eia-api-go/cmd/eia-client/internal/util/util_reflect.go

package util

import (
	"context"
	"errors"
	"fmt"
	"net/http"
	"reflect"
	"strconv"
	"time"

	"github.com/spf13/cobra"

	eiaapi "gitea.libretechconsulting.com/50W/eia-api-go/api"
)

func GetFacets(cmd *cobra.Command, route string) (*eiaapi.FacetOptionList, error) {
	client, err := Client(cmd)
	if err != nil {
		return nil, err
	}

	// Get the reflect.Value of the target object
	targetValue := reflect.ValueOf(client)

	// Get the method by name
	method := targetValue.MethodByName(route)
	if !method.IsValid() {
		return nil, fmt.Errorf("method %q not found", route)
	}

	// Create a slice of reflect.Value for the method's arguments
	methodType := method.Type()
	args := make([]reflect.Value, 0, methodType.NumIn())

	// Populate arguments with zero values for their respective types
	for i := 0; i < methodType.NumIn(); i++ {
		argType := methodType.In(i)

		// Don't supply request editor Fn args
		if methodType.IsVariadic() && i == methodType.NumIn()-1 {
			continue
		}

		if argType == reflect.TypeOf((*context.Context)(nil)).Elem() {
			args = append(args, reflect.ValueOf(cmd.Context()))
			continue
		}

		// Default to last year for Route1
		if argType == reflect.TypeOf(eiaapi.Route1("1999")) {
			lastYear := time.Now().AddDate(-1, 0, 0).Year()
			args = append(args, reflect.ValueOf(eiaapi.Route1(strconv.Itoa(lastYear))))
			continue
		}

		// Zero value of other stuff
		args = append(args, reflect.Zero(argType))
	}

	results := method.Call(args)
	if len(results) != 2 {
		return nil, errors.New("unexpected response from get facet call")
	}

	var resp *http.Response
	var ok bool
	if resp, ok = results[0].Interface().(*http.Response); !ok {
		return nil, errors.New("no or invalid response received from call")
	}
	if err := checkCallErr(results[1]); err != nil {
		return nil, err
	}

	parserFunc, exists := eiaapi.ParseFunctionsMap[fmt.Sprintf("Parse%sResponse", route)]
	if !exists {
		return nil, fmt.Errorf("parser func for %s not found", route)
	}

	parser := reflect.ValueOf(parserFunc)
	if !parser.IsValid() {
		return nil, errors.New("unable to find parser for facet response")
	}

	results = parser.Call([]reflect.Value{reflect.ValueOf(resp)})
	if len(results) != 2 {
		return nil, errors.New("unexpected response while parsing facet response")
	}
	if err := checkCallErr(results[1]); err != nil {
		return nil, err
	}

	result := results[0]
	if result.Kind() == reflect.Ptr {
		result = result.Elem()
	}

	if result.Kind() != reflect.Struct {
		return nil, fmt.Errorf("unexpected parse result kind %s", result.Kind().String())
	}

	field := result.FieldByName("JSON200")
	if !field.IsValid() {
		return nil, errors.New("invalid facet data field in response")
	}

	facetOptions, ok := field.Interface().(*eiaapi.FacetOptionListContainer)
	if !ok {
		return nil, errors.New("response does not contain facet options")
	}

	if facetOptions == nil {
		return nil, errors.New("no facet options found for facet request")
	}

	return facetOptions.Response, nil
}

func checkCallErr(val reflect.Value) error {
	var err error
	var ok bool

	if val.IsValid() && !val.IsNil() {
		if err, ok = val.Interface().(error); !ok {
			return errors.New("unexpected call response")
		}
	}

	return err
}