"encoding/json"
	"errors"
	"net/http"
	"time"

	"galaxy/mail/internal/service/getdelivery"
	"galaxy/mail/internal/service/listattempts"
	"galaxy/mail/internal/service/listdeliveries"
	"galaxy/mail/internal/service/resenddelivery"
)

const defaultOperatorRequestTimeout = 5 * time.Second

// ListDeliveriesUseCase lists accepted deliveries for trusted operators.
type ListDeliveriesUseCase interface {
	// Execute returns one filtered deterministic ordered page of deliveries.
	Execute(context.Context, listdeliveries.Input) (listdeliveries.Result, error)
}

// GetDeliveryUseCase resolves one accepted delivery for trusted operators.
type GetDeliveryUseCase interface {
	// Execute returns one exact delivery view and its optional dead-letter
	// entry.
	Execute(context.Context, getdelivery.Input) (getdelivery.Result, error)
}

// ListAttemptsUseCase resolves one delivery-attempt history for trusted
// operators.
type ListAttemptsUseCase interface {
	// Execute returns the full attempt history of one accepted delivery.
	Execute(context.Context, listattempts.Input) (listattempts.Result, error)
}

// ResendDeliveryUseCase clones one accepted terminal delivery for trusted
// operator resend.
type ResendDeliveryUseCase interface {
	// Execute creates one new clone delivery and returns its identifier.
	Execute(context.Context, resenddelivery.Input) (resenddelivery.Result, error)
}

func newListDeliveriesHandler(useCase ListDeliveriesUseCase, timeout time.Duration) http.HandlerFunc {
	return func(writer http.ResponseWriter, request *http.Request) {
		input, err := DecodeDeliveryListInput(request)
		if err != nil {
			writeErrorResponse(writer, http.StatusBadRequest, ErrorCodeInvalidRequest, err.Error())
			return
		}

		callCtx, cancel := context.WithTimeout(request.Context(), effectiveOperatorTimeout(timeout))
		defer cancel()

		result, err := useCase.Execute(callCtx, input)
		if err != nil {
			switch {
			case errors.Is(err, listdeliveries.ErrInvalidCursor):
				writeErrorResponse(writer, http.StatusBadRequest, ErrorCodeInvalidRequest, "cursor is invalid")
			case errors.Is(err, listdeliveries.ErrServiceUnavailable):
				writeErrorResponse(writer, http.StatusServiceUnavailable, ErrorCodeServiceUnavailable, "service is unavailable")
			default:
				writeErrorResponse(writer, http.StatusInternalServerError, ErrorCodeInternalError, "internal server error")
			}
			return
		}

		response := DeliveryListResponse{
			Items: make([]DeliverySummaryResponse, len(result.Items)),
		}
		for index, record := range result.Items {
			response.Items[index] = summaryResponseFromDelivery(record)
		}
		if result.NextCursor != nil {
			encodedCursor, err := EncodeDeliveryListCursor(*result.NextCursor)
			if err != nil {
				writeErrorResponse(writer, http.StatusInternalServerError, ErrorCodeInternalError, "internal server error")
				return
			}
			response.NextCursor = encodedCursor
		}

		writeJSONResponse(writer, http.StatusOK, response)
	}
}

func newGetDeliveryHandler(useCase GetDeliveryUseCase, timeout time.Duration) http.HandlerFunc {
	return func(writer http.ResponseWriter, request *http.Request) {
		deliveryID, err := DecodeDeliveryIDFromPath(request)
		if err != nil {
			writeErrorResponse(writer, http.StatusBadRequest, ErrorCodeInvalidRequest, err.Error())
			return
		}

		callCtx, cancel := context.WithTimeout(request.Context(), effectiveOperatorTimeout(timeout))
		defer cancel()

