eia-api-go/pkg/eia/eia_reflection.go

package eia

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

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

// For reflected API requests, dynamically replace certain
// parameters by type
type MethodSubs struct {
	TypedParams      map[reflect.Type]reflect.Value // Replace field of specific type with value, must be ptr to type
	RequestEditorFns []eiaapi.RequestEditorFn       // Optional request editor functions
}

// By default replace all routes with a string year
// To be more specific, set NameParams, which will overwrite
// NameContainsParams
var defaultMethodSubs = MethodSubs{
	TypedParams: map[reflect.Type]reflect.Value{
		reflect.TypeOf((*eiaapi.Route1)(nil)): reflect.ValueOf(
			strconv.Itoa(time.Now().AddDate(-1, 0, 0).Year())),
	},
}

// Given an API route and a facet ID, retrieve information about the facet
func (client *Client) GetFacet(ctx context.Context, route string, facet string, subs *MethodSubs) (*eiaapi.FacetDetails, error) {
	eiaClient := reflect.ValueOf(client)

	// Get the method for describing this facet
	methodName := fmt.Sprintf("%sFacetId", route)
	method := eiaClient.MethodByName(methodName)
	if !method.IsValid() {
		return nil, fmt.Errorf("method %s not found", methodName)
	}

	// Populate facet param anywhere in func call
	subs.TypedParams[reflect.TypeOf((*eiaapi.FacetId)(nil))] = reflect.ValueOf(facet)

	args := prepMethodArgs(method, methodName, subs)

	// Prepare a parser func for our facet response
	parserFunc, exists := eiaapi.ParseFunctionsMap[fmt.Sprintf("Parse%sResponse", methodName)]
	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 := method.Call(args)
	resp, err := getResponse(results)
	if err != nil {
		return nil, err
	}

	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")
	}

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

	if facetDetails == nil {
		return nil, errors.New("no facet details found for facet")
	}

	return facetDetails.Response, nil
}

// Return a list of facets given a named route
func (client *Client) GetFacets(ctx context.Context, route string, subs *MethodSubs) (*eiaapi.FacetOptionList, error) {
	eiaClient := reflect.ValueOf(client)

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

	args := prepMethodArgs(method, route, subs)

	// Prepare a parser func for our facet response
	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")
	}

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

	// Prepare *http.Response, error
	resp, err := getResponse(results)
	if err != nil {
		return nil, err
	}

	// Call the parser with our response, then extract the JSON200 response,
	// and return the expected FacetOptiionsList from the container

	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
}

// Prepare default substitutions with a provided context
func DefaultMethodSubs(ctx context.Context) *MethodSubs {
	subs := defaultMethodSubs

	subs.TypedParams[reflect.TypeOf((*context.Context)(nil)).Elem()] = reflect.ValueOf(ctx)

	return &subs
}

// Return a list of API routes with a given list of
// function suffixes
func GetRoutes(suffixes ...string) []string {
	eiaClientInterface := new(eiaapi.ClientInterface)
	t := reflect.TypeOf(eiaClientInterface).Elem()

	routes := make([]string, 0, t.NumMethod())

	for i := 0; i < t.NumMethod(); i++ {
		method := t.Method(i)
		if len(suffixes) < 1 {
			routes = append(routes, method.Name)
			continue
		}

		for _, suffix := range suffixes {
			if strings.HasSuffix(method.Name, suffix) {
				routes = append(routes, method.Name)
				break
			}
		}
	}

	return slices.Clip(routes)
}

// Given an API method, replaces any named fields with the provided value
// from the subs map, otherwise uses built-in logic for common fields
// such as a context.Context. Skips request editor funcs
func prepMethodArgs(method reflect.Value, name string, subs *MethodSubs) []reflect.Value {
	// 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)

		// Supply provided request editor Fn args if this function
		// is varidic and if we're in the lest arg
		if methodType.IsVariadic() && i == methodType.NumIn()-1 {
			for _, reFn := range subs.RequestEditorFns {
				args = append(args, reflect.ValueOf(reFn))
			}
			break
		}

		// Retrieve arg from generated arg mapping due to use of
		// type aliases (e.g. type Route1 = string) rather than use of
		// discrete types (e.g. type Route1 string) in generated code
		funcArgs, ok := eiaapi.FunctionParams[name]
		if ok {
			if i > len(funcArgs) {
				// WARN: This indicates a generator issues
			} else {
				argType = funcArgs[i]
			}
		} else {
			// WARN: This indicates a generator issues
		}

		// Run through type substitutions
		for t, v := range subs.TypedParams {
			if argType.Kind() == reflect.Ptr && argType.Elem() == t {
				args = append(args, v)
				goto next
			}
		}

		// Fall back to less-specific types
		for t, v := range subs.TypedParams {
			if argType == t {
				args = append(args, v)
				goto next
			}
		}

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

	return args
}

func getResponse(responses []reflect.Value) (*http.Response, error) {
	resp, ok := responses[0].Interface().(*http.Response)
	if !ok {
		return nil, errors.New("no or invalid response received from call")
	}

	if err := checkCallErr(responses[1]); err != nil {
		return nil, err
	}

	return resp, 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
}