		result, err := useCase.Execute(callCtx, getdelivery.Input{DeliveryID: deliveryID})
		if err != nil {
			switch {
			case errors.Is(err, getdelivery.ErrNotFound):
				writeErrorResponse(writer, http.StatusNotFound, ErrorCodeDeliveryNotFound, "delivery not found")
			case errors.Is(err, getdelivery.ErrServiceUnavailable):
				writeErrorResponse(writer, http.StatusServiceUnavailable, ErrorCodeServiceUnavailable, "service is unavailable")
			default:
				writeErrorResponse(writer, http.StatusInternalServerError, ErrorCodeInternalError, "internal server error")
			}
			return
		}

		writeJSONResponse(writer, http.StatusOK, detailResponseFromDelivery(result.Delivery, result.DeadLetter))
	}
}

func newListAttemptsHandler(useCase ListAttemptsUseCase, timeout time.Duration) http.HandlerFunc {
	return func(writer http.ResponseWriter, request *http.Request) {
		deliveryID, err := DecodeDeliveryIDFromPath(request)
		if err != nil {
			writeErrorResponse(writer, http.StatusBadRequest, ErrorCodeInvalidRequest, err.Error())
			return
		}

		callCtx, cancel := context.WithTimeout(request.Context(), effectiveOperatorTimeout(timeout))
		defer cancel()

		result, err := useCase.Execute(callCtx, listattempts.Input{DeliveryID: deliveryID})
		if err != nil {
			switch {
			case errors.Is(err, listattempts.ErrNotFound):
				writeErrorResponse(writer, http.StatusNotFound, ErrorCodeDeliveryNotFound, "delivery not found")
			case errors.Is(err, listattempts.ErrServiceUnavailable):
				writeErrorResponse(writer, http.StatusServiceUnavailable, ErrorCodeServiceUnavailable, "service is unavailable")
			default:
				writeErrorResponse(writer, http.StatusInternalServerError, ErrorCodeInternalError, "internal server error")
			}
			return
		}

		response := DeliveryAttemptsResponse{
			Items: make([]AttemptResponse, len(result.Attempts)),
		}
		for index, record := range result.Attempts {
			response.Items[index] = attemptResponseFromRecord(record)
		}

		writeJSONResponse(writer, http.StatusOK, response)
	}
}

func newResendDeliveryHandler(useCase ResendDeliveryUseCase, timeout time.Duration) http.HandlerFunc {
	return func(writer http.ResponseWriter, request *http.Request) {
		deliveryID, err := DecodeDeliveryIDFromPath(request)
		if err != nil {
			writeErrorResponse(writer, http.StatusBadRequest, ErrorCodeInvalidRequest, err.Error())
			return
		}

		callCtx, cancel := context.WithTimeout(request.Context(), effectiveOperatorTimeout(timeout))
		defer cancel()

		result, err := useCase.Execute(callCtx, resenddelivery.Input{DeliveryID: deliveryID})
		if err != nil {
			switch {
			case errors.Is(err, resenddelivery.ErrNotFound):
				writeErrorResponse(writer, http.StatusNotFound, ErrorCodeDeliveryNotFound, "delivery not found")
			case errors.Is(err, resenddelivery.ErrNotAllowed):
				writeErrorResponse(writer, http.StatusConflict, ErrorCodeResendNotAllowed, "delivery status does not allow resend")
			case errors.Is(err, resenddelivery.ErrServiceUnavailable):
				writeErrorResponse(writer, http.StatusServiceUnavailable, ErrorCodeServiceUnavailable, "service is unavailable")
			default:
				writeErrorResponse(writer, http.StatusInternalServerError, ErrorCodeInternalError, "internal server error")
			}
			return
		}

		writeJSONResponse(writer, http.StatusOK, DeliveryResendResponse{
			DeliveryID: result.DeliveryID.String(),
		})
	}
}

func effectiveOperatorTimeout(timeout time.Duration) time.Duration {
	if timeout <= 0 {
		return defaultOperatorRequestTimeout
	}

	return timeout
}

func writeJSONResponse(writer http.ResponseWriter, statusCode int, payload any) {
	writer.Header().Set("Content-Type", "application/json")
	writer.WriteHeader(statusCode)
	_ = json.NewEncoder(writer).Encode(payload)
